Research On Coding-Aware Opportunistic Routing In Wireless Networks

Due to the interference between the signals of the same frequency, the limited network bandwidth resources, the mobility of the network nodes and radio channel instability, the transmission efficiency of the wireless network is severely affected. How to ensure and improve the wireless network transmission efficiency, throughput, and robustness is a critical issue in wireless communication network. Routing protocols directly determines the transmission performance of the network and the traditional wired network routing protocols are not well suitable for complex wireless network communication environment, and can’t provide efficient network transmission for wireless networks.In order to improve the performance of the wireless network transmission efficiency and throughput, the researches have proposed two new technologies network coding and opportunities routing, and provided new ideas for the design of wireless routing protocols. Because network coding and opportunistic routing take full advantage of the broadcast nature of the radio channel, many researchers have made a lot of new routing schemes combined with the advantages of both two technologies, the combination of the two technologies can further improve the transmission efficiency and throughput of the wireless network. Currently, most of the combination schemes are based on intra-flow network coding, and do not consider the coding opportunity among different data flows. In addition, these routing schemes do not take into account the influence on the transmission efficiency of opportunistic routing made by transmission rate.In view of the problems mentioned above, we have made a lot of research work, and obtained the following innovative achievements:1) Propose a new any-path coding-aware opportunistic routing ACOR. The opportunistic routing has multi-path propagation characteristics, and therefore there are a lot of inter-flow network coding opportunities in opportunistic routing. In order to take full advantage of the inter-flow network coding opportunities in opportunistic routing, we combine opportunistic routing and network coding to propose any-path coding-aware opportunistic routing. The combination of opportunistic routing and inter-flow network coding can make full use of the broadcasting feature of radio channel and the multipath propagation characteristics of opportunistic routing. As the result of simulation experiment showed, ACOR can largely improve forwarding efficiency and throughput of the network.2) Propose a new multi-rate coding-aware opportunistic routing MCOR. The transmission rate of a node affect the wireless network connectivity, link quality and bandwidth utilization. First, using a single rate over the entire network underutilizes available bandwidth resources. Some links may perform well at higher rate, while others may only work at lower rate. Second, and most importantly, the network may become disconnected at a higher transmission rate. This thesis presents a multi-rate coding-aware opportunistic routing scheme, combined inter-flow network coding with opportunity routing and transmission rate selection mechanism to improve the transmission efficiency of forwarding nodes. In order to assess the transmission efficiency of encoding nodes in multi-rate environment, we also propose the expected coding-aware transmission time (ECTT) metric. According the ECTT metric, forwarding node selects an optimal transmission rate and an appropriate candidate nodes set for each flow. Simulation results show that, compared to single-rate opportunistic routing and ordinary multi-rate opportunistic routing, MCOR can largely improve the throughput of the network.