Downlink Performance Analysis of Full-Rate STCs in 2x2 MIMO WiMAX Systems

MIMO techniques play a key role in the current wireless specifications including IEEE 802.11n, IEEE 802.16e, and LTE. Indeed, spatial multiplexing (SM) and Alamouti code are already in use in WiMAX systems based on IEEE 802.16e specifications [1]. But more efficient full-diversity full-rate codes, such as Golden code [2], are still under discussion and have been proposed for future evolutions of the standards. However, the maximum likelihood (ML) or ML-like decoding of these codes is still not feasible for practical implementation. Existing papers include performance comparisons of such complex codes limited to simple scenarios and their performances in a real WiMAX environment have not been discussed in detail. In this paper, we present the performances of the Golden code, which is known to be the best full-rate full-diversity 2x2 STC, on a 2x2 downlink MIMO transmission and compare them with those of SM. The results show that the well-known performance advantage of Golden code over SM diminishes when real system scenarios are considered using powerful channel codes.