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,...     

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.     

基于PPM调制的超宽带Rake接收机性能研究

室内环境中超宽带(UWB)信号经过密集多径传播会产生严重的时间弥散,采用Rake接收是提高UWB接收机性能的重要手段.在IEEE802.15.3a工作组推荐的信道模型基础上,采用脉冲位置调制(PPM)方式对超宽带信号在不同信道情况下不同Rake接收机的性能进行了系统的研究,可以在选择Rake接收机时,为综合考虑系统复杂度和性能改善的优化问题提供有价值的参考.     

用户间UWB脉冲相互正交的M状态PPM超宽带系统

UWB(超宽带)系统中各用户通常使用同一种UWB脉冲发送数据,当系统采用PPM(脉位调制)时,由于存在多用户干扰,系统一般为二状态PPM而很少采用M(>2)状态PPM方式,同时为提高接收信噪比,系统一般发送多个UWB脉冲调制1比特数据。该文根据正交函数的特性,提出了一种基于正交UWB脉冲的M状态PPM超宽带系统,系统中每个用户使用的UWB脉冲互不相同,而且用户间的UWB脉冲是相互正交的,在系统实现时隙同步的基础上,系统可完全消除多用户干扰,极大地提高了用户速率。     

用户UWB脉冲相互正交的M状态PPM超宽带系统

UWB(超宽带)系统中各用户通常使用同一种UWB脉冲发送数据,当系统采用PPM(脉位调制)时,由于存在多用户干扰,系统一般为二状态PPM而很少采用M(>2)状态PPM方式,同时为提高接收信噪比,系统一般发送多个UWB脉冲调制1比特数据。该文根据正交函数的特性,提出了一种基于正交UWB脉冲的M状态PPM超宽带系统,系统中每个用户使用的UWB脉冲互不相同,而且用户间的UWB脉冲是相互正交的,在系统实现时隙同步的基础上,系统可完全消除多用户干扰,极大地提高了用户速率。     

一种适合PPM-UWB信号的时移TDT同步捕获算法

指出TDT(timingwithadirtytemplate)盲同步捕获算法只适于PAM调制(脉冲幅度调制)UWB系统,而不能在PPM调制(脉冲相位调制)UWB系统中应用。提出了一种TS-TDT(time-shift-TDT)盲同步捕获算法,解决了PPM调制UWB系统快速同步捕获问题。该算法通过两条相关支路分别计算接收信号的延迟互相关值而获得同步信息,无需训练序列。理论分析和仿真实验结果表明,该算法结构简单,同步精度灵活可变,性能良好。     

超宽带系统的调制技术

目前一种新的无线通信技术引起了人们的广泛关注,这就是所谓的超宽带(UWB,Ultra WideBand)技术,它被认为是未来五年电信热门技术之一。本文主要介绍了UWB信号的各种调制技术,包括数据调制和多址调制,其中重点介绍了PPM(Pulse Position Modulation,脉冲位置调制)及TH-PPM(Time-Hopping PPM,跳时PPM),最后简要分析比较了IEEE 802．15．3a标准的两大提案——DS-UWB和MB-OFDM。     

基于FPGA的UWB雷达PPM调制解调系统

超宽带UWB无线通信技术是一种基于直接发射窄脉冲的新技术,因其具有低功耗、良好的抗干扰和抗多径能力、穿透性能好等特点,特别适用于隐藏活动目标检测和近距离数据传输。用于检测隐藏活动目标的超宽带雷达就是基于基带无载波极窄脉冲的,有着广阔的应用前景。对比超宽带的多种调制解调方式选取了脉冲位置调制。介绍了使用Verilog语言在FPGA上实现PPM调制解调器,实现了UWB雷达发送窄脉冲进行基带调制。     

在室内通信环境下UWB信号设计及性能分析

采用的脉冲波形在满足联邦通信委员会(FCC)发射要求的基础上,提出了在室内通信环境下,经过脉冲位置调制(PPM)的UWB信号延迟参数的优化设计方法,相对于传统的方法,性能有明显的提升。同时结合信号的数学模型,对信号的误码性能进行了分析与比较,这对于UWB系统在实际系统中的使用有很好的指导意义。     

各用户使用不同正交函数的超宽带系统

超宽带(UWB:Ultra Wide Band)系统中各用户通常使用同一种UWB脉冲发送数据,根据Hermite函数的正交特性,提出了一种基于正交UWB脉冲的TH-SS PPM超宽带系统。系统中每个用户使用不同的修正Hermite函数作为UWB脉冲,用户间的UWB脉冲是相互正交的。该系统的多用户干扰小于各用户使用同一种UWB脉冲的TH-SS PPM超宽带系统,提高了系统的误码率性能,使系统具有更低的误码率。     

Signal design for noncoherent PPM modulation with applications to UWB communications

By deriving the probability of error of a binary pulse-position modulated (PPM), ultra wide-band (UWB) impulse-radio system under noncoherent detection, it is shown that the optima! value for time shift parameter /spl delta/ for PPM is fundamentally different from that for coherent reception. In particular, the optimal choice of /spl delta/ is one that results in zero correlation between the two waveforms used in PPM modulation. By examining the performance sensitivity around possible optimal /spl delta/ solutions for a commonly used UWB monopulse, we also show that it is still possible to employ /spl delta/相似文献   

PPM技术在UWB通信系统中的应用

UWB（Ultra Wide-Band）无线通信技术是一种基于直接发射窄脉冲的新技术,因其具有低功耗、良好的抗干扰和抗多径能力、穿透性能好等特点,特别适用于隐藏动目标检测和近距离数据传输,具有广泛的应用前景。对比超宽带多种调制解调方式,选取了脉冲位置调制。介绍了使用Verilog语言,在FPGA上实现PPM（Pulse Position Modulation）调制解调器,实现了对UWB窄脉冲的基带调制。     

Performance of ultra-wideband communications with suboptimal receivers in multipath channels

The performance of a single-user ultra-wideband (UWB) communication system employing binary block-coded pulse-position modulation (PPM) and suboptimal receivers in multipath channels is considered. The receivers examined include a RAKE receiver with various diversity combining schemes and an autocorrelation receiver, which is used in conjunction with transmitted reference (TR) signaling. A general framework is provided for deriving the performance of these receivers in multipath channels corrupted by additive white Gaussian noise (AWGN). By employing previous measurements of indoor UWB channels, we obtain numerical results for several cases which illustrate the tradeoff between performance and receiver complexity.     

一种室内信道下改善UWB图像传输系统性能的方法

文章在主要分析了室内衰落信道模型及TH-PPM（跳时脉冲位置调制）UWB系统模型的基础上,提出了一种用于在已知室内衰落信道的情况下提高UWB图像传输系统通信性能的方法,即将发送图像数据分为主要数据和次要数据,在信道良好的情况下,传输主要数据;在信道较差的情况下,传输次要数据。在不损害传输速率的情况下提高UWB图像传榆系统的通信性能。系统仿真的结果显示,在SNR为5dB时,选择传输的接收图像的PSNR比未做选择传输的接收图像改进约7dB。     

A decision tree‐based NLOS detection method for the UWB indoor location tracking accuracy improvement

Among existing wireless technologies, ultra‐wideband (UWB) is the most promising solution for indoor location tracking. UWB has a great multipath fading immunity; however, great multipath resolvability alone does not eliminate the effect of non‐line‐of‐sight (NLOS) and multipath propagation. NLOS and multipath propagation in indoor environments can easily produce meters of UWB ranging error. This condition gives an enormous impact on the accuracy of indoor location tracking data. To address this problem, we propose an NLOS detection method using recursive decision tree learning. Using the UWB channel quality indicators information, we develop our model with the Gini index and altered priors splitting criteria. We then validate the constructed model using the 10‐fold cross‐validation method. Our experiment shows that the constructed model has correctly detected 90% of both line‐of‐sight (LOS) and NLOS cases on the seven different indoor environments. The result of this work can be used for the UWB indoor location tracking accuracy improvement.     

Performance of a Binary PPM Ultra-Wideband Communication System with Direct Sequence Spreading for Multiple Access

In this paper, we present an analysis of the BER performance of an ultra-wideband (UWB) system with pulse position modulation (PPM) for data modulation and direct sequence (DS) spreading for multiple access over indoor lognormal fading channels. A rake receiver is used to combine a subset of the resolvable multipath components using the maximal ratio combining technique. Inter-path and multiple-access interferences are modeled and incorporated into the bit-error-rate expressions. The analytical and simulation results allow one to quantify many critical aspects of a DS-PPM UWB system such as the gain of the optimally spaced signaling scheme over the orthogonal signaling scheme, the potential error floor given a specific channel multipath delay spread and the number of interfering users, tolerance of the system to timing jitter, and impact of user codes.     

Multiuser detection of time-hopping PPM UWB system in the presence of multipath fading

Ultra-wideband (UWB) impulse radio (IR) systems are currently being considered for several applications due to their attractive features that include low-power carrierless and ample multipath diversity. Among the various modulation and multiple-access schemes, time-hopping (TH) pulse position modulation (PPM) is a popular technique in application. Most past works rely on strict power control and perform single-user detection (matched filtering) on the desired signal. This paper aims to apply multiuser detection techniques in binary PPM (BPPM) UWB IR multiple-access systems. Moreover, we consider frequency-selective multipath fading channels to account for the wireless cellular environment. A class of linear multiuser detectors (LMDs) is applied to extract the information bits while eliminating multiuser interference (MUI) in the presence of multipath fading. Simulation results are provided to compare the performance of different LMDs.     

PPM调制下的Chirp扩频超宽带无线通信系统

鉴于上行线性调频与下行线性调频信号在实际中的交叠和非完全正交而导致的互相关干扰,设计了基于脉冲位置调制的线性调频扩频超宽带无线通信系统。同时,对提出的系统在AWGN信道和其他的多径信道下做了仿真,并与正交二进制键控线性调频超宽带系统做了比较。仿真结果显示所设计的系统通过引入脉冲位置调制和声表面波Rake接收机,在IEEE802.15.4a制定的室内外信道环境下,有着稳健的抗多径干扰和阴影衰落的能力,并且在非视距环境下性能要远优于正交二进制键控线性调频超宽带系统。