OPTIMAL MEMORY MANAGEMENT STRATEGIES FOR A MOBILE USER IN A BROADCASTDATA DELIVERY SYSTEM

Recently, data broadcasting has been considered as a promising way of disseminating information to a massive number of users in a wireless c ommunication environment. In a broadcast data delivery system, there i s a server which is broadcasting data to a user community, Due to the lack of communication from users to the server, the server cannot know what a user needs, In order to access a certain item, a user has to w ait until the item appears in the broadcast, The waiting time will be considerably long if the server's broadcast schedule does not match th e user's access needs, If a user has a local memory, it can alleviate its access latency by selectively prefetching the items from the broad cast and storing them in the memory, A good memory management strategy can substantially reduce the user's access latency, which is a major concern in a broadcast data delivery system, In this paper, an optimal memory management policy is identified that minimizes the expected ag gregate latency, We present optimal memory update strategies with limi ted lookahead as implementable approximations of the optimal policy, S ome interesting special cases are given for which the limited look-ahe ad policies are optimal. We also show that the same formulation can be used to find the optimal memory management policy which minimizes the number of deadline misses when users generate information requests wh ich have to be satisfied within some given deadlines.