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The newly emerging wireless backhaul network has fundamental difficulties in supporting Voice over IP (VoIP) applications due to the MAC overheads introduced by huge amounts of small packets. Packet aggregation is a promising approach to mitigate these overheads. However, previous approaches to such problems are often stringent, not adaptive to the change of channel conditions. They are operated by each TAP (Transit Access Point) separately without any coordination in the use of shared channels. As a result, they fail to ensure the VoIP quality in terms of delay and loss. The major contribution of this paper is the proposal of a coordinated aggregation algorithm, which is adaptive and distributed. By coordinating with neighboring TAPs, the proposed algorithm is able to assign an appropriate aggregation rate to each TAP, aiming at better channel utilization and lower packet loss and delay. We evaluate this design by comprehensive analysis and simulations. The simulation results show that our algorithm significantly improves the VoIP capacity in wireless backhaul networks and outperforms existing aggregation algorithms.

Recently, peer-to-peer (P2P) model becomes popular due to its outstanding resource sharing ability in large-scale distributed systems. However, the most popular P2P system – unstructured P2P system, suffers greatly from the mismatching between the logical overlay and physical topology. This mismatching problem causes a large volume of redundant traffic, which makes peer-to-peer system far from scalable and degrades their search efficiency dramatically. In this paper we address the mismatching problem in an unstructured P2P architecture by developing a distributed overlay optimizing algorithm – HAND (Hops Adaptive Neighbor Discovery). Through comprehensive simulations, we show that HAND significantly outperforms previous approaches, especially in large-scale P2P systems.