Geolocation of a Known Altitude Target Using TDOA and GROA in the Presence of Receiver Location Uncertainty

This paper considers the problem of geolocating a target on the Earth surface using the target signal time difference of arrival (TDOA) and gain ratio of arrival (GROA) measurements when the receiver positions are subject to random errors. The geolocation Cramer-Rao lower bound (CRLB) is derived and the performance improvement due to the use of target altitude information is quantified. An algebraic geolocation solution is developed and its approximate efficiency under small Gaussian noise is established analytically. Its sensitivity to the target altitude error is also studied. Simulations justify the validity of the theoretical developments and illustrate the good performance of the proposed geolocation method

Passive acoustic method for aircraft localization

The present thesis investigates a passive acoustic method to locate maneuvering aircraft. The method is based on the acoustical Doppler effect, as a particular effect of the signals received by a mesh of spatially distributed microphones. A one-dimensional version of the ambiguity function allows for the calculation of the frequency stretch factor that occurs between the sound signals received by a pair of microphones. The mathematical expression for this frequency stretch is a function of the aircraft position and velocity, both of them being estimated by a genetic algorithm. The method requires only a minimum of seven microphones and the prior knowledge of the aircraft position and velocity at a given time. The advantages of the method are that it is suitable for all kind of aircraft, not only propeller-driven, and is not restricted to low heights above the ground. Its applicability could be, for instance, to supplement aircraft noise monitoring systems or to supervise small airports activities. This doctoral research includes the theoretical background of the method as well as the detailed description of its implementation. To assess the performance of the method, results from computer simulations are discussed. First of all, noise propagation is considered in a lossless medium, thus only geometrical spreading influences the sound emitted by the source traveling to the receivers. The accuracy of each step of the method has been evaluated and the results obtained reveal acceptable performance. Due to the large distances between microphones and the aircraft in flight, the atmospheric attenuation plays a major roll. Therefore, computer simulations have also been carried out under the assumption of an homogeneous but non lossless medium to evaluate the influence of the atmospheric absorption on the aircraft location. Under these conditions, the performance of the method with respect to the microphone distribution is discussed. Moreover, the location method has also been tested for a possible inaccuracy on the microphones synchronization. Finally, an outdoor experimental validation of the acoustic method has been carried out with a radio control airplane. The description of the experimental test is detailed in the present work as well as the results obtained.La tesi desenvolupa, implementa i valida un mètode acústic per a la localització d’aeronaus. El mètode es basa en l’efecte Doppler que es percep en els registres de diferents micròfons distribuïts al voltant d’un aeroport. La versió u-dimensional de la funció d’ambigüitat permet el còmput del factor de compressió o expansió que sorgeix entre els registres freqüencials d’ un parell de micròfons. Aquest factor Freqüencial es pot expressar matemàticament en funció de la posició i velocitat de l’aeronau, que s’estimen en aquesta tesi a partir d’algoritmes genètics. El mètode només requereix de set micròfons i el coneixement previ de la posició de l’avió en un moment donat. Els principals avantatges del mètode són que és un mètode vàlid per qualsevol tipus d’aeronau, no només per avions d’hèlix o helicòpters, i que no restringeix a vols de baixa alçada. La seva aplicació podria ser, per exemple, complementar un sistema de monitorització de soroll aeri o bé supervisar l’activitat dels aeroports petits que no disposen de sistemes de radar. Aquesta investigació inclou el desenvolupament teòric del mètode així com la descripció detallada de la seva implementació. Per tal d’avaluar l’efectivitat del mètode, es presenten i analitzen resultats obtinguts a partir de diverses simulacions. Com a primer cas, es considera que el so es propaga en un medi conservatiu, és a dir, el so que es propaga des de la font fins als receptors només es veu afectat per l’atenuació geomètrica. Sota aquest model senzill de propagació, s’ha analitzat l’accuracy de cada un dels passos del mètode i els resultats obtinguts posen de manifest una bona ... del mètode. Tenint en compte que les distàncies entre els micròfons i l’avió en vol són llargues, l’atenuació atmosfèrica influeix també en la propagació del so emès per l’avió. Per tant, el segon cas de simulacions que s’han dut a terme considera un medi de propagació homogeni i no conservatiu amb l’objectiu d’avaluar la influència de l’atenuació atmosfèrica en la localització acústica de l’aeronau. Sota aquestes condicions, també s’ha analitzat l’eficàcia del mètode en funció de la distribució de micròfons. A més, el mètode de localització s’ha posat a prova sota possibles errors en la sincronització dels set micròfons. Finalment, s’ha dut a terme una validació experimental del mètode amb una avioneta de radio control al Club Aeronàutic Egara. La descripció d’aquest test experimental es detalla en la tesis així com els resultats obtinguts que demostren la validesa satisfactòria del mètode

Spatial Compressive Sensing for MIMO Radar

We study compressive sensing in the spatial domain to achieve target localization, specifically direction of arrival (DOA), using multiple-input multiple-output (MIMO) radar. A sparse localization framework is proposed for a MIMO array in which transmit and receive elements are placed at random. This allows for a dramatic reduction in the number of elements needed, while still attaining performance comparable to that of a filled (Nyquist) array. By leveraging properties of structured random matrices, we develop a bound on the coherence of the resulting measurement matrix, and obtain conditions under which the measurement matrix satisfies the so-called isotropy property. The coherence and isotropy concepts are used to establish uniform and non-uniform recovery guarantees within the proposed spatial compressive sensing framework. In particular, we show that non-uniform recovery is guaranteed if the product of the number of transmit and receive elements, MN (which is also the number of degrees of freedom), scales with K(log(G))^2, where K is the number of targets and G is proportional to the array aperture and determines the angle resolution. In contrast with a filled virtual MIMO array where the product MN scales linearly with G, the logarithmic dependence on G in the proposed framework supports the high-resolution provided by the virtual array aperture while using a small number of MIMO radar elements. In the numerical results we show that, in the proposed framework, compressive sensing recovery algorithms are capable of better performance than classical methods, such as beamforming and MUSIC.Comment: To appear in IEEE Transactions on Signal Processin

Navigation with Limited Prior Information Using Time Difference of Arrival Measurements from Signals of Opportunity

The Global Positioning System (GPS) provides world-wide availability to high-accuracy navigation and positioning information. However, the threats to GPS are increasing, and many limitations of GPS are being encountered. Simultaneously, systems previously considered as viable backups or supplements to GPS are being shut down. This creates the need for system alternatives. Navigation using signals of opportunity (SoOP) exploits any signal that is available in a given area, regardless of whether or not the original intent of the signal was for navigation. Common techniques to compute a position estimate using SoOP include received signal strength, angle of arrival, time of arrival, and time difference of arrival (TDOA). To estimate the position of a SoOP receiver, existing TDOA algorithms require one reference receiver and multiple transmitters, all with precisely known positions. This thesis considers modifications to an existing algorithm to produce a comparable position estimate without requiring precise a priori knowledge of the transmitters or reference receiver(s). Using Amplitude Modulation (AM) SoOP, the effect of erroneous a priori data on the existing algorithm are investigated. A proof-of-concept for three new estimation algorithms is presented in this research. Two of the estimators successfully demonstrate comparable performance to the existing algorithm. This is demonstrated in six different transmitter environments using four different receiver configurations

A dynamic two-dimensional (D2D) weight-based map-matching algorithm

Existing map-Matching (MM) algorithms primarily localize positioning fixes along the centerline of a road and have largely ignored road width as an input. Consequently, vehicle lane-level localization, which is essential for stringent Intelligent Transport System (ITS) applications, seems difficult to accomplish, especially with the positioning data from low-cost GPS sensors. This paper aims to address this limitation by developing a new dynamic two-dimensional (D2D) weight-based MM algorithm incorporating dynamic weight coefficients and road width. To enable vehicle lane-level localization, a road segment is virtually expressed as a matrix of homogeneous grids with reference to a road centerline. These grids are then used to map-match positioning fixes as opposed to matching on a road centerline as carried out in traditional MM algorithms. In this developed algorithm, vehicle location identification on a road segment is based on the total weight score which is a function of four different weights: (i) proximity, (ii) kinematic, (iii) turn-intent prediction, and (iv) connectivity. Different parameters representing network complexity and positioning quality are used to assign the relative importance to different weight scores by employing an adaptive regression method. To demonstrate the transferability of the developed algorithm, it was tested by using 5,830 GPS positioning points collected in Nottingham, UK and 7,414 GPS positioning points collected in Mumbai and Pune, India. The developed algorithm, using stand-alone GPS position fixes, identifies the correct links 96.1% (for the Nottingham data) and 98.4% (for the Mumbai-Pune data) of the time. In terms of the correct lane identification, the algorithm was found to provide the accurate matching for 84% (Nottingham) and 79% (Mumbai-Pune) of the fixes obtained by stand-alone GPS. Using the same methodology adopted in this study, the accuracy of the lane identification could further be enhanced if the localization data from additional sensors (e.g. gyroscope) are utilized. ITS industry and vehicle manufacturers can implement this D2D map-matching algorithm for liability critical and in-vehicle information systems and services such as advanced driver assistant systems (ADAS)

Estimation of Source and Receiver Positions, Room Geometry and Reflection Coefficients From a Single Room Impulse Response

We propose an algorithm to estimate source and receiver positions, room geometry and reflection coefficients from a single room impulse response simultaneously. It is based on a symmetry analysis of the room impulse response. The proposed method utilizes the times of arrivals of the direct path, first order reflections and second order reflections. The proposed method is robust to erroneous pulses and non-specular reflections. It can be applied to any room with parallel walls as long as the required arrival times of reflections are available. In contrast to the state-of-art method, we do not restrict the location of source and receiver

3D Reflector Localisation and Room Geometry Estimation using a Spherical Microphone Array

The analysis of room impulse responses to localise reflecting surfaces and estimate room ge- ometry is applicable in numerous aspects of acoustics, including source localisation, acoustic simulation, spatial audio, audio forensics, and room acoustic treatment. Geometry inference is an acoustic analysis problem where information about reflections extracted from impulse responses are used to localise reflective boundaries present in an environment, and thus estimate the geometry of the room. This problem however becomes more complex when considering non-convex rooms, as room shape can not be constrained to a subset of possible convex polygons. This paper presents a geometry inference method for localising reflective boundaries and inferring the room’s geometry for convex and non-convex room shapes. The method is tested using simulated room impulse responses for seven scenarios, and real-world room impulse responses measured in a cuboid-shaped room, using a spherical microphone array containing multiple spatially distributed channels capable of capturing both time- and direction-of-arrival. Results show that the general shape of the rooms is inferred for each case, with a higher degree of accuracy for convex shaped rooms. However, inaccuracies gen- erally arise as a result of the complexity of the room being inferred, or inaccurate estimation of time- and direction-of-arrival of reflections