| Wireless mesh network (WMN) is becoming a major paradigm for constructing user access networks that provide community or city-wide Internet connectivity. However, there are some challenges in wireless mesh networks.For example,a major barrier for the adoption of wireless mesh networks is severe limits on throughput;and the quality of service (QoS) can not be guaranteed.The network coding, as a new technique which relay nodes in the network not only forward but also process the incoming information flows, will have a good application in wireless mesh network.In our work,there are two routes in the research process of the key technologies for transmission based on the network coding in the wireless mesh network. The first route is transmission construction, and the other route is transmission character of WMN.To the first one, we propose a segment network coding (SNC) based on multipath to improve throughput.Furthermore, a mechanism of multipath transmission control protocol (MPTCP) that naturally adds network coding layer to current network systems is designed; and the game thory is investigated in the selfish nodes of multipath. In the second route of our research, we put emphasis on the network coding based on opportunistic routing; and the network coding based on synchronization is used to improve the performance of self-similar traffic. Through the two researching routes, the key technologies for transimission based on network coding in the wireless mesh networks are studied deeply in this thesis. The main work and contributions are presented in the following aspects:(1)There are some partial error data packets which are dropped in wireless multipath routing. An improved segment network coding algorithm based on multipath routing is proposed. In addition, we propose a MPTCP that naturally adds the segment network coding based on multipath to current network systems.In the segment network coding, we encode a group of segment data into independent new packets and transmit them along multiple paths to reduce the data packets retransmit and communications in relay nodes. In addition,a new MPTCP is investigated.In our scheme, according to the degree of freedom of decoding block from the destination feedback, the source node modify the coded data block to reduce restransmit of timeouts. As a result, the network is achieved higher throughput compared to TCP in the presence of lossy wireless links. Comprehensive simulations and results verify the theoretical results in the paper.(2) There are some selfish nodes which depress the peformance in wireless mesh network multiple paths. In this paper, a game theoretic method is used to investigate multipath inter-session network coding. There are some selfish nodes in wireless mesh network multiple paths. We apply game theory among in the multipath inter-session network coding selfish nodes. Firstly the Nash equilibrium in the proposed multipath transmission game model is derived. Secondly, some characteristic of multipath inter-session network coding game is proved.Lastly we propose a stimulus scheme which is suit for multi-path selfish nodes game. In the multipath transmission, we use the watch dog to check the existence of selfish nodes. For multipath selfish nodes, we adopt non-cooperation method to punish it. It is proved that Nash equilibrium is acquired for all players to obey the incentive scheme honestly. Experiments verify the theoretical analysis.(3)Now, the quality of service of streaming media wireless mesh network can not be guaranteed.A deterministic network coding based on opportunistic routing is proposed. Using of a deterministic network calculus tool, we derive the wireless mesh network nodes’backlog upper bound, the end-to-end upper delay bound and the end-to-end upper delay jitter bound based on the existing link throughput model of opportunistic routing; and then a deterministic network coding (DNC) which meets the QoS of streaming media is designed. An ETC considering the node’s backlog upper bound is proposed to a guide line which determines the encoding nodes. In order to improve the performance, we use network coding before the node’s backlog upper bound is exceeded.The represented ETP considering the jitter and the end-to-end upper delay jitter bound is a guide line which determines the received candidate nodes. The data packets are encoded among the candidate nodes according to the ETC. Comprehensive simulations and results show that the throughput is improved; the delay time and the jitter of end to end are degraded.(4) We present a low delay time network coding against the high decode time based on opportunistic routing in streaming media wireless mesh network this paper. There are two parts of variable length network coding (VLNC) and candidate node feedback (CNF) in the implement of low delay time network coding. Firstly, the decode delay time and reliability of variable length network coding are analyzed. Then, a new algorithm is proposed that the candidate node feedback the encoded data packet. The algorithm of low delay time network coding is implemented in this paper. And the same bank is output by counters in the candidate nodes. When it lack of the decode data packets in the destination node, the candidate node is the first node to find the encoded data packets. As a result, the decode time is reduced. Simulations and results show that the delay time is degraded and the performance is improved.(5) The length of queue and the ratio of data packet drop are increased in the intermidle nodes when self-similar traffic is occurred. An algorithm of network coding to reduce based on the synchronization is presented to reduce the queue length and the delay time when self-similar traffic is occurred. The algorithm is implemented based on synchronization after data packets are classified by destination address and lengths.The algorithm is suit to use in the bursty self-similar traffic. Comprehensive simulations and results show that the delay time is reduced and queue length is shortened. |
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