A statistical approach to the analysis of DS/CDMA cellular systems employing RAKE receivers and sectorized antennas

RAKE receivers and sectorized antennas are used in direct-sequence/code-div ision multiple-access (DS/CDMA) cellular systems to improve the system perf ormance, This paper presents a statistical method for analyzing the perform ance of DS/CDMA cellular radio systems employing RAKE receivers and sectori zed antennas, Average bit error rates in the system are estimated consideri ng the multipath fading effects of the environment. (The fast fading is ass umed to be Rayleigh distributed, and the distance-dependent means of the mu ltipath components have an exponential power delay profile.) The analysis o f RAKE receivers quantifies the performance improvement that could be achie ved by increasing the number of RAKE fingers. Sectorized antennas improve the system performance by reducing the interfer ence at the receiver, In a perfectly sectorized system, assuming three sect ors per cell, the capacity of the system can be improved by a factor of thr ee. However, due to the imperfection in practical antennas, it is not possi ble to achieve this improvement. In this paper, the performance of systems employing practical sectorized antennas (with finite front-to-back ratios a nd overlapping sectors) is compared with the performance of perfectly secto rized systems. The analysis shows that the incremental performance improvement diminishes with each incremental increase in the number of RAKE fingers. Performance d egradation due to finite front-to-back ratio is shown to be insignificant f or practical values of the front-to-bark ratio of sectorized antennas, Howe ver, the reliability of mobile reception can be degraded significantly in a reas where adjacent sectors overlap.