A Study Of Information Exchanging Scheme Based On Network Coding In Wireless Multi-Hop Networks

The emergence of wireless communication has made communication technology experience another leap. As an important branch of mobile communications, Wireless Multi-hop Networks(WMNs) has a bright application in military, civil, commerce and research. However, it is because of the wireless characteristics that network performance is influenced. For example, the channel capacity, the energy of network equipment and the network security are all limited; what’s worse, network topology is changeable, which not only can’t satisfy people’s needs but also brings some difficulty in designing network protocols. Network Coding allows and encourages relay nodes to code data packets together receiving different source nodes either in a linear or in a nonlinear way before they are transmitted, thus leading to the improvement of network throughput, bandwidth and robustness. Therefore, it remains a problem worth studying how to combine network coding technology with wireless multi-hop network to improve the quality of data transmission. The author’s major contributions are outlined as follows:1. An information exchanging scheme based on network coding in wireless multi-hop networks(NCIE) has been studied. Existing literatures have proved that bringing network coding in information exchanging network is feasible. A network coding information exchanging scheme based on time slot multiplexing has been designed by using the half-duplex and time division multiplexing property, which aims at a network having potential coding opportunity with two data packets flowing in. To avoid the data loss caused by packets conflict, the sending and receiving regularity of relay nodes and source nodes has been provided. At the same time, the relay nodes buffer model, coding data packets model and the overall strategy of this project have also been taken into consideration and designed.2. The key technologies of the NCIE scheme have been studied. Combined with the network sliding window mechanism, the inserting and deleting process of node buffers have been analyzed. Firstly, to solve the problem of asynchronous data streams flowing in, asynchronous information exchange strategy has been designed, which has made an algorithm control relay nodes flexibly switch between network coding and store forwarding. Secondly, to solve the problems, such as not being able to receive information because of the losing of data packets, a node retransmission scheme based on TDMA has been proposed. Whether the packet has been successfully received or not is decided by the receiving packet number.3. The proposed scheme has been simulated on Matlab platform. Compared the proposed scheme with store and forward routing scheme by average throughput and coding gain. Besides, compare these two schemes and NCIE in different input data rate. The results have shown that the proposed scheme can effectively improve the network performance. With relay node number increasing, Network coding also increases, but hardly is the throughput affected. In the situation of asynchronous data flow, the network has become less affected by asynchronization and the end-to-end delay of the network reduces.