Optimized hybrid localisation with cooperation in wireless sensor networks

In this study, the authors introduce a novel hybrid cooperative localisation scheme when both distance and angle measurements are available. Two linear least squares (LLS) hybrid cooperative schemes based on angle of arrival–time of arrival (AoA–ToA) and AoA–received signal strength (AoA–RSS) signals are proposed. The proposed algorithms are modified to accommodate cooperative localisation in resource constrained networks where only distance measurements are available between target sensors (TSs) while both distance and angle measurements are available between reference sensors and TSs. Furthermore, an optimised version of the LLS estimator is proposed to further enhance the localisation performance. Moreover, localisation of sensor nodes in networks with limited connectivity (partially connected networks) is also investigated. Finally, computational complexity analysis of the proposed algorithms is presented. Through simulation, the superior performance of the proposed algorithms over its non-cooperative counterpart and the hybrid signal based iterative non-linear least squares algorithms is demonstrated

Optimised Localisation in Wireless Sensor Networks

Wireless sensor networks (WSNs) comprise of tens, hundreds or thousands of low powered, low cost wireless nodes, capable of sensing environmental data such as humidity and temperature. Other than these sensing abilities, these nodes are also able to locate themselves. Different techniques can be found in literature to localise wireless nodes in WSNs. These localisation algorithms are based on the distance estimates between the nodes, the angle estimates between the nodes or hybrid schemes. In the context of range based algorithms, two prime techniques based on the time of arrival (ToA) and the received signal strength (RSS) are commonly used. On the other hand, angle based approach is based on the angle of arrival (AoA) of the signal. A hybrid approach is sometimes used to localise wireless nodes. Hybrid algorithms are more accurate than range and angle based algorithms because of additional observations. Modern WSNs consist of a small group of highly resourced wireless nodes with known locations called anchor nodes (ANs) and a large group of low resourced wireless nodes known as the target nodes (TNs). The ANs can locate themselves through GPS or they may have a predetermined location given to them during network deployment. Based on these known locations and the range/angle estimates, the TNs are localised. Since hybrid algorithms (a combination of RSS, ToA and AoA) are more accurate than other algorithms, a major portion of this thesis will focus on these approaches. Two prime hybrid signal models are discussed: i) The AoA-RSS hybrid model and ii) the AoA-ToA hybrid signal model. A hybrid AoA-ToA model is first studied and is further improved by making the model unbiased and by developing a new weighted linear least squares algorithm for AoA-ToA signal (WLLS-AoA-ToA) that capitalise on the covariance matrix of the incoming signal. A similar approach is taken in deriving a WLLS algorithm for AoA-RSS signal (WLLS-AoA-RSS). Moreover expressions of theoretical mean square error (MSE) of the location estimate for both signal models are derived. Performances of both signal models are further improved by designing an optimum anchor selection (OAS) criterion for AoA-ToA signal model and a two step optimum anchor selection (TSOAS) criterion for AoA-RSS signal model. To bound the performance of WLLS algorithms linear Cramer Rao bounds (LCRB) are derived for both models, which will be referred to as LCRB-AoA-ToA and LCRB-AoA-RSS, for AoA-ToA and AoA-RSS signal models, respectively. These hybrid localisation schemes are taken one step further and a cooperative version of these algorithms (LLS-Coop) is designed. The cooperation between the TNs significantly improves the accuracy of final estimates. However this comes at a cost that not only the ANs but the TNs must also be able to estimate AoA and ToA/RSS simultaneously. Thus another version of the same cooperative model is designed (LLS-Coop-X) which eliminates the necessity of simultaneous angle-range estimation by TNs. A third version of cooperative model is also proposed (LLS-Opt-Coop) that capitalises the covariance matrix of incoming signal for performance improvement. Moreover complexity analysis is done for all three versions of the cooperative schemes and is compared with its non cooperative counterparts. In order to extract the distance estimate from the RSS the correct knowledge of path-loss exponent (PLE) is required. In most of the studies this PLE is assumed to be accurately known, also the same and fixed PLE value is used for all communication links. This is an oversimplification of real conditions. Thus error analysis of location estimates with incorrect PLE assumptions for LLS technique is done in their respective chapters. Moreover a mobile TN and an unknown PLE vector is considered which is changing continuously due to the motion of TN. Thus the PLE vector is first estimated using the generalized pattern search (GenPS) followed by the tracking of TN via the Kalman filter (KF) and the particle filter (PF). The performance comparison in terms of root mean square error (RMSE) is also done for KF, extended Kalman filter (EKF) and PF

AN ENERGY EFFICIENT CROSS-LAYER NETWORK OPERATION MODEL FOR MOBILE WIRELESS SENSOR NETWORKS

Wireless sensor networks (WSNs) are modern technologies used to sense/control the environment whether indoors or outdoors. Sensor nodes are miniatures that can sense a specific event according to the end user(s) needs. The types of applications where such technology can be utilised and implemented are vast and range from households’ low end simple need applications to high end military based applications. WSNs are resource limited. Sensor nodes are expected to work on a limited source of power (e.g., batteries). The connectivity quality and reliability of the nodes is dependent on the quality of the hardware which the nodes are made of. Sensor nodes are envisioned to be either stationary or mobile. Mobility increases the issues of the quality of the operation of the network because it effects directly on the quality of the connections between the nodes

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin

A survey of self organisation in future cellular networks

This article surveys the literature over the period of the last decade on the emerging field of self organisation as applied to wireless cellular communication networks. Self organisation has been extensively studied and applied in adhoc networks, wireless sensor networks and autonomic computer networks; however in the context of wireless cellular networks, this is the first attempt to put in perspective the various efforts in form of a tutorial/survey. We provide a comprehensive survey of the existing literature, projects and standards in self organising cellular networks. Additionally, we also aim to present a clear understanding of this active research area, identifying a clear taxonomy and guidelines for design of self organising mechanisms. We compare strength and weakness of existing solutions and highlight the key research areas for further development. This paper serves as a guide and a starting point for anyone willing to delve into research on self organisation in wireless cellular communication networks

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin

Federated Sensor Network architectural design for the Internet of Things (IoT)

An information technology that can combine the physical world and virtual world is desired. The Internet of Things (IoT) is a concept system that uses Radio Frequency Identification (RFID), WSN and barcode scanners to sense and to detect physical objects and events. This information is shared with people on the Internet. With the announcement of the Smarter Planet concept by IBM, the problem of how to share this data was raised. However, the original design of WSN aims to provide environment monitoring and control within a small scale local network. It cannot meet the demands of the IoT because there is a lack of multi-connection functionality with other WSNs and upper level applications. As various standards of WSNs provide information for different purposes, a hybrid system that gives a complete answer by combining all of them could be promising for future IoT applications. This thesis is on the subject of `Federated Sensor Network' design and architectural development for the Internet of Things. A Federated Sensor Network (FSN) is a system that integrates WSNs and the Internet. Currently, methods of integrating WSNs and the Internet can follow one of three main directions: a Front-End Proxy solution, a Gateway solution or a TCP/IP Overlay solution. Architectures based on the ideas from all three directions are presented in this thesis; this forms a comprehensive body of research on possible Federated Sensor Network architecture designs. In addition, a fully compatible technology for the sensor network application, namely the Sensor Model Language (SensorML), has been reviewed and embedded into our FSN systems. The IoT as a new concept is also comprehensively described and the major technical issues discussed. Finally, a case study of the IoT in logistic management for emergency response is given. Proposed FSN architectures based on the Gateway solution are demonstrated through hardware implementation and lab tests. A demonstration of the 6LoWPAN enabled federated sensor network based on the TCP/IP Overlay solution presents a good result for the iNET localization and tracking project. All the tests of the designs have verified feasibility and achieve the target of the IoT concept