Near-Optimum Detection with Low Complexity for Uplink Virtual MIMO Systems

In mobile worldwide interoperability for microwave access (WiMAX) or 3rd Generation partnership project long-term evolution (3GPP-LTE), uplink virtual multiple input multiple output (MIMO) technology is adopted to perform spatial multiple access with two portable subscriber stations (PSSs), where each PSS has an antenna. As two PSSs transmit simultaneously on the same orthogonal frequency division multiple access (OFDMA) resource blocks, the overall uplink capacity will be doubled. To employ this interesting technique with high performance, most system venders demand the optimal maximum-likelihood detection (MLD) scheme in the radio access station (RAS). However, the optimal MLD is difficult to implement due to its explosive computational complexity. In this paper, we propose two efficient MIMO decoding schemes that achieve near-optimum performance with low complexity for uplink virtual MIMO systems that have an iterative channel decoder using bit log-likelihood ratio (LLR) information. The simulation results show that the proposed schemes have almost the same block error rate (BLER) performance as that of the optimal MLD with only about 15.75% and 28% computational complexity in terms of real multiplication, when both PSSs transmit 16 quadrature amplitude modulation (QAM) signals, and only about 3.77% and 7.22% for 64 QAM signals.