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Internet-based vehicular ad hoc network (IVANET) is an emerging technique that combines a wired Internet and a vehicular ad hoc network (VANET) for providing universal information and service accessibility. A key design optimization technique in IVANETs is to cache the frequently accessed data items in a local storage of vehicles. Since vehicles are not critically limited by the storage/memory space and power consumption, cache replacement scheme for accommodating new data items is not an issue. Rather, a more critical design question is how to keep the cached copies valid or to invalidate them when the original data items are updated. This is particularly important in IVANETs, where vehicles move very fast. This paper proposes state-aware cooperative cache invalidation (CCI) scheme and its enhancement (ECCI) that take advantage of the underlying location management mechanism. Extensive performance study shows that the proposed schemes can reduce the query delay as much as 69% and increase the cache hit rate up to 57% in comparison to two existing cache invalidation techniques, called poll-each-read (PER) and extended asynchronous (EAS). Note that PER and EAS have been modified to work in IVANETs.
Date of Conference: 3-6 Aug. 2009