Caching for mobile clients in broadcast environments

Abstract

In the mobile wireless computing environment of the future a large number of users equipped with low powered palmtop machines will access the database over the wireless communication channels. So the challenges ensuing from the asymmetric communication capabilities of mobile environment have led to an increased interest in broadcast-based data dissemination. To enforce serializability in broadcast environment, we have evaluated two existing concurrency control protocols in this project; which are BCC-TI and Quasi-TI protocols. BCC-TI is a protocol that allows dynamically adjusts the position of the read-only transactions in the current serialization order by recording the timestamp intervals [2]. And the Quasi-TI is an enhanced the BCC-TI protocol that is based on quasi-caching constraints [1]. We demonstrate that the Quasi-TI protocol has a better performance than the BCC-TI protocol. Also, caching of frequently accessed data items will be an important technique that will reduce contention on the narrow bandwidth wireless channel [1, 4, 5, 7]. In this project, we have evaluated two caching schemes, which are P-caching and PIT-caching schemes. Through simulation, we demonstrate that caching improves the query response time in both BCC-TI and Quasi-TI protocols. Furthermore, we have further evaluated two traditional cache replacement schemes in broadcast environment and compared their performance with P-caching and PIT-caching schemes.