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Ultra-Wideband Communications – An Idea Whose Time Has Come
Abstract
Ultra-wideband (UWB) radio is a fast emerging technology with many unique attractive features that promotes major advances in wireless communications, networking, radar, imaging, and positioning systems. Research in UWB is still in its infancy stages, offering limited resources in handling the challenges facing the UWB communications. Understanding the unique properties and challenges of UWB communications as well as its application in competent signal processing techniques are vital in conquering the obstacles towards developing exciting UWB applications. UWB research and development has to cope with the challenges that limit their performance, capacity, throughput, network flexibility, implementation complexity, and cost. This tutorial focuses on UWB wireless communications at the physical layer. It overviews the state-of-the-art UWB in channel modeling, transmitters, and receivers of UWB radios, and outlines the research directions and challenges that needs to be overcome. Since a signal processing expertise is expected to have major impact in research and development of UWB systems, emphasis is placed on the DSP aspects.
... Within each tap, there are uniformly distributed random phases φ l over the interval [0, 2π], an initial phase φ 0 , and L Doppler frequencies f d . In (24), K is the Rician K-factor, depending on the ratio of the signal power over the direct path to that over scattered paths and the direct line-of-sight (LoS) path acquires a Doppler frequency of f 0 . It is evident that L sets of Doppler frequencies f d can be selected from Jake's spectrum, such that these f d s, in turn, can be used to generate (24), and the probability density function (pdf) of the range of f d can be expressed as, ...
... In (24), K is the Rician K-factor, depending on the ratio of the signal power over the direct path to that over scattered paths and the direct line-of-sight (LoS) path acquires a Doppler frequency of f 0 . It is evident that L sets of Doppler frequencies f d can be selected from Jake's spectrum, such that these f d s, in turn, can be used to generate (24), and the probability density function (pdf) of the range of f d can be expressed as, ...
... On the other hand, UWAC systems often utilise bandwidth that is relatively wide compared to the centre frequency of the signal, thus qualifying as wideband systems in a relative sense [24]. Therefore, we also investigate the behavior of the channel when employing a broader bandwidth with a high centre frequency for communication (see Figure 6, top left-hand side). ...
In this paper, we develop a tractable mathematical model and an emulation framework for communicating information through water using acoustic signals. Water is considered one of the most complex media to model due to its vastness and variety of characteristics, which depend on the scenario, the type of water body (lakes, rivers, tanks, sea, etc.), and the geographical location of the water body being considered. Our proposed mathematical model involves the concept of damped harmonic oscillators to represent the medium (water); Milne’s oscillator technique is used to map the interaction between the acoustic signal and water. Wave equations formulated for acoustic pressure and acoustic wave velocity are employed to characterise the travelling acoustic signal. The signal strength, phase shift, and time delay generated from the mathematical model are then inputted into a Simulink-based emulator framework to generate channel samples and channel impulse responses. The emulator utilises the wide sense stationary uncorrelated scattering (WSSUS) assumption and a finite sum-of-sinusoids (SOS) approach with a uniformly distributed phase to generate the channel samples. By utilising this emulator platform, it becomes feasible to generate profiles for amplitude variation, the Doppler shift, and spread experienced by any travelling signal in various underwater communication scenarios. Such a platform can be employed to simulate different communication scenarios, underwater network topologies, and data for training various learning models. Additionally, it can predict the performance of different modulation, multiplexing, error correction, and multi-access techniques for underwater acoustic communication (UWAC) systems.
... UWB has an added portion in the physical layer used to send and receive data packets specified as IEEE 802.15.4z. This serves as a critical extension not available in other technologies that allows for security techniques, such as cryptography and random number generation, to deter attackers from accessing the UWB communication [47]. Two modes of transmission are supported: ultra-short pulses in the picosecond range, which are also known as impulse radios, and subdividing the total UWB bandwidth into a set of broadband orthogonal frequency-division multiplexed channels. ...
... Therefore, UWB is preferred for applications requiring lower latency, better energy efficiency and accurate positioning, while Wi-Fi is preferred for high-data-rate communications. In addition, in the future, UWB could prove more successful than Bluetooth because of its superior speed, low cost, low power requirements, more secure transmission, superior location discovery and device ranging [47]. In the IoT, UWB is used for perception and, partly, transmission. ...
While a robust and reliable communication network for monitoring the mining environment in a timely manner to take care of people, the planet Earth and profits is key, the mining environment is very challenging in terms of achieving reliable wireless transmission. This survey therefore investigates the reliability of LoRaWAN communication in the mining environment, identifying the challenges and design requirements. Bearing in mind that LoRaWAN is an IoT communication technology that has not yet been fully deployed in mining, the survey incorporates an investigation of LoRaWAN and other mining IoT communication technologies to determine their records of reliability, strengths and weaknesses and applications in mining. This aspect of the survey gives insight into the requirements of future mining IoT communication technologies and where LoRaWAN can be deployed in both underground and surface mining. Specific questions that the survey addresses are: (1) What is the record of reliability of LoRaWAN in mining environments? (2) What contributions have been made with regard to LoRa/LoRaWAN communication in general towards improving reliability? (3) What are the challenges and design requirements of LoRaWAN reliability in mining environments? (4) What research opportunities exist for achieving LoRaWAN communication in mining environments? In addition to recommending open research opportunities, the lessons learnt from the survey are also outlined.
... It is necessary to note that, since the end of the 20th century, the use of UWB signals [4,5] in mass-purpose wireless communication systems has the focus of the scientific community. The beginning of research on mass implementation of license-free UWB solutions is associated with the introduction of a spectral mask by the US FCC [5,6] and the subsequent development of a number of international standards for UWB wireless communications, such as IEEE 802.15.3a [7,8] (not adopted in the end), IEEE 802. ...
... R , V (4) R Output signals of the generators on the testbed CS 1 , CS 2 , CS 3 , CS 4 Chaotic oscillators of the testbed ∆ f Frequency bandwidth of chaotic radio-pulses T P Chaotic pulse length 9. Equation for the sub-circuit C 4 − L 4 − C 3 : the voltage across inductance L 4 is V 4 = V L4 + V 3 . 10. Equation for the currents in the sub-circuit C 4 − L 1 − R E − L 4 − C 5 : the current through capacitor C 4 is the sum of currents J 1 and J 4 , through resistor R E and capacitor C 5 . ...
A modulation method is proposed for generating identical UWB chaotic radio pulses using an analog generator of chaotic oscillations. The problem is on the edge of two contradicting requirements: (1) theoretical ability to produce a huge number of various-shape signals, because of high sensitivity to the initial conditions of the generator; (2) the necessity to reproduce oscillations of the same shape both in the receiver and in the transmitter for the implementation of coherent methods of signal processing. The considered method allows us to resolve this contradiction. A single-transistor chaotic oscillator with single power supply and frequency range 100 to 500 MHz is proposed. A mathematical model of the generator (a system of ODEs) was derived. A method of generating chaotic radio pulses with a reproducible shape that could be varied in a manner that is controlled and natural for UWB radio by means of changing the supply voltage of the chaotic oscillator is shown. The mathematical model of the generator is simulated numerically and proves the proposed ideas. The shaping and the replicability of UWB pulses was experimentally proven in an analog domain on a testbed with four instances of the chaotic generator.
... Historically, the technological evolution of R&C follows along two main trends: a) from low frequencies to higher frequencies and larger bandwidths [1], and b) from singleantenna to multi-antenna or even massive-antenna arrays [2], ( [3]. With recent developments, the combined use of largeantenna arrays and Millimeter Wave (mmWave)/Terahertz (THz) band signals results in striking similarities between R&C systems in terms of the hardware architecture, channel characteristics, as well as signal processing methods. ...
... is the symbol sequence being transmitted, N c is the number of subcarriers, and ψ c,k (t) is the synthesis function which satisfies the Nyquist criterion with respect to 1 Bc and maps x c,m (n) into the signal space. The family of ψ c,m (t) = ω c (t)e j2πm∆f t is referred to as a Gabor system, where ω c (t) is the prototype filter, and ∆f is the subcarrier spacing. ...
Radar and communications (R&C) as key utilities of electromagnetic (EM) waves have fundamentally shaped human society and triggered the modern information age. Although R&C had been historically progressing separately, in recent decades, they have been converging toward integration, forming integrated sensing and communication (ISAC) systems, giving rise to new highly desirable capabilities in next-generation wireless networks and future radars. To better understand the essence of ISAC, this article provides a systematic overview of the historical development of R&C from a signal processing (SP) perspective. We first interpret the duality between R&C as signals and systems, followed by an introduction of their fundamental principles. We then elaborate on the two main trends in their technological evolution, namely, the increase of frequencies and bandwidths and the expansion of antenna arrays. We then show how the intertwined narratives of R&C evolved into ISAC and discuss the resultant SP framework. Finally, we overview future research directions in this field.
... Communication technologies passed through several stages, starting from the simplest system and ending with modern technologies in our time. Recently, many modern technologies have appeared in encoding information, and each technology differs from the other in the e ciency of information transfer [1]. Among these modern techniques is the use of chaos theory, Lorenz, Chua, Rossler Chen [2][3][4][5][6][7][8][9][10][11][12], where these works differed in terms of e ciency in transmitting information [13][14][15][16][17][18][19][20][21]. ...
... The synchronization term can be represented by coupling term where k is coupling factor. Through previous experiments [1,6,7,[11][12][13][14][15][16][17][18][19][20][21][22], it was found that it is better to perform the synchronization process on the y2 channel, and to send the external message on the x1 channel, as follow: ...
Due to the progress of modern technologies in covert communication, in this work a new communication system is proposed using the chaotic system resulting from optoelectronic feedback of semiconductor laser. Where the sinusoidal signal (amplitude A and frequency f were 0.01 a.u and 0.1 a.u respectively) was used to examine the transmission efficiency of the signal and it was found that the purity of the received signal at the receiving unit depends on the amount of synchronization between the two systems, i.e. on the coupling factor between the transmitting and receiving systems. It was found that the ideal value of the coupling factor was 270 a.u at initial condition x i1 , y i1 , z i1 , x i2 , y i2 , and z i2 are 1, 1, 0.005, 1, 1, and 0.05 respectively, as the two systems showed full synchronization between them. Through the results obtained, it was found that the chaotic system resulting from the optoelectronic feedback (OEFB) presents a modern technique for encoding the signal to send it with high confidentiality, and the reason is due to the wide bandwidth of the spectrum of the chaotic system, which allows easy selection of the appropriate frequency for encoding information, and in this way it was possible to open a new field in secret communications.
... Historically, the technological evolution of R&C follows along two main trends: a) from low frequencies to higher frequencies and larger bandwidths [1], and b) from singleantenna to multi-antenna or even massive-antenna arrays [2], ( [3]. With recent developments, the combined use of largeantenna arrays and Millimeter Wave (mmWave)/Terahertz (THz) band signals results in striking similarities between R&C systems in terms of the hardware architecture, channel characteristics, as well as signal processing methods. ...
... is the symbol sequence being transmitted, N c is the number of subcarriers, and ψ c,k (t) is the synthesis function which satisfies the Nyquist criterion with respect to 1 Bc and maps x c,m (n) into the signal space. The family of ψ c,m (t) = ω c (t)e j2πm∆f t is referred to as a Gabor system, where ω c (t) is the prototype filter, and ∆f is the subcarrier spacing. ...
Radar and communications (R&C) as key utilities of electromagnetic (EM) waves have fundamentally shaped human society and triggered the modern information age. Although R&C have been historically progressing separately, in recent decades they have been moving from separation to integration, forming integrated sensing and communication (ISAC) systems, which find extensive applications in next-generation wireless networks and future radar systems. To better understand the essence of ISAC systems, this paper provides a systematic overview on the historical development of R&C from a signal processing (SP) perspective. We first interpret the duality between R&C as signals and systems, followed by an introduction of their fundamental principles. We then elaborate on the two main trends in their technological evolution, namely, the increase of frequencies and bandwidths, and the expansion of antenna arrays. Moreover, we show how the intertwined narratives of R\&C evolved into ISAC, and discuss the resultant SP framework. Finally, we overview future research directions in this field.
... Compared to the solutions mentioned above, ultra-wideband (UWB)-based solutions have become increasingly popular due to their excellent performance in high accuracy, high-speed ranging and positioning [18], [19], [20], [21], [22], as well as their high-speed communication capabilities [23], [24]. These properties make them suitable and optional candidates for ALPTS applications. ...
Most Ultrawideband (UWB) location systems implement the early UWB IEEE 802.15.4 standard. However, recently, the latest UWB IEEE 802.15.4z standard was introduced. Here, to understand the exact performance of the IEEE 802.15.4z standard and thus provide a valuable reference for UWB-based location systems, we present the first performance comparison of the two standards in ranging and positioning, as well as energy efficiency. All comparisons were carried out in a common environment (a typical indoor office) with the same settings used in a critical performance comparison and analysis. The comparisons include both line-of-sight (LOS) and non–line-of-sight (NLOS) conditions. Experimental results indicate that both standards achieve centimeter-level ranging accuracy in LOS conditions, but IEEE 802.15.4z achieves better performance in NLOS conditions with an average ranging error of less than 0.2 m and thus better performance in positioning than that of IEEE 802.15.4. Moreover, IEEE 802.15.4z achieves approximately three times higher energy efficiency than that of IEEE 802.15.4. Therefore, this work provides a comprehensive overview of a practical performance comparison of IEEE 802.15.4z and IEEE 802.15.4.
... A radio communication system is said to be ultra-wideband if either its bandwidth is greater than 500 MHz or its fractional bandwidth (FB) exceeds 20%. Thus, UWB is distinct from other transmissions, which typically occupy 3% of the available bandwidth (Liuqing Y. and Giannakis G.B., 2004). Figure 1 refers to the WiMedia UWB common radio platform that allows highspeed (480Mbps and beyond), low cost and low energy multimedia data transfers in a wireless personal area network (WPAN). ...
Ultra-Wideband (UWB) communication has been the subject of extensive research in recent years due to its unique capabilities and potential applications, particularly in short range multiple access wireless communications. The traditional models of mobile communications desired to be improved upon in the near future because of current demand of high speed of data transmission in area networking. Internet-based streaming, video services and high definition wireless video connections within the home, office and even business environment are an essential feature of the next phase of digital transformation. Ultra-Wideband (UWB) radio technology will play a vital role in promoting these services and products with its very high speed, low cost, low power consumption and dissipation. This paper presents an insight into the WiMedia Ultra-Wideand; current status, operation, applications and possible future perspective. From these general analysis the research presents theoretical and practical findings from which are derived from proven publications within this concept.
... To tackle these issues, ultrawide bandwidth (UWB) technology was introduced in radio transceivers [8] and evolved with IEEE standards [9,10]. These were then referred to as real-time locating systems (RTLSs), which are able to achieve consistent centimeter-level accuracy in the positioning of objects indoors because of their high level of robustness against parasitic multipath components [11]. ...
Over the past few years, the Internet of Things paradigm has brought renewed significant interest to indoor positioning, tracking, and localization topics, principally since real-time locating technology allows a reference node to infer the position of tagged target nodes, creating the opportunity for millions of object-to-object awareness applications. This study first presents an overview of positioning localization techniques and discusses the use of ultra-wide bandwidth technology for complex environment monitoring, followed by consideration of the error sources that are present in line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios between a reader and a tag. A technical review of the available industrial and commercial UWB real-time locating transceivers (RTLSs) is presented, with a focus on the frontend antennas that are integrated in these systems to establish the needed wireless communication for positioning. Then, the different characteristics of these antennas are summarized and discussed, along with their impact on the localization performance in terms of the reading range, position information accuracy, object-orientation-independent localization, and multipath mitigation. Solutions are suggested to achieve antenna-based improvements to the performance of RTLSs.
... С конца 20 века использование сверхширокополосных (СШП) сигналов [1,2] в гражданских беспроводных системах связи находится в центре внимания научного сообщества. На сегодняшний день некоторые СШП технологии уже реализованы на практике. ...
An approach to reduce the negative impact of multipath signal propagation (interpulse interference) in a wireless communication channel has been proposed. Pulse-interval modulation of chaotic radio pulses allows to increase the time interval between pulses without reducing the average bitrate. The possibility of using this method in ultra-wideband microwave channels with multipath propagation is demonstrated. The noise immunity of the AWGN channel has been studied. An experimental implementation of the method is described.
... The most widely adopted UWB multipath channel model has been proposed by the IEEE 802. 15.3a Task Group [9]. ...
Ultra Wideband (UWB) communication is one of the key technology for high data rate networks over short range communication. The ultra wide bandwidth offers pulses with very short duration that provides frequency diversity and multipath resolution. UWB OFDM communication is proposed for physical layer in the IEEE 802.15.3a standard which covers wideband communication for wireless personal area networks (WPANs). Channel estimation is very important for OFDM based UWB system because of its coherent demodulation and channel is time varying. This paper proposes a new blind adaptive channel estimation technique based on orthogonal iteration method for UWB OFDM communication. The channel parameters are adaptively estimated in the proposed method which is based on recursive least square method. The proposed method distinguishes itself from many previously reported channel estimation methods by eliminating the training bits, thereby increasing the channel efficiency. The proposed method is compared with LS based blind channel estimation method in various aspects by computer simulations.
... Among the available technologies for IPS in the literature [2], [3], Ultra-Wideband (UWB) technology has been considered a promising and viable option for GNSS-denied environments [4]. The main reasons for this consideration include the UWB's ability to provide decimeter-level (i.e., centimeter-level) ranging accuracy, penetrate obstacles, support high data rates, potentially offer low-power and compact hardware, resist jamming, be immune to interference, and coexist with narrow bandwidth (NB) technologies [5], [6]. Overview, time-based UWB positioning and navigation is a common practice in the system implementation process. ...
A bidirectional Ultra-Wideband (UWB) localization scheme is one of the three widely adopted design integration processes commonly used in time-based UWB positioning systems. The key property of bidirectional UWB localization is its ability to serve both navigation and tracking tasks within a single localization scheme on demand. Traditionally, navigation and tracking in wireless localization systems were treated as separate entities due to distinct applicable use-cases and methodological needs in each implementation process. Therefore, the ability to flexibly or elastically combine two unique positioning perspectives (navigation and tracking) within a single scheme can be regarded as a paradigm shift in the way location-based services are conventionally observed. This article reviews the mentioned bidirectional UWB localization from the perspective of a flexible and versatile positioning topology and highlights its potential in the field. In this regard, the article comprehensively describes the complete system model of the bidirectional UWB localization scheme using modular processes. It also discusses the demonstrative evaluation of two system integration processes and conducts a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis of the scheme. Furthermore, the prospect of the presented bidirectional localization scheme for achieving precise location estimation in 5G/6G wireless mobile networks, as well as in Wi-Fi fine-time measurement-based positioning systems was briefly discussed.
... Esta tecnología, surgida en la década de 1950 dentro del marco militar, con el objetivo de mejorar las comunicaciones a larga distancia (Yang, 2004), presenta como principal característica, definida por la Comisión Federal de Comunicaciones de Estados Unidos o FCC (Rahayu, 2008), el empleo de un ancho de banda superior a los 500 MHz o al 25% de la frecuencia central (Taylor, 2000), ancho de banda superior a diez veces el correspondiente a otras alternativas de comunicación inalámbrica, permitiendo transmitir información a una mayor velocidad que tecnologías similares (Vázquez, 2012). ...
Debido al desarrollo de la tecnología ultra-wideband en las últimas décadas dentro de los numerosos estándares de comunicación inalámbricos, en este trabajo se desarrolla una interfaz gráfica que permite realizar un análisis de esta tecnología en el campo de la medición de distancias y posicionamiento. Se utiliza para ello el módulo DWM1001-DEV, que incorpora dicha tecnología junto con diferentes modos de conexión y puertos de entrada y salida. La interfaz desarrollada permite establecer una conexión a través del puerto USB con el módulo mencionado y también de forma inalámbrica a través de una red Wi-Fi. Se plantea también el software de gestión de datos y su envío con una placa tipo Raspberry. Se muestra un conjunto de pruebas experimentales utilizando la interfaz y se realiza un estudio preliminar de la calidad de la medida de distancia entre dos módulos DWM1001-DEV.
... Various applications of electronic systems require designers to pay attention on different properties of antennas, depending on the criterion chosen, for example: size, bandwidth, radiation pattern, gain, efficiency and impedance matching. In world literature, the prevailing proposals include single radiators in a wide range of shapes: from the classic ones (rectangle, triangle, circle) to fractal (curves filling space) and nature shapes (flower, tree); there are also examples of large antenna arrays, but there are definitely fewer ideas [8,9,10]. ...
... T HE future of real-time locating systems (RTLS) announces itself to be a prominent topic as its applications find a niche in most domains such as industrial, scientific, economic, and social [1], [2]. ...
Indoor object localization and positioning is part of the space-awareness concept which has seen a rising popularity in recent Internet of Things (IoT) research and applications. This article presents a novel method to improve the localization performance of ultra-wide band (UWB) real-time locating systems (RTLS) by improving the transmitting and receiving reader and tag antennas. Patch directional UWB antennas with relatively higher gain compared to the generally used standard omnidirectional monopole UWB antennas have been exploited to achieve a larger localization range. Furthermore, the patch antennas were designed to have wideband circular polarization to achieve two objectives: a received power independent of the orientation of the tagged objects that need to be detected, and the filtering of unwanted multipath signals. A measurement campaign was conducted using a commercially available RTLS with conventional antennas and then with the newly designed antennas. A comparison between the localization results of the two antenna types demonstrates an improved range with almost 100 m difference, received power independent of tag orientation, and increased multipath mitigation with the directional circularly polarized antennas.
... Essentially, OCDM is a specialized chirp spread spectrum (CSS) technology that achieves the Nyquist signaling rate with optimal spectral efficiency, analogous to OFDM and frequency-division multiplexing (FDM). However, compared to traditional CSS systems, which are notorious for their poor spectral efficiency due to the non-orthogonal chirped waveforms [17]- [19], the chirps in OCDM are mutually orthogonal, and thus attain the maximum spectral efficiency at the so-called Nyquist signaling rate [7]. ...
In multiple-input multiple-output (MIMO) systems, channel estimation is of crucial importance to guarantee reliable recovery of ultra-high-speed MIMO signals. This paper proposes a novel channel estimation algorithm for the emerging MIMO-based orthogonal chirp-division multiplexing (OCDM) systems by utilizing the unique features of OCDM signals. In the proposed algorithm, a set of pilot signals is designed based on the Fresnel basis, which is essentially a family of orthogonal linear chirps. The pilots are assigned to different antennas for transmission occupying the same time slot and bandwidth. According to the convolution-preservation theorem of the Fresnel transforms, the transfer matrices of MIMO-OCDM systems can be readily estimated at the receiver without any inter-antenna interference, even if the pilots overlap in both the time and frequency domains. The proposed algorithm avoids bandwidth waste in conventional channel estimators, in which silent pilots will be required in time and/or frequency to ensure the received MIMO pilots separable. We show that the proposed algorithm is unbiased for the unique OCDM pilots and has better estimate accuracy and system performance. Finally, analysis and numerical results are provided to validate its advantages as a promising algorithm for emerging wireless access technology based on MIMO-OCDM.
... Conventional BSS implementations by electronics are competent in separating narrow-band and low-frequency signals, such as audio signals 20 , but are challenging to achieve a broadband operation due to the limited bandwidth of RF technology. For example, the spectrum of ultrawideband (UWB) signals 21 covers up to 7.5 GHz, and that of Wi-Fi signals has expanded from 2.4 GHz (802.11) to 6 GHz (802.11ax). Having broadband coverage is challenging with a single RF system, as depicted in Fig. 1. ...
The expansion of telecommunications incurs increasingly severe crosstalk and interference, and a physical layer cognitive method, called blind source separation (BSS), can effectively address these issues. BSS requires minimal prior knowledge to recover signals from their mixtures, agnostic to the carrier frequency, signal format, and channel conditions. However, previous electronic implementations did not fulfil this versatility due to the inherently narrow bandwidth of radio-frequency (RF) components, the high energy consumption of digital signal processors (DSP), and their shared weaknesses of low scalability. Here, we report a photonic BSS approach that inherits the advantages of optical devices and fully fulfils its “blindness” aspect. Using a microring weight bank integrated on a photonic chip, we demonstrate energy-efficient, wavelength-division multiplexing (WDM) scalable BSS across 19.2 GHz processing bandwidth. Our system also has a high (9-bit) resolution for signal demixing thanks to a recently developed dithering control method, resulting in higher signal-to-interference ratios (SIR) even for ill-conditioned mixtures.
... arXiv:2302.07706v1 [eess.SY] 15 Feb 2023 the ability of UWB to provide (i) a decimeter-level (i.e., centimeter-level) ranging accuracy, (ii) obstacle penetration capability, (iii) high data rate, (iv) potentially low power and small size hardware, (v) resistance to jamming and immunity to interference, and (vi) coexistence with narrow bandwidth (NB) technologies [5], [6]. In terms of the system implementation process, the setup of UWB-based IPS, especially for the time-based ranging system, can be coarsely divided into three types, namely: (i) the GNSS-liked UWB system, (ii) the inverted GNSS-like UWB system, and (iii) the hybrid approach that combines both scenarios in one topology [7], [8] (Section II). ...
A bidirectional Ultra-Wideband (UWB) localization scheme is one of the three widely deployed design integration processes ordinarily destined for time-based UWB positioning systems. The key property of the bidirectional UWB localization is its ability to serve both the navigation and tracking assignments on-demand within a single localization scheme. Conventionally, the perspective of navigation and tracking in wireless localization systems is viewed distinctly as an individual system because different methodologies were required for the implementation process. The ability to flexibly or elastically combine two unique positioning perspectives (i.e., navigation and tracking) within a single scheme is a paradigm shift in the way location-based services are observed. Thus, this article addresses and pinpoints the potential of a bidirectional UWB localization scheme. Regarding this, the complete system model of the bidirectional UWB localization scheme was comprehensively described based on modular processes in this article. The demonstrative evaluation results based on two system integration processes as well as a SWOT (strengths, weaknesses, opportunities, and threats) analysis of the scheme were also discussed. Moreover, we argued that the presented bidirectional scheme can also be used as a prospective topology for the realization of precise location estimation processes in 5G/6G wireless mobile networks, as well as Wi-Fi fine-time measurement-based positioning systems in this article.
... Therefore, the in-depth theoretical details are omitted and only the necessary concepts for practical implementation of the UWB technology are tackled in an essay manner. For the readers who need more details in theory regarding UWB technology, the author would refer to read the books in [72,154,156,170] and the papers in [70,134,212]. ...
This dissertation addresses a bidirectional scheme of Ultra-Wideband (UWB)-based localization system, which is generally overlooked in the literature causing its potential overshadowed. The bidirectional scheme is one of the three design integration processes usually applied in UWB-based localization systems. The key property of the bidirectional UWB scheme is its ability to act as both navigation and tracking tasks within a single localization scheme. Conventionally, the perspective of navigation and tracking in wireless localization systems is treated separately, because distinct methodologies were typically required in the implementation process. The ability to combine two unique positioning perspectives (i.e., navigation and tracking) within a single scheme is, indeed, a paradigm shift in the way location-based services are observed in the literature. Much to the author's surprise, there are no well-documented books or research articles related to the bidirectional UWB localization system. Thus, this dissertation attempts to serve as a complement to the mentioned gap in the literature. In this dissertation, the bidirectional UWB localization scheme was tackled by dividing the system implementation process into several sectors. Then, the methodologies applicable in each sector were rigorously evaluated in order to give the readers insightful knowledge, findings, and recommendations. Regarding this, the concept of the bidirectional UWB localization scheme and its implementation process were thoroughly explained by comparing it with the typical unidirectional schemes. Concerning the ranging sector of the bidirectional UWB scheme, this dissertation demonstrated the misconception widely practiced in literature in terms of the two-way ranging technique. Moreover, the dissertation suggested a better method compared to the conventional one, which could be used as a baseline or de facto standard for comparing or bench-marking different two-way ranging schemes. The claim was supported by the experimental results rigorously evaluated by using analytical methods, numerical simulation, and real-world experimental data. Moreover, the comprehensive benchmark of five location estimation algorithms for the bidirectional UWB localization system was conducted in the dissertation. The five algorithms were evaluated based on the Bayesian framework and the detailed implementation process was regarded as an important aspect because the literature is generally lacking it, especially for the use-case of the UWB technology. The evaluation results showed that the linear positioning algorithms gave excellent performance in scenarios such as static conditions under a direct path signal. In contrast, the nonlinear techniques appeared to be better at resisting abrupt changes during measurements as well as the scenarios in non-direct path signals. Furthermore, the identification and mitigation of errors produced by non-direct path signals in UWB were addressed. Concerning this, a novel mitigation technique was proposed in the thesis whereas the feasibility of the identification process was evaluated using machine learning methods. The classification procedure was considered as a multi-class problem, which is opposed to the typical binary class approach in literature. The results showed that the machine learning techniques are very promising compared to the conventional ones for identification of the non-direct path signals in UWB localization.
... Sistem ultra-wideband (UWB) didefinisikan memiliki bandwidth relatif lebih besar dari 20% atau bandwidth absolut lebih besar dari 500 MHz [2], [3]. Sistem radio pita sempit konvensional menggunakan sinyal pita sempit yang merupakan bentuk gelombang sinusoidal dengan spektrum frekuensi yang relatif lebih sempit baik dalam transmisi maupun penerimaan. ...
Peningkatkan keandalan sistem multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) dengan memanfaatkan waktu bersama dan demodulasi domain frekuensi diharapkan dapat meningkatkan kinerja. Modulasi posisi pulsa terbalik (I-PPM) terinspirasi dari sistem pulse-OFDM dan lebih lanjut mengambil keuntungan dari posisi pulsa terbalik untuk modulasi domain waktu. Ini diterapkan setelah IFFT dengan membagi jumlah subcarrier untuk mengurangi kompleksitas dan konsumsi daya pada transceiver Dibandingkan dengan demodulasi domain frekuensi konvensional dalam OFDM, equalizer 2D yang diusulkan tidak hanya dapat mencapai probabilitas kesalahan bit (BEP) yang jauh lebih andal, tetapi juga menikmati rasio daya puncak-rata-rata (PAPR) yang sebanding melalui simulasi numerik. Di bawah kanal white Gaussian noise (AWGN) aditif, equaliser 2D (EGCt selektif + EGCf) dapat menghemat sekitar 6 dB dan 4 dB dibandingkan dengan equalizer 1D, domain frekuensi MRC dan EGC, masing-masing pada BER = 10-3. Selanjutnya, di bawah saluran fading Rayleigh, Equaliser 2D (EGCt dan MRCf selektif) mengungguli equalizer 1D, domain frekuensi MRC, sekitar 3,5 dB pada BER = 10-3. Teknik I-PPM MIMO OFDM dapat mencapai kinerja PAPR yang sebanding serta sistem transceiver antena tunggal.
... Against this background, 6th-generation (6G) wireless systems are proposed with large uplink broadband capacity, low latency, and high frequency, which are supposed to be put into commercial use around 2030. ultra-wide band (UWB) technology was specified by Federal Communications Commission (FCC) as a large spectrum with the bandwidth of more than 500 MHz in 3.1-10.6 GHz band in 2002 [1,2]. Since then, research on UWB channels have attracted extensive interests in the field of intra-vehicular wireless sensor network (IVWSN), positioning and so on [3,4]. ...
The demand for wideband data transmission in the “next-generation” mobile communication system is growing rapidly. As the frequency band around 10 GHz could be the option for 6th-generation (6G) wireless communication systems. In this paper, a recently conducted measurement campaign in the 6–14 GHz radio wave propagation channel using a large antenna array with 1024 elements is introduced. In order to investigate the behavior of the wideband channel, we have analyzed the channel characteristics with respect to different carrier frequencies, bandwidths, the locations of antenna elements, and user locations, aiming at exploring the spatio-frequency variability of channels in the massive multiple-input multiple-output (MIMO) scenarios. Moreover, the sparsity of the channel in frequency and spatial domains is evaluated through the degree of freedom (DoF) analysis, and statistical models are established.
... The other is that all-digital receivers are limited by the ADC resolutions and power consumption. The Nyquist sampling rate for IR-UWB may be as high as tens of giga samples per second [181] which is hardly realizable and highly power consuming for high-resolution ADCs. Since the complexity and power consumption of b-bit high-speed flash ADCs increase at the speed of 2 b , a possible solution is to use low-resolution ADCs [123], [182]. ...
With the rapid growth of wireless data traffic and antennas configuration, higher spectrum efficiency and lower power consumption processing have evoked remarkable attention from the research and industry community for the deployment of future wireless communication. It has become a heated topic quickly in recent years and gives rise to the widespread interest around the world. As a core technology of the fifth-generation (5G) mobile communication, massive multi-input multi-output (MIMO) technology can fully exploit the space resources and greatly improve the spectral and energy efficiency. However, massive MIMO systems are faced with the problems of mass data processing, high hardware cost, and huge total power consumption. To cope with these problems, a useful solution is that the receiver equips with finite resolution analog-to-digital (ADC) converters. A large number of research results show that the low-resolution quantization technology brings significant performance within the allowable loss of capacity. This promising technique has attracted many scholars to do tremendous endeavor on it. As a motivation, we make a comprehensive survey about low-resolution ADCs for wireless communication. This paper summarizes the latest developments in the design of low-resolution communication systems, focusing on system performance analysis, some key technologies of the receiver, and typical application scenarios for the low-resolution ADCs. In view of the adverse effects caused by coarse quantization, some potential implementations are presented to alleviate this dilemma. Future research directions are also given and suggested in this paper. This overview contributes significantly to providing an informative and tutorial reference for the key technologies of low-resolution ADCs as well as its applications in practical systems. INDEX TERMS Low resolution quantization, multi-input and multi-output, channel capacity, channel estimation, automatic gain control, synchronization, receiver, relay system.
... There are many phenomena that display non-linear behavior that appear in different systems such as pattern formation, chaos, continuous self-oscillation, and other phenomena (Guokenheimer and Holmes 1993). Because the chaotic system has a broad bandwidth, it has become a destination for many modern technological applications such as broadband sensor networks, complex dynamics in incoherent source with ac-coupled optoelectronic feedback (Failed 2016), realization of a novel chaotic system using coupling dual chaotic system and in secure communications applications (Yang and Giannakis 2004). In secure communication the synchronization of the chaotic signal between the receiver unit and transmitter unit is examined by using coupling factor (Murthy et al. 2011).The recovery of the message at the end of the receiver is investigated, which is based on the synchronization of the chaotic oscillator of the receiver unit and transmitter unit (Kinzel et al. 2010). ...
In this paper, a novel study of the possibility of transferring signals and information from one place to another and in complete secrecy using a chaotic system type Chen model. New chaotic encoder technology was used to encode a range of different signals (sinusoidal, OVEN, and the beats). It has been shown that chaotic carriers allow for successful encoding and decoding of messages, and this really depends on the coupling factor between the transmitting and receiving units. The initial conditions of the transmitting and receiving units of the dynamic system used were changed, meaning that the values (xi1, yi1, zi1, xi2, yi2, zi2) were changed, as there are no two systems identical at the same time unless an external influencer called the coupling factor influences it. It is observed in our work that the best value of the coupling factor k is 100 for sinusoidal and OVEN signals and k = 10,000 for the beats signal. In addition, the effect of changing the frequency value and the amplitude of the transmitted signal on the confidentiality of the system was studied. Through this study, it was found that the efficiency of the system's work reaches 99%.
... Given the prevalence of the two-way ranging scheme that incorporates multiple packets in each transaction, we shall show in section V that using an inappropriate packet as input may result in significantly lower mitigation performance. More importantly, taking as input a single CIR is sub-optimal because of time-variations of real-world RF channels (with sub-millisecond coherence time [17]). To gain more insights, we create a transaction-level synchronized CIR dataset that enables us to study the impact of various CIR combinations. ...
Ultra-Wide-Band (UWB) ranging sensors have been widely adopted for robotic navigation thanks to their extremely high bandwidth and hence high resolution. However, off-the-shelf devices may output ranges with significant errors in cluttered, severe non-line-of-sight (NLOS) environments. Recently, neural networks have been actively studied to improve the ranging accuracy of UWB sensors using the channel-impulse-response (CIR) as input. However, previous works have not systematically evaluated the efficacy of various packet types and their possible combinations in a two-way-ranging transaction, including poll, response and final packets. In this paper, we firstly investigate the utility of different packet types and their combinations when used as input for a neural network. Secondly, we propose two novel data-driven approaches, namely FMCIR and WMCIR, that leverage two-sided CIRs for efficient UWB error mitigation. Our approaches outperform state-of-the-art by a significant margin, further reducing range errors up to 45%. Finally, we create and release a dataset of transaction-level synchronized CIRs (each sample consists of the CIR of the poll, response and final packets), which will enable further studies in this area.
... However, since the entire transmission power of a few milliwatts is distributed over such an extensive frequency range ( Figure 1), interference to narrowband transmission methods is min imised down to a nonsignificant level. The spectral mask that was released by the FCC in 2002 requires UWB radiators to operate at noise floor level (below −41.3 dB m), but also allows for an extensive bandwidth of up to 7.5 GHz [15]. This makes it possible for UWB to coexist with other radio technologies in the spectrum. ...
Physical tickets like RFID or paper-tickets increasingly recede into the background as smartphone based solutions emerge. As such, digital tickets have become more and more popular in several business segments like skiing or parking. As ticketing apps are being developed aiming to minimise interaction effort at turnstiles and barriers, new backbone technologies have to be explored.
Ultra-wideband comes with great potential to be applied in named use-cases. Due to the high adaption trend in the smartphone industry and its technological superiority, UWB appears to be pushing Bluetooth off its place on the market, becoming its successor. This thesis takes a closer look on the radio technology in general, as well as in context of its utilisation in people access solutions.
A proof-of-concept prototype was built and tested in the course of this thesis, validating the practical suitability of UWB to be used in turnstiles. The results are promising.
Autonomous mobile robots (AMRs) play a crucial role in smart factories and Internet of Things (IoT) applications. This paper presents a high-accuracy localization system called the global UWB system (GUS) for the AMR based on ultra-wideband (UWB) distance measurements. By using two UWB modules (tags) on AMR, it is possible to estimate both position and heading angle simultaneously, which can solve the problem of error accumulation over time in internal sensors. A new tightly coupled algorithm called baseline constraint extended Kalman filter (BC-EKF) is proposed. The baseline is the actual distance between the two tags that is used as a constraint for the measurement process. The relationship between the baseline and the heading angle error is also discussed to ensure reasonable deployment of the tags. The proposed localization method is persistent as value of the geometric dilution of precision (GDOP) increases. This helps to secure the performance of the localization method even in tight workspaces where the number of fixed UWBs (anchors) is limited. The simulation and experiment results demonstrate the localization performance of the proposed method.
Exploiting ultra-wide bandwidths is a promising approach to achieve the terabits per second (Tbps) data rates required to unlock emerging mobile applications like mobile extended reality and holographic telepresence. However, conventional digital systems are unable to exploit such bandwidths efficiently. In particular, the power consumption of ultra-fast, high-precision digital-to-analogue and analogue-to-digital converters (DACs/ADCs) for ultra-wide bandwidths becomes impractical. At the same time, achieving ultra-fast digital signal processing becomes extremely challenging in terms of power consumption and processing latency due to the complexity of state-of-the-art processing algorithms (e.g.“, soft” detection/decoding) and the fact that the increased sampling rates challenge the speed capabilities of modern digital processors. To overcome these bottlenecks, there is a need for signal processing solutions that can, ideally, avoid DACs/ADCs while minimizing both the power consumption and processing latency. One potential approach in this direction is to design digital systems that do not require DACs/ADCs and perform all the corresponding processing directly in the analogue domain. Despite existing attempts to develop individual components of the transceiver chain in the analogue domain, as we discuss in detail in this work, the feasibility of complete analogue processing in ultra-fast wireless systems is still an open research topic. In addition, existing analogue-based approaches have inferior spectrum utilization than digital approaches, partly due to their inability to exploit the recent advances in digital systems such as “soft” detection/decoding. In this context, we also discuss the challenges related to performing “soft” detection/decoding directly in the analogue domain, as has been recently proposed by the DigiLogue processing concept, and we show with a simple example that analogue-based “soft” detection/decoding is feasible and can achieve the same error performance as digital approaches with more than 37× power savings. In addition, we discuss several challenges related to the design of ultra-fast, fully analogue wireless receivers that can perform “soft” processing directly in the analogue domain and we suggest research directions to overcome these challenges.
The indoor positioning system (IPS) plays a crucial role in many applications of the Internet of Things (IoT). The trilateration is the most common and widely used method for the IPS because of its computational efficiency and ease of implementation. However, the accuracy of trilateration is affected by the geometric dilution of precision (GDOP). In this article, we propose a constrained least-squares trilateration (CLST) for the IPS that achieves high positioning performance with efficient computations even under severe GDOP conditions. The ultrawideband sensors are used to test the proposed positioning algorithm in this study. The positioning performance of the proposed method is demonstrated by simulations and experiments.
A method for generating chaotic radio pulses using an analog generator of chaotic oscillations is proposed. The method makes it possible to reproduce the pulse wave-form both by the same generator instance and by different instances of structurally identical generators. The pulse waveforms are controlled by the supply voltage of the generator. To prove the concept an experimental test-bed consisting of four identical generators of 100–500 MHz band has been developed. The proposed method can be applied both for coherent reception of chaotic UWB oscillations in the microwave band and for beamforming.
In an indoor environment where global positioning system (GPS) signals are severely attenuated, ultra-wideband (UWB) and 2D lidar are widely used in the autonomous positioning of mobile platforms. However, the presence of nonline-of-sight (NLOS) environments can lead to large errors in UWB positioning, and 2D lidar will increase the cumulative error due to the loss of accuracy in sparsely textured scenes. In order to reduce the positioning error, a UWB and 2D lidar fusion positioning algorithm based on the assistance of a few landmarks is proposed in this paper. Considering the colored noise of lidar location data, a Kalman filter algorithm based on cumulative error analysis is proposed. First, the lidar error curve is fitted by the least-square method, and then the relationship between the noise covariance matrix and the lidar cumulative error function is established by introducing the scale factor, which is substituted into the Kalman prediction equation. Experimental results show that the proposed multi-sensor fusion localization algorithm is feasible, and compared with the single localization method, the proposed fusion algorithm can significantly improve the localization accuracy; matching landmarks can achieve a positioning accuracy of 0.15 m, which is about 24.4% lower than the root mean square error of traditional Kalman filter.
Due to the progress of modern technologies in covert communication, in this work a new communication system is proposed using the chaotic system resulting from optoelectronic feedback of semiconductor laser. Where the sinusoidal signal (amplitude A and frequency f were 0.0 and 0.1 a.u, respectively) was used to examine the transmission efficiency of the signal and it was found that the purity of the received signal at the receiving unit depends on the amount of synchronization between the two systems, i.e., on the coupling factor between the transmitting and receiving systems. It was found that the ideal value of the coupling factor was 270 a.u at initial condition xi1, yi1, zi1, xi2, yi2, and zi2 are 1, 1, 0.005, 1, 1, and 0.05, respectively, as the two systems showed full synchronization between them. Through the results obtained, it was found that the chaotic system resulting from the optoelectronic feedback (OEFB) presents a modern technique for encoding the signal to send it with high confidentiality, and the reason is due to the wide bandwidth of the spectrum of the chaotic system, which allows easy selection of the appropriate frequency for encoding information, and in this way it was possible to open a new field in secret communications. In fact, the percentage matches between the transmitted signal and the received signal reach 99.99%.
An approach is proposed to the filtering of an additive mixture of ultra-wideband chaotic signals and white Gaussian noise, in order to retrieve the useful signal in the receiver. The role of the filter is performed by a passive frequency-selective circuit, identical to the one involved in the formation of oscillations in the chaos generator. A mathematical model of a modulating chaos generator, detecting and receiving a sequence of ultra-wideband chaotic radio pulses in a noisy channel is designed. For the receiver of sequences of symbols encoded by chaotic radio pulses with 2- and 4-position modulation, the bit error ratio as a function of the noise level and the pulse duration is estimated numerically.
Uncertainty is stated as the indication of the quality of the calibration certificate. When uncertainties occurred in a stubbed ground plane, it affects the performance of every source. Hence, a thorough analysis of uncertainties on a monopole antenna is required. The proposed research work is to focus on designing a planar monopole antenna to improve the bandwidth with minimal changes on the ground plane mainly for medical applications and to reduce the uncertainty. The narrowband antenna on the ground plane is redesigned to boost up the gain and broadens the monopole antenna’s bandwidth impedance. Then the ground plane is integrated with the rectangular plate. As a result the bandwidth is 42.5 GHz ahead.
In this paper, we present a novel localization framework which combines the detection results of multiple radars in a distributed heterogeneous radar sensor network. The radar sensor network consists of multiple ultra-wideband (UWB) and frequency-modulated continuous-wave (FMCW) radars, distributed across the region of detection. The UWB radar is used because of its excellent time resolution, which leads to the estimation of distance at a fine resolution. On the other hand, the FMCW radar is used because it can provide velocity and angle measurements in clutter-rich environment. The angle measurement is incorporated into the conventional range-based trilateration algorithm to improve the localization accuracy. In addition, because each radar has a different measurement capability, different weights are assigned to each measurement when deriving the least-squares solution. The performance of the proposed method is demonstrated using experimental data measured in an open space and a clutter-rich environment. The localization results showed that the fusion of UWB and FMCW radar data leads to enhanced localization performance.
In the design of the filter antenna, the filter unit with the same structure as the radiation patch not only improves the selectivity of the band edge, but also helps to improve the in-band impedance. In this design, a compact circular monopole filtering antenna with improved sideband selectivity and in-band impedance using a circular-stub-load resonator is proposed. To obtain better sideband selection characteristics and in-band impedance characteristics, and reduce the mismatch problem caused by the introduction of the filter, a branch-loaded filter with the same resonance mode as the antenna radiation patch is designed. In addition, different shape branch loading structures of the bandpass filter are also studied. The experimental results show that when the loading unit of the filter and the radiation structure of the antenna have the same structure, both good in-band impedance characteristics and sideband selectivity characteristics can be obtained from the filter antenna. The antenna reflection coefficient bandwidth is from 3 to 11 GHz (114%), and the maximum reflection coefficient is only −15 dB, showing good in-band impedance characteristics and sideband selection characteristics. The filter antenna realizes the integration of antenna filtering without increasing the size, and the final size of the antenna is 30 × 25 mm ² .
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.
Orthogonal Time Frequency Space (OTFS) modulation is a recently proposed scheme for time-varying narrowband channels in terrestrial radio-frequency communications. Underwater acoustic (UWA) and ultra-wideband (UWB) communication systems, on the other hand, confront wideband time-varying channels. Unlike narrowband channels, for which time contractions or dilations due to Doppler effect can be approximated by frequency-shifts, the Doppler effect in wideband channels results in frequency-dependent non-uniform shift of signal frequencies across the band. In this paper, we develop an OTFS-like modulation scheme – Orthogonal Delay Scale Space (ODSS) modulation – for handling wideband time-varying channels. We derive the ODSS transmission and reception schemes from first principles. In the process, we introduce the notion of
$\omega$
-
convolution
in the
delay-scale space
that parallels the
twisted convolution
used in the
time-frequency space
. The preprocessing 2D transformation from the Fourier-Mellin domain to the delay-scale space in ODSS, which plays the role of inverse symplectic Fourier transform (ISFFT) in OTFS, improves the bit error rate performance compared to OTFS and Orthogonal Frequency Division Multiplexing (OFDM) in wideband time-varying channels. Furthermore, since the channel matrix is rendered near-diagonal, ODSS retains the advantage of OFDM in terms of its low-complexity receiver structure.
A general method for the evaluation of the symbol er-ror probability (SER) of UWB systems with various kind of mod-ulation schemes (N-PAM, M-PPM, Bi-Orthogonal), in presence of multipath channel, multiuser and strong narrowband interference, is presented. This method is shown to be able to include all the principal multiaccess techniques proposed so far for UWB, time hopping (TH), direct sequence (DS) and optical orthogonal codes (OOC). A comparison between the performance of these multiple access and modulation techniques is given, for both ideal Rake re-ceiver and minimum mean square error (MMSE) equalizer. It is shown that for all the analyzed multiple access schemes, a Rake receiver exhibits a high error floor in presence of narrow-band interference (NBI) and that the value of the error floor is in-fluenced by the spectral characteristics of the spreading code. As expected, an MMSE receiver offers better performance, represent-ing a promising candidate for UWB systems. When the multiuser interference is dominant, all multiple ac-cess techniques exhibit similar performance under high-load con-ditions. If the number of users is significantly lower than the spreading factor, then DS outperforms both TH and OOC. Finally 2PPM is shown to offer better performance than the other modula-tion schemes in presence of multiuser interference; increasing the spreading factor is proposed as a more effective strategy for SER reduction than the use of time diversity.
The issue of bandwidth scaling has always caused some confusion
for channels subject to additive white Gaussian noise plus multipath
fading. On the one hand, there is an old result saying that the capacity
of the channel (under a power constraint but no bandwidth constraint) is
the same as the infinite bandwidth capacity of the non-fading additive
noise channel with the same average received power as the fading
channel. On the other hand, it appears intuitively that when a CDMA
system is spread too widely in bandwidth, it becomes increasingly
difficult for a RAKE receiver to measure the channel and correspondingly
difficult for detection to take place. Here the authors look at a
particularly simple model of the fading channel, but the methodology
appears to be extendable to more general models
This paper examines this emerging field to classify wireless micro-sensor networks according to different communication functions, data delivery models, and network dynamics. This taxonomy will aid in defining appropriate communication infrastructures for different sensor network application sub-spaces, allowing network designers to choose the protocol architecture that best matches the goals of their application. In addition, this taxonomy will enable new sensor network models to be defined for use in further research in this area
We consider the problem of low-sampling rate high-resolution channel estimation and timing for digital ultra-wideband (UWB) receivers. We extend some of our recent results in sampling of certain classes of parametric non-bandlimited signals and develop a frequency domain method for channel estimation and synchronization in ultra-wideband systems, which uses sub-Nyquist uniform sampling and well-studied computational procedures. In particular, the proposed method can be used for identification of more realistic channel models, where different propagation paths undergo different frequency-selective fading. Moreover, we show that it is possible to obtain high-resolution estimates of all relevant channel parameters by sampling a received signal below the traditional Nyquist rate. Our approach leads to faster acquisition compared to current digital solutions, allows for slower A/D converters, and potentially reduces power consumption of digital UWB receivers significantly.
The power spectral density (PSD) of time-hopping (TH) ultra wide band (UWB) signals plays a major role in key aspects like coexistence with conventional radio systems. In the past, several papers have been published, presenting on the one hand the effects of modulation and timing jitter on the PSD assuming random TH codes. On the other hand, papers have been presented dealing with the PSD of specific TH codes without modulation. This paper presents a mathematical framework that enables the evaluation of the PSD of a modulated impulse radio signal using a deterministic TH code. Besides being of theoretical interest, our results can be the starting point for the development of TH code design criteria aimed at the spectral shaping of the UWB signal.
The problem of allocating network resources to the users of an integrated services network is investigated in the context of rate-based flow control. The network is assumed to be a virtual circuit, connection-based packet network. It is shown that the use of generalized processor sharing (GPS), when combined with leaky bucket admission control, allows the network to make a wide range of worst-case performance guarantees on throughput and delay. The scheme is flexible in that different users may be given widely different performance guarantees and is efficient in that each of the servers is work conserving. The authors present a practical packet-by-packet service discipline, PGPS that closely approximates GPS. This allows them to relate results for GPS to the packet-by-packet scheme in a precise manner. The performance of a single-server GPS system is analyzed exactly from the standpoint of worst-case packet delay and burstiness when the sources are constrained by leaky buckets. The worst-case session backlogs are also determined.<
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Channel uncertainty limits the achievable data rates of power constrained wide band systems, where the data rate penalty depends on the number of channel parameters the receiver has to estimate per unit time. Duty cycle transmission reduces the channel un- certainty because the receiver has to estimate the channel only when transmission takes place. The transmission period should equal the coherence time of the channel in order to minimize the channel uncertainty. The duty cycle parameter (fraction of time used for transmission) should be minimized for the same reason, and its optimal value depends on the spectral efficiency of the signal modulation. The optimal duty cycle parameter de- creases as the bandwidth increases, making the signal increasingly bursty. At the limit of infinite bandwidth, direct sequence spread spectrum and pulse position modulation sys- tems with duty cycle achieve AWGN capacity, if the increase of the number of channel paths with the bandwidth is not too rapid. The higher spectral efficiency of the spread spectrum modulation lets it achieve AWGN capacity in the limit, in environments where pulse position modulation cannot be used because of the large number of channel paths.
Synchronization and channel acquisition for ultra-wideband signals are investigated. The channel impulse response is estimated via two approaches: a least-squares method which ignores channel structure, and a subspace technique which rinds channel sparseness and then exploits this structure for final channel estimation. Symbol and frame synchronization is also accomplished using least squares methods. Performance is investigated through the evaluation of mean-squared channel estimation error and probability of error with a RAKE receiver employing the channel estimates for an indoor wireless channel. It is observed that the subspace method exploiting the clustered property of the channel yields the best performance at the expense of complexity.
Abstruet-The problem of allocating network resources to the users of an integrated services network is investigated in the context of rate-based flow control. The network is assumed to be a virtual circuiq comection-based packet network. We show that the use of Generalized processor Sharing (GPS), when combined with Leaky Bucket admission control, allows the network to make a wide range of worst-case performance guarantees on throughput and delay. The scheme is flexible in that d~erent users may be given widely different performance guarantees, and is efilcient in that each of the servers is work conserving. We present a practicat packet-by-packet service discipline, PGPS (first proposed by Deme5 Shenker, and Keshav [7] under the name of Weighted Fair Queueing), that closely approximates GPS. This altows us to relate ressdta for GPS to the packet-by-packet scheme in a precise manner. In this paper, the performance of a single-server GPS system is analyzed exactty from the standpoint of worst-case packet delay and burstiness when the sources are constrained by leaky buckets. The worst-case sewdon backlogs are also determined. In the sequel to this paper, these results are extended to arbitrary topology networks with multiple nodes.
Preface Main Features of Ultra-Wideband (UWB) Radars and Differences from Common Narrowband Radars, Igor I. Immoreev Improved Signal Detection in UWB Radars, Igor I. Immoreev High-Resolution Ultra-Wideband Radars, Nasser J. Mohamed Ultra-Wideband Radar Receivers, James D. Taylor Compression of Wideband Returns from Overspread Targets, Benjamin C. Flores and Roberto Vasquez, Jr. The Micropower Impulse Radar, James D. Taylor and Thomas E. McEwan Ultra-Wideband Technology for Intelligent Transportation Systems, Robert B. James and Jeffrey B. Mendola Design, Performance, and Applications of a Coherent Ultra-Wideband Random Noise Radar, Ram M. Narayanan, Yi Xu, Paul D. Haffmeyer, and John O. Curtis New Power Semiconductor Devices for Generation of Nano- and Subnanosecond Pulses, Alexei F. Kardo-Sysoev Fourier Series Based Waveform Generation and Signal Processing in Ultra-Wideband Radar, Gurnam S. Gill High Resolution Step-Frequency Radar, Gurnam S. Gill The CARABAS II VHF Synthetic Aperature Radar, Lars Ulander, Hans Hellsten, and James D. Taylor Ultra-Wideband Radar Capability Demonstrations, James D. Taylor Bistatic Radar Polarimetry Theory, Anne-Laure Germond, Eric Pottier, and Joseph Saillard
In integrated services networks, the provision of Quality of Service (QoS) guarantees depends critically upon the scheduling algorithm employed at the network layer. In this work we review fundamental results on scheduling, and we focus on Packet Fair Queueing (PFQ) algorithms, which have been proposed for QoS wireline-wireless networking. The basic notion in PFQ is that the bandwidth allocated to a session is proportional to a positive weight
i
. Because of the fixed weight assignment, the inherent in PFQ delay-bandwidth coupling imposes limitations on the range of QoS that can be supported. We develop PFQ with deterministic time-varying weight assignments, and we propose a low-overhead algorithm capable of supporting arbitrary piecewise linear service curves which achieve delay-bandwidth decoupling. Unlike existing service-curve based algorithms, our time-varying PFQ scheme does not exhibit the punishment phenomenon, and allows sessions to exploit the extra bandwidth in under-loaded networks.
Ultra-wideband communications systems offer unique challenges and opportunities for RF circuit design. Proper understanding of the trade-offs that system specifications impose upon the circuit designer is essential in optimizing a system for UWB. The defining attribute of UWB is the wide fractional bandwidth of the signal. This wide bandwidth can be achieved in several ways: with carrierless systems, with a wide-bandwidth single carrier spread-spectrum system, with a multi-carrier system such as OFDM, via frequency hopping, or via some combination of these methods. This paper provides detailed impact analysis of wide fractional bandwidth on RF frontend circuits and examines the various tradeoffs. In particular, wide-bandwidth channels limit the instantaneous Q allowable in the signal path. This requires modifications of the traditional narrowband design methods. Some of the issues discussed in this paper include: issues of broadbanding, power impact, fast hopping tradeoffs, power amplifier, and antenna issues.
We investigate the multipath characteristics of the impulse radios
(IR) which have drawn much attention for future high-speed wireless
communication services. For this objective, we observe the
characteristics of bit error rates through computer simulations for the
deterministic two-path model and the statistical indoor multipath model
of Saleh and Valenzuela (1987). The simulation results indicate that the
performance of the IR system depends on the time-delay differences
between the multipath components, the path gains, the time interval in
the PPM, and the reference signal waveform. It is also observed that the
reference signal waveform used in the AWGN channel can not be applicable
to the multipath channel
The results of indoor multipath propagation measurement using 10-ns, 1. 5-GHz, radarlike pulses are presented for a medium-size office building. The observed channel was very slowly time-varying, with the delay spread extending over a range up to about 200 ns and rms values of up to about 50 ns. The attenuation varied over a 60-dB dynamic range. A simple statistical multipath model of the indoor radio channel that fits the measurements well is presented. More importantly, the model appears to be extendable to other buildings. With this model, the received signal rays arrive in clusters. The rays have independent uniform phases, and independent Rayleigh amplitudes with variances that decay exponentially with cluster and ray delays. The clusters, and the rays within the cluster, form Poisson arrival processes with different, but fixed, rates.
Ultra-wideband (UWB) radios have received increasing attention recently for their potential LPD attributes and low-power consumption and low-complexity implementation. Because of the pulsed or duty-cycled nature of the ultra-short transmitted waveforms, timing synchronization and channel estimation pose major, and often conflicting, challenges. In order to address (or in fact bypass) both tasks, we design and test noncoherent UWB (de)modulation schemes, which remain operational even without timing and channel information. Relying on integrate-and-dump operations of what we term "dirty templates", we first derive a maximum likelihood (ML) optimal scheme. We further establish a conditional ML demodulator with lower complexity. Analysis and simulations show that it can also be applied after (possibly imperfect) timing acquisition, as well as be adapted to a transmitted reference (TR) scheme. The resultant robust-to-timing (RT)TR considerably improves performance of the original TR in the presence of timing offsets or residual timing acquisition errors.
Emerging technologies including wireless multimedia and personal area networks (WPANs) call for high-rate systems capable of supporting multiple users (piconets) with variable rates. These requirements motivate multi-band ultra-wideband (UWB) radios with low-cost, short time-to-market transceivers. Relative to baseband UWB radios, multi-band systems offer certain advantages, but special multiple access (MA) schemes are needed. To this end, we introduce a cross-band flexible UWB MA scheme for multi-piconet WPANs. The resultant so termed FLEX-UWB design offers resilience against multi-user interference (MUI), can accommodate various spreading alternatives, enables full multipath diversity, and can affect scalable spectral efficiency (from low, to medium and high data rates).
Ultra wideband (UWB) communication holds great potential for significantly improved data rate in future wireless systems. Accurate channel estimation and synchronization are critical for successful operation of a UWB system. We propose in this paper a completely blind channel estimation and synchronization algorithm for UWB systems that employ pulse-position modulation. The algorithm exploits the first-order cyclostationarity in the received signal and performs certain circular deconvolution. The complexity is extremely low - only some "overlap-add" operations and FFT operations are needed. The algorithm is capable of simultaneously estimating multiple (say, more than 60) channel taps and there is no ambiguity in either the amplitude or the phase of the estimated channel. It is shown that using the estimated channel from 500 information symbols, the performance can approach that with the known channel within 2 dB in signal to noise ratio for bit error rate less than 0.01.
Ultra-wideband (UWB) radio is gaining increasing attention thanks to its attractive features that include low-power low-complexity baseband operation and ample multipath diversity. Realization of its potential, however, faces the challenge of low-complexity high-performance timing acquisition. In this paper, we develop a blind timing acquisition algorithm for frame-level synchronization. Relying on simple integrate-and-dump operations over one symbol duration, our algorithm exploits the rich multipath diversity enabled by UWB transmissions. It outperforms existing blind algorithms and has comparable performance to data-aided ones. Equally attractive is its applicability to UWB links with or without time hopping (TH), over frequency-flat or multipath channels. It is also worth stressing that our "dirty" template based scheme is able to achieve timing synchronization at any desirable resolution and is readily applicable to non-UWB systems, so long as intersymbol interference is absent.
This paper investigates the timing tolerances of ultra wideband communications (UWB). We quantify the BER sensitivity to timing offsets under various operating conditions and system setups, including AWGN and frequency flat channels, dense multipath fading channels, and different receiver types such as a sliding correlator and RAKE receivers. Through analyses, we illustrate that the reception quality of a UWB system is highly sensitive to both acquisition and tracking errors. In particular, direct-path channels exhibit little tolerance to the tracking error, while for dense multipath channels, the energy capture capability of a RAKE combiner can be severely compromised by mis-timing.
The growing interest towards ultra-wideband (UWB) radios stems from their attractive features that include low-power low-complexity baseband operation, rich multipath diversity, and the potential of enhanced user capacity. Existing baseband spreading codes are not flexible in handling narrowband interference (NBI), which emerges when UWB radios overlay co-existing systems. In this paper, we introduce two novel spreading codes, for baseband UWB multiple access. Utilizing a single or multiple digital subcarriers (SC or MC), these codes give rise to multi-band UWB systems. In addition to providing flexibility in handling NBI, SC- and MC-UWB codes also enable full multipath diversity, and maximum coding gains. Equally attractive is their capability to reduce the number of interfering users, with simple matched filter operations.
Ultra-wideband (UWB) technology is gaining increasing interest for its potential application to short-range indoor wireless communications. Utilizing ultra-short pulses, UWB baseband transmissions enable rich multipath diversity, and can be demodulated with low complexity receivers. Compliance with the FCC spectral mask, and interference avoidance to, and from, co-existing narrow-band services, calls for judicious design of UWB pulse shapers. This paper introduces pulse shaper designs for UWB radios, which optimally utilize the bandwidth and power allowed by the FCC spectral mask. The resulting baseband UWB systems can be either single-band, or, multi-band. More important, the novel pulse shapers can support dynamic avoidance of narrow-band interference, as well as efficient implementation of fast frequency hopping, without invoking analog carriers.
In this paper, a multi-band OFDM system for ultra-wideband communication (UWB) is described. In this system, the UWB spectrum is divided into bands that are 528 MHz wide and the data is transmitted across the bands using a time-frequency code. Within each sub-band, an OFDM modulation scheme is used to convey the information. An overview of the multi-band OFDM system and various system design trade-offs are discussed within this paper. In addition, bit precision requirements, power consumption estimates and performance results in realistic multi-path environments are provided for the multi-band OFDM system.
Realizing the great potential of ultra-wideband radios depends critically on the success of timing acquisition. To this end, optimum data-aided timing offset estimators are derived in this paper based on the maximum likelihood (ML) criterion. Specifically, generalized likelihood ratio tests are employed to detect an ultra-wideband waveform propagating through dense multipath, as well as to estimate the associated timing and channel parameters in closed form. The acquisition ambiguity induced by multipath spreading and time hopping is resolved via a robust ML formulation. The proposed algorithms only employ digital samples collected at a low symbol or frame rate, thus reducing considerably the implementation complexity and acquisition time.
Transmitted-reference (TR) ultra-wideband (UWB) wireless communication systems [R. Hoctor et al., Jan. 2002] can relax the difficult UWB timing requirements and can provide a simple receiver that gathers the energy from the many resolvable multipath components. However, TR-UWB's relatively poor bit error rate (BER) performance and low data rate have limited its application. In this paper, the TR-UWB idea is generalized to address both of these issues. In particular, the aspects of the system that provide the desirable multipath gathering ability and timing attributes are retained, while the remainder of the system is optimized, resulting in a significantly different signaling scheme and receiver back-end. Numerical results for two examples indicate a significant BER improvement over standard TR-UWB under the same timing requirement.
This paper considers a UWB communication system that uses spectral encoding as both the multiple access scheme and the interference suppression technique. The main advantage of this technology is that the transmitted signal spectrum can be conveniently shaped to suppress narrow-band interference. The implementation of such systems considering real-time devices is examined, and its performance is analyzed in the presence of narrow-band interference. Numerical results of the system performance are presented for a UWB channel model, and for two different multipath combining schemes.
In this paper, we describe the leading proposal to the IEEE 802.15.3a wireless personal area networks (WPAN) standardization effort. That proposal relies on ultra wideband (UWB) orthogonal frequency division multiplexing (OFDM). We then propose an enhancement of the baseline system that uses pulsed sinusoids instead of continuous sinusoids to send information in parallel over different sub-carriers. Pulsating OFDM symbols spreads the spectrum of the modulated signals in the frequency domain leading to enhanced performance in multipath fading environments and reduced complexity and power consumption. We also provide a summary of the differences between pulsed OFDM and generalized UWB-OFDM that was proposed earlier. Finally, we present simulation results to confirm the advantages of pulsed UWB OFDM over non-pulsed wideband OFDM.
Synchronization and channel acquisition for ultra-wideband signals are investigated. The channel impulse response is estimated via two approaches: a least-squares method which ignores channel structure, and a subspace technique which finds channel sparseness and then exploits this structure for final channel estimation. Symbol and frame synchronization is also accomplished using least squares methods. Performance is investigated through the evaluation of mean-squared channel estimation error and probability of error with a RAKE receiver employing the channel estimates for an indoor wireless channel. It is observed that the subspace method exploiting the clustered property of the channel yields the best performance at the expense of complexity.
The optimal receiver for an ultra-wideband transmitted reference (UWB TR) system in a single user multipath environment is derived, based on knowledge of channel properties. The performances of this optimal receiver and other crosscorrelation receivers are analyzed and compared. The usual crosscorrelation receiver which is often used in UWB TR systems is shown to be suboptimal. In addition, an UWB differential transmitted reference (UWB DTR) system is also proposed and its performance is evaluated.
Performance of ultra-wideband (UWB) communication systems can be enhanced by collecting multipath diversity gains, once the channels are acquired at the receiver. In this paper, we develop a novel pilot waveform assisted modulation (PWAM) scheme that is tailored for power-limited UWB communications, and can be implemented in analog form. The PWAM parameters are designed to jointly optimize performance and information rate. The resulting transmitter design also minimizes the mean square error (MSE) of channel estimation and thereby achieves the Cramer-Rao lower bound (CRLB).
Ultra-wideband time hopping binary pulse position modulation performance in a free space propagation condition is analyzed. An analytic expression for the bit error rate is obtained, in terms of signal energy-noise power spectral density ratio (E<sub>x</sub>/N<sub>0</sub>), number of users, bit rate and impulse characteristics. Multiple access interference is assumed to be a zero mean Gaussian process. Theoretical results are compared with simulation analysis and the validity of the Gaussian hypothesis is discussed.
Military requirements and civil air traffic control have driven radar development. Many radar functions such as locating aircraft will be taken over by satellite based locating systems. We examine how increasing system bandwidth can provide many new capabilities for civil applications and recommend specific research objectives for future radar research.
Ultra-wideband (UWB) signals as implemented in our localizers provide a foundation for highly accurate methods of 3D position determination using precise ranging between any two nodes. In a large, distributed network of nodes, the time required for all nodes to acquire each other is of paramount importance. We have developed a method of rapid acquisition that allows two nodes to acquire each other in a fraction of the time afforded by other methods. We utilize a beacon/listener technique using Kasami sequences and divide-and-conquer algorithms to effect acquisitions in less than a second. We discuss our rapid acquisition process in this paper.
Previously, the authors have invented and experimented with a new radio communications scheme called delay-hopped transmitted-reference (DHTR) radio. This technique can function either as an impulse radio, or can employ a more traditional spread-spectrum carrier such as broadband noise. The DHTR method is well-suited to short-range transmissions in a high multipath environment, and, in contrast to time-modulated impulse radio, is easy to synchronize at the receiver. Finally, DHTR receivers and transmitters are not highly complex, and can be implemented in a cost-effective way.