MAC Level Performance Comparison of Distributed and Adjacent OFDMA Subchannels in IEEE 802.16

This paper provides a comprehensive simulative performance evaluation of the OFDMA sub-channel schemes which are used in the IEEE 802.16 standard. The sub-channels are either distributed or adjacent in the frequency channel. The analysis is focused on the tradeoff between accuracy in the SINR estimation due to time-correlated fading processes and the exploitation of diversity. The adjacent sub-channel scheme provides a high degree of diversity in the sub-channel quality compared to the distributed approach. The reason for that is the averaging effect of the latter scheme. At the same time that effect is also responsible for the more accurate SINR estimation in the distributed sub-channel scheme. The performance comparison is conducted for the downlink in a multi-user reference scenario with mobility.