Interference and Capacity Analysis in Wireless Mesh Network

Abstract

CSMA based MAC protocols are known to incur throughput imbalance when employed in multi hop wireless networks and existing literature lacks efficient MAC protocol for wireless mesh networks. Accurate modeling of interference and its affect on throughput of flows in the WMN is critical in designing future wireless networking protocols. This thesis performs a thorough analysis of interference and capacity in wireless multi hop network based on CSMA/CA MAC behavior. It is hypothesized that accurate modeling of interference at MAC level can maximize overall network capacity. In first part of thesis, twenty five unique possible two flow topologies have been classified into six categories based on MAC layer behavior and per flow throughput and closed form expressions for occurrence probabilities of the identified categories have been derived with particular observation that carrier sensing range based categories have high occurrence probability and cannot be ignored. MAC behavior of each category is discussed. In the second iii iv part, accurate computation of conditional packet loss probability and busy time is done based on geometrical configuration of the interfering links and also predicted per-flow throughput while addressing CSMA’s coordination problem. Unlike previous work, our analytical throughput model can clearly differentiate between links interfering from transmission range and carrier sensing range. Analytical and empirical results demonstrate improved accuracy, indicate throughput imbalances and provide better understanding of CSMA based protocol behavior in multi-hop wireless networks that can be used to design fair, scalable, and efficient MAC layer protocols.