A practical RAKE combining scheme for synchronous CDMA systems

In this paper we consider the performance of a RAKE receiver in a code division multiple access (CDMA) system employing maximal-ratio combining. A simple select and combine algorithm is introduced in which the RAKE receiver combines only the synchronization path and those resolvable paths with a signal-to-noise ratio (SNR) larger than a given threshold. We analyze its performance based on moment generating functions of the SNR of the combined signal. We study the cases with equal and unequal average SNR for different diversity paths. In particular, closed-form expressions for the average combined SNR and symbol error probability with the proposed RAKE receiver over block fading channels are derived. We also study the outage probability of the system and the number of channels estimated. Numerical results are given to illustrate the analytical results.