Replication of data associated with locations in ad hoc networks

It is difficult to retain accessibility to data on other hosts in ad hoc networks because of disconnections caused by movements of hosts. This fact affects the practical use of ad hoc networks. When important data are operated on ad hoc networks, it is demanded to retain accessibility to the data from users even if there are disconnections between mobile hosts. Hara (2001) has proposed some methods for allocating replicas on ad hoc networks for achieving high accessibility to data objects shared by multiple hosts. The methods are based on an assumption that all hosts on the network know the probabilities of data access to each object and the probabilities do not change. In this paper, we handle a case that the probability of data access from each host change with time and its location. We propose a method to enhance the accessibility to data that are associated with locations and used frequently by hosts that are close to the location. We assume data object is accessed by geocast. Such kind of data will be used in personal navigation systems, systems handling virtual objects overlaid on to the real world like Space Tag and cooperative work for disaster relief etc.