Research On Key Technologies In Delay Tolerant Network

Recently the technology of networking has developed rapidly, especially in the wireless network area. Nowadays wireless network is part of our daily life and has become the most important method of data transmission. The development of technology drives people to research new environment for new networks. More and more new types of network such as inter-planet network, satellite network and wildlife tracking network have been invented to solve the problems that traditional networks can't. In these new networks the stable end-to-end link which is the basis of traditional data transmission does not exist for the most of time. So how to transmit data packets in these networks became a well-known challenge. Thus the concept of delay tolerant network was proposed to face this challenge.DTN (delay tolerant network) is a kind of network in which there are no stable end-to-end links between nodes. DTN uses the store-wait-forward model to transmit data packets through the network. As there are more and more types of delay tolerant network, DTN has gradually become the research hot spot in both acdemical area and industry area. Many new technologies are studied in DTN such as new MAC layer protocols, new routing protocols, new transport layer protocols and the Bundle protocol. This thesis focus on three key technologies of delay tolerant network: MAC layer protocol, routing protocol and Bundle protocol. The main content and the original techniques are as follow:1. We described the basic definations about DTN, its protocol stack and the scenarios in which DTN can be used.2. We summarized the recent research work on DTN, showed the research on the routing protocols in DTN and presented some research projects on DTN.3. We discussed how to use TDMA in some special DTN scenarios and proposed a new TDMA slot assign algorithm EASA. EASA uses a dynamic frame length and dynamicly assign slots to nodes according to their demands. Simulation results proved EASA can increase the usage of network bandwidth and increase the overall performance of the network.4. We analyzed the current broadcast routing protocols in DTN and proposed a new on AEBP for DTN. AEBP uses adaptive thresholds determine technique and decrease the threshold according to packet hops. AEBP can significantly lower the protocol overhead.5. We did some experiments to see the performance of traditional packet dropping policies in DTN environment and found that these policies can't fulfill the need of DTN. Thus we developed a new packet dropping policy HWDP which uses historical information to calculate the weight for each packet and uses the weight to determine which packet should be dropped. Simulation results show that HWDP can achieve much better packet delivery rate comparing to the traditional ones.