Study On Multicast Techniques Of P2P Streaming Media Based On Wireless Mesh Networks

With the development of the Internet, streaming media business gradually increased. Video on Demand (VoD), Internet Protocol Television (IPTV), tele-conferencing and distance learning have become the most popular applications in Internet. P2P (Peer to Peer) technology makes the Internet transferred from a centralized client-server model to a distributed model, which brought new development space for streaming media applications. At the same time, the rapid development of Wireless Mesh Networks (WMN) and mobile communication devices makes the user demand for P2P streaming media transferred from wired network to wireless network. Users' demand promotes the developments of the WMN-based P2P streaming media technology. Furthermore, the widely application prospects of WMN also attracted P2P streaming media technology into wireless networks.WMN-based P2P streaming system is a P2P streaming application implemented under the support of WMN. Considering the special characteristics of WMN network, P2P technology faces many challenges and problems in the WMN. For example, heterogeneous problem caused by the wide variety of wireless terminals, the mismatching problem between P2P overlay and underlying network, the interference problem among wireless links, the limited radio spectrum resources and lack of system-level experimental platform.For the above background and take the above problems into account, multicast techniques of P2P streaming media in WMN are focused on in this paper. It is based on the traditional multicast techniques of P2P streaming media in wired networks and is studied both from theoretical and experimental aspects. The contributions of this paper are presented as follows:(1) In order to manage the heterogeneous networks efficiently and to solve the mismatching problem between the WMN and its P2P overlay, a membership management protocol for P2P overlay in wireless network is proposed. The proposed protocol combines traditional BA model with gossip scheme. Decentralization and locally probability-preferential attachment are two key mechanisms in the proposed protocol. Through mathematical analysis based on complex network theory, the proposed protocol is proved stable and scale-free. Simulation results show that the proposed protocol solved the topology mismatch problem to some extent and more suitable for heterogeneous network environment than the traditional protocol.(2) Against the interference problem among wirelss links, a Lower-Cost Minimal Relay Tree (LCMRT) algorithm for WMN is proposed in this paper. The algorithm consists of two parts, multicast-tree construction and channel allocation. The multicast-tree construction algorithm selects a lower-cost path for data delivery on the condition of minimal relay nodes which reduces the end-to-end delay. At the same time, a more precise parameter of interference degree is introduced in channel allocation algorithm which decreases the interference between links and improves the system throughput The simulation results show that the LCMRT algorithm performs better than existed algorithm in time complexity, delay and throughput.(3) In order to use the limited radio spectrum resources more efficiently, a multi-channel multicast scheduling mechanism based on SNR (Signal Noise Ratio, SNR) feedback is proposed. The higher-SNR channel has higher-speed, thus the proposed mechanism allocates higher-priority data ito the higher-SNR channel. Simulation results show that through the proposed mechanism users'start-up delay and waiting time are reduced. Moreover, the bandwidth utilization is improved by new mechanism. However, more buffer space is used by the porpose mechanism than existed mechanism. As the development of hardware technology, it is easy for users to obtain disk space. Therefore, it is reasonable to further reduce users'waiting time in the price of a small increase in buffer requirements.(4) In order to evaluate the performance of P2P streaming media in WMN more precisely and objectivly, the system-level experimental platform of P2P streaming based on WMN is deployed in this paper. Through field experiments five factors are tested. They are the encoding rate, the encoding mode, with P2P methods or not, hops and topology despectively. Different network performance and video quality under the five factors are experimented.The experimental results show that the encoding rate, encoding mode and network topology are important factors affecting the video quality. However, hops and video quality are not related with each other directly. Combining P2P technology with WMN is feasible but there are both advanteges and disadvantages. The results are worth referencing both in theory and practice for future research.