Application Of Improved Prophet Routing In Delay Tolerant Networks

Delay Tolerant Network(DTN) is a kind of restricted network that long delays and frequent network fragmented can be tolerated. Unlike the traditional TCP/IP network, delay tolerant network does not have a stable end-to-end connectivity, and there exists some problems like high error rate, long delay and intermittent connectivity in DTN. Therefore, custody transfer is used to ensure reliable delivery of messages. Due to the special environment of DTN routing, the algorithm of routing and congestion control has been an important and difficult field in DTN research.Prophet algorithm is a routing algorithm based on probability strategy. This routing algorithm significantly reduces the blindness in forwarding process and improves the success rate of message delivery compared with Epidemic routing. However, with the expansion of network scale, a large number of copies will be produced, which may affect the network performance. Besides, Prophet does not optimize the message transmission policy and discard strategy.So we propose an improved routing algorithm of Prophet named PBSNW(Prophet based Binary Spray and Wait) in this thesis. It is based on Prophet routing and combins the copy control strategy to limit the duplicate of messages. The major contributions of our work are described as follows:Firstly, an improved Prophet routing algorithm based on probability index calculated by Prophet and combined with binary spray and wait(PBSNW) is proposed in this thesis. Simulation results show that the new algorithm improves the message delivery rates while reducing overhead ratio and delay.Secondly, an buffer management algorithm based on PBSNW is proposed to improve its congestion control strategy. In the algorithm, the delivery probability and message properties are used to construct a congestion improved metric(CIM). Messages with higher CIM have the priority to be forwarded to the nodes to improve the buffer utilization. Messages with the minimum CIM are discarded to reduce the impact of random dropping on routing efficiency.