Research On Routing Policy In Delay Tolerant Networks For Emergency Communication

After the disaster,large-scale infrastructure such as bridges,roads,and electrical equipment were destroyed.It is difficult to effectively repair damaged infrastructure and power equipment in a short time.Stricken areas may be shut off from the world,and communication can not go smoothly.How to quickly establish an effective emergency communication network after the disaster is a problem worth studying.In post-disaster frequent interruption networks environment,some traditional wireless communication will not work effectively.Delay tolerant networks(DTN)uses the way of a "store-carryforward" to transfer messages,which can be applied to sparse nodes with intermittent links in the network environment,and is an effective mean to build emergency communication network.A unique routing policy should be adopted in the network due to characteristics of long delay,sparse node distribution,region-dependent segmentation and limited resources in the post-disaster environment.In this thesis,based on the analysis of post-disaster scenarios and the distribution and movement patterns of disaster victims,a DTN routing policy for post-disaster environment is proposed.The main work of this thesis is as follows:(1)A routing policy based on a regional center node.Based on the analysis of the distribution and movement characteristics of the people after the disaster,a highperformance node,which has a large buffer capacity and can communicate with ordinary nodes and ferry nodes,is proposed as the regional center node.A message collection and forwarding mechanism based on the regional center node is established in the region.The messages can be gathered in the regional center node.Inter-regional message transmission is accomplished by the cooperation between ferry node and regional center nodes.The ferry node cruises each regional center node according to the planned path to complete the interregional message transmission.(2)An inter-regional ferry path decision mechanism based on message choose exchange.To address the problem that the fixed ferry path lacks flexibility in responding to changes in post-disaster network environment.An inter-regional ferry path decision mechanism based on message choose exchange is proposed.Redundant message packets in the network is reduced by message choose exchange,and according to the changes of network data transmission requirements,the cruise path is dynamically adjusted to reduce inter-area message transmission delay.Extensive simulations are conducted and the results show the proposed routing policy can significantly improves network performance.The data delivery ratio of the whole area is improved and the transmission delay is greatly reduced.