Choice of interleavers for space-diversity codes in HIPERMAN and 802.16a broadband wireless systems

We study the choice of block interleavers in a MIMO-OFDM based broadband fixed wireless access system for the HIPERMAN and IEEE 802.16a standards with space-frequency trellis coding under typical channel conditions. It has previously been shown that a given code offers varying levels of error performance depending on the degree of frequency selectivity of the channel. Code performance was comparatively better in channels with higher frequency selectivity or delay spreads, while performance was particularly degraded in channels with low frequency selectivity. In order to extract the maximum possible frequency diversity and close this gap in performance, we investigate the use of appropriate interleavers. As different channels favour interleavers of different depths, we recommend suitable interleaver depths for the typical channels considered. With these interleavers the performances can be significantly improved and can be made comparable despite the variation in channel frequency selectivity.