On VoIP Packet Aggregation For Wireless Mesh Networks

Recently, WMN(Wireless mesh network) based on IEEE 802.11s protocol draft have been wildly researched. Comparing with Ad Hoc network or WLAN, WMN has much advantage and characteristic. Compared to Ad Hoc, WMN has more immobile topology, and the topology divided into access networks layer and back-bone network layer, so WMN is more suitable to be used as an access network. When compared to WLAN, WMN extended its coverage by using multi-hop wireless back-bone, and WMN also offers the ability of mobility management, WMN has a flexible network structure and makes the deployment easier. So WMN is one of the key technologys in next generation wireless access networks.VoIP is an extremely fast developing application in recent years, it became a key application of the next generation wireless networks. The performance of VoIP over wireless mesh network became a hot-point in research areas. VoIP requires the low delay, low packet loss rate, low delay jitter, Satisfing the QoS requirement is a big challenge for wireless mesh network. It was found that because of the short packets length and the short packets cycle, VoIP suffers a low bandwidth utilization rate and its QoS requirement is hardly to be satisfied, even more, the VoIP capacity of wireless mesh network, measured by the supported VoIP connections per unit bandwidth, is very low. This problem greatly influences the development of VoIP application in wireless mesh network.The thesis focuses on the performance of VoIP in wireless mesh network, namely, the supported VoIP connections per unit bandwidth. Based on the analysis of performance of the MAC layer and PHY layer, a method combined with the optimization of MAC layer parameters and packets aggregation was proposed to resolve the bottleneck effect and the low bandwidth utilization rate of VoIP in WMN, and finally makes a lot of growth of the performance of VoIP over WMN. The cross-layer designing method was used in the proposition. Using the topology information gained by cross-layer accessing, the optimization of MAC layer and adjustment of the policy of packet aggregation can be made.In the fouth paragraph we introduced the pricing strategy into packets aggregation method, called packets aggregation with pricing. This particular aggregation method achives the maximum network uitility, under the premise of fairness guarantee between various traffics. In details, this scheme combined with the DiffServ service and static pricing strategy, by dynamicly adjusting the weight of aggregation buffer queue in proportional fairness scheduling, the two goals, which are the fairness between the different service and the maximization of the network uitility can achieved synchronously. The result of the simulation indicates that the scheme proposed can both guarantee the QoS requirement and optimizing the network effectiveness.