Impacts of impulse-based ultra-wideband data links on cooperative wireless ad hoc networks

The recently permitted unlicenced use of the regulated ultra-wideband (UWB) radio spectrum (regulated first by the US FCC in 2002 and subsequently by the standardisation bodies of EU and other major countries) provides wireless ad hoc networks a cheap and promising air-interface technology for their adopted wireless data links, thus offering the potential to greatly boost their applications. The impacts of such UWB data links, mainly the more likely adopted impulse-based UWB data links for low data rate applications, on the extensively developed cooperative wireless ad hoc networks are investigated. First, the authors investigate the diversity order of data transfer of each impulse-based UWB data link working in a corresponding fading channel, and give an approximate relationship between the diversity order and the channel model parameters (here the Saleh?Valenzuela model parameters); Secondly, the authors develop efficient cooperative and decentralised diversity schemes that can utilise the widely spread and independently distributed multiple paths of the fading UWB channels. Performance analysis and simulation studies show that proposed decentralised cooperative beamforming schemes can achieve full diversity and are more efficient than their decentralised cooperative routing counterparts.     

Ultra wideband technologies coexistence in Nakagami-m fading channels

The wide spectrum of ultra wideband (UWB) communications makes it inevitable to consider strategies for avoiding and mitigating interference from narrowband wireless systems such as GPS, UMTS, and WLAN, or other UWB wireless technologies. In this paper, we provide a performance analysis of multiband orthogonal frequency division multiplexing (MB-OFDM) UWB in the presence of binary phase-shift keying time-hopping (BPSK-TH) UWB or BPSK-DS UWB interfering transmissions under Nakagami-m fading. In the bit-error rate (BER) analysis, several UWB interferers are considered to affect the MB-OFDM signal. A Gaussian approximation is considered for the UWB interferers and used in the analysis of the BER performance of the MB-OFDM UWB system. The Nakagami-m distribution is applied to characterise the amplitude of the fading channels for both the reference signal and the interference signals. Furthermore, a waveforming technique is considered for mitigating the effect of interference and its efficiency is illustrated in terms of BER improvement. Numerical and simulation results are provided and compared for different coexistence scenarios.     

High-speed ultra-wide band in-car wireless channel measurements

Among the different wireless solutions, ultra-wide band (UWB) is a promising technology for in-car communications because of its high data rates. To optimise the UWB radio system design, knowledge of the propagation channel within the car is required. The performance of a high-speed 480 Mbps UWB radio system is studied within a real in-car environment measured under mobility. A comprehensive set of measurements is presented, including several possible non-line of sight scenarios while the vehicle is stationary and mobile, for open- and closed-window environments and with/without occupants. These measurements are used to characterise the in-car channel and evaluate the performance of a typical UWB radio system in this setting.     

V-Shaped Monopole Antenna with Chichena Itzia Inspired Defected Ground Structure for UWB Applications

Due to rapid growth in wireless communication technology, higher bandwidth requirement for advance telecommunication systems, capable of operating on two or higher bands with higher channel capacities and minimum distortion losses is desired. In this paper, a compact Ultra-Wideband (UWB) V-shaped monopole antenna is presented. UWB response is achieved by modifying the ground plane with Chichen Itzia inspired rectangular staircase shape. The proposed V-shaped is designed by incorporating a rectangle, and an inverted isosceles triangle using FR4 substrate. The size of the antenna is 25 mm×26 mm×1.6 mm. The proposed V-shaped monopole antenna produces bandwidth response of 3 GHz Industrial, Scientific, and Medical (ISM), Worldwide Interoperability for Microwave Access (WiMAX), (IEEE 802.11/HIPERLAN band, 5G sub 6 GHz) which with an additional square cut amplified the bandwidth response up to 8 GHz ranging from 3.1 GHz to 10.6 GHz attaining UWB defined by Federal Communications Commission (FCC) with a maximum gain of 3.83 dB. The antenna is designed in Ansys HFSS. Results for key performance parameters of the antenna are presented. The measured results are in good agreement with the simulated results. Due to flat gain, uniform group delay, omni directional radiation pattern characteristics and well-matched impedance, the proposed antenna is suitable for WiMAX, ISM and heterogeneous wireless systems.     

基于空时块编码和正交脉冲的MIMO系统性能研究

为了有效利用脉冲无线电(IR)的短距离、高数据速率以及多输入多输出(MIMO)通信系统的更大容量,提出了一种基于空时块编码(STBC)和正交脉冲的MIMO超宽带(UWB)通信系统。具体实现是通过对标准单输入单输出(SISO)脉冲无线电系统的直接序列超宽带作为多址(MA)技术的IR-MA信号模型以及信道模型、收发器结构和检测方法的分析,提出了一种把空时块编码和正交脉冲相结合的新方法,并采用FS-rake相干接收(CR)和非相干接收(NCR)技术及IEEE UWB信道模型对其获得的空间分集和编码性能进行了研究,从而得到可以相对较好地描述高信噪比时的性能变化趋势的理论上限值。仿真结果表明,这种STBC-IR方案相比于传统的单链路-脉冲无线电(SL-IR)方案,可获得更好的空间分集和编码增益,可用于增加传输距离和减少rake接收机的复杂性,而且在UWB通信中,STBC-IR方案还能很好地消除定时抖动的影响。     

Analytical performance evaluation of ultra-wideband multiple access schemes for different wireless sensor network application environments

One of the most promising uses for ultra-wideband (UWB) is wireless sensor networks (WSNs). Since WSNs offer a wide variety of services for different application areas, the UWB propagation channel characteristics of each application environment show fundamental differences from each other in many aspects. A reliable and energy-efficient multiple access scheme is thus required to coordinate the transmissions of sensor nodes in these various application channel environments. We develop an analytical framework for evaluating the performance of UWB time-hopping (TH), direct sequence (DS) and orthogonal frequency division multiplexing (OFDM) multiple access schemes with multi-node interference in the following UWB propagation channel environments that have a high importance for WSN applications: residential, office, suburban outdoor, industrial and agricultural. The objective is to determine the most appropriate multiple access scheme to be applied for a particular WSN application channel environment. Performance is evaluated in terms of the average information throughput efficiency, a relevant progress-related measure for multihop WSNs. The mathematical expression of this metric is derived in detail, and is used in numerical evaluations for assessing the performance of the three schemes operating under UWB propagation channel models of the various environments that are characterised by distinct channel parameters and specific valid distance ranges. TH-UWB is shown to be the most suitable multiple access scheme to be adopted for UWB WSNs. It outperforms both the DS-UWB and OFDM-UWB schemes for all application environments and is the most robust and energy efficient. OFDM-UWB is the poorest performing whereas DS-UWB provides similar performance to TH-UWB below a specific threshold number of interfering nodes.     

一种基于跨层设计的UWB无线Ad hoc网络MAC层协议

运用跨层设计思想和方法研究了超宽带（UWB）无线自组织（Ad hoc）网络媒体访问控制（MAC）层协议的设计,提出了一种可利用UWB技术定位性好的优势和实现跨层协作的MAC层协议。该协议通过物理层、MAC层和网络层之间的跨层协作来解决自组织网络单信道无线传输过程中的隐藏终端和暴露终端问题以及网络能量节约问题,以提高网络的性能。仿真实验表明,该协议在平均吞吐量、平均端到端时延以及能量开销等性能指标上,均优于已有的IEEE802．11和MACA—BIMAC协议。该协议的设计思想和方法为下一步的UWB无线Ad hoc网络研究奠定了理论和实验基础。     

Non-line-of-sight on-body ultra wideband (1?6 GHz) channel characterisation using different antenna polarisations

Ultra wideband (UWB) is a promising technology for wireless body area networks (WBANs). The authors investigate the wave propagation in the frequency range of 1-6-GHz for non-line-of-sight (NLOS) channels from the front to back of a human body by considering different wave polarisations: perpendicular and tangential with respect to the body. Time domain electromagnetic (EM) simulation using the anatomical model of a human body assuming frequency-dependent tissue properties is conducted. Radiographs of the energy density and delay spread of the NLOS channels are provided. The energy fading of UWB signals for the on-body channel suggests that the optimisation of the receiving antenna position for efficient signal transmission can be useful. A significant enhancement of the on-body communication link is identified by exploiting the transceiver antennas at the perpendicular to body polarisations. The impacts of body environment reflections on the channel characteristics of different polarisations are studied. The results show that the perpendicular polarisation channel characteristics are less influenced by the body environment reflections and are more stable regarding energy density and delay spread than tangential polarisation. The frequency-dependent propagation loss of on-body UWB channels is derived, where the efficient communication bandwidths for both perpendicular and tangential wave polarisations are given.     

Ergodic Capacity Evaluation of Multi-Hop Decode-and-Forward MIMO-OFDM Relaying Network

Spatial diversity plays a significant role in wireless communication systems, including the Fourth Generation (4G) and Fifth Generation (5G) systems, and it is expected to be a fundamental part of the future wireless communication systems as well. The Multiple-Input Multiple-Output (MIMO) technology, which is included in the IEEE 802.16j standard, still holds the most crucial position in the 4G spectrum as it promises to improve the throughput, capacity, spectral, and energy efficiency of wireless communication systems in the 2020s. This makes MIMO a viable technology for delay constrained medical and health care facilities. This paper presents an approximate closed-form expression of the ergodic capacity for the Decode-and-Forward (DF) protocol MIMO-Orthogonal Frequency Division Multiplexing (OFDM) relaying network. Although MIMO-OFDM is highly valuable for modern high-speed wireless communication systems, especially in the medical sciences, its performance degrades in multi-hop relay networks. Therefore, in this paper, an approximate closed-form expression is derived for an end-to-end ergodic capacity of multi-hop DF MIMO-OFDM wireless communication system has been presented. Monte-Carlo simulations are conducted to verify the performance of the presented analysis regarding the capacity (bits/s/Hz) for different SNR-dB values for single, 2 × 2, 4 × 4, and multi-hop DF MIMO-OFDM systems. The presented results provide useful insights for the research on the end-to-end ergodic capacity evaluation.     

无线通信系统仿真中的性能指标的测量

面向3G和4G的下一代无线通信系统复杂性远高于传统系统，基于经验法则的传统设计方法具有较大的局限性，理论仿真支撑的网络规划和系统仿真显得尤为重要。近年来计算机软件仿真技术和无线通信数学模型已渐趋成熟，目前无线通信系统的设计标准化流程一般是从软件仿真开始。特别是对于3G和4G无线系统，由于系统复杂性的提高，在系统设计和规划阶段必须首先在仿真环境中测量各项系统性能指标。本文首先介绍基于MATLAB的无线通信系统仿真技术和无线通信仿真系统的常用测量指标，然后通过搭建基于DCA算法的无线通信仿真系统在软件环境中测量了相关的性能指标。文章最后利用该测试手段结合DCA算法在不均衡用户分布环境中的性能表现的实例给出了软件仿真结果和仿真数据分析。     

M-PAM space?time trellis codes for ultra-wideband multiple-input multiple-output communications

Multiple-input multiple-output (MIMO) systems with space-time (ST) coding are desirable in ultra- wideband (UWB) communication systems to improve the error-rate performance of the UWB link. The authors have considered the design of optimal (in error-rate performance) M-ary pulse-amplitude modulated (M-PAM) ST trellis codes (STTC) for a pulse-based UWB MIMO communication system. Following the approach by Vucetic et al. for narrowband systems, the authors carry out a probability of error analysis to derive upper bounds on pairwise symbol error probability for a UWB communication system for slow fading and fast fading at both low and high signal-to-noise ratios (SNRs). The authors deduce the design criteria from the upper bounds. Based on these criteria, an optimal four-state binary-PAM STTC, for two transmit antennas, is designed by hand. Finally, simulation results of the optimal binary-PAM STTC in a UWB communication system confirm significant improvement in bit error-rate performance over previously proposed ST coding scheme for UWB, at higher transmit SNR.     

Simple correlated channel model for ultrawideband multiple-input multiple-output systems

A simple correlated channel model for ultrawideband (UWB) multiple-antenna systems is proposed. The authors show that a single numerical value of the spatial correlation coefficient is sufficient to accurately model the performance of UWB spatial multiplexing systems in an indoor environment. The appropriate value of the correlation coefficient is selected by ensuring a close match between the bit error rate results achieved on the proposed correlated channel and those on the measured indoor channel. The authors also experimentally confirm that the performance substantially degrades in the presence of high values of spatial correlation for a range of spatial multiplexing receivers, and quantify the relationship between this degradation and the value of the spatial correlation coefficient. Thus, a route for the development of the existing standards for single- antenna UWB channels to the multiple-antenna regime is provided here.     

Ultra-wideband detect and avoid procedure for WiMAX victims

Detect and avoid (DAA) procedures aim at improving ultra-wideband (UWB) coexistence with existing narrowband/wideband licenced/unlicenced victim terminals operating in the same band at the same time and area. The authors propose a DAA procedure that can be used to reduce the percentage of time the UWB interferes with victims operating in a time division duplexing (TDD) mode. The authors consider a system scenario where a TDD terminal has a primary role and UWB devices create a secondary network on a local area basis. A DAA procedure is implemented only in the UWB devices that adapt their transmissions in order to avoid or reduce interference on primary device(s) in the same area. The performance of the proposed DAA procedure is presented and discussed and its dependence on some key UWB transmission parameters, bit rate and the emitted power is evidenced. It is shown that the DAA timeout parameters can be tuned so as to arbitrarily reduce the average percentage of time the UWB interferes with the considered victim systems even well below the limits imposed by regulatory bodies. It is shown that interference reduction is obtained at the expense of reduced performance of the UWB transmission. The proper selection of DAA timeouts for a desired percentage of UWB interference and UWB link efficiency is discussed.     

Ultrasparse, ultrawideband arrays

This paper investigates the properties of highly thinned ultrawideband (UWB) arrays. The design aim is high resolution and very low side radiation levels (SL). One- and two-dimensional ultrasparse UWB arrays can be designed to achieve both. The minimum available pulse-echo SL is shown to approach N(-4) where N is the number of elements in the transmit and receive arrays. Periodic thinning is shown to be superior to random thinning, and amplitude taper is shown to raise the SL. Two-dimensional curvilinear deployment of elements are shown to outperform rectilinear designs, and different transmit and receive arrays in pulse-echo systems are shown to outperform systems that use the same array for transmit and receive. Very low SL is achievable in an ultrasparse UWB system with so few elements that echo signal-to-noise ratio (SNR) rather than SL becomes the constraint on the minimum number of elements required by the system for the array to be useful for imaging. For example, in ultrasonic pulse-echo breast imaging, SL approximately -70 dB is desired to distinguish small cysts from tumors. A 2-D randomly thinned array requires about 10,000 elements. A 2-D ultrasparse UWB periodic array requires less than 100 to satisfy SL, a reduction of 100:1, but provides insufficient SNR. A 500-element, 7.5 MHz array operating with 4 cm penetration depth satisfies both. Experimental results demonstrate the theory.     

Feasibility of ultra-wideband SAW RFID tags meeting FCC rules

We discuss the feasibility of surface acoustic wave (SAW) radio-frequency identification (RFID) tags that rely on ultra-wideband (UWB) technology. We propose a design of a UWB SAW tag, carry out numerical experiments on the device performance, and study signal processing in the system. We also present experimental results for the proposed device and estimate the potentially achievable reading distance. UWB SAW tags will have an extremely small chip size (<0.5 times 1 mm²) and a low cost. They also can provide a large number of different codes. The estimated read range for UWB SAW tags is about 2 m with a reader radiating as low as <0.1 mW power levels with an extremely low duty factor.     

Coding and Modulation for LMDS and Analysis of the LMDS Channel

Local Multipoint Distribution Service (LMDS) has the potential to become a viable alternative to coaxial cable, fiber and other wired and wireless technologies providing “last mile” communication services. A major obstacle, however, is the high equipment cost. While for example cable modems supporting two-way services are available for $200 to $300, LMDS modem providing similar services will cost over $1000. The major cost driver of LMDS equipment is the radio frequency (RF) unit, as Ka-band technology still is quite expensive. The modem design must minimize the overall architecture cost, and low-cost modems requiring an expensive architecture should not be used. The channel characteristics of LMDS systems are very different from those of fiber, coaxial cable, and lower frequency wireless links, major channel impairments being non-linear high power amplifier (HPA), high phase noise and high co-channel interference. Modems should therefore be developed specifically for LMDS systems. This report deals with the choice of coding and modulation schemes, the LMDS channel, and how the channel impairments should be overcome by digital signal processing algorithms.     

An Experimental Investigation of the Multipath Propagation of Chaotic Radio Pulses in a Wireless Channel

Technical Physics Letters - An experimental investigation of the multipath propagation of ultrawideband (UWB) microwave chaotic radio pulses in a wireless channel has been carried out. Based on the...     

MIMO-Terahertz in 6G Nano-Communications: Channel Modeling and Analysis

With the development of wireless mobile communication technology, the demand for wireless communication rate and frequency increases year by year. Existing wireless mobile communication frequency tends to be saturated, which demands for new solutions. Terahertz (THz) communication has great potential for the future mobile communications (Beyond 5G), and is also an important technique for the high data rate transmission in spatial information network. THz communication has great application prospects in military-civilian integration and coordinated development. In China, important breakthroughs have been achieved for the key techniques of THz high data rate communications, which is practically keeping up with the most advanced technological level in the world. Therefore, further intensifying efforts on the development of THz communication have the strategic importance for China in leading the development of future wireless communication techniques and the standardization process of Beyond 5G. This paper analyzes the performance of the MIMO channel in the Terahertz (THz) band and a discrete mathematical method is used to propose a novel channel model. Then, a channel capacity model is proposed by the combination of path loss and molecular absorption in the THz band based on the CSI at the receiver. Simulation results show that the integration of MIMO in the THz band gives better data rate and channel capacity as compared with a single channel.     

Error performance of ultrawideband spatial multiplexing systems

In this paper, a number of ultrawideband (UWB)multiple-input multiple-output (MIMO) spatialmultiplexing systems are presented and their error performance is analysed. For both model-based and measured UWB channels, the performance of various MIMO detectors is evaluated under the multiband orthogonal frequency division multiplexing (MB-OFDM) regime. Contrary to expectation, the results demonstrate that significant spatial diversity can be extracted, in addition to linear data-rate scaling, despite the large frequency diversity inherent in the UWB channel. It is shown that nonlinear detection schemes with reasonable complexity can provide considerable diversity gain, in contrast to well-known linear receivers. Thus, the proposed UWB spatial multiplexing schemes not only increase the data rate but also provide significant diversity gain and improved error rate performance.     

Ultra-wide bandwidth in-vehicle channel measurements using chirp pulse sounding signal

A novel ultra-wide bandwidth (UWB) channel measurement approach based on chirp pulse sounding signal in an automotive vehicle is proposed. An UWB channel impulse response (CIR) estimator using de-convolution technique is constructed to verify that the chirp pulse sounding signal generated with rectangular window is 12.71 dB better in accuracy than the Gaussian pulse sounding signal to measure the CIR of the UWB channel. The UWB channel measurement in the frequency band of 4.25-4.75 GHz is carried out inside an automotive vehicle. The experimental results validate the correctness of using chirp pulse sounding signal to measure the UWB channel inside an automotive vehicle with windows closed through the root mean square delay spread for Cases A and B radio propagation channel models of IEEE 802.15.3a UWB standard when the threshold is properly chosen. Also, test results show that opening the vehicle s window may change the channel characterisation.