Survey of energy efficient tracking and localization techniques in buildings using optical and wireless communication media
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paper_title: LOFAR: the first of a new generation of radio telescopes

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The Low Frequency Array (LOFAR) opens a previously largely unexplored frequency domain for challenging radio-astronomical research. At the 10 to 240 MHz operating frequencies of this radio telescope, it is feasible to employ very large numbers of simple, all-sky antennas with wide-band early digitization. This means that almost the full signal processing chain can be realized in (embedded) software. This approach makes it possible to deal with Earth-based radio signals in effective and novel ways. The signal processing challenges in LOFAR are manifold, since the ultimate dynamic range in astronomical images depends on the quality of the full chain of operations that combines ten-thousands of antenna signals into a single multichannel image cube, while correcting for a large variety of instrumental and environmental effects.
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paper_title: Performance of multiple-receive multiple-transmit beamforming in WLAN-type systems under power or EIRP constraints with delayed channel estimates

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Downlink beamforming in a WLAN-type system employing access points and mobiles equipped with multiple antennas and associated receivers and transmitters are considered. The beamforming aims at maximizing the performance under constraints on transmit power or equivalent isotropic radiated power (EIRP). Solutions for the two constraints are derived and investigated using simulated and measured channels. Our simulation and experimental results shows that performance gains of 8-10 dB when using four directional transmitter antennas and two receive antennas (as compared with a base-line one-transmit two-receive), are possible under both constraints. For simulated channels, a delay between channel estimation and use of the same channel of up to 10% of the (inverse of the) Doppler frequency only degrades performance some tenths of a dB. In our measurements, very small degradations are seen with delays of up to 130 ms. The measurements were made under relatively stationary conditions with only occasionally moving people. Two different strategies for updating the beamforming vectors: sounding and ping-pong, are also considered in the paper.
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paper_title: Applications Of Antenna Arrays To Mobile Communications, Part I: Performance Improvement, Feasibility, And System Considerations

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The demand for wireless mobile communications services is growing at an explosive rate, with the anticipation that communication to a mobile device anywhere on the globe at all times will be available in the near future. An array of antennas mounted on vehicles, ships, aircraft, satellites, and base stations is expected to play an important role in fulfilling the increased demand of channel requirement for these services, as well as for the realization of the dream that a portable communications device the size of a wristwatch be available at an affordable cost for such services. This paper is the first of a two-part study. It provides a comprehensive treatment, at a level appropriate to nonspecialists, of the use of an antenna array to enhance the efficiency of mobile communications systems. It presents an overview of mobile communications as well as details of how an array may be used in various mobile communications systems, including land-mobile, indoor-radio, and satellite-based systems. It discusses advantages of an array of antennas in a mobile communications system, highlights improvements that are possible by using multiple antennas compared to a single antenna in a system, and provides details on the feasibility of antenna arrays for mobile communications applications.
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paper_title: Array and Phased Array Antenna Basics

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Preface. References. Acknowledgments. Acronyms. 1 Radiation. 1.1 The Early History of Electricity and Magnetism. 1.2 James Clerk Maxwell, The Union of Electricity and Magnetism. 1.3 Radiation by Accelerated Charge. 1.4 Reactive and Radiating Electromagnetic Fields. 2 Antennas. 2.1 The Early History of Antennas. 2.2 Antenna Developments During the First World War. 2.3 Antenna Developments in Between the Wars. 2.4 Antenna Developments During the Second World War. 2.5 Post-War Antenna Developments. 3 Antenna Parameters. 3.1 Radiation Pattern. 3.2 Antenna Impedance and Bandwidth. 3.3 Polarisation. 3.4 Antenna Effective Area and Vector Effective Length. 3.5 Radio Equation. 3.6 Radar Equation. 4 The Linear Broadside Array Antenna. 4.1 A Linear Array of Non-Isotropic Point-Source Radiators. 4.2 Plane Waves. 4.3 Received Signal. 4.4 Array Factor. 4.5 Side Lobes and Grating Lobes. 4.6 Amplitude Taper. 5 Design of a 4-Element, Linear, Broadside, Microstrip Patch Array Antenna. 5.1 Introduction. 5.2 Rectangular Microstrip Patch Antenna. 5.3 Split-T Power Divider. 5.4 Transmission and Reflection Coefficients for a Corporate Fed Array Antenna. 5.5 Simulation, Realisation and Measurement. 6 The Linear Endfire Array Antenna. 6.1 Introduction. 6.2 Phase Differences. 6.3 Hansen-Woodyard Endfire Array Antenna. 6.4 Mutual Coupling. 6.5 Yagi-Uda Array Antenna. 7 The Linear Phased Array Antenna. 7.1 Linear Phase Taper. 7.2 Beam Broadening. 7.3 Grating Lobes and Visible Space. 7.4 Means of Phase Shifting. 8 A Frequency Scanned Slotted Waveguide Array Antenna. 8.1 Slotted Waveguide Array Antenna. 8.2 Antenna Design. 8.3 Validation. 9 The Planar Array and Phased Array Antenna. 9.1 Geometry. 9.2 Planar Array Antenna. 9.3 Planar Phased Array Antenna. 10 Special Array Antenna Configurations. 10.1 Conformal Array and Phased Array Antennas. 10.2 Volume Array and Phased Array Antennas. 10.3 Sequential Rotation and Phasing. 10.4 Reactive Loading. 11 Array and Phased Array Antenna Measurement. 11.1 Input Impedance, Self-Coupling and Mutual Coupling. 11.2 Radiation Pattern Measurement. 11.3 Scan Element Pattern. 11.4 Waveguide Simulator. Appendix A: Complex Analysis. A.1 Complex Numbers. A.2 Use of Complex Variables. Appendix B: Vector Analysis. B.1 Notation. B.2 Addition and Subtraction. B.3 Products. B.4 Derivatives. Appendix C: Effective Aperture and Directivity. Appendix D: Transmission Line Theory. D.1 Distributed Parameters. D.2 Guided Waves. D.3 Input Impedance of a Transmission Line. D.4 Terminated Lossless Transmission Lines. D.5 Quarter Wavelength Impedance Transformer. Appendix E: Scattering Matrix. E.1 Normalised Scattering Matrix. E.2 Unnormalised Scattering Matrix. Appendix F: Voltage Incident at a Transmission Line. Appendix :G Cascaded Scattering Matrices. Index.
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paper_title: From theory to practice: an overview of MIMO space-time coded wireless systems

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This paper presents an overview of progress in the area of multiple input multiple output (MIMO) space-time coded wireless systems. After some background on the research leading to the discovery of the enormous potential of MIMO wireless links, we highlight the different classes of techniques and algorithms proposed which attempt to realize the various benefits of MIMO including spatial multiplexing and space-time coding schemes. These algorithms are often derived and analyzed under ideal independent fading conditions. We present the state of the art in channel modeling and measurements, leading to a better understanding of actual MIMO gains. Finally, the paper addresses current questions regarding the integration of MIMO links in practical wireless systems and standards.
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paper_title: Wideband Beamforming: Concepts and Techniques

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This book provides an excellent reference for all professionals working in the area of array signal processing and its applications in wireless communications. Wideband beamforming has advanced with the increasing bandwidth in wireless communications and the development of ultra wideband (UWB) technology. In this book, the authors address the fundamentals and most recent developments in the field of wideband beamforming. The book provides a thorough coverage of the subject including major sub-areas such as sub-band adaptive beamforming, frequency invariant beamforming, blind wideband beamforming, beamforming without temporal processing, and beamforming for multi-path signals. Key Features: Unique book focusing on wideband beamforming Discusses a hot topic coinciding with the increasing bandwidth in wireless communications and the development of UWB technology Addresses the general concept of beamforming including fixed beamformers and adaptive beamformers Covers advanced topics including sub-band adaptive beamforming, frequency invariant beamforming, blind wideband beamforming, beamforming without temporal processing, and beamforming for multi-path signals Includes various design examples and corresponding complexity analyses This book provides a reference for engineers and researchers in wireless communications and signal processing fields. Postgraduate students studying signal processing will also find this book of interest.
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paper_title: Application and performance of downlink beamforming techniques in UMTS

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The opportunities and constraints for application of beamforming techniques in UMTS are reviewed and compared by means of extensive dynamic network-level simulations. We start by reviewing the physical layer specifications for UMTS in order to clarify which channels are allowed to use beamforming. Second, radio resource management for cells with beamforming capabilities are addressed from a standardization and algorithmic point of view. The exchange of beamforming specific measurement reports between the base station (Node-B) and the radio network controller is discussed as well as beam switching mechanisms, directional power-based admission control, and more. In addition to implementation of beamforming within logical cells, options for exploiting the antenna array to synthesize independent sector beams are also investigated (i.e., higher order sectorization via beamforming). The presented results show that beamforming within logical cells is an effective enabler for higher system capacity, while the use of beamforming for creation of many logical cells is less attractive due to significantly larger soft handover overhead and somewhat reduced capacity gain.
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paper_title: Trends in Wideband Phased-Array Front-Ends

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Wideband phased-array front-end technology is characterised by stringent specifications, increasing cost-pressure and is subject to fundamental changes. This paper addresses trends observed for these systems, both in relation to the functionality required (including the architecture of the system and the platforms upon which they are applied) as well as in relation to the technologies that may be employed.
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paper_title: Multiple emitter location and signal Parameter estimation

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Processing the signals received on an array of sensors for the location of the emitter is of great enough interest to have been treated under many special case assumptions. The general problem considers sensors with arbitrary locations and arbitrary directional characteristics (gain/phase/polarization) in a noise/interference environment of arbitrary covariance matrix. This report is concerned first with the multiple emitter aspect of this problem and second with the generality of solution. A description is given of the multiple signal classification (MUSIC) algorithm, which provides asymptotically unbiased estimates of 1) number of incident wavefronts present; 2) directions of arrival (DOA) (or emitter locations); 3) strengths and cross correlations among the incident waveforms; 4) noise/interference strength. Examples and comparisons with methods based on maximum likelihood (ML) and maximum entropy (ME), as well as conventional beamforming are included. An example of its use as a multiple frequency estimator operating on time series is included.
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paper_title: ESPRIT-estimation of signal parameters via rotational invariance techniques

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An approach to the general problem of signal parameter estimation is described. The algorithm differs from its predecessor in that a total least-squares rather than a standard least-squares criterion is used. Although discussed in the context of direction-of-arrival estimation, ESPRIT can be applied to a wide variety of problems including accurate detection and estimation of sinusoids in noise. It exploits an underlying rotational invariance among signal subspaces induced by an array of sensors with a translational invariance structure. The technique, when applicable, manifests significant performance and computational advantages over previous algorithms such as MEM, Capon's MLM, and MUSIC. >
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paper_title: Signal acquisition and tracking with adaptive arrays in the digital mobile radio system IS-54 with flat fading

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The author considers the dynamic performance of adaptive arrays in wireless communication systems. With an adaptive array, the signals received by multiple antennas are weighted and combined to suppress interference and combat desired signal fading. In these systems, the weight adaptation algorithm must acquire and track the weights even with rapid fading. The author considers the performance of the least-mean-square (LMS) and direct matrix inversion (DMI) algorithms in the North American digital mobile radio system IS-54. He shows that implementation of these algorithms permits the use of coherent detection, which improves performance by 1 dB over differential detection. Results for two base station antennas with flat Rayleigh fading show that the LMS algorithm has large tracking loss for vehicle speeds above 20 mph, but the DMI algorithm can acquire and track the weights to combat desired signal fading at vehicle speeds up to 60 mph with less than 0.2 dB degradation from ideal performance with differential detection. Similarly, interference is also suppressed with performance gains over maximal ratio combining within 0.5 dB of the predicted ideal gain. >
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paper_title: Tracking issues of some blind equalization algorithms

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Due to the growing demand for mobile communications, blind adaptive algorithms have an important role in improving data transmission efficiency. In this context, the convergence and tracking analysis of such algorithms is a problem of interest. Recently, a tracking analysis of the Constant Modulus Algorithm was presented based on an energy conservation relation. In this letter we extend that analysis to blind quasi-Newton algorithms that minimize the Constant Modulus cost function. Under certain conditions, the considered algorithms can reach the same steady-state mean-square error. Close agreement between analytical and simulation results is shown.
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paper_title: Adaptive Array Systems: Fundamentals and Applications

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Preface. Acknowledgments. List of Figures. List of Tables. Introduction. I.1 Adaptive Filtering. I.2 Historical Aspects. I.3 Concept of Spatial Signal Processing. 1 Fundamentals of Array Signal Processing. 1.1 Introduction. 1.2 The Key to Transmission. 1.3 Hertzian Dipole. 1.4 Antenna Parameters & Terminology. 1.5 Basic Antenna Elements. 1.6 Antenna Arrays. 1.7 Spatial Filtering. 1.8 Adaptive Antenna Arrays. 1.9 Mutual Coupling & Correlation. 1.10 Chapter Summary. 1.11 Problems. 2 Narrowband Array Systems. 2.1 Introduction. 2.2 Adaptive Antenna Terminology. 2.3 Beam Steering. 2.4 Grating Lobes. 2.5 Amplitude Weights. 2.6 Chapter Summary. 2.7 Problems. 3 Wideband Array Processing. 3.1 Introduction. 3.2 Basic concepts. 3.3 A Simple Delay-line Wideband Array. 3.4 Rectangular Arrays as Wideband Beamformers. 3.5 Wideband Beamforming using FIR Filters. 3.6 Chapter Summary. 3.7 Problems. 4 Adaptive Arrays. 4.1 Introduction. 4.2 Spatial Covariance Matrix. 4.3 Multi-beam Arrays. 4.4 Scanning Arrays. 4.5 Switched Beam Beamformers. 4.6 Fully Adaptive Beamformers. 4.7 Adaptive Algorithms. 4.8 Source Location Techniques. 4.9 Fourier Method. 4.10 Capon's Minimum Variance. 4.11 The MUSIC Algorithm. 4.12 ESPRIT. 4.13 Maximum Likelihood Techniques. 4.14 Spatial Smoothing. 4.15 Determination of Number of Signal Sources. 4.16 Blind Beamforming. 4.17 Chapter Summary. 4.18 Problems. 5 Practical Considerations. 5.1 Introduction. 5.2 Signal Processing Constraints. 5.3 Implementation Issues. 5.4 Radiowave Propagation. 5.5 Transmit Beamforming. 5.6 Chapter Summary. 5.7 Problems. 6 Applications. 6.1 Introduction. 6.2 Antenna Arrays for Radar Applications. 6.3 Antenna Arrays for Sonar Applications. 6.4 Antenna Arrays for Biomedical Applications. 6.5 Antenna Arrays for Wireless Communications. 6.6 Chapter Summary. 6.7 Problems. References. Index.
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paper_title: A survey on localization techniques for wireless networks

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Abstract Wireless networks have displaced the well established and widely deployed wired communication networks of the past. Tetherless access and new services offered to mobile users contribute to the popularity of these networks. Thus users have access from many locations and can roam ubiquitously. The knowledge of the physical location of mobile user devices, such as phones, laptops and PDAs, is important in several applications such as network planning, location based services, law enforcement and for improving network performance. A device's location is usually estimated by monitoring a distance dependent parameter such as wireless signal strength from a base station whose location is known. In practical deployments, signal strength varies with time and its relationship to distance is not well defined. This makes location estimation difficult. Many location estimation or localization schemes have been proposed for networks adopting a variety of wireless technologies. This paper reviews a broad class ...
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paper_title: Simulated annealing based localization in wireless sensor network

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In sensor networks, the information obtained from sensors are meaningless without the location information. In this paper, we propose a simulated annealing based localization (SAL) scheme for wireless sensor networks. Simulated annealing (SA) is used to estimate the approximate solution to combinatorial optimization problems. The SAL scheme can bring the convergence out of the local minima in a controlled fashion. Simulation results show that this scheme gives accurate and consistent location estimates of the nodes
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paper_title: Client assisted location data acquisition scheme for secure enterprise wireless networks

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Current wireless networks that are widely deployed for various commercial applications, do not keep track of a mobile user's location. However, location information can enhance security by facilitating tracking of misbehaving users, or though implementation of location based network access. Previous work done on location estimation typically involves methods that use a lookup table comprising the client or access point signal strengths, which are collected manually at short distances throughout the site. This paper proposes a new data collection scheme for building a lookup table using client assistance in an enterprise wireless environment. In this work, a network-bused location estimation scheme is implemented using sniffers, which monitor client signal strength. It is observed that the accuracy of location estimation is improved by averaging the lookup table data collected over time. The client assisted data collection scheme can be used to frequently build lookup tables in an efficient manner and hence improve accuracy in location estimation. Thus, this scheme could be used to implement a location based security policy throughout the enterprise wireless network.
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paper_title: The active badge location system

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A novel system for the location of people in an office environment is described. Members of staff wear badges that transmit signals providing information about their location to a centralized location service, through a network of sensors. The paper also examines alternative location techniques, system design issues and applications, particularly relating to telephone call routing. Location systems raise concerns about the privacy of an individual and these issues are also addressed.
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paper_title: A Probabilistic Room Location Service for Wireless Networked Environments

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The popularity of wireless networks has increased in recent years and is becoming a common addition to LANs. In this paper we investigate a novel use for a wireless network based on the IEEE 802.11 standard: inferring the location of a wireless client from signal quality measures. Similar work has been limited to prototype systems that rely on nearest-neighbor techniques to infer location. In this paper, we describe Nibble, a Wi-Fi location service that uses Bayesian networks to infer the location of a device. We explain the general theory behind the system and how to use the system, along with describing our experiences at a university campus building and at a research lab. We also discuss how probabilistic modeling can be applied to a diverse range of applications that use sensor data.
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paper_title: Hybrid TOA/AOA techniques for mobile location in non-line-of-sight environments

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Techniques for locating wireless subscribers for E-911 emergency services must meet the stringent accuracy requirements set by the FCC. In non-line-of-sight propagation conditions, large measurement errors with unknown statistics cause standard location schemes to perform poorly. In these challenging environments, it is necessary to develop methods that can integrate heterogeneous measurements and utilize all available information to mitigate the errors and improve location accuracy. This paper illustrates a hybrid time and angle of arrival technique that utilizes non-linear constrained optimization to estimate the mobile terminal's location with bounds on the range and angle errors inferred from geometry. Another simple hybrid TOA/AOA algorithm based on a least squares solution of lines of position is also proposed. These algorithms are compared to previous approaches using TOA only and simulation results are provided that show the accuracy gains of the proposed algorithms.
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paper_title: Global Positioning System: Theory and Practice

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1 Introduction.- 1.1 The origins of surveying.- 1.2 Development of global surveying techniques.- 1.2.1 Optical global triangulation.- 1.2.2 Electromagnetic global trilateration.- 1.3 History of the Global Positioning System.- 1.3.1 Navigating with GPS.- 1.3.2 Surveying with GPS.- 2 Overview of GPS.- 2.1 Basic concept.- 2.2 Space segment.- 2.2.1 Constellation.- 2.2.2 Satellites.- 2.2.3 Operational capabilities.- 2.2.4 Denial of accuracy and access.- 2.3 Control segment.- 2.3.1 Master control station.- 2.3.2 Monitor stations.- 2.3.3 Ground control stations.- 2.4 User segment.- 2.4.1 User categories.- 2.4.2 Receiver types.- 2.4.3 Information services.- 3 Reference systems.- 3.1 Introduction.- 3.2 Coordinate systems.- 3.2.1 Definitions.- 3.2.2 Transformations.- 3.3 Time systems.- 3.3.1 Definitions.- 3.3.2 Conversions.- 3.3.3 Calendar.- 4 Satellite orbits.- 4.1 Introduction.- 4.2 Orbit description.- 4.2.1 Keplerian motion.- 4.2.2 Perturbed motion.- 4.2.3 Disturbing accelerations.- 4.3 Orbit determination.- 4.3.1 Keplerian orbit.- 4.3.2 Perturbed orbit.- 4.4 Orbit dissemination.- 4.4.1 Tracking networks.- 4.4.2 Ephemerides.- 5 Satellite signal.- 5.1 Signal structure.- 5.1.1 Physical fundamentals.- 5.1.2 Components of the signal.- 5.2 Signal processing.- 5.2.1 Receiver design.- 5.2.2 Processing techniques.- 6 Observables.- 6.1 Data acquisition.- 6.1.1 Code pseudoranges.- 6.1.2 Phase pseudoranges.- 6.1.3 Doppler data.- 6.1.4 Biases and noise.- 6.2 Data combinations.- 6.2.1 Linear phase combinations.- 6.2.2 Code pseudorange smoothing.- 6.3 Atmospheric effects.- 6.3.1 Phase and group velocity.- 6.3.2 Ionospheric refraction.- 6.3.3 Tropospheric refraction.- 6.3.4 Atmospheric monitoring.- 6.4 Relativistic effects.- 6.4.1 Special relativity.- 6.4.2 General relativity.- 6.4.3 Relevant relativistic effects for GPS.- 6.5 Antenna phase center offset and variation.- 6.6 Multipath.- 6.6.1 General remarks.- 6.6.2 Mathematical model.- 6.6.3 Multipath reduction.- 7 Surveying with GPS.- 7.1 Introduction.- 7.1.1 Terminology definitions.- 7.1.2 Observation techniques.- 7.1.3 Field equipment.- 7.2 Planning a GPS survey.- 7.2.1 General remarks.- 7.2.2 Presurvey planning.- 7.2.3 Field reconnaissance.- 7.2.4 Monumentation.- 7.2.5 Organizational design.- 7.3 Surveying procedure.- 7.3.1 Preobservation.- 7.3.2 Observation.- 7.3.3 Postobservation.- 7.3.4 Ties to control monuments.- 7.4 In situ data processing.- 7.4.1 Data transfer.- 7.4.2 Data processing.- 7.4.3 Trouble shooting and quality control.- 7.4.4 Datum transformations.- 7.4.5 Computation of plane coordinates.- 7.5 Survey report.- 8 Mathematical models for positioning.- 8.1 Point positioning.- 8.1.1 Point positioning with code ranges.- 8.1.2 Point positioning with carrier phases.- 8.1.3 Point positioning with Doppler data.- 8.2 Differential positioning.- 8.2.1 Basic concept.- 8.2.2 DGPS with code ranges.- 8.2.3 DGPS with phase ranges.- 8.3 Relative positioning.- 8.3.1 Phase differences.- 8.3.2 Correlations of the phase combinations.- 8.3.3 Static relative positioning.- 8.3.4 Kinematic relative positioning.- 8.3.5 Pseudokinematic relative positioning.- 9 Data processing.- 9.1 Data preprocessing.- 9.1.1 Data handling.- 9.1.2 Cycle slip detection and repair.- 9.2 Ambiguity resolution.- 9.2.1 General aspects.- 9.2.2 Basic approaches.- 9.2.3 Search techniques.- 9.2.4 Ambiguity validation.- 9.3 Adjustment, filtering, and smoothing.- 9.3.1 Least squares adjustment.- 9.3.2 Kalman filtering.- 9.3.3 Smoothing.- 9.4 Adjustment of mathematical GPS models.- 9.4.1 Linearization.- 9.4.2 Linear model for point positioning with code ranges.- 9.4.3 Linear model for point positioning with carrier phases.- 9.4.4 Linear model for relative positioning.- 9.5 Network adjustment.- 9.5.1 Single baseline solution.- 9.5.2 Multipoint solution.- 9.5.3 Single baseline versus multipoint solution.- 9.5.4 Least squares adjustment of baselines.- 9.6 Dilution of precision.- 9.7 Accuracy measures.- 9.7.1 Introduction.- 9.7.2 Chi-square distribution.- 9.7.3 Specifications.- 10 Transformation of GPS results.- 10.1 Introduction.- 10.2 Coordinate transformations.- 10.2.1 Cartesian coordinates and ellipsoidal coordinates.- 10.2.2 Global coordinates and local level coordinates.- 10.2.3 Ellipsoidal coordinates and plane coordinates.- 10.2.4 Height transformation.- 10.3 Datum transformations.- 10.3.1 Three-dimensional transformation.- 10.3.2 Two-dimensional transformation.- 10.3.3 One-dimensional transformation.- 10.4 Combining GPS and terrestrial data.- 10.4.1 Common coordinate system.- 10.4.2 Representation of measurement quantities.- 11 Software modules.- 11.1 Introduction.- 11.2 Planning.- 11.3 Data transfer.- 11.4 Data processing.- 11.5 Quality control.- 11.6 Network computations.- 11.7 Data base management.- 11.8 Utilities.- 11.9 Flexibility.- 12 Applications of GPS.- 12.1 General uses of GPS.- 12.1.1 Global uses.- 12.1.2 Regional uses.- 12.1.3 Local uses.- 12.2 Attitude determination.- 12.2.1 Theoretical considerations.- 12.2.2 Practical considerations.- 12.3 Airborne GPS for photo-control.- 12.4 Interoperability of GPS.- 12.4.1 GPS and Inertial Navigation Systems.- 12.4.2 GPS and GLONASS.- 12.4.3 GPS and other sensors.- 12.4.4 GPS and the Federal Radionavigation Plan.- 12.5 Installation of control networks.- 12.5.1 Passive control networks.- 12.5.2 Active control networks.- 13 Future of GPS.- 13.1 New application aspects.- 13.2 GPS modernization.- 13.2.1 Future GPS satellites.- 13.2.2 Augmented signal structure.- 13.3 GPS augmentation.- 13.3.1 Ground-based augmentation.- 13.3.2 Satellite-based augmentation.- 13.4 GNSS.- 13.4.1 GNSS development.- 13.4.2 GNSS/Loran-C integration.- 13.5 Hardware and software improvements.- 13.5.1 Hardware.- 13.5.2 Software.- 13.6 Conclusion.- References.
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paper_title: Wireless Sensor Network Localization Techniques

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Wireless sensor network localization is an important area that attracted significant research interest. This interest is expected to grow further with the proliferation of wireless sensor network applications. This paper provides an overview of the measurement techniques in sensor network localization and the one-hop localization algorithms based on these measurements. A detailed investigation on multi-hop connectivity-based and distance-based localization algorithms are presented. A list of open research problems in the area of distance-based sensor network localization is provided with discussion on possible approaches to them.
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paper_title: Vehicular Ad Hoc Networks: A New Challenge for Localization-Based Systems q

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A new kind of ad hoc network is hitting the streets: Vehicular Ad Hoc Networks (VANets). In these networks, vehicles communicate with each other and possibly with a roadside infrastructure to provide a long list of applications varying from transit safety to driver assistance and Internet access. In these networks, knowledge of the real-time position of nodes is an assumption made by most protocols, algorithms, and applications. This is a very reasonable assumption, since GPS receivers can be installed easily in vehicles, a number of which already comes with this technology. But as VANets advance into critical areas and become more dependent on localization systems, GPS is starting to show some undesired problems such as not always being available or not being robust enough for some applications. For this reason, a number of other localization techniques such as Dead Reckoning, Cellular Localization, and Image/Video Localization has been used in VANets to overcome GPS limitations. A common procedure in all these cases is to use Data Fusion techniques to compute the accurate position of vehicles, creating a new paradigm for localization in which several known localization techniques are combined into a single solution that is more robust and precise than the individual approaches. In this paper, we further discuss this subject by studying and analyzing the localization requirements of the main VANet applications. We then survey each of the localization techniques that can be used to localize vehicles and, finally, examine how these localization techniques can be combined using Data Fusion techniques to provide the robust localization system required by most critical safety applications in VANets.
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paper_title: The Cricket location-support system

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This paper presents the design, implementation, and evaluation of Cricket , a location-support system for in-building, mobile, location-dependent applications. It allows applications running on mobile and static nodes to learn their physical location by using listeners that hear and analyze information from beacons spread throughout the building. Cricket is the result of several design goals, including user privacy, decentralized administration, network heterogeneity, and low cost. Rather than explicitly tracking user location, Cricket helps devices learn where they are and lets them decide whom to advertise this information to; it does not rely on any centralized management or control and there is no explicit coordination between beacons; it provides information to devices regardless of their type of network connectivity; and each Cricket device is made from off-the-shelf components and costs less than U.S. $10. We describe the randomized algorithm used by beacons to transmit information, the use of concurrent radio and ultrasonic signals to infer distance, the listener inference algorithms to overcome multipath and interference, and practical beacon configuration and positioning techniques that improve accuracy. Our experience with Cricket shows that several location-dependent applications such as in-building active maps and device control can be developed with little effort or manual configuration.
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paper_title: Geolocation and assisted GPS

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Currently in development, numerous geolocation technologies can pinpoint a person's or object's position on the Earth. Knowledge of the spatial distribution of wireless callers will facilitate the planning, design, and operation of next generation broadband wireless networks. Mobile users will gain the ability to get local traffic information and detailed directions to gas stations, restaurants, hotels, and other services. Police and rescue teams will be able to quickly and precisely locate people who are lost or injured but cannot give their precise location. Companies will use geolocation based applications to track personnel, vehicles, and other assets. The driving force behind the development of this technology is a US Federal Communications Commission (FCC) mandate stating that by 1 October 2001 all wireless carriers must provide the geolocation of an emergency 911 caller to the appropriate public safety answering point. Location technologies requiring new modified, or upgraded mobile stations must determine the caller's longitude and latitude within 50 meters for 67 percent of emergency calls, and within 150 meters for 95 percent of the calls. Otherwise, they must do so within 100 meters and 300 meters, respectively, for the same percentage of calls. Currently deployed wireless technology can locate 911 calls within an area no smaller than 10 to 15 square kilometers. It is argued that assisted-GPS technology offers superior accuracy, availability, and coverage at a reasonable cost.
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paper_title: Nonparametric belief propagation for self-localization of sensor networks

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Automatic self-localization is a critical need for the effective use of ad hoc sensor networks in military or civilian applications. In general, self-localization involves the combination of absolute location information (e.g., from a global positioning system) with relative calibration information (e.g., distance measurements between sensors) over regions of the network. Furthermore, it is generally desirable to distribute the computational burden across the network and minimize the amount of intersensor communication. We demonstrate that the information used for sensor localization is fundamentally local with regard to the network topology and use this observation to reformulate the problem within a graphical model framework. We then present and demonstrate the utility of nonparametric belief propagation (NBP), a recent generalization of particle filtering, for both estimating sensor locations and representing location uncertainties. NBP has the advantage that it is easily implemented in a distributed fashion, admits a wide variety of statistical models, and can represent multimodal uncertainty. Using simulations of small to moderately sized sensor networks, we show that NBP may be made robust to outlier measurement errors by a simple model augmentation, and that judicious message construction can result in better estimates. Furthermore, we provide an analysis of NBP's communications requirements, showing that typically only a few messages per sensor are required, and that even low bit-rate approximations of these messages can be used with little or no performance impact.
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paper_title: A system for LEASE: location estimation assisted by stationary emitters for indoor RF wireless networks

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We present LEASE, a new system and framework for location estimation assisted by stationary emitters for indoor RF wireless networks. Unlike previous studies, we emphasize the deployment aspect of location estimation engines. Motivated thus, we present an adaptable infrastructure-based system that uses a small number of stationary emitters (SEs) and sniffers employed in a novel way to locate standard wireless clients in an enterprise. We present the components of the system and its architecture, and new non-parametric techniques for location estimation that work with a small number of SEs. Our techniques for location estimation can also be used in a client-based deployment. We present experimental results of using our techniques at two sites demonstrating the ability to perform location estimation with good accuracy in our new adaptable framework.
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paper_title: GPS-free positioning in mobile ad-hoc networks

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We consider the problem of node positioning in ad-hoc networks. We propose a distributed, infrastructure-free positioning algorithm that does not rely on Global Positioning System (GPS). The algorithm uses the distances between the nodes to build a relative coordinate system in which the node positions are computed in two dimensions. The main contribution of this work is to define and compute relative positions of the nodes in an ad-hoc network without using GPS. We further explain how the proposed approach can be applied to wide area ad-hoc networks.
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paper_title: SurroundSense: mobile phone localization via ambience fingerprinting

paper_content:

A growing number of mobile computing applications are centered around the user's location. The notion of location is broad, ranging from physical coordinates (latitude/longitude) to logical labels (like Starbucks, McDonalds). While extensive research has been performed in physical localization, there have been few attempts in recognizing logical locations. This paper argues that the increasing number of sensors on mobile phones presents new opportunities for logical localization. We postulate that ambient sound, light, and color in a place convey a photo-acoustic signature that can be sensed by the phone's camera and microphone. In-built accelerometers in some phones may also be useful in inferring broad classes of user-motion, often dictated by the nature of the place. By combining these optical, acoustic, and motion attributes, it may be feasible to construct an identifiable fingerprint for logical localization. Hence, users in adjacent stores can be separated logically, even when their physical positions are extremely close. We propose SurroundSense, a mobile phone based system that explores logical localization via ambience fingerprinting. Evaluation results from 51 different stores show that SurroundSense can achieve an average accuracy of 87% when all sensing modalities are employed. We believe this is an encouraging result, opening new possibilities in indoor localization.
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paper_title: The active badge location system

paper_content:

A novel system for the location of people in an office environment is described. Members of staff wear badges that transmit signals providing information about their location to a centralized location service, through a network of sensors. The paper also examines alternative location techniques, system design issues and applications, particularly relating to telephone call routing. Location systems raise concerns about the privacy of an individual and these issues are also addressed.
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paper_title: Calibration as parameter estimation in sensor networks

paper_content:

We describe an ad-hoc localization system for sensor networks and explain why traditional calibration methods are inadequate for this system. Building upon previous work, we frame calibration as a parameter estimation problem; we parameterize each device and choose the values of those parameters that optimize the overall system performance. This method reduces our average error from 74.6% without calibration to 10.1%. We propose ways to expand this technique to a method of autocalibration for localization as well as to other sensor network applications.
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paper_title: A Probabilistic Room Location Service for Wireless Networked Environments

paper_content:

The popularity of wireless networks has increased in recent years and is becoming a common addition to LANs. In this paper we investigate a novel use for a wireless network based on the IEEE 802.11 standard: inferring the location of a wireless client from signal quality measures. Similar work has been limited to prototype systems that rely on nearest-neighbor techniques to infer location. In this paper, we describe Nibble, a Wi-Fi location service that uses Bayesian networks to infer the location of a device. We explain the general theory behind the system and how to use the system, along with describing our experiences at a university campus building and at a research lab. We also discuss how probabilistic modeling can be applied to a diverse range of applications that use sensor data.
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paper_title: Mobile location with bias tracking in non-line-of-sight

paper_content:

The main impairment for the location of terminals in a wireless communications system is the non-line-of-sight (NLOS) condition which is mainly due to blocking of the transmitted signal by obstacles. It is well known that NLOS biases time-of-arrival (TOA) and time-difference-of-arrival (TDOA) estimates, therefore providing a biased position. The paper analyzes the improvements in positioning accuracy by tracking the bias of the time measures with the Kalman filter proposed for location estimation. The evaluation of the approach has been carried out with measures taken in real scenarios, for positioning techniques based on TDOA and TOA+AOA (angle of arrival) measurements.
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paper_title: Secure localization in sensor networks using transmission range variation

paper_content:

In a wireless sensor network, sensors can be randomly distributed in order to collect data from a site. In many cases the location of the wireless sensor nodes is required in order to map the collected data to a particular location. Various schemes have been proposed earlier to estimate the location of sensor nodes in a sensor network. However most of these schemes assume the absence of a malicious user in the system which might not always be true. This paper presents a secure localization algorithm (SLA) that can be implemented with the capabilities of current sensor nodes without the need for any additional specialized hardware. The scheme is based on the transmission of nonces at different power levels from the anchor nodes. A sensor node receives a certain set of nonces which it will have to transmit back to the sink via the anchor nodes. The location of the sensor node can be estimated securely based on this set of nonces. We have investigated the properties of SLA using simulations
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paper_title: RADAR: an in-building RF-based user location and tracking system

paper_content:

The proliferation of mobile computing devices and local-area wireless networks has fostered a growing interest in location-aware systems and services. In this paper we present RADAR, a radio-frequency (RF)-based system for locating and tracking users inside buildings. RADAR operates by recording and processing signal strength information at multiple base stations positioned to provide overlapping coverage in the area of interest. It combines empirical measurements with signal propagation modeling to determine user location and thereby enable location-aware services and applications. We present experimental results that demonstrate the ability of RADAR to estimate user location with a high degree of accuracy.
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paper_title: Multiple emitter location and signal Parameter estimation

paper_content:

Processing the signals received on an array of sensors for the location of the emitter is of great enough interest to have been treated under many special case assumptions. The general problem considers sensors with arbitrary locations and arbitrary directional characteristics (gain/phase/polarization) in a noise/interference environment of arbitrary covariance matrix. This report is concerned first with the multiple emitter aspect of this problem and second with the generality of solution. A description is given of the multiple signal classification (MUSIC) algorithm, which provides asymptotically unbiased estimates of 1) number of incident wavefronts present; 2) directions of arrival (DOA) (or emitter locations); 3) strengths and cross correlations among the incident waveforms; 4) noise/interference strength. Examples and comparisons with methods based on maximum likelihood (ML) and maximum entropy (ME), as well as conventional beamforming are included. An example of its use as a multiple frequency estimator operating on time series is included.
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paper_title: Angular CMA: A modified Constant Modulus Algorithm providing steering angle updates

paper_content:

Conventional blind beamforming algorithms have no direct notion of the physical Direction of Arrival angle of an impinging signal. These blind adaptive algorithms operate by adjusting the complex steering vector in the case of changing signal conditions and directions. This paper presents Angular CMA, a blind beamforming method that calculates steering angle updates (instead of weight vector updates) to keep track of the desired signal. Angular CMA and its respective steering angle updates are particularly useful in the context of mixed-signal hierarchical arrays as means to find and distribute steering parameters. Simulations of Angular CMA show promising convergence behaviour, while having a lower complexity than alternative methods (e.g., MUSIC).
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paper_title: ESPRIT-estimation of signal parameters via rotational invariance techniques

paper_content:

An approach to the general problem of signal parameter estimation is described. The algorithm differs from its predecessor in that a total least-squares rather than a standard least-squares criterion is used. Although discussed in the context of direction-of-arrival estimation, ESPRIT can be applied to a wide variety of problems including accurate detection and estimation of sinusoids in noise. It exploits an underlying rotational invariance among signal subspaces induced by an array of sensors with a translational invariance structure. The technique, when applicable, manifests significant performance and computational advantages over previous algorithms such as MEM, Capon's MLM, and MUSIC. >
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paper_title: Wireless Sensor Network Localization Techniques

paper_content:

Wireless sensor network localization is an important area that attracted significant research interest. This interest is expected to grow further with the proliferation of wireless sensor network applications. This paper provides an overview of the measurement techniques in sensor network localization and the one-hop localization algorithms based on these measurements. A detailed investigation on multi-hop connectivity-based and distance-based localization algorithms are presented. A list of open research problems in the area of distance-based sensor network localization is provided with discussion on possible approaches to them.
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paper_title: GSM indoor localization

paper_content:

Accurate indoor localization has long been an objective of the ubiquitous computing research community, and numerous indoor localization solutions based on 802.11, Bluetooth, ultrasound and infrared technologies have been proposed. This paper presents the first accurate GSM indoor localization system that achieves median within floor accuracy of 4 m in large buildings and is able to identify the floor correctly in up to 60% of the cases and is within 2 floors in up to 98% of the cases in tall multi-floor buildings. We report evaluation results of two case studies conducted over a course of several years, with data collected from 6 buildings in 3 cities across North America. The key idea that makes accurate GSM-based indoor localization possible is the use of wide signal-strength fingerprints. In addition to the 6-strongest cells traditionally used in the GSM standard, the wide fingerprint includes readings from additional cells that are strong enough to be detected, but are too weak to be used for efficient communication. We further show that selecting a subset of highly relevant channels for fingerprinting matching out of all available channels, further improves the localization accuracy.
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paper_title: Tracking issues of some blind equalization algorithms

paper_content:

Due to the growing demand for mobile communications, blind adaptive algorithms have an important role in improving data transmission efficiency. In this context, the convergence and tracking analysis of such algorithms is a problem of interest. Recently, a tracking analysis of the Constant Modulus Algorithm was presented based on an energy conservation relation. In this letter we extend that analysis to blind quasi-Newton algorithms that minimize the Constant Modulus cost function. Under certain conditions, the considered algorithms can reach the same steady-state mean-square error. Close agreement between analytical and simulation results is shown.
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paper_title: Recent trends and advances in UWB positioning

paper_content:

Since the ruling of the Federal Communications Commission (FCC) in the United States to open up the spectrum from 3.1–10.6 GHz for ultra wideband (UWB) applications in 2002, interest in the use of UWB for localization outside of military applications has skyrocketed. The multi-purpose nature of UWB for localization and also high or low data rate communication make it robust and attractive in many indoor applications including wireless sensor networks, medical body area networks (BANs), surgical navigation, etc. A push towards integrating UWB with global positioning systems (GPS), wireless local area networks (WLANs), Wi-Fi, and inertial measurement units (IMUs) help to mitigate localization errors with redundancy and increase interoperability with existing technologies. A look at the current trends both in the research community and industry highlight future applications of UWB positioning and the technologies which will serve as the building blocks in these systems.
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paper_title: Precise distance measurement with IEEE 802.15.4 (ZigBee) devices

paper_content:

In modern wireless communications products it is required to incorporate more and more different functions to comply with current market trends. A very attractive function with steadily growing market penetration is local positioning. To add this feature to low-cost mass-market devices without additional power consumption, it is desirable to use commercial communication chips and standards for localization of the wireless units. In this paper we present a concept to measure the distance between two IEEE 802.15.4 (ZigBee) compliant devices. The presented prototype hardware consists of a low- cost 2.45 GHz ZigBee chipset. For localization we use standard communication packets as transmit signals. Thus simultaneous data transmission and transponder localization is feasible. To achieve high positioning accuracy even in multipath environments, a coherent synthesis of measurements in multiple channels and a special signal phase evaluation concept is applied. With this technique the full available ISM bandwidth of 80 MHz is utilized. In first measurements with two different frequency references-a low-cost oscillator and a temperatur-compensated crystal oscillator-a positioning bias error of below 16 cm and 9 cm was obtained. The standard deviation was less than 3 cm and 1 cm, respectively. It is demonstrated that compared to signal correlation in time, the phase processing technique yields an accuracy improvement of roughly an order of magnitude.
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paper_title: High Precision Indoor and Outdoor Positioning using LocataNet

paper_content:

Today, GPS is the most popular and widely used three-dimensional positioning technology in the world. However, in many everyday environments such as indoors or in urban areas, GPS signals are not available for positioning (due to the very weak signals). Even with high sensitivity GPS receivers, positioning for urban and indoor environments cannot be guaranteed in all situations, and accuracies are typically of the order of tens to hundreds of meters at best. Other emerging technologies obtain positions from systems that are not designed for positioning, such as mobile phones or television. As a result, the accuracy, reliability and simplicity of the position solution is typically very poor in comparison to GPS with a clear view of the sky. Locata is a new positioning technology, developed to address the failure of current technologies for reliable ubiquitous (outdoor and indoor) positioning. In this paper key aspects of the new technology are discussed, with particular emphasis on the positioning network (LocataNet). An innovative characteristic of the LocataNet is its ability to propagate (autonomously) into difficult environments and over wide areas. Through an experimental LocataNet installation, a key mechanism for achieving this is tested, and real-time stand-alone positioning (without a base station and additional data link) with sub-centimeter precision is demonstrated.
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paper_title: RFID tags: Positioning principles and localization techniques

paper_content:

RFID is an automatic identification technology that enables tracking of people and objects. Both identity and location are generally key information for indoor services. An obvious and interesting method to obtain these two types of data is to localize RFID tags attached to devices or objects or carried by people. However, signals in indoor environments are generally harshly impaired and tags have very limited capabilities which pose many challenges for positioning them. In this work, we propose a classification and survey the current state-of-art of RFID localization by first presenting this technology and positioning principles. Then, we explain and classify RFID localization techniques. Finally, we discuss future trends in this domain.
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paper_title: RADAR: an in-building RF-based user location and tracking system

paper_content:

The proliferation of mobile computing devices and local-area wireless networks has fostered a growing interest in location-aware systems and services. In this paper we present RADAR, a radio-frequency (RF)-based system for locating and tracking users inside buildings. RADAR operates by recording and processing signal strength information at multiple base stations positioned to provide overlapping coverage in the area of interest. It combines empirical measurements with signal propagation modeling to determine user location and thereby enable location-aware services and applications. We present experimental results that demonstrate the ability of RADAR to estimate user location with a high degree of accuracy.
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paper_title: PBIL PDR for scalable Bluetooth Indoor Localization

paper_content:

The ever-existing problems in indoor localization are attaining efficient scalability, reliability and accuracy besides cost efficiency. Although diverse approaches based on WLAN, Bluetooth, ZigBee, RFID and UWB had been divulged for localization and navigation, these schemes often do lack competent localization. Furthermore these schemes linger either expensive or be deficient in accuracy. Moreover not all technologies exist in smart phones. Recent outburst of technology expansion has paved way to solve indoor localization complexity by cohering various positioning methods and sensor models. In this paper, we developed a unified particle filter based localization approach based on Bluetooth positioning and pedestrian dead reckoning (PDR) method. We call this system as PBIL (PDR for scalable Bluetooth Indoor Localization). The proposed approach overcomes failure in the context of uninterrupted service where Bluetooth technologies lag behind. By coalescing Bluetooth and 3D compass sensor models, we surmount the localizing tribulations and guarantee a preeminent solution for pedestrian indoor localization and navigation.
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paper_title: Optical all-pass filters for phase response design with applications for dispersion compensation

paper_content:

Lossless all-pass optical filters are introduced, which can approximate any desired phase response while maintaining a constant, unity amplitude response. Architectures using cascade and lattice structures based on ring resonators and cavities defined by reflectors are discussed. Two applications are presented: 1) for fiber dispersion compensation and 2) for compensation of the nonlinear phase response of narrow bandpass optical filters such as thin-film or Bragg grating filters. All orders of dispersion can be compensated in principle, and the filters are periodic so multiple channels can be compensated with a single device. The architectures are very compact compared to alternatives such as chirped Bragg gratings.
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Title: Survey of energy efficient tracking and localization techniques in buildings using optical and wireless communication media

Section 1: Introduction
Description 1: Provide an overview of the challenges related to energy consumption in buildings and the potential of modern technologies for energy savings.

Section 2: The SOWICI Project
Description 2: Describe the objectives, architecture, and expected benefits of the SOWICI project, including its approach to integrating optical and wireless communication for energy efficiency.

Section 3: Beamforming
Description 3: Discuss the techniques and applications of beamforming, with a focus on both narrowband and wideband beamforming, and its various implementations.

Section 4: Beamsteering
Description 4: Outline the different algorithms for adaptive beamforming, including temporal reference, spatial reference, and blind beamforming algorithms.

Section 5: Mobile Localization and Tracking
Description 5: Present a broad survey of mobile tracking techniques and their relevance to the SOWICI project, highlighting current advancements in mobile user localization.

Section 6: Classification of Localization schemes
Description 6: Classify localization schemes based on deployment area, wireless technology, physical parameters, location lookup tables, estimation techniques, localizing entities, and security considerations.

Section 7: Indoor Localization Techniques
Description 7: Examine various indoor localization techniques applicable to SOWICI, including GPS-based, RFID-based, cellular-based, UWB-based, WLAN-based, Bluetooth-based, and IEEE 802.15.4-based methods.

Section 8: Localization Selection Criteria
Description 8: Identify criteria for selecting appropriate localization techniques, considering factors like cost, accuracy, computational complexity, network impact, security, and energy consumption.

Section 9: Identifying the Appropriate Techniques for SOWICI
Description 9: Discuss the energy consumption focus of SOWICI, and evaluate the potential use of different beamforming, beamsteering, and tracking techniques within the project's framework.