Distributed caching and broadcast in a wireless mobile computing environment

In a mobile computing system, the wireless communication bandwidth is a scarce resource that needs to be managed carefully. In this paper, we investigate the use of distributed caching as an approach to reduce the wireless bandwidth consumption for data access. We find that conventional caching techniques cannot fully utilize the dissemination feature of the wireless channel, We thus propose a novel distributed caching protocol that can minimize the overall system bandwidth consumption at the cost of central processor unit processing time at the server side. This protocol allows the base station to select data items into a broadcast set, based on a performance gain parameter called the bandwidth gain, and then send the broadcast set to all the mobile computers within the server's cell. We show that, in general, this selection process is NP-hard and therefore, we propose a heuristic algorithm that can attain a near-optimal performance. We also propose an analytical model for the protocol and derive closed-form performance measures, such as the bandwidth utilization and the expected response time of data access by mobile computers. Experiments show that our distributed caching protocol can greatly reduce the bandwidth consumption so that the wireless network environment can accommodate more users, and at the same time vastly improve the expected response time for data access by mobile computers.