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Transmission Adaptation for Broadband Wireless MIMO-OFDM Systems with Limited Feedback

This paper studies link adaptation technique for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with limited feedback. In order to utilize highly fluctuating MIMO channel efficiently and reliably, spatial mode switching between beamforming, diversity and multiplexing modes is needed. We propose mutual information effective SINR mapping (MIESM) method to spatial mode and modulation scheme selection problem in frequency selective MIMO-OFDM channels. The use of the effective received SINR allows accurate link error prediction leading to the enhanced link performance. Simulation results indicated that a low complexity adaptive system which applies diversity mode and multiplexing mode attain good performance in 2×2 MIMO. Slight performance improvement can be provided by using simple beamforming with two fixed beams in addition to diversity and multiplexing modes.