Development of SDM-COFDM prototype employing a hierarchical ICI canceller for MIMO-based broadband wireless access systems

This paper describes an SDM-COFDM (space division multiplexed-coded orthogonal frequency division multiplexing) prototype employing a hierarchical ICI (inter-channel interference) canceller for MIMO (multi-input multi-output)-based broadband wireless access systems. The prototype has two types of ICI cancellers: multiplicative and subtractive. The multiplicative canceller multiplies the received signals by the estimated inverse propagation coefficient matrix. In addition, the subtractive one generates ICI replicas, subtracts the replicas from the received symbols, weights the subtracted signals by the estimated propagation coefficients, and combines them to obtain diversity gain. Experimental results show that the newly developed prototype with 2×2 antennas obtains a 1.4 dB improvement in required CNR at the PER of 0.1 compared to that achieved with only the multiplicative canceller. It achieves more than 100 Mbit/s per 18 MHz bandwidth by using 64QAM with the coding rate of 3/4 in frequency selective fading environments.