Mobile computing environments are characterized by slow wireless links and relatively underprivileged hosts with limited battery powers, predisposed to frequent disconnections. Caching data at the hosts in a wireless network helps alleviate problems associated with slow, limited bandwidth wireless links, by reducing latency and conserving bandwidth.
Battery power is conserved by reducing the number of uplink requests. A mobile computing environment is a distributed system, thus when data at the server changes, the client hosts must be made aware of this fact in order for them to invalidate their cache otherwise the host would continue to answer queries with the cached values returning incorrect data.
The nature of the physical medium coupled with the fact that disconnections from the network are very frequent in mobile computing environments demands a cache invalidation strategy with minimum possible overheads.
In this paper we propose a scheme for cache invalidation which requires maintaining information about what is cached at each client at the server. Server initiated updates are sent to the clients when the data changes at the server. We show that the average latency and throughput increase by using this strategy at the cost of a few additional uplink requests. The cache continues to be valid even after arbitrarily long disconnections from the network.
We provide analytical comparison between our proposed scheme and the existing scheme for cache management. Extensive experimental results are provided to compare the schemes with respect to performance metrics like latency, number of uplink requests etc. both under high and low rate of change of data at servers.
Source: The Pennsylvania State University
Author: Sumit Khurana, Anurag Kahol, Sandeep K. S. Gupta, and Pradip K Srimani