Performance enhancement through joint detection of cochannel signals using diversity arrays

TLDR

Joint detection exploits channel differences among users to distinguish cochannel signals without relying on spectrum spreading. The study seeks to analytically bound the average symbol‑error rate for joint detection with diversity antennas in fading environments and to benchmark it against MMSE combining. It derives a union‑bound expression for arbitrary numbers of users and antennas under both perfect and imperfect CSI and compares the resulting performance analytically. Joint detection achieves remarkable performance, incurring only a 2‑dB penalty per additional user under perfect CSI, tolerating inaccurate channel estimation, supporting more users than antennas with slow degradation, and outperforming MMSE combining by orders of magnitude.

Abstract

Joint detection based on exploiting differences among the channels employed by several users allows a receiver to distinguish cochannel signals without reliance on spectrum spreading. This paper makes a number of new contributions to the topic; it provides an analytical expression for the union bound on the average symbol-error rate for an arbitrary number of users and diversity antennas in a fading environment, for both perfect and imperfect channel state information (CSI), and it compares the performance of joint detection with diversity antennas against classical minimum-mean-square-error (MMSE) combining. The performance is remarkable. With accurate CSI, several users can experience good performance with only a single antenna; moreover, for perfect CSI, only a 2-dB penalty is incurred for each additional user. With several antennas, many more users than the number of antennas may be supported with a slow degradation in performance for each additional user. Furthermore, high accuracy is not required from the channel estimation process. In all cases, the performance of joint detection exceeds that of MMSE combining by orders of magnitude.