Research On Key Technologies Of Reliable Networking And Efficient Transmission

With the rapid development of Internet, more and more applications of high definition pictures, audio and video boost network traffic exponentially. However, the current situation of network construction is seriously mismatched with the traffic explosion. Therefore, an efficient network environment is the fundamental for various kinds of applications. Basically, the rapid development of E-commerce, online payments and other applications demand the network with faster real-time response. And many kinds of natural disasters, attacks and destruction force a network must be in need of high tolerance to failures. Thus, a design of good data protection, recovery ability and transport mechanism will be necessary for the efficiency and reliability of network.This dissertation analyzes the current researches in network topology optimization, fault protection, rateless coding, and then indicates the further work should be performed about the improvement of network reliability and efficiency. Focus on these work, this dissertation launches a series of studies for highly efficient and reliable network topology optimization, link failures protection, and efficient rateless codes designing. Some valuable research results are achieved in the following aspects.1. Design of efficient network topologyWith given nodes and links, a network topology optimization algorithm based on average distance is improved, which could reduce the computational complexity by studying the characteristics of the adjacency matrix of network topology. After calculation, the algorithm may find many network topologies which have the minimum average distance. In order to choose the best network topology, the average distance after the failures of every node and link is investigated, then the topology with the minimum average distance is the optimal network topology.2. Network topology with the maximum node-connectivity and the maximum node-disjoint pathsThis dissertation proposes a network model which has the maximum node-connectivity and the maximum node-disjoint paths between any two nodes. After that, it also proposes a design algorithm with given numbers of nodes and links. The computational complexity can be reduced by some techniques. The computation results show that the algorithm can get the network topology which has the maximum node-disjoint paths, and the node-connectivity is equal or near to the theoretical node-connectivity. An algorithm based on the high efficiency and reliability is proposed to design the network which has the maximum node-disjoint paths, the maximum node-connectivity and smaller average distance.3. Network coding-based protection strategy against multiple link failuresA protection scheme based on network coding is improved to protect multiple link failures with the minimum protection links. The scheme considers the primary link and protection link failures simultaneously, which is closer to the real communication environment.4. Performance indices and ideal rateless codes modelThis dissertation analyzes the applications and drawbacks of current performance indices of rateless codes, proposes several novel performance indices, extends definition of traditional systematic code, and proposes an ideal rateless codes model.5. Rateless coding scheme based on two stages and forward equal probabilityBased on the ideal rateless codes model, a rateless coding scheme based on two stages and forward equal probability(TS-FEP) is proposed. Simulation results show that the rateless codes from the proposed scheme have higher code rate, lower average delay, smaller maximum disorder and bigger uniformity recovery entropy than that of other schemes. The TS-FEP algorithm can be modified for unequal error protection, which also has good performance as above. Sometimes, it is difficult to know the exact channel knowledge, but the worst case can be got. Therefore, a design scheme is proposed with the maximum erasure rate. Simulation results show that its performance is slightly better than that of TS-FEP. Finally, the influence of the coding algorithm on decoding algorithm is analyzed. The proposed coding scheme can greatly reduce the computational complexity of Gaussian elimination and BP decoding algorithm.6. Rateless coding scheme based on cyclesIn general, each information symbol of a file is not isolated. An efficient rateless codeing scheme based on cycles is proposed with the consideration of the correlations. The rateless codes from the proposed scheme have good performance. The scheme is closer to the real communication environment than other coding schemes.7. A rateless coding scheme based on efficiency-fairness principlesThe rateless codes from the TS-FEP algorithm have good performance, but the performance is average performance. The TS-FEP algorithm can not ensure that the performance of each communication process will satisfy the performance requirements. So this dissertation modifies the ideal rateless codes model, and proposes a rateless coding scheme based on the new model. The scheme based on efficiency-fairness principles, which improves the rateless codes performance by the combination of determinacy and randomness. Simulation results show that the rateless codes of the proposed scheme have better performance. The scheme can be used for unequal error protection after minor modifications.