Optimum Detection with Low Complexity for Collaborative Spatial Multiplexing in Uplink Mobile WiMAX Systems

In mobile WiMAX systems, uplink collaborative MIMO (Multiple Input Multiple Output) performs spatial multiplexing with two MSs (Mobile Stations), each with one antenna. As two MSs transmit collaboratively on the same subchannel region, the overall uplink capacity will be doubled. To perform this interesting technique with high performance, most system venders demand the optimal MLD (Maximum-Likelihood Detection) in the base station which has at least two antennas. However, the MLD is difficult to implement due to its explosive computational complexity. In this paper, we propose a novel MIMO decoding scheme which achieves optimal performance with low complexity for collaborative spatial multiplexing in uplink mobile WiMAX systems having an iterative channel decoder using bit log-likelihood ratio information. Simulation results show that the proposed scheme has the same block error rate performance of the MLD with only 28% computational complexity in terms of real multiplication, when both MSs transmit with 16QAM.