Recently, indoor geolocation technologies has been attracting tremendous attention. For indoor environments, the fine time resolution of ultra-wideband (UWB) signals enables the potential of accurate distance measurement of the direct path (DP) between a number of reference sources and the people or assets of interest. However, Once the DP is not available or is shadowed, substantial errors will be introduced into the ranging measurements, leading to large localization errors when measurements are combined from multiple sources. The measurement accuracy in undetected direct path (UDP) conditions can be improved in some cases by exploiting the geolocation information contained in the indirect path measurements. Therefore, the dynamic spatial behavior of paths is an important issue for positioning techniques based on TOA of indirect paths. The objectives of this thesis are twofold. The first is to analyze the sensitivity of TOA estimation techniques based on TOA of the direct path. we studied the effect of distance, bandwidth and multipath environment on the accuracy of various TOA estimation techniques. The second is to study the sensitivity of multipath parameters pertinent to TOA estimation techniques based on the TOA of the indirect paths. We mainly looked into the effect of distance, bandwidth, threshold for picking paths, and multipath environment on the number of multipath components(MPCs) and path persistency. Our results are based on data from a new measurement campaign conducted on the 3rd floor of AK laboratory. For the TOA estimation techniques based on DP, the line of sight (LOS) scenario provides greatest accuracy and these TOA estimation techniques are most sensitive to bandwidth availability in obstructed line of sight (OLOS) scenario. All the TOA estimation algorithms perform poorly in the UDP scenario although the use of higher bandwidth can reduce the ranging error to some extent. Based on our processed results, The proposal for selecting the appropriate TOA estimation technique with certain constrains is given. The sensitivity study of multipath parameters pertinent to indirect-path-based TOA estimation techniques shows that the number of MPCs is very sensitive to the threshold for picking paths and to the noise threshold. It generally decreases as the distance increase while larger bandwidth always resolves more MPCs. The multipath components behave more persistently in line of sight (LOS) and obstructed line of sight (OLOS) scenarios than in UDP scenarios, and the use of larger bandwidth and higher threshold for picking paths also result in more persistent paths.

La thèse a porté sur la localisation de mobile pour les systèmes UMTS-FDD. Il s'agit d'un sujet qui intéresse de plus en plus les opérateurs, notamment dans le cas de système UMTS-FDD où il existe très peu de réseaux réels. Les différentes approches permettant de localiser un émetteur ont ainsi été envisagées, et plus particulièrement, celles basées sur les mesures de puissances, les temps d'arrivée (TOA) en liaison descendante ou encore celles basées sur les angles d'arrivée (AOA) et sur toute combinaison AOA-TOA. Pour ces différentes approches, nous nous sommes intéressés aux deux principales sources d'erreur pouvant dégrader les performances de la localisation : -l'absence de trajet direct qui est une des caractéristiques des systèmes radio-mobile. -le problème d'écoute, qui est inhérent au système UMTS-FDD. A ces deux problèmes, nous avons proposé des solutions pour les differentes approches de localisation, qui soient à la fois précises et facile à mettre en oeuvre au niveau de la norme.

With the rapid development of wireless networking technology and the great growth of service demand, accurate wireless location estimation has gained considerable attention. Most wireless location system may suffer from non-line-of-sight (NLOS) propagation error, which leads to a severe degradation of position accuracy. In this thesis, we propose a hybrid TOA/AOA (time of arrival/ angle of arrival) non-line-of-sight identification and wireless location technology to cope with NLOS condition. This algorithm can simultaneously determine the number of line-of-sight (LOS) base stations (BSs) and identify them. The identification part is to collect all TOA and AOA parameters from all BSs and to use residual information to detetmine whether the NLOS error is present in measurements. The localization method only processes the LOS measurements to avoid the NLOS error and increases position accurary. The simulation results show that the location system with TOA measurements can identify three or more LOS-BSs. The system has a high identification accuracy when the number of LOS-BSs is more than three. When the number of LOS-BSs is three, the degraded identification capability leads to larger position errors. When the AOA information is available in the positioning system, the TOA is combined with AOA because the property of the AOA localization method which needs only two measurements to locate the MS makes the location system capable of identifying two LOS-BSs. When the number of LOS-BSs is two, the combination of TOA and AOA measurements maintains a higher NLOS identification accuracy and make its location performance remarkably promoted.

For most time-based positioning techniques, synchronization between the objectsin the system is of great importance. GPS (global positioning system) signalshave been found very useful in this area. However, there are some shortcomingsof these satellite signals, making the system vulnerable. The aim of this masterthesis is to investigate an alternative method for synchronization, independent ofGPS signals, which could be used as a complement. The proposed method takesadvantage of the broadcast signals from telecommunication towers, and use themfor calculation of the synchronization error between two receivers. By looking atthe time difference between arrival times at the receivers, and compare it to thetrue time difference, the synchronization error can be found. A precondition isthat the locations of the receivers as well as the tele tower are known beforehand,so that the true time difference can be calculated using geometry.The arrival times are determined through correlation between the received signalsand known training bits, which are a part of the transmission sequence. Forverification, experiments were made on localization of a mobile phone in theGSM (global system of mobile communications) network.This researchwas a collaboration with FOI, the Swedish Defense Research Agency,where most of the work was done.

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / An improved ionospheric delay correction model for a transionospheric electromagnetic pulse (EMP) is used for estimating the total-electron-content (TEC) profile of the path and accurate ranging of the EMP source. For a known pair of time of arrival (TOA) measurements at two frequency channels, the ionospheric TEC information is estimated using a simple numerical technique. This TEC information is then used for computing ionospheric group delay and pulse broadening effect correction to determine the free space range. The model prediction is compared with the experimental test results. The study results show that the model predictions are in good agreement with the test results.

Our increased reliance on localization devices such as GPS navigation has led to an increased demand for localization solutions in all environments, including indoors. Indoor localization has received considerable attention in the last several years for a number of application areas including first responder localization to targeted advertising and social networking. The difficult multipath encountered indoors degrades the performance of RF based localization solutions and so far no optimal solution has been published. This dissertation presents an algorithm called Coherent Array Reconciliation Tomography (CART), which is a Direct Positioning Algorithm (DPA) that incorporates signal fusion to perform a simultaneous leading edge and position estimate for a superior localization solution in a high multipath environment. The CART algorithm produces position estimates that are near optimal in the sense that they achieve nearly the best theoretical accuracy possible using an Impulse Radio (IR) Ultra-Wideband (UWB) waveform. Several existing algorithms are compared to CART including a traditional two step Leading Edge Detection (LED) algorithm, Singular value Array Reconciliation Tomography (SART), and Transactional Array Reconciliation Tomography (TART) by simulation and experimentation. As shown under heavy simulated multipath conditions, where traditional LED produces a limited solution and the SART and TART algorithms fail, the CART algorithm produces a near statistically optimal solution. Finally, the CART algorithm was also successfully demonstrated experimentally in a laboratory environment by application to the fire fighter homing device that has been a part of the ongoing research at Worcester Polytechnic Institute (WPI).

The major problems encountered in wireless location are the effects caused by non-line of sight (NLOS) propagation and multipath interference. In the thesis, we propose an approach to mitigate NLOS error. First of all, we use improved biased Kalman filter (IBKF) based on time of arrival (TOA) measurement to identify and mitigate NLOS error. Applying the statistic characteristic that the standard deviation of the NLOS propagation errors is generally much larger than that of measurement noises in the LOS condition, we combine hypothesis test and sliding window to identify NLOS error. According to the feedback identification and the calculated standard deviation, IBKF switches biased or unbiased to process TOA measurement. Nevertheless, the performance of IBKF-TOA is still affected slightly by NLOS error. Since extended Kalman filter (EKF) based on received signal strength (RSS) measurement is designed for prespecified environments, the effect of NLOS mitigation is more obvious. Moreover, EKF-RSS not only exists higher error probability in NLOS identification, but also needs longer time to converge in the cases that start with NLOS. Comparing IBKF-TOA with EKF-RSS, we adopt interacting multiple model (IMM) in the proposed data fusion structure for processing TOA and RSS measurements. In the proposed scheme, we reserve the basic IMM structure and add the step of NLOS identification into basic IMM structure. By accurate NLOS identification results and soft decision of IMM, the proposed scheme will switch to adequate filter mode and obtain better estimation. With simulation in UWB channel, the analysis and performance evaluation show advantages and disadvantages of using IBKF-TOA, EKF-RSS, and proposed scheme. Simulation results reveal that NLOS error can be mitigated effectively by data fusion of TOA and RSS measurements and can achieve high accuracy in positioning and tracking.

The fine time resolution of ultra wide-band (UWB) systems enables applications in TOA/TDOA based high precision wireless indoor location. The main purpose of this thesis is to investigate TOA estimation in multi-band OFDM UWB systems. We propose an effective and simplified TOA estimation algorithm for multi-band OFDM standard. The proposed algorithm is based on the generalized maximum-likelihood (GML) algorithm. The TOA estimation algorithm utilizes the preamble signal in multi-band OFDM system. We modify the realization method of GML algorithm according to the preamble signal properties and apply it to multi-band OFDM system. From simulation results, by comparing with cross correlation algorithm and the original GML algorithm, the proposed algorithm has ability to mitigate multipath interference and improves TOA estimation accuracy. In this thesis we also discuss the thresholds setting and SNR estimation problems to make the proposed algorithm more realizable.

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This thesis presents a feasibility study on unobtrusive localization of GSM en- abled cellphones using a Fake Base Station (FBS). An FBS is a radio transceiver that emulates the behaviour of a legitimate GSM Base Station (BS) to fool unal- tered cellphones to connect with it. This feasibility study investigates how an FBS can be utilized to estimate positions of connected cellphones in an area of interest. We present a proof of concept system that consists of a mobile FBS that measures the Time Of Arrival (TOA) and Received Signal Strength (RSS) to a cell- phone. The positions of the mobile FBS are determined with GPS. We employ calibration-free localization algorithms as we assume unknown environments and unknown hardware. Our experiments in an outdoor 180x100 m2 Line-Of- Sight (LOS) environment show that our calibration-free localization algorithms provide an average localization error less than 10 meters, which is sufficient for most applications of interest. In addition, our experiments show that RSS-based localization outperforms TOA-based localization when the average distance be- tween the FBS and cellphone is roughly 50 meters. Our experiments show that TOA-based localization outperforms RSS-based localization when the average dis- tance increases to roughly 75 meters. This research is part of the Smart Savannah project in which a wide range of different surveillance systems are developed to protect rhinos from poachers. We envision that our localization system can be used to detect and localize these poachers in an unobtrusive way. In addition, we envision that our localization sys- tem can be used in Search And Rescue (SAR) operations to estimate the positions of cellphones of missing persons. / Detta examensarbete undersöker möjligheten att lokalisera mobiltelefoner med GSM teknologi genom att använda en Falsk Basstation (FBS). En FBS är en radio transceiver som emulerar beteendet hos en legitim GSM basstation för att lura omodifierade mobiltelefoner att ansluta till den. Undersökningen tar reda på hur en FBS kan användas för att estimera positionerna av anslutna mobiltelefoner inom ett målområde. För att undersöka detta har ett Proof-Of-Concept-system ta- gits fram. Systemet består av en mobil FBS som som mäter propageringstid (TOA) och mottagen signalstyrka (RSS). FBS:ens positioner bestäms med GPS. Systemet använder kalibreringsfria algoritmer för lokalisering, då vi antar att miljön och mobiltelefonernas hårdvara är okänd. Tester av systemet har utförts utomhus i ett 180x100 m2 Line-Of-Sight-område. Dessa tester visar att lokaliseringsalgorit- merna ger ett genomsnittligt fel på mindre än 10 meter. Detta anses vara till- räckligt för de flesta tillämpningar av intresse. Utöver detta visar även testerna att RSS-baserad lokalisering ger bättre resultat än TOA-baserad lokalisering när medelavståndet mellan FBS och mobiltelefon är omkring 50 meter. TOA-baserad lokalisering ger däremot ett bättre resultat än RSS-baserad lokalisering när me- delavståndet ökar till omkring 75 meter. Denna undersökning är en del av Smart Savannah projektet som innefattar flera olika övervakningssystem, utvecklade för att skydda noshörningar från tjuv- skyttar. Målet med vårt lokaliseringssystem är att det ska kunna användas för att upptäcka och lokalisera tjuvskyttar utan deras vetskap. Vi tror även att lokalise- ringssystemet kan användas vid eftersökning- och räddnings-operationer för att lokalisera försvunna personers mobiltelefoner. / Project Ngulia