单载波块传输系统及其均衡技术的研究

近年来，多载波OFDM系统因其均衡简单且能有效地抗多径干扰而受到广泛地研究。随着研究的深入，发现单载波系统也有类似的均衡办法与优点。介绍一种系统，称为单载波块传输系统，并研究了其各种均衡办法，比较了它们的性能与复杂度。当采用信道矩阵扩展技术或重叠相加技术，并采用最小均方误差均衡时，该系统有着良好的抗多径性能和较低的计算复杂度。     

基于DTTB单载波频域均衡技术研究

分析了中国数字电视地面广播标准中的系统帧结构,并根据信号帧头的循环特性,提出了一种性能较好的信道估计 算法;分析了传统的单载波均衡算法的优缺点,提出了一种联合频域均衡和时域判决反馈的均衡技术;最后对U1信道进行仿 真,并对仿真结果进行分析总结.     

一种单载波频域均衡方案及性能仿真

参考IEEE802.16标准建议的单载波频域均衡的方法,提出了一种适合时变深衰落信道的单载波均衡方案。该方案采用了基于分集合并的判决反馈均衡结构,不但具有较好的抗符号间干扰能力,而且可以显著改善无线通信系统的抗衰落性能。对该方案的抗符号间干扰能力进行了软件仿真。     

正交复用QAM系统的定时和载波相位跟踪新算法

在数字信号传输系统中，正交复用ＱＡＭ（ＯＭＱＡＭ）是目前最有效的一种抗信道失真传输技术，但它对系统的定时偏移和载波相位误差非常敏感。本文基于高阶累积量技术，导出了一种新的ＯＭＱＡＭ系统定时和载波相位的跟踪算法。计算机仿真证实了这一理论分析结果，并同原有的Ｈｉｒｏｓａｋｉ算法做了比较     

一种实现非等带宽多载波调制的新方法

传统的多载波调制都是采用对传输信道进行等带宽划分的方式。为了更好地适应信道传输特性，一个很有应用前景的发展方向是采用非等带宽划分信道的多载波调制方式。本文提出了一种利用正交小波包变换实现的非等带宽划分信道的多载波调制方法。理论分析和实验结果表明，这种方法对于提高信道的传输性能有很大的潜力。     

跳频/多载波频率分集/扩频多址无线通信系统的研究

本文提出了一种跳频／多载波频率分集／扩频多址（ＦＨ／ＭＣＦＤ／ＳＳＭＡ）无线通信系统,给出了ＦＨ／ＭＣＦＤ／ＳＳＭＡ系统的发送和接收模型,对判惟变量统计特性进行了分析,然后对峰窝系统反向链路在理想定时和信道估计条件下用户平均接收误码率进行了仿真。结果表明,ＦＨ／ＭＣＦＤ／ＳＳＭＡ蜂窝通信系统具有较好的抗多径衰落能力,同单载波ＦＨ／ＳＳＭＡ系统相比其误码性能和频谱效率有显著改善。     

无线信道中的单载波频域均衡技术

本文介绍了时域均衡的单载波系统、多载波正交频分复用系统和频域均衡的单载波系统。频域均衡单载波系统复杂度和性能与多载波系统相当，可以与多载波系统共存，已被IEEE 802．16建议在宽带无线接入中采用。     

基于迫零均衡的单载波分块传输系统的误符号率分析

分析了若干独立非负随机变量调和平均值的概率密度函数在零点附近的变化特性.在此基础上,分析了单载波分块传输系统中采用频域迫零均衡时的误符号率性能,给出了高信噪比时采用MPSK调制和MQAM调制时的误符号率的闭合表达式,并通过计算机仿真验证了理论分析结果.理论分析和数值仿真结果表明在瑞利衰落信道下,采用迫零均衡的SCBT系统在高信噪比时的平均误符号率与信道多径数目无关.     

基于载波调制的光纤通信网络传输质量提升方法

光纤通信网络传输信道畸变，影响了光纤通信网络传输质量，为此，提出了基于载波调制的光纤通信网络传输质量提升方法。构建光纤通信网络传输的传输大数据采集和特征分析模型，结合模糊聚类方法进行光纤通信网络输出信道的扩频处理，采用载波调制方法进行光纤通信网络的波特均衡控制，抑制光纤通信网络传输信道畸变，优化光纤通信网络传输质量。结果表明，采用该方法进行光纤通信网络传输精度可达96.2%,网络信道均衡性较好，输出误码率较低，在16 dB和13 dB时可达最低误码率，有效提升了光纤通信网络传输质量。     

面向ASIC设计的单载波超宽带信道均衡研究

单载波超宽带通信系统的均衡在芯片实现中面临高吞吐率、高性能和低复杂度三方面问题。该文首先比较了最大似然均衡（MLSE）、线性均衡（LE）、判决反馈均衡（DFE）及单载波频域均衡（SC-FDE）在性能、复杂度及高速化实现上的优缺点,并综合考虑SC-UWB系统这一特殊的应用场景最终选择了DFE。然后针对DFE算法中的三个关键参数——前馈阶数Nf,反馈阶数Nb及判决延迟D,提出了一种实际系统中有效且实用的参数优化设计策略,最后仿真证明了优化策略的实用性和有效性。     

Bandwidth‐efficient turbo coding over Rayleigh fading channels

Introduced in 1993, turbo codes can achieve high coding gains close to the Shannon limit. In order to design power and bandwidth‐efficient coding schemes, several approaches have been introduced to combine high coding rate turbo codes with multilevel modulations. The coding systems thus obtained have been shown to display near‐capacity performance over additive white Gaussian noise (AWGN) channels. For communications over fading channels requiring large coding gain and high bandwidth efficiency, it is also interesting to study bit error rate (BER) performance of turbo codes combined with high order rectangular QAM modulations. To this end, we investigate, in this paper, error performance of several bandwidth‐efficient schemes designed using the bit‐interleaved coded modulation approach that has proven potentially very attractive when powerful codes, such as turbo codes, are employed. The structure of these coding schemes, termed ‘bit‐interleaved turbo‐coded modulations’ (BITCMs), is presented in a detailed manner and their BER performance is investigated for spectral efficiencies ranging from 2 to 7 bit/s/Hz. Computer simulation results indicate that BITCMs can achieve near‐capacity performance over Rayleigh fading channels, for all spectral efficiencies considered throughout the paper. It is also shown that the combination of turbo coding and rectangular QAM modulation with Gray mapping constitutes inherently a very powerful association, since coding and modulation functions are both optimized for operation in the same signal‐to‐noise ratio region. This means that no BER improvement is obtainable by employing any other signal constellation in place of the rectangular ones. Finally, the actual influence of the interleaving and mapping functions on error performance of BITCM schemes is discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance of a Modified Multicarrier Direct Sequence CDMA System

In this paper, we present an improved multicarrier direct sequence (DS) code division multiple access (CDMA) scheme by modifying the system originally proposed by Kondo and Milstein [13]. In this modified system, different spreading sequences multiplied by a data sequence modulate different carriers. This is to prevent the multiple access capability from reducing when the fading characteristics of different carrier frequencies are highly correlated. We have derived a formula which determines the mean values of the relative received signal strength in a single carrier DS CDMA rake system and in a multicarrier DS-CDMA system. We present results on the comparison of the bit error rate (BER) performance of the two systems including the effect of correlation between fading characteristics of different frequencies under various multipath fading conditions. The results indicate that with 50 users the modified multicarrier DS CDMA system can achieve an uncoded irreducible BER of 1.7 × 10^??3 with an average received signal-to-noise ratio per bit of 10 dB, which is better than 3.0 × 10^??3 achieved by the single carrier DS CDMA rake system, and also show that if multicarrier CDMA system is used with respect to single carrier CDMA system, the SNR gain is up to 4.5 dB for the uncode BER of 10^??3 being achieved.     

正交多载波降噪差分混沌键控通信系统

为解决多载波差分混沌移位键控(MC-DCSK)系统传输速率低和误码性能差的缺点,该文提出一种正交多载波降噪差分混沌移位键控(QMC-NR-DCSK)系统。在发送端,预定义载波用于发送参考信号,剩余M-1个不同中心频率的载波及其经正交调制技术后得到的频率相同但相位正交的载波都用于传输信息信号,此外,通过进一步引入Hilbert变换,将系统的频带利用率和传输速率提升为MC-DCSK系统的4倍。在接收端引入滑动平均滤波器的降噪操作降低了噪声的方差,从而改善了系统误码性能。推导了QMC-NR-DCSK系统在加性高斯白噪声(AWGN)信道和多径瑞利衰落(RFC)信道下的比特误码率公式并进行了仿真。仿真结果和理论分析表明：QMC-NR-DCSK系统能有效提升传输速率、带宽效率和误码性能,为该系统应用于多载波无线通信提供理论参考。     

Cyclic prefixed single carrier and multicarrier transmission: bit rate comparison

We consider cyclic prefixed single carrier and adaptive multicarrier transmission over a frequency selective channel. We compare the achievable bit rate for a target bit error rate. We analytically prove that the bit rate achieved with multicarrier transmission with adaptive modulation is always higher than that obtained with single carrier transmission when a one-tap frequency domain equalizer is used. We also show that the same adaptively loaded multicarrier scheme reaches the performance of single carrier transmission with a block decision-feedback equalizer.     

汉明码在多载波CDMA系统中的应用

本文讨论了GMC-CDMA技术。GMC-CDMA提供了全数字、统一的结构，包含了单载波和多载波CDMA系统。然后，本文用信道编码对GMC-CDMA技术改进，采用在GMC-CDMA系统前先进行蝙码采确保低误码率。仿真结果会表明：经过编码后的系统能取得更低的误码率。图像在编码的GMC-CDMA和未编码的GMC—CDMA两个系统中的不同传输效果进一步验证了这一结论。     

The multitone channel

The maximum bit rate of multitone QAM (quadrature amplitude modulation) over a general linear channel is found. First, the overall bit rate for an AWGN channel with a two-level transfer function is maximized, using a multitone QAM system. The power distribution between the tones and the number of bits/symbol per tone is optimized for a given symbol error rate. Extending these results to the general channel, it is shown that the optimum power division for multitone signals is similar to the water-pouring solution of information theory. Furthermore, multitone QAM performance is about 9 dB worse than the channel capacity, independent of the channel characteristics. The multitone results throughout are compared to those of an equivalent single-tone linearly equalized system. The comparison shows that the multitone system is useful for some channels, e.g. those with deep nulls in the transfer function. The maximum bit error rate over a twisted-pair channel which is performance dominated by near-end crosstalk (NEXT) is also found     

二维扩频系统中时频码片级差分检测的性能分析

时变频率选择性衰落信道中,针对二维扩频系统提出了一种时频码片级差分检测方法,并进行了误码率分析,同时进行了仿真验证.分析和仿真结果表明,时频码片级差分检测同时具有抵抗信道频率选择性和时间选择性衰落的能力,在选择性衰落信道中的性能优于平坦衰落信道中的性能.通过性能对比发现,时频码片级差分检测相对多载波扩频码片级差分检测能够更加有效地降低了载波间干扰对系统性能的影响.     

A sensitivity matched multicarrier modulation

We develop a multicarrier modulation scheme for transmission of compressed data. The energy allocation among subcarriers is optimized by minimizing a modified symbol error function in either AWGN or Rayleigh fading channels. It is observed that our sensitivity matched multicarrier modulation significantly outperforms the conventional multi carrier modulation. The performance gain in Rayleigh fading channels varies from 0.58 to 3.26 dB depending upon the relative sensitivity of bit groups associated with subchannels     

Trellis code‐aided high‐rate M‐QAM space‐time labeling diversity using a unitary expansion

In this paper, we present a high‐rate M‐ary quadrature amplitude modulation (M‐QAM) space‐time labeling diversity (STLD) system that retains the robust error performance of the conventional STLD system. The high‐rate STLD is realised by expanding the conventional STLD via a unitary matrix transformation. Robust error performance of the high‐rate STLD is achieved by incorporating trellis coding into the mapping of additional bits to high‐rate codes. The comparison of spectral efficiency between the proposed trellis code‐aided high‐rate STLD (TC‐STLD) and the conventional STLD shows that TC‐STLD with 16‐QAM and 64‐QAM respectively achieves a 12.5% and 8.3% increase in spectral efficiency for each additional bit sent with the transmitted high‐rate codeword. Moreover, we derive an analytical bound to predict the average bit error probability performance of TC‐STLD over Rayleigh frequency‐flat fading channels. The analytical results are verified by Monte Carlo simulation results, which show that the derived analytical bounds closely predict the average bit error probability performance at high signal‐to‐noise ratios (SNR). Simulation results also show that TC‐STLD with 1 additional bit achieves an insignificant SNR gain of approximately 0.05 dB over the conventional STLD, while TC‐STLD with 2 additional bits achieves an SNR gain of approximately 0.12 dB.     

Complexity reduction and performance improvement of a decisionfeedback equalizer for 16QAM in land mobile communications

This paper proposes a complexity-reduced decision feedback equalizer (DFE) for 16-ary quadrature amplitude modulation (16QAM) using tap gain interpolation, bi-directional equalizing (BDE) and space diversity combining (SDC) to achieve high spectral efficiency and high quality data transmission over frequency-selective fading channels in land mobile communications. To reduce the amount of computation required for BDE and SDC, we propose a tap gain interpolation scheme and pre-decision schemes for both processes. Computer simulation of a (16QAM/TDMA system) confirms that the proposed scheme improves frequency-selective fading compensation performance by 6 dB or more while using only 27% of the computation of conventional single branch DFE receivers