In time-of-arrival (TOA) based indoor human tracking system, the human body mounted with the target sensor can cause non-line of sight (NLOS) scenario and result in significant ranging error. However, the previous studies on the behavior of indoor TOA ranging did not take the effects of human body into account. In this paper, measurement of TOA ranging error has been conducted in a typical indoor environment and sources of inaccuracy in TOA-based indoor localization have been analyzed. To quantitatively describe the TOA ranging error caused by human body, we introduce a statistical TOA ranging error model for body mounted sensors based on the measurement results. This model separates the ranging error into multipath error and NLOS error caused by the creeping wave phenomenon. Both multipath error and NLOS error are modeled as a Gaussian variable. The distribution of multipath error is only relative to the bandwidth of the system while the distribution of NLOS error is relative to the angle between human facing direction and the direction of transmitter–receiver, signal to noise ratio and bandwidth of the system, which clearly shows the effects of human body on TOA ranging.

Modeling the Effect of Human Body on TOA Based Indoor Human Tracking

For time-of-arrival-(TOA)-based indoor human tracking system, the wireless channel between human body surface and external reference node can be regarded as the source of inaccuracy. Since only the arrival time of direct path provides accurate range estimate, the nonline of sight caused by human body leads to undetectable direct path condition and thus results in a significant distance measurement error. In this paper, we measured TOA ranging error for indoor human tracking applications inside a typical office environment. A large number of TOA ranging samples was obtained and statistically analyzed. The TOA ranging error was modeled as a Gaussian random variable with the parameters, including position of target sensor, angle between human facing direction, and direction of transmitter–receiver, signal-to-noise ratio, and bandwidth of the system. As a validation of proposed model, excellent agreement has been found between empirical measurement and model-based software simulation.

Toward Accurate Human Tracking: Modeling Time-of-Arrival for Wireless Wearable Sensors in Multipath Environment

Precision ultra-wideband ranging requires accurate estimation of time of arrival (TOA). The threshold-based TOA estimation has attracted considerable interest due to its simplicity. In this paper, we propose a technique to set the threshold as a function of delay instead of a single value as in conventional methods. Simulation results show that the proposed method is superior to conventional methods.

Delay-Dependent Threshold Selection for UWB TOA Estimation

Autonomy of vehicles is a widely discussed topic, increasing the need for low power, inexpensive and precise localization and navigation. Due to ongoing research and standardization in last decades, ultra-wideband (UWB) based localization technology is more and more ready for large scale usage. In this paper we propose an embedded UWB localization system, consisting of an inexpensive, low power hardware platform deploying an IEEE 802.15.4a-2011 UWB-PHY standard conform RF chip, enabling communication and localization, a software framework, and localization algorithms. The key contribution of the paper is this system concept and experimental results using a developed system in an underground parking garage. Within this system evaluation we show in an accuracy analysis an achievable positioning error of around 30 cm. Furthermore we show the useage of such an UBW localization system in an use case near scenario.

Design of an embedded UWB hardware platform for navigation in GPS denied environments

The location of people, mobile terminals and equipment is highly desirable for operational enhancements in the mining industry. In an indoor environment such as a mine, the multipath caused by reflection, diffraction and diffusion on the rough sidewall surfaces are the main sources of range measurement errors. In this paper, a UWB time of flight based localization system is proposed to address the multipath effect in underground mines. To reduce the communication cost and time delay of localization in such a chain type wireless network, a distributed localization algorithm based on particle swarm optimization (PSO) is proposed and implemented on the blind node (the node to be localized). Without extra hardware needed, an accurate but low cost localization system has been achieved. Experimental results verify the proposed scheme

A Distributed UWB-based Localization System in Underground Mines

This paper sums up the approach of designing and fabrication of the flight controller for unmanned aerial vehicles. There are many existing flight controller designs which use a wide range of components. However, in order to understand the functioning of the flight controller in detail and to have a practical approach towards the same, we have designed a flight controller and have realized it into a 3D CAD model. This paper covers the selection of components, approach taken to initiate design process, theoretical analysis of performance of the components and visualization of 3D CAD model of the flight controller.

Design and Fabrication of a Flight Controller for Unmanned Aerial Vehicles

Prior to transmission, the best receiver position for optimum signal reception from the transmitter is preferred Unfortunately due to multipath, finding the best receiver position and identifying the channels in indoor environment are very difficult This paper proposes a low complexity parameter to overcome this problem Also, advantage is taken of the UWB (Ultra-Wide Band) physical layer, which has multipath resolution capacity Simulation and measurement results are compared and shown as proof of concept that precise channel profiles between different LOS and NLOS conditions can be identified with this combined strategy Also UWB communication system is realized by modelling UWB signal as Hermite pulses and convolving them with the IEEE 802153a channel models for LOS and different NLOS conditions, namely CM1, CM2, CM3 and CM4, using modified Saleh-Valenzuela (S-V) model

Gerardine Immaculate Mary

Papers

Design and Fabrication of a Flight Controller for Unmanned Aerial Vehicles

UWB indoor channel profile identification with orthogonal Hermite pulses