On the Design of a MIMO-SIC Receiver for LTE Downlink

In this paper, we investigate different multiple-input multiple-output (MIMO) receiver structures based on MMSE filtering and sequential interference cancellation (SIC) for the downlink of the 3GPP long term evolution (LTE) system. We divide them into two approaches: symbol-SIC receivers, in which the detection and interference cancellation is done independently for each subcarrier, and codeword-SIC structures, in which the processing is carried out for each independently-coded stream by including the turbo-decoder inside the feedback loop. The results show that symbol-SIC receivers need to take into account the propagation of errors in the interference cancellation to provide the turbo decoder with reliable soft bit values. However, these are clearly outperformed by codeword-SIC schemes, due to the error correction capabilities of the turbo-decoder inside the feedback loop. We show that the best tradeoff between computational complexity and receiver performance is achieved by only cancelling the interference of a codeword when this has been successfully decoded.