Time Difference Of Arrival Scheme Research Articles

Time Difference of Arrival Based Indoor Positioning System Using Visible Light Communication

Visible Light Communication (VLC) is a novel optical wireless communication technology which uses Light Emitting Diodes (LEDs) and Photodiodes for coherent detection and very-high-data rate data communication system. The stringent Line of Sight (LoS) requirement in VLC makes it very suitable for Indoor Positioning System (IPS), to be used for autonomous and smart city infrastructure. The current work aims to implement a real time IPS system using VLC link in Network Simulator (NS-3). The VLC module is implemented by modelling real-time attributes of LEDs, optical channel, and the photodiodes. The localization is carried out using trilateration schemes which measures the Received Signal Strength Indication (RSSI) and the Time Difference of Arrival (TDoA) for position estimation of the target. The project is further extended to obtain a comparative analysis between VLC link and other existing technology, Wi-Fi, as far as positioning accuracy and other important performance metrics are concerned. The simulation results show significant improvement for the VLC link over the Wi-Fi link specially for the TDoA scheme accompanied by increasing number of beacon nodes.

Demonstration of a Low-Complexity Indoor Visible Light Positioning System Using an Enhanced TDOA Scheme

In this paper, a low-complexity time-difference-of-arrival (TDOA) based indoor visible light positioning (VLP) system using an enhanced practical localization scheme based on cross correlation is proposed and experimentally demonstrated. The proposed TDOA scheme offers two advantages: 1) the use of virtual local oscillator to replace the real local oscillator for cross correlation at the receiver side so as to reduce the hardware complexity; 2) the application of cubic spline interpolation on the correlation function to reduce the rigorous requirement on the sampling rate and to enhance the time-resolution of cross correlation. In order to achieve the high positioning accuracy with minimum implementation complexity, parameter optimization is first performed in terms of sampling rate, interpolation factor, and data length for correlation. Using the obtained optimal parameters, we demonstrate a low-complexity indoor two-dimensional VLP system using the correlation-based TDOA scheme in a coverage area of 1.2 $\times$ 1.2 m $^{2}$ with a height of 2 m. The experimental results validate the feasibility of the proposed TDOA scheme, and an average positioning accuracy of 9.2 cm is achieved with a sampling rate of 500 MSa/s, an interpolation factor of 100 and a data length of 250 k samples.

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.

Auto-localization system for indoor mobile robot using RFID fusion

SUMMARYAutonomous mobile robots need accurate localization techniques to perform assigned task. Radio Frequency Identification Technology (RFID) has become one of the main means to construct a real-time localization system. Localization techniques in RFID rely on accurate estimation of the read range between the reader and the tags. This paper proposes an auto-localization system for indoor mobile robot using passive RFID. The proposed system reads any three different RFID tags which have a known location. The current location can be estimated using the Time Difference of Arrival (TDOA) scheme. In order to improve the system accuracy, the proposed system fuses the TDOA scheme for the three tags. A Kalman filter is used to minimize the estimated error and predict the next location. The simulation results validate the proposed framework.