IEEE Wireless Dictionary (IEEE Standards Wireless Networks)

Dictionary Dr. James P. K. Gilb

Published by Standards Information Network

IEEE Press

ThelEEE Wireless Dictionary By Dr. James P. K. Gilb

"IEEE Published by Standards Information Network IEEE Press

Trademarks and Disclaimers IEEE believes the information ill this publication is accurate as of its publication date; such information is slIbject to change without notice. IEEE is not responsible for any inadvertellt errors. Library of Congress Cataloging-in-Publication Data

Gilb. James P.K., 1965The IEEE wireless dictionary I by James P.K. Gilb.

p. cm. -- (IEEE standards wireless networks series) ISBN 0-7381-4766-4 1. Wireless communication systems--Dictionaries. I. Title. IT. Series.

TK5 103.2.G54 2005 621.38403--dc22

2005054462

IEEE 3 Park Avenue, New York. NY 10016-5997. USA Copyright © 2005 by The Institute o{ EleCTrical and Electronics Engineers.

Inc. Al! rights reserved. Published December 2005. Printed in the United States of America. No part o(this publicationlllav be reproduced in anyforlll. ill all electronic retrieval system. or othenvise. without the prior written permission of the publishel:

I

Jennifer AIcClaill Longmon. Managing Editor Linda Sibilia. Cover Designer

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TRADEMARKS Bluetooth is a registered trademark of Bluetooth SIG, Inc. (www.bluelooth.orgf). CDMA2000 is a registered trademark of the Telecommunications Industry Association (TIA USA) (www.tiaonline.org/). IEEE and 802 are registered trademarks of the IEEE (www.icee.org/). IEEE Standards designations are trademarks of the IEEE (www.ieee.org/). Iridium is a trademark of Iridium, Inc. (www.iridium.com/). Qualcomm is a registered trademark of Qualcomm (www.qualcomm.com/). RC4 is a trademark of RSA Security (http://www.rsasccurity.com/). Wi-Fi is a registered trademark of the Wi-Fi Alliance (www.wi-fi.org/). WiMedia is a trademark of the WiMedia Alliance (www.wimedia.org/). WiMAX is a trademark of the WiMAX Forum (www.wimaxforum.orgf). Zig Bee Alliance is a trademark of Philips Corporation (www.zigbee.org/).

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AUTHOR James P. K. Gilb received the Bachelor of Science degree in Electrical Engineering in 1987 from the Arizona State University, graduating magna cum laude. In 1989, he received the Master of Science degree in Electrical Engineering from the same institution and was named the Outstanding Graduate of the Graduate College. He received the Ph.D. degree in Electrical Engineering in 1999, also from Arizona State University. From 1993 to 1995, he worked as an Electrical Engineer at the Hexcel Corporation's Advanced Products Division, which was subsequently bought by the Northrop Grumman Corporation, developing advanced attificial electromagnetic materials, radar absorbing materials, and radar absorbing structures. He joined the Motorola Corporation in 1995, working initially for the Government Systems Technology Group as an RFIC designer and radio system designer. In J999, he moved to the Semiconductor Products Sector as a Technical Staff Engineer (Member of Technical Staff) where he worked on a variety of radio systems. He developed radio architectures and specifications for new products and provided input for new process development. He joined the Mobilian Corporation in 2000, as a Senior Staff Engineer, where he developed the radio architecture and wrote the specification for the RF/analog chip that supported simultaneous operation of IEEE Std 802.11 and Bluetooth. He was also responsible for the detailed design and layout for the front -end RF circuits of the chip. In 2002, he joined Appairent Technologies as the Director of Radio Engineering where he was responsible for overseeing the implementation of the complete physical layer for IEEE Std 802.15.3. In 2005, Dr. Gilb joined SiBEAM as a Senior Member of Technical Staff working in the area of wireless technologies and standards. He has been the Technical Editor of the IEEE 802.15.3 Task Group, the IEEE 802.l5.3b Task Group and is cun-endy the Technical Editor of the IEEE 802.15 Working Group and the IEEE 802.l5.3c Task Group. He has five patents issued, many papers published in refereed journals, and is the author of two books: Wireless Multimedia: A Guide to the IEEE 802.J5.3 Standard and IEEE Wireless Dictionary. He is aJ so presently teaching courses t1uollgh Doceotech, training engineers in wireless standat·ds.

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IEEE Wireless Dictionary

OVERVIEW

How to use this book Wireless technology, like many other technical fields, has its own set of jargon and acronyms. Many times, these acronyms are used simply to reduce the effort required to describe concepts. Imagine having to say "time division synchronous code division multiple access" every time instead of just "TD-SCDMA." The goal of this book is to provide meaning for the acronyms and jargon used in the wireless industry with a particular emphasis on commercial systems. Although not exhaustive, the goal was to include the most commonly used terms. Individuals who are expelts in one pmticular field, e.g., third generation (3G) cellular or Wireless Local Area Networks (WLANs), will find tenns from other fields with which they are unfmniliar. Individuals who need to have broad view of the wireless landscape will find that this book covers most of the topics and terms that are important in today's market. This book is a dictionary that reads more like an encyclopedia. Rather than just giving a terse definition for various wireless terms, many of the definitions contain additional information to provide context for understanding the tenn. A little history is added where appropriate, as well as some opinion regarding the technical and marketing issues that make the design of wireless systems so interesting.

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IEEE Wireless Dictionary

The book is organized into four sections. The first (this one) contains an overview of the book and addresses a couple of topics that are common to many of the definitions, e.g., frequency bands, and the Open Systems Interconnection (OST) networking model. The second part of the book contains the definitions arranged, strangely enough, in alphabetical order. The third section has a handy list of acronyms and abbreviations for quick reference. The fourth section has a bibliography for quick reference.

FREQUENCY BANDS

The frequency spectrum is commonly divided into the bands shown in Figure 1. The band names serve only as a reference and are not a requirement for a system. Some systems will have frequency allocations that exist in more than one of the bands shown in Figure 1. As shown in Figure I, the labels for the frequency bands were chosen to give nice round numbers for the wavelengths. The bands are occasionally referred to by the wavelength. For example, the 30 GHz to 300 GHz band is often referred to as the millimeter wave band because the wavelengths for these frequencies are between I and 10 mm. The 3 GHz to 30 GHz band is usually referred to as the microwave band, despite the fact that the wavelength is in centimeters as opposed to microns, and typical microwave ovens operate just below this band in the 2.4-2.4835 GHz Industrial, Scientific, and Medical (ISM) band.

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IEEE Wireless Dictionary

Frequency

Wavelength

Selected 'FCC allocations

10000 m

30Hz

ELF 1000 km

300 Hz

VF

3kHz

VLF 30kHz

LF 300 kHz

:::~m

~

AM Radio 535-1065 kHz

CB radio, toys, etc. 27 MHz

1 km

Cordless phones, toys, etc. 43.69-50 MHz

MF 3MHz

100 m HF

30MHz

VHF TV 54-72,76-88 MHz FM Radio 88-108 MHz VHF TV 174-216 MHz UHF TV 470-608,614-806 MHz

VHF

Cellular phones 824-849, 869-894 MHz

300 MHz

ISM band, 902-928 MHz

I UHF ~:..~~======= pes (digital cellular) 3GHz

L

SHF 30GHz

;:~~~~::9G~~3-2.15

ISM band, 2.4-2.4635 GHz

UN!! bands, 5.15-5.35, 5.47-5.825 GHz 10m

ISM band 5.725-5.875 GHz

EHF 300 GHz

Figure 1:

1mm

Unlicensed operation 57-64 GHz

Naming convention for frequency bands

Throughout this dictionary, a shorthand notation will be used to refer to the various frequency bands in use in wireless communications, The mobile phone bands also have a shorthand notation to refer to the allocations that are available. Some of these are listed in Table 1.

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IEEE Wireless Dictionary

Table 1:

Common names for various frequency bands

Frequency (MHz)

Regionsl regulatory

Common name(s)

824-849,869-894

FCC

800 or 850 band

1850-1990

FCC

PCS, 1900 band

880-915,925-960

ETSI

GSM900, 900 band

1710-1785, 1805-1880

ETSI

DCS1800, 1800 band

1750-1780

South Korea

Korea PCS band

810-888,893-958

Japan

800 MHz band

1429-1453, 1477-\501,

Japan

1.5 GHz band

2400-2483.5

Various

2.4 Gllz band, ISlvl band

OSI 7-LAYER PROTOCOL MODEL The OSI standard, ISO 7498, was developed by International Organization for Standardization (ISO) as an attempt to define a communications protocol stack (i.e., a layered group of protocols) that provides well-defined interfaces between different parts of communications protocol. A fier much deliberation, the ISO committee settled on a 7-1ayer modell, as illustrated in Figure 2.

1

4

This is sometimes referred to as the Taco Bell"' model because the restaurant chain has sold a 7-layer burrito.

IEEE Wireless Dictionary

IEEE Wireless Dictional:)'

Layer 7: Application Layer 6: Presentation Layer 5: Session Layer4: Transport Layer 3: Network Layer 2: Data link Layer 1: Physical Figure 2:

OSl7-layer protocol model

Not everyone agrees with the model, but most protocols attempt to find some place in the 7-layer model. While some people feel that seven layers is too many (the U.S. Depaltment of Defense model only has four), it is not uncommon for standards to define sublayers within one or more of the seven layers. In particular, the IEEE 802® Local Area Network/Metropolitan Area Network (LAN/MAN) Standards Committee (LMSC) has divided Layer 2 into two sub layers, the Medium Access Controller (MAC) and the Logical Link Controller (LLC).

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IEEE Wireless Dictionary

While not every communications protocol stack adheres to this model, the layers are used as a shorthand to indicate the location in the network stack where specific operations are accomplished. For example, network switches are often referred to as Layer 3 or Layer 4 switches 2 • This indicates that determination of where to send the data is being made in a different portion of the networking stack. Likewise, wireless networks are generally concerned with only Layer 1 and Layer 2 as the higher layers are relatively independent of type of physical layer (PHY), wired or wireless, that is being used. As with all things that relate to computers, jokes abound. Something is a "Layer 8 problem" when the issue is with the user and not the network. Another joke is that the model really needs 9 layers, where Layer 8 is money and Layer 9 is political. People will also complain of "layer bleeding" when one layer's functions are being performed by another layer.

2

6

Switches normally reside in Layer 2. The marketing terms "Layer 3 switch" and "Layer 4 switch" are used to indicate that a similar switching function is being accomplished at a higher layer.

IEEE Wireless Dictionary

IEEE Wireless Dictional:v

DEFINITIONS IX: See: CDMA2000@ IX.

lx evolution-data optimized (lxEV-DO): See: CDMA2000® lxEV-DO.

8 differential phase shift keying (8DPSK): A modulation method in which groups of three bits that are to be transmitted are mapped onto one of eight equally-spaced phase changes. A typical 8DPSK (or 8PSK for that matter) constellation is illustrated in Figure 3. As with other differential modulation techniques, 8DPSK maps the groups of bits to a phase change rather than an absolute phase. See also: 8 phase shift keying (8PSK), differential quadrature phase shift keying (DQPSK), nl4 differential quadrature phase shift keying (DQPSK), and phase modulation (PM) .

Figure 3:

•

•

•

•

Example of constellation for 8DPSK modulation

lEE!: Wireless Dictionmy

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IEEE Wireless Dictionary

8 phase shift keying (8PSK): A modulation method in which groups of three bits that are to be transmitted are mapped onto one of eight equally-spaced absolute phases, e.g., 0°,45°,90°, 135°, 180°,225°,270°, and 315°. A typical8PSK (or 8DPSK for that matter) constellation is illustrated in Figure 3. Unlike differential modulation techniques, 8PSK maps the groups of bits to an absolute phase rather than a phase change. See also: 8 differential phase shift keying (8DPSK), differential quadrature phase shift keying (DQPSK), and 1t/4 differential quadrature phase shift keying (DQPSK). access point (AP): A device in an IEEE 802.11 WLAN operating in infrastructure mode that provides a variety of services for the network, including access to external wired networks. The access point (AP) acts as the master ofthe WLAN, and stations (STAs) need to receive permission from the AP to join the WLAN. If security is implemented, the STA will also need to authenticate with or through the AP before it can join the network. 3 In infrastructure mode, all data traffic goes through the AP rather than directly between STAs in the network. 4 Typical wireless products that implement the IEEE 802.11 AP functionality also provide Dynamic Host Configuration Protocol (DHCP) and network address translation (NAT) services, which are not part of the IEEE 802.11 AP. However, the entire product will often be labeled as a "Wireless Access Point" even though it is much more than just an AP. See also:

1

4

8

In some cases, the AP passes the authentication information to a security server, e.g., a RADIUS server. Direct links between STAs are an optional feature of the IEEE 802.11 e amendment to IEEE Std 802.11.

IEEE Wireless DictionalY

IEEE Wireless Dictionary

Extensible Authentication Protocol (EAP) and Remote Authentication Dial-in User Service (RADIUS). ad-hoc mode: In IEEE 802.11, a WLAN in which all of the STAs are peers and there is not an AP.5 This mode is not used by most users because it requires them to manually configure the network. On the other hand, in infrastructure mode for IEEE 802.11, a typical AP will be integrated with higher layer functions in a single product that will act as a DHCP server allowing the STAs to automatically configure their networking. 6 ad-hoc network: A network that forms automatically for only as long as it is required to exchange data. Wireless personal area networks (WPANs) are typically ad-hoc networks. address resolution protocol (ARP): A part of transmit control protocol/internet protocol (TCP/IP), address resolution protocol (ARP) is a method for detennining the MAC address that corresponds to an IP address. A broadcast frame is sent to all of the hosts on the network, and either the device that has that IP address or a router that knows the MAC address of the machine that has that IP address responds with the information.

5

(,

In IEEE Std 802.11, this is referred to as an independent basic service set (IBSS). Strictly speaking. the DHCP functionality is not part of an AP. However, to the typical user, the DHCP, NAT, firewall, etc., are all part afthe "access point" because that is what the manufacturers call these boxes.

IEEE Wireless Dictiona1Y

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Wireless Dictionarv

adjacent channel interference protection ratio (ACIPR): A measure of how well a receiver resists adjacent channel interference. It is the ratio of the power of an interfering signal to the power of the desired signal, usually expressed in dB. Typical receivers can withstand interferers that are stronger than the desired signal, so the adjacent channel interference protection radio is usually a positive dB value. adjacent channel power ratio (ACPR): A measure ofthe quality of the transmitted signal. It is the ratio of the power in an adjacent channel to the power in the desired channel and is generally expressed in dB. As with all frequency domain power measurements, the ACPR should have the resolution bandwidth specified for both the adjacent and desired channels. The ACPR requirements are important because they indicate the level of interference that is generated by a transm itter in other channels. ACPR is usually caused by non-linearities in the transmit chain and so it is generally dominated by the output third-order intercept (OIP 3). See also: third-order output intercept point (OIP3)' advanced mobile phone service (AMPSf: One of the original mobile phone standards, it is still in use in many locations today although it is being phased out in favor of2G and 3G cellular systems. AMPS is a full-duplex system that uses frequency modulation (FM) over the air in the 800 MHz band with 25 kHz wide channels. See also: first generation (1 G), narrowband advanced mobile phone service

7

10

AMPS is sometimes expanded as Analog Mobile Phone Service.

IEEE Wireless Dictionary

IEtJi Wireless Dictiol1w:v

(NAMPS), Nordic mobile telephone (NMT), and total access communication system (TACS). advanced encryption standard (AES): A symmetric encryption algorithm that uses 128 bit blocks and is based on the Rijndael cipher. AES uses either 128, 192 or 256-bit keys. AES replaced the data encryption standard (DES) as the standard encryption algorithm for the U.S. government. AES is used in wireless standards, include IEEE Std 802.11 i, IEEE Std 802.15.3 and IEEE Std 802.15.4. See also: RC4. American National Standards Institute (ANSI): An internationally-recognized standards development body. ANSI is a private, non-profit organization (SOl(c)3) that administers and coordinates the U.S. voluntary standardization. 8 amplitude modulation (AM): A form of modulation in which the information is encoded in the amplitude of the signal. AM usually refers only to analog modulation of the signal although the term encompasses digital modulation as well. See also: amplitude shift keying (ASK) and on-off keying (OOK). amplitude shift keying (ASK): A digital modulation system in which each of n bits to be transmitted is sequentially mapped to one of 2n ampl itudes for the signal as shown in Figure 4. See also: amplitude modulation (AM) and on-off keying (OOK).

8

http://www.ansi.org/.

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IEEE Wireless Dictionmy

Figure 4:

Example of a constellation for ASK modulation with 8 levels

analog to digital converter (ADC): A device that takes an analog signal as an input and produces, at regular intervals, a measure of the signal amplitude as a binary number.

antenna diversity: A receiver technique for improving the received signal by non-coherently combining the signals received from two or more antennas. This may take the form of switched antenna diversity, in which a single antenna is selected based on some predetermined criterion [e.g., the bit error rate (BER) is acceptable]; selection diversity, in which the signals received from all antennas are sampled, and the one with the lowest BER is selected; combination diversity, in which the signals from all antennas are combined, the signals with the highest signal-to-noise ratio (SNR) given additional weight; and other types. The theory behind receive antenna diversity is that while one antenna may be blocked or in a point of low signal energy, a nearby antenna, as little as a quarter of a wavelength away, can

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IEEE Wireless Dictionary

IEEE Wireless DictiollCllJl

have much greater received signal strength or received signal quality. Tn an antenna diversity system, the receiver will select one or more of the available antennas to use for receiving data. As the conditions change, the receiver may switch to a different antenna set to maximize the quality of the received signal. There are many different techniques for selecting the "best" antennas and the improvement in the received signal directly depends on the quality of these techniques. Antenna diversity can be achieved not only by using the physical separation of the antennas but also by using different polarizations or orientations (polarization diversity). Note that antenna diversity is different from beam forming or phased alTays in that phased alTays employ coherent combining of the signals (i.e., considering the phase of received signals in the combining process), while antenna diversity employs non-coherent combining.

Association of Radio Industries and Business (ARIB): A public service corporation in Japan that deals with telecommunications, broadcasting, and radio-related issues. The ARlB perfonns research, develops standards, and perfoDns other related tasks.

asynchronous transfer mode (ATM): A networking protocol which encodes data into small, fixed-length packets (48-byte payload, 53 bytes with overhead), instead of variable length packets, like those used in internet protocol (lP) or ethemet. ATM was supposed to unify circuit switched protocols, like plain old telephone system (POTS), with packet switched protocols, such as IP. The CUlTent trend is for circuitswitched protocols to migrate to packet-switched networks, in

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

particular lP, and so the future of ATM is unclear. See also: internet protocol (lP). authentication: In computer security, the process of verifying that a person, computer program, or computer is who they claim to be. Note that authentication is often associated with authorization and so the two are often confused as being the same thing, which they are not. For example, when accessing a secure AP to gain access to the wireless network, the AP will first attempt to verify cryptographically that the STA sending request is the one identified in the request. Then the AP will check to see if the STA is authorized to join the network. Only if the authentication and authorization checks both pass will the STA be admitted to the network. See also: authorization and confidentiality. authorization: The process of detenl1ining that the person, computer program, or computer is allowed to perform the requested action. Normally, the first step in authorization is to authenticate the requestor. Once the identity of the requestor has been verified, the next step is to determine if the action requested is allowed for that requestor. The difference between authentication and authorization can be explained with this example: a person with a valid ID attempts to enter a private club. The guard verifies that the person matches the ID and that the ID is valid (authentication) and then checks the member list to see if the person is a member (authorization). Only if the ID is valid and the person is a member will they be allowed entry into the club. See also: authorization and confidentiality. automatic repeat request (ARQ): A class of methods for error control in networking. If the intended destination detects

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IEEE Wireless Dictionary

IEEE Wireless Dicfiol1G1:v

an error in a message, it responds to the sender and asks for a retransmission of the message. When the transmitter receives the request from the receiver, it will normally retransmit the message, unless the number of retries exceeds a preset number. Alternately, if the intended desitnation does not correctly receive the message, the destination does not confirm receipt of the message. In this case, the absence of a confinnation indicates to the sender that the message was lost and the sender wi II retransmit the message, unless the number of retries exceeds a preset number.

baseband: A generic term used to describe signals, either in analog or digital format, prior to being modulated on a carrier or after having been converted down from the carrier. See also:

carrier.

beam forming: A technique for improving the coverage distance or interference rejection of a wireless network through the use of multiple antennas and transmitters. This technique is also referred to as a phased array and was deployed as early as World War II. Beam forming antennas/phased arrays adjust the relative phase and amplitude of the signal that is applied to each of the antenna elements in the array. This allows the antenna to focus the transmitted energy in a specific direction. Because the phase and amplitude are electronically controlled, these antennas can be "steered" electronically, allowing very fast response. The technique is equally applicable for steering the receiving antenna array to maximize the received signal power or minimize interfering signal power. The initial uses of this technology focused on radar applications for the military, but mainstream commercial applications have become more

IEEE Wireless Dictionary

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IEEE Wireless DictiollQlY

common in recent years. Beam forming is now used in mobile phone towers to increase capacity and has been proposed for the IEEE 802.16 and IEEE 802.11 wireless standards. Beam forming uses only a single signal in transmit and is trying to receive only a single source in receive mode. Thus, these systems are not classified as a multiple input, multiple output (MIMO) systems. 9 See also: antenna diversity and multiple input, multiple output (MIMO).

bipolar phase shift keying (BPSK): A type of modulation in which one digital bit is encoded per symbol. The values of one and zero take on a phase of either 0 or 180 degrees, as illustrated in Figure 5.

Figure 5:

Example of a constellation for BPSK modulation

bit errOl' rate/bit error ratio (BER): A measure of receiver performance for digital transmission. It is simply the number of bits that were received in error divided by the total

9

16

The marketing of advanced IEEE 802.llaand IEEE 802.llgdevices as pre-IEEE 802.lln has led some manufacturers to claim that beam forming solutions are actually Ml MO systems, much to the chagrin of manufacturers who are actually selling true MIMO systems.

IEEE Wireless Dictionary

IEEE Wireless DictioIlCll)'

number of bits that were sent. Typically, the BER is indicated in powers of 10, e.g., 10.2, 10.6 and 10.12 • Theoretically. the BER never goes higher than 0.5 for random data because random guessing would, on average, have that value. The BER required for a system depends on the application. A BER of 10-3 may be adequate for voice, while 10-6 is required for good throughput of data, particularly with long data packets. Video requires a BER of 10- 12 , after corrections and retransmissions, for good quality. Data transfer applications require essentially zero BER but usually accomplish this with error detection and correction at the higher layers.

Bluebug: A type of Bluesnarfing attack in which the attacker gains access to the basic command set of the telephone and is able to initiate outbound calls, re-direct incoming calls, send Short Message Service (SMS) messages, initiate data connections, etc. Because many of these services have fees associated with them, a Bluebug attack can cost the victim a significant amount of money. See also: bluesnai'fing. BIuesnarfing: A security vulnerability in which an unauthorized user uses Bluetooth® to gain access to data, e.g., phone numbers, contact information, calendar, etc., on a Bluetooth-enabled device. The vulnerability was first discovered in November 2003 and affects only certain Bluetooth-enabled phones. Nonnally, the attack requires that the phone is in "discoverable" mode, i.e., that other devices can easily find it. However, there are multiple tools available on the Internet that can bypass this requirement. Unless the victim is viewing the Bluetooth-enabled device precisely when the attack takes place, the attack will be undetected.

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

Bluetooth@: An industry specification for short-range communication with raw data rates of up to 3 Mb/s and throughput up to 2.1 Mb/s. Bluetooth is an frequency hopping spread spectrum (FHSS) system that uses Gaussian frequency shift keying (GFSK), nl4 differential quadrature phase shift keying (n14 DQPSK), and 8DPSK modulation. Bluetooth operates in the unlicensed 2.4 GRz band, which is available almost worldwide. The Bluetooth specification was developed by the Bluetooth Special Interest Group (SIG) to replace the wires required to connect portable devices such as mobile phones, personal digital assistants (PDAs), laptops, and headsets/microphones. The MAC and PRY layers of the Bluetooth specification up to version 1.2 have been standardized as IEEE Std 802.15.1 Th'-2005.

broadband: A communication system that has a broad, i.e., large, data bandwidth. Broadband is an imprecise term normally used to differentiate systems that provide voice quality (10's ofkb/s) with those that are fast enough to provide video services (5-20 Mb/s). carrier: A signal used to change the frequency of the message but which does not add information to the message. See also: baseband.

carrier sense, multiple access (CSMA): A contentionbased class of multiple access protocols, characterized by an assessment of channel activity, called clear channel assessment (CCA), prior to transmission and a random delay, called a backoff, followed by another CCA if the channel is found to be active. Carrier sense, mUltiple access protocols can be further characterized into one of two types-CSMA with collision

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IEEE Wireless Dictionary

IEEE Wireless Dictionary

avoidance (CSMA/CA) and CSMA with collision detection (CSMA/CD). CSMA/CD is employed in wired systems such as IEEE Std 802.3'" (Ethernet) that have a PHY which is able to detect collisions while transmitting (and then immediately stop transmission and enter a random backofi). Wireless systems wh ich, generally speaking, do not have the capability to detect collisions while transmitting, employ CSMA/CA, which attempts to avoid collisions by first performing a CCA, then transmitting a frame. In one variant, the device first sends a short request to send (RTS) frame to the desired recipient which, if it receives the RTS frame, replies with a short clear to send (CTS) frame. If the original device receives the CTS frame, it wiJI then send the message. Since this reduces, but does not eliminate, the possibility offrame collisions, acknowledgement frames (ACKs) are an important part of networks employing CSMAICA because they cannot otherwise detect collisions. CSMAICA is used in many systems, including, but not limited to IEEE Std 802.11 m, IEEE Std 802.15.3'M, and IEEE Std 802.15.4"'.

CDMA2000®: Also known as IMT-CDMA multi-carrier lO or Ix radio transmission technology (lxRTT), this is a CDMA version of the IMT-2000 standard developed by the Tntemational Telecommunications Union (lTU). The CDMA2000 standard is 3G mobile wireless technology. CDMA2000 can support mobile data communications at data rates ranging from 144 kb/s to 2 Mb/s.

[" IMT stands for International Mobile Telecommunications.

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

CDMA2000'~ lx: Often referred to as Ix or 1xRTT, this is a second and a half generation (2.5G) mobile phone standard developed by Qualcomm® and approved by the International Telecommunications Union (ITU) to expand the capabilities of the original CDMA mobile phone standard. I x provides both voice and data, at a peak data rate of 153 kb/s, using the original 1.25 MHz CDMA channel (known as cdmaOne).

CDMA200W lx evolution-data optimized (lxEV-DO"): An upgrade of cdmaOne, Ix evolution-data optimized (1 xEV-DO) is a 3G mobile phone standard that provides improved data handling capabilities. Up to 3.1 Mb/s data rate is available in the downlink, and 1.8 Mb/s in the uplink in a radio channel allocated for data only.

CDMA200081 Ix evolution-data and voice (lxEV-DV): A 3G mobile phone standard that is the follow-on to CDMA2000 lxEV-DO. Up to 3.1 Mb/s data rate is available in the downlink, and 1.8 Mb/s is available in the uplink, in a radio channel allocated for data only. Unlike lxEV-DO, Ix Evolution-Data and Voice (lxEV-DV) supports both voice and data in the radio channel.

CDMA200081 3x: Also called IMT-2000 CDMA multi catTier (MC), this version of CDMA2000 combines three 1.25 MHz channels into a single 5 MHz channel. This allows data rates of over 2 Mb/s.

cdmaOne: The original CDMA system created by Qualcomm® and standardized as IS-95. The system was designed to

II

20

Originally, DO stood for Data Only.

IEEE Wireless Dictionary

IEEE Wireless Dictionary

coexist with existing analog service, AMPS and NAMPS, by using a combination of analog channels to fonn a 1.25 MHz wide channel in which individual connections are separated by olthogonal codes (CDMA) rather than time (TDMA) or frequency (FDMA). Originally in the 850 MHz band in the U.S., it is now used in the U.S. in the PCS bands (1.9 GHz), in South Korea in the 1.8 GHz band, as well as in other countries. Communications are full-duplex like the original AMPS system, but unlike GSM which is half-duplex.

cell: A geographic area covered by a base station. Early radio systems used a single base station to cover as much area as possible. However, this resulted in only a small number of users being able to access the network at any given time. By decreasing the coverage area of each base station, i.e., by using small cells, and providing more base stations, the number of users who can simultaneously access the system is greatly increased. This was one of the key developments that allowed the phenomenal growth of mobile phones. cellular digital packet data (CDPD): A data communications protocol developed as an overlay on the analog mobile phone system in the 850 MHz band. Cellular Digital Packet Data (CDPD) searches for unused analog phone channels and establishes a digital link of up to 19.2 kb/s. This service did not see widespread adoption and has been since been replaced by 2.5G and 3G data services.

IEEE Wireless DictionaTY

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IEEE Wireless Dictiol1wy

chip: In a direct sequence spread spectrum (DSSS) system 12, one symbol of the spreading code. The duration of a chip must be less than the duration of a bit in the original signal in order for the signal spectrum to be spread. chirp modulatiou: A spread spectrum technique in which the carrier frequency is swept over a wide band during an interval. This method is rarely used in communication systems but has seen use in radar. clear channel assessment (CCA): A process by which a device detennines the state of a channel, either busy or free. CCA is used with CSMA/CA protocols. code division multiple access (CDMA): A scheme employing DSSS that enables multiple users to access the same frequency band at the same time. Each user (or logical channel) is assigned one of a number of orthogonal code sequences. These are used by the receiver to find the desired channel among the others that are transmitted. Although this term is often associated with the cdmaOne standard, it is a general technique. See also: frequency division multiple access (FDMA) and time division multiple access (TDMA). complimentary code keying (CCK): A DSSS coding that is used in IEEE S02.llb to give data rates of 5.5 and 11 Mb/s. This term is also used in IEEE Std 802.lIg for the complimentary code keying/orthogonal frequency domain multiplexing (CCK/OFDM) optional PHY. This PHY uses the CCK

12

22

Of course, the term "chip" has many other definitions. Only its use in reference to communication systems is discllssed here.

IEEE Wireless Dictiol1w:v

IEEE Wireless Dictionary

preamble of IEEE 802.l1b with OFDM signalling from IEEE 802.11 a for the data portion.

confidentiality: A characteristic of a message or a protocol that provides guarantees that only the intended recipient of the message will be able to view its contents. See also: authentication and authorization. constant bit rate (CBR): Used in reference to voice or video streams, constant bit rate (CBR) indicates that a data transfer or encoding occurs at a constant data rate. Consumer Electronics Association (CEA): An industry organization of over 2000 companies in the U.S. consumer technology industry. The Consumer Electronics Association (CEA) has a variety of activities, including standards development, market research, and technical training. CEA also produces the International Consumer Electronics Show (CES), which is one of the world's largest consumer electronics events.

customer premises equipment (CPE): Refers to the portion of the communications equipment that is installed at the customer location as opposed to equipment that is installed in a central location or, in the case of wired communications, between the central location and the customer. The use of the term customer premises equipment (CPE) implies that the device in question is one end of a communications system that connects the customer to the outside world. As such, it is used by telecommunications companies, cable providers, and wireless data providers. Although the handset in a mobile phone

IEEE

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Dictiollm:v

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IEEE Wireless Dictionary

system is the equivalent of the handset in a POTS, it is almost never referred to as CPE.

cyclic redundancy check (CRC): A routine performed on a set of data to determine if communication errors have occurred. A calculation is performed on a portion of the transmitted data, resulting in a fixed number of bits (8, 16, or 32 are common lengths) that is typically appended to the end of that portion of data when it is sent. The receiver performs the same calculation on the received data and compares its result to the one sent by the transmitter. If the two numbers match, then it is likely (but not certain) that no errors occurred. It is possible for some of the bits in the message to be changed and still have the cyclic redundancy check (CRC) calculation have the same result, i.e., the message would be in error but the CRC would indicate that it was valid.

data converters: A generic term that refers to both analog to digital converters CADCs) and digital to analog converters (DACs). Although ADCs and DACs are distinct in terms of function and design, they require similar skill sets to design and share many ,of the same figures of merit in their specification;

decibel (dB): A dimensionless measure of the relative amplitude between two quantities, equal to ten times the base 10 logarithm of their ratio for power related quantities. For voltage related quantitites, it is equal to twenty times the base 10 logarithm of their ratio. A decibel (dB) is one-tenth of a Bel, named in honor of telephone pioneer Alexander Graham Belll3. Since many parameters in communication systems can

24

IEL'E Wireless Dictionary

IEEE Wireless Dictionary

vary over many orders ofmagnitude, decibels are often a usefu 1way to manipulate them. A decibel is a relative measure, and so an absolute measure must include a comparison value. This has led to the use of dB relative to one Watt (dBW), dB relative to one milliwatt (dBm), dB relative to an isotropic radiator (dBi), dB relative to an ideal half-wave dipole (dBd), etc. See also: decibels relative to the carrier (dBc), decibels relative to full-scale (dBFS), decibels relative to an isotropic radiator (dBi), decibels relative to a milliwatt (dBm). decibels relative to the carrier (dBc): The strength of a signal, expressed in dB relative to an unmodulated carrier. For example, the values in transmitter power mask are often indicated in decibels relative to the carrier (dBc). In this case, an accurate measure also requires that the integration bandwidth is included in the specification, e.g., "-20 dBc in a 100 kHz bandwidth." decibels relative to a dipole (dBd): The gain or directivity of an antenna, expressed in dB relative to the gain of an ideal

1)

This is why the' 13' is capitalized in the unit The convention for abbreviating units is that the letter is capitalized only when it refers to a person, an hence, a proper name. The name of the unit, however, is not capitalized, and so it is watt and not Watt (since the fonner refers to a LIn it of power while the latter refers to a person). Thus it is mm, mg and ms for meter, gram and second. but mF, mH and mW, in honor of Michael Faraday, Joseph Henry. and James Watt The multipliers are sometimes capitalized as well. Generally, multipliers that are greater than one are capitalized, e.g., M for mega-, while those less than one are lower case, e.g., m for milli-. The most comlllon exception is k for kilo-.

IEEE TFireless DictionalY

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IEEE Wireless Dictionary

halfwave dipole antenna. The gain of an ideal half-wave dipole in free space is about 2.14 dBi.

decibels relative to full-scale (dBFS): The strength of a signal, expressed in dB relative to a full-scale value. This unit is usually Llsed for the specifications of data converters. decibels relative to an isotropic radiator (dBi): The most common measurement unit for antenna gain or directivity, it is the gain or directivity of the antenna relative to an ideal isotropic radiator. An ideal isotropic radiator spreads the energy evenly over a spherical surface. decibels relative to a milliwatt (dBm): The most common form of power measurement in the pOliable wireless environment because the transmitters do not usually go much higher than a few watts. One milliwatt is 0 dBm while 1 Watt is 30dBm.

decibels relative to a watt (dBW): The power ofa signal, expressed in dB relative to one Watt.

differential nonlinearity (DNL): A performance measure of data converters. In an ideal A DC, the voltage required to change the digital code by one least significant bit (LSB) is constant for all of codes. Likewise, changing the digital code by one LSB in a DAC should result in the same change in the output (either current or voltage) as for a one-LSB change for any of the other codes. However, in a real device, these values vary from the ideal step size. For example, if a change of one LSB in the code produces a 1.5 LSB change in the output, the differential linearity (DNL) is 0.5 LSB. DNL is expressed

26

11"£E Wireless Dictionary

IEEE Wireless Dictionary

either in LSBs, where I LSB is equivalent to changing the digital code by one, or as a percentage of the full-scale range. See also: integral nonlinearity (INL).

differential quadrature phase shift keying (DQPSK): A modulation method based on QPSK in which pairs ofbits to be transmitted are encoded as a change in the phase of the signal. DQPSK allows both coherent and non-coherent demodulation and is used in direct sequence spread spectrum (DSSS) PRY of IEEE Std 802.11 and in IEEE Std 802.15.3. A typical constellation for DQPSK is illustrated in Figure 6 .

Figure 6:

•

•

•

•

Example of constellation for DQPSK modulation

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IEEE Wireless Dictionarv

digital advanced mobile phone service (D-AMPS): An early name for the IS-I 36/TDMA 20 mobile phone standard. See also: time division multiple access (TDMA). digital enhanced cordless telecommunications (DECT)14: A standard for digital cordless telephones, it uses the 1.9 OHz band in Europe and allows multiple handsets to share a single base station. Because the 1.9 OHz band is allocated for mobile phones in the U.S., some manufacturers have adopted DECT systems to operate in the U.S. by using essentially the same protocol and PHY in the 2.4 OHz ISM band. digital to analog converter (DAC): A device that takes a number, usually binary, as an input at regular intervals and produces an analog voltage on its output that is proportional to the number that was input. dipole antenna: An antenna with two co-linear radiating elements that are excited with opposite phases. A half-wave dipole antenna is a dipole antenna whose overall dimension is one-half of the wavelength of its primary operating frequency. Each ann of a half-wave dipole is then one-quarter of a wavelength long. direct conversion radio (DCR): A radio architecture in which the signal is directly converted between baseband and RF. This tenn nonnally refers to the receiver architecture, but it can also refer to the architecture of the transmitter. It is

14

28

The original expansion was Digital European Cordless Telecommunications.

IEEE Wireless Dictionary

IEEE Wireless Dictional'\'

possible for a radio to have a direct conversion transmitter but have a super-heterodyne receiver (and vice-versa). direct sequence spread spectrum (DSSS): A spread spectrum technique that spreads the transmitted infOlmation bandwidth by converting each bit or set of bits into a larger number of transmitted elements, called chips. The chip rate (the rate at which the chips are sent) is greater than the bit rate (the rate at which the bits are sent), thereby expanding the bandwidth. While it is common in DSSS systems for each individual bit to be expanded by a digital code, there are DSSS systems. e.g., CCK, that expand groups of bits. Examples of DSSS systems in use today include IEEE 802.11 DSSS, IEEE 802.11 CCK, and CDMA. See also: chirp modulation, frequency hopping spread spectrum (FHSS). and spread spectrum. directivity: The ratio of the radiation intensity in one direction by an antenna to the radiation intensity averaged over all directions. Typically, the directivity is specified as a single number, expressed in dBi, without a direction and indicates the maximum directivity of the antenna. Note that the efficiency of an antenna is not included in determining its directivity, but it is included in determining the gain Thus an antenna will have a gain that is less than its directivity. See also: decibels relative to an isotropic radiator (dBi) and gain. duplex (full duplex): A communications system in which a device in normal operation is transmitting and receiving at the same time.

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

dynamic host configuration protocol (DHCP): A method for dynamically assigning internet protocol (IP) addresses in a network. It also distributes necessary network information, e.g., default gateway address, subnet mask, broadcast address, etc. DHCP is defmed in RFC 2131.

dynamic range: The ratio of the highest level signal to the lowest level signal for a system or a device, normally expressed in dB. This term is used in a variety of applications, from speakers to mixers to ADCs. The lower level is determined by a noise-related specification, i.e., the desired signal needs to be a certain number of dB above the noise floor. The upper level is bounded by a distortion-related limit of the signal for high signal levels. The criteria for determining the lower limit and upper limit depend on the specific application. Once the application has been defined, it is still necessary to pick limits, below which the effect of noise or above which the effect of distortion are considered to be unacceptable. Thus, it is important when comparing the dynamic range of systems or devices to ensure that they are being measured against the same criteria.

EbINO: The energy per bit (Eb) divided by noise power spectral density (No), usually expressed in dB. The EblNO ratio is a key parameter in determining the BER for a communication system. It is not necessarily the same as the SNR. The two are related by

where SIN is the SNR, BW is the signal bandwidth and R is the bit rate.

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IEEE Wireless Dictionmy

IEEE Wireless Dictionary

effective number of bits (ENOB): A measure of the perfonnance of a data converter. A data converter is designed to have a specific number of bits as the output (ADC) or the input (DAC). Given the number of bits, the ideal signal to noise ratio for a data converter can be calculated from SNR (dB) = 6.02*(number of bits) + 1.76 dB However, due to imperfections in the design and implementation of the data converter, the actual SNR will be less than this value. One way to express this loss of SNR is to state the number of bits that the SNR corresponds to by calculating ENOB = (SNR (measured) - 1.76 dB)/6.02 Thus a I O-bit data converter that has an SNR of 59 dB would have 9.5 ENOB. Electronic Communications Committee (ECC): One of the committees of the European Conference of Postal and Telecommunications Administrations (CEPT). Fonnerly known as the European Radio Committee (ERC). the Electronic Communications Committee (ECC) deals with spectrum engineering, frequency management, and radio regulations. Electronics Industries Alliance (EIA): A trade organization of electronics manufacturers in the U.S., ErA also maintains various standards bodies, such as the Telecommunications Industry Association (TTA) and JEDEC Solid State Technology Association (JEDEC)lS.

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

endian: The order in which bytes are arranged in memory or the order in which they are transmitted over a medium. Bigendian systems send the most significant bytes first and/or store them at the lowest addresses in memory. Little-endian systems send the least significant byte first and/or store them at the lowest address in memory. enhanced data-rates for GSM evolution (EDGE)16: A 3G standard 17 for mobile telephones that is an evolution of the Global System for Mobile Communications (GSM) and General Packet Radio Service (GPRS) standards. Enhanced Data-Rates for GSM Evolution (EDGE) improves on GSM by using 8-PSK instead of GMSK, which provides for data rates that, ideally, are three times faster than GSM. EDGE provides data rates of up to 384 kb/s, but only under very limited conditions. Typical data rates will be less.

enhanced distributed channel access (EDCA): One of two methods for improving the quality of service (QoS) in IEEE Std 802.11 e. Enhanced Distributed Channel Access (EDCA) is an extension to the CSMA/CA methods defined in 15

16

17

32

JEDEe originally stood for Joint Electron Device Engineering Council, but has a new name now to renect its broader range of work. This acronym has many different definitions floating around including: enhanced data GSM environment, enhanced data-rates for global evolution, and enhanced data for global evolution. The third generation partnership project (3GPP). which wrote the EDGE standard, expands the acronym as shown in the definition. EDGE is sometimes classified as a2.5G or 2.75G standard, butthere really isn't a hard and fast rule that determines the generation of a particular standard, so we will give it the benefit of the doubt and call it 3G.

IEEE Wireless Dictionary

IEEE Wireless Dictionm:v

IEEE Std 802.11. EDCA changes the backoffwindow used for gaining access to the medium based on the priority of the data. This influences the probability for gaining access to them medium, but does not guarantee improved access. European Conference of Postal and Telecommunications Administrations (CEPT)18: CEPT is the body of policy makers and regulators for almost the entire European geographic region, including Central and Eastern Europe. CEPT has members from 46 European countries. European Telecommunications Standards Institute (ETSI): Created by CEPT in 1988, the European Telecommunications Standards Institute (ETSI) develops telecommunications standards for information and communications technology in Europe. evolution-data optimized (EV-DO): See: CDMA2000® lx evolution-data optimized (lxEV-DO). evolution-data and voice (EV-DV): See: CDMA2000® Ix evolution-data and voice (lxEV-DV). extensible authentication protocol (EAP): A security protocol (RFC 2284) originally designed for the point-to-point protocol (PPP). In extensible authentication protocol, the supplicant sends the relevant user information, typically the user name and password to the access point. The access point then either uses this information to authenticate the user by one

IR

The acronym is derived from the French name, Conference Europeenne des Administrations des Postes et des Telecommunications.

IEEE Wireless Dictionm:v

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IEEE Wireless Dictionary

of several means, each with varying levels of security, or passes the information to another server to do the authentication. Many implementations use a remote authentication dial-in user service (RADIUS) server for authentication, especially for applications that have a dedicated Information Technology (IT) staff that are capable of setting up the server. extremely high frequency (EHF): A frequency band that extends from 30 GHz to 300 GHz. See: frequency bands. extremely low frequency (ELF): A frequency band that extends from 30 Hz to 300 Hz. See: frequeucy bands. fast fourier transform (FFT): A mathematical algorithm that efficiently converts discrete time domain samples into a frequency domain representation. Federal Communications Commission (FCC): The Federal Communications Commission (FCC) is a U.S. regulatory body, responsible directly to Congress. The FCC is charged with regulating interstate and international communications by radio, television, wire, satellite and cable. Lt is also one of two governmental organizations that manage the use of spectrum the U.S .. The National Telecommunications and Infonnation Administration (NTIA) manages the federal use of spectrum in the U.S. while the FCC manages all other lIses. See also: National Telecommunications and Information Administration (NTIA). first generation (lG): The first generation of mobile phones that used analog modulation, in particular frequency modulation (FM). The first generation (1 G) standards include

34

IEEE Wireless Dictionary

IEEE Wireless Dictionary

advanced mobile phone service (AMPS), narrowband advanced mobile phone service (NAMPS), Nordic Mobile Telephone (NMT) and total access communication system (TACS).

fixed wireless: Any wireless system in which the positions of the antennas are fixed for long periods of time. forward error correction (FEe): A technique used to improve the performance of a digital system by reducing the EblNO required to achieve a particular BER. The transmitting device adds additional bits of information to a block of data that can be used by the receiver to correct bit errors in that block of data. Although this reduces the overall throughput of the system under ideal, noiseless conditions, good codes will provide significantly improved BER performance under noisy conditions. A forward error correction (FEC) code is described by the algorithm name, e.g., Reed-Solomon, Turbo, etc., and a coding rate, e.g., 5/8. The coding rate expresses the ratio of the num bel' of information bits to the number of bits sent. In the 5/8 example, for every five bits of infon11ation that are sent, three additional bits are added to detect and correct errors, for a total of eight bits sent. Thus, a 5/8 code operates at 62.5% of the uncoded bit rate and therefore has an overhead of 37.5%. fourth generation (4G): Soon after work began to define what 3G would be, people began to speculate about the next generation. Various systems claim to be fourth generation (4G), including Wi-Fi® (IEEE 802.11), Wi MaxTh' (IEEE 802.16™), and various upgrades to the current 3G standards. As there is no accepted way to detennine the generation to which a

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

particular standard belongs, the assignment of these designations is more a marketing activity than a technical one.

fractional bandwidth: Generally expressed as a percentage, the fractional bandwidth is calculated from

where fL is the lowest occupied frequency and fH is the highest occupied frequency. fL and fH are nonually defined as the point at which the signal has been reduced by a specified number of dBs. There is not a consensus on the number of dB and values of3, 10,20, and 25 dB have all been used or suggested at some point. The fractional bandwidth of a system or component is used to detel1l1ine if it is a narrow band « 1%), wide band

(> 10%) or ultra-wide band (> 20%). The divisions between these designations is only approximate as not everyone agrees to the percentages.

frequency division duplex (FDD): A communication system in which a device transmits on one set of frequencies and receives on another set of frequencies. Frequency division duplex systems can be either full-duplex or half-duplex. Mobile phone standards use FDD with one set of channels reserved for downlink (i.e., from the base station to the user tenninal) and another set reserved for uplink (i.e., from the user tenuinal to the base station). However, some mobile phone standards are full-duplex, e.g., advanced mobile phone service (AMPS) and carrier sense, mUltiple access (CDMA), while others are half-duplex or time division duplex (TDD),

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IEEE Wireless Dictiol1G1:v

e.g., Global System for Mobile Communication (GSM) and time division mUltiple access (TDMA). frequency division multiple access (FDMA): A method for sharing a fixed bandwidth among multiple users. FDMA allocates a distinct frequency band for each of the users in the system, as illustrated in Figure 7. Although not strictly required, FDMA systems typically have channel bandwidths that are equal. In some instances, e.g., cdmaOne and 3G mobile phone standards, multiple smaller channels are aggregated into a single allocation to enable additional functionality. Most modern systems (2G, 2.5G, 3G, IEEE 802.11, IEEE 802.15, etc.) employ a combination of FDMA and some other access method. For example, cdmaOne uses CDMA to share a 1.25 MHz bandwidth among multiple users, but also uses FDMA to enable more users by occupying multiple 1.25 MHz channels. AMPS is an example of a pure FDMA system; each mobile phone is assigned one frequency channel from its base station. See also: Code Division Multiple Access (CDMA), Frequency Division Multiplexing (FDM), and Time Division Multiple Access (TDMA).

CCYJ CCYJ. I •

I

~ Channel

Frequency

Frequency band to be shared

•

Key: n -> m - Device n sending data to Device m

Figure 7:

Example of a typical FDMA frequency allocation

IEEE rrireless Dictionary

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IEEE Wireless Dictionary

frequency division multiplexing (FDM): A communication system in which different signals, possibly from the same user, use distinct frequency bands to avoid interference. Almost all radio systems use some fonn of frequency division multiplexing along with other multiplexing and multiple access techniques. When multiple users are separated using different frequencies, the system is said to be using FDMA. See also: dode division multiple access (CDMA), frequency division multiple access (FDMA), time division multiplexing (TDM), and time division multiple access (TDMA). frequency hopping spread spectrum (FHSS): A spread spectrum technique in which the spreading is achieved by changing the transmission frequency, usually in a pseudorandom fashion. Frequency hopping spread spectrum systems are divided into two major categories, slow hopping and fast hopping. A slow-hopping FHSS system is one in which one or more complete bursts of data are sent on a single frequency before the system changes to the next frequency. A fasthopping system is one in which the frequency changes more than once during a burst of data, even to the point that the frequency may be changing during a symbol. There are many deployments of slow-hopping FHSS systems because it is significantly easier to create systems that change frequencies relatively slowly. Examples of slow-hopping FHSS systems are: IEEE 802.11-FHSS, HomeRF, Digital Enhanced Cordless Telecommunications (DECT) and Bluetooth®.19 Fast hopping FHSS systems were once only found in military systems, but

19

38

Bluetooth is the fastest ofthe slow-hopping system; it changes frequencies for each data frame.

IEEE Wireless Dictionmy

IEEE Wireless Dictionary

there is a proposed commercial system that has a mode of operation in which the frequency changes for each symbol. frequency modulation (FM): A modulation method in which the information is encoded in the instantaneous frequency of the signal. See also: frequency shift keying (FSK). frequency shift keying (FSK): A digital modulation system in which each of n bits is sequentially mapped to one of 2" frequencies. A common variation of frequency shift keying, Gaussian FSK, or GFSK, filters the data with a Gaussian filter prior to modulating the frequency. See also: frequency modulation (FM) and Gaussian frequency-shift keying (GFSK). gain (for an antenna): The ratio of the radiation intensity of an antenna in a given direction to the radiation intensity that would be obtained if the power accepted into the antenna were radiated isotropically. Because the gain is defined relative to an isotropic source, it is typically expressed in dBL Occasionally, the gain will be expressed relative to an ideal half-wave dipole, in which case it is expressed in dBd. Because the gain of an ideal half-wave dipole is about 2.14 dB, Gain (dBi) = Gain (dBd) + 2.14 dB. Antenna gain is a combination of the antenna's directivity and efficiency; to have high gain, the antenna must have both high directivity and low loss. While antenna gain is technically a function of direction, typically only the highest gain of the antenna is reported. When evaluating an antenna, the pattern of this antenna gain is often

iEEE Wireless Dictionary

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IEEE Wireless Dictionary

more important than a single gain number for the antenna. See also: directivity.

gain (for power, voltage, or current): The relative change in power, voltage, or current between the input and output of a device. When the type of gain is unspecified, power gain is usually implied. Voltage and current gain indicate changes in voltage and current, respectively. Gain is usually expressed in dB, but it may also be expressed as a linear ratio. Although gain implies an increase in power, it will occasionally have a negative value in dB, indicating a decrease in power. For example, mixers will often list conversion gain as a parameter but it will have a negative dB value, indicating a conversion loss.

Gaussian filter: A filter that has an impulse response that is proportional to the Gaussian distribution; i.e., -x l /(2,i)

G(X)

=

e'--_ _

aj2ir The magnitude of the frequency response is also proportional to the Gaussian distribution.

Gaussian frequency shift keying (GFSK): A modulation technique in which the data is first passed through a Gaussian low-pass filter before being modulated with FSK. See also:

frequency shift keying (FSK).

Gaussian minimum shift keying (GMSK): A modulation technique in which the data is first passed through a Gaussian low-pass filter before being modulated with MSK. See also: minimum shift keying (MSK).

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IEEE Wireless DictionmT

general packet radio service (GPRS): GPRS is 2.SG mobile phone standard that is based on GSM. GPRS extends GSM so that it can handle data in a more efficient manner. GSM is a TDMA system that uses time slots on the air in a given physical channel to share the available bandwidth among a group of mobile phones. GPRS improves the data rate by combining up to four time slots for downloading and two time slots for uploading to increase the GSM data rate to a theoretical data rate of about 170 kb/s. Global System for Mobile Communication (GSM)20: A 2G mobile phone standard developed by the European Telecommunications Standards Institute (ETSI), GSM has seen phenomenal success due in large part to the fact that it was the only 2G system allowed for deployment in Europe. GSM is a TDMA system that uses Gaussian minimum shift keying (GMSK) modulation. The GSM standard had a number of innovations including the use of subscriber identity modules (SIM) and SMS. See also: second generation (2G), cdmaOne, subscriber identity module (SIM), and short messaging service (SMS).

half-duplex: A communications system in which a device in normal operation does not transmit and receive at the same time. Rather, the device is either receiving, transmitting, or is inactive. handover: A feature of a wireless system in which the connection to a mobile device is transferred from one base station or access point to another without breaking the 20

Originally "Groupe Speciale Mobile."

IEEE Wireless Dictionmy

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IEEE Wireless Dicfional:v

connection. Handover differs from roaming in that handover occurs within a single provider's network, whereas roaming involves switching the connection between different providers. HCF controlled channel access (HCCA): A channel access method in IEEE 802.lle that allows for contention-free access. Hybrid coordination function (HeF) controlled channel access is based on a polling protocol coordinated by the quality of service access point (QAP). HCCA can be used for uplink, downlink, or direct link connections [where two quality of service stations (QSTAs) send frames directly to each other rather than through the QAP]. high frequency (HF): A frequency band that extends from 3 MHz to 30 MHz. See: frequency bands. high-performance LAN (HiperLAN): A wireless local area network (LAN) standard developed by the European Telecommunications Standards Institute (ETSI). High-Performance LAN (HiperLAN) I was a single carrier system that never saw widespread deployments. The HiperLAN 2 and TEEE 802.11 a standards groups agreed to use the same PHY, differentiating the two standards based on the MAC. HiperLAN 2 never saw widespread deployment; a problem that was exacerbated when TEEE Std 802.11 a received approval for operation in Europe after adding dynamic frequency selection and transmit power control. high speed downlink packet access (HSDPA): A third and a half generation (3.5G) communications standard, high speed downlink packet access is an upgrade to wide band code division multiple access (WCDMA) that uses the 5-MHz radio

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IEEE Wireless Dictionary

channels but increases the downlink speeds from 2 Mb/s to 8-10 Mb/s (possibly up to 20 Mb/s using MIMO systems). HSDPA is a packet-based system rather than a connectionbased system, so it is capable of efficiently sharing a single channel among multiple users with asynchronous data requirements.

high speed packet access (HSPA): A generic term for 3G packet-switched protocols that encompasses both high speed downlink packet access (HSDPA) (downlink) and high speed uplink packet access (HSUPA) (uplink). See also: high speed downlink packet access (HSPDA) and high speed uplink packet access (HSUPA). high speed uplink packet access (HSUPA): A 3.50 mobile phone standard that provides up to 5.8 Mh/s in the uplink (terminal to base station) using a packet-switched protocol.

HomeRF: An industry working group that developed a specification for wireless connectivity at up to 10 Mb/s. The specification, called the Shared Wireless Access Protocol (SWAP), specified data rate initially at 1 and 2 Mh/s and later at 5 and 10 Mb/s. The physical layer (PHY) operated in the 2.4 GHz industrial, scientific, medical (ISM) band and was a slowhopping frequency hopping spread spectrum (FHSS) system using 2FSK and 4FSK. The protocol scheduled voice traffic using TDMA and data traffic with CSMA/CA. The HomeRF working group disbanded in January 2003. 21

homodyne: A radio in which the received signal is converted directly from radio frequency (RF) to baseband without an

IEEE Wireless Dictionary

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IEEE Wireless DictionalY

intennediate frequency. See also: direct conversion radio (DCR), super-heterodyne, very low intermediate frequency (VLIF), and zero intermediate frequency (ZIF).

hybrid coordination function (HeF): A function defined in IEEE S02.11e that enables quality of service (QoS) improvements to IEEE 802.11 by coordinating enhanced distributed channel access (EDCA), HCF controlled channel access (HCCA), and the legacy contention access functions in the operations of an IEEE 802.11 station (STA).

IEEE 802.11 working group: An IEEE Standards working group that is developing standards for wireless local area networks (WLANs). All IEEE 802.11 ™ physical layers (PHYs) use the same medium access controller (MAC) which is based on carrier sense multiple access/collision avoidance (CSMA/CA). To date, a total of nine different PHYs have been defined in IEEE Standard 802.11, with most of them being opti onal. 22 IEEE 802.11 standards: The IEEE 802.11 working group has been busy improving the original standard, IEEE Std 802.1 1'"-1997, which specified a single medium access

21

22

44

In what mayor may not be ironic, MC-link, which is what became the Bluetooth specification. was originally proposed to the HomeRF working group. The Hom~RF group picked a different proposal, and the rest is history. The nine PHYs are: JR, FHSS, DSSS, CCK. PBCC, OFDM, DSSSOF OM, ERP-OFOM, ERP-PBCC. This doesn't count ERP-OSSS and ERP-CCK, which are basically the same PHYs as OSSS and CCK but with some small modifications to work with the new PHYs in IEEE Std 802.l1g.

IEEE Wireless Dictional)'

IEEE IYireless Dictionarv

controller (MAC) sub layer and three physical layers. Amendments to the standard are now increasing data rates, improving security, providing quality of service, and more. Each amendment or revision to the standard is generally assigned a new letter as part of its designation. The first amendment approved for development was therefore IEEE Std 802.11 aTM?3 Some of the amendments to IEEE Std 802.11 are only of interest to implementors, but there are some amendments that come up more often. The more popular amendments to IEEE Std 802.11 are listed in Table 2 on page 46. 24 There are exceptions to the use ofa letter as pati of the name of the amendment, revision, or recommended practice. For example, the IEEE 802.11T Task Group is developing a recommended practice that will be called IEEE Std 802.11.2TM as opposed to IEEE Std 802. liT.

image frequency (IF): The frequency that will be converted to the same intermediate frequency (IF) as the desired signal after it is multiplied by the Local Oscillator (LO) in the mixer of a superheterodyne system. The image frequency is offset from the LO by the IF, on the opposite side of the RF signal. The image frequency can be calculated from fimage

=

2*fLO - fRF

industrial, scientific, medical (ISM) band: Frequency bands allocated by the ITU for industrial, scientific, and medical use. The Federal Communications Commission (FCC) " IEEE Std 802.11 b was approved at roughly the same time, but one of them had to be 'a' and the other 'b'. 24 For the most current information on IEEE 802.11 activities, visit the working group's website at: http://grouper.ieee.org/groups/8021111.

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IEEE Wireless Dictionary

Table 2: Designation

Selected IEEE 802.11 amendments Summary

IEEE Std 802. II a'''-I 999

Alternate PHY in the 5 GHz band, uses OFDM with data rates up to 54 Mb/s.

IEEE Std 802.1Ib"'-1999

Alternate PHY in the 2.4 GHz band, compatible with DSSS, it uses CCK with data rates up to II Mb/s.

IEEE Std 802.11 e-'''2005

Amendment to provide QoS for the MAC.

TEEE Std 802.IIF'''-2003

Recommended practice to allow APs from different vendors to interoperate.

TEEE Std 802. Ilg"'-2003

Alternate PHY in the 2.4 G I [z band, compatible with DSSS and CCK, it uses OFDM with data rates up to 54 Mb/s.

IEEE Std 802.11h"'-2003

Amendment that enables IEEE 802.11a devices to meet European requirements.

IEEE Std 802.11 ('-2004

Amendment to provide improved security for the MAC.

IEEE Std 802.11/"-2004

Provides mechanisms for signalling compliance with regulatory domain requirements ofthe USA, Europe, and Japan; for extending 5 GHz orthogonal frequency division multiplexing (OFDM) physical layer (PHY) operation outdoors; and for 5 GHz OFDM PIIY operation in nonoverlapping 10 MHz channel spacing.

IEEE P802.lln""

Alternate PHY, in development now. The requirement is that it delivers more than 100 Mb/s of throughput (not instantaneous data rate).

The "P" designation before "SOl. lin" indicates that this is a standards project in process and has not yet been approved by the IEEE Standards Association.

46

IEEE Wireless Dictionary

IEEE Wireless Dictionary

regulations (47 CFR 18.107) list typical ISM applications as "the production of physical, biological, or chemical effects such as heating, ionization of gases, mechanical vibrations, hair removal and acceleration of charge particles," although, in later years, short-range consumer wireless systems, such as WLANs and WPANs, have come to dominate the bands once largely used only by microwave ovens. The FCC regulations list 11 frequency bands for operation of ISM equipment, from 6.78 MHz to 245 GHz, but the 902 to 928 MHz, 2.4 to 2.4835 GHz, and 5.725 to 5.850 GHz are those used for wireless systems at present. (Not all bands are available in all countries and the rules in each country can vary.)

Infrared Data Association (IrDA): An industry group that develops specifications for infrared wireless 25 communications. The IrDA group has specified not only the medium access controller (MAC) and physical layer (PHY), but also application level protocols like infrared object exchange (IrOBEX). The IrDA specifications are focused on simplicity and low cost so that they can be applied to a wide variety of devices. 26 IrDA has become so successful in the wireless infrared space that it has become synonymous with infrared connectivity. Remote controls, which have even more strict cost constraints, are one ofthe few infrared applications that do

25

26

It isn't really possible to have a "wired" optical link in the sense ofa connection that uses conductors. However. there are optical links that use waveguides, e.g., fiber optics, and ones that are wireless, e.g., IrDA. IrDA has set the standard for low-cost, wireless links. The requirement for a $5.00 Bluetooth radio came from a desire to replace IrDA connections at roughly the same price point.

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

not use IrDA. Despite this success, there have been many attempts to replace IrDA with RF wireless technology like Bluetooth®. Two main reasons for replacing IrDA are the greater range available at radio frequencies and removing the requirement for the devices to be pointed in a specific direction.

infrastructure mode: Tn TEEE 802.11, this refers to a wireless local area network (WLAN) that has at least one access point (AP) that is controlling access to the WLAN. See also: ad-hoc mode. Institute of Electrical and Electronics Engineers, Inc. (IEEE): The Institute of Electrical and Electronics Engineers, Inc. (IEEE) is a non-profit, technical professional association of more than 365,000 individual members in approximately 150 countries. Through its members, the IEEE is a leading authority in technical areas ranging from computer engineering, biomedical technology and telecommunications, to electric power, aerospace engineering and consumer electronics, among others. Through its technical publishing, conferences and consensus-based standards activities, the IEEE produces 30 percent of the world's published literature in electrical and electronics engineering, and computer science areas, holds more than 300 major conferences annually and has nearly 900 active standards with almost 500 under development.

integral nonlinearity (INL): A performance measure of data converter. The integral nonlinearity is expressed either in least significant bits (LSBs), where I LSB is equivalent to changing the digital code by one, or as a percentage of the

48

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IEEE Wireless Dictionarv

full-scale range. The INL is the difference between an ideal straight line transfer function and the actual transfer function for the data converter. One method for determining the INL is to use a linear least squares fit to the measured data to determine the straight line. Another method uses the zero and full-scale values as the endpoints of the line. The INL is the maximum deviation between the measured values and the ideal straight line transfer function for any of the codes. See also: differential non-linearity (DNL).

integrated digital enhanced network (iDEN): A mobile phone system designed by Motorola® to operate and coexist with existing 2-way radios. The integrated digital enhanced network system uses time division mUltiple access (TDMA) with 200-kHz frequency channels, which is the same as Global System for Mobile Communication (GSM). One of the distinguishing features of iDEN is the push-to-talk (PTT) capability that derives from its heritage as a two-radio system. Other system providers that use GSM and code division multiple access (CDMA) have been working to add PTT to their mobile phone systems. intermediate frequency (IF): A frequency other than the baseband or radio frequency (RF) in a transmit or receive chain that is used to carry the desired signal. A radio will have 0 or more IFs depending on the architecture of the system. In radios that use an IF, the channel selectivity is often done at the IF. Using an IF allows the radio designer to distribute the required gain at different tJ:equencies. This avoids the need to have too much gain at a single frequency which can lead to instabilities.

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IEEE Wireless Dictionary

International Organization For Standardization (ISO)27: An international federation of hundreds of standards bodies that cover a wide variety of topics, including WLAN s (ISO 8802-11), film speed (ISO 5800), CD-ROM data format (ISO 9660), and quality management systems (ISO 9001).

International Radio Consultative Committee

(CCIRf8: The old name for the ITU Radiocommunications sector (ITU-R). See also: International Telecommunications Union (ITU).

International Telecommunications Union (ITU): An international organization within the United Nations whose purpose is to develop radio standards and regulate international radio usage. There are three main divisions of the ITV; ITU-R, lTV Telecommunications standardization sectors (lTU-T), and the lTV Telecommunications development bureau (lTU-D). The lTV also develops recommendations for spectrum policy with the goal of creating worldwide allocations of spectrum for specific uses. Internet Engineering Task Force (IETF): The Internet Engineering Task Force (IETF) is an open, volunteer organization that develops standards for the internet. The IETF issues documents called Requests For Comments (RFCs), which, 27

28

50

As with many acronyms that are of an international character, the order of the words in the English translation may not conform to the order of the letters in the acronym. The main reason for this is that in other languages, e.g., French and Spanish, the adjective follows the noun, whereas, in English, it usually precedes the noun. In French, the name was Comite ConsultatifIntemational des Radiocommunications.

IEEE Wireless DictionaJ:V

IEEE Wireless Dictio/lm:v

when approved, become Internet standards. The IETF has standardized such things as email, TCP/IP, etc. The lETF reports to the Internet Activities Board (lAB), which, in tum, is a part of the Internet Society (ISOC).

internet protocol (IP): A data protocol for communicating data across a packet-switched network. IP is an unreliable delivery mechanism and so applications that require reliability need to supply it at a higher layer. IP exists today in two forms. IPv4, which is the fourth version of IP, but the first that was widely deployed, and IPv6, which is the latest version and is still in the process of being widely deployed. inverse fast fourier transform (IFFT): An algorithm that is able to efficiently convert discrete frequency domain samples into a time domain representation. iridium: A system of LEO (Low Earth Orbit) satellites that provides global mobile telephone service. The original concept had 7 polar orbits with 11 satellites in each orbit for a total of 77 satellites, which is the same as the number of electrons in an Iridium atom. The final system had 66 satellites, 11 satellites in each of 6 polar orbits, with spares also in orbit. Iridium was conceived and developed by Motorola® and began service in . November 1998 as the Iridium corporation which had telecommunications providers from around the globe and Motorola among the investors. Iridium failed to attract sufficient subscribers fast enough and declared bankruptcy in August 1999. The assets were bought by a group of private investors that re-stmied the company in 2001 and it is currently offering service with the U.S. government as a major customer.

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IEEE Wireless Dictionary

isotropic radiator: An ideal antenna that radiates equally in all directions.

LANIMAN Standards Committee (LMSC): Sponsored by the IEEE Computer Society, the IEEE 802 LMSC develops standards for LAN/MAN data networking. The most widely used IEEE 802 standards are Bridging and Virtual Bridged LANs (IEEE 802.I'M), Ethernet (IEEE 802.3'M), Token Ring (IEEE 802.5"), WLAN (IEEE 802.11'''), WPAN (IEEE 802.15.1"', IEEE 802.15.3''', IEEE 802.15.4"''), and WMAN (IEEE 802.16"'). Lansford's law: "Moore's Law doesn't apply to spectrum!" Unlike transistors, which get smaller, cheaper, and faster every year, the supply of spectrum (i.e. wireless bandwidth) is relatively fixed. Because of this, instead of getting cheaper, spectrum can become more expensive over time as the supply of "good" spectrum is reduced. (Originally stated by Jim Lansford, Ph.D.).

least significant bit (LSB): The lowest order bit in a binary number or bit string. It is the multiplier of2° = 1 and so it represents values of 0 or 1. In plural form, it refers bits that are closest to and including the LSB. The acronym LSB is sometimes used to refer to the lowest order byte and so sometimes LSb or lsb will be used for bits and LSB for bytes. Ifit is not defined clearly, the meaning ofLSB needs to be determined from the context. least significant byte (LSB): The lowest order byte (8 bits) in a binary number or byte string. In a binary number, this byte is the multiplier of 16° and so it represents values of 0 to 15.

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lEEE Wireless Dictionary

The acronym LSB is sometimes used to refer to the lowest order bit and so sometimes LSb or Isb will be used for bits and LSB for bytes. If it is not defined clearly, the meaning of LSB needs to be deterrninded from the context.

line of sight (LOS): A radio channel in which there are no obstructions between the transmitting and receiving antennas. One of the consequences of a line of sight (LOS) channel is that the dominant signal received is from the direct path, as opposed to a non-line of sight (NLOS) channel which may not have a dominant signal because the received energy comes from multiple paths that includes reflection or diffraction.

local area network (LAN): A network that covers an area equivalent to a building or even a campus. The term LAN is used exclusively for wired networks as the tenn WLAN is used to indicate wireless versions. See also: metropolitan area network (MAN), personal area network (PAN), wireless local area network (WLAN), wireless metropolitan area network (WMAN), and wireless personal area networl, (WPAN). local multipoint distribution service (LMDS): A broadband, fixed wireless system for voice, data, and multimedia. Local Multipoint Distribution Service (LMDS) uses a point-to-multipoint topology. similar to mobile phones except that the user tenninals are fixed in position rather than being mobile. Fixed end points allow the use of high-gain antelmas, which improves the distance and data rate that can be achieved. LMDS systems offer coverage areas of 3 to 5 miles with data rates delivered to the users that range from 64 kb/s to 155 Mb/s. LMDS operates in licensed spectrum between

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IEEE Wireless Dictionary

27 and 32 GHz in the U.S. and other frequency allocations are available in many other countries.

local oscillator (LO): A frequency source in a radio that is used to conveli the signal up or down in frequency by multiplying the signal with the LO. Multiplication of the signal with a single sinusoidal tone results in two products, fRF = fLO + flF and tRF = fLO - fiF' High-side injection is when the LO is higher in frequency than the radio frequency (RF) and low-side injection when the LO is lower in frequency than the RF. If the LO is equal to the RF frequency, the process is referred to as direct conversion.

logical channel: A specific data connection between communicating devices. Logical channels can defined be independent of the underlying physical channel. One or more logical channels can be carried by a single physical channel using a mUltiple access method, e.g., code division multiple access (CDMA) or time division multiple access (TDMA). logical link controller (LLC): The higher of two sublayers that make up the data link control (DLC) layer in IEEE 802 networking standards [the other is the medium access control (MAC) sublayer]; see "OSI 7-layer protocol model" on page 4. The LLC uses a flat addressing scheme in which each address, called the MAC address, is associated with a networking device at the time ofmanufacture. 29 The LLC can also directly

2,

54

While this is generally true, there are legitimate reasons to fake the MAC address, so it is possible in some instances to change the value that a device reports to the network.

IEEE Wireless Dictionary

IEEE Wireless Dictionary

transfer messages to different network segments based on the MAC address, a technique referred to as bridging or switching.

low frequency (LF): A frequency band that extends from 30 kHz to 300 kHz; see "Frequency bands" on page 2.

low intermediate frequency (LIF): A superheterodyne radio architecture in which the IF is so low that the image frequency occurs in the radio frequency (RF) passband. Along with zero intermediate frequency (ZIF) and very low intermediate frequency (VLlF), this architecture is popular in single-chip radios because it can be designed such that external channel select filters are not required. See also: direct conversion receiver (DCR), homodyne, super-heterdyne, very low intermediate frequency (VLIF), and zero intermediate frequency (ZIF). low probability of intercept (LPI): A characteristic of a communications system that is difficult to detect by an adversary. Low probability of intercept systems generally require some form of the protocol to be secret to prevent eavesdroppers from finding and receiving the communication. master: In the context of wireless protocols, this refers to a device that controls the operation ofa network. The most common usage of this term is in connection with the Bluetooth® specification in which the master provides the reference timing and controls all traffic in the network. medium frequency (MF): A frequency band that extends from 300 kHz to 3 MHz; see "Frequency bands" on page 2.

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IEEE Wireless Dictionary

medium access controller (MAC): The lower of two sublayers that make up the data link control (DLC) layer in an IEEE 802 networking standard. The MAC controls access to the medium by the physical layer (PHY), determines if the data was received correctly by checking a check sum, and filters out frames received by the PRY but not intended for the device. One of the purposes of the MAC is to hide the details of the PHY from the higher layers so that the networking stack will work in a variety of media. MACs for wireless media will often include link-layer security due to the open nature of a wireless PRY. message authentication: Also referred to as message integrity, this is the process of verifying that a message sent by a party has not been changed before it was received. Note that message authentication does not provide confidentiality for the contents of the message. See also: authentication and confidentiality. metropolitan area network (MAN): A network that covers an area equivalent to a city or portions of a city. The tenn is used exclusively to refer to wired networks with the term WMAN used to indicate wireless versions. See also: local area network (LAN), personal area network (PAN), wireless local area network (WLAN), wireless metropolitan area networ\{ (WMAN), and wireless personal area network (WPAN). minimum discernible signal (MDS): The minimum signal power input to a radio that will meet a specified performance criteria. In digital modulation systems, the performance criteria is usually a maximum BER.

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IEEE Wireless Dictiol1Q/~v

minimum shift keying (MSK): A modulation method based on quadrature phase-shift keying (QPSK) in which each bit determines a phase shift for the next symbol, either -90° or +90°, as shown in Figure 8. Unlike QPSK, a phase shift of 180° between symbols is not allowed. One of the advantages of MSK is that it avoids transitions through zero (180 degree transitions) and so it can have a lower peak to average power ratio. See also: gaussian minimum-shift keying (GMSK), quadrature phase-shift keying (QPSK), and 11:/4 differential quadrature phase-shift keying (11:/4 DQPSK). Allowed transitions

\K-+-l-.ra"n~siti!

not allowed

• Figure 8:

Example of a constellation for MSK modulation

mobile internet protocol (MIP): An Internet Engineering Task Force (IETF) standard communications protocol that allows mobile users to maintain connectivity and their internet protocol (IP) addresses even as the users move to different networks. Packets that are sent to the user's IP address are

IEEE rFireless Dictionary

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IEEE Wireless Dictionary

captured by an agent operating in the user's home network and are then tunneled to the network in which the user is currently operating.

Moore's law: An empirical 30 observation made by Gordon Moore, "the complexity for minimum component costs has increased at a rate of roughly a factor of two per year." Moore was considering the optimum number of components (e.g., transistors) that could be placed on an integrated circuit "optimum" in the sense of "lowest cost per component." If too few transistors are placed on an integrated circuit, packaging and testing costs rise, since more integrated circuits must be packaged and tested to perform a given system function. If too many transistors are placed, yields of the circuit degrade, also raising costs. Therefore, there is an economically-optimum number of transistors to place on an integrated circuit for the lowest cost per transistor. It was Moore's observation that, with improving technology, this optimum number of transistors was increasing rapidly, without apparent bound. In 1975, Moore changed his observation to indicate that the complexity was roughly doubling every 2 years.3! Moore's law does not apply directly to wireless systems even though they are made with semiconductors. On reason is that analog and radio frequency (RF) circuits only use a relatively small 30

31

58

Originally published in Electronics, Number 8, April 19, 1965. Moore did not refer to it as 'law,' that term was applied later by Carver Mead. The law has also been quoted as an 18-month interval, but Sematech'" uses 2 years as the cycle for its roadmap. (Scmalech is a consortium that develops advanced semiconductor manufacturing processes, materials, and equipment for member companies.)

IEEE Wireless Dictionary

IEEE Wireless Dictionary

number of transistors, and most of the space in an analog or RF integrated circuit is filled with the passive devices, Le., inductors, capacitors and resistors. This is changing as the price of transistors drops dramatically due to Moore's law and new radio architectures are developed that take advantage of this. Moore's law does not apply to radio spectrum either32 , although techniques like multiple input, multiple output (MIMO) have been enabled by the falling prices of radios and digital logic.

most significant bit (MSB): The highest order bit in a binary number of bit string. Ifthere are 11 bits in the number, then the most significant bit (MSB) is the multiplier of 2"- 1• In plural form, it refers bits that are closest to and including the MSB. The acronym MSB is often used to refer to the highest order byte and so sometimes MSb or msb will be used for bits and MSB for bytes. Ifit is not defined clearly, the meaning of MSB needs to be determined from the context.

most significant byte (MSB): The highest order byte (8 bits) in a binary number or byte string. In a binary number that is 11 octets long, this byte is the multiplier of 16/1-1. In plural fonn it refers to the bytes that are closest to and including the MSB. The acronym MSB is sometimes used to refer to the highest order bit and so sometimes MSb or msb will be used for bits and MSB for bytes. If it is not defined clearly, the meaning of MSB needs to be determined from the context. multichannel, multipoint distribution system (MMDS): A wireless broadband communications system for 32

See Lansford's law.

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IEEE Wireless Dictionary

data communications or to deliver cable television. A multichannel, multipoint distribution system is a fixed, point to multipoint system and so it uses high-gain antennas to get high data rates at long ranges. Data rates for MMDS can be as high as 10 Mb/s with ranges of up to 70 miles in LOS environments. MMDS uses licensed frequency allocations in the 2 to 3 GHz range.

multiple access protocol: A MAC sublayer protocol that enables multiple devices to access a single physical channel. multiple input, multiple output (MIMO): A technique in which a radio with two or more transmitters sends two or more unique data streams in the same frequency and physical space to another radio that has two or more receivers. At the receiving end, the signals from the multiple receivers are combined to recover the original transmitted streams. Because the signals from each of the transmitting antennas travel in slightly different paths, it may be possible for the receiver to distinguish between them and recover all of the transmitted data streams. The key advantage ofMTMO systems is that the data rate in a given frequency allocation can be increased without increasing the occupied bandwidth. Ideally, the data rate in the radio channel will scale linearly with the number of transmitters in the system. MfMO systems are often described by the number of transmitters and receivers. For example, a system with two transmitters and two receivers is referred to as a 2x2 system. Tn MIMO systems, the number ofreceivers is greater than or equal to the number of transmitters. Not all systems with multiple antennas are MIMO systems. For example, beam fonning and receive antenna diversity, while

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IEEE Wireless Dictionary

improving perfonnance, are not MIMO systems because they do not send more than one distinct data stream in the same radio channel at the same time. See also: beam forming and diversity. narrowband advanced mobile phone service (NAMPS)33: An enhanced version of the AMPS standardized as IS-91. NAMPS is a 10 analog mobile phone standard. The NAMPS system uses IO-kHz channels instead of the 30-kHz channels used by AMPS, effectively tripling the capacity of an analog network. As with AMPS, NAMPS was used primarily in the u.s. and is now being phased out in favor of20 and 30 systems. See also: advanced mobile phone service (AMPS) and first generation (lG). National Telecommunications and Information Administration (NTIA): The NTIA acts as the U.S. President's advisor on telecommunications policy. It also acts as one of two organizations that manage spectrum in the U.S. The NTIA manages the federal use of spectrum, e.g., military and government, while the FCC manages all other uses. See also: Federal Communications Commision (FCC). network address translation (NAT): A technique for changing the source and/or destination addresses of internet protocol (IP) packets as they pass through the device implementing the NAT functionality. The most common use is to share a single external IP address among multiple hosts in an internal network. Unfortunately, the address translation can 33

Sometimes expanded as Narrowband Analog Mobile Phone System. See also AMPS.

IEEF Wireless Dictionary

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IEEE Wireless Dictionarv

break some applications that expect transparent end-to-end addressing. noise figure (NF): The ratio of the signal-to-noise ratio (SNR) at the output of a block to the SNR at the input of the block. The noise figure is often abbreviated as NF and is typically expressed in dB. An ideallossless block that introduces no additional noise would have a noise figure of odB. For systems or blocks that have very low noise figure, the noise temperature is listed instead. The noise temperature, T, is expressed in Kelvins and is related to the noise figure as follows: T(K)

=

290 x

lO[NF(dB)/IO-lj

non-line of sight (NLOS): A radio channel in which there are obstructions between the transmitting and receiving antennas. One of the consequences of a non-line of sight (NLOS) channel is that there may not be dominant signal received because of all of the reflected paths, as opposed to an LOS channel which in which the dominant signal comes from the direct path. See also: line of sight (LOS). Nordic Mobile Telephone (NMT)34: A IG mobile phone system used not just in the Nordic countries, but in many countries. NMT operated at 450 MHz and 900 MHz and is an analog FM system like AMPS. Like AMPS, NMT has been almost completely replaced by 2G systems, such as GSM in

34

62

The English translation of either Nordisk MobilTelefoni or Nordiska MobiITelefoni-gruppen.

IEEE Wireless Dictionary

IEEE Wireless Dictiol1G1Y

particular. NMT is still in use in sparsely populated areas such as lceland, where its superior coverage is an advantage. See also: advanced mobile phone service (AMPS), narrowband advanced mobile phone system (NAMPS) and total access communications system (TACS). nth-order input intercept point (lIP n): The point at which the power from the dh-order intermodulation product would equal the power ofthe desired signal measured at the input of the device. The nth-order input intercept point plus the gain of the device is equal to the dh-order output intercept point (OTP n). See also:nth-order intercept point (IP n) and nth-order output intercept point (OIP n)' 11 th -order

intercept point (IP n): A measure of a device's intemlOdulation perfonnance. Because no practical circuit is ever completely linear, multiple signals placed at the device's input will produce the desired output and additional spurious outputs called intennodulation products. These products can be at the frequency of a desired signal, even if the input signals were not, and so the intermodulation performance ofthe circuit can be a serious design issue. The nth-order intercept point is an imaginary point on a graph of input power versus output power of the device at which the extended line of the desired signal and the extended line of the dh-order intennodulation product, both expressed in dB, meet. In general, the power in the d h intermodulation products will increase linearly with input power with a slope of n while the power in the desired signal increases linearly with a slope of one, as shown in Figure 9 on page 65. The output intercept, 01 Pn is equal to the input intercept, lIP n plus the gain of the

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

device. The actual output power ofthe device under test will saturate before the intercept point is reached, so that IPn is calculated as an extrapolation of the I ines. In equation form, the OIP n is as follows:

where Rn is the suppression of the nth-order intermodulation products.

The IP either referred to the input, lIP11' or the output, OlP n. lIP n is typically specified for components used in the receive chain, e.g., low noise amplifiers (LNAs), while OTP n is specified for components used in the transmit chain, e.g., power amplifiers. nth-order output intercept point (OIP n): The point at which the output power from the dh-order intermodulation products would equal the output power of the desired signal. See also: nIh-order input intercept point (lIP II) and nIh-order intercept point (IP II)' on-off keying (OOK): A form of amplitude shift keying (ASK) modulation in which one bit is encoded into two states, one state is represented by zero amplitude and the other state by by a non-zero amplitude. See also: amplitude-shift keying (ASK) and amplitude modulation (AM). open systems interconnection-reference model

(OSI-RM): A networking layer model; see "OSI 7-layer protocol model" on page 4.

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IEEE Wireless Dictionary

Output Power (Pout) Extrapolated power of / nth intermodulation products / / OIPn

/ /

Extrapolated power of the desired signal

-----------------------------------------f /

/./ !

~!-=---

!

Slope

=1 Slope = ni IIPn

Figure 9:

Input Power (Pin)

Graphical representation of the output, OIP n , and input, IIP no intercept points

orthogonal frequency domain multiplexing (OFDM): A multicarrier radio system in which a single data stream is transmitted using more than one lower-rate subcarrier_ In addition, the bandwidth, filtering, and frequency separation of the subcarriers are selected such that sub carriers are mathematically orthogonal. A typical OFDM system generates the subcarriers digitally and applies an inverse fast fourier transfOlm (IFFT) to convert the frequency domain data into the time domain for transmission_ At the receiver, the time domain data is converted back into the frequency domain using an FFT. The

IEEE Wireless Dictionary

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IEEE Wireless Dictionarv

individual subcarriers are then demodulated to recover the data. Compared with single carrier systems, OFDM systems can offer excellent resistance to multipath fading, depending on the system design. However, they also have a much higher peak-to-average ratio which reduces the efficiency of the power amplifier and increases the required accuracy of the data converters.

packet error ratio (PER): The number of packets lost by a receiver due to an uncorrectable error divided by the total number of packets sent by the transmitter. pairing: A process by which Bluetooth'~ devices agree to communicate with each other and exchange encryption keys. The pairing process uses a passkey or a personal identification number (PIN) to attempt to verity that the identity of the Bluetooth devices. Unfortunately, some devices use a default PIN, which offers no security35. Even more unfortunate is that it is possible to recover the PIN by eavesdropping on the pairing process. Because it is possible for an attacker to force devices to repeat the pairing process, this is a security concern. personal area network (PAN): A network that covers a person and their immediate surroundings. In addition, a PAN is typically made of devices that are owned or controlled by a single user (or a close group, such as a family) and are neither leased nor part of a paid service. See also: local area network (LAN), metropolitan area network (MAN), wireless local

35

66

One web page that describes pairing offers the helpful advice that "Often, the passkey is a simple zero."

IEEE Wireless Dictionary

IEEE IFireless Dictionary

area network (WLAN), wireless metropolitan area network (WMAN) and wireless personal area network (WPAN). personal communications system (peS): A band of frequencies allocated in the u.s. for digital mobile phone service. It is also used sometimes to refer to the mobile phones that use this band for operation. The uplink (handset to basestation) frequency band is 1.85-1.89 GHz while the downlink (basestation to handset) frequency band is 1.93 to 1.97 GHz. New frequencies have recently been allocated for pes in the U.S., 2.130-2.150 GHz and 2.180-2.2 GHz. See also: second generation (2G). personal digital assistant (PDA): A mobile device that is used to perform relatively simple computational tasks, such as alarms, calendar, email, etc., and to store personal information. The lines separating PDAs from other mobile devices is gray, as many portable devices now perfom1 the functions previously performed by PDAs, and PDAs now perform the functions, such as music playback, wireless networking, telephone calls, etc., that were once done by single-function devices. personal digital cellular (PDq: A digital mobile phone standard deployed in Japan. Personal Digital Cellular (PDC) is considered a 2G system and uses TDMA like GSM and IS-136. PDC operates in the 800 MHz and 1500 MHz bands. See also: cdmaOne, Global System for Mobile Communications (GSM), second generation (2G) and TDMA (IS-136).

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IEEE Wireless Dictionary

personal handyphone system (PHS): A digital mobile phone system originally used in Japan, but now spreading to other countries in Asia. It was designed to be a cheaper alternative to the existing mobile phone systems by reducing the coverage area and supported only limited use in moving vehicles. A Personal Handyphone System (PHS) phone operates as a cordless phone when the user is in or near their home and as a mobile phone elsewhere. PHS supports voice, fax, and video. phase modulation (PM): A form of modulation in which the infonnation is encoded in the phase of the signal. See also: 8 differential phase-shift keying (8DPSK), Iso: 8 phase-shift keying (8PSK), differential quadrature phase-shift keying (DQPSK), rrJ4 differential quadrature phase-shift keying (n14 DQPSK) and quadrature phase-shift keying (QPSK). phase noise: A measure of the spectral purity of a frequency source. Ideally, a frequency generator creates a sinusoidal signal at the desired frequency. Imperfections due to losses and noise sources cause the frequency to change over time. For synthesized frequency sources, the jitter and loop characteristics of the phase-locked loop will also cause the frequency to change slightly over frequency. Phase noise is measured by dividing the average power at an offset frequency by the power at the desired frequency. Phase noise is generally expressed as x decibels relative to the carrier (dBc) at y kHz (or MHz) frequency offset and so should be a negative number, e.g., -80 dBc at 100-kHz offset. Phase noise in a receiver causes jitter in the received signal and also mixes out-of-channel interferers into the desired channel (reciprocal mixing). Phase

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~Vireless

Dictionary

noise in a transmitter increases the en-or in the transmitted constellation, which makes it more difficult for the receiver to conectly demodulate the data.

physical channel: The specific medium or portion of the medium used to create a connection between devices. For wireless systems, the physical channel is typically one or more frequency bands. The physical channel also includes all of the impamnents, e.g., multipath, frequency selective fading, and losses specific to the medium (rain fade, oxygen absorption, water vapor absorption, etc.). physical layer (PHy): The lowest layer of the OSI model, the PHY converts strings of bits to analog signals and back to bits again. nl4 differential quadrature phase-shift keying (n14 DQPSK): A modulation method in which pairs of bits to be sent are encoded as a change in the phase from the previous symbol rather than as an absolute phase as in nl4 QPSK. Allowed changes are in the phase are 45, 135, or 225 or 315 degrees from the previous symbol. Thus the constellation looks like 8 phase-shift keying (8PSK) except that not all phase transitions are allowed. One of the advantages of nl4 DQPSK is that it avoids transitions through zero (180 degree transitions) and so it can have a lower peak to average power ratio. See also: 8 phase-shift keying (8PSK), 8 differential phase-

shift keying (8DPSK), differential phase-shift I{eying (DQPSK), nl4 quadrature phase-shift keying (n14 QPSK) and quadrature phase-shift keying (QPSK).

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

n/4 quadrature phase-shift keying (n/4 QPSK): A modulation method in which pairs of bits to be sent are encoded as the absolute phase of the symbol. In addition, the phase of adjacent symbols is offset by rr/4 as shown in Figure 10. In QPSK and DQPSK, the next symbol is either 0, 90, 180, or 270 degrees from the previous symbol. In nl4 QPSK, the next symbol is 45, 135, or 225 or 315 degrees from the previous symbol. Thus the constellation looks like 8 phaseshift keying (8PSK) except that not all phase transitions are allowed. One of the advantages of rr/4 QPSK is that it avoids transitions through zero (180 degree transitions) and so it can have a lower peak to average power ratio.See also: 8 phaseshift keying (8PSK), 8 differential phase-shift keying (8DPSK), differential phase-shift keying (DQPSK), nl4 differential quadrature phase-shift keying (rr/4 DQPSK) and quadrature phase-shift l{eying (QPSK).

•

Even numbered symbols

•

Odd nwnbercd symbols

Figure 10: Example of constellation for nl4 QPSK modulation

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lEEE Wireless Dictionary

piconet controller (PNC): The coordinator in an IEEE 802.l5.3 piconet. The piconet controller controls the membership and timing allocations in the piconet. plain old telephone system (POTS): The wired communications system that is based on circuit-switched connections made up of analog and digital portions. The average person would simply know this as a telephone. However, the term POTS includes all of the infrastructure that connects a wireline telephone to another endpoint (which could be one end of a wireless network). push to talk (PTT): A feature in a mobile radio device that allows the user to push a button and speak with the result that speech is emitted from the speakers of other associated mobile radios without the intervention of the user on the remote end. In a traditional phone system, the user first has to dial a number and the remote user has to take an action to answer the call. PTT is also referred to as a walkie-talkie feature. This capability is common in two-way radio systems and is being added to many mobile phone systems due to the success of the iDEN system which has this feature. See also: integrated digital enhanced network (iDEN). quadrature amplitude modulation (QAM): A digital modulation technique in which the infonnation is encoded in both the phase and amplitude of the signal. Quadrature amplitude modulation signals typically use a rectangular constellation, as shown in Figure 11, but other shapes, e.g., hexagons, are possible. Four types of QAM modulation are iIlustmted in the figure, named for the number of points in the constellation, e.g., 32-QAM has 32 points in the constellation.

IEEE Wireless Dictionary

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IEEE Wireless Dictionarv

The number of bits encoded by a QAM symbol is log2(# points), e.g., 32-QAM encodes 5 bits per symbol. QPSK is equivalent to 4-QAM. See also: Amplitude Shift Keying (ASK), Bipolar Phase Shift Keying (BPSK), Frequency Shift Keying (FSK), and Quadrature PhaseShift Keying (QPSK). 16·QAM

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Figure 11:

Rectangular constellation for QAM

quadrature phase-shift keying (QPSK): A modulation technique in which pairs of bits are mapped onto one offour symbols, each with equal amplitude and separated by 90 degrees (n/2 radians) in phase, as illustrated in Figure 12. QPSK is equivalent to 4-QAM. See also: differential

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IEEE Wireless Dictionary

IEEE Wireless Dictionary

quadrature phase-shift keying (DQPSK), 71:/4 differential quadrature phase-shift keying (71:/4 DQPSK) and quadrature amplitude modulation (QAM) .

Figure 12:

•

•

•

•

Example constellation for QPSK modulation

quality of service (QoS): A measure of the timeliness and reliability of the delivery of data from a source to a destination. QoS is not a single measurement, but rather is combination of the latency, throughput, jitter, availability, reliability, etc. The QoS level that is acceptable depends greatly on the application and the user.36 Typical applications that require a high QoS are telephony, multimedia. and streaming audio. Different applications emphasize different requirements, e.g., telephony has relatively low throughput requirements, < 32 kb/s, but very stringent latency requirements, < 100 ms. Streaming video, on the other hand, has a high throughput requirement (> 20 Mb/s

J(,

It will also vary widely among engineers trying to define an adequate QoS for a system.

IEEE Wireless Dictionary

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IEEE Wireless Dictionary

for the highest resolution of compressed high-defmition television), but can have relatively relaxed latency requirements, < 5 s, depending on the buffering available at the destination. QoS is a measure of the end-to-end responsiveness and reliability of a link, and so it is only as good as the weakest link in the connection. quality of service access point (QAP): An IEEE 802.11 access point that implements the QoS functions defined in IEEE Std 802.11e. quality of service station (QSTA): An IEEE 802.11 station (STA) that implements the QoS functions defmed in IEEE Std 802.1 Ie. radio frequency (RF): Electromagnetic phenomena below approximately 1 THz; i.e., below the infrared frequencies, even though the underlining equations 37 are the same for both regions. It is also used to describe anything associated with the "dark art" of designing circuits and systems that are capable of handling RF signals. It is a very imprecise tenn as there are dramatic differences in the design and construction of systems that operate in the low MHz as opposed to those that operate at millimeter wave frequencies. radio frequency identification (RFID): Wireless technology that allows an object to be identified at a distance. The distance for RFlD can be a few inches to as much as a mile. Objects are identified by attaching an RFlD tag that

37

74

The equations referred to are the ones proposed by James Clerk Maxwell, as simplified by Oliver Hcavyside.

IEA'E Wireless Dictionary

iEEE Wireless Dictionary

contains the antenna, radio, memory, and sometimes a cpu. In addition to identifying the object to which the tag is attached, RFID systems usually are able to read infonnation from and write information to the tag. There are two classes of RFID tags: active and passive. A passive tag is powered by the energy in the received signal and does not have a battery. Active tags, on the other hand, have batteries, and typically have longer ranges and more capabilities. RFID tags typically are small, very low cost, and very low power.

RC4"': A widely used symmetric key stream cipher. Unlike block ciphers, which operate on blocks of data, a stream cipher operates on units of data as small as a bit or a byte. RC4 is used in IEEE Std 802.11-1999 and Wi-Fi protected access (WPA), however it is not recommended for use in new implementations. See also: advanced encryption standard (AES), IEEE 802.11 and Wi-Fi protected access (WPA). received signal strength indication (RSSI): An estimate of the power in a received signal. RSSI can be used in a variety of ways including; performing clear channel assessment, reporting signal strength to a user, adjusting the transmit power, and determining when to change the data rate in multirate systems. receive or receiver (RX): The common abbreviation used to mean either receive or receiver, depending on the context. This is sometimes represented as Rx. See also: transmit or transmitter (TX).

IEEP Wireless Dictionary

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IEEE TFireless Dictionary

reciprocal mixing: The process in which an interferer is mixed by the sidebands of the local oscillator (LO) into the intennediate frequency (IF) or baseband. While an ideal LO is a single sinusoidal tone, in practice, the LO changes frequency slightly over time, resulting in sidebands or phase noise. The effect of reciprocal mixing is calculated by integrating the LO phase noise over the bandwidth of the interfering signals at the frequency offset of the interferer and multiplying that power by the power of the interfering signals. For example, if the interfering signal is 200 kHz wide and its center is offset 2 MHz from the center of the desired signal, then the LO phase noise, nonnally measured in dBc/Hz, is integrated from 1.9 MHz to 2.1 MHz offset and is multiplied (adding in dB) by the power of the interfering signal. The result is the power level of the interfering signal that will be converted into the passband of the receiver, degrading the quality of the received signal. Remote Authentication Dial-in User Service (RADIUS): An Internet standard for authentication and authorization of remote users. As the name indicates, the protocol was originally used to perform access control for dial-up internet connections. RADIUS is one of the options for authentication and authorization in IEEE Std 802.lli.

resolution bandwidth: The integration bandwidth used in making a frequency domain measurement, typically specified in either kHz or MHz. This is usually used in connection with spectrum analyzers or devices that implement a measurement function similar to spectrum analyzers. In a classic spectrum analyzer design, the resolution bandwidth is the bandwidth of the IF filter. All of the power that is measured within the

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IEEE Wireless Dictiolla/~v

resolution bandwidth is displayed as if it occurred only at the center frequency.

request for comments (RFC): A set of numbered documents from the Internet Engineering Task Force (lETF) that provide information related to the Internet. While many of the RFCs describe protocols and standards for the internet, others are information only or provide introduction to new topics of research. roaming: A characteristic ofa wireless network in which a mobile unit is able to maintain connectivity as it moves from one wireless network segment to another. For mobile phones, roaming occurs when the user is in an area not serviced by their provider but is serviced by a different provider that has an roaming agreement with the user's provider. In IEEE 802.11, roaming occurs when a station (STA) moves from the coverage area of one AP to the coverage area of another AP. IEEE 802.11 roaming is equivalent to handover for mobile phones. See also: handover. root mean square (rms): A calculation in which the samples are first squared, then averaged (mean) and finally the square root of the result is returned. It is used as a measurement technique for AC voltage, current and power. In equation form, nns value of sen) is N

I Srms =

s(n)

n= 1

N

IEEE Wireless Dictionary

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IEEE Wireless Dictionarv

scattering parameters (S parameters): A method for modeling an N-port system with a matrix whose entries are the ratios of the incident and scattered voltage waves. S parameters are complex numbers and so are expressed in either in cartesian (real and imaginary) or in polar (angle and magnitude) format. The magnitude of an S parameter is often expressed in dB. Individual entries of the S-parameter matrix are designated as SiJ which is the ratio of the outward traveling voltage at port i relative to the voltage of the inward traveling wave at port). S parameters are commonly used for describing the characteristics ofRF devices. For a two-port device, the S parameters and their interpretation is given in Table 3. Table 3:

S parameters for two-port networks

S parameter

Definition

511

Input ret1ection coefficient

Input return loss

Forward transmission coefficient

Gain'

S12

Reverse transmission coefficient

Isolation

S22

Output ret1ection coefficient

Output return loss

S21

Other name

The magnitude of S21 directly relates to the gain only when the input and output are well matched. Otherwise, much of the power is either reflected back to the generator or is reflected back from the load.

second generation (2G): The group of mobile phone standards that followed the original analog mobile phones. All of the 20 standards were based on transmitting a digitized and

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compressed copy of voice instead of the analog version used in 10 systems. One of the big advantages of20 phones is improved battery life in standby mode due to the fact that the phones are able to spend more time with the radio turned off. 20 systems include cdmaOne (IS-95a), PDC, OSM, iDEN. and TDMA (TS-I36).

second and one-half generation (2.5G): Mobile phone standards that are more advanced than 20 but less than 30. The change from 20 to 30 results in faster data services such that 2.5038 standards have improved data capabilities and speeds while still providing digital voice services. 2.50 systems include CDMA2000® IX and GPRS.

segmentation and reassembly (SAR): In a network, the process of breaking up a packet into smaller pieces (segmentation) prior to transmitting and putting them back together (reassembly) after the pieces have been received. According to the open system interconnection (OS!) reference model, this process takes place in the transport layer (layer 4) but this process is sometimes supported at the medium access controller (MAC) level as well. The terms segmentation and reassembly are used for asynchronous transfer mode (ATM) while the terms fragmentation and defragmentation are used in transmit control protocol/internet protocol (TCP/IP).

shared wireless access protocol (SWAP): See HomeRF.

" Another reason for 2.SG is that the technology gap between 2G and 3G was so great that the vendors wanted to offer an intermediate solution to encourage the sale of new devices and services.

IEEE W'ireless Dictiol1G1:v

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IEEE Wireless Dictionary

short message service (SMS): A text messaging protocol defined in the Global System for Mobile Communication (GSM) standard which allows users to send up to 160 characters in a message 39 • SMS has become very popular and is a feature in all of the 3G standards. SMS messages are delivered on a best effort basis, i.e., there is no guarantee when or if the message will get through. signal to noise ratio (SNR): The root mean square (rms) power in the signal divided by the rms noise power. The SNR is usually expressed in dB. The higher the SNR of the received signal, the fewer errors occur and the higher the potential information rate in a channel. simplex: A communications system which allows only one-way communications. Wireless examples of simplex systems include frequency modulation (FM) radio and broadcast television. slave: In the context of wireless protocols, a device that is dependent on another device for control, usually called the master. The most common usage of this term is in connection with the Bluetooth® specification which describes a network with one master and multiple slaves. specific absorption rate (SAR): The rate at which radio frequency (RF) energy is absorbed by a unit mass of a human body when it is exposed to an electromagnetic field. SAR can

39

80

The message is actually a maximum of 140 bytes long, which allows 160 seven-bit characters, 140 eight-bit characters, or 70 two-byte characters, sllch as those used in Japan, Korea, and China.

IEEE Wireless Dictionmy

TEEE Wireless Dictionary

be averaged over the whole body or over a specific mass of tissue, for example 1 g. Various regulatOlY agencies, e.g., the Federal Communication Commission (FCC), have established SAR limits for electronic devices for safety reasons.

specification: A specification is a technical document generally developed by a group or company. It differs from a standard in that the process for developing the specification is not based on an open consensus process, rather it is typically developed in a closed forum not open to the public for comment.

spread spectrum: A communication system in which the bandwidth of the transmitted wavefonTI is greater than the minimum bandwidth required to transmit the information. Spread spectrum techniques can be used in conjunction with almost any modulation, including amplitude modulation (AM), frequency modulation (FM), phase modulation (PM), and quadrature amplitude modulation (QAM). There are a variety of ways to create spread spectrum signals including; direct-sequence spread spectrum (DSSS), frequency hopping spread spectrum (FHSS), time hopping, pulsed frequency modulation (FM) or chirp systems, and combinations of these methods (i.e., DSFHSS). Spread spectrum was initially used by the military because when it is properly designed it has two useful qualities, jamming resistance and low-probability of intercept eLPI). Because of this, spread spectrum systems are occasionally touted as being inherently secure, when, in fact, no such security is inherent in the system40 • The qualities of jamming resistance and LPI depend on the design of the spread spectrum system and are not measured as present or absent, but rather as

IEEE Wireless DictionGlY

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IEEE Wireless DictiollaJY

the level or protection they provide. See also: chirp modulation, direct sequence spread spectrum (DSSS), and frequency hopping spread spectrum (FHSS). spurious free dynamic range (SFDR): The ratio of the root mean square (nTIS) signal amplitude to the rms amplitude of the highest noise or spurious component (generally due to distortion). The SFDR may be expressed either in decibels relative to the carrier (dBc) when measured relative to the carrier or in dB full scale (dBFS) when measured relative to the full scale of a data converter. The SFDR is normally used as a figure of merit for data converters and for receivers. In a superheterodyne receiver, the SFDR has an ideal value of (2/3)(lTP3-MDS). In a zero intermediate frequency (ZTF) receiver, where second order intermodulation products are of issue, the SFDR has an ideal value of (1/2)(IIP2-MDS). standard: A document that describes a p0l1ion of the functionality of a device such that certain characteristics will be the same regardless of the entity that does the building and/or implementation. A standard is similar to a specification, with the key exception that it is an open-consensLls document

40

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An example of this lack of inherent security is IEEE Std 802.11. The original 802.11 had three physical layers (PHYs), FHSS, DSSS (both in the 2.4 GHz band) and infrared. Despite the fact that the only PHY s commercially deployed were spread spectrum (FHSS and DSSS), it is widely accepted that 802.11 is completely insecure when the encryption system, called wired equivalent privacy (WEP), is not used. Of course, it is only somewhat more secure with WEP enabled, but that is due to mistakes in the design of the security protocol, which appears to be fixed with IEEE Std 802.lli. The PHYs offer no security at all.

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IEEE Wireless Dictionary

developed and approved by a recognized standards body. Examples of standards bodies include the Institute of Electrical and Electronics Engineers, Inc. (IEEE), European Telecommunications Standards Institute (ETSI), Consumer Electronics Association (CEA), American National Standards Institute (ANSI), and the Internet Engineering Task Force (lETF).

station (STA): The name for the basic device in an 802.11 network. The standard defines it as any device that contains an 802.11 conformant medium access controller (MAC) and physical layer (PHY). Thus, every access point (AP) must contain a STA. However, the tenn is almost never applied in normal usage when referring to APs. See also: access point (AP), quality of service access point (QAP), quality of service station (QSTA). subscriber identity module (SIM): A smartcard llsed in Global System for Mobile Communication (GSM) mobile phones to securely identify the subscriber. In addition, the 81M card can contain other user infonnation such as their phone book and instant messages. In theory, a user should be able to switch carriers by simply putting a new SIM card in their phone. However, many carriers SIM lock the phones that they sell so that they cannot be used on other providers networks. The Iridium'" satellite phone system also llses 81M cards. See also: Global System for Mobile Communication (GSM).

super-heterodyne: Called super-het for short, it is a radio architecture in which the conversion between the baseband signal and the RF signal uses an IF. In a super-heterodyne receiver, the RF signal is down-converted first to a lower frequency, the IF, before being down-converted to baseband

IEEE Wireless Dictionary

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IEEE Wireless DictiollaJY

(Le., being detected). Note that this frequency conversion may be perfomled more than once, producing a double-conversion superheterodyne, triple-conversion super-heterodyne, etc. Super-heterodyne can be applied to both the transmitter and receiver architectures and a radio need not have the same transmit and receiver architectures. Many DECT phones used direct modulation for the transmitter and a super-heterodyne receiver. See also: direct conversion radio (DCR), homodyne, low intermediate frequency (LIF), very low intermediate frequency (VLIF) and zero intermediate frequency (ZIF). super high frequency (SHF): A frequency band that extends from 3 GHz to 30 GHz; see "Frequency bands" on page 2.

TDMA (IS-136): Although time division multiple access (TDMA) is a well-known acronym among communications engineers, it has also been applied to the IS-136 cellular phone standard. 41 This system tripled the capacity of the mobile phone system as compared with the Advanced Mobile Phone Service (AMPS) and improved the standby time for the mobile phones. The 1S-136 system uses the same 30 kHz frequency channels as AMPS, but divides the time on the air among three mobile phones. IS-136 only saw widespread deployment in the U.S. and was used in the 850 MHz and 1900 MHz bands. The

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Generally. the meaning of the term can be determined from the context. For example: "GSM is a TD MA system" refers to the fact that GSM uses distinct time slots for ditferent mobile devices. On the other hand "TDMA is being phased out in favor ofGSM" refers to two different standards, both of which use TDMA.

IEEE Wireless Dictionmy

IEEE TFireless Dictionary

IS-136 standard evolved from the IS-54 standard, also called D-AMPS, which specified operation only in the 850 MHz band. The systems are now being replaced with the Global System for Mobile Communication (GSM) and will likely follow the evolutionary path to General Packet Radio Service (GPRS) and enhanced data-rates for GSM evolution (EDGE). See also: enhanced data-rates for GSM evolution (EDGE), Global System for Mobile Communication (GSM). and time division multiple access (TDMA). Telecommunications Industries Association (TIA): An industry standards organization accredited by the American National Standards Institute (ANSI). TlA develops standards for a variety of areas in telecommunications, including fiber optics, wireless communications, networks, and satellite communications. temporal key integrity protocol (TKlP): An interim solution to fix problems with wired equivalent privacy (WEP). TKIP was developed to provide a security upgrade beyond WEP for the large installed base of wireless local area network (WLAN) products. It was designed to be able to be implemented with only a firmware upgrade. TKIP provides a number of improvements over WEP including: changing the key relatively often, ensuring that each device in the WLAN uses a different key stream. a stronger message integrity check, and the ability to detect and respond to attacks. See also: wired equivalent privacy (WEP) and Wi-Fi protected access (WPA).

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IEEE Wireless Dictionm:v

text messaging: A generic term for a protocol that sends short text messages to other devices. Generally, when this term is used, it means short message service (SMS), which is the text messaging service provided by GSM mobile phones. See also: short message service (SMS). third generation (3G): Digital mobile phone standards that also support data transmissions with high data rates. In addition to voice support, 3G standards also seek to provide enhanced multimedia capabilities as well as fast asynchronous data connectivity. Four 3G standards have been defined: enhanced data-rates for GSM evolution (EDGE)42, Universal Mobile Telecommunications System (UMTS) wideband code division multiple access (WCDMA), CDMA2000®, and time division synchronous CDMA (TD-SCDMA). third and one-half generation (3.5G): A tenn often used in conjunction with high speed downlink packet access (HSDPA) to indicate that its performance is much greater than that offered by 3G standards. Third Generation Partnership Project (3GPP): A collaboration among telecommunications standards bodies to develop and promote 3G standards for mobile communications. The current members of the partnership are the Association of Radio Industries and Business (ARIB), the China Communications Standards Association (CCSA), European Telecommunications Standards Institute (ETST), the

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Not everyone agrees that EDGE is a 3G technology. Some people will refer to it as 2.75G to differentiate it from the other 3G standards that have much higher possible data rates.

IEE'E Wireless Dictionary

IEEE Wireless Dictionary

Alliance for Telecommunications Industry Solutions (U.S.) (ATIS), the Telecommunications Teclmology Association (Korea) (TTA), and the Telecommunication Technology Committee (Japan) (TTC). third-order input intercept point (IIP3): The intercept point of the third-order intennodulation products and the desired signal of a device measured as a function of the input power. The HP) plus the gain ofthe device is equal to the OIP). Because the HP 3 of the system is finite, interferers that are outside of the receive channel can create in-band interference. In particular, if two signals are present at the input of a radio receiver at frequencies offset by foffset and 2*foffset' then the third order products produced by a finite lIP) will fall in the receive channel and may interfere with the desired signal. See also: nth-order intercept point (IP n) and third-order output intercept point (OIP 3). third-order output intercept point (OIP3): The intercept point of the third-order intennodulation product and the desired signal, see OIP n' The OIP 3 is used in detennining the performance requirements ofa radio system. Because the OIP) of the system is [mite, interferers that are outside of the receive channel can create in-band interference. In particular, if two signals are present at the input of a radio receiver at frequencies offset by foffset and 2*foffset. then the third-order products produced by a finite OIP) will fall in the receive channel and may interfere with the desired signal. See also: nth-order intercept point (IP n) and third-order input intercept point

(IIP3)'

IEEE FVireless Dictionmy

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IEEE Wireless Diclionary

time division duplex (TDD): A communication system in which a device transmits and receives during distinct time intervals. TDD systems are typically also half-duplex systems. See also: frequency division duplex (FDD), full-duplex, half-duplex, and simplex. time division multiple access (TDMA): A process of sharing a given frequency allocation by assigning distinct time periods to different users, as shown in Figure l3. The time allocated to a given device is generally referred to as a time slot while a larger unit oftime that contains multiple time slots is often called a frame, as illustrated in Figure 13. While the time slots in some TDMA protocols are of equal duration, it is not a requirement for this access method. Likewise, the arrangement of the time slots can change from tl'ame to frame. An advantage of using a TDMA protocol is that it allows the radio to be turned off for a significant fraction of the time, greatly extending the standby time of the device. Essentially all systems that use TDMA also use frequency division multiple access (FDMA) as part of their multiple access strategy. Some of the protocols that use TDMA are Global System for Mobile Communication (GSM), IS-136 and HiperLAN. See also: code division multiple access (CDMA) and frequency division multiple access (FDMA).

I1

I.

->

3 -> 2

2 I_

Time slot

1

4 -> 1

12 -> 1

I

3 -> 1

-j

Frame

I Time . .1

Key: n -> m - Device n sending data to Device m

Figure 13:

88

Example of a TDMA time allocation

IEEE Wireless Dictionary

IEEE Wireless Dictionary

time division multiplexing (TDM): A communication system in which different signals use distinct time periods for transmission. When mUltiple users are separated using different time periods, the system is said to be using TDMA. See also: code division multiple access (CDMA), frequency division multiple access (FDMA), frequency division multiplexing (FDM), and time division multiple access (TDMA). time division synchronous CDMA (TD-SCDMA): An alternate 3G standard developed by Siemens and the China Academy of Telecommunications Technology. TD-SCDMA is a time division duplex (TDD) system, i.e., the receiver and transmitter don't operate at the same time. In addition, TD-SCDMA operates in an unpaired spectrum, i.e., in allocations where separate transmit and receive frequencies have not been allocated. TD-SCDMA supports data rates of up to 2 Mb/s. total access communication system (TACS): The European version of advanced mobile phone service (AMPS). TACS has been replaced by Global System for Mobile Communication (GSM). See also: advanced mobile phone service (AMPS) and Global System for Mobile Communication (GSM). total harmonic distortion (THD): The ratio of the sum of the root mean square (rms) values of all of the hannonics to the nns value ofthe input signal. THD is typically expressed in decibels relative to the carrier (dBc) and larger negative numbers are better (lower power in the harmonics).

IEEE Wireless Dictiol1my

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IEEE Wireless Dictionary

transmit or transmitter (TX): The common abbreviation used to mean either transmit or transmitter, depending on the context. This is sometimes represented as Tx. See also: receive or receiver (RX).

tri-band: Although the mobile phone frequency allocation for the U.S. and Europe overlap for 900 MHz, the higher frequency bands do not. Thus, to build a phone that is capable of being used in the U.S. and Europe requires supporting three frequency bands, hence the tenn triband. Note that a tri-band phone may be only single mode, e.g., Global System for Mobile Communication (GSM), whereas there are multimode phones, e.g., analog, carrier sense multiple access (CDMA), and/or GSM, that support one, two, or three bands.

ultra high frequency (UHF): A frequency band that extends from 30 MHz to 300 MHz; see "Frequency bands" on page 2. ultra wide band, ultra-wide band or even ultra-wille-band (UWB): UWB is a qualitative description of a type of a radio system. Traditionally, UWB systems have been those with a fractional bandwidth greater than 20%43 or an occupied bandwidth greater than 250 MHz. These qualities are not universally accepted as being definitive and the Federal Communications Commission (FCC), in granting unlicensed spectrum for UWB devices, declared UWB to be systems with greater than 500 MHz bandwidth or a fractional bandwidth 43

90

Most radio systems use less than 1%. For example, IEEE 802.11g is about 0.7% (17 MHz at 2400 MHz). Narrowband Advanced Mobile Phone System (NAMPS) is about OJJOI % (10 kHz at 850 MHz).

IEEE Wireless Dictiol1wy

IEEE Wireless Dictiol1arv

greater than 20%. An alternate definition is that UWB systems use very short pulses to generate wide bandwidths. Under this definition, UWB systems can be described as carrier-less because the frequency content is determined by the pulse shape and not the frequency of a local oscillator used for up-conversion. However, few, if any of the currently proposed UWE systems meet the characteristics of being either short pulse and carrier-less. The FCC frequency allocation in the U.S. forbids intentional radiation below 3.1 GHz, so the current UWB systems up convert at the baseband signal to a radio frequency in the allocated band44 • Although some UWE systems do use short pulses, others use traditional modulation techniques [i.e., quadrature phase-shift keying (QPSK) and orthogonal fequency division multiplexing (OFDM)] at very high data rates. One of the advantages ofUWB systems is that the frequency allocation in the U.S. is huge (7.5 GHz of spectrum) at relatively low frequencies (which translates into better propagation characteristics). However, the FCC has strictly limited the power of these systems because they are overlapping with licensed users in their band. The low transmit power coupled with the high data rates proposed for these systems will severely limit the coverage range.

Universal Mobile Telecommunications System (UMTS): The 3G successor to Global System for Mobile

44

Some systems do this with the traditional local oscillator (LO) and up-mixer combination while some of the more aggressive system perform this up conversion digitally and use an extremely high-speed digital-to-analog converter (DAC) to generate the RF signal.

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Communication (OSM), it is sometimes referred to as 30SM. The Universal Mobile Telecommunications System (UMTS) is based on wideband code division multiple access (WCDMA) air interface supported by OSM infrastructure. UMTS is designed to provide data rates to up to 1.92 Mbls but typical data rates will be closer to 384 kb/s. Universal National Information Infrastructure (U-NIl): The name of four frequency bands allocated by the FCC in the U.S. for unlicensed use. The Universal National Information Infrastructure (U-NIl) bands are: 5.15-5.25 OHz with approximately 50 m W TX power for indoor use, 5.25-5.35 OHz and 5.47-5.725 OHz with a TX power limit of approximately 250 m W for indoor and outdoor use, and 5.725-5.825 OHz with a TX power limit of I W. Additional restrictions apply and are found in the U-Nll section of the part 15 rules, i.e., in 47 CFR 15.401-15.407.

UWB Forum: An industry alliance of companies created to support the IEEE 802.15.3a standard. The UWB Forum's goal is to promote interoperability among standards-based UWB products and to promote regulatory acceptance ofUWB worldwide. See also: ultra wideband (UWB) and WiMedia. voice frequency (VF): A frequency band that extends from 300 Hz to 3 kHz; see "Frequency bands" on page 2. very high frequency (VHF): A frequency band that extends from 30 MHz to 300 MHz; see "Frequency bands" on page 2.

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IEEE Wireless Dictionary

very low frequency (VLF): A frequency band that extends from 3 kHz to 30 kHz,;see "Frequency bands" on page 2. very low intermediate frequency (VLIF): A radio architecture in which the IF is equal to one-half of the symbol rate. See also: direct conversion radio (DCR), homodyne, low intermediate frequency (LIF), super-heterodyne and zero intermediate frequency (ZIF). very small aperture terminal (VSAT): A very small aperture tenninal is a satellite terminal that uses a relatively small antenna. In this instance, small means 0.8 to 2.4 m diameter dishes, which is small when compared with 10m sate Hite dishes. virtual private network (VPN): A generic name for protocols that allow secure communications over insecure networks by routing higher-layer protocols through a cryptographic tunnel. The goal of these protocols is to provide confidentiality (only authorized people can view the data), authentication (verifying the identity of the source) and message integrity (ensuring that the message has not been changed). There are a variety of protocols for implementing VPNs, but as with other security issues, it is significantly easier to construct protocols that seem secure but aren't, than it is to construct protocols that actually are secure. As with most security systems, even VPNs that are otherwise secure can fail due to layer 8 problems (see "OSI 7-layer protocol model" on page 4).

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war chalking: The act of marking Wi-Fi access points (APs), usually by drawing symbols on the sidewalk or building with chalk that indicate the security, ssm and data rate of the AP. See also: access point (AP) and war driving. war driving: Driving45 around a city with a computer, usually a laptop, searching for IEEE 802.11 access points (APs), paIiicularly ones that are open. War drivers wi II often use Global Positioning System (GPS) to track the location of the APs that are found, posting their location on a web site. Nonnally, war drivers do not attempt to connect to the APs, but rather simply note the location and relevant infonnation. The term war driving is derived from war dialing which has come to refer to dialing phone numbers to tind a modem with which to connect, usually to gain unauthorized access. wideband CDMA (WCDMA): A 30 air interface that expands the code division multiple access (CDMA) bandwidth from 1.25 MHz to 5 MHz and offers data rates of up to 384 kb/s for mobile terminals and up to 1.92 Mb/s for stationary terminals. See also: Universal Mobile Telecommunications System (UMTS). Wi-Fi'° multimedia (WMM): The naIlle given by the Wi-Fi Alliance for a subset ofIEEE Std 802.11 e that was introduced to bring quality of service (QoS) to the market before IEEE Std 802.11 e was finalized. Wi-Fi Multimedia (WMM) uses the prioritized access method [enhanced distributed channel access

'5

94

There is at least one documented occurrence of war-flying, where a person used an airplane to find IEEE 802.11 access points in the San Diego, CA, metropolitan area.

IEEE Wireless Dictionary

IEEE Wireless Dictionary

(EDCA)] ofIEEE Std 802.lIe. See also: enhanced distributed channel access (EDCA), HCF controlled channel access (HCCA) and wireless fidelity (Wi-Fi). Wi-Fi® multimedia scheduled access (WMM-SA): The Wi-Fi Alliance's name for the extension to Wi-Fi multimedia (WMM) to include hybrid coordination function (HCF) controlled channel access (HCCA). WMM-SA provides centrally-coordinated, contention-free access. It also provides features needed for demanding quality of service (QoS) applications such as voice and video. See also: enhanced distributed channel access (EDCA), HCF controlled channel access (HCCA) and wireless fidelity (Wi-Fi). Wi-Fi® protected access (WPA): The name assigned by the Wi-Fi Alliance to a security protocol for IEEE 802.11 wireless local area networks (WLANs) based on the work ofthe IEEE 802.IIi task group. The negative publicity associated with the poor security provided by wired equivalent privacy (WEP) convinced the Wi-Fi Alliance that a timely upgrade was required for IEEE 802.11 devices. Since the work in the IEEE 802.11 i task group was proceeding more slowly than desired 46 , at the request of the Alliance, the task group published an early draft of the standard for use by the Wi-Fi Alliance. This draft had improvements to the protocol, e.g., temporal key integrity

46

IEEE Std 802.11 i was originally part of the IEEE 802.11 e project, which was moving even more slowly at the time. IEEE 802.lle was initially approved as an IEEE 802 project in March 2000 and IEEE 802.11 i was splil off in June, 200 I. 1EEE Std 802.11 i was approved as a standard in June 2004 while IEEE Std 802.11 e was approved in September 2005.

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protocol (TKIP), but maintained the RC4 encryption algorithm in order to minimize hardware changes. WPA provides a significant improvement in the security of S02.I1 systems over WEP but is not as secure as WPA2/S02.11 i47. See also: wired equivalent privacy (WEP) and Wi-Fi protected access 2 (WPA2).

Wi-Fi@ Protected Access 2 (WPA2): The name given by the Wi-Fi Alliance to the security protocol in IEEE Std 802.IIi. This standard is intended to replace WEP with a significantly more secure system. Wi-Fi Protected Access 2 (WPA2)/IEEE Std S02.I1 i includes all of the aspects of WPA but provides new encryption and authentication methods. In addition to RC4, WPA2/IEEE Std S02.IIi also provides a much stronger symmetric key encryption method, 128-bit advanced encryption system (AES). See also: wired equivalent privacy (WEP) and Wi-Fi protected access (WPA).

WiMax''': An industry organization developed to promote IEEE Std 802. 16 and IEEE Std 802.16e Because IEEE S02.16 has a cafeteria approach to creating a standard (there are multiple, incompatible PHYs), WiMax is certitying products that conform to a certain subset of the standard. WiMax is also developing profiles to ensure application level compatibility among certified devices. Th '

T

".

WiMedia"': Originally formed to promote IEEE Std 802.15.3 and its amendments, this organization no longer supports any "' At least it appears to be more secure. Security is a dynamic field and techniques once thought to be very secure can be found to have attacks that significantly reduce the security.

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IEEE Wireless Dictionary

IEEE standards and instead has adopted a medium access controller (MAC) and physical layer (PRY) specification originally developed by the multiband OFDM Alliance, which has since merged with WiMedia.

wired equivalent privacy (WEP): The name for the original security system used in IEEE 802.11. The goal of WEP was to provide a level of security roughly equal to what could be expected in a wired connection. Unfortunately, WEP became infamous because it was found to have major deficiencies in security, allowing an attacker to gain the secret keys in less than an hour of passive scanning. See also: temporal key integrity protocol (TKIP) and Wi-Fi protected access (WPA).

wireless application protocol (WAP): A specification for providing secure access to the internet and e-mail for mobile phones. Because the connection to the mobile phone is relatively slow and the displays are small, a WAP gateway reformats the web page before it is delivered. WAP includes a reduced set of HTML, called wireless markup language (WML). WAP has been criticized because the protocol requires that the WAP gateway decrypts the traffic and reencrypts for transport over wired medium. This creates a potential security vulnerability in the WAP gateway where the data is unencrypted.

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Wireless Ethernet Compatibility Alliance (WECA): The original name for the Wi-Fi Alliance™48. When the name of the organization changed in October 2002, the alliance had already been certifying products under the Wi-Fi® brand name. The name change reflected the acceptance in the market of the Wi-Fi brand name.

wireless fidelity (Wi-Fi'): The brand name for IEEE 802.11a, IEEE 802.11 b and/or IEEE 802.1lg products that have passed the Wi-Fi Alliance's certification procedure. Marketing of standards and certification of solutions is not allowed in the IEEE standards process, so industry alliances are formed to do these tasks. Because the IEEE owns the trademark to the IEEE 802 family of standards, an outside organization needs to create a new name that can be trademarked and applied only to products that meet certiflcation. Based on the success ofWi-Fi, other IEEE 802 wireless standards have adopted similar names, e.g., WiMax'" and WiMedia™49,

wireless local area network (WLAN): A wireless network that covers an area equivalent to a building or even a campus. While this is a generic term, the WLAN name has increasingly become synonymous with the IEEE 802.11 family of standards, particularly IEEE Std 802.11 a, IEEE Std 802.11 b,

48

49

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The IEEE 802.11 standard was initially seen as a wireless version of ethernet, hence the name. The manufacturers ofIEEE 802.15.4 devices inexplicably chose the name of ZigBee'". Possibly, it is an attempt to prove that the name of the technology is not nearly as important as the quality of the technology.

IEt"E Wireless Dictionary

IEEE Wireless Dictionary

and IEEE Std 802.llg. See also: local area network (LAN), metropolitan area network (MAN) personal area network (PAN), wireless metropolitan area network (WMAN), and wireless personal area network (WPAN).

wireless metropolitan area network (WMAN): A wireless network designed to operate over a range that a city or portions of a city. See also: local area network (LAN), metropolitan area network (MAN) personal area network (PAN), wireless metropolitan area network (WMAN), and wireless personal area network (WPAN).

wireless personal area network (WPAN): A wireless network that covers a person and their immediate surroundings. While the definition of WPAN initially included a restriction on the range to less than 10 m, all of the published IEEE 802.15 WPAN standards with physical layers (PHYs), i.e., IEEE Std 802.15.1, IEEE Std 802.15.3 and IEEE Std 802.15.4, operate at ranges well in excess of 10m, providing a coverage area roughly equivalent to the IEEE 802.11 wireless local area networks (WLANs). Currently, the key difference between the WLAN and WPAN standards is that WLANs are generally formed to connect to other networks to enable world-wide connectivity via the internet. On the other hand, WPAN networks are often complete in themselves, connecting devices owned and controlled by a single person and don't require connections to outside networks.

wireless transport layer security (WTLS): A security protocol based on transport layer security (TLS) which is in turn, based on secure socket layers (SSL). WTLS is

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specifically designed to provide privacy for wireless networks using WAP. See also: wireless application protocol (WAP).

zero intermediate frequency (ZIF): ZIF is a radio architecture in which receiver or transmitter coverts directly between the baseband signal and the RF signal. ZIF is a bit of a misnomer because these systems do not have an intermediate frequency. This type of radio architecture is referred to as direct conversion or direct conversion radio (DCR). Infrequently, the tenn homodyne will be used to refer to this architecture. See also: direct conversion receiver (DCR), homodyne, low intermediate frequency (LIF), super heterodyne and very low intermediate frequency (VLIF). ZigBee'M: The ZigBee Alliance was fonned to promote IEEE Std 802.15.4, provide conformance testing, and improve interoperability among devices from different manufacturers. Although the ZigBee specification is based on IEEE Std 802.15.4, it does not exactly follow every part of the standard and it adds a great deal more to the standard in the form of profiles and requirements for higher layers in the networking stack. The goal of IEEE Std 802.15.4 and the ZigBee Alliance is to provide wireless solutions that are low-cost, low data-rate, and low power. The target applications are control and monitoring systems that only infrequently send small amounts of data.

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ACRONYMS AND ABBREVIATIONS

The following acronyms and abbreviations are used in this book:

1G 2G 2.5G

30 3.5G 4G 8DPSK 8PSK ACIPR ACPR ADC AES

AM AMPS ANSI AP ARIB

ARP ATM BER CBR CCA CCK CDMA CDPD CEA

first generation second generation second and one half generation third generation third and one half generation fourth generation 8 differential phase-shift keying 8 phase-shift keying adjacent channel interference protection ratio adjacent channel power ratio analog to digital converter advanced encryption system amplitude modulation Advanced Mobile Phone Service American National Standards Institute access point Association of Radio Industries and Business address resolution protocol asynchronous transfer mode bit enor ratio constant bit rate clear channel assessment complimentm)' code keying code division mUltiple access cellular digital packet data Consumer Electronics Association

IEEE "Vireless DiclionalY

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IEEE Wireless Dictionary

CPE CRC CSMA/CA CSMA/CD DAC dB dBc dBd dBFS dBi dBm dBW DHCP DNL DSSS DQPSK EAP ECC EDCA EDGE EHF EIA ELF FCC FDD FDMA FEC FHSS

102

customer premises equipment cyclic redundancy check carrier sense mUltiple access/collision avoidance carrier sense multiple access/collision detection digital-to-analog converter decibel decibels relative to the carrier decibels relative to the dipole decibels relative to full-scale decibels relative to an isotropic radiator decibels relative to a milliwatt decibels relative to a watt dynamic host configuration protocol differential nonlinearity direct-sequence spread spectrum differential quadrature phase-shift keying extensible authentication protocol Electronic Communications Community enhanced distributed channel access enhanced data-rates for GSM evolution extremely high frequency Electronics Industries Alliance extremely low frequency Federal Communications Commission frequency division duplex frequency division multiple access forward error correction frequency hopping spread spectrum

IEEE Wireless Dictionary

IEEH Wireless Dictionary

FM FSK OFSK OMSK GPRS OPS OSM HiperLAN iDEN IEEE ETF IF INL IP ISO ITU LAN LF LLC LMSC LO LOS LSB MAC MAN MF MIMO MSB

frequency modulation frequency shift keying Gaussian frequency shift keying Gaussian minimum-shift keying General Packet Radio Service Global Positioning System Global System for Mobile Communication high-perfOlmance LAN Integrated Digital Enhanced Network Institute of Electrical and Electronics Engineers, Inc. Internet Engineering Task Force intermediate frequency integral nonlinearity internet protocol International Organization for Standardization International Telecommunications Union local area network low frequency logical link controller LAN/MAN Standards Committee local oscillator line of sight least significant bit medium access controller metropolitan area network medium frequency multiple input, multiple output most significant bit

IEEE Wireless DictionQlY

!03

IEEE Wireless Dictionary

MSK NAMPS NAT NLOS NMT NTIA OFDM OOK OSI PAN PCS PDA PDC PER PHS PHY PM PNC POTS PSK nl4 DQPSK

nl4 QPSK PTT QAM QAP QoS QPSK

104

minimum-shift keying Narrowband Advanced Mobile Phone Service network address translation non-line of sight Nordic Mobile Telephone National Telecommunications and Information Administration orthogonal frequency division multiplexing on-off keying open systems interconnection personal area network personal communications system personal digital assistant personal digital cellular packet error ratio personal handyphone system physical layer phase modulation piconet controller plain old telephone system phase-shift keying nl4 differential quadrature phase-shift keying nl4 quadrature phase-shift keying push to talk quadrature amplitude modulation quality of service access point quality of service quadrature phase-shift keying

IEEE Wireless Dictio/1my

IEEE Wireless Dictionary

QSTA RADIUS RF RFC RFID nns RSSI SFDR SHF SMS SNR SPS STA SWAP TACS TCP/IP TDD TDM TDMA TD-SCDMA THD TIA TKIP UHF UMTS U-NII UWB VF

quality of service station Remote Authentication Dial-in User Service radio frequency request for comments radio frequency identification root mean square receiver signal strength indication spurious free dynamic range super high frequency short message service signal-to-noise ratio synchronized power save station shared wireless access protocol total access communication system transmit control protocol/internet protocol time division duplex time division multiplexing time division multiple access time division synchronous CDMA total hannonic distribution Telecommunications Industries Association temporal key integrity protocol ultra high frequency Universal Mobile Telecommunications System Universal National Information In frastructure ultra-wideband voice frequency

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VUF

VPN VSAT

WAP WEP Wi-Fi

WLAN WMAN WMM WPA

WPAN WTLS ZIF

106

very low intermediate frequency virtual private network very small aperture tenninal wireless application protocol wired equivalent privacy wireless fidelity wireless local area network wireless metropolitan area network Wi-Fi multimedia Wi-Fi® protected access wireless personal area network Wireless TranspOJi Layer Security zero intermediate frequency

IL"EE Wireless Dictionary

IEEE

~Vireless

Dictionary

BIBLIOGRAPHY lEEE Std 802.11 TM, (Second Edition, 2005) IEEE Standard for Local and Metropolitan Area Networks-Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) And Physical Layer (PHY) Specifications. 50 IEEE Std 802.11a™-1999, IEEE Standard for Local and Metropolitan Area Networks-Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 1: High-speed Physical Layer in the 5 GHz Band. IEEE Std 802.11 b'''-1999. IEEE Standard for Local and Metropolitan Area Networks-Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 2: Higher-speed Physical Layer Extension in the 2.4 GHz Band: Corrigendum 1. IEEE Std 802.l1d"'-2001, Local And Metropolitan Area Networks-Specific Requirements Part 11: Wireless Lan Medium Access Control (MAC) And Physical Layer (PHY) Specifications Amendment 3: Specification for Operation in Additional Regulatory Domains.

'u

IEEE publications are available from the IEEE. 445 Hoes Lane. P.O. Box 1331. Piscataway. NJ 08855-1331, USA (http://www.standards .ieee.org/).

IEEE Wireless Dictionary

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iEEE Wireless DictionalY

IEEE Std 802.ll el>I_2005, IEEE Standard for Information Technology-Telecommunications and Information Exchange Between Systems-LAN/MAN Specific Requirements--Part 11 Wireless Medium Access Control (MAC) and Physical Layer (PHY) specifications: Medium Access Control (MAC) Quality of Service (QoS) Enhancements. IEEE Std 802.11F" -2003, IEEE Trial-Use Recommended M

Practice for Multi-vendor Access Point Interoperability via an Inter-access Point Protocol Across Distribution Systems Supporting IEEE 802.11 Operation. IEEE Std 802.1Ig" -2003, IEEE Standard for Local and M

Metropolitan Area Networks-Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 4: Further Higher Data Rate Extension in the 2.4 GHz Band. IEEE Std 802.11h'M-2003 , IEEE Standard for Local and Metropolitan Area Networks-Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) And Physical Layer (PHY) Specifications Amendment 5: Spectrum and Transmit Power Management Extensions in the 5 GHz Band in Europe. IEEE Std 802.lliT>I_2004, IEEE Standard for Local and Metropolitan Area Networks-Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 6: Medium Access Control (MAC) Security Enhancements.

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iEEE Wireless Dictional),

IEEE Wireless Dictionary

IEEE Std 802.11j'"-2004, IEEE Standard for Local and Metropolitan Area Networks-Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 7: 4.9 GHz-5 GHz Operation In Japan. IEEE Std 802.15. 1'M-2005, IEEE Standard for Information Techno logy-Telecommunications and Information Exchange Between Systems- Local and Metropolitan Area NetworksSpecific Requirements Pm115.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications For Wireless Personal Area Networks (WPANs). IEEE Std 802.15.2"'-2003, IEEE Standard for Information Technology-Telecomlllunications mId Infonnation Exchange Between Systems-Local and Metropolitan Area NetworksSpecific Requirements Part 15.2: Coexistence of Wireless Personal Area Networks with Other Wireless Devices. IEEE Std 802.15.3"'·2003, IEEE Standard for Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for High Rate Wireless Personal Area Networks (WPAN). IEEE Std 802.15.4"'-2003, IEEE Standard for Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (LR-WPANs).

IEEE Wireless Dictiolll1l:v

]09

IEEE Wireless Dictionary

ISO 9660, Infonnation Processing-Volume and File Structure of CD-ROM for Information Interchange. ISO/IEC 7498, Information Technology-Open Systems Interconnection-Basic Reference Model-The Basic Model. ISO/IEC 8802-11, Information Techno logy-Telecommunications and Infonnation Exchange Between Systems-Local and Metropolitan Area Networks-Specific Requirements-Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PRY) Specifications. RFC 2131, Dynamic Host Configuration Protocol.

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IEEE Wireless Dictionary

More Titles in the IEEE Standards Wireless Networks Series

Wireless COllllllunication Standards: A Study of IEEE 802. JJ '", 802. 15'M, and S02.16™ by Dr. Todor Cooklev is the only IEEE book of its kind that covers all of the current 802 wireless standards.*

Wireless Multimedia: A Guide to the IEEE 802.15.3'" Standard by Dr. James P.K. Gilb clarifies the standard for individuals who are implementing compliant devices and shows how the standard can be used to develop wireless multimedia applications. *

* The authors of these books are also teaching courses based on IEEE wireless standards. For information, please visit: http://doceotech.com/. Doceotech trains engineers in Wireless, VolP and RPID Standards.

The IEEE 802.1 J '" Handbook: A Designer s Companion (Second Edition).This new edition now covers IEEE 802.lld. IEEE P802.lIe. 802.IIF. 802.11g, 802.] Ih, 802. IIi, 802.11j. 802.lIn. and more!

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More Titles in the IEEE Standards Wireless Networks Series

Low-Rate Wireless Personal Area Networks: Enabling Wireless Sensors with IEEE 802.i5.-I'" is an excellent companion to the standard for those interested in the Held of "simple" wireless connectivity with a further focus on wireless sensors and actuators for the industry in general.

Coming in 2006 .... WirelessMAN: inside the IEEE 802.16 Standard/or Wireless Metropolitan Area Networks

Please visit http://standards.ieee.org/standardspress/

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iEEE Wireless Dictiollmy

The IEEE Wireless Dictionary Wireless technology, like many other technical fields, has its own set of jargon and acronyms. The goal of this book is to provide meaning for the most commonly used terms in the wireless industry, with a particular emphasis on commercial systems. Individuals who are experts in one particular field, e.g., third generation (3G) cellular or Wireless Local Area Networks (WLANs), will find terms from other fields with which they are unfamiliar. This book is a dictionary that reads more like an encyclopedia. Rather than just giving a terse definition for various wireless terms, many of the definitions contain additional information to provide context for understanding the term. A little history is added where appropriate, as well as some opinion regarding the technical and marketing issues that make the design of wireless systems so interesting. The IEEE Wireless Dictionary is the perfect companion to the other books in the IEEE Standards Wireless Networks Series, which includes: The IEEE 802.11™ Handbook, Second Edition; Wireless Communication Standards: A Study of IEEE 802.11™, IEEE 802.15™, and IEEE 802.16™; Wireless Multimedia: A Guide to the IEEE 802.15.3™ Standard; Low-Rate Personal Area Networks: Enabling Wireless Sensors with IEEE 802.15.4™; All 802® wireless standards (IEEE 802.11, IEEE 802.15, IEEE 802.16). Look for other books in the series at:

http://standards.ieee.org/StandardsPress