Bandwidth Aware Cache Invalidation in Error Prone Wireless Mobile Environments

The IR-UIR based approach for cache invalidation is an attractive solution for reducing the query delay where data changes frequently. However, it achieves this by increasing the frequency of replication resulting in consumption of large amount of bandwidth. Bit sequencing approach proposed to address the problem of long disconnection cannot be used in this scenario as even a single bit error would collapse the entire hierarchy and also the UIRs are very short reports, which contain very less data items. In this paper, we propose to use hashing techniques to represent the data items so as to reduce the bandwidth requirements. Using hashing we divide the data items into different groups called buckets. By using the hash key of a bucket the data items in that bucket are represented using less number of bits than is actually required. Since data items are to be accompanied by the time at which they are modified, we reduce the number of bits required to represent time by using the amount of time elapsed since the data item is modified. Detailed mathematical analysis and simulation experiments are carried out to evaluate the proposed methodology. Compared to the previous methods our solution not only requires less bandwidth but also performs well in erroneous environments