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d\ then LOS is assumed (figure 6.24) and the position (XMT, VMT] of the MT is simply estimated as
Fig. 6.23 Sample of a polar representation of the sentinel function p(a) for a typical urban scenario. Source: M. Porretta, P. Nepa, G. Manara, F. Giannetti, M. Dohler, B. Allen, A. H. Aghvami, A Novel Single Base Station Location Technique for Microcellular Wireless Networks: Description and Validation by a Deterministic Propagation Model, IEEE Trans. Veh. Tech., Vol 53, No 5, pp 1553-1560, Sept, 2004 © IEEE.
Therefore, when the MT is supposed to be in LOS, only the parameters relevant to the first MFC (Q;I, TI) are used in the location estimation. It is worth mentioning that the solution given by equation (6.19) is the basic 1—ToA/ 1—AoA single BS hybrid positioning algorithm . However, such a scheme is used by the proposed location technique only if the MT is supposed to be in LOS with the BS. Cost function minimisation in NLOS conditions If the above mentioned test, (f(a) > di, fails, then the NLOS condition is assumed (figure 6.25). In this case, the MT position is determined by minimising a given cost function. First, the algorithm evaluates the coordinates of the scatterers found along the angle of arrival for the first N MFCs, namely xs = [ Zai, £S2, • • • xsN } and ys = [ ysi, y s2 , ••• VsN ]• These scatterers are
ANTENNA ARRAYS FOR WIRELESS COMMUNICATIONS
Fig. 6.24 If the mobile terminal (MT) and the BS are in LOS, then p(cti) > d\. Source: M. Porretta, P. Nepa, G. Manara, F. Giannetti, M. Dohler, B. Allen, A. H. Aghvami, A Novel Single Base Station Location Technique for Microcellular Wireless Networks: Description and Validation by a Deterministic Propagation Model, IEEE Trans. Veh. Tech., Vol 53, No 5, pp 1553-1560, Sept, 2004 © IEEE.
the points where the ray related to each MFC has been reflected or diffracted for the last time before reaching the BS; consequently, their coordinates are obtained as:
After the identification of the scatterer positions, the algorithm computes the vector rs = [ TR, TR2, • • • TEN ] containing the propagation delays from the MT to the scatterers:
Fig. 6.25 If the mobile terminal MT and the BS are in NLOS, then