Transmit-receive antenna diversity and turbo multiuser detection

Antenna diversity and turbo multiuser detection are two promising techniques for combating channel impairments and multiple-access interference. In this paper, we propose a novel scheme for a turbo coded system with both transmit and receive antenna diversity that employs iterative multiuser detection and decoding. Multiuser detection is embedded into single-user turbo decoding. After each turbo decoding iteration, the extrinsic information of the interfering users is passed to the multiuser detector, and after each multiuser iteration, updated a posteriori probabilities are passed to the single-user turbo decoders as the soft input metrics. The proposed scheme achieves excellent performance, about 1.8 [dB] away from multiuser capacity for multiple antennas. It is shown that depending on the channel characteristics, for a fixed spectral efficiency, that is for a fixed number of virtual users K_v=KT_x, there exists a trade-off between the number of active users K and the number of transmit antennas T_x.