Ultra-wideband Technique Research Articles

Joint Direction-of-Arrival and Time-of-Arrival Estimation With Ultra-Wideband Elliptical Arrays

This paper presents a general technique for the joint Direction-of-Arrival (DoA) and Time-of-Arrival (ToA) estimation in multipath environments. The proposed ultra-wideband technique is based on phase-mode expansions and the use of nearly frequency-invariant elliptical arrays. New possibilities open with the present approach, as not only elliptical, but also circular and linear (highly flattened) arrays can be considered with the same implementation. Systematic selection/rejection of signals-of-interest/signals-not-of-interest in smart wireless environments is possible, unlike with previous approaches based on circular arrays. Concentric elliptical arrays of many sizes and eccentricities can be jointly considered, with the subsequent improvement that entails in DoA and ToA detection. This leads to the realization of pseudo-random array patterns; namely, quasi-arbitrary geometries created from the superposition of multiple elliptical arrays. Some simulation and experimental tests (measurements in an anechoic chamber) are carried out for several frequency bands to check the correct performance of the method. The method is proven to give accurate estimations in all tested scenarios, and to be robust against noise and position uncertainty in sensor placement.

Overview of ultra-wideband transceivers—system architectures and applications

The Ultra-WideBand (UWB) technique, which offers good energy efficiency, flexible data rate, and high ranging accuracy, has recently been recognized as a revived wireless technology for short distance communication. This paper presents a brief overview of two UWB techniques, covering Impulse-Radio UWB (IR-UWB) and Frequency-Modulation UWB (FM-UWB) methods. The link margin enhancement technique, Very-WideBand (VWB), and power consumption reducing technique, chirp UWB, are also introduced. Then, several potential applications of IR-UWB with transceiver architectures are addressed, including high data rate proximity communication and secure wireless connectivity. With fine-ranging and energy-efficient communication features, the UWB wireless technology is highly promising for secure mobile Internet of Things (IoT) applications.

Multistatic UWB Radar-Based Passive Human Tracking Using COTS Devices

Due to its high delay resolution, the ultra-wideband (UWB) technique has been widely adopted for fine-grained indoor localization. Instead of active positioning, UWB radar-based passive human tracking is explored using commercial off-the-shelf (COTS) devices. To extract the time-of-flight (ToF) reflected by the moving person, the accumulated channel impulse responses (CIR) and the corresponding variances are used to train the convolutional neural networks (CNN) model. Particle filter algorithm is adopted to track the moving person based on the extracted ToFs of all pairs of links. Experimental results show that the proposed CIR- and variance-based CNN models achieve less than 30-cm root-mean-square errors (RMSEs). Especially, the variance-based CNN model is robust to the scenario changing and promising for practical applications.

Energy Efficient Approach in Wireless Sensor Network for Surveillance: A Review Analysis

Over recent years there is a huge growth in the area of wireless networks due to its efficient design. The word sensor is defined as component which handles & monitor different kinds of inputs from different sources such as physical and environmental conditions like pressure, heat, light, sound and vibrations etc. The output produced by the sensor will be electrical in nature and this electrical signal is further applied to various controllers for other functions. A Wireless Sensor Network is basically a form of ad-hoc network which consists of thousands of tiny sensor nodes. These wireless networks are deployed where the wired network implementation is difficult or impossible. These nodes are further distributed over a wide area such as hilly areas, forests, deserts, ocean etc. and these tiny sensors communicate or exchange data with each other by using radio signals. The WSN utilizes various communication protocols like Bluetooth, Wi-Fi, Zigbee and Ultra Wide Band techniques. Every protocol has its own speed and depending upon the distance between them, there are various problems which network can face like battery failure, effective coverage area, and effective energy utilization or node failure. In this paper, the several different methods to build energy efficient network, methods to improve the lifetime of a network, method for detection and correction of node failure and in the last the important applications are discussed.

Indoor Localization With Reconfigurable Intelligent Surface

Recently, reconfigurable intelligent surface (RIS), which operates with the aim to manipulate multi-path signals, has been widely considered for wireless communications. In this letter, we extend the employment of RIS to indoor positioning, with the aid of ultra-wideband (UWB) technique. Moreover, the Cramér-Rao lower bound of the developed positioning scheme is quantified. Both theoretical analysis and simulation results demonstrate that RIS has the potential to realize accurate positioning with a single access point, due to its ability to mark the channel and replace traditional active positioning anchors. Moreover, it is also depicted that when the number of receive antennas is limited, time-of-arrival based positioning has a higher accuracy than that based on angle-of-arrival, due to the high multipath resolution of UWB signals.

An Efficient Indoor Target Tracking Algorithm Using TDOA Measurements With Applications to Ultra-Wideband Systems

The ultra-wideband technique has shown its effectiveness for indoor target tracking. Various types of measurements have been applied to ultra-wideband systems for indoor target tracking, and the time difference of arrival (TDOA) measurement-based approaches are the most widely used methods due to their good accuracy and feasibility. Target tracking with the TDOA measurements usually encounters the problem of correlated measurement noises, as one sensor network utilizes the common reference sensor for measurement generation. The off-diagonal entries in the measurement error covariance matrix become non-zero values, which makes the standard target tracking algorithms inconvenient for practical installation of an ultra-wideband system. Another problem in sensor networks is properly exploiting the measurements obtained from multiple sensors considering practical conditions, such as storage limitations or computational resource consumption. The parallel update and the serial update are usually applied for the multi-sensor tracking problem. This paper presents a target tracking algorithm that integrates the Cholesky decomposition to decorrelate the measurement noises for the serial update, thus improving computational efficiency. The proposed algorithm is realized in an ultra-wideband system for real-time target tracking, and an experiment using real data is conducted to validate its practicability.

Localization of Indoor Mobile Robot Using Minimum Variance Unbiased FIR Filter

The demand of indoor localization has recently grown quickly in industries. In general, a localization system is required to be reliable, fast, and have high accuracy. In this paper, the ultrawideband (UWB) technique is combined with the inertial navigation sensor (INS) to form a coupled UWB/INS localization framework, which inherits the advantages from both components. A minimum variance unbiased finite impulse response (MVU FIR) method is then applied to obtain accurate position and velocity estimations from noisy measurements. Two experiments and several simulations are conducted. Compared with the traditional Kalman filter (KF) and particle filter, the MVU FIR filter exhibits better immunity to the errors about a priori knowledge of noise variances. It can handle the kidnapped problem, and recover from some extreme failures satisfactorily. Moreover, the MVU FIR filtering algorithm is fast and easily implementable. Its online computational time is even lower than that of the KF, which is favorable in localization applications. Note to Practitioners —For indoor robot localization, an effective filtering algorithm can improve the accuracy significantly. Existing and commonly used filtering approaches suffer from weak robustness to the imprecise a priori knowledge of noise variances used, unsatisfied performance when dealing with sudden behaviors of robot, and large online computational load. This paper suggests a new practical method to estimate the current state using finite past measurements with a finite impulse response filter gain computed off-line. By testing it within the coupled ultrawideband/inertial navigation sensor localization framework under different operating conditions, we demonstrate that the proposed method can effectively overcome the above problems, providing fast, accurate, and reliable estimation in a practical environment.

Measurement of the Reflectivity of Radiation Absorbent Materials by Pulsed Spectroscopy

Results from an experimental study of the reflectivity of radiation adsorbent materials probed by ultrashort electromagnetic radiation are presented. Ultra wide-band pulsed microwave spectroscopic methods are used. Measurements of reflectivity by traditional narrow band and ultra-wide band techniques are compared.

A high-accuracy indoor positioning system based on UWB

In this paper, a high-accuracy indoor positioning system based on the ultra-wideband (UWB) technique is proposed. The proposed system uses a simple ranging process to obtain the distance between the mobile node and the fixed base stations. Besides, an improved time of arrival (ToA) algorithm with Kalman filtering is proposed to improve the positioning accuracy. Measurements have been performed in the real indoor 13m*7.6m environment with many obstacles and the root-mean-square error (RMSE) is less than 0.3m. The proposed system offers a wide range of application in robotics, industrial automation, post-sorting system and so on.

Soil Effects on the Underground-to-Aboveground Communication Link in Ultrawideband Wireless Underground Sensor Networks

Wireless underground sensor networks (WUSNs) is an emerging area of research. They are used in many applications from intelligent irrigation to security and assisted navigation. WUSNs mainly use narrowband systems working in the frequency range below 1 GHz and, therefore, suffer from a poor localization capability and large-sized antennas. The use of impulse radio ultrawideband (UWB) technique allows alleviating these drawbacks. In this letter, the impact of soil on UWB underground-to-aboveground communication link is studied experimentally. More specifically, the effects of the orientation of the buried antenna and burial depth and soil moisture are investigated. The experimental results show that, at 7 GHz, additional attenuations of 10, 34, and 40 dB are noted for depointing the underground antenna by 90°, increasing the depth from 0 to 30 cm and raising the soil moisture from 0% to 20%, respectively. Burial depth lower than 30 cm or soil moisture lower than 20% allow getting acceptable received signal strength (superior to –100 dBm) for communication and localization, particularly in the UWB low band (3.1–5 GHz). The obtained results bring out the feasibility of UWB WUSN.

Backscattering UWB/UHF hybrid solutions for multi-reader multi-tag passive RFID systems

Ultra-wideband (UWB) technology is foreseen as a promising solution to overcome the limits of ultra-high frequency (UHF) techniques toward the development of green radio frequency identification (RFID) systems with low energy consumption and localization capabilities. While UWB techniques have been already employed for active tags, passive tags solutions are more appealing also due to their lower cost. With the fundamental requirement of maintaining backward compatibility in the RFID domain, we propose a hybrid UWB/UHF architecture to improve passive tag identification both in single-reader and multi-reader scenarios. We then develop two hybrid algorithms: the first one exploits the UWB signal to improve ISO/IEC 18000-6C UHF standard, while the other one exploits UWB to enhance a compressive sensing (CS) technique for tag identification in the multi-reader, multi-tag scenario. Both solutions are able to improve success rate and reading speed in the tag identification process and reduce the energy consumption. The multi-reader version of the proposed approaches is based on a cooperative scheme in order to manage reader-tag collisions and reader-reader collisions besides the typical tag-tag collisions. Furthermore, timing synchronization non-idealities are analyzed for the proposed solutions and simulation results reveal the effectiveness of the developed schemes.

Microwave and millimetre wave antipodal Vivaldi antenna with trapezoid‐shaped dielectric lens for imaging of construction materials

High-quality microwave and millimetre wave imaging of construction materials and structures requires ultra-wideband (UWB) techniques to provide high-range resolution as well as a reasonable penetration depth. A modified compact microwave and millimetre wave UWB antipodal Vivaldi antenna is designed and presented in this study. First, the conventional antipodal Vivaldi antenna is designed as a reference antenna. Then, to provide the desired frequency range (3.4-40 GHz) with increased gain at its lower frequencies, the slit edge technique is applied, thus creating a periodic slit edge antipodal Vivaldi antenna (PSEAVA). Finally, a trapezoid-shaped dielectric lens (TDL) as an extension of the substrate is added and optimised to increase gain and directivity at higher frequencies of the frequency range, creating PSEAVA with a TDL (PSEAVA-TDL). The results show that the PSEAVA-TDL has the highest gain (up to 16 dB) and front-to-back ratio (up to 37.5 dB), and the narrowest half power beamwidth (down to 11.7°). A prototype of the proposed PSEAVA-TDL with compact size of 40 × 90 × 0.508 mm 3 is fabricated and applied for the imaging of samples made of construction materials. High-range resolution images of the samples are obtained with this antenna by using synthetic aperture radar algorithm.

An Efficient Transmission Scheme for DCSK Cooperative Communication Over Multipath Fading Channels

Differential-chaos-shift-keying cooperative communication (DCSK-CC) has attracted a great deal of attention in the past five years, because it can overcome the negative effect of wireless multipath fading. However, the conventional DCSK-CC system suffers from a major disadvantage of low data rate due to the resource consumption in cooperation. To address the issue, this paper proposes an efficient cooperative scheme, called partial-sequence CC (PS-CC) scheme , for the DCSK-CC system. In the PS-CC framework, the source and relays only transmit a partial chaotic sequence corresponding to one bit to the destination, while consuming the same transmission energy as DCSK-CC. To validate the feasibility of the DCSK PS-CC system, this paper carries out the error performance, diversity order, and data rate analyses under different cooperative conditions over multipath fading channels. Both numerical and simulated results show that the proposed PS-CC system outperforms the DCSK-based non-cooperative system and DCSK-CC systems over the range of signal-to-noise ratio under study. Moreover, the proposed system can enhance data rate and reduce the computational overhead of the relays as compared with the DCSK-CC system. In addition, it will be demonstrated that the DCSK PS-CC system preserves its advantages in typical ultra-wideband (UWB) channels. Overall, the PS-CC appears to be a desirable cooperative scheme for those applications featured by high-data-rate, low-power, and low-complexity, such as wireless sensor networks using the transmitted reference UWB technique.

An Energy-Efficient Tunable CMOS UWB Pulse Generator

The design of an energy-efficient tunable ultra-wideband (UWB) pulse generator which complies with FCC regulations, without the need for shaping filter, is presented. The proposed pulse generator is based on carrier architecture. A new baseband UWB wavelet is used to modulate digital input data, ensuring better spectral efficiency. By using digital implementation technique, the proposed UWB pulse generator can adjust both the pulse width and the pulse amplitude, allowing more flexibility for use with different UWB technique. The design was simulated by a standard 65-nm CMOS technology. Simulation results show that the consumed energy by pulse is 19.8pJ decreased proportionally as bandwidth spectrum is higher. This shows a very good agreement with the low-power, low-cost UWB systems. The tuning spectrum complies with 3.1–5 GHz regulations.

Echo simulation of lunar penetrating radar: based on a model of inhomogeneous multilayer lunar regolith structure

Lunar Penetrating Radar (LPR) based on the time domain Ultra-Wideband (UWB) technique onboard China's Chang'e-3 (CE-3) rover, has the goal of investigating the lunar subsurface structure and detecting the depth of lunar regolith. An inhomogeneous multi-layer microwave transfer inverse-model is established. The dielectric constant of the lunar regolith, the velocity of propagation, the reflection, refraction and transmission at interfaces, and the resolution are discussed. The model is further used to numerically simulate and analyze temporal variations in the echo obtained from the LPR attached on CE-3's rover, to reveal the location and structure of lunar regolith. The thickness of the lunar regolith is calculated by a comparison between the simulated radar B-scan images based on the model and the detected result taken from the CE-3 lunar mission. The potential scientific return from LPR echoes taken from the landing region is also discussed.

Cooperative angle-of-arrival position localization

Cooperation among unknown-location nodes can improve network positioning coverage as well as localization accuracy particularly in the poor electronic conditions. This paper investigates the cooperative angle-of-arrival (AOA) positioning based on the Ultra Wideband (UWB) technique. An UWB measuring system is built to estimate the AOAs, and then the weighted cooperative positioning algorithm is implemented to determine the locations of the unknown nodes. Theoretical analysis is conducted to evaluate the accuracy of the cooperative AOA localization, and the methods to select neighbors for the distributed localization are proposed as well to improve the localization performance. The results of extensive experiments have shown that the proposed cooperative AOA positioning approach is more accurate.

Flexible sixteen monopole antenna array for microwave breast cancer detection.

Radar based microwave imaging (MI) has been widely studied for breast cancer detection in recent times. Sensing dielectric property differences of tissues over a wide frequency band has been made possible by ultra-wideband (UWB) techniques. In this paper, a flexible, compact monopole antenna on a 100 μm Kapton polyimide is designed, using a high frequency structure simulator (HFSS), to be in contact with biological breast tissues over the 2-5GHz frequency range. The antenna parameters are optimized to obtain a good impedance match over the required frequency range. The designed antenna size is 18mm × 18mm. Further, a flexible conformal 4×4 ultra-wideband antenna array, in a format similar to that of a bra, was developed for a radar-based breast cancer detection system.

NEW HIGH-RATE UWB SCHEME FOR WBAN-BASED HEALTHCARE SYSTEMS

Given the emphasis on increasing wireless network usage for healthcare application, e.g., Wireless Body Area Network (WBAN), the need for high-rate physical layer has become a genuine concern from research and industrial community. The use of the Ultra-Wideband (UWB) is looking especially bright for such systems given its lower energy consumption and performances towards frequency-selective channels. However, the Multi-Band-OFDM-based UWB technique has some inherent limitations as loss in spectral e-ciency due to the use of Cyclic-Preflx (CP). In this paper, a new physical layer scheme for high-rate wireless body area networks based on MB-OFDM with Ofiset Quadrature Amplitude Modulation (OQAM) modulation is presented. The proposed MB-OFDM/OQAM can achieve high spectral and power e-ciency than conventional MB-OFDM system. Moreover, the use of the CP Interval in the conventional MBOFDM removes e-ciently the Inter-Symbols Interferences (ISI) but remains inefiective towards the Inter-Carriers Interferences (ICI) caused by the channel frequency ofiset (FO). The performances evaluation of the proposed technique will be carried-out in realistic UWB-WBANs channels with various scenarios, which will be also presented and studied herein.

Energy-adaptive Pulse Amplitude Modulation for IR-UWB Communications Under Renewable Energy

Impulse Radio Ultra-wideband (IR-UWB) technique has long been recognized for its unique carrierless operation as compared with other communication techniques. The simple and low-cost structure offers great advantages for self-powered embedded wireless systems, in which energy efficiency is a challenging issue due to the fact that most renewable energy sources only offer limited and unstable power supply. In this paper, we present an energy-adaptive Pulse Amplitude Modulation technique for self-powered IR-UWB based communication systems to improve data rate and or time coverage. The basic idea is derived from the fact that domain-specific information in such applications are often available; thus, by jointly exploiting the wireless channel conditions and the non-deterministic characteristics of renewable energy sources, the proposed technique dynamically adjusts the modulation level to enhance the sustainable operation under the unreliable energy supply. Simulation results demonstrate that the proposed technique achieves a much higher data rate and better time coverage than conventional UWB systems. The proposed technique is also insensitive to many practical issues such as the battery aging effect.

Experimental investigation on channel characteristics in tunnel environment for Time Reversal Ultra Wide Band techniques

The objective of this paper is to investigate the potential advantages of the Time Reversal (TR) technique applied to Impulse Radio Ultra Wide Band (UWB) signals for communications in tunnels. Indeed, in an environment with significant multipaths, it has already been outlined that this technique allows mitigating intersymbol interference and increases the peak power received at a target antenna. However, in a tunnel, as a result of the guiding effect of the structure, the spatial diversity degree decreases as the distance between the transmitter and receiver increases. An in‐depth analysis is therefore needed, and we first thus present the main characteristics of the UWB channel deduced from measurements made in a long straight arched tunnel and for a frequency band extending from 2.8 to 5 GHz. In the time domain, waveforms of the impulse radio signal are obtained through an inverse Fourier transform of the measured frequency response and examples are given for different distances varying from 50 m to 500 m. Delay spread and peak‐to‐peak gain are then studied, depending on the communication range. The case for multiple antenna transmission is also considered.