A new channel filter for CDMA systems in multipath delay and fading environments

Direct-sequence spread-spectrum (DS/SS) receivers are based generally on correlation techniques, such as the matched filter (MF). These methods are optimal for the despreading of the PN code in the presence of Gaussian noise. In the multipath propagation environment, this processing gain is insufficient to reject effectively cochannel and multipath delay interference. This restricts the performance of the acquisition system and hence, of the receiver. Cancellation techniques can be used before acquisition, but this does not provide significant improvement in the case of the multipath delay and fading environment. A new channel filter to be used before the acquisition system is proposed to overcome the multi-user and multi-path delay interference. A simulator is used to evaluate and compare the performance in terms of multiple users and multi-path delay both with and without proposed channel filter. Details of the system configuration, the design concept of the proposed new channel filter and the simulation technique are discussed. The results show that the proposed new technique can significantly improve the overall system performance