Research On Energy Saving Strategies In Network Layer In Wireless Sensor Networks

A Wireless Sensor Network (WSN), consisting of a large number of small sensor nodes with sensing, computing, and communication capabilities, recently received tremendous attention from both academia and industry because of its promise of a wide range of potential applications in both civil and military areas. It is declared as one of the most important technologies for the 21st century.The wireless sensor nodes are often only equipped with limited power resources, and it is very hard to change and recharge. In order to increase the system lifetime, it is crucial to develop an energy-efficient routing protocol in the design of the WSN. Since many differences are existed between the WSN and the other traditional wireless networks, the routing protocols in those wireless networks cannot simply be transplanted to the design of the WSN. This brings new challenges and pressures to the routing technologies for WSN in the following issues:The problem of energy distribution. The relaying burden is not the same for all the nodes, which will incur the different energy consumption for each node. It is necessary to switch some traffic on the critical nodes or critical paths that will greatly affect the system performance to some other nodes or some other paths, this can achieve energy distribution and increase the system lifetime. Node switching and multipath methods are the main solutions to the problem of energy distribution in the present, but they all have not carefully considered the problems of the resource usage and the switching complexity.The QoS routing strategy. With the development of the science and technology and the requirement of the applications, the WSN must meet a certain QoS requirement in some areas. Most routing protocols in WSN only consider the reachability and energy efficiency, though some protocols have provided some QoS metric, they are far away from perfect. So studying and developing a routing protocol to meet some certain QoS requirement is important to ensure efficient usage of the sensors and effective access to the gathered measurements.Topology analysis. Two main architectures are existed in the WSN: flat and hierarchical. The latter one gains much attractive for the reason of scalability, management and energy efficiency. Many methods for selecting the cluster headers are presented, but they don't pay a critical attention to the overhead during the role rotations. And they decide the beginning of a new round by some constant experimental periodical time which cannot adjust according to the actual working state. So it is necessary to develop an adaptive clustering formation based on the actual network situation. To solve the above problems, this paper addresses on the energy-constrained routing technologies in the WSN. The contents of this thesis include the following issues: (1) an energy-aware load-balancing multipath delivery strategy; (2) an efficient energy distribution scheme; (3) a real-time routing protocol in the sensor network; (4) adaptive minimum rotational cost for cluster formation in sensor networks. The work in this thesis has been supported by the National Science Foundation of China under contract No.60572049 and the Natural Science Foundation of Hubei Province, China under contract No. 2005ABA264.The contributions of this thesis include:1. Multipath delivery scheme based on Decisive Energy Ratio: Propose a multipath delivery scheme based on Decisive Energy Ratio (DER) and DER with Overload Avoidance (DEROA). It can effectively achieve energy-awareness and load-balancing.2. Maximum relay energy distribution strategy: Critically analyze the relay energy consumption and point out the nodes one hop to the sink will affect the system lifetime prominently. Propose an efficient Maximum Relay Energy Distribution (MRED) strategy which can prolong the system's lifetime without partitioning.3. Energy-aware real-time routing protocol for sensor networks: Introduce a novel concept of Effective Transmission (ET) to limit the forwarding candidate area. The end-to-end delay requirement is separated into the sum of each link's Constrained Equivalent Delay (CED), which can simplify the route discovery process. An energy-aware real-time routing protocol for sensor network is proposed.4. Adaptive minimum rotational cost for cluster formation strategy: Putforward a method to adaptively minimize the rotational cost and reduce the rotational overhead. It combines the dynamic and static advantages in the selection of the cluster head and ensures the flexibility of the hierarchical architecture.