| In recent years, network coding technology is improved in great speed. Research results shows that network coding can improving throughput, reliability and robusty for wireless networks. Naturally, the combination of distributed wireless network and network coding attracts researchers' great attention. In this thesis, we focus on the network coding based distributed networks. The theory of network coding, and its applications in wireless networks are studied. this thesis has engaged in extensive research on network coding scheme design, reliability insurance, channel utilization and the impacting on real-time applications.In this thesis, we analyze the background and features of wireless networks. Then select random network coding algorithm as basic algorithm to study roundly based on the analysis and remark of status and problems remaining unsolved. In the meantime, give the related technology for random network coding for wireless networks based on the application background of the research.Based on the characteristic of wireless network's channel and topology, a random network coding solution for improving the reliability of wireless communications is introduced. A new conception hyper-path is defined as a sub-graph, which is scalabel and can be established without any knowledge of network topology. With network coding, the nodes in a hyper-path can achieve high reliability by making the best of wireless broadcast nature and the cooperation communication of redundant node in the neighborhood.Packets from the source nodes in a distributed wireless network often have to hop more than once before it reaches the destination node. Unfortunately, when existing coding schemes is used in such multi-hop networks, the drawbacks of high delay, low throughput and waste of channel resources may follow. Here, after analyzing existing schemes, an improved network coding scheme for multi-hop wireless networks is designed, relative to tradition network coding schemes, the throughput in our scheme do not sensitive to the count of hops, and the waste of channel resource is also can be alleviated.In random network coding schemes, packets always are assembled as a block, and then all the coding operation is based on this block. So, the channel utilization must differ from that in traditional packets based transmissions. Therefore, we study the behaviors of channel utilization in random network coding context, and the influence factor of channel utilization is analyzed, then the method of computing maximum channel utilization is given.Random network coding benefits a lot to wireless communications, but it brings us a trouble in time-sensitive applications simultaneously. A block can be used only after it can be decoded as a whole, so the time delay that from the beginning of block transmission to decoding has to be controlled carefully. And then, a statistical model of block delay based on 802.11 wireless networks is established. On the basis of this model, an adaptive block size determination algorithm for block delay control is introduced. After that, the relationships among block size block delay and channel utilization are investigated by simulations.In conclusion, we propose the further development directions of wireless network coding. |
