Low Complexity Iterative Receiver based on Successive Cancellation for MIMO

Turbo-encoded multiple-input multiple-output (MIMO) systems have recently been proposed for the support of high-speed downlink packet access (HSDPA) in UNTS, where the re-use of spreading codes across the transmitter antennas results in high levels of interference. The state of the art receiver for this system incorporates a channel equalizer, followed by an a posteriori probability (APP) detector and a turbo decoder. However, the complexity of APP detection can become prohibitive since it grows exponentially with the number of transmitter antennas and the modulation order. In this paper, a MIMO receiver is proposed which replaces the optimum but complex APP detector by successive interference cancellation (SIC) incorporating sub-optimal matched filter detection. using convolutional encoding at the transmitter, the receiver performance is sustained via iterations between the simplified detector and the convolutional decoder. In combination with a proposed novel log-likelihood ratio (LLR) combining scheme, it is shown that the new receiver can outperform the APP-based receiver at a much lower complexity and with no need for channel equalization.