Rate-Maximizing Adaptation in MIMO-OFDM with Space-Time-Frequency Coding

By matching transmitter parameters to time-varying channel conditions, adaptive modulation provides considerably improved communications relative to designs assuming no channel knowledge at the transmitter. In this paper, after introducing a space-time-frequency (STF) coding method for multiantenna orthogonal frequency division multiplexing (OFDM) transmission over frequency-selective fading channels, we develop an adaptive MIMO-OFDM transmitter based on available channel state information. Under the constraints of fixed transmit-energy and prescribed error performance, our objective is to maximize the transmission rate by applying an adaptive energy and bit loading scheme across OFDM subcarriers. Simulation results are also presented, which illustrate the tradeoffs between design parameters.

Keywords:

MIMO-OFDM , Diversity methods , Space-time-frequency codes , Adaptive modulation , Fading channels