Efficient and accurate techniques for cooperative localization in wireless sensornetworks

  • Ahmed Rashed Kulaib AlTunaiji

Student thesis: Doctoral Thesis

Abstract

Wireless Sensor Networks (WSNs) consist of a group of sensor nodes that can communicate using radio signals. Each node consists typically of a transceiver, microcontroller, memory, one or more sensors, and a power source. The size and cost of sensor nodes have decreased significantly, making it possible to build and embed large scale WSN that covers a substantial area, such as a complete city. WSNs have a wide range of civilian and military applications, including health systems, environmental monitoring, and habitat monitoring, as well as target tracking and localization. The localization process is an important aspect of WSNs as it provides the necessary information to deliver position-dependent applications. Basically, the localization process involves computations based on the received signals to determine the physical coordinates of a group of sensor nodes. This process is important as the accuracy of subsequent data analysis and decisions based on it can be degraded due to the lack of reliable location information. This thesis addresses the factors that need to be considered when selecting a localization algorithm. It discusses the advantages and limitations of the various localization techniques and the particular challenges associated with localization in WSNs. Algorithms that can be used to localize sensor nodes can be classified into centralized and distributed, depending on where the computation effort is carried out. This thesis reviews the major localization techniques in each category and sets the direction that is taken to achieve the overall thesis goal. The thesis aims to develop algorithms that can accurately localize sensor nodes in real-time with low computational requirements, and robustly adapt to environmental changes. Computational complexity and signaling overhead are important aspects of the algorithm development as the computational power of the processors in sensor nodes is normally limited. The thesis mainly focuses on distributed algorithms as they are considered more computationally efficient than centralized algorithms, particularly for sensor networks that have limited resources. Algorithms that use Direction of Arrival (DoA) and Time Difference of Arrival (TDoA) methods are of particular interest. This is due to the accuracy of these localization algorithms, and their ability to be scaled to a multitude of applications. WSN localization algorithms can also be categorized into Range-Based and Range-Free positioning algorithms. Range-Based include DoA and Received Signal Strength (RSS), while Range-Free include Distance Vector(DV)-hop algorithm. A novel uniform circular displaced sensor array (UC-DSA) configuration is proiposed for estimating the DoA of multiple signals using MUltiple SIgnal Classification (MUSIC) algorithm. Numerical comparative study shows that the UC-DSA outperforms other configurations including uniform linear displaced sensor array (UL-DSA), uniform circular arrays (UCA), and Uniform Linear Array (ULA) configurations. The proposed UC-DSA configuration has several advantages that include reduced computational complexity and resolving coherence problem without the need for spatial smoothing or other techniques. A hybrid technique that combines RSS and DoA has been implemented and verified. Combining RSS and DoA provides several advantages making it outperform algorithms that uses only RSS technique. For example, a hybrid node is capable of localizing another node by itself without any assistance from other nodes, and provides a higher localization accuracy when compared to nodes that only use RSS. Distance Vector(DV)-hop algorithm is a Range-Free positioning algorithm based on distance vector routing and GPS positioning principle. The DV-hop advantage over Range-based positioning algorithm is its low computational complexity. Increasing the accuracy of DV-hop algorithm without increasing the computational complexity significantly was a target in this thesis. A new modified DV-hop has been developed in order to increase the localization accuracy. The new technique consists of two main stages. The first stage is the traditional DV-hop, while the second stage, starts by finding the center of the localized nodes with error, and then determine the radius based on the further node from the center. After that, the information available is used to either move anchor nodes on the circumference of the circle or localize nodes which are close to the circumference of the circle using DoA nodes and then turn them into anchors so that they can be used to localize the rest of the normal nodes. This technique is inspired by the effectiveness of anchors combination theory.
Date of Award2014
Original languageAmerican English
SupervisorRaed Shubair (Supervisor)

Keywords

  • Efficient and accurate techniques for cooperative localization in wireless sensor networks

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