Abstract:In this paper, a spectrum-efficient differential space-time transmission scheme is presented for Code-Division Multiple-Access (CDMA) systems. Consider a multiuser environment with M synchronous co-channel users, each is equipped with 2 transmit antennas. Assuming the receiver uses N>2 receive antennas, this scheme will exploit decorrelating detectors and receive antenna diversity to separate M users. Then a noncoherent decoder is derived for flat Rayieigh fading channels, which can provide a minimum diversity order of 2x(jV-1) to each co-channel user. Compared with the existing differential space-time coded CDMA systems, the proposed scheme has two main advantages: Firstly, only by deploying an additional receive antenna, it can effectively improve the system performance under the condition that the spectrum efficiency is increased by 1/3; secondly, it has only linear decoding complexity.