Energy-saving And Routing Research In Delay Tolerant Network

The Internet has achieved great success in interconnecting tens of millions of communication equipment of the global heterogeneous network, and its achievements are due to TCP/IP protocol suite. However, for limited wireless network such as military wireless ad hoc networks, interplanetary network and wireless sensor networks, the network is prone to disconnected phenomenon, connection between source nodes and destination nodes is not stable, so the current TCP/IP model can not provide a good service. In order to achieve the interconnection between these networks, in2002, Kevin Fall proposed a message-oriented overlay architecture in conference of ICIR, called Delay Tolerant Network (DTN). DTN using store-carry-forward routing pattern, so that messages can be forwarded hop by hop to the destination node, then complete the communication under the limited network environment.In DTN, the nodes have characteristics of movement, sparse distribution and limited resources (energy, bandwidth, buffer size), etc., the communication link is often intermittently connected, which makes it difficult to transmit network data timely and reliably to the destination node, causing the large network communications overhead, the high data transfer delay, and low reliability. Currently, DTN’s research focuses on the aspects of the routing strategy, and the main goal is to lower the transmission delay and overhead to achieve higher data delivery rate. However, the energy consumption of nodes is a critical issue, it directly affects the lifetime of the network. Therefore, according to the characteristics of DTN, designing an efficient and reasonable data transfer mechanisms to reduce network energy consumption, to transfer data fast and reliably to the destination node, and achieve an effective balance among the data delivery rate, overhead, delay becomes the primary problem of DTN to be solved.Firstly, the concept of DTN, DTN architecture, mobility model of nodes, the node’s contact probing mechanisms and several typical routing protocols are introduced, and then analysis and research an energy-saving scheme for DTN, lastly, make an improvement of the existing spray and wait routing protocol. The main research programs and contents are as follows:In realistic Delay Tolerant Networks (DTNs), the nodes need to keep probing the environment to discover the neighbors in their transmission range. In this thesis we assume that the network has a small amount of energy-sufficient nodes (called core nodes) continuously transmitting beacon messages, thereby enhancing the probability of successful probing, while alleviating the regular nodes’ energy consumption. We first derive the regular node’s probability distribution of link duration when the network has some core nodes, then on this basis, derive the theoretically energy consumption of the regular node. When compared with the network that only has regular nodes, besides energy saving, the packet delivery rate and average delay are all improved.In this thesis, we put forward the concept of CoN (Capability of Node) based on the nodes’ different performances. Then we propose CoN-ASW (Adaptive Spray and Wait Routing Algorithm based on Capability of Node) routing algorithm. In this algorithm, nodes dynamically forward the number of message copies and decide whether to forward messages to the encounter nodes in the wait phase. This self-adaptive distribution and forwarding strategy can better adapt to dynamic network topology, so as to improve the message delivery utility and reduce the network overhead.In this thesis, the ONE simulator is used to simulate and assess for Core nodes-assisted energy-saving and routing research in DTN, as well as the adaptive spray and wait routing algorithm based on capability of node in DTN, then the simulation results were analyzed and compared.