Organization of Invalidation Reports for Energy-Efficient Cache Invalidation in Mobile Environments

Abstract

In a wireless environment, mobile clients often cache frequently accessed data to reduce contention on the limited wireless bandwidth. However, it is difficult for clients to ascertain the validity of their cache content because of their frequent disconnection. One promising cache invalidation approach is the Bit-Sequences scheme that organizes invalidation reports as a set of binary bit sequences with an associated set of timestamps. The report is periodically broadcast by the server to clients listening to the communication channel. While the approach has been shown to be effective, it is not energy efficient as clients are expected to examine the entire invalidation report. In this paper, we reexamine the Bit-Sequences method and study different organizations of the invalidation report to facilitate clients to selectively tune to the portion of the report that are of interest to them. This allows the clients to minimize the power consumption when invalidating their cache content. We conducted extensive studies based on a simulation model. Our study shows that, compared to the Bit-Sequences approach, the proposed schemes are not only equally effective in salvaging the cache content but are more efficient in energy utilization.