AN ENERGY-EFFICIENT CONCURRENCY CONTROL ALGORITHM FOR MOBILE AD-HOC NETWORK DATABASES

With the rapid growth of the wireless networking technology and mobile computing devices, there is an increasing demand for processing mobile database transactions in mission-critical applications such as disaster rescue and military operations that do not require a fixed infrastructure, so that mobile users can access and manipulate the database anytime and anywhere. A Mobile Ad-hoc Network (MANET) is a collection of mobile, wireless and battery-powered nodes without a fixed infrastructure; therefore it fits well in such applications. However, when a node runs out of energy or has insufficient energy to function, communication may fail, disconnections may happen, execution of transactions may be prolonged, and thus time-critical transactions may be aborted if they missed their deadlines. In order to guarantee timely and correct results for multiple concurrent transactions, energy-efficient database concurrency control (CC) techniques become critical. Due to the characteristics of MANET databases, existing CC algorithms cannot work effectively.In this dissertation, an energy-efficient CC algorithm, called Sequential Order with Dynamic Adjustment (SODA), is developed for mission-critical MANET databases in a clustered network architecture where nodes are divided into clusters, each of which has a node, called a cluster head, responsible for the processing of all nodes in the cluster. The cluster structure is constructed using a novel weighted clustering algorithm, called MEW (Mobility, Energy, and Workload), that uses node mobility, remaining energy and workload to group nodes into clusters and select cluster heads. In SODA, in order to conserve energy and balance energy consumption among servers so that the lifetime of the network is prolonged, cluster heads are elected to work as coordinating servers. SODA is based on optimistic CC to offer high transaction concurrency and avoid unbounded blocking time. It utilizes the sequential order of committed transactions to simplify the validation process and dynamically adjusts the sequential order of committed transactions to reduce transaction aborts and improve system throughput.Besides correctness proof and theoretical analysis, comprehensive simulation experiments were conducted to study the performance of MEW and SODA. The simulation results confirm that MEW prolongs the lifetime of MANETs and has a lower cluster head change rate and re-affiliation rate than the existing algorithm MOBIC. The simulation results also show the superiority of SODA over the existing techniques, SESAMO and S2PL, in terms of transaction abort rate, system throughput, total energy consumption by all servers, and degree of balancing energy consumption among servers

Adaptive search in mobile peer-to-peer databases

Information is stored in a plurality of mobile peers. The peers communicate in a peer to peer fashion, using a short-range wireless network. Occasionally, a peer initiates a search for information in the peer to peer network by issuing a query. Queries and pieces of information, called reports, are transmitted among peers that are within a transmission range. For each search additional peers are utilized, wherein these additional peers search and relay information on behalf of the originator of the search

Managing Data Replication in Mobile Ad-Hoc Network Databases

A Mobile Ad-hoc Network (MANET) is a collection of wireless autonomous nodes without any fixed backbone infrastructure. All the nodes in MANET are mobile and power restricted and thus, disconnection and network partitioning occur frequently. In addition, many MANET database transactions have time constraints. In this paper, a Data REplication technique for real-time Ad-hoc Mobile databases (DREAM) is proposed that addresses all those issues. It improves data accessibility while considering the issue of energy limitation by replicating hot data items at servers that have higher remaining power. It addresses disconnection and network partitioning by introducing new data and transaction types and by considering the stability of wireless link. It handles the real-time transaction issue by replicating data items that are accessed frequently by firm transactions before those accessed frequently by soft transactions. DREAM is prototyped on laptops and PDAs and compared with two existing replication techniques using a military database application. The results show that DREAM performs the best in terms of percentage of successfully executed transactions, servers’ and clients’ energy consumption, and balance of energy consumption distribution among servers

TriM: Tri-modal data communication in mobile ad-hoc network database systems.

The Mobile Ad-hoc Network (MANET) is an emerging area of research in the network and database communities. A MANET is a group of self-organizing, autonomous clients and servers that form temporary networks. A MANET allows three methods of data communication. These are: data broadcast, data query and peer-to-peer communication. The primary research in this area has been in MANET routing. Node mobility, disconnection, battery power and limited bandwidth form the constraints for MANET data communication research.TriM was designed to accommodate disconnection and reconnection to the network through periodic synchronization. Data communication was designed to provide contention free data broadcast. Each part of the protocol was designed with minimum power consumption as a goal.Simulation showed TOM minimized the average power consumption of servers and clients while accommodating node disconnection. The research also demonstrates the transmission ranges needed to get acceptable performance in large regions where the number of servers is limited. Simulation was also used to compare TriM to Gruenwald's Leader Selection protocol. This comparison showed TriM operated at similar and lower average power consumption rates while providing a greater range of data communication methods. Analysis of TriM demonstrated the benchmark was capable of accurately predicting the simulation performance of TriM under a wide range of scenarios.The objective of this research is twofold. First, a MANET data communication protocol, TriM (for Tri-Modal Communication), capable of providing all three methods of data communication in a single network is designed. This is the first MANET protocol capable of providing all three methods of MANET data communication. Second, a benchmark capable of evaluating MANET data communication protocols is developed. This is the first benchmark developed for the MANET environment.The developed benchmark has three parts. These are a standard MANET architecture, data communication workload and evaluation criteria. This benchmark allows the evaluation and comparison of MANET data communication protocols and is used to evaluate TriM

The usability of knowledge based authentication methods on mobile devices

Mobile devices are providing ever increasing functionality to users, and the risks associated with applications storing personal details are high. Graphical authentication methods have been shown to provide better security in terms of password space than traditional approaches, as well as being more memorable. The usability of any system is important since an unusable system will often be avoided. This thesis aims to investigate graphical authentication methods based on recall, cued recall and recognition memory in terms of their usability and security