Small delay multipath diversity in spread spectrum communication systems

A new double-filter receiver for spread spectrum wireless systems is presented. The receiver exploits the inherent diversity due to the small delay difference between the multipaths which may not be exploited by the conventional RAKE receiver. The bit error rate performances of both the coherent and the noncoherent detectors are analyzed and compared with the ideal RAKE receiver and the matched filter bound. We also examine the best and the worst cases of a three-path fading channel for the proposed receiver. Optimum pulse shapes under various channel conditions are designed. Implementation issues in code-division multiple access systems are discussed. The numerical results show that the proposed receiver achieves significant gains for a given spreading factor under a complexity constraint.