Joint Link/packet Scheduling, Rate Allocation and Routing Optimization in Stdma Based Wireless Mesh Networks

JOINT LINK/PACKET SCHEDULING, RATE ALLOCATION AND ROUTING OPTIMIZATION IN STDMA BASED WIRELESS MESH NETWORKS Ahmet Emrah SEZGİN M.S. in Electrical and Electronics Engineering Supervisor: Assoc. Prof. Dr. Ezhan KARAŞAN August 2009 Wireless Mesh Networks (WMN) are a promising solution for next generation wireless access networks since they cherish benefits of having a reliable backbone in an ad hoc nature. This thesis investigates the joint scheduling and routing problem in minimizing the maximum delay required for delivering a given packet traffic to the intended destinations in spatial reuse Time Division Multiple Access (STDMA) based single channel multi-rate WMNs. Firstly, an Integer Linear Programming (ILP) model is developed by considering the constraints inherent to the problem, such as the Signal-to-Noise and Inteference Ratio (SINR) and capacity. The model is then improved by using additional constraints, such that these constraints do not affect the final solution but narrow down the search space. Because of the computational complexity, this ILP based optimization model is limited to small sized networks. We then consider different approaches to obtain sub-optimum solutions and find good lower and upper bounds on the optimum solution. LP and Lagrangian relaxations are used for obtaining lower bounds. Improving LP relaxation with cutting planes and Lagrangian relaxation, we obtain lower bounds that are up to 100% tighter than the simple LP