Research On Congestion Control Strategy In Delay Tolerant Networks

With the rapid development of wireless communications,more and more data are transmitted over wireless networks.In same wireless network such as interplanetary network,disaster relief network,military communication network,and vehicle-mounted network,nodes frequently move,link are intermittent,end-to-end path cannot be guaranteed and the network topology changes dynamically,traditional TCP/IP network protocols are no longer applicable to these challenging networks,so Kevin et al proposed a reliable message-oriented overlay network architecture called the Delay Tolerant Network(DTN)to achieve communication in these challenging networks.Although DTN is widely used,due to features such as frequent network link interruptions,long delays,resource limitations,and the storage-carry-forward communication mode adopted by it,it is easy to quickly deplete network-constrained resources and cause network congestion,degrade network performance,so implementing congestion control is a research focus in delay tolerant networks.Based on the in-depth study of the network characteristics and architecture of DTN,this paper focuses on the study of network congestion control from two aspects of routing protocol and buffer management.The main research work is as follows:(1)Research the traditional DTN routing algorithms deeply,through analysis and comparison,the advantages and disadvantages of each are pointed out;study and analyze the existing typical buffer management schemes,then summarize the advantages and existing problems of which;model DTN communication,build DTN simulation platform.(2)For the problem that the social-aware based routing algorithm is insufficient to consider the node energy and buffer resources,this paper proposes an improved social-aware based routing algorithm.The algorithm introduces the node's energy and buffer resources as the basis for measuring the node's choice of next hop,avoids selecting a node with large forwarding capacity but congested as the next hop node,thereby balancing the transmission capacity and load of the node,reducing network resource consumption,and effectively preventing network congestion.The simulation results show that this scheme guarantees the message delivery rate and extends the network life cycle.(3)For that message weight based buffer management schemes generally only use a single metric and can not drop messages reasonably,this paper proposes an improved message weight based buffer management scheme.The scheme divides the node buffer into source,relay,and target message queues,each queue allocates the drop weight for the messages in the queue based on the drop metrics set by different message attributes.When the network is congested,according to the order of the target,the relay,and the source message queue,drop the message with the highest drop weight in queue,thereby alleviating the network congestion.The simulation results show that this scheme improves the message delivery rate,reduces the network overhead and the average delivery delay.(4)Based on the research of routing protocol and buffer management in DTN congestion control,a joint routing protocol and buffer management for congestion control strategy is proposed.The strategy first selects the appropriate next hop node according to the relay selection metrics,and then determines the order of dropping the messages according to the buffer management scheme based on priority queue.and introduces a hop-by-hop ACK confirmation mechanism to delete the message and it's copies has been passed to the destination node in the network.The simulation results show that the joint congestion control strategy further improves network performance.