Richa Bharadwaj

Experimental Investigation of 3-D Human Body Localization Using Wearable Ultra-Wideband Antennas

This paper presents experimental investigations and analysis of ultra-wideband localization of body-worn antennas in an indoor environment. Three-dimensional (3-D) tracking of wearable antennas placed on the upper human body is achieved using a compact and cost-effective antenna and time of arrival (TOA) localization techniques. Various features such as rms delay spread, kurtosis, and signal amplitude have been used to classify the channel type between each antenna location and base station. Non-line-of-sight identification and mitigation techniques have been used to enhance the accuracy of the localization technique applied. Geometric dilution of precision of the base-station configuration and numerical analysis on the radiation patterns for different locations of the body-worn antenna has been studied in terms of variation in localization accuracy. High-accuracy 3-D localization results in the range of 1-2 cm are obtained with the antennas placed on the limbs and 1-3 cm for the torso region. The accuracy achieved is 3 times better than commercially available UWB localization and tracking systems. The significantly high-accuracy results obtained for all antenna locations demonstrate the reliability and suitability of UWB technology for various indoor tracking and localization applications in the fields of healthcare, sports, and well-being.

Localization of Wearable Ultrawideband Antennas for Motion Capture Applications

This letter presents a study of human body localization using ultrawideband (UWB) technology. Various base-station configurations, time of arrival, and first peak detection algorithms are used to estimate the position of the body-worn antennas. Localization error as small as 1-2 cm has been achieved using eight base stations, which is comparable to the measurement accuracy obtained by a complex optical motion capture system to determine the absolute displacement error. The localization error obtained is better by a third in comparison to common commercial system based on UWB technology. The results demonstrate that cuboid-shape configuration with four base stations gives slightly low average percentage error (2%-3%) in comparison to Y-shape (4%). However, the Y-shape configuration is more compact and provides setting-up simplicity, which makes it convenient for various applications ranging from healthcare monitoring to entertainment technologies either laboratory-based or in-home.

Analytical and Experimental Investigations on Ultrawideband Pulse Width and Shape Effect on the Accuracy of 3-D Localization

This letter presents analytical and experimental investigation of three-dimensional indoor localization accuracy using different subbands of the Ultrawideband (UWB) spectrum. Combined effect of ranging errors of each base station (due to change in pulse width, bandwidth, and UWB source pulse) on 3-D localization using a compact tapered slot antenna is studied. Higher-order Gaussian derivative source pulses (3rd and 7th) are compared to first-order Gaussian derivative theoretically and analyzed in terms of the fidelity of the UWB source pulses; localization accuracy and Cramér-Rao lower bounds have also been calculated to validate the experimental findings. It is observed that 5-GHz bandwidth gives sufficiently high localization accuracy results with an average error of 2-3 cm. Results related to the different UWB source pulse show that the third-order Gaussian derivative signal can be used to enhance (30% increase) the localization accuracy and also preserve a good tradeoff between accuracy and complexity of the UWB system.

Ultrawideband-Based 3-D Localization Using Compact Base-Station Configurations

This letter presents theoretical and experimental investigations and analysis on three-dimensional ultrawideband (UWB) localization using compact base-station configurations. A comparative study is performed between the three proposed configurations (Y-shape, L-shape, and mirror-based) and the commonly used cuboid-shape configuration in terms of accuracy and compactness. Results show that the average localization accuracy of the Y- and L-shape configurations is in the range of 3-5 cm, whereas the cuboid- and mirror-based configurations give an accuracy of around 2-5 cm. The Geometric Dilution of Precision (GDOP) values have been calculated for all configurations, which shows a high level of accuracy (i.e., precision values are in the range of 2-4). In addition, a tradeoff regarding occupancy area and complexity is taken into account, and the results show that the proposed configurations have the advantage of compactness as compared to the cuboid configuration and also provide high accuracy in centimeter range, hence making it suitable for various applications such as motion capture in healthcare systems and entertainment.

Impulse Radio Ultra-Wideband Communications for Localization and Tracking of Human Body and Limbs Movement for Healthcare Applications

Accurate and precise motion tracking of limbs and human subjects has technological importance in various healthcare applications. The use of impulse radio-ultra wideband technology (IR-UWB) technology due its inherent properties is of recent interest for high-accuracy localization. This paper presents experimental investigations and analysis of indoor human body localization and tracking of limb movements in 3-D based on IR-UWB technology using compact and cost-effective body-worn antennas. The body-centric wireless channel characterization has been analyzed in detail using parameters such as path loss magnitude, number of multipath components, rms delay spread, signal amplitude, and Kurtosis with the main focus to differentiate between line-of-sight (LOS) and non-LOS situations. Fidelity of the received signal is also calculated for different activities and antenna positions to study the pulse preserving nature of the UWB antenna, when it is placed on the human body. The results reported in this paper have high localization accuracy with 90% in the range from 0.5 to 2.5 cm using simple and cost-effective techniques which is comparable to the results obtained by the standard optical motion capture system.

Experimental investigation of efficient Ultra Wideband localisation techniques in the indoor environment

This paper presents experimental work on Ultra Wideband indoor positioning in presence of different objects using a compact UWB antenna using time of arrival positioning techniques. Obstacles considered are wooden table, laboratory chair and a solid wooden object. Different objects affect the accuracy in positioning depending upon the shape, size, and material of the objects. Results show that the error is similar in the presence of laboratory chair and wooden object though the material type is different. This is attributed to the fact that the propagation between Base Stations and Mobile Stations are affected due to height of objects and position of the Base Stations which leads to reflections/ multipath. Maximum error of 5 to 6 cm in localisation is achieved in presence of a wooden block which is due to the fact of having height more than the Base Stations and Mobile Station bringing them in non line of sight situation. Minimum error obtained is 1 to 3 cm when no object is present in the area where localisation is taking place.

Ultra wideband sub-band time of arrival estimation for location detection

This paper presents experimental and theoretical characterisation of time of arrival and distance for accurate location detection using different subbands of Ultra Wideband (UWB) radio technology. The error in the measured distance is computed between the geometrically calculated distance (taken as a reference) and the estimated distance using channel impulse response technique. Three different types of compact antennas are used in this study. Studies on different sub bands across whole UWB band shows that the average percentage error in estimation of distance improves by a factor of two, when higher bandwidth (7 GHz) is used compared to lower bandwidth (2 GHz) of the UWB frequency range. Results show that the percentage error of estimation for Time of Arrival is directly proportional to the pulse width.

Study and analysis of ultra wideband through glass propagation channel characteristics

This paper presents an experimental investigation of ultra-wideband (UWB) radio propagation through glass in the (3–8 GHz) frequency range using compact and cost-effective planar microstrip antennas. Channel parameters such as path loss magnitude, rms delay spread, received signal amplitude and multipath have been analyzed from the measured data. Results and analyses highlight the variation of the channel parameters when the glass is rotated at different angles ranging from 0 to 90 degrees mimicking the movement of a door or window present in an indoor environment. Measurement data is also used in predicting different LOS, partial NLOS and NLOS situations which are dependent on the rotation angle of the glass sheet and also the position of the Tx-Rx antennas. Results indicate higher multipath and rms delay spread for edge scattering in comparison to direct through glass propagation. Path loss magnitude varies by 2 to 4 dB for NLOS scenarios in comparison to LOS scenarios. RMS delay spread values increase by 3 to 5 nsec for NLOS scenarios and multipath components by 10 to 15. The study gives an overview on the indoor propagation characteristics of the channel in the presence of glass sheet which acts like an obstacle causing variation in the channel link.

Numerical analysis of ultra-wideband propagation for body-centric communication

This paper presents a study on body centric propagation based on ultra wideband technology using a compact and cost effective wearable antenna through simulations and validated by indoor environment measurements. The body worn antenna is placed on the human body model and different scenarios are considered such as off-body, body-to-body communication with and without the presence of partition made of concrete that will lead to variation in the propagation phenomenon. Fidelity factor results related to the received pulse shows that in the presence of the wall partition and human body, the average fidelity decreases by 4–5 % in comparison to no-obstacle scenario having high fidelity (0.97–0.99). Average fidelity in the presence of human body only is 0.96, thus leading to a reliable communication link in all scenarios.

Motion tracking of a human subject in healthcare applications using compact ultra wideband antennas

This paper presents a study of 3D localisation of compact body-worn sensors using Ultra Wideband technology. Nine different sensor locations on the upper body of the human subject are considered. 3D localisation of the body worn sensors is achieved using time of arrival and peak detection techniques. The average 3D positioning accuracy achieved is in the range of 1 to 3 cm which are comparable with the complex optical motion capture system that is used as reference. Results also show that accuracy in estimation of location of the sensor depends on the position it is placed on the human body, configuration of the base station and the propagation phenomenon in the indoor environment in which localisation is taking place. The high cm accuracy obtained makes UWB technology suitable for various indoor applications in field of healthcare, sports, industry and day to day life.