abstract
-
In this thesis we study the handoff problem of mobile stations (MSs) jointly with the resource management at the access points (APs) for wireless mesh networks (WMNs), where the APs can dynamically adjust the transmission power and time to each of the associated MSs. Two objectives are considered, one is to balance the energy consumption of the APs, and the other is to achieve fair throughput among the MSs. Since the global optimum solutions are difficult to obtain, we propose heuristic schemes for achieving each of the objectives. The objective of balancing AP energy consumption is achieved in two steps. The optimum transmission power and rate is solved at each AP so that to minimize the energy consumption of the AP, assuming the MS-AP association is given. Two handoff schemes are then designed to find which MSs should be associated to which APs during each scheduling interval (SI). The schemes are based on energy consumption information exchanged among neighboring APs. The real-time energy balancing (REB) scheme tries to balance the energy consumption of the APs in each SI, while the long term energy balancing (LEB) scheme balances the AP energy consumption over a longer term. Our results indicate that the network lifetime can be significantly extended using the proposed handoff schemes, compared to the simple distance-based handoff scheme, and using LEB can achieve balanced AP energy consumption with a small number of handoffs. The second part of the thesis is to consider the MS handoff and AP resource allocations in order to achieve fair throughput among the MSs. An optimization problem is formulated and solved at each AP to achieve long term proportional fairness of the throughput among the MSs, assuming the MS-AP association is known. Two handoff schemes are proposed, one is utility-based, and the other is number-based, in order to determine which MSs should be associated to which APs. Our results show that both the schemes are good at achieving fair throughput among the MSs, and the schemes are not sensitive to MS moving speed or group mobility patterns. The number-based scheme is simpler than the utility-based one in terms of implementation.