Ultra-wideband Signal Transmission Research Articles

The Development and Progress of the UWB Physical Layer.

Ultra-wideband (UWB) technology has been applied in many fields, such as radar and indoor positioning, because of its advantages of having a high transmission rate, anti-multipath interference, and good concealment. In the UWB physical layer, the transmitting link, including an encoder and a pulse generator, is used to improve the anti-interference ability of the signal, while the receiving link, including a receiver and a decoder, can correct the error signal. Therefore, the performance of the UWB physical layer can obviously affect the speed and quality of UWB signal transmission. In this paper, the structure and performance of the codec and transceiver of the UWB physical layer are introduced and compared. In addition, some typical architectures and features are summarized and discussed, which provides a valuable reference and suggestions for the design of the UWB physical layer. Finally, the outlook of the UWB physical layer is presented: its development direction mainly includes high speed, low power consumption, and fewer hardware resources.

On-Demand Precise Tracking for Energy-Constrained UAVs in Underground Coal Mines

The precise tracking of unmanned aerial vehicle (UAV) in coal mines remains a challenging task that faces strict energy constraints. The existing approaches mainly focus on achieving better accuracy but ignore energy consumption. This article proposes an on-demand precise tracking (OPT) framework based on the fusion of the ultrawideband (UWB) and inertial measurement unit (IMU). The fusion unscented Kalman filter (fusion UKF) is devised for energy-efficient tracking with customized performance. First, OPT provides an adaptive adjustment mechanism of UWB signal transmission to trade off between accuracy and energy consumption for UAV local positioning in coal mines. Second, we propose an on-demand trigger algorithm for UAV remote tracking to determine whether the data are transmitted to the ground server. Especially, the on-demand trigger condition is ameliorated due to the existence of packet drops in complicated coal mines. Finally, extensive simulations in the Gazebo Platform and field experiments utilizing P440 UWB nodes in the indoor and coal mine laboratories have been conducted to verify the feasibility. Results show that OPT is efficient and practical and balances the performance and energy consumption under appropriate parameters. Compared with the existing event-triggered extended Kalman filter (ET-EKF) scheme, the accuracy is improved by 10.3%, and the communication rate is contracted by 11.4% in the coal mine environment.

A Ray-Tracing Model for Millimeter-Wave Radio Propagation in Dense-Scatter Outdoor Environments

The future saturation of the electromagnetic spectrum currently allocated for mobile communications has led the scientific and technical communities to consider the use of the vast millimeter-wave frequency band. However, there are technical obstacles limiting the immediate use of this band. In the radio propagation area, there is a research effort to characterize the outdoor urban channel. The developed model described here uses a 2.5 D ray-tracing algorithm based on geometrical optics and uniform theory of diffraction concepts in outdoor environments. The model implements several techniques that could be considered by a future standard of fifth-generation mobile communications for the transmission of ultrawideband signals through line-of-sight (LOS) and non-LOS channels with a high density of scatterers, such as trees, poles, and diffuse scattering by rough building walls. In addition, simulations and comparisons are performed in environments where measurement campaigns were carried out, considering the following metrics: received power, mean delay, root mean square delay spread, and cross-polar discrimination. The comparison between simulation and experimental results shows a good agreement. Possible model impairments are also discussed.

Digital and analogue modulation and demodulation scheme using vortex-based spin torque nano-oscillators

In conventional communications systems, information is transmitted by modulating the frequency, amplitude or phase of the carrier signal, which often occurs in a binary fashion over a very narrow bandwidth. Recently, ultra-wideband signal transmission has gained interest for local communications in technologies such as autonomous local sensor networks and on-chip communications, which presents a challenge for conventional electronics. Spin-torque nano-oscillators (STNOs) have been studied as a potentially low power highly tunable frequency source, and in this report we expand on this to show how a specific dynamic phase present in vortex-based STNOs makes them also well suited as Wideband Analogue Dynamic Sensors (WADS). This multi-functionality of the STNOs is the basis of a new modulation and demodulation scheme, where nominally identical devices can be used to transmit information in both a digital or analogue manner, with the potential to allow the highly efficient transmittance of data.

A full duplex ultrawideband over free‐space optics architecture based on polarization multiplexing and wavelength reuse

AbstractThis article demonstrates the integration of fiber optics with free space optics for the transmission of ultrawideband signals at a data rate of 2 Gbps. The fiber‐based components enable all‐optical generation of ultrawideband signals. The free space optical link allows bandwidth flexibility along with reduced installation costs. The proposed architecture employs polarization multiplexing and carrier reuse in order to make the radio access units simple and cost‐efficient. The free space optical link is modeled using the log‐normal (LN) channel model. Bit‐error‐rate (BER) measurements demonstrate that the proposed link is suitable for the transmission of high throughput ultrawideband signals.

Polarization Multiplexing-Based Ultra-Wideband Over Fiber Communication Employing Direct Modulation and Carrier Re-Use

A cost-efficient ultra-wideband (UWB) over fiber architecture is proposed and demonstrated through simulation results. A directly modulated laser diode at the central unit (CU) is employed to transport and generate downlink UWB signals at a remote access unit (RAU). The directly modulated carrier is re-used at the RAU for transmission of uplink UWB signal. Therefore, all-optical full-duplex transmission of UWB signals at a rate of 2 Gbps is achieved while maintaining very low-bit-error rate (BER) values.

All-optical generation and transmission of multiple ultrawideband signals over free space optical link

Ultrawideband (UWB) signals have low allowable transmission powers. To enhance the coverage and capacity of UWB signals, a cost-efficient solution for the access network has been proposed and simulated. The access network is based on gamma–gamma free-space optical channel model, which is employed between the central unit and the four different carrier-free radio access units (RAUs). All-optical generation and transmission of UWB signals at a rate of 1.5 Gbps to each RAU are demonstrated. Bit error rate results are obtained to observe the performance of the UWB signals received at the mobile stations. The proposed architecture requires minimum deployment cost and gives acceptable bit error rate results.

Model of ultra-wideband signal transmission and reception using the pseudorandom carrier

We show the possibility of transmission and subsequent decoding of an ultra-wideband signal in an optical communication channel using a noise-like carrier. For an example, the simulation of the transmission of word encoded with Baudot telegraph code was realized. The necessary sequence of symbols was introduced into the noise-like carrier represented by a pseudo-random sequence of ultra short pulses. The possibility of the transmitted word decoding to a high degree of reliability was shown by calculation of auto- and cross-correlation functions. To some extent, the method can be treated as an analog of pulse-position modulation.

Sparsity-based narrowband interference mitigation in ultra wide-band communication for 5G and beyond

In real operating environments, the performance of low power large bandwidth ultra wide-band (UWB) communication systems suffers due to narrowband interference (NBI) from high power narrowband interferers. Since noise is not spectrally white in the presence of NBI in UWB systems, conventional matched filter based receivers are not optimum in such scenarios. Although NBI mitigation methods have been proposed using NBI subspace and/or limiters for UWB systems, subspace-based approaches are usually not feasible due to no apriori knowledge of the NBI subspace in a real scenario, and the limiter-based approach is also non-optimum. In this paper, we propose a sparsity-based NBI mitigation method that exploits distinct characteristics of UWB signals and NBI, and does not require a limiter. Improved performance of the proposed receiver has been validated via time hopping binary phase shift keying (TH-BPSK) UWB signal transmission in both additive white Gaussian noise and multipath fading channels.

Optical generation of ultra-wideband signals with a reconfigurable spectral notch-band

A novel method for optical generation of ultra-wideband signals with a reconfigurable spectral notch-band is proposed. In the proposed system, ultra-wideband signals are generated in the optical domain and an optical tunable delay line is deployed to introduce a notch-band to the spectral profile of the generated ultra-wideband signals, which can effectively avoid the signal interference between ultra-wideband signals and pre-planned narrowband wireless signals used in wireless local area networks (WLAN). A theoretical model describing the proposed system is derived; the optical generation and fiber transmission of ultra-wideband signals with a reconfigurable notch-band are demonstrated via computer simulations.

All-optical binary phase-coded UWB signal generation using DWDM-based multi-channel frequency discriminator

A simple all-optical binary phase-coded ultra-wideband (UWB) signal generation scheme only using a DWDM-based multi-channel optical frequency discriminator is proposed and demonstrated. In the proposed scheme, the CW lights emitted from a laser array are modulated in a phase modulator driven by electrical Gaussian pulses, and then are sent to a DWDM used as a multi-channel optical frequency discriminator, in which phase modulation to intensity modulation (PM–IM) conversions are performed, and by locating the phase-modulated light wavelengths at the positive or negative slopes of the DWDM transmission spectra, delaying and recombining each channel signal, binary phase-coded UWB codes are generated. We numerically demonstrate encode and decode process of binary phase-coded UWB signals with a code length of 4, operating at 625Mbit/s. In addition, binary phase-coded UWB signal transmission in fiber link was also numerically investigated. Our proposed system has potential application in future multi-user UWB-over-fiber communication systems.

Simple solutions for photonic power-efficient ultra-wideband system assisted by electrical bandpass filter

We propose and experimentally demonstrate two simple solutions for power-efficient ultra-wideband (UWB) radio frequency (RF) system assisted by an electrical bandpass filter (EBPF). In the first solution, any optical Gaussian pulse with enough bandwidth is transmitted over optical fiber link, and then converted to a power-efficient UWB pulse by an EBPF with a passband of 3.1–10.6 GHz. The transmission and modulation of UWB signal is processed in optical domain, whereas the generation of UWB is processed in electrical domain. Both UWB modulations of on-off keying (OOK) and binary phase shift keying (BPSK) are experimentally demonstrated. In the second solution, the EBPF is used to convert any electrical waveform to a power-efficient UWB pulse. Then the electrical UWB pulse is converted to an optical UWB pulse with a Mach-Zehnder modulator (MZM), and then distributed over long haul fiber link. These two solutions embody the advantages of both low-loss longhaul transmission of optical fiber and mature electrical circuits. And the millimeter-wave UWB signal is also demonstrated.

Influential factors for decimetre level positioning using ultra wide band technology

The integration of wireless and satellite positioning technologies can provide positional information in both indoor and outdoor environments for various location based services and applications. Among different wireless positioning technologies, ultra wide band (UWB) adopts the time delay approach based on highly accurate clock synchronisation between transmitter and receiver antenna. High accuracy range measurement data can therefore be used to derive decimetre accuracy positions. Similar to other wireless technologies, the transmission of UWB signal is subject to interference when propagating through different media. In this paper, influential factors for the theoretical decimetre level positioning expectation of UWB are analysed with a pair of PulseOn P210 devices. Our investigations include signal attenuation in different scenarios of materials of obstruction, multipath and geometrical effects. From the analysis of field test and simulation results, we conclude that UWB can generally achieve better than 0·5 m (95% confidence level), the accuracy of which agrees with specifications of the UWB real time positioning systems (RTLS) available on the market, and field test results of a UWB RTLS conducted by Mok et al. It is essential that UWB device be set up at a higher position to avoid the influence of multipath. When setting up the UWB location system, special attention should be paid to the location of the sensors in weak geometrical strength areas, such as tunnels and narrow corridors.

All-optical switchable UWB pulses generation, modulation and transmission

We proposed and demonstrated all-optical polarity- and shape-switchable ultrawideband (UWB) Gaussian pulses generation schemes using a single polarization interferometer (PI) or a semiconductor optical amplifier (SOA) cascaded by a PI. When an optical signal with dark return-to-zero (RZ) format propagates directly through a single PI, a pair of polarity-reversed UWB monocycle pulses and a positive UWB doublet pulse is acquired respectively only by adjusting the polarization controllers, without changing the bias of the intensity modulator. If a SOA is connected at the input of the PI to firstly implement the first-order differential function to the input dark RZ pulse utilizing gain saturation effect of the SOA, both polarity- and shape-switchable UWB Gaussian monocycle and doublet pulses are all acquired from the cascaded system. Moreover, if a nonreturn-to-zero control signal is introduced into the SOA, utilizing the cross-gain modulation (XGM) effect of the SOA and the differential characteristic of PI, all-optical shape modulation to UWB signals can be realized, and the polarity of the modulated UWB pulses can also be switched. Also, UWB signal transmission characteristics in fiber link were investigated.

Performance evaluation of multiband orthogonal frequency division multiplexing ultra-wideband signal transmission over multimode fibre

The performance of multiband orthogonal frequency division multiplexing ultra-wideband (UWB) signal over a multimode fibre-based radio-over-fibre link is discussed. The co-transmissions of UWB signals with other wireless signal standards, including wireless code division multiple access (W-CDMA) (2.15 GHz), wireless local area network 802.11a/g and global system for mobile communication (1.8 GHz) are considered. Based on the measurement results, it has been shown that UWB signals can be transmitted without error over 400 m for the highest data rate of 480 Mbps using the system proposed. The co-transmission can also be successfully done with minimal mutual interference.

An Efficient Simulation Technology for Characterizing the Ultra-Wide Band Signal Propagation in a Wireless Body Area Network

This paper presents an efficient simulation technology to characterize the Ultra-Wide Band signal propagation between the antennas in close proximity to a human body, where the human body works as a Wireless Body Area Network. The first technique is the hybrid Method of Moments and asymptotic Physical Optics in which the formulation is extended for modeling the dielectric body. The second technique combines the modification of the Multilevel Fast Multipole Algorithm with the Impedance Boundary Condition. These two techniques drastically reduce the computational complexity to model and simulate an electrically very large and complex structure including antennas and human body. Numerical examples showing the effects of the human body on the Ultra-Wide Band signal transmission between two antennas are presented to demonstrate the efficiency of our proposed method.

Combined Analysis of OFDM-UWB Transmission in Hybrid Wireless-Optical Access Networks

The hybrid wireless-optical transmission of ultra-wideband signals employing orthogonal frequency-division multiplexing modulation (OFDM) ultra-wideband (UWB) as defined in the ECMA-368 standard is experimentally analyzed in this letter. The OFDM-UWB signals provide 400 Mb/s per user at optical distances from 5 to 50 km on standard single-mode fiber (SSMF). The analysis includes the wireless radiation from 0 to 3 m after optical transmission. The results indicate a maximum error-vector-magnitude degradation of 2.5 dB measured at 1.5-m radio after 50-km SSMF optical transmission for the first two UWB channels. This degradation translates to 1-m maximum wireless-reach penalty.

Time Domain Characteristics of Band-Notched Ultrawideband Antenna

A study of time domain characteristics of band-notched ultrawideband (UWB) antennas is presented. Two parameters - the correlation factor and the pulse width stretch ratio (SR) are resorted to estimate the time domain characteristics. The high correlation and the values of SR show that the previously proposed antennas are suitable for short-range UWB impulse radio. Ringing distortion of receiving antenna signals caused by the band-notched characteristics is discussed. Measured magnitudes of transfer function and group delay are exhibited. The primary study in this communication is to demonstrate the good performances of the previously proposed band-notched UWB antennas in short-range UWB signal transmission, propagation and reception in time domain.

Impact of Optical Transmission on Multiband OFDM Ultra-Wideband Wireless System With Fiber Distribution

Multiband (MB) orthogonal frequency-division multiplexing (OFDM) ultra-wideband (UWB) wireless, which provides high data rate access, is required to be distributed by using optical fiber. The performance of MB-OFDM UWB over fiber transmission system is investigated considering optical modulation and demodulation impact. Theoretical analysis of the effect of fiber dispersion, optical transmitter, and optical receiver response on system performance is carried out considering amplitude and phase distortion. Experiments are conducted and verified by our theoretical analysis and good agreement is obtained. It is found that RF modulation index of ~4% is optimum for optical transmitter with Mach-Zehnder modulator, and optical receiver with Chebyshev-II response is the best for MB-OFDM UWB over fiber. Compared to back-to-back UWB over fiber, optical transmission is mainly limited by laser phase noise converted relative intensity noise and phase distortion induced by fiber dispersion when optimum modulation index is used. Higher modulation index is limited by amplitude and phase distortion to OFDM signal induced by optical transmitter and receiver response nonlinearities and fiber dispersion and the spectral mask. It is also found that highly received optical power is required for transmission of MB-OFDM UWB signal over fiber.

Experimental Demonstration of All-Optical 781.25-Mb/s Binary Phase-Coded UWB Signal Generation and Transmission

In this letter, an all-optical incoherent scheme for generation of binary phase-coded ultra-wideband (UWB) impulse radio signals is proposed. The generated UWB pulses utilize relaxation oscillations of an optically injected distributed feedback laser that are binary phase encoded (0 and pi) and meet the requirements of Federal Communications Commission regulations. We experimentally demonstrated a 781.25-Mb/s UWB-over-fiber transmission system. A digital-signal-processing-based receiver is employed to calculate the bit-error rate. Our proposed system has potential application in future high-speed UWB impulse radio over optical fiber access networks.