First Path Research Articles

Double sliding window variance detection-based time-of-arrival estimation in ultra-wideband ranging systems

<span lang="EN-US">Ultra-wideband (UWB) ranging via time-of-arrival (TOA) estimation method has gained a lot of research interests because it can take full advantage of UWB capabilities. Energy detection (ED) based TOA estimation technique is widely used in the area due to its low cost, low complexity and ease of implementation. However, many factors affect the ranging performance of the ED-based methods, especially, non-line-of-sight (NLOS) condition and the integration interval. In this context, a new TOA estimation method is developed in this paper. Firstly, the received signal is denoised using a five-level wavelet decomposition, next, a double sliding window algorithm is applied to detect the change in the variance information of the received signal, the first path (FP) TOA is then calculated according to the first variance sharp increase. The simulation results using the CM1 and CM2 IEEE 802.15.4a channel models, prove that our proposed approach works effectively compared with the conventional ED-based methods.</span>

A novel singular value decomposition-based ultra wide band time-of-arrival estimation for multiple targets

It is widely <span>admitted that the estimation of ultra wide band (UWB) time-of-arrival (TOA) for multiple targets in indoor multipath channels is a very challenging task. The existing algorithms deal with a limited number of targets and require a complex exchange of several messages. In this paper, a novel TOA estimation algorithm for multiple targets is developed. The proposed algorithm estimates the first path (FP) TOA of a number of targets without exchanging messages or using collision avoidance techniques. As a first step, the singular value decomposition (SVD) is employed to extract the first path (FP) of each target and then a matched filter, followed by an iterative threshold crossing algorithm, is used to determine the number of targets and the corresponding FP TOAs. The simulation results with four targets, using the CM1 IEEE 802.15.4a channel model, showed that the proposed novel algorithm can effectively detect the FP of each target and estimate its corresponding TOA.</span>

UWB pulse detection and TOA estimation using GLRT

In this paper, a novel statistical approach is presented for time-of-arrival (TOA) estimation based on first path (FP) pulse detection using a sub-Nyquist sampling ultra-wide band (UWB) receiver. The TOA measurement accuracy, which cannot be improved by averaging of the received signal, can be enhanced by the statistical processing of a number of TOA measurements. The TOA statistics are modeled and analyzed for a UWB receiver using threshold crossing detection of a pulse signal with noise. The detection and estimation scheme based on the Generalized Likelihood Ratio Test (GLRT) detector, which captures the full statistical information of the measurement data, is shown to achieve accurate TOA estimation and allows for a trade-off between the threshold level, the noise level, the amplitude and the arrival time of the first path pulse, and the accuracy of the obtained final TOA.

Entropy-Based TOA Estimation and SVM-Based Ranging Error Mitigation in UWB Ranging Systems.

The major challenges for Ultra-wide Band (UWB) indoor ranging systems are the dense multipath and non-line-of-sight (NLOS) problems of the indoor environment. To precisely estimate the time of arrival (TOA) of the first path (FP) in such a poor environment, a novel approach of entropy-based TOA estimation and support vector machine (SVM) regression-based ranging error mitigation is proposed in this paper. The proposed method can estimate the TOA precisely by measuring the randomness of the received signals and mitigate the ranging error without the recognition of the channel conditions. The entropy is used to measure the randomness of the received signals and the FP can be determined by the decision of the sample which is followed by a great entropy decrease. The SVM regression is employed to perform the ranging-error mitigation by the modeling of the regressor between the characteristics of received signals and the ranging error. The presented numerical simulation results show that the proposed approach achieves significant performance improvements in the CM1 to CM4 channels of the IEEE 802.15.4a standard, as compared to conventional approaches.

Application of power transformation and moments in time based UWB ranging

For ultra-wideband (UWB) ranging, TOA estimation with the energy detection (ED) receiver is to detect the energy sample that contains the first path (FP) signal in dense multipath. Threshold crossing (TC) is used frequently. However, it is difficult to determine the threshold. Some threshold setting methods are based on constant false alarm rate (CFAR) and the chi-squared distribution. However, the distribution is complicated. Moreover, it depends on the degree of freedom (DOF). If the DOF used is wrong, it will degrade the detection performance. The study bypasses the distribution. We first examine the distribution of the output of the ED receiver after power transformation. Based on the new characteristics of the transformed data and approximate distributions, we propose some practical TOA estimation methods. Similarly, the moments of the output of the ED receiver, such as the second or one-third order moments, are also analysed and used. The proposed methods are easy to implement and can achieve about the same ranging performance with methods based on the chi-squared distribution. We provide both theoretical and simulation results to prove their effectiveness.

First Path Detection Using Rank Test in IR UWB Ranging with Energy Detection Receiver under Harsh Environments

To estimate time of arrival (TOA) in impulse radio (IR) ultra wideband (UWB) ranging under harsh environments, the rank test is adopted in the study to detect the first path (FP) in dense multipath with energy detection (ED) receiver. Most TOA estimation methods work well in the additive white Gaussian noise (AWGN). Actually, the background noise could be non-Gaussian. Moreover, the received signal could be polluted by outliers. In these cases, traditional threshold based methods perform badly, as there may be extraordinary large samples in the output of the receiver. These samples will interfere with the detection of the sample containing the FP. A novel and practical method based on the rank test is proposed to deal with these problems. The FP detection is based on the ranks of the received data samples instead of the samples. Simulations are carried out to demonstrate its effectiveness in the IEEE 802.15.4a channels.

TOA Estimation in IR UWB Ranging with Energy Detection Receiver Using Received Signal Characteristics

The energy detection (ED) receiver is a feasible solution for time of arrival (TOA) estimation in ultra wideband (UWB) ranging. The task of TOA estimation under UWB multipath channel is to determine the first path (FP). In the ED receiver, threshold-crossing (TC) is used a lot. However, the threshold should be elaborately chosen, or else the false detection probability will be high. But it is difficult to acquire the optimal threshold. In the study, we propose a novel method to estimate the TOA based on the received signal characteristics, which are that the TOA of the noise sample that exceeds the threshold is random while the TOA of the FP is definite. The method detects the FP by calculating the frequencies of different samples crossing the thresholds over a sequence of received pulses. Simulation results verify its effectiveness in the IEEE 802.15.4a channels. Comparison results with other methods are also presented to prove the superiority of our method.