Index Terms

Abstract

The noncoherent capacity of multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is first derived. Then, an adaptive bit-interleaved coded modulation (BICM) scheme for the MIMO-OFDM system that exploits transmitter beamforming and variable-rate-variable-power (VRVP) QAM is proposed to enhance the throughput in a time-varying environment. The throughput of the variable-rate (VR) scheme is proved to have the same pre-log factor as the lower bound of noncoherent capacity. Furthermore, it is proved that the VR scheme has the same diversity-multiplexing tradeoff behavior as MIMO systems with random Gaussian codewords. The effect of imperfect channel station information (CSI) on the effective channel signal-to-noise ratio (SNR) is explained. It is shown by computer simulation that adaptive BICM outperforms adaptive trellis-coded-modulation (TCM) when outdated channel estimation is used. The throughput of multiuser downlink is analyzed and OFDMA with opportunistic scheduling outperforms OFDM-TDMA scheduling with a constant enhancement that is dependent on the user number and the antenna number but independent of SNR