Channel Access and Packet Scheduling in Wireless Multihop Networks with QoS Guarantees

Wireless Multihop Networking (WMN) has emerged as a key and promising next-generation wireless technology. The ad hoc network formation andmultihop communications incur more challenges than conventional wireless networks. This dissertation investigates channel access, medium access control (MAC), packet scheduling, and their interactionswith the physical layer in WMNs. Existing wireless MAC and packet scheduling algorithms are briefly reviewed. Their analysis often does not consider the specific properties of WMNs, in particular in terms of the wireless channels, the traffic characteristics, and their interaction.In this thesis, we apply queueing theory to analyze typical MAC and scheduling schemes in WMNs, including delay-balancing priorityscheduling, TDMA and slotted ALOHA. Packet dropping strategies are employed to guarantee delay constraints and reduce unnecessary energyconsumption. The Quality of Service (QoS) parameters under study include delay, packet loss rate, throughput, and capacity.Our analysis quantitatively explains why TDMA outperforms slotted ALOHA not only in terms of throughput, but also of delay. An importantfeature caused by multihop communications is the correlations, which exist between the wireless channels themselves, between the channels and traffic flows, between the traffic flows themselves, and between the delays of each node. Due to such correlations, the wireless channel performance is better than when all traffic flows are independent. Besides, the traffic correlation helps to form a natural spacing between simultaneously transmitting nodes, achieve efficient spacial reuse, and more importantly, avoid the overhead of establishing and maintaining the spacing. Furthermore, the correlationbetween the delays of each node substantially improve the end-to-end (e2e) delay variance. Therefore, taking advantage of these correlationcould be helpful in the cross-layer design of efficient, distributed and cooperative protocols in WMNs.