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Advances in Radio Localization Techniques
Published in Chao Gao, Guorong Zhao, Hassen Fourati, Cooperative Localization and Navigation, 2019
Cesar Vargas-Rosales, Rafaela Villalpando-Hernandez, Mort Naraghi-Pour
TDOA is another time-based method for localization which measures the difference in time between the signals arriving at two different receivers [13,24,26,63]. As such, this approach has several advantages over the TOA estimation method. Since it only measures the time difference at the anchor nodes, only the clocks between these receivers must be synchronized. In particular, it is not required that these clocks be synchronized with the clock at the target node. Clock synchronization among the anchor nodes is often easy to achieve since these nodes are part of a network infrastructure and may even be synchronized using a reference receiver. Moreover, since only signals at the receivers are compared, the transmitted signal from the target does not need to be time-stamped. These aspects make the TDOA-based localization more suitable in scenarios such as rescue missions, where the target mobile cannot synchronize its clock with the anchor receivers. As in the case of TOA, the anchors’ positions must be known. TDOA computation, however, requires more coordination among the anchor nodes. In particular, to compute the TDOA between two anchor nodes, their received signals must be available in the same location, requiring that at least one of the signals be transmitted again. Recently, a new approach to TDOA has been proposed which does not require clock synchronization among the anchors [100].
Acoustic Source Localization
Published in Kundu Tribikram, Mechanics of Elastic Waves and Ultrasonic Nondestructive Evaluation, 2019
With the plane wave front approximation, one can assume that the three sensors receive identical signal patterns near the first arrival and the signals are dispersed afterwards. TDOA is a time shift between two received signals which is computed by the cross-correlation technique, by plotting the product of two signals when for one signal the time shift is continuously changed. Two signals recorded by two sensors are displayed together in Figure 5.13a. Similar signals with a small time shift were found in the range between 1100 μs and 1500 μs. The time shift between them can be easily found by the cross-correlation technique. This method examines the similarity between the two given signals by computing [F(t)⋆G(t)](τ)=∫F(t)G(t+τ)dt
Positioning Algorithms and Systems
Published in Mohsen Kavehrad, Reza Aminikashani, Visible Light Communication Based Indoor Localization, 2019
Mohsen Kavehrad, Reza Aminikashani
To address these issues, hyperbolic lateration methods usually utilizing time-difference-of-arrival (TDOA) measurements are used. Different from TOA, TDOA-based systems measure the difference in time at which signals from different reference points arrive. These signals must be transmitted at the same time; therefore, all the transmitters as reference points have to be synchronized precisely. In VLC, this can be easily realized because light emitting diode (LED) bulbs are in close proximity. On the other hand, the receiver does not have to be synchronized with transmitters since it is not taking measurements of the absolute time of arrival. Moreover, no time stamp is required to be labeled in the transmitted signal.
UHF RFID Indoor Localization Based on Phase Difference
Published in IETE Journal of Research, 2023
Yanhan Zeng, Yuxing Liao, Xiheng Chen, Hong-zhou Tan
The types of indoor positioning algorithms can be divided into triangulation-based and pattern matching methods. The principle of the triangulation-based method is to calculate distance or angle directly by the measured information, which includes time of arrival (ToA), time difference of arrival (TDoA) [4–6], phase of arrival (PoA) and phase difference of arrival (PDoA) [7–10]. ToA requires accurate synchronization of all receivers and transmitters, while TDoA requires accurate time reference between receivers. The distance is estimated by the received signal strength indicator (RSSI) [11,12]. However, the accuracy of RSSI-based positioning method is limited due to the multipath, noise and antenna interaction. Besides, the problem of phase ambiguities will be encountered in the application of PoA. The complex indoor environments aggravate the above problems. Phase difference (PD) is used to eliminate the phase ambiguity [7], which is obtained by the antenna array in Reference [13]. As an improvement, a mobile antenna is used in Reference [14] to simulate antenna array. But these methods introduce additional mechanical equipment. In this paper, several groups of phases are obtained by setting reader’s different transmitting frequency, which is more feasible and affordable. To avoid the measurement error of distance or angle estimation, a method based on pattern matching is developed.
Use of real time localization systems (RTLS) in the automotive production and the prospects of 5G – A literature review
Published in Production & Manufacturing Research, 2022
Christoph Küpper, Janina Rösch, Herwig Winkler
Another method is the Time Difference of Arrival (TDOA). TDOA does not measure the time of the signal from the target to the base stations but the difference in time with which the signal arrives at two different base stations. Like TOA, the positions of the base stations must be known. In the plane case, three base stations and two-time differences are needed to determine the position (one more for the position in space). The position determination is shown in Figure 6. The base station that the signal reaches first becomes the reference base station. As soon as the signal reaches the second base station, a hyperbola can be formed based on the time difference. This hyperbola is the area in the plane where the difference between two fixed points is constant. The second time difference results in a second hyperbola that defines the target’s position at the intersection with the first . A significant advantage over TOA is that only the base stations must be synchronized. Not, however, the base station with the target object, since only the arrival times of the same package at the base stations are used for computation. Accordingly, the calculation is similar to TOA. However, since the time of the transmitter ts is not known, this variable is eliminated by subtracting equations (2) and (3): (Laoudias et al., 2018a; Tahat et al., 2016)
Incorporation of acoustic sensors in the regulation of a mobile robot
Published in Advanced Robotics, 2019
C. A. Luna-Aguilar, A. B. Morales-Díaz, M. Castelán, C. Nadeu
There are a number of methods used for spatial sound localization [12], which can be coarsely divided into three main groups: (1) Array beamforming based methods, in particular the Steered Response Power (SRP) approach, which relies on the power of the signal received when the microphone array steers each target location [13]. (2) Methods based on high spectral resolution [14], which use the spectral decomposition of the covariance matrices, like the Multiple Signal Classification (MUSIC) algorithm; they can work with several sound sources but are considered less robust against reverberation than beamforming based methods. And (3) Time Delay of Arrival (TDOA) methods, which work with the estimated time delays between signals captured by two spatially separated (a pair of) microphones; the time delays are combined with the coordinates of the microphones to estimate the source location. Time delays are often obtained from the Generalized Cross-Correlation (GCC) [15], employing the Phase Transform (PHAT) [11]. PHAT filtering is also used in combination with SRP (SRP-PHAT). The last technique is widely used because of its robustness [9], provided that the number of microphones is high enough. That is not the case in our application, so we will use the TDOA approach, which has the additional advantage of requiring a low computational load.