A simple 2-user multiple access technique using fading signatures and space diversity

In this paper, a simple 2-user multiple access technique using the same available resources without subdivision in orthogonal dimensions (time, frequency, space or orthogonal codes) is proposed. It utilizes the difference in users´ fading channels and space diversity to recover the individual user´s data in a joint manner using minimum Euclidian distance detection. The effects of channel correlation (p), number of receive antennas and constellation points are investigated. System bit error rate (BER) performance is presented and shown to achieve the single user BPSK bound for uncorrelated channels (p=0). It is also shown that constellation rearrangement of the transmitted signal using different techniques improves the system performance by resolving signals ambiguity at the receiver. Using orthogonal constellation rotation between equal power BPSK users, this technique with single receive antenna achieves the single user BPSK for any p.