Research On Coverage Of Randomly Deployed Wireless Sensor Networks In Shadow Fading Environment

Coverage is one of the basic problems of wireless sensor network. It’s expectedto maximize the network coverage area under the premise of guaranteeing a certainquality of service by deploying or scheduling the sensor nodes. If all nodes are in aworking state at the same time, it can provide maximum coverage in the simplest way.However, this method will cause a lot of energy waste resulting in reducing networklifetime.One of the core issues of network coverage is how to ensure adequate coveragewhile achieving the maximum network lifetime. Many scholars study the issues, butthey generally use the idealized model (Boolean disk model). This simplified modelignores the random nature of wireless channel. Shadow fading effect caused byobstructions can not be ignored in wireless communications engineering design. Thephenomenon is still not aroused enough concern and attention in research on coverageof wireless sensor networks. So, in order to analysis the relationship between theshadow fading effects and network coverage, to guide the design and implementationof sensor networks, this paper study how the effects of shadow fading affect networkcoverage through theoretical analysis and experimental. After that we focus on thenode scheduling and coverage control algorithms, and present a energy-efficientcoverage control algorithm, based on more realistic model of the probability coverage.The main tasks are:(1) The paper introduces the characteristics of the shadow fading environment,and analyzes the lognormal model of shadow fading in details. After that, theimportance of researching on the network’s connectivity problems in shadow fadingenvironment are discussed.(2) First reasonable assumptions about the network model are proposed. Usingthe point coverage concept, the paper deduces by theory that in the wireless sensornetworks whose sensor nodes are randomly deployed according to the same Poissonprocess, the shadow fading effect can help improving network’s coverage to someextent. After that, we design simulation with Matlab. The experimental results furtherconfirm the correctness of the conclusion.(3) Concerning about the Wireless Sensor Networks’ node-scheduling strategy, aenergy-efficient coverage control algorithm(ECAP) is presented, based on the morerealistic model of probability coverage. The algorithm applies to a limited target point monitoring problems, it use the heuristic greedy strategy, selecting the nodes with thehigher energy and making more contribution to the probability of detection of targetset to construct cover set. It improves energy efficiency and prolongs the lifetime ofthe networks to2-4life cycle on average. By comparing the number of active nodes inseveral experiments, simulation results show that the algorithm constructs cover setwith a good stability.