Guaranteed and consistent mobile transactions in broadcast environment

Abstract

Wireless data broadcast allows a large number of users to retrieve data simultaneously in mobile databases, resulting in an efficient way of using the scarce wireless bandwidth. The efficiency of data access methods, however, is limited by an inherent property that users can only access data strictly sequential. In a wireless broadcast environment, mechanisms to efficiently transmit information to mobile clients are of significant interest. For instance, a satellite or a base station to communicate information of common interest to mobile clients could use such mechanisms. Broadcast based delivery is important for a wide range of applications that involve dissemination of information to a large number of clients. Dissemination-based applications include information feeds such as stock trading and sport tickets, electronic newsletters, mailing lists, banking and traffic management systems. In such applications, if there is a client waiting for a data item, the client will get the data item from the air while the server is broadcasting it. Thus, the cost for data dissemination is independent of client number since a data broadcast can satisfy multiple clients waiting for the same data item, resulting in a much more efficient way of using the bandwidth. This project work is the fresh approach to query optimization for reducing transaction response time significantly in wireless data broadcast. This is based on the philosophy that a client should take a more active role in maintaining its transactions consistency in an asymmetric communication environment. One way to ensure the consistency of read-only transactions is to abort transactions that read data values that correspond to different database states. However, this kind of abort-based methods leads to intolerable transaction abort rate in case of intensive updates at the server. The server constructs concurrency control information, which is used by a mobile transaction to identify its descendant transactions. The concurrency control information is broadcasted at the beginning of each bicycle, ahead of the data items. More specifically, view consistency is characterized by the notion that each read-only transaction is serializable with respect to the update transactions from which it reads directly or indirectly. View consistency provides guaranteed data dissemination among the mobile clients.