| Network coding has been proved to be able to improve network performance,but with the increasing scale of the Internet,the types of access devices become more and more abundant,which makes the problem of network heterogeneity more and more serious,while the traditional single-rate network coding is difficult to meet the multi-rate requirements of heterogeneous networks.The layered network coding can not only satisfy the multi-rate requirements of heterogeneous networks by performing layered operation at source nodes,but also significantly improve the network throughput by using the coding and decoding capabilities of network coding,and it has become one of the research hotspots of network coding in recent years,and the optimization problem of efficient transmission scheme based on layered network coding in heterogeneous networks has become one of the difficulties in research.To a certain extent,the selection of optimization objects and optimization algorithms affect the specific performance of the network.Designing a reasonable layered network coding optimization scheme provides a new research idea for the application of network coding in heterogeneous networks,and has a certain practical significance in improving the performance of heterogeneous networks.Aiming at heterogeneous networks with single source and multiple sinks,this paper discusses several optimization schemes of hierarchical network coding based on bionic algorithm.The main research contents and results of this paper are as follows:1.The related concepts of intra-session network coding network model are analyzed,and the mathematical description of its optimization problem is summarized.With the layer rate as the optimization object,an optimization scheme of intra-session network coding based on improved particle swarm optimization is designed.And the layer rate in this scheme is no longer fixed,which breaks the limitation of the fixed layer rate optimization scheme.The more reasonable layer rate allocation improves the maximum flow that each sink can achieve,thus improving the throughput of the whole network.2.According to the difference between inter-session network coding and intra-session network coding,this paper re-sums up the mathematical programming of optimization of inter-session network coding and designs an optimization scheme based on firefly algorithm according to its characteristics,and takes link layered type and layer rate as the common optimization object,fully considers the impact of various combinatorial factors on network throughput.This scheme regards the location of firefly as a kind of distribution scheme of link layered type and layer rate,and the brightness of firefly corresponds to the throughput of the network,and it realizes the optimization and updating of the distribution scheme by using the characteristics of low brightness firefly moving to high brightness firefly.Experiments has shown that the improved firefly algorithm can improve the network throughput with fewer iterations because of its fast search ability.3.Some shortcomings of the firefly algorithm are analyzed and an optimization scheme of inter-session network coding based on shuffled frog leaping algorithm according to its improvements is proposed.By improving the meme group rule and the local optimization position change rule of the shuffled frog leaping algorithm,the algorithm keeps the trend of global evolution and avoids falling into local optimum.Compared with the optimization scheme based on firefly algorithm,the complexity of the scheme is reduced,so the number of iterations needed to optimize is less than that needed. |
