Diversity and Adaptive Modulation & Coding Aware Routing in WLAN Multihop Networks with Centrally Scheduled Multiple Access

This thesis presents novel multihop relaying schemes capable of incorporating multihop diversity in routing calculations for centrally scheduled systems using adaptive modulation and coding. The routing algorithms can factor multihop selection combining and multihop maximal ratio combining (MRC) in digital or hybrid digital and analog relaying systems (HDAR). These diversity schemes do not require additional bandwidth or transmit power beyond that already required for multihop relaying. Furthermore the frame segmentation scheme incorporates modulation and coding used on route hops and can adjust to maximize diversity gains and enhance performance. The energy consumed when using multihop relaying is equal to that when using singlehop relaying due to frame segmentation, yet we can achieve considerable performance gains. These novel routing algorithms and diversity techniques are the main contribution of this thesis. The performance of these schemes is investigated for both 2-hop and multihop networks in the downlink scenario using a HiperLAN/2 wireless LAN test-bed. 2-hop relaying with proposed multihop diversity techniques was observed to offer considerable throughput increases particularly when the relaying terminal is situated nearer to the destination and using adaptive modulation and coding. Our results also show that 2-hop relaying can extend the coverage area to three times that of a singlehop network while offering significant throughput increases. Multihop quadruples the extension of the coverage area and offers further increase in throughput with respect to singlehop. Advanced routing incorporating modulation and coding can also significantly increase network performance in HDAR systems.