Non-coherent UWB Radio for Low-rate WPAN Applications: A Chaotic Approach

The requirements of low cost, low power and longer operation range for low-rate wireless personal area network (LR-WPAN) applications has driven the utilization of non linear communication approach. In this paper, a combined ultra-wideband (UWB) and chaotic communication technologies is proposed to meet these challenging demands. Among the candidates, the differential chaos shift keying (DCSK) modulation appears to be a very promising solution. The DCSK is a family of transmit reference (TR) system where a correlator based receiver is used to demodulate the received signal. However, this is not very well understood in the literature and therefore we will exemplify this issue in terms of noise performance. Furthermore, the feasibility study of the proposed DCSK is presented through the scalability and link budget analysis in two different operation modes. The system performance in both additive white Gaussian noise (AWGN) channel and standardized IEEE 802.15.4a UWB multipath channels are provided in order to further demonstrate the capability of the proposed system.     

Performance of an Ultra-Wideband Communication System in the Presence of Narrowband BPSK- and QPSK-Modulated OFDM Interference

An analysis is derived for calculating the bit-error probability of an ultra-wideband (UWB) communication system operating with binary phase-shift keying and quaternary phase-shift keying narrowband interference in additive white Gaussian noise. The analytical expressions are valid when phase transitions of the interfering symbols can be ignored. The accuracy of the Gaussian approximation is assessed, and several modulation schemes proposed for UWB communication are evaluated in terms of capability of interference suppression.     

瑞利衰落信道下DCSK系统性能分析

差分混沌键控(DCSK)是一种非相干调制技术,其输出信号具有固有的宽频特性。在各种混沌键控数字调制方案中,DCSK调制有着最优的抗噪声性能。文中在文献[4]的基础上,进一步分析了DCSK在瑞利衰落信道下的系统性能,推导出误码率公式,并通过计算机仿真实验验证了该理论分析的正确性。     

基于光纤光栅的超宽带信号产生与传输

针对现有方法功率利用率低与调制实现困难的问题,采用基于光纤光栅（FBG）的超宽带（UWB）调制信号产生方法,建立了UWB信号产生系统。不仅可以实现UWB信号的调制,而且提高了产生信号的信噪比。实现了二进制相位调制（BPM）、脉冲幅度调制（PAM）和脉冲位置调制（PPM）等UWB信号产生。分析了光纤传输对产生信号的影响,...     

通用差分混沌键控通信系统及其性能分析

在各种混沌通信方案中,差分混沌键控混沌采用了易于实现的非相干解调,因而成为了混沌超宽带通信研究的热点。文章基于传统差分混沌键控通信提出一种通用差分混沌键控通信系统,该系统包含了多种差分混沌键控通信系统。文中理论分析了该系统中每比特采样点数、每符号比特数和信号占空比三个参数对于系统性能的影响,通过仿真证明了理论分析的正确性,最后分析了仿真和理论分析差异产生的原因。     

基于TR-RASK的多输入多输出UWB方案

本文提出了一种基于时间反演接收天线移位键控的多输入多输出超宽带（time reversal receive antenna shift keying multiple input multiple output ultra wide band,TR-RASK-UWB）方案,较好地解决了MIMO-UWB系统中多天线干扰和多径干扰的问题。首先,该方案利用RASK调制将发射天线阵列形成空间波束,同时使用TR技术聚焦发射信号到达目标接收天线;其次,通过最大接收功率检测算法理论推导了该方案在UWB多径信道下的误比特率（bit error rate,BER）表达式,并通过仿真得到验证;最后结果表明,在发射天线和接收天线相同的情况下,所提方案的性能相比于MIMO-UWB有较大提升。      

Ultra-wideband for multiple access communications

Ultra-wideband wireless communications techniques have many merits, including an extremely simple radio that inherently leads to low-cost design, large processing gain for robust operations in the presence of narrowband interference, covert operations, and fine time resolution for accurate position sensing. However, there are a number of challenges in UWB receiver design, such as capturing multipath energy, intersymbol interference especially in a non-line-of-sight environment, and the need for high-sampling-rate analog-to-digital converters. In this article, we provide a comprehensive review of UWB multiple access and modulation schemes, and their comparison with narrowband radios. We also outline the issues with UWB signal reception and detection, and explore various suboptimal low-complexity receiving schemes     

Efficient modulation techniques for satellite telemetry—receiver design and performance evaluation

In this paper we address the design of the data demodulator for high-efficiency satellite communications suited for telemetry applications. We choose Gaussian minimum shift keying as the modulation format and analyse its relative merits with respect to the more traditional filtered offset quadrature phase-shift keying scheme, when applied to medium-to-high data rate telemetry. Our study encompasses both geostationary orbits and the more challenging low earth orbit scenarios, and investigates the acquisition and tracking performance of the receiver with the aid of computer simulations. In particular, we present design criteria leading to the development of efficient, low-complexity schemes for symbol timing and carrier phase/frequency recovery and we analyse the impact of these synchronization algorithms on the system performance. Next, we discuss the demodulator performance degradation when the transmitted signal is passed through on-board solid-state or travelling-wave-tube power amplifiers. The paper is concluded by a comparative analysis of the above modulation schemes, with special emphasis on their power and spectral efficiency.     

Kasami Code-Shift-Keying Modulation for Ultra-Wideband Communication Systems

Ultra-wideband (UWB) communication systems are generally applied to short-range wireless communications. In order to achieve higher rates or to support multiple access capabilities, direct sequence spread spectrum (DSSS) techniques have been introduced to UWB systems, and multiple pulses corresponding to a certain pseudo-noise (PN) code are transmitted to represent a symbol. In addition, the concept of M-ary code shift keying (M-CSK) was introduced into DSSS systems to achieve higher rates. In this work, we propose an M-CSK modulation technique based on the large set of Kasami sequences since it possesses good code properties, including a large code set size and low cross correlations. The modulation and demodulation schemes are developed, and the system performance in additive white Gaussian noise (AWGN) and UWB channels exposed to multiple user interference is investigated thoroughly. It was found that the Kasami M-CSK modulation is superior to other M-CSK modulation schemes in the bandwidth efficiency, and therefore a higher data rate can be achieved. Furthermore, based on our proposed demodulation scheme, the hardware complexity of receivers can be greatly reduced to O(M^1/3), and the implementation of receivers for a very large M becomes feasible.     

Performance Analysis and Optimization Based on Adaptive Modulation and Chaotic Interleaving for Helicopter-Satellite Communications

Overcoming periodic blockage of the received signal and the carrier frequency fluctuations caused by rotor blades and Doppler shift, respectively, are considered the most challenging issues in helicopter-satellite communication systems. In this study, we propose an automatic frequency control method based on an adaptive modulation scheme. We employ a hybrid modulation not only depending on quadrature phase shift keying, but also based on binary phase shift keying for accurate cancellation of periodic blockage. On the other hand, we apply a chaotic interleaving scheme with a hybrid modulation scheme in order to achieve a better Bit Error Rate (BER) performance in LOS and NLOS environments. Finally, we validate the mathematical analysis of the proposed scheme through simulations. We evaluated the performance of the proposed scheme and performed a comparison with conventional schemes. Our results show that the proposed scheme is significantly capable of reducing the acquisition time and working with various velocities of helicopter blades in addition to providing a better BER performance in shadow fading environments.     

Low-cost small-size tapered slot antenna for lower band UWB applications

A low-cost small-size tapered slot antenna (TSA) is investigated in view of ultra-wideband (UWB) applications. First, the bandwidth of the antenna is studied for the lower UWB band: 3.1-4.85 GHz. Secondly, the design is made as small as possible. Thirdly, the pulse distortion of a modulated Gaussian pulse in the lower UWB band, between 3.5 and 4.5 GHz, is investigated based on the measured S/sub 21/-parameter. The low distortion observed indicates that this TSA is suitable for applications in the lower UWB band.     

Miniaturization of UWB Antennas and its Influence on Antenna-Transceiver Performance in Impulse-UWB Communication

In this paper, a co-design methodology and the effect of antenna miniaturization in an impulse UWB system/transceiver is presented. Modified small-size printed tapered monopole antennas (PTMA) are designed in different scaling sizes. In order to evaluate the performance and functionality of these antennas, the effect of each antenna is studied in a given impulse UWB system. The UWB system includes an impulse UWB transmitter and two kinds of UWB receivers are considered, one based on correlation detection and one on energy detection schemes. A tunable low-power Impulse UWB transmitter is designed and the benefit of co-designing it with the PTMA antenna is investigated for the 3.1–10.6 GHz band. A comparison is given between a 50 $\Omega $ design and a co-designed version. Our antenna/transceiver co-design methodology shows improvement in both transmitter efficiency and whole system performance. The simulation results show that the PTMA antenna and its miniaturized geometries are suitable for UWB applications.     

一种新的混沌数字保密通信实现方案

针对差分混沌键控（DCSK）的保密性低,数据传输速率不高等缺点,这里设计并研究了一种新的混沌键控调制方式—调频相关延迟键控（FM-CDSK）通信方案,该方案同时兼具CDSK和FM-DCSK的优点。通过仿真分析验证了该系统在数据传输速率和保密性等方面较DCSK和CDSK都有所提高,传输速率更是比原有键控方式提高了2倍,并且利用该混沌调制方式很好的实现了图像信号的保密传输,验证了该系统在数字保密通信中的可实现性。     

Flexible Chaotic UWB Communication System With Adjustable Channel Bandwidth in CMOS Technology

A flexible chaotic ultra-wideband (UWB) communication system with an adjustable channel spectrum is proposed. Since the chaotic UWB bandwidth (BW) is independent of the data rate, the system band plan can be flexibly organized for various communication environments. The proposed system can overcome the spectral inefficiency and RF power wastage that is typically observed in conventional methods by utilizing adjustable channel allocations. A novel chaotic signal generator is designed with an adjustable frequency range of 3.5-4.5 GHz and BW of 70-620 MHz. The chaotic UWB transceiver system is implemented in CMOS 0.18-mum technology, and it features tunable chaotic signal generation and adaptive detection. The system performance is evaluated for digital data transmission rates of up to 15 Mb/s.     

超宽带波形和调制技术研究

研究了几种不同的脉冲成形和调制技术,并对其性能进行了分析。仿真结果表明,在AWGN信道和瑞利衰落信道下,不同的脉冲形状对脉冲位置调制（PPM）的性能影响较大,而对二进制相移键控调制（BPSK）和开关键控调制（OOK）影响较小,且当采用RZ-Manchester脉冲时,BPSK调制技术下的误比特率（BER）性能在两种信道下均达到最好。     

Accurate evaluation of multiple-access performance in TH-PPM and TH-BPSK UWB systems

A characteristic function method is proposed for precisely calculating the bit-error probability of time-hopping (TH) ultra-wideband (UWB) systems with multiple-access interference in an additive white Gaussian noise environment. The analytical expressions are validated by simulation and used to assess the accuracy of the Gaussian approximation. The Gaussian approximation is shown to be inaccurate for predicting bit-error rates (BERs) for medium and large signal-to-noise ratio (SNR) values. The performances of TH pulse position modulation (PPM) and binary phase-shift keying (BPSK) modulation schemes are accurately compared in terms of the BER. It is shown that the BPSK system outperforms the binary PPM system for all values of SNR. The sensitivity of the performance of the modulation schemes to the system parameters is also addressed through numerical examples.     

差分混沌通信研究综述:信号设计与性能优化

作为一种低复杂度的非相干信息传输方案,差分混沌通信系统以其良好的抗多径衰落性能而受到广泛关注。近年来,研究者围绕着以差分混沌移位键控(DCSK)为代表的差分混沌通信开展了一系列富有成效的研究,逐渐发展了差分混沌通信的信号设计与性能优化方法。为此,该文从信号帧结构设计、正交多级信号设计、信号星座图设计和多载波信号设计4个层面详细综述了差分混沌通信信号设计的主要研究进展。此外,该文重点总结了面向差分混沌通信的噪声抑制辅助性能优化、索引调制辅助性能优化和混沌成形滤波辅助性能优化等方面的研究工作。     

Analysis and CMOS implementation of a chaos-based communication system

We describe the design and CMOS implementation of a baseband spread-spectrum communication system using chaotic signals for spreading digital data. The communication system uses a new chaotic modulation scheme called modified differential chaos shift keying (M-DCSK). The M-DCSK scheme and its characteristics are analyzed for single user and multi user applications. The chaotic signals were generated using a simple and robust circuit. The dynamics of this chaos generating circuit are also studied. The spectral properties of the system are investigated and compared with theoretical expectations.     

基于混沌映射的偏振移位键控光通信系统

提出了一种基于数字混沌与偏振移位键控(PolSK)技术的光保密通信系统.该系统选取几种偏振态部分或完全相同的PolSK方式,在系统不同时钟周期,发送端根据实时产生的数字混沌序列选用不同的PolSK方式调制信息,接收端利用同步的混沌序列与相应的PolSK方式解调信息.数字混沌序列的伪随机特性使得该系统的PolSK调制方式呈现无规则变化.当星座点个数不少于6且选用的PolSK方式不少于4种时,可选的PolSK组合超过1060种,系统的密钥空间庞大.用OptiSystem和Matlab软件相结合的方法进行了系统仿真,并做了一定的数值分析.仿真与分析结果表明,该光通信系统通信正常,具有较强的保密性.     

Generation of 60-GHz MB-OFDM Signal-Over-Fiber by Up-Conversion Using Cascaded External Modulators

In this paper, we demonstrate multiband orthogonal frequency division multiplexing (MB-OFDM) transmission of quadrature phase shift keying (QPSK) modulation with 200-Mb/s bit rate by all-optical frequency up-conversion using external modulator for ultrawideband (UWB) applications to 60-GHz band radio-over-fiber (RoF) network. Error vector magnitude (EVM) measurements are used to evaluate the performance of our system and an EVM root mean square (rms) of 12.6% at 60 GHz is obtained with our technique and corresponds to bit error rate (BER) below $10^{-9}$, in compliance with standard requirements.