PETRANET College of Engineering

This material is based upon work supported by the National Science Foundation under Grant No. 0312746. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).


Project Summary

Advances in connectivity and wireless communications have revolutionized the computer industry. Connectivity has enabled software available on independent systems at different locations to cooperate in order to provide a wider spectrum of services to users. Wireless communication technology makes it possible to extend these services to nomadic users. Together, connectivity and wireless communications expand the horizons of the computer realm. These developments have influenced the Database arena as well. Multidatabase systems - a set of autonomous database systems that cooperate to provide an extended set of services to users - are a result of connectivity. The advances in wireless communications demand that the services provided to static users by multidatabase systems be extended to mobile users - henceforth referred to as Mobile MultiDataBase Management Systems (MMDBMS).

Transaction Management is a vital component of any MMDBMSs. The Transaction Manager is responsible for providing reliable and consistent units of computing to its users. Mobile users are characterized by frequent disconnection and migration. These both impact transaction processing and management. Much research in the area of mobile database transaction management was based on the general mobile computing architecture where fixed Mobile Support Stations (MSSs) are connected to a fixed network, and each fixed MSS is responsible for all mobile hosts (MHs) roaming in its own cell. None of the research has considered an ad-hoc mobile network architecture where there are no fixed MSSs, all servers/clients are MHs, and the network that interconnects these MHs is a wireless network with a frequently changing topology. This kind of architecture is widely used in battlefields and in disaster recovery situations where it is difficult or not feasible to depend on a static wired communication infrastructure. Moreover applications like battlefields are time-critical which require that their transactions be executed not only correctly but also within their deadlines. So the Transaction Manager at the MH where the database is stored has to consider the mobility of the submitting MHs as well as the deadlines of the transactions. Another important issue in ad-hoc networks is power or energy restriction on MHs because MHs are not connected to direct power supplies and many of them are small and low-power devices. Therefore energy-efficient solutions are needed for this environment.

The PETRANET (Power Efficient Transaction Management Technique for Real-time Mobile Ad-hoc Network Databases) project increases power efficiency, considers real-time constraints, and operates in a mobile environment. This technique is aimed at reducing the overall energy consumption and providing a balance in individual MH energy consumption, while at the same time reducing the number of transactions that must be aborted due to deadline violations. It considers both firm real-time and soft real-time transactions, and three modes that an MH can be in: active, doze, and sleep. It treats time as the most important factor in handling firm transactions while energy as the most important factor in handling soft transactions. It uses this principle to locate MHs, schedule transactions, and commit/abort transactions. Disconnections are handled by aborting the transaction. A prototype has been developed to evaluate the performance of the proposed technique for two real-life applications, military operations and fire rescue applications, and to provide guidelines to assist both users and designers. This prototype has been demonstrated at the 2006 IEEE International Conference on Data Engineering in Atlanta, Georgia.

The research results allow users to query real-time and non real-time distributed databases in a mobile ad-hoc network environment. This makes it feasible for military, rescue personnel, students and business associates to use distributed databases in situations where it is not possible to setup a wired network.

The prototype and the real-life applications are available here.