Low Complexity Linear MMSE detector with Recursive Update Algorithm for Iterative Detection-Decoding MIMO OFDM system

Iterative turbo processing between detection and decoding shows near-capacity performance on a multiple-antenna system. Combining iterative processing with optimum front-end detection is particularly challenging because the front-end maximum a posteriori (MAP) algorithm has a computational complexity that is exponential in the throughput. Sub-optimum detector such as the soft interference cancellation linear minimum mean square error (SIC-LMMSE) detector with near front-end MAP performance has been proposed. The asymptotic computational complexity of SIC-LMMSE remains O(n(t)(2)n(r) + n(t)n(r)(3) + n(t)M(c)2(Mc)) per detection-decoding cycle where n(t) is number of transmit antenna, n(r) is number of receive antenna, and M-c is modulation size. A lower complexity detector is the hard interference cancellation LMMSE (HIC-LMMSE) detector. HIC-LMMSE has asymptotic complexity of O(n(t)(2)n(r) + n(t)M(c)2(Mc)) but suffers extra performance degradation. In this paper, we introduce a low complexity front-end detection algorithm that not only achieves asymptotic computational complexity of O(n(t)(2)n(r) + n(t)n(r)(2) [Gamma (beta) + 1] + n(t)M(c)2(Mc)) where Gamma(beta) is a function with discrete output {-1, 2, 3,..., n(t)}. Simulation results demonstrate that the proposed low complexity detection algorithm offers exactly same performance as its full complexity counterpart in an iterative receiver while being computational more efficient.