A survey on acoustic positioning systems for location-based services

Positioning systems have become increasingly popular in the last decade for location-based services, such as navigation, and asset tracking and management. As opposed to outdoor positioning, where the global navigation satellite system became the standard technology, there is no consensus yet for indoor environments despite the availability of different technologies, such as radio frequency, magnetic field, visual light communications, or acoustics. Within these options, acoustics emerged as a promising alternative to obtain high-accuracy low-cost systems. Nevertheless, acoustic signals have to face very demanding propagation conditions, particularly in terms of multipath and Doppler effect. Therefore, even if many acoustic positioning systems have been proposed in the last decades, it remains an active and challenging topic. This article surveys the developed prototypes and commercial systems that have been presented since they first appeared around the 1980s to 2022. We classify these systems into different groups depending on the observable that they use to calculate the user position, such as the time-of-flight, the received signal strength, or the acoustic spectrum. Furthermore, we summarize the main properties of these systems in terms of accuracy, coverage area, and update rate, among others. Finally, we evaluate the limitations of these groups based on the link budget approach, which gives an overview of the system's coverage from parameters such as source and noise level, detection threshold, attenuation, and processing gain.Agencia Estatal de InvestigaciónResearch Council of Norwa

Static and dynamic evaluations of acoustic positioning system using TDMA and FDMA for robots operating in a greenhouse

Acoustic positioning system has great potential to be applied in a greenhouse due to its centimeter-level accuracy, low cost, and ability of extensive greenhouse coverage. Spread Spectrum Sound-based local positioning system (SSSLPS) was proposed to be a navigation tool for multiple agricultural robots by the authors' research team. However, to increase the system capacity for positioning multiple robots in a greenhouse, the near-far problem caused by the interference between speakers needs to be overcome. The use of different access methods, Time Division Multiple Access (TDMA) or Frequency Division Multiple Access (FDMA), is essential in the SSSLPS system for solving the near-far problem. The static positioning in a greenhouse was first evaluated by setting different parameters to determine the optimal signal setting for a dynamic experiment. From that, the moving robot tests were added with a motion capture system and tested the performance of TDMA and FDMA. The results demonstrated that TDMA can be used in a stationary sound-based positioning system with 12.2 mm accuracy, but it has a time delay problem in dynamic positioning. A simulation was designed to mimic the position error increases with different moving speeds. Although FDMA has the sound damping problem in high-frequency regions creating a peak detection issue, it achieved a higher accuracy with an average position error of 62.1 mm compared to 180.3 mm of TDMA. This study shows that the TDMA method is suitable for static measurements, while the FDMA method is suitable for measuring dynamic objects and controlling mobile robots

3D indoor positioning of UAVs with spread spectrum ultrasound and time-of-flight cameras

Este trabajo propone el uso de un sistema híbrido de posicionamiento acústico y óptico en interiores para el posicionamiento 3D preciso de los vehículos aéreos no tripulados (UAV). El módulo acústico de este sistema se basa en un esquema de Acceso Múltiple por División de Código de Tiempo (T-CDMA), en el que la emisión secuencial de cinco códigos ultrasónicos de espectro amplio se realiza para calcular la posición horizontal del vehículo siguiendo un procedimiento de multilateración 2D. El módulo óptico se basa en una cámara de Tiempo de Vuelo (TOF) que proporciona una estimación inicial de la altura del vehículo. A continuación se propone un algoritmo recursivo programado en un ordenador externo para refinar la posición estimada. Los resultados experimentales muestran que el sistema propuesto puede aumentar la precisión de un sistema exclusivamente acústico en un 70-80% en términos de error cuadrático medio de posicionamiento.This work proposes the use of a hybrid acoustic and optical indoor positioning system for the accurate 3D positioning of Unmanned Aerial Vehicles (UAVs). The acoustic module of this system is based on a Time-Code Division Multiple Access (T-CDMA) scheme, where the sequential emission of five spread spectrum ultrasonic codes is performed to compute the horizontal vehicle position following a 2D multilateration procedure. The optical module is based on a Time-Of-Flight (TOF) camera that provides an initial estimation for the vehicle height. A recursive algorithm programmed on an external computer is then proposed to refine the estimated position. Experimental results show that the proposed system can increase the accuracy of a solely acoustic system by 70–80% in terms of positioning mean square error.• Gobierno de España y Fondos para el Desarrollo Regional Europeo. Proyectos TARSIUS (TIN2015-71564-C4-4-R) (I+D+i), REPNIN (TEC2015-71426-REDT) y SOC-PLC (TEC2015-64835-C3-2-R) (I+D+i) • Junta de Extremadura, Fondos FEDER y Fondo Social Europeo. Proyecto GR15167 y beca predoctoral 45/2016 Exp. PD16030peerReviewe

Ultrasound Indoor Positioning System Based on a Low-Power Wireless Sensor Network Providing Sub-Centimeter Accuracy

This paper describes the TELIAMADE system, a new indoor positioning system based on time-of-flight (TOF) of ultrasonic signal to estimate the distance between a receiver node and a transmitter node. TELIAMADE system consists of a set of wireless nodes equipped with a radio module for communication and a module for the transmission and reception of ultrasound. The access to the ultrasonic channel is managed by applying a synchronization algorithm based on a time-division multiplexing (TDMA) scheme. The ultrasonic signal is transmitted using a carrier frequency of 40 kHz and the TOF measurement is estimated by applying a quadrature detector to the signal obtained at the A/D converter output. Low sampling frequencies of 17.78 kHz or even 12.31 kHz are possible using quadrature sampling in order to optimize memory requirements and to reduce the computational cost in signal processing. The distance is calculated from the TOF taking into account the speed of sound. An excellent accuracy in the estimation of the TOF is achieved using parabolic interpolation to detect of maximum of the signal envelope at the matched filter output. The signal phase information is also used for enhancing the TOF measurement accuracy. Experimental results show a root mean square error (rmse) less than 2 mm and a standard deviation less than 0.3 mm for pseudorange measurements in the range of distances between 2 and 6 m. The system location accuracy is also evaluated by applying multilateration. A sub-centimeter location accuracy is achieved with an average rmse of 9.6 mm.Junta de Andalucía P08-TIC-0388

RSSI Based Indoor Passive Localization for Intrusion Detection and Tracking

A real time system for intrusion detection and tracking based on wireless sensor network technology is designed by using the IITH mote which is de- veloped and designed in IIT Hyderabad as the communication module in the network.This paper describes the Device-Free Passive Localization system based on RSSI.The main objective of this paper is to design a DFP Local- ization system that is easily redeployable, recon�gurable, easy to use, and operates in real time. In addition the detection of humans is to be done.The em- bedded intrusion detection algorithm is designed so that it is able to cope with the limited resources, in terms of computational power and available memory space, of the microcontroller unit (MCU) found in the nodes. and various challenges and problem faced during the real test bed deployment and also proposed solutions to overcome them.We presented an alternative algo- rithm based on the minimum Euclidean distance classi�er.our result shows that the localization accuracy of this system is increased when using the proposed algorith

Diseño de un simulador para sistemas de localización acústicos subacuáticos basados en secuencias de espectro ensanchado

Las señales acústicas en entornos subacuáticos cada vez tienen más relevancia debido a la necesidad de localizar vehículos submarinos o redes de sensores en el fondo marino. Para desplegar cualquier sistema de posicionamiento, el primer paso es la realización de pruebas simuladas con objeto de conocer las necesidades y restricciones impuestas por el medio. Además, debido a la dificultad y al coste asociado a desplegar demostradores prácticos en entornos subacuáticos, resulta de especial utilidad disponer de modelos de simulación que permitan generar un amplio banco de pruebas, como paso previo a la realización de pruebas experimentales. La herramienta de simulación presentada en este trabajo permite el diseño de las señales emitidas por los transductores, la configuración de la emisión, la batimetría y los diferentes parámetros que caracterizan el entorno, así como la selección y ubicación del hidrófono receptor. Se utilizará un modelo de trazado de rayos para la simulación de la propagación de señales acústicas y se mostrarán los resultados en diferentes etapas del procesamiento: banda base, señal modulada, señal recibida y estimación de la posición.Acoustic signals for positioning systems in underwater environments have become particularly relevant, due to the need of locating underwater vehicles and sensor networks. To successfully deploy these positioning systems, a first common step is to carry out simulated studies to determine the requirements and restrictions imposed by the environment. Furthermore, since the underwater environment involves an additional difficulty and cost when deploying prototypes, it is particularly useful to have computer models available that allow the generation of a wide range of tests, as a previous step to the implementation of any experimental test. For that purpose, this work focuses on the design of a simulation tool for researchers in the field of acoustic localization systems. The proposed tool deals with key parameters and features, such as the generation of the signals emitted by the acoustic transducers (encoding techniques, modulations schemes, etc.), the frequency response and location of emitters and hydrophones, the bathymetry of the seabed, and the channel effects on the ultrasonic signal propagation. A ray tracing model has been applied to model the propagation of acoustic signals. The simulation tool has been successfully validated as a useful asset for this type of positioning systems, by means of a complete set of tests, considering different configurations and situations, and also analyzing the signals involved at different processing stages: baseband, modulated signals, received signals and final estimated positions.Máster Universitario en Ingeniería Industrial (M141

잔향 환경에서의 인공 음향 신호를 이용한 음향 센서 위치 추정 기술

학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 김남수.Widespread use of smart devices has brought a growth of user-customized services. In particular, localization techniques have been gaining attention due to increase of location-based services (LBS). Most of LBS services such as navigation systems, traffic alerts or augmented reality (AR) services depend on the GPS for its accuracy and speed, however, its operation is limited to the outdoor environments. The demand of indoor LBS is rapidly growing due to the growth of automated home and IoT technology. There have been studies via WiFi, Bluetooth or RFID, but their performance has been unsatisfactory for their limitation such as the requirement of additional equipment or guarantee of the line of sight. Among various sensors used for indoor localization, we focus on the acoustic sensors, i.e. microphones. There are several advantages in using the acoustic signals for indoor localization. There is no need for additional apparatus since loudspeakers are pre-installed in most of the buildings for the purpose of announcement or playing background music and mobile devices such as cellphones or tablets are equipped with microphones and loudspeakers. Even the prevailing popularity of IoT services helps accessibility of acoustical sensors and loudspeakers. In addition, acoustic signals have advantages of being able to detect signals through obstacles unlike cameras of RFID. In this thesis, we propose a position estimation system using acoustic signals to maximize these advantages. We aim to estimate the position of the target user with an acoustic sensor based on the recording of signals from the fixed loudspeakers installed around the room. We target to estimate the position of the acoustic sensor with high accuracy and low-complexity in a large space with high reverberation. Particularly, we try not to affect human hearing by using inaudible frequency bands. In order to estimate the position, it is important to estimate the direct path signal rather than the signal due to reverberation or reflection. To do this, we present various localization techniques as following. First, we propose the source data structure to operate in the large reverberant environments. In the large space, the consideration of the near-far effect is required which refers to a situation when the desired signal is far away, it is difficult to receive the desired signal due to the interference of closer unwanted signals. In wireless communications, it can be dealt with by interaction of transmitter and receiver by feedback of channel information. However, it is difficult in the acoustic system since there is no feedback between the transmitter and receiver. We borrowed the structure called OFDMA-CDM and modified it to deal with the near-far effect. In the reverberant environment, the amplitude of reverberation is often larger than the direct path signal. We proposed the technique to estimate the direct path signal. Second, we propose a method for accurate location estimation in the highly reverberant environments. In the high reverberation condition, more spurious reflections occur, which makes it difficult to estimate the time delay of the direct path signal. If the time delay estimation is wrong, it is likely that the position estimate does not converge by an estimation method. In the proposed method, position candidates are obtained from most of the received signals including signals even from spurious reflections. The unreliable candidates are filtered out by the agreement test and rank the rest candidates by their reliability to find accurate target position. We can estimate the receiver's position even in the condition of attenuated direct path signal or high reverberation by using the proposed method. Third, we proposed a low-complexity localization method to work in the highly reverberant environment. This method is based on the particle filter that estimates the position by weighted particles whose weights are computed by the likelihood. We designed likelihood function that efficiently calculates likelihood in the region with the direct path signal so that more reliable position can be obtained. The proposed method enables location estimation with high precision with a relatively small amount of computation in severe reverberation. The proposed methods are evaluated in simulated environments with different reverberation time. The performances are verified in different parameters and compared with other localization methods. In addition, the performance is evaluated in the real reverberant environment with a large space. A series of experiments has shown the superiority of the proposed methods and it is appropriate to apply in the actual environment.1 Introduction 1 2 Acoustic Receiver Localization System 7 2.1 Source data structure 8 2.2 Localization from the received signal 12 2.3 TDE in reverberant environments 16 2.4 Near-far effect 18 3 Indoor Localization using Inaudible Acoustic Signals 21 3.1 Introduction 21 3.2 Acoustic source design and synchronization 22 3.2.1 Reverberation in multipath environments 23 3.2.2 Source data structure for ARL 23 3.2.3 Signal presence detection 30 3.2.4 Direct path detection 30 3.3 Performance evaluation 32 3.3.1 Experimental setup and system configuration 33 3.3.2 Evaluation of acoustic data structure 34 3.3.3 Performance of the direct path detection algorithm 36 3.3.4 Performance in a real room 36 3.4 Summary 38 4 Robust Time Delay Estimation for Acoustic Indoor Localization in Reverberant Environments 39 4.1 Introduction 39 4.2 Robust TDE 40 4.3 Performance evaluation 45 4.3.1 Performance evaluation in a real room 46 4.3.2 Performance evaluation in simulated reverberant conditions 47 4.4 Summary 50 5 Indoor Localization Based on Particle Filtering 53 5.1 Introduction 53 5.2 A framework of positioning method using particle filter 54 5.2.1 State and dynamic models 55 5.2.2 Bayesian framework using particle filter 56 5.2.3 Likelihood function 57 5.3 ARL in reverberant environment 59 5.3.1 Peak quality 59 5.3.2 Efficient calculation of the likelihood function 60 5.3.3 Finding the direct path region 61 5.4 Performance evaluation 64 5.4.1 Performance in a simulated environment 65 5.4.2 Performance in the actual environment 87 5.5 Summary 89 6 Conclusions 91 Bibliography 95 요약 105Docto