Approaches for broadcasting temporal data in mobile computing systems

Rapid advances in mobile communication technology have spawned many new mob ile applications. A key element in many of these systems is the need to dis tribute real-time information from a database server to mobile clients. Whi le data broadcast has been shown to be an efficient data dissemination tech nique, many issues such as selection of broadcast data and caching strategi es at mobile clients are still active research areas. In this paper, we con sider an important characteristic of many mobile computing systems which ha s often been ignored in the design of broadcast algorithms: the fact that m any data items are associated with temporal constraints on their validity. We introduce the notion of absolute validity interval (AVI) to capture the temporal constraints of the data items, formulate a temporal data model and examine both static and dynamic approaches to select data items based on t heir access frequencies as well as their AVI. The reason for considering th e AVI of the data items in broadcast selection is to increase the client ca che hit probability so that the access delay for a data item will be much r educed. Based on the results from extensive simulation experiments, it is c oncluded the AVI-based approaches, by improving cache hit probability, can significantly improve the mean response time and reduce the number of deadl ine missing requests. (C) 2000 Elsevier Science Inc. All rights reserved.