Adaptive MIMO OFDMA for Future Generation Cellular Systems in a Realistic Outdoor Environment

Abstract

This paper presents a downlink performance evaluation of a candidate physical layer for future generation cellular communications systems employing link adaptive MIMO-OFDMA. Adaptation between various modulation and coding schemes in combination with both space-time block codes (STBC) and spatial multiplexing (SM) on the basis of channel knowledge is considered. By means of ray-tracing software, a detailed example coherent time-variant channel trace is generated. Subsequent application of physical layer simulation software to this channel trace yields PER and throughput results for all available link adaptation parameters. Various channel parameters are considered against this data and the SNR and H matrix determinant are found to have the most significant influences on the system throughput. Subsequently, LA algorithms are proposed whereby the system adapts according to SNR only and both SNR and H matrix determinant. The performance of these algorithms is compared to the optimal case.