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Research On Data Gathering Strategies In Mobility-assistant Wireless Sensor Networks

Posted on:2013-01-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:X W ZhangFull Text:PDF
GTID:1118330371486849Subject:Computer software and theory
Abstract/Summary:PDF Full Text Request
Data gathering in wireless sensor networks by employing mobile data collectors (MDCs) can greatly reduce the relay hops among sensors and then prolong the lifetime of whole network for the energy saving at sensor nodes. However, new challenges are aroused for the mobility of MDCs in data gathering which is different from static wireless sensor networks. In this paper, we focus on the mobility-assisted data gathering schemas in wireless sensor networks. The main contributions of our work include the following:The first part of the work committed to optimizing the movement path of the MDC. Under normal circumstances, the limited speed of MDC is far less than the speed of wireless transmission, so there is a tradeoff between the energy consumption and data transmission delay. All the sensors send the data to some nodes which cached these data and transmit to the MDC when it is nearby. These cached nodes are called rendevous points (RPs) and they construct the trajectory of MDC. In order to select the optimal rendevous points, we proposed a heuristic algorithm based on the priority of sensor nodes. Furthermore, according to the uncertainty of data sensing, we presented a probabilistic path selection algorithm. The evaluation results show that our algorithms can shorten the trajectory of MDC effectively as well as satisfy the data gathering quality.The second part of our work is concerning routing update issues in real-time applications. The data transmission routings between sensors and Sinks are dynamically changed due to the mobility of MDC (here mainly refers to mobile Sink), so the sensors should update their route information in time in order to keep a data forwarding path. We proposed an adaptive real time local route upating algorithm in which we change the sensor's data forwarding route according to ratio between the lengths of original route to new point of MDC and optimal route after MDC moving. If the ratio is larger than the threshold given by application, the old route of sensor is changed to optimal route, otherwise the sensor use original route to original point of MDC and then data is transferred to new point. The simuations show the power consumption can be controlled by select the threshold properly.Sleep/wake scheduling is an effective mechanism to prolong the lifetime of these energy-constrained wireless sensors. However, sleep/wake scheduling could result in substantial discovery delays because the sensor needs time to receive the beacon-ID signals when MS entered its communication range. In the third part, we first study on the mobile sink discovery mechanism and the factors which affect the efficiency of data collection. Based on this result, we then provide a solution to the control problem of how to optimally adjust the system parameters of the sleep/wake scheduling protocol to maximize the network lifetime, subject to a constraint on the expected residual contact time. Our numerical results indicate that the proposed solution can balance the network consumption, especially in a sparse sensor networks.In forth part we introduce the design and implementation of a mobile sink node based on ARM9core chip, named DataTruck, which has a large storage and rapid speed. Furthermore, we integrated a smart antenna system to collect the data from multiple static nodes concurrently which using the same frequency. We consider applying space-division multiple access (SDMA) technique to data gathering by equipping the DataTruck with two antennas. With SDMA, two distinct compatible sensors may successfully make concurrent data uploading to the DataTruck. Experiments show that DataTruck can collect data efficiently and reduce the average data delay by using SDMA technology.Finally, we make a conclusion of our work and discuss the further research issues on data gathering schemes for mobility-assistant wireless sensor networks.
Keywords/Search Tags:wireless sensor networks (WSNs), mobility-asisstant, data gathering, pathselection, real-time routing, local routing update, duty-cycles, SDMA, compatiblenodes
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