High-performance MIMO receivers based on multi-stage partial parallel interference cancellation

Turbo-encoded multiple-input multiple-output (MIMO) radio links have recently been proposed for the support of high-speed downlink packet access (HSDPA) in UMTS, where the re-use of spreading codes across the transmitter antennas results in high levels of interference. The state-of-the-art receiver chain for such a link incorporates space-time channel equalization, de-spreading, pre-whitening and finally a posteriori probability (APP) detection. A multi-stage partial parallel interference canceller (MS-PPIC) is considered as a low complexity alternative to the APP detector and its max-log variant. Nonlinear cancellation metrics are derived for the MS-PPIC and its performance is compared with the APP detector for flat and dispersive channels. It is shown that the MS-PPIC can provide similar performance compared to APP and, for low coding rates, superior performance compared to max-log-APP, at a substantially lower computational complexity.