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Due to the growing interest in accessing the Internet, it is an important requirement to consider the integration of MANET with the Internet. Thus, to put the MANET technology into the context of real life, we consider an Internet based MANET, called IMANET [1], and investigate the problem of information search and access under this environment. An IMANET consists of a set of MTs. The MTs communicate with each other with ad hoc communication protocols. Among the MTs, some of them can directly connect to the Internet, and thus serve as AP for the rest of MTs in the IMANET. Thus, an AP is a gateway for the Internet and is assumed to have access to any information.

Although there may exist many potential applications, none of the previous work has addressed the constraints in IMANET. First, not all the MTs can access the Internet. Second, due to MTs' mobility, a set of MTs can be separated from the rest of the MTs and get disconnected from the Internet. Finally, an MT requiring multi-hop relay to access the Internet may incur a longer access latency than those which have direct access to the Internet. To address these constraints, we propose an aggregate caching mechanism for IMANET. The basic idea is that by storing data items in the local cache of the MTs, members of the IMANET can efficiently access the required information. Thus, the aggregated local caches of the MTs can be considered as an unified large cache for the IMANET. In addition, since information search in IMANET is different from the search engine based approach on the wired Internet, we propose a broadcast based approach, called Simple Search (SS) algorithm, which can be implemented on the top of existing routing protocols, to locate the requested data items. As part of the aggregate cache, a cache admission control policy and a cache replacement policy, called Time and Distance Sensitive (TDS) replacement, are developed to reduce the cache miss ratio and improve the information accessibility.

We conduct a simulation based performance evaluation to observe the impact of caching, cache management, and access points (which are directly connected to the Internet) upon the effectiveness of IMANET. The overall results show that the proposed methodology can relieve limitations of IMANET and improve system performance significantly.

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Sunho Lim