Performance of orthogonal multi-carrier CDMA with DPSK modulation and differential detection in a fading multi-path channel

Multi-carrier direct sequence code-division multiple-access (DS-CDMA) with differential phase shift keying (DPSK) modulation is proposed. Transmitted data bits are differentially encoded before being serial to parallel converted to a number of parallel streams. On each stream each encoded bit is direct sequence spread spectrum (DS-SS) modulated and transmitted using orthogonal carriers. The system is analyzed with a differential detector for a static Rayleigh fading multipath channel. The performance is compared to that of the (PSK) conventional matched filter (CMF) receiver. It is shown that, for the static fading channel, the performance of the differential detector is akin to a (CMF) receiver especially for a small number of identical-bit carriers and small signal-to-noise ratio (SNR). (DPSK) with a differential detector has the advantage of simpler implementation than (PSK) with (CMF) since the exact frequency and phase of the carrier are not required in the differential detector.