Low Complexity Precoding of BICMB- OFDM-SG for Wireless Broadband System

Multi-Input Multi-Output(MIMO) techniques can achieve higher throughput and improved reliability in wireless broadband communications by exploiting spatial diversity in multiple-antenna wireless communications. By combining the spatial diversity and spatial multiplexing we can fully exploit the MIMO channel capacity. BitInterleaved Coded Multiple Beamforming (BICMB) can achieve both spatial diversity and spatial multiplexing for flat fading MIMO channels. For frequency selective fading MIMO channels, BICMB with OFDM (BICMB-OFDM) can be employed to provide both spatial diversity and multipath diversity, making it an important technique. Full diversity of BICMB-OFDM with Subcarrier Grouping (BICMB-OFDM-SG) can be achieved within the condition RcSL ≤ 1, where Rc, S, and L are the code rate, the number of parallel streams at each subcarrier, and the number of channel taps, respectively. The full diversity condition implies that if S increases, Rc may have to decrease to maintain full diversity. As a result, increasing the number of parallel streams may not improve the total transmission rate. In this paper, the precoding technique is employed to overcome the full diversity restriction issue of RcSL ≤ 1 for BICMB-OFDM-SG. First, the diversity analysis of precoded BICMB-OFDM-SG is carried out. Based on the analysis, a full diversity condition related to the combination of the precoding matrix, the Low density parity check codes, and the bit interleaver is provided. Then, the full-diversity precoding design is developed with the minimum achievable decoding complexity. Thus provides a sufficent method to guarantee full diversity, better performance and higher throughput while minimizing the increased decoding complexity .