Iterative MMSE multiuser interference suppression for coded dispersive CDMA wireless channels with multisensor receivers

A soft iterative multisensor array receiver for coded dispersive multiuser code division multiple access (CDMA) wireless uplink channels is proposed. The proposed scheme suppresses multiuser interference over a wide range of user signal powers, by iteratively exchanging soft information between a minimum mean square error (MMSE) multiuser demodulator and a bank of single-user decoders, feeding back the outputs of the latter to aid in soft multiuser multisensor MMSE-RAKE demodulation and subtractive interference cancellation. It displays remarkable near-far resistance, since it functions like a successive interference subtracter across iterations. The array responses are also obtained using soft-decoded feedback estimates and (temporal) pilot symbols, seeking neither to rely on the array geometry nor to estimate the directions from which users´ signals arrive at the receiver. Simulation studies indicate that this scheme performs remarkably close to the single-user case with a two-sensor receiver array, and perfect channel state information, after four iterations; alternatively, it allows significant overload capability compared with conventional receivers, and suffers only a modest loss with estimated array responses.