Nonlinear Chip-Level Multiuser Transmission for TDD-CDMA with frequency-selective MIMO channels

Multiuser Transmission (MUT), the counterpart of Multiuser Detection (MUD) in the transmitter, can substantially enhance the performance of the CDMA downlink in frequency-selective channels. Besides linear Multiuser Transmission, known as Joint Transmission and Transmit Wiener filters, recently nonlinear MUT was proposed. The contribution of this paper is the extension of nonlinear Minimum BER Transmission from the symbol-level to the more general chip-level. A phase-only nonlinear MUT scheme is proposed, which requires considerably less computational complexity. The linear and nonlinear multiple antennae MUT schemes are compared for different receiver configurations and for the application of multiple antennas both in the transmitter and in the receiver. The simulation environment is similar to 3GPP TDD CDMA or the Chinese TD-SCDMA.