基于Hermite函数的超宽带脉冲波形设计与性能分析

根据联邦通信委员会关于超宽带辐射功率谱的限制以及适用于多址方式的窄脉冲要求,设计了一组基于Hermite函数的超宽带脉冲波形。所设计的脉冲波形具有正交性和不随阶数变化的恒定脉宽两个重要特性,从而提供了良好的防时间抖动性能并有效降低符号间干扰;为了评估相关接收机的性能,对设计脉冲信号的自相关和互相关函数的闭合表达式进行了推导;分析了跳时脉位调制超宽带系统中脉冲波形在加性高斯白噪声、多址干扰、多径衰落信道等多种环境下的误码率性能,探讨了时间抖动对系统性能的影响,并将仿真结果与高斯单周期脉冲进行比较。分析结果表明该脉冲设计方案提供了一种灵活而系统的超宽带脉冲设计方法,所设计脉冲既满足辐射功率谱限制又提供良好的系统误码性能。     

基于AGC方法的软判决LDPC译码器输入匹配电路

针对低密度奇偶校验码(LDPC)译码器性能受输入软信息电平抖动影响较大的问题,本文提出一种基于自动增益控制(AGC)方法的输入匹配电路,能够跟踪输入的信号电平变化动态调整信号幅度,使解调器与LDPC译码器始终工作在最佳匹配状态.此方法及AGC结构匹配电路模块已用于实现高速超宽带(MBOK-UWB)无线通信系统接收机的LDPC译码器,系统仿真和实际测试结果均表明,上述方法有效提高了系统的误比特性能.     

基于PPM与LDPC的迭代解调中脉冲展宽与时间抖动对系统性能研究

在以光子计数为基础的空间光通信系统中,每个入射光子都有可能经历一个随机的脉冲展宽,在光子抽样判决中可能存在随机的时间抖动。时间抖动和脉冲展宽会导致本时隙光脉冲展宽到相邻的时隙中,从而导致传输数据译码错误。文章基于泊松信道下的PPM与LDPC码循环迭代解调系统,研究了时间抖动和脉冲展宽不同方差的情况下系统性能的变化,并对比了此条件下自然编码与格雷编码对性能的影响。研究表明,时间抖动和脉冲展宽方差越大系统性能越差,采用格雷编码,可以对时间抖动和脉冲展宽带来的性能损失进行一定的弥补。     

Hermite脉冲超宽带系统在多径信道的性能分析

研究了一种基于Hermite脉冲的超宽带系统在多径信道下的性能。考虑到定时抖动对Rake相关接收的影响,通过Hermite脉冲的相关函数可以计算Rake捕获的信号能量,进而得到接收机的输出信干比。在假设符号间干扰为高斯噪声下,得出系统在多径信道下的理论误比特性能。结果表明,符号间干扰能量对Rake接收机合并路径数目的变化并不敏感;增加合并路径数目可以提高系统的误比特性能;大的定时抖动范围会造成系统性能下降。     

超宽带无线通信与声表面波宽带信号处理技术

介绍了超宽带(UWB)无线通信的技术及特点,与传统窄带无线系统进行了性能比较,指出了超宽带无线通信四大关键技术是:超宽带无线通信脉冲信号的波形设计;超宽带无线通信脉冲信号编码与调制方式;超宽带无线通信信号的检测;超宽带无线通信系统中的同步捕获技术;分析了超宽带尤线通信系统军用的潜在市场,最后阐述了SAW宽带信号处理技术在UWB通信系统中的应用.     

色散管理孤子系统中时间抖动性能的分析

研究了色散管理孤子(DMS)系统中影响时间抖动性能的各个因素。理论分析得出：色散管理(DM)的累积色散、附加累积色散和DM强度是影响时间抖动的重要因素,降低路径平均色散和增大DM强度均能减小时间抖动;附加累积色散对系统时间抖动影响较大,当它等于传输总累积色散量的1／2时,时间抖动最小。数值计算的结果验证了理论分析的正确性,得出的结论对DMS系统中时间抖动性能的改善有一定的帮助。     

基于多啁啾波形的超宽带多址系统的研究

基于啁啾(chirp)脉冲的超宽带系统具有成本低、耗能少和较高的系统增益等优点.本文在啁啾理论的基础上,提出一种针对多用户超宽带系统的新型啁啾波形.通过详尽分析该编码的相关性能,验证了该多址方案的合理性.利用多啁啾波形编码构建的多用户超宽带通信系统,兼具了脉冲超宽带和多带超宽带的优点.本文对基于多啁啾脉冲波形的多用户超宽带通信系统进行了详尽的理论分析,并进行了性能仿真,仿真结果表明:相对于传统脉冲超宽带系统,这种多啁啾波形的多用户系统具有更好的抵抗多址干扰的能力.     

TH-UWB系统中ML信道估计算法研究

跳时超宽带无线通信系统中信道估计的准确度对系统接收性能具有重要影响,首先对超宽带系统收发模型进行介绍,然后对TH-UWB系统中基于训练序列的非结构化最大似然信道估计算法进行分析,最后在超宽带信道模型下对估计算法性能进行仿真.仿真结果表明基于训练序列的非结构化最大似然信道估计算法能够有效估计出信道参数.     

基于Turbo编码的超宽带系统性能分析

为了降低严重的时间弥散影响,提出了一种Turbo信道编码方案引入超宽带系统中,分析和仿真了在不同无线室内环境下基于Turho编码的超宽带系统的误比特率性能。无线室内环境是由IEEE802．15．3a提出的修正的SV信道模型。为了降低迭代译码的复杂度,采用了LOG-MAP算法。仿真结果表明,相比于无编码的系统,具有Turbo编码的超宽带系统在不同无线室内环境下提供了可观的编码增益,随着迭代次数的增加,超宽带系统的性能得到了改善。     

超宽带Rake接收机在密集多径信道下的性能

超宽带信号在室内环境中将经历密集多径传播,产生严重的时间弥敞。采用Rake接收是提高超宽带接收机性能的重要手段。该文针对采用BPSK调制的超宽带系统,推导出密集多径信道下Rake接收机的误码性能计算公式,揭示了Rake接收机性能与多径信道参数以及脉冲波形自相关系数之间的关系。针对典型信道模型和脉冲给出了计算实例。     

The effects of timing jitter and tracking on the performance of impulse radio

Impulse radio (IR) is a promising ultra-wideband technique for tactical military communications. A key feature of time-hopping IR are the very narrow pulses used to convey information. Analysis of such time-hopping schemes under a variety of assumptions have been reported in the literature. However, none of these studies to date consider the effects of timing jitter and tracking on time-hopping in a ultra-wideband (UWB) setting. We consider the effects of timing jitter and tracking on the performance of binary and 4-ary UWB communications. We find that the performance of IR is very sensitive to timing jitter and tracking, at least in part due to the very narrow pulses. We also find that in the presence of timing jitter and tracking, orthogonal 4-ary pulse position modulation (PPM) out performs binary offset PPM at all jitter levels in thermal and pulse noise. Simulation results are presented that quantify the sensitivity of binary and 4-ary IR to timing jitter and tracking error.     

Effect and Compensation of Colored Timing Jitter in Pulsed UWB Systems

Ultra-wideband (UWB) systems impose a stringent requirement on the jitter performance of the system clock. So far, only the effect of white Gaussian timing jitter has been considered in the literature via numerical simulation. However, practical clocks commonly exhibit colored jitter. In this paper, we first investigate the bit error rate (BER) performance of a single-user binary pulse position modulation UWB system subjected to white and colored Gaussian jitter. It is shown that colored jitter degrades BER performance much more than white jitter, and the extent of degradation increases as the jitter bandwidth decreases. Motivated by this result, we then propose a new jitter compensation scheme to improve the BER performance under colored jitters with small jitter bandwidth, in which each information-bearing data symbol is coupled with a pilot symbol. The proposed scheme attempts to track first the jitter for the current pilot symbol by making use of the pulse-template correlation function. This information is then used together with the known clock jitter bandwidth and jitter root-mean-square (RMS) value to detect the current data symbol according to the maximum likelihood criterion. Simulation results show that the algorithm is effective in improving the BER performance for colored jitters with small jitter bandwidth. Lei Huang received the B.Sc. degree from Xi'an Jiaotong University, China, in 1993, the M. Sc. degree from South China University of Technology in 1996, and the Ph.D. degree from Victoria University of Technology (VUT), Australia, in 2003, all in Electrical Engineering. From 1996 to 1999, he was a Lecturer at South China University of Technology. From March 2003 to December 2005, he was with National University of Singapore as a Research Fellow. Since January 2006, he has been working in Panasonic Singapore Laboratories as an R & D Engineer. His research interests focus on physical layer aspects on wireless communication systems, especially CDMA, ultrawideband and millimeter wave communications.     

Analog space-time coding for multiantenna ultra-wideband transmissions

Ultra-wideband (UWB) transmissions have well-documented advantages for low-power, peer-to-peer, and multiple-access communications. Space-time coding (STC), on the other hand, has gained popularity as an effective means of boosting rates and performance. Existing UWB transmitters rely on a single antenna, while ST coders have mostly focused on digital linearly modulated transmissions. In this paper, we develop ST codes for analog (and possibly nonlinearly) modulated multiantenna UWB systems. We show that the resulting analog system is able to collect not only the spatial diversity, but also the multipath diversity inherited by the dense multipath channel, with either coherent or noncoherent reception. Simulations confirm a considerable increase in both bit-error rate performance and immunity against timing jitter, when wedding STC with UWB transmissions.     

The effect of timing jitter on MC-DS-CDMA

In this paper, we consider the effect of timing jitter on the performance of a multicarrier direct-sequence code-division multiple-access system for both uplink and downlink transmission, assuming orthogonal spreading sequences. Theoretical expressions are derived for the performance degradation caused by the timing jitter, in the presence of a multipath channel. Assuming an additive white Gaussian noise channel, perfect power control, and full load, it is shown that the performance degradation for the downlink transmission is independent of the number of subcarriers, of the spreading factor, and of the spectral contents of the jitter at the receiving mobile station, but only depends on the jitter variance. Under the same assumptions, we point out that, if the jitter spectra of all transmitting mobile stations are the same, the degradation on the uplink is the same as the degradation on the downlink.     

A Single-Chip Ultra-Wideband Receiver With Silicon Integrated Antennas for Inter-Chip Wireless Interconnection

A single-chip ultra-wideband (UWB) receiver was developed using 0.18 mum CMOS technology, and inter-chip wireless data communication by integrated antennas was confirmed. Timing pulse and data pulse with on-off keying were alternately sent from a transmitting antenna. Double Gaussian monocycle pulse (GMP) template generators performed detections of timing and data pulses. A single GMP template, whose probability distribution of the pulse repetition cycle is given by Gaussian, showed a random jitter of 4.87 ps. Dual-Dirac model could explain the probability distribution of the cycle of double GMP template. Obtained random jitter and deterministic jitter were 4.6 ps and 14.4 ps, respectively. The receiver successfully recovered 200 Mbps data at the distance of 0.5 mm.     

A new noncoherent UWB impulse radio receiver

This letter analyzes the implementation issues related to coherent receivers for UWB impulse radio with a special emphasis on timing and jitter problems. We propose a new jitter tolerant receiver design that is easy to implement. Analytical BER analysis and simulations verify that the performance of the proposed receiver is comparable to that of a correlator-based receiver that includes jitter. The new design is a promising candidate for low-cost low-power UWB IR receiver implementations.     

UWB-OFDM系统的符号盲同步方法

该文提出一种适合于UWB-OFDM系统的符号盲同步方法。该方法是基于UWB-OFDM符号中的ZP功率出现规律性的分布特性,利用滑动窗能量检测的办法来进行符号同步。研究了高斯信道和UWB信道下的符号同步方法,并详细分析了UWB信道下接收信号的能量分布特性。为了提高同步性能,设计了多滑动窗方法代替双滑动窗方法。计算机仿真分析表明该方法无论在高斯还是UWB信道下都具有优异的性能。     

An analysis of the effect of chip timing jitter in MC-CDMA systems

We investigate the effect of chip synchronization error (or chip timing jitter) in a multicarrier-code division multiple access (MC-CDMA) scheme. The chip timing jitter is modeled by a stationary random process with a known statistic, and the error produced by the jitter is reduced to an additive source of noise. This decomposition is useful because it allows for the use of analytical methods for the computation of the error probability. First, the analysis has been applied to the simple Gaussian channel; afterwards, it has been extended to a multipath fading channel typical of large indoor areas. Use of a semi-analytical approach has been the key factor in obtaining reliable results at moderate computational complexity     

Performance of Impulse-Train-Modulated Ultra-Wideband Systems

The performance of impulse-train-modulated ultra-wideband (UWB) systems for the ideal additive white Gaussian noise channel is analyzed in this letter. The derived formulae are also used to optimize the modulation parameter of a Gaussian monocycle UWB impulse radio