CHOICE OF INTERLEAVERS FOR SPACE-DIVERSITY CODES IN ETSI-HIPERMAN AND IEEE 802.16a BROADBAND WIRELESS SYSTEMS

The choice of block interleavers in a MIMOOFDM based broadband fixed wireless access system for the HIPERMAN and IEEE 802.16a standards with spacefrequency trellis coding under typical channel conditions is examined and block interleavers that maximise the diversity performance in typical channels is found. It has prevously 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 apropriate interleavers. We find that different channels favour interleavers of different depths, and recommend suitable interleaver depths for the typical channels considered. With these interleavers the performances can be made comparable despite the variation in channel frequency selectivity.