Layered Multicast Based On Network Coding

Because of the heterogeneity of network and diversity of receivers, the source should multicast with different rate according to the actual network. Layered multicast is a classic layered multicast technology to address the network heterogeneous problem. It divides the original information into a certain number of layers with dirrerent priority and transmits each layer with corresponding rate according to the situation of receivers.Network coding has changed traditional routing with only store-and-forward, and it allows relay nodes to code the data they received from multiple pathes. Recently, network coding has been a hot subject of the research field on network communication. How to make use of the advantage of network coding to improve thoughput of layered multicast has been the the subject we focus on.In the paper, the model of existing centralized layered multicast algorithm and distributed layered multicast algorithm are proposed respectively first. Then the two kinds of layered multicast are described detailed, and their advantages and disadvantages are analyzed at last.A layered multicast algorithm based on feedback, LMBF, is proposed then, which has improved the existed problems of the typical distributed layered multicast algorithm Pushback as following,1) there may be wasted bandwidth during transmission,2) receivers may not decode all of information contained in the packets they received,3) the mechanism can’t consider how to deal with the receivers are intermediate nodes at the same time. To solve these3problems, LMBF algorithm utilizes appropriate improvement scheme respectively, which are decoding judgment, feedback of the maximum request and preprocess on special receivers. Theoretical analysis shows that for a certain network, the total receiving rate with LMBF algorithm is always greater than or equal to Pushback algorithm. Finally, the LMBF algorithm and Pushback algorithm are simulated with VC++, and the simulation results show that total receiving rate improved with LMBF algorithm is about10%when there are only leaf receivers. While as LMBF algorithm can effectively process the receivers being intermediate nodes at the same time, the performance gain could be up to20%with LMBF algorithm when a receiver is an intermediate node with the probility of0.2.The performance of Pushback algorithm is not good in the application environment with data loss and different data amont required to be synchronous of different layers. To address this problem, LMDSER (Layered Multicast with data Synchronization and Enhanced Reliability) algorithm is proposed in this paper based on Pushback algorithm. LMDSER makes use of the difference between the data amont required to be synchronous of low layer and high layer to construct the linear coding combination as the redundant information of the low layer. Extension simulation is made and the results show that LMDSER could obtain10%-15%performance gain compared to Pushback algorithm when there are data lost.