Managing concurrent execution of transactions in mobile ad-hoc network database systems: an energy-efficient approach

A Mobile Ad-hoc Network (MANET) is a collection of mobile, wireless and battery-powered nodes without any fixed infrastructure. Therefore, it fits well in mission-critical applications such as disaster rescue and military operations. However, when a node runs out of energy, communication may fail and transactions may be aborted if they are time-critical and miss their deadlines. In order to provide timely and correct results for multiple concurrent transactions, energy-efficient database concurrency control (CC) techniques become critical for database systems built for MANET. Due to the characteristics of MANET databases, existing CC algorithms cannot work effectively. In this paper, an energy-efficient CC algorithm is developed for mission-critical MANET databases in a clustered network architecture where nodes are divided into clusters, each of which has a cluster head, responsible for the processing of all nodes in the cluster. The cluster structure is constructed using a novel weighted clustering algorithm, which uses node mobility, remaining energy and workload to group nodes into clusters and select cluster heads. In our CC algorithm, we elect cluster heads to work as coordinating servers to conserve energy and balance energy consumption among servers, and propose an optimistic CC algorithm to offer high concurrency and avoid wasting limited system resources. Besides correctness proof and theoretical analysis, comprehensive simulation experiments were conducted, and simulation results show the superiority of our CC algorithm over existing techniques in terms of transaction abort rate, total energy consumption by all servers, and degree of balancing energy consumption among servers.