EFFICIENT COOPERATIVE CACHING IN DISRUPTION TOLERANT NETWORKS

Abstract

Opportunistic networks or Disruption Tolerant Networks (DTNs) are mobile networks in which a complete end-to-end path rarely exists at a time. Due to the high mobility of nodes, and limited radio transmission range, two nodes may not always be able to communicate with each other. Therefore, these networks are also called Intermittently Connected Networks (ICNs). Thus, communication is plausible only at the encounter opportunities between nodes. This necessitates the use of store-carry-forward communication paradigm for routing messages from source to destination, in which intermediate mobile nodes store data to be transmitted till they find an appropriate relay node in the path towards the destination. In Disruption Tolerant Network (DTN), determining the exact location of data and amount of delay to query the data by a requester is a major concern. It is costly for a node to maintain information of opportunistic paths to every other node in a DTN. Identifying appropriate caching locations is a difficult task. In this thesis, we propose a Greedy technique for selecting the nodes for caching data based on the past performance of the respective nodes so that data queries can be satisfied with less delay. Our basic idea is to cache data at a set of Proper Nodes (PNs), which can be easily accessed by other nodes in the network. We present a novel algorithm to select the PNs. This algorithm ensures that the PNs are not clustered to damage the data access performance of the whole network A Least Recently Used cache replacement method is use for replacing the data from the buffer of caching nodes, once the buffer is filled the caching nodes cache the data generated by source node and forwards the data to other caching nodes. A requester node broadcasts the data query to the neighbors and a caching node replies the query. Simulation results show the efficacy of the proposed approach in terms of query successful ratio.