Opportunistic Routing In Cognitive Radio Networks

With the development of wireless communication, wireless networks make life and work more convenient. Due to the unrestricted communication of wireless medium, wireless networks have received a lot of praise from users. Nowadays, the spectrum resources are regulated by a static allocation policy. In this situation, the spectrums available for allocation are limited. At the same time, the assigned spectrums are with low utilizations. The static allocation policy no longer satisfies the huge demand for wireless communication. Recently, cognitive radio (CR) technology can make the user sense and access the’spectrum hole’, and utilize the unoccupied spectrum to communication with each other, without interfering primary user’s communication. The available spectrums for each CR user are time-varying. This characteristic introduces additional complexities for routing in CR networks.This paper studies the issue of opportunistic routing in CR networks. The content of this paper is as follows:1. Sum up the characteristics of Ad Hoc networks, WLAN and CR networks. Propose the problems we prepare to study. To solve these problems, we provide preliminary solutions.2. Survey research topics of CR networks, Ad Hoc networks and WLAN, point out the existing research work’s weak point, and summarize the typical related work.3. Discuss routing and channel selection in Ad Hoc CR networks. The problem of our concern is:given a set of CR nodes with geographical positions and temporarily available channels for each node, how to design a routing algorithm and select channels, so that the average number of transmissions per packet is minimized. We proposed a novel distributed routing algorithm where packets are transmitted through successively geographic closer intermediate destination nodes step by step, until the eventually destination is reached. The intermediate destination nodes are locally chosen by a heuristic algorithm we develop. We also proposed an algorithm for selecting the operating channel for opportunistic routing. Extensive simulations are conducted to show the performance of our protocol.4. Study how to use network coding to further reduce the average number of transmissions per packet. We first propose a network coding graph and show our problem is a reduction from the maximum clique problem (MCP). Then, we propose a heuristic method to solve this problem. In addition, we introduce the implementation details. Extensive simulations are conducted to show the coding method can significantly reduce the average number of transmissions per packet.5. Discuss how to use opportunistic routing to extend the service coverage of AP and maximize the throughput of the whole network. This paper analyzes the transmission process of opportunistic routing and proposes the method to computing effective transmission time. We also propose a centralized opportunistic routing algorithm to let the clients relay traffic for AP. In addition, to deal with the situation of the arrival of a new client and the leaving of current client, we propose a distributed opportunistic routing algorithm to fix the route. Extensive simulations show that our method can increase the service coverage of AP and increase the network’s throughput.