Guowei Shen

Performance comparison of TOA and TDOA based location estimation algorithms in LOS environment

In this paper, various positioning algorithms for range-based TOA and TDOA localization have been analyzed, which include the analytical method, least square method, approximate maximum likelihood method, Taylor series method, two-stage maximum likelihood method and genetic algorithm. The assumed scenario is an overdetermined system in a 3D space under line of sight (LOS) situation and a number of sensor nodes placed arbitrarily across this area. The performance of the algorithms has been compared in the assumed scenario. Both the average error and the failure rate have been investigated in terms of the number of reference nodes and the root mean squared error (RMSE) of the range estimation.

Range-based localization for UWB sensor networks in realistic environments

The Non-Line of Sight (NLOS) problem is the major drawback for accurate localization within Ultra-Wideband (UWB) sensor networks. In this article, a comprehensive overview of the existing methods for localization in distributed UWB sensor networks under NLOS conditions is given and a new method is proposed. This method handles the NLOS problem by an NLOS node identification and mitigation approach through hypothesis test. It determines the NLOS nodes by comparing the mean square error of the range estimates with the variance of the estimated LOS ranges and handles the situation where less than three Line of Sight (LOS) nodes are available by using the statistics of an arrangement of circular traces. The performance of the proposed method has been compared with some other methods by means of computer simulation in a 2D area.

Time of arrival estimation for range-based localization in UWB sensor networks

Accurate Localization has gained significant interest within sensor networks recently and positioning systems based on Ultra-Wideband (UWB) technology have been considered, because the UWB signals have a very good accuracy due to the high time resolution (large bandwidth). Time of Arrival (TOA) estimation of the first path is usually used for range-based localization in realistic environments within UWB sensor networks, which can be challenging in dense multipath environments. In this paper, TOA algorithms for range-based localization in UWB sensor networks are analyzed and two new TOA estimation methods are proposed. One is the constant false alarm rate (CFAR) method, which is based on the CFAR detection theory in Radar systems. The other one is the maximum probability of detection (MPD) method, which determines the TOA estimation according to a comparison of the detection probabilities of a number of different possible TOA estimations. The performance of the proposed methods is evaluated and compared with several existing methods by computer simulation using realizations of IEEE802.15.4a channel models.

Ultra-Wideband MIMO Ambiguity Function and Its Factorability

Ambiguity function (AF) provides an effective way for analysis of the resolving performance of a radar system. With the development of ultra-wideband (UWB) and multiple-input-multiple-output (MIMO) radio techniques, recently, the combination of them-the concept of UWB MIMO radar has been proposed and received much attention. For a UWB MIMO radar, first, the signal waveform with an exponential expression which is widely adopted in narrowband cases is not appropriate anymore. Second, the MIMO radar sensors are typically organized in a certain spatial topology, which greatly impacts the performance of the MIMO system. In addition, for a typical MIMO radar application scenario, generally, there are relative motions existing between the radar sensors and the targets. The presence of the relative motions would further complicate the performance analysis of the system. In fact, for a MIMO radar, the overall performance of the system is jointly determined by the parameters, such as the signal waveform, the topology, and the relative motions. Each of the parameters impacts the resolving performance in a particular way. In order to evaluate the contribution of each individual parameter of interest, in this paper, a UWB MIMO AF is developed and factorized into several factors. By this means, each individual parameter can be evaluated via the corresponding factor to examine a certain specific characteristic of the system, instead of via the complicated whole MIMO AFs.

Evaluation of requirements for UWB localization systems in home-entertainment applications

This paper discusses basic requirements for passive ultra-wideband (UWB) localization systems that aim at home-entertainment applications such as smart audio systems, which can adapt the sound according to the user location, providing an optimum listening experience to the user. We have analyzed over hundred thousand channel impulse responses measured by a real-time UWB channel sounder in different scenarios. Our analyses show that passive localization systems must possess a large real-time dynamic range in order to be capable of detecting a listener. We assume that the listener does not carry any tag and is detected and localized just by electro-magnetic (EM) waves reflected from his body. Such passive localization is demonstrated by a measurement example.

Cooperative Localization and Object Recognition in Autonomous UWB Sensor Networks

Ultra-wideband (UWB) radio sensor networks promise interesting perspectives for emitter and object position localization, object identification and imaging of environments in short range scenarios. Their fundamental advantage comes from the huge bandwidth which could be up to several GHz depending on the national regulation rules. Consequently, UWB technology allows unprecedented spatial resolution in the geo-localization of active UWB radio devices and high resolution in the detection, localization and tracking of passive objects.

Ultrawideband Channel Sounding within an Airbus 319

Ultra-wideband (UWB) techniques are recently targeted as a broadband short range solution for in-flight-entertainment (IFE) systems. Despite the in-cabin channel can be considered as an indoor channel, under the current aviation regulations, and due to the usual metal cabins and cylindrical shapes, these scenarios are particular for wireless applications. In this paper is presented an experimental characterization of the UWB channel within an Airbus 319 aircraft cabin based on a real-time multiple-input-multiple-output (MIMO) UWB channel sounder. Here, the delay spread and coherent bandwidth have been calculated for different antennas configurations and distances. Besides, the in-cabin path-loss exponent has been calculated based on an extensively amount of data. Moreover, dynamic range metrics have been introduced for channel analysis and performance comparisons along the cabin.

UWB localization of active nodes in realistic indoor environments

Localization in distributed Ultra-Wideband sensor networks is an important area that attracts significant research interest. In this paper, main sources of errors in a realistic indoor environment of range-based localization are analyzed and a novel UWB localization approach is proposed which considers ranging, location estimation, NLOS identification and tracking. The performance of it is evaluated by computer simulation in an assumed indoor scenario with different LOS/NLOS situations.

Stationary symmetric object detection in unknown indoor environments

It is difficult to detect a stationary object in practice, especially in an unknown indoor environment, because t (a) there is no distinct speed difference between the targets and the background; (b) responses of the targets are contaminated by the dense unknown clutter; (c) a priori knowledge of the background is not always available. In the paper, a scheme is designed to enhance the signal by a “time-shift & accumulation” operation. Meanwhile, clutters from different sources are non-uniformly time-shifted. As a consequence, the Signal-to-Clutter Ratio (SCR) is increased. The distribution of the accumulation of clutter and noise from different sources would approach Gaussian according to the Central Limit Theorem (CLT). Then the problem of target detection in an unknown environment becomes target detection under Gaussian clutter and noise. Since the targets concerned are symmetric objects, the signals from the symmetrically placed receiver pairs are examined. In addition, results from measurement in a realistic indoor environment are provided.

A UWB active sensor localization method based on time-difference back-projection

Time of arrival (TOA) based techniques are widely used in many ranging and localization problems. But because their performance highly depends on the accuracy of the TOA estimation of direct-paths, its challenging to achieve accurate position estimations under dense multipath or Non-Line-of-Sight (NLOS) condition. In this paper, an algorithm which combines Time difference of arrival (TDOA) technique and back-projection technique is proposed. Based on a coarse estimate of the direct-path, a certain data segment containing direct-path is extracted from each channel. Then a back-projection operation is applied on the extracted data segments so as to strengthen the information of direct-path. A final position estimate is obtained at the same time.