Research On Routing Optimized Policies In Resource Constrained DTN

In the last decade,Delay Tolerant Network (DTN) as a novel network seems to have become a hot research object, which differs from conventional networks, with high latency, intermittent connectivity, low transmissibility, inexistence of end-to-end path. On account of these characteristics, traditional routing protocols in the store-forward style can't be applied directly. Thus, DTN deploys a routing with store-carry-forward style and the research on routing policies in Delay Tolerant Network becomes a key issue. Many routing policies have been proposed from the perspective of sufficient resources in DTN. In those routing policies, constrained resource such as insufficient local resources and disproportion resource distribution,which are the common characteristics in DTN, was not taken into consideration. And that the local resources instead of the global network states were referred would bring about the challenge of achieving a common purpose between the global network and the routing policies. For the above reasons, a suit of routing optimized policies in resource constrained DTN are proposed in this paper, which includes three parts: a buffer management method, an optimized control information generating method and a routing policy.First of all, traditional buffer management methods mainly make use of characteristic of nodes or characteristic of messages to perform buffer management.Both differentiated services to the messages with different priorities and the fairness of message forwarding had been not taken into account. Therefore,a new buffer management method is proposed based on token bucket and WFQ, in which each node's buffer is divided into several queues according to the mechanism of combining token bucket with WFQ. Accordingly each queue is allowed to own a token bucket with a weight which varies as the number of tokens in the token bucket. Thus the goal of the differentiated services to the messages with different priorities and fairness of message forwarding is realized.Secondly, the researches on traditional optimized control technology were relatively deficient. Because of the narrow limitation of transmission performance which is caused by resource constrained DTN, an optimized control information generating method is proposed in the paper. It generates the optimized control information by evaluating the global network states. Thus the problem that the local resources instead of the global network states are referred is figured out.Finally, traditional routing policies depended mostly on the nodes' local resources when selecting relay nodes of messages. In spite of realizing the local optimum of selecting relay nodes, the optimal or sub-optimal global network performance can not be reached. As a consequence, a routing policy based on the optimized control information is proposed in the paper, in which relay nodes are selected in accordance with nodes' local resources such as nodes' buffer size and communication range, meanwhile the number of copies is controlled in accordance with optimized control information. Thus the objective of the optimal or sub-optimal global network performance is achieved.