运用误差反馈的判决反馈均衡器的性能分析

判决反馈均衡器（Decision Feedback Equalizer，DFE）能补偿具有严重符号间干扰（Inter Symbol Interference，ISI）的信道，且不存在线性均衡器增强噪声的影响。而在其基础上改进的运用误差反馈的DFE，可利用误差反馈滤波器来减少传统DFE中存在的误差信号的相关性，同时其硬件实现的复杂度没有明显提高。理论分析和仿真表明，这种方法比传统的DFE更有效，特别是针对信道有严重符号间干扰的情况。     

40Gb/s光纤通信系统中自适应判决反馈均衡器的补偿性能

数值仿真了40Gbit/s 非归零码(NRZ)光纤通信系统中,基于最小均方差算法的非线性自适应判决反馈均衡器对系统传输损伤的补偿性能.仿真结果表明,对于单信道40 Gbit/s NRZ系统,在同时考虑色散和自相位调制情况下,自适应判决反馈均衡器的引入可以使系统色散容限(1 dB眼图张开度代价)得到明显改善.在信号丢失率为10-3条件下,PMD容限由补偿前的0.17/单位比特周期,可提高到补偿后的0.22/单位比特周期.     

一种提高部分反馈预编码MIMO系统安全性能方案

MIMO(Mutiple-In Mutiple-Out,多输入多输出)技术是无线移动通信领域智能天线技术的重大突破。无线通信的广播特性容易引起信息泄露,开展研究提高无线通信网络安全性能的课题十分必要。目前,MIMO系统中的预编码技术已成为无线通信领域的研究热点。本文将介绍一种加密技术控制下通过旋转码本提高预编码系统安全性能的方案。通过仿真,验证了该方案可以使无线通信可靠性接近1,并且该方案的设计思想可以推广到其他预编码系统中。     

改善判决反馈均衡器性能的一种新方法

判决反馈均衡器是一种算法复杂度较低、性能也较好、并在实际中得到广泛应用的均衡器。它的一个内在的缺陷是错误判决结果反馈所引起的性能损失。利用判决反馈均衡器中前向滤波器输出中的信息,提出了一种改善判决反馈均衡器性能的方法,并给出改进后判决反馈均衡器的结构和实现方法。仿真结果证明了该方法的有效性。     

有限反馈分布式预编码协作通信系统及性能分析

该文提出了一种有限反馈条件下的分布式预编码非正交协作分集系统(DP-NOCD)。该系统利用目的端的多天线特性,将中继信号进行预处理后在共享的信道资源上发送,从而同时提高了传统正交协作分集(OCD)系统的频谱效率和可靠性。利用译码转发(DF)中继信道模型,并将虚拟的两输入多输出信道在矢量空间分解为两个正交子信道,提出了一种系统误码率最小准则下的预编码方法。该方法能改善系统误码性能,且反馈量低。仿真结果表明,在理想协作场景下,与非协作系统和无干扰的OCD系统相比,DP-NOCD系统在误码率为10-3时分别可获得5～6.2 dB和1～1.2 dB的增益。     

The Performance of BICM With a Single Decision Feedback for the AWGN Channel

This paper studies the performance of bit interleaved coded modulation (BICM) with a single decision feedback. The separation of demodulation and decoding in BICM inevitably reduces the channel's capacity. Altering the conventional bit mapping in BICM and allowing a single decision feedback greatly reduces the capacity loss. The extra complexity introduced by the single decision feedback appears well justified for dense constellations.     

非理想信道信息下认知中继系统中断概率研究

本文针对存在信道估计误差的情况,分析了非理想信道状态信息下认知中继系统的性能.建立了非理想信道状态信息下认知中继系统的数学模型,推导出了非理想信道状态信息下认知中继系统中断概率的表达式.理论分析表明在非理想信道状态信息下认知中继系统的性能较理想状态有所下降,但更符合实际情况.同时数值仿真结果验证了理论分析的正确性.     

一种FTN系统下预测型判决反馈均衡器

超Nyquist码元速率(FTN)理论的出现为提高通信系统数据传输速率奠定了基础。但是,FTN是以引入码间串扰(ISI)为代价的。这给接收端信号检测工作增加了难度。目前已有学者提出了基于线性频域均衡器(FDE)的FTN接收方案。但是FDE在设计抽头系数时没有考虑接收滤波器对信道噪声的影响,而且FDE输出的结果仍然存在残余的ISI,因此性能略差。针对上述问题,将接收滤波器对信道噪声的影响考虑进均衡器设计中,并进一步提出了基于预测型判决反馈均衡器(NPDFE)的FTN接收方案,提高了接收性能。仿真结果表明:在BER=10-4条件下,当ρ=0.8时,NPDFE以提升一倍复杂度的代价使得所需的SNR比FDE减少约5 d B。     

Noise Performance of a Cross-Product AFC with Decision Feedback for DPSK Signals

This paper presents a derivation of the noise performance of the cross-product AFC with decision feedback (CPAFCDF). This is an AFC loop configured for use with differentially phase-shift-keyed (DPSK) signals and gives excellent performance in noise.     

带有天线阵列的多载波DS-CDMA系统的性能分析

本论文提出了一个多载波DS-CDMA的下行空时接收机结构并且分析了它的性能，对于每一个载波，首先进行最优波束形成。再经过传统的RAKE合并，并比较了多天线接收机和单天线的接收机的性能。仿真结果表明，使用天线阵列，多径干扰和多用户干扰可以被有效的抑制，因而其系统容量远远高于单天线系统。     

Performance Analysis of a Memory ARQ Scheme with Soft Decision Detectors

An automatic repeat-request (ARQ) scheme with memory and soft error detectors has been recently proposed by Benelli. Its performance was studied mainly through computer simulation. In this paper, a generalized version of this ARQ scheme is examined. The selection of certain thresholds and weights to minimize the bit error rate in systems using a fixed number of packet repeats is considered. Finally, the evaluation of the average number of transmissions per packet in systems in which negatively acknowledged packets are retransmitted until successfully received is described.     

室内可见光通信中的线性均衡与判决反馈均衡

信道均衡是光通信的关键技术之一。信道均衡能有效地克服信息传输中的多径干扰和消除码间串扰,适合于数据传输。本文针对室内可见光通信系统中由信道失真引起的严重的码间串扰（ISI）情况,研究迫零均衡（ZFE）、最小均方误差（MMSE）均衡、判决反馈均衡（DFE）3种均衡技术,并利用计算机仿真对3种均衡技术的性能进行评估。仿真结果表明,判决反馈均衡器具有明显的优越性。     

OFDM-FDMA Scheme for the Uplink of a Mobile Communication System

The Orthogonal Frequency Division Multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA, FDMA and CDMA approaches with the OFDM modulation procedure which is particularly important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting subcarrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM transmission signal. A specific OFDM-FDMA uplink procedure is proposed and will be designed in this paper which can be seen as a combination of a specific subcarrier spreading scheme and subcarrier selection process. The resulting transmit signal consists of a periodic extension and multiple repetition of all modulation symbols and leads therefore to an extremely low computation complexity in the transmitter. Furthermore, the transmit signal shows simultaneously a constant envelope to avoid any non-linear effects in the amplification process. This uplink scheme can be considered as a trade off between low computation complexity and system performance. Prof. Hermann Rohling is with the Technical University Hamburg-Harburg, Germany where he has developed an international reputation in the field of OFDM transmission techniques. Previously Prof. Rohling was with the AEG Research Institute, Ulm as a researcher working in the area of digital signal processing for radar and communications applications. His research interests have included Wideband Mobile Communications especially based on Multicarrier Transmission Techniques (OFDM) for future broadband systems (4G), signal theory, digital radar signal processing, detection, estimation and differential GPS for high precision navigation. Prof. Rohling is a member of Informationstechnische Gesellschaft (ITG), German Institute of Navigation (DGON) and a senior member of IEEE. He is chairman of the August 2005 International OFDM Workshop (InOWo 2005) in Hamburg, Germany. Martin Stemick received the Dipl.-Ing. degree in electrical engineering from the Technical University Hamburg Harburg (TUHH), Germany in 2004. Currently, he is a Ph. D. student and belongs to the scientific staff of the Department of Telecommunications, TUHH, Hamburg, Germany. His research interests include wireless OFDM-systems, with a current emphasis on resource allocation and equalization techniques.     

Application of Passband Decision Feedback Equalization in Two-Dimensional Data Communication Systems

We describe and experimentally evaluate a receiver structure for two-dimensional data communication systems based on passband decision feedback equalization and data-directed carrier recovery. The forward and feedback tap coefficients and the demodulator's carrier phase angle are adjusted adaptively; the carrier recovery and demodulation operation, as in the case of a linear equalization receiver, can compensate for rather severe frequency offset and phase jitter. Experimental results are reported of simulations of the receiver on voiceband telephone channels.     

On Noise Immunity of Feedback Communication Systems

This paper compares the noise immunities of feedback communication systems for two particular types of systems noise: Gaussian white noise, which is typical of radio and telephone communication, and Poisson-distributed noise, which is typical of laser communication. The comparison shows that as the error probability requirement is made more stringent, the use of feedback will save commensurately more energy in both cases.     

非正弦短波通信方案及性能分析

为了提高短波通信容量和数据传输速率,缓减短波信道拥挤状况,提出了基于椭圆球面波的非正弦短波通信方案.该方案利用快速设计方法设计椭圆球面波脉冲信号,利用新方法构建椭圆球面波时域正交脉冲集,利用基于椭圆球面波的非正弦调制方法调制发送数据,利用基于椭圆球面波的非正弦相关解调方法解调发送数据.对基于椭圆球面波的非正弦调制解调原...     

The New-Word Policy and Decision Feedback in Loop Data Communication Networks

The new-word policy with decision feedback is shown to improve the efficiency of loop data communication with noisy links to the extent that the average number of loop transmissions per new word increases only linearly with the number of identically noisy links. This compares to an exponential increase in more conventional acknowledge-or-retransmit systems. Also, in the (almost) noiseless case, a greater number of word transfers per loop transmission can be achieved.     

“大数判决”译码在移动信道中的抗干扰性能研究

本文讨论了实现简单的“大数判决”和“大数决加小纠错”两种译码方式，并给出计算机模拟结果，将两种情况下的结果与交错ＢＣＨ性能进行比较，选择较优方式。     

Performance of a Biphase Bandpass Communication System

A binary bandpass communications system is considered, in which the ratio of bandwidth to intermediate frequency (IF) is not necessarily small. Closed-form expressions are given in the case when the receiver (IF) filter hasNdistinct poles. Explicit results, namely probabilities of error, are computed when the filter is a bandpass Butterworth filter. The effect ofk = f_{0}/f_{r}(ratio of half filter bandwidth to IF),f_{0}T(product of half filter bandwidth and bit duration),N, phase and time jitter on probability of error, is investigated.     

On Mean-Square Decision Feedback Equalization and Timing Phase

We analyze the effect of timing phase on the performance of digital data receivers which employ decision feedback equalization. It has long been conjectured, and verified by computer simulations, that decision feedback equalizers are considerably less sensitive to the choice of timing phase than are conventional transversal linear equalizers. We develop the theoretical machinery which provides a rationale for these observations. It follows from our results that for typical operating conditions a 1-2 dB penalty can be incurred by choosing a bad timing phase in decision feedback, while the penalty can be an order of magnitude greater than this (in dB) in conventional linear equalizers.