BER performance of the RAKE receiver in a realistic mobile radio channel

The performance of an ideal RAKE receiver, which exploits time/frequency diversity, is no different than the performance of an L branch space diversity receiver as shown by Proakis (see Digital Communications, McGraw Hill Book Co., 3rd edition, p.772-806, 1995). Therefore, the expressions for average probability of error for space diversity systems can be used as a starting point for RAKE performance. This paper extends this analysis to incorporate the effects of random path arrival on RAKE BER performance assuming the path arrival may be modeled as a modified (doubly stochastic) Poisson process as was suggested by Turin et. al. (1972) and by Suzuki (1977). The analysis results in a new measure for diversity which is the average number of paths for a given length of the power delay profile. As average number of paths (the Poisson parameter) is not necessarily an integer number, the notion of order of diversity, which is generally described in integer numbers, can be extended to fractional diversity for realistic channels