MMSE Soft-Interference-Cancellation Aided Iterative Center-Shifting K-Best Sphere Detection for MIMO Channels

Based on an Extrinsic Information Transfer (EXIT) chart-assisted receiver design, a low-complexity near-Maximum A Posteriori (MAP) detector is constructed for high-throughput systems. A high throughput is achieved by invoking high-order modulation schemes or multiple transmit antennas, while employing a novel sphere detector (SD) termed as a center-shifting SD scheme. The center-shifting SD is assisted by the MMSE soft- interference-cancellation (SIC-MMSE) algorithm. The resultant scheme is capable of attaining a considerable complexity reduction over the conventional SD-aided iterative benchmark receiver. For example, the SIC-MMSE center-shifting scheme may enable the iterative receiver to achieve a near-MAP performance in the challenging scenario of an (8 x 4)-element rank-deficient 4-QAM SDM/OFDM system. This near-MAP performance is achieved, despite imposing a reduced detection-candidate-list-generation- related complexity, which is about an order of magnitude lower than that exhibited by the list-SD dispensing with the proposed center-shifting scheme. As a further benefit, the computational complexity associated with the extrinsic LLR calculation was reduced by a factor of about 64. The associated memory requirements were also reduced by a factor of 64.