In this paper, we extend our previous work on content retrieval in Disruption Tolerant Networks (DTNs) to support cooperative caching. Our caching scheme can adapt to the unstable network topology in DTNs, and enable the sharing and coordination of cached data among multiple nodes to reduce data access latency. Our key idea is to cache data at cluster head nodes that have the highest social levels, and thus receive many content requests.

Furthermore, to reduce the caching overhead at central nodes and to bring data closer to the content requesters, we use multiple caching nodes along the content request forwarding path. Lastly, we propose a new cache replacement policy that considers both the frequency and recency of data access. Simulations in the NS-3 environment show that our caching scheme significantly improves the performance of content retrieval in DTNs.

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