Measurement and positioning of moving array shape by IR-UWB

1.1 Impulse Radio (IR) Ultra Wideband (UWB) Communications Ultra wideband (UWB) communication is a fast emerging technology that offers new opportunities such as high data rates, low equipment cost, low power, precise positioning capability and extremely low interference Ghawami (2005). A wide range of possible UWB communication system applications includes radars due to UWB ultra high precision ranging at the centimeter level, wireless personal area networks (WPAN), sensor networks, imaging systems, UWB positioning systems, etc. Yang (2004), Kshetrimayum (2009). From a commercial point of view, the high data rates are the most attractive feature of UWB systems for which speeds of over 100Mb/s have been demonstrated Ghawami (2005). There exist three main types of UWB technologies: impulse radio (IR UWB), direct sequence (DS UWB), and multi-band orthogonal frequency division multiplexing (MB OFDM) Ran (2009). IR UWB communication technique is essentially different from all other communication techniques because it is carrier free and uses for communication between transmitters and receivers very narrow radio frequency (RF) pulses generated from the UWB pulse generator, while traditional transmission systems transmit information by varying the power, frequency, and/or phase of a sinusoidal wave in a modulation process Kshetrimayum (2009), Yao (2007). Consequently, complicated frequency mixers and local oscillators for carrier frequency up and down conversion are not necessary Yao (2007). IR UWB modulation techniques are especially important because the UWB spectrum has been made available by the Federal Communication Commission (FCC) and it can be used with IRs developed to date Lin (2005). Waveforms for IR UWB are designed to obtain a flat frequency response over the bandwidth of the pulse and to avoid a DC component. The large spectrum of a UWB signal may interfere with existing users. In order to keep this interference to the minimum, FCC specifies spectral masks for different applications, i.e. the allowed power output for specific frequencies Ghawami (2005). A contiguous bandwidth of 7.5GHz is available in the frequency interval of (3.1− 10.6)GHz at a maximum power output of −41.3dBm/MHz which is considered as extremely low Ghawami (2005). The power spectral density (PSD) of UWB systems defined as a ratio of the transmitted power P in watts and a signal bandwidth B in hertz is extremely low as compared to other communication systems due to the very wide bandwidth B of short pulses that are typically of nanosecond or picosecond order Ghawami (2005). The selection of the impulse signal type for IR UWB communication system is essential since it determines

The recently allocated 71-76 GHz and 81-86 GHz bands provide an opportunity for realising Line Of Sight (LOS) links for directional point-to-point "last mile" applications. An efficient use of this spectrum may allow wireless to finally "catch up" with wires, leading to systems such as "multi-Gigabit wireless Ethernet," and "wireless fiber." However, the transmission at such a frequency range shows some additional challenges compared to lower frequency bands, from both technological and propagation point of view, which makes difficult to use them efficiently. In this scenario, IR (Impulse Radio) UWB (Ultra Wide Band) technology might offer some more degrees of freedom for the design of a highly integrated and low cost transceiver. This work has at its core the comparison of two main IR-UWB architecture transceivers operating in E band, focusing their performance.

Non-invasive remote health monitoring plays a vital role in epidemiological situations such as SARS outbreak (2003), MERS (2015) and the recently ongoing outbreak of COVID-19 because it is extremely risky to get close to the patient due to the spread of contagious infections. Non-invasive monitoring is also extremely necessary in situations where it is difficult to use complicated wired connections, such as ECG monitoring for infants, burn victims or during rescue missions when people are buried during building collapses/earthquakes. Due to the unique characteristics such as higher penetration capabilities, extremely precise ranging, low power requirement, low cost, simple hardware and robustness to multipath interferences, Impulse Radio Ultra Wideband (IR-UWB) technology is appropriate for non-invasive medical applications. IR-UWB sensors detect the macro as well as micro movement inside the human body due to its fine range resolution. The two vital signs, i.e., respiration rate and heart rate, can be measured by IR-UWB radar by measuring the change in the magnitude of signal due to displacement caused by human lungs, heart during respiration and heart beating. This paper reviews recent advances in IR- UWB radar sensor design for healthcare, such as vital signs measurements of a stationary human, vitals of a non-stationary human, vital signs of people in a vehicle, through the wall vitals measurement, neonate’s health monitoring, fall detection, sleep monitoring and medical imaging. Although we have covered many topics related to health monitoring using IR-UWB, this paper is mainly focused on signal processing techniques for measurement of vital signs, i.e., respiration and heart rate monitoring.

This paper investigates the parameters of time-hopping impulse radio ultra wide band (TH-IR-UWB). At a given spreading factor and a given system load, a trade-off has to be done in the choice of the frame length and the repetition factor. This trade-off lays on the condition of validity of the standard Gaussian approximation for multi user interferences (MUI). This study concerns both pulse amplitude modulation and pulse position modulation and may be applied to UWB networks with high density of users and low data rates like ad-hoc sensor networks, as well as networks with higher data rate and small number of users

Impulse radio ultra wide band (IR-UWB) is gaining consensus within the recently formed IEEE 802.15.4a Task Group as a solution for providing combined communication and ranging in low data rate indoor/outdoor networks. In this work we propose a solution for medium access control in low data rate IR-UWB networks that uses the specific features of IR-UWB and enables location-based network optimizations by providing and storing estimates of the distance between network terminals. The performance of the protocol as a function of channel characteristics, transmission range, number of users and user data rates is evaluated by means of simulations, taking into account an accurate MUI model based on the concept of pulse collision. Results highlight that in all considered scenarios the protocol provides high throughput and low packet delay, and constitutes thus a viable solution for location-aware low data rate UWB networks

An ultra wideband (UWB) technology is a potential candidate for implant body area networks (BANs), where wireless communications are established between inside and outside of a human body. The UWB can accomplish higher data rate than the other frequency band for the implant communication. However, due to its high frequencies, the UWB signals suffer from quite large attenuation in the implant communication link, which makes it difficult to achieve reliable communications. For achieving reliable communication, it is well known that a spatial diversity technique is efficient without any frequency extension. In our previous works, we developed a transmit polarization diversity antenna for the UWB implant communication. However, optimal UWB modulation scheme for transmit diversity were rarely discussed. In this paper, in order to investigate the optimal UWB modulation schemes for implant communication with transmit diversity, we compare the communication performances of UWB-impulse radio (UWB-IR) and multiband-orthogonal frequency division multiplexing (MB-OFDM). For this purpose, we first analyze the propagation characteristics in the implant UWB channel, which ranges from 3.4 GHz to 4.8 GHz, using a finite difference time domain (FDTD) numerical analysis technique. Then, we evaluate and discuss the communication performances of both modulation schemes for the transmit polarization diversity from the viewpoint of the BER and the required transmit power.

Wireless Body Area Networks (WBAN) are endowed with relatively raw but intrinsic motion capture capabilities through radiolocation, which may be of interest for home activity monitoring, large-scale postural rehabilitation or gaming applications. In this context, we propose a solution to localize wearable wireless nodes relatively to a body-strapped Local Coordinate System (LCS). More particularly, we consider adapting a Constrained Distributed Weighted Multi-Dimensional Scaling algorithm (CDWMDS) that asynchronously estimates nodes' locations under fixed-length constraints. This algorithm is fed by inter-node range measurements based on e.g. Impulse Radio - Ultra Wideband (IR-UWB) Time Of Arrival (TOA) estimation. Several new enhancements to the nominal CDWMDS, including nodes censoring and updates scheduling for nodes' locations, are herein put forward to mitigate errors propagation and harmful effects caused by fast moving nodes. Simulation results are provided to illustrate the gains observed on the average location error per node under moderate pedestrian mobility, relying on a realistic biomechanical model.

Ultra-wideband (UWB) and WiFi technologies have been widely proposed for the implementation of accurate and scalable indoor positioning systems (IPSs). Among different approaches, fingerprinting appears particularly suitable for WiFi IPSs and was also proposed for UWB IPSs, in order to cope with the decrease in accuracy of time of arrival (ToA)-based lateration schemes in the case of severe multipath and non-line-of-sight (NLoS) environments. However, so far, the two technologies have been analyzed under very different assumptions, and no fair performance comparison has been carried out. This paper fills this gap by comparing UWB- and WiFi-based fingerprinting under similar settings and scenarios by computer simulations. Two different k-nearest neighbor (kNN) algorithms are considered in the comparison: a traditional fixed k algorithm, and a novel dynamic k algorithm capable of operating on fingerprints composed of multiple location-dependent features extracted from the channel impulse response (CIR), typically made available by UWB hardware. The results show that UWB and WiFi technologies lead to a similar accuracy when a traditional algorithm using a single feature is adopted; when used in combination with the proposed dynamic k algorithm operating on channel energy and delay spread, UWB outperforms WiFi, providing higher accuracy and more degrees of freedom in the design of the system architecture.

Wireless sensor networks (WSNs) are widely used in the modern world. An important requirement for the optimal operation of the network is the determination of the location of the sensor nodes. When building the network, various positioning methods are used, providing the necessary level of accuracy in determining the location of the sensor nodes. It makes it possible to adjust the transmission power of the nodes, to determine which sensors should be in standby mode and which ones to be in working mode, and also to determine the best route for transmitting information. The Angle of Arrival (AoA) method is a method of positioning with respect to the location of the mobile station, which is determined by triangulation of received information collected at multiple access points. The Time of Arrival (ToA) method, also known as the telemetry method, provides one-way measurements of the time difference of signal propagation from the exact time the signal is sent by the transmitter and the exact time the signal is received at the receiver. The Time Difference of Arrival (TDoA) method is based on the concept that a mobile station transmits a message that has been received by at least three access points that are synchronized with other access points. Most of these methods involve approximation and/or linearization, which introduce additional errors. In the present work, an algorithm is proposed for calculating the location of the sensor nodes by the ToA method using a genetic algorithm (GA). An objective function is derived, based on the distances from the reference nodes and the mobile sensor node whose location is sought. This objective function is minimized using a GA, resulting in the desired node coordinates. Investigations of the accuracy of determining the location of the sensor nodes at different accuracy of distance measurement have been made.

In this contribution we develop a multiple-input multiple-output (MIMO) impulse radio ultra wide band (IR-UWB) transceiver for orthogonal signalling over (baseband) muhipath faded MIMO channels. The proposed maximum-likelihood receiver results to be "partially coherent", since it is optimized to work without any information about channel coefficients, and it is based on the knowledge of the arrivals' times of the transmitted signals' replicas. The behavior of the proposed transceiver has been evaluated via three suitable versions of the Union-Chernoff Bound related to several indoor and outdoor propagation scenarios, and these limits are considered to introduce a novel family of unitary orthogonal space-time block codes (e.g., the space-time OPPM (STOPPM) codes), that are able to attain maximum diversity and coding gains.

A theoretical model for non-coherent start-of-frame-delimiter (SFD) detection in IEEE 802.15.4a is presented and closed form solutions for SFD threshold and signal-to-noise ratio (SNR) estimation are derived. The derived results are implemented in an impulse radio ultra wide band (IR-UWB) demonstrator operating in the 6–10.6 GHz UWB band. The demonstrator is designed for low power operation (in the mW range for combined digital base band (DBB) & radio frequency (RF)). The transmitter (TX) RF is duty cycled at pulse level and the receiver (RX) RF is switched to pulse level duty cycling when possible. Moreover, digital TX and RX resources are only switched on when needed. Measurement results are in close agreement with the derived closed form solutions.

An approximation for the Average Error Probability (AEP) of the Pulse Amplitude Modulation (PAM) Impulse Radio Ultra Wide Band (IR-UWB) systems in the presence of Multi-User Interference (MUI) is derived assuming that the spreading codes are fixed in time. The comparison of the proposed theoretical expression and the empirical result shows the accuracy of our approximation for both Direct-Sequence (DS) and Time-Hopping (TH) multiple access techniques. From this approximation, we deduce criterion that enable us to select the set of codes optimizing the performance in terms of the AEP.

This paper proposes a method for mitigation of non-line-of-sight (NLOS) situations in a real time location system (RTLS) using an impulse radio ultra wide band (IR-UWB). Based on our experiment, we found that there is a slight chance to meet the line-of-sight (LOS) at all the readers of RTLS in a realistic scenario. In the NLOS environment, there are two problems of packet-miss error and multi-path error as well. To compensate for the packet-miss error, this paper presents a new algorithm (PPTi), which uses previous time information before the time difference of arrival (TDOA) positioning technique calculates the coordinate of the target. We also employed the Kalman Filter (KF) to mitigate multi-path error. Our proposed algorithm provides a 5.9% increased positioning success rate and a 25.6% decreased root mean square error (RMSE) in an NLOS environment.

In this paper, we propose a new adaptive clutter suppression algorithm in impulse radio ultra wide band IR-UWB) radar system. It effectively removes static clutter signals whereas sufficiently maintaining reflected signals from human body. Compared to previous methods, it makes moving target signals more notable and improves detection probability by increasing peak to average power ratio (PAPR) of desired signals. The performance of the proposed method is verified by applying it to practical measurement results, and it shows more enhanced clutter suppression effect than conventional methods. Furthermore, it improves the detection probability in statistical model-based peak detection.

The ranging and positioning systems for the LR WPAN (low-rate wireless personal area network) have been one of the attracting issues for indoor location applications. In order to support the ranging functions in WPAN, IEEE 802.15.4a Task Group has released new standard of alternative PHY (Physical layer) and amendment of MAC (medium access control) with IR-UWB (impulse radio ultra wide band) signals for high ranging resolution. This paper shows the implementation of IEEE 802.15.4a PHY and MAC protocol for ranging and data communications, and the positioning system including data acquisition, display, and positioning algorithm.