共查询到19条相似文献,搜索用时 187 毫秒
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一种适合PPM-UWB信号的时移TDT同步捕获算法 总被引:5,自引:0,他引:5
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。 相似文献
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密集多径信道下IR—UWB信号同步捕获方法 总被引:1,自引:0,他引:1
超宽带(UWB)信号的快速同步捕获是UWB通信系统中的关键问题.本文提出一种分步同步捕获方法,首先采用两种次最优的最大似然估计算法进行粗搜索,然后在粗搜索获得的有限范围内利用最大值/阈值检测进行精估计.该方法提高了密集多径信道下极窄脉冲形式UWB信号(IR-UWB)的捕获性能,并有效降低了计算复杂度和处理时间.文中还根据IR-UWB信号接收特点,从捕获能量的角度定义了捕获概率.通过仿真评估了捕获能量对系统性能的影响,并对算法性能和参数选择进行了分析. 相似文献
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超宽带(UWB)通信是目前无线通信研究的热点,其中脉冲无线电(Impulse Radio,IR)技术采用业纳秒脉冲信号作为信息传输的载体,数据传输速率大于100Mbps,具有超宽频谱和极低功率谱密度的优点。在采用IR技术的UWB通信中,脉冲的捕捉和同步是它的核心技术和难点。该文给出了采用基于正交分解进行脉冲同步的方法,相对于传统的使用匹配滤波器进行的定时估计和接收,具有结构简单,实现方便,在室内密集多径信道下和极大的符号间干扰下均能稳定工作的特点。仿真表明,该方法对多径捕获、脉冲重复频率和定时估计都有很好的性能。 相似文献
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本文提出了一种基于多天线辅助估计的UWB(超宽带)快速捕获算法,利用UWB信号的循环平稳特性,将接收信号与它自身延迟一个信息位产生的模板相关,应用最大似然方法就可得到一个粗略的同步时间估计,在充分利用线性天线阵空间分集增益的情况下,这种估计相当准确。在此基础上继续进行精确同步,直到捕获任一符号位的第一帧第一个到达脉冲。文中采用流图法给出了本算法平均捕获时间的闭式解。理论分析和计算机模拟表明,该算法与同等硬件复杂程度和同等捕获精度的其他捕获方法相比可明显地缩短平均捕获时间。 相似文献
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正交Hermite脉冲被提出用于超宽带无线通信。该文提出新方法用于超宽带通信的多用户传输系统。通过同时传输多个正交Hermie脉冲,超宽带多用户传输系统可以获得好的性能特征。该文还提出了正交Hermite脉冲应用于UWB的DS-CDMA系统以同时支持更多的用户通信。 相似文献
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Rshdee Alhakim Kosai Raoof Emmanuel Simeu Youssef Serrestou 《Signal, Image and Video Processing》2013,7(4):741-757
Timing acquisition constitutes a major challenge in realizing ultra-wideband communications. In this paper, we propose the timing with dirty template (TDT) approach as a promising candidate for achieving rapid, accurate and low-complexity acquisition. We describe the dirty template (DT) technique, in order to develop and test timing algorithms in both modes: data-aided (DA) and non-data- aided (NDA) modes. First, we derive the Cramer–Rao lower bound, which is used as a fundamental performance limit for any timing estimator. Next, the TDT acquisition estimator is achieved by using the Maximum Likelihood concept. Then we propose a new method, based on Time-Hoping codes, to improve the performance estimation of the original dirty template algorithms. Simulation shows the estimation error results of the modified method in the DA and NDA modes. It confirms the high performance and fast timing acquisition of DA mode, compared with NDA mode, but with less bandwidth efficiency. 相似文献
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基于PSWF的非正弦时域正交调制信号的同步方法 总被引:2,自引:0,他引:2
该文针对基于PSWF的非正弦时域正交调制信号同步困难的问题,通过分析调制信号的脉冲序列特征,提出了一种基于辅助序列的同步方法。采用Barker码调制0阶基带时限PSWF脉冲设计具有单峰值特性的辅助序列。同步捕获时,先采用滑动相关捕获法将同步大致位置快速定位于一个小的搜索区间,再采用MAX/TC算法在这个小的搜索区间内进行准确捕获并验证正确性。理论推导了AWGN条件下的同步捕获性能,仿真结果表明,该同步方法可行,且在低信噪比条件下具有较好的捕获概率。 相似文献
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Demodulation and tracking with dirty templates for UWB impulse radio: algorithms and performance 总被引:1,自引:0,他引:1
Farahmand S. Xiliang Luo Giannakis G.B. 《Vehicular Technology, IEEE Transactions on》2005,54(5):1595-1608
Major challenges in ultrawideband (UWB) communications include timing acquisition, tracking, and low complexity demodulation. Timing with dirty templates (TDT) is a recently proposed acquisition algorithm with attractive features. Starting with a performance analysis of TDT, this paper goes on to considerably broaden its scope by developing novel tracking loops and detectors by naturally following the TDT operation. Specifically, upper bounds on the mean square error of the blind and data-aided TDT estimators are derived, along with TDT-based demodulators, obviating the need to know the underlying channel and time hopping code. Analytical comparisons reveal that TDT demodulators outperform RAKE with limited number of fingers in the medium-high SNR range. TDT demodulation performance in the presence of timing errors is evaluated and shown to be robust to mistiming. In order to follow timing offset variations, an adaptive loop is also introduced to track the first multipath arrival of each symbol. For a given input disturbance, parameters of the loop are selected to optimize jointly transient and steady state performance. Analytical results are corroborated by simulations. 相似文献
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Joo A. Ney da Silva Marcello L. R. de Campos 《Communications, IEEE Transactions on》2007,55(2):313-322
In this paper, we present a method to obtain a set of orthogonal pulses to be used in pulse-shape modulation (PSM) for ultra-wideband communications. The pulses are built as linear combinations of Hermite functions, which are shown to have unique advantageous features. Mathematical restrictions of orthogonality and spectral efficiency are introduced as guidelines to a fully explained search procedure to find the best set of pulses. Additionally, this procedure is adapted and used to find a single FCC-compliant pulse shape. A quaternary PSM scheme is implemented with orthogonal pulses obtained by the proposed method, and the results of a simulation are shown 相似文献
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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。 相似文献
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The novel pulses, which not only meet the power spectral mask of the Federal Communications Commission (FCC) but also preserve orthonormality at the correlation receiver, have been proposed by Kim for high data rate communications in indoor ultra-wideband (UWB) systems. The proposed multiple orthonormal pulses comply with the FCC spectral mask without additional frequency shifting or bandpass filters, and furthermore, provide enhanced bit-error rate (BER) performance, compared with a well-known Gaussian monocycle and modified Hermite pulses. This paper analyzes the impact of the proposed pulses' properties, such as their auto- and cross-correlations, on the correlation receiver of the UWB system based on the pulse position modulation. The performance of the proposed pulses are compared with different waveforms under various conditions, such as multipath fading, timing mismatch, and multiuser interference. We also discuss a modulation scheme using the multiple orthogonal pulses to achieve the enhancement of data rate and the impact of the correlation characteristics of the proposed waveforms on the BER performance. Simulation results demonstrate the effectiveness of the proposed orthonormal pulses in various conditions, comparing with different waveforms 相似文献
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A Novel UWB Pulse Shape Modulation System 总被引:5,自引:1,他引:4
Ghavami Mohammad Michael Lachlan B. Haruyama Shinichiro Kohno Ryuji 《Wireless Personal Communications》2002,23(1):105-120
In this paper novel modified Hermite polynomial functions for use in impulse radio (ultra-wideband) communications are proposed. With these functions pulse shapes which are orthogonal and have nearly constant pulse width regardless of the pulse order are generated. These properties hold under the effects of differentiation. An M-ary communication system is constructed using these pulse shapes. A Matlab model for generating the pulses is designed and the effect of timing jitter on the performance of the system is investigated by computer simulation. 相似文献
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A new joint frame synchronization and carrier frequency offset estimation scheme in orthogonal frequency division multiplexing (OFDM) systems is proposed in this paper, where both frame synchronization and carrier frequency offset estimation can be performed by using only ONE training symbol. Frame synchronization and carrier frequency offset acquisition are performed simultaneously in the proposed scheme. Reliable frame synchronization is obtained in the proposed scheme even in low SNR. The maximum carrier frequency offset acquisition range of the proposed scheme can be up to one half of the total signal bandwidth. The same training symbol can also be utilized to carrier frequency offset Fine Adjustment, which estimates the remaining carrier frequency offset after acquisition with higher accuracy. The performance comparison of the proposed Fine Adjustment algorithm and Schmidl's algorithm by using computer simulation illustrates and verify the superior performance of the proposed algorithm with regard to estimation accuracy. 相似文献