Concurrency Control Using Timestamp Ordering in Broadcast Environments

In the near future, tens of millions of users will have access to distributed information systems through the wireless interface in their mobile computers. The physical characteristics of the wireless medium pose new challenging issues on data consistency of transaction processing in wireless environments. In particular, the monetarily expensive wireless bandwidth and the asymmetric communication between the mobile clients and the server bar the applicability of conventional transaction processing techniques. In this paper, we first propose a concurrency control protocol in wireless environments that is adapted from the optimistic concurrency control with forward validation protocol. The protocol offers autonomy between the mobile clients and the server such that the mobile clients can read consistent data off the air without contacting the server. To reduce the number of unnecessary transaction restarts such that the timeliness of mobile transactions can be enhanced, we propose another protocol based on timestamp ordering that can show significant performance improvement. The timestamp ordering technique enjoys a number of benefits from the separate processing and flexible adjustment of serialization order by exploiting the semantics of read-only transactions. Most of the existing applications, such as information dispersal systems for stock prices, weather information and traffic condition updates, are comprised of read-only transactions. The simulation results confirm that the proposed protocol could be an efficient and effective approach to transaction processing in real-time broadcast environments for meeting transaction deadlines.