Wireless Ad Hoc Networks, Energy-saving Related To A Number Of Key Issues

The advances in mobile devices and wireless communication technology have enabled a new communication paradigm: wireless ad hoc network. A wireless ad hoc network is a multi-hop, self-organized wireless network where the communication of mobile nodes can be done without the support of any fixed infrastructure.A lot of new issues and challenges have arised due to the nature of wireless ad hoc networks. These issues include routing, application and middleware, energy management, security and cooperation etc. Among these issues, energy management is one of the most challenging cross-layer problems that should be fully investigated.This dissertation addresses energy-related key problems in wireless ad hoc networks. The main contributions are summarized as following:Firstly, this dissertation deals with the problem of making existing lifetime-aware routing algorithms in ad hoc networks achieve their design objectives in the presence of selfish nodes. Several lifetime-aware routing algorithms have been developed before to maximize the lifetime of ad hoc networks. But these algorithms have an implicit assumption that nodes are cooperative and truthful, and they cannot work properly in the face of selfish nodes. Motivated by algorithmic mechanism design, this dissertation proposes two truthful mechanisms SMM and SMM-VCG, and presents a lifetime-aware routing algorithm Ad hoc-SMM that copes with the selfish nodes by using the proposed meachnisms. The basic idea of the mechanisms is giving appropriate payment to stimulate the cooperation of nodes, and cheating can not increase or even lose the utility. The experiment results show that the payment ratio is relatively small and stable due to the nature of lifetime-aware routing algorithms.Secondly, this dissertation deals with the problem of maximizing the lifetime of a sensor network to gather more information from environment. Most existing works lack formal analysis and the corresponding algorithms are not well optimized. This dissertation theoretically investigates the maximum lifetime data gathering problem from two aspects: static routing scheme and dynamic routing scheme. It also proposes a near optimal maximum lifetime data gathering and aggregation algorithm MLDGA, which tries to minimize the total energy consumption in each round as well as maximize the lifetime of a routing tree used in the round. The simulation results show that MLDGA performs well regardless of base station location and initial battery energy levels of sensors.