Wireless Positioning System Research Articles

Interference Mitigation Based on Bayesian Compressive Sensing for Wireless Localization Systems in Unlicensed Band

In wireless localization services, a wideband spectrum is required for high resolution ranging. For this purpose, unlicensed bands have received substantial interest for their potential to reduce deployment cost. However, in the unlicensed spectrum, narrowband interference is often present and distorts band-limited reference signals for channel impulse response (CIR) estimation that is a key component to determine the location of users. In this paper, we propose a new Bayesian compressive sensing (BCS) framework to estimate complex-valued targets and apply it to mitigate the impact of subband interference on CIR estimation accuracy. Our Bayesian approach estimates the CIR by maximizing the posterior probability of the CIR from frequency domain signals in which a portion of the signal is corrupted by the interference. Based on the BCS framework, we propose three interference mitigation techniques that utilize the information on interfered subbands differently. We demonstrate the superior performance of the proposed schemes by showing improved ranging error statistics using measured indoor channels in the 5.8 GHz band.

Adaptive synchronization in hidden broadband systems

Subject of Research. The paper deals with the method of adaptive synchronization in receiving devices of broadband communication systems of the hidden message exchange increasing the efficiency of computational capability usage of a receiving device. The research topicality is caused by the need in more effective usage of computing resources for accepting modules of broadband digital communication and radiolocation. Method. The proposed solution is an extension of sequential synchronization method being applied nowadays. The method consists of two synchronization stages: preliminary – hard, and subsequent – precise one. The entity of the proposed solution lies in computation of correlative function only in the area (window) near the expected central peak. The window movement along the accepted character sequence enables to find the actual peak position and to make synchronization. Decreasing of computing expenses is reached due to reduction of processed information volume. The method adaptivity is reached by exact retraining of synchronization during all communication session. The proposed solution is urgent for mobile systems of communication and radiolocation in condition of signal interference. Main Results. Simulation of synchronization system is carried out in the environment of Simulink (MATLAB). The signal created on the basis of a complex-valued matrix with the size equal to 3×4 with the special form of autocorrelation function is used as an example for synchronization. Model researches showed that the developed method enables to realize synchronization of transceiving system, without quitting the mode of the hidden (subnoise) message passing. It is shown that application of the developed method of the adaptive synchronization, gives the possibility to reduce significantly computational capability of a receiving device, necessary for synchronization. The number of operations in case of correlation function computation was decreased in 28 times as compared to a computation method in time over all range of counting and in 5 times concerning an algorithm of correlation function computation with the use of fast Fourier transform. Practical Relevance. Research results can find application in the design of receiving modules of broadband digital communication and radiolocation.

TrackCC: A Practical Wireless Indoor Localization System Based on Less-Expensive Chips.

This paper aims at proposing a new wireless indoor localization system (ILS), called TrackCC, based on a commercial type of low-power system-on-chip (SoC), nRF24LE1. This type of chip has only l output power levels and acute fluctuation for a received minimum power level in operation, which give rise to many practical challenges for designing localization algorithms. In order to address these challenges, we exploit the Markov theory to construct a -sized state transition matrix to remove the fluctuation, and then propose a priority-based pattern matching algorithm to search for the most similar match in the signal map to estimate the real position of unknown nodes. The experimental results show that, compared to two existing wireless ILSs, LANDMARC and SAIL, which have meter level positioning accuracy, the proposed TrackCC can achieve the decimeter level accuracy on average in both line-of-sight (LOS) and non-line-of-sight (NLOS) senarios.

Improved Localization Algorithms for Indoor TOA-based Wireless Localization System

Improved Localization Algorithms for Indoor TOA-based Wireless Localization System

Performance Enhancement of MEMS-Based INS/UWB Integration for Indoor Navigation Applications

Inertial navigation system (INS) has an increasingly important role in indoor navigation, which mainly uses inertial measurement units based on a micro electro mechanical system (MEMS) to acquire data, and which is independent of the external environment. However, INS has serious accumulated errors, and thus, it was often integrated with wireless location systems (WLSs), such as ultra wideband (UWB) system, in order to enhance the position performance. Namely, MEMS-based inertial sensors have the problem of random errors. Besides, a UWB system is vulnerable to external environment conditions, such as the non-line-of-sight (NLOS) factor and multipath effects, and thus, many outliers are produced. In order to improve the overall performance of the INS/UWB system, this paper proposes the three-tier approach based on: 1) analysis and pre-filtering of random errors of MEMS-based inertial sensors, and use of a complementary filter to provide attitude information of navigation system; 2) use of the anti-magnetic ring (AMR) to eliminate the outliers from the UWB system in NLOS environment; and 3) improvement of positioning accuracy at information fusion level using the double-state adaptive Kalman filter. The proposed approach was verified by experiments that included AMR test and filter test. The obtained results have validated the proposed method efficiency.

Single anchor node real-time positioning algorithm based on the antenna array

This article presents an anchor node based on directional antenna array and reports the design of an automatic test system. The antenna radiation characteristics and the wireless channel model are studied first, followed by the evaluation of a single anchor node localization algorithm for wireless sensor network real-time positioning on the base of antenna radiation modeling and radio channel propagation model research then. Finally, the algorithm is evaluated by experiments in real environments. Experimental results show that the algorithm positioning accuracy could reach 1 m, and angular positioning accuracy error is less than 20° with no data exchange required during the positioning process. Hence, the wireless data transmission protocol complexity is reduced with improved real-time performance. This study is expected to provide technical references for the method research of wireless sensor network real-time positioning and new positioning system in practical applications.

Backscattering of decametric waves on magnetically oriented ionosphere inhomogeneities

The method of study of magnetically oriented ionosphere inhomogeneities based on the analysis of radar decametric emission backscattering on inhomogeneities is proposed. It is shown that certain conditions, including the orientation of the propagation route relative to the Earth’s magnetic field lines and the polarization and frequency of the emitted wave, make possible resonant backscattering of radiolocation system emission on magnetically oriented ionosphere inhomogeneities. The paper presents the results of experimental observation of scattering in Kamchatka Peninsula. They demonstrated the opportunity to evaluate the extension of the scattering region, the vertical and horizontal components of the velocities of magnetically oriented inhomogeneities, and the frequency dependence of these parameters.

A Novel Automated Construction Method of Signal Fingerprint Database for Mobile Robot Wireless Positioning System

The indoor wireless positioning system for a mobile robot employing fingerprinting technique is made in two phase, offline, i.e., collecting reference data for database, and online, i.e., matching the unknown data to those in the database. It is commonly known that the positioning accuracy is increased with the larger number of the reference locations. This has made the offline phase a tedious works, where laborious efforts are needed to construct the database. Thus, automatic database construction is desired in order to minimize the human efforts. This paper described the Signal Propagated Modified Shepard’s Method (SP-MSM) to construct the database by means of interpolating the missing wireless data using for mobile robot application. By introducing the selection probability, reference locations are identified and database is constructed. We found that over all 64 test locations, the proposed SP-MSM method outperform other interpolation method at 52% locations. In addition, the usage of low pass filter has greatly suppressed the fluctuation problem caused by unpredicted behavior of the wireless signal.

Study of Radiated Emission from Wireless Positioning System and the Strategies to Minimize the Radiations

The objective of this research work is to develop Wireless Positioning System compatible with CISPR EMI/EMC standard. The system should work satisfactorily under dynamic and environmental conditions related to automotive platforms. This paper presents the measurement of Radiated Emission from GPS based Wireless Positioning/Localization System. It also deals with the implementation of the shielding techniques in order to make the system compatible with the EMC requirements as per CISPR EMI/EMC Standard. In the current scenario, the GPS based Wireless Positioning System is an essential part in the application areas such as logistics, public transports, naval ships, railways and stringent environment like defense vehicles. Due to its usefulness in daily life, the system has been considered as the test model for this research work. The reliability prediction for the model has been done with MTBF and Failure Rate estimations. The Radiated Emission level has been investigated for GPS based Vehicle Positioning System at the Centre for Electronics Test Engineering, Pune, India and Automotive Research Association of India (ARAI), Pune, India. This model was first validated in the GTEM Cell and further it was tested in the EMI chamber. It has been observed that RE level at certain frequency bands was found to be exceeding the specified limits as per the EMC standard. In this paper, few innovative techniques like shielding with enclosures has been proposed and implemented to reduce the level of radiated emission. The shielding enclosure of aluminum and copper were designed and implemented. Also, simulation of the stress level has been done for the copper enclosure with ANSYS software. The results of re-validating the GPS based system with aluminum and copper enclosures are presented here. After re-validation, radiated emission level was found to be reduced by around 10–40 dB making the system compatible with the EMI/EMC CISPR standards.

Efficient Ambiguity Resolution in Wireless Localization Systems

Wireless communication is widely used for node localization in various automation domains. Schemes based on time difference of arrival (TDOA) are a good compromise of achievable accuracy and implementation effort. Due to restrictions on possible reference sensor positions in industrial environments, the geometric conditions between reference and mobile nodes locations are often difficult. Consequently, iterative algorithms can fail or result in high computational effort. Exact direct methods introduce no additional errors, but can result in a valid pair of solutions. Existing direct methods thus either rely on a priori information to sort out one of those two solutions, or revert to nonexact linearization approaches of the underlying hyperbolic equations. In this work, we present a direct approach that applies exact direct methods, and resolves the ambiguous pairs of solutions without a priori information. Its divide and conquer structure and the high computational efficiency of the available exact direct methods makes it a very good candidate for fast parallel computing in distributed sensor networks. The performance is compared to the Cramer–Rao lower bound, to the iterative Gauss–Newton method and to another direct method. The new method is presented for the TDOA scheme, but can also be applied to time of arrival, or any other range-based scheme.

ER-CRLB: An Extended Recursive Cramér–Rao Lower Bound Fundamental Analysis Method for Indoor Localization Systems

We propose an extended recursive Cramér-Rao lower bound (ER-CRLB) method as a fundamental tool to analyze the performance of wireless indoor localization systems. The ER-CRLB fully models the complicated indoor environment, e.g., the sequential position state propagation, the target-anchor geometry effect, the non-line-of-sight (NLOS) identification, and the related prior information. First, we use an abstract function to represent the entire wireless localization system model. Then, the unknown vector of the ER-CRLB consists of two parts: The first part is the estimated vector, and the second part is the auxiliary vector that helps improve the estimation accuracy. Accordingly, the Fisher information matrix (FIM) of the ER-CRLB is divided into two parts, namely, the state matrix and the auxiliary matrix. Based on this idea, ER-CRLB can be a practical fundamental limit to denote the system which fuses multiple information in the complicated environment, e.g., recursive Bayesian estimation based on the hidden Markov model, the map matching method and NLOS identification and mitigation methods. When only a small set of unknown vectors is estimated in the system, the ER-CRLB is equivalent to the other CRLBs of the wireless indoor localization system as well. However, the ER-CRLB is more adaptable than other CRLBs when considering more unknown important factors. We employ the ER-CRLB to analyze the time-of-arrival (TOA) range-based indoor localization system. The influence of the hybrid line-of-sight (LOS)/NLOS channels, the building layout information, and the relative height differences between the target and anchors are analyzed. It is demonstrated that the ER-CRLB exploits all the available information for the indoor localization systems and serves as a fundamental limit of the unbiased estimation accuracy.

GuideLoc: UAV-Assisted Multitarget Localization System for Disaster Rescue

Locating trapped targets using the signals of wireless devices such as mobile phones carried by targets is increasingly becoming the preferred scheme for disaster rescue. However, the accuracy of radio-localization technology currently adopted in the rescue is not high enough. To solve such problems, researchers proposed the approaches of Warwalking or Wardriving. However, both approaches are all limited by application scenarios. This paper proposes GuideLoc, a highly efficient aerial wireless localization system, which uses the target guiding technology based on region division. GuideLoc allows an unmanned aerial vehicle (UAV) to fly over a target device and provide position coordinates of the UAV as the target location information. During the process of positioning targets, based on the result of regional division, GuideLoc uses a number of fixed antennas to get the received signal strength indicator (RSSI) and angle of arrival (AOA) information of the target and estimates the target location using the information and correspondingly controls the UAV to fly towards the target. Averaging method is also applied for determining coordinates of the target. Experiment results show that GuideLoc can in short time achieve 2.7-meter positioning accuracy in average. Compared with other wireless localization methods using UAVs proposed in the literature, it shortened the flight distance by more than 50%. In addition, energy efficiency is also improved significantly.

Joint Allocation of Spectral and Power Resources for Non-Cooperative Wireless Localization Networks

Network localization is a key feature in many wireless services and applications. In typical range-based non-cooperative localization techniques, agents try to perform position estimation through ranging with respect to anchors with known positions. Based on the definition of squared positional error bound, the localization accuracy can be determined by the transmit power, carrier frequency, and signal bandwidth. This paper analyzes the joint power and spectrum allocation (JPSA) optimization problems in resource restricted wireless localization systems. We first formulate both optimal interference-free and interference affected JPSA problems. We then formulate the robust counterparts of the problems in the presence of uncertainty of the agents’ positions. Since all JPSA problems are non-convex, we show that they can be modeled and solved as geometric programming (GP) by proper approximations. Numeric results validate our analysis and show that the developed algorithms are able to find solutions close to the global optimum in the investigated cases. We can find the optimal/robust resource deployment in non-cooperative wireless localization networks based on the proposed frameworks.

Practical Performance Analysis for Multiple Information Fusion Based Scalable Localization System Using Wireless Sensor Networks

In practical localization system design, researchers need to consider several aspects to make the positioning efficiently and effectively, e.g., the available auxiliary information, sensing devices, equipment deployment and the environment. Then, these practical concerns turn out to be the technical problems, e.g., the sequential position state propagation, the target-anchor geometry effect, the Non-line-of-sight (NLOS) identification and the related prior information. It is necessary to construct an efficient framework that can exploit multiple available information and guide the system design. In this paper, we propose a scalable method to analyze system performance based on the Cramér–Rao lower bound (CRLB), which can fuse all of the information adaptively. Firstly, we use an abstract function to represent all of the wireless localization system model. Then, the unknown vector of the CRLB consists of two parts: the first part is the estimated vector, and the second part is the auxiliary vector, which helps improve the estimation accuracy. Accordingly, the Fisher information matrix is divided into two parts: the state matrix and the auxiliary matrix. Unlike the theoretical analysis, our CRLB can be a practical fundamental limit to denote the system that fuses multiple information in the complicated environment, e.g., recursive Bayesian estimation based on the hidden Markov model, the map matching method and the NLOS identification and mitigation methods. Thus, the theoretical results are approaching the real case more. In addition, our method is more adaptable than other CRLBs when considering more unknown important factors. We use the proposed method to analyze the wireless sensor network-based indoor localization system. The influence of the hybrid LOS/NLOS channels, the building layout information and the relative height differences between the target and anchors are analyzed. It is demonstrated that our method exploits all of the available information for the indoor localization systems and serves as an indicator for practical system evaluation.

Wireless Indoor Localization Systems and Techniques: Survey and Comparative Study

<p>The popularity, great influence and huge importance made wireless indoor localization has a unique touch, as well its wide successful on positioning and tracking systems for both human and assists also contributing to take the lead from outdoor systems in the scope of the recent research works. In this work, we will attempt to provide a survey of the existing indoor positioning solutions and attempt to classify different its techniques and systems. Five typical location predication approaches (triangulation, fingerprinting, proximity, vision analysis and trilateration) are considered here in order to analysis and provide the reader a review of the recent advances in wireless indoor localization techniques and systems to have a good understanding of state of the art technologies and motivate new research efforts in this promising direction. For these reasons, existing wireless localization position systems and location estimation schemes are reviewed. We also made a comparison among the related techniques and systems along with conclusions and future trends to identify some possible areas of enhancements. </p>

Stochastic Cooperative Decision Approach for Studying the Symmetric Behavior of People in Wireless Indoor Location Systems

Nowadays, several wireless location systems have been developed in the research world. The goal of these systems has always been to find the greatest accuracy as possible. However, if every node takes data from the environment, we can gather a lot of information, which may help us understand what is happening around our network in a cooperative way. In order to develop this cooperative location and tracking system, we have implemented a sensor network to capture data from user devices. From this captured data we have observed a symmetry behavior in people’s movements at a specific site. By using these data and the symmetry feature, we have developed a statistical cooperative approach to predict the new user’s location. The system has been tested in a real environment, evaluating the next location predicted by the system and comparing it with the next location in the real track, thus getting satisfactory results. Better results have been obtained when the stochastic cooperative approach uses the transition matrix with symmetry.

Optimum Placement of Wireless Access Point for Mobile Robot Positioning in an Indoor Environment

[abstFig src='/00280002/07.jpg' width=""300"" text='The placement objective so that the particular arrangement could provide enough signal data to the mobile robot' ]The Wireless Positioning System (WPS) has gained increasing attention for mobile robot applications in indoor environments over conventional on-board sensors. This is mainly due to their cost effectiveness as well as adaptability for future use. Many literatures on WPS adapted existing wireless infrastructures such as WiFi for mobile robot usage, resulting in relatively impractical accuracy for mobile robot application. A systematic technique must be sought in order to place the wireless nodes where coverage could be maximized and be suitable for a mobile robot positioning system via fingerprinting technique. We propose an effective and simple means to optimize wireless access point (AP) placement. Simulation results by ITU-R P.1238 MWF signal propagation model with automatic wall crossing computation have ensured the maximum coverage for human users using a minimum number of wireless nodes as possible. The mobile robot positioning error employing the weightedk-nearest neighbor algorithm (WKNN) with the average signal strength as fingerprint database yielded significant results when the proposed placements are used over symmetrical placements.

An Effective TOA-based Localization Method with Adaptive Bias Computation

Abstract Inthispaper,weproposeaneffectivetime-of-arrival(TOA)-basedlocalizationmethodwithadaptivebiascomputationinindoorenvironments.Thegoalofthelocalizationistoestimateanaccuratetarget’slocationinwirelesslocalizationsystem.However, inindoor environments, non-line-of-sight (NLOS)errorsblockthesignal propagationbetweentargetdeviceandbasestation.TheNLOSerrorshavesignificanteffectsonrangingbetweentwodevicesforwirelesslocalization.InTOA-basedlocalization,findingthetarget'slocationinsidetheoverlappedareaintheTOA-circlesisdifficult.Wepresentaneffectivelocalizationmethodusingcompensated distance with adaptive bias computation. The proposed method is possible for the target'slocationtoestimateanaccuratelocationintheoverlappedareausingthemeasureddistanceswithsubtractedadaptivebias.Throughlocalizationexperimentsinindoorenvironments,estimationerrorisreducedcomparingtotheconventionallocalizationmethods.Keywords:WirelessLocalization,Time-of-Arrival(TOA),Non-Line-of-Sight(NLOS)errors,AdaptiveBiasComputation,WirelessSensorNetworks*AgencyforDefenceDevelopment,Koreae-mail:milkyfacer@gmail.comTel:+82-55-540-6818ManuscriptreceivedNov20,2015;revisedDec28,2015;acceptedDec28,2015ThisisanOpen-Accessarticledistributedunderthetermsofthe Creative Commons Attribution Non-CommercialLicense(http://creativecommons.org/licenses/by-nc/3.0) whichpermits unrestricted non-commercial use, distribution, andreproductioninanymedium,providedtheoriginalworkisproperlycited.ISSN: 1226-7244 (Print)ISSN: 2288-243X (Online)논문번호 16-01-01

Cubic-Receiver-Based Indoor Optical Wireless Location System

A cubic-receiver-based indoor optical wireless location system is proposed in this paper. The cubic receiver arranging five photodiodes (PDs) as a cubic structure is used as photodetector to measure the angles of arrival (AOAs) of the incident light from multiple light-emitting diodes. Due to the cubic structure, the AOA has a simple relationship with the differential received photocurrents; hence, the AOA can be conveniently obtained by measuring the differential received photocurrents of five PDs. This system is shown to have several advantages, such as wide field of view (FOV), low algorithm complexity, and high accuracy. The system performance is numerically simulated, and the experiment shows that a mean positioning error of 3.3 cm can be achieved.

Optimal Jammer Placement in Wireless Localization Systems

In this study, the optimal jammer placement problem is proposed and analyzed for wireless localization systems. In particular, the optimal location of a jammer node is obtained by maximizing the minimum of the Cramer-Rao lower bounds (CRLBs) for a number of target nodes under location related constraints for the jammer node. For scenarios with more than two target nodes, theoretical results are derived to specify conditions under which the jammer node is located as close to a certain target node as possible, or the optimal location of the jammer node is determined by two of the target nodes. Also, explicit expressions are provided for the optimal location of the jammer node in the presence of two target nodes. In addition, in the absence of distance constraints for the jammer node, it is proved, for scenarios with more than two target nodes, that the optimal jammer location lies on the convex hull formed by the locations of the target nodes and is determined by two or three of the target nodes, which have equalized CRLBs. Numerical examples are presented to provide illustrations of the theoretical results in different scenarios.