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提出一种通用的多载波频率分集CDMA系统基带发射、瑞利信道以及相关接收的矩阵信号分析模型。通过分析可以看出,多载波频率分集CDMA系统是一种高效的并行调制技术,它使信道和信号之间的卷积关系变成了线性加权关系,有效地抑制了符号间干扰和码间干扰,同时还具有频率分集的优点。对多载波频率分集CDMA系统在BPSK调制下的理论误码性能进行了深入探讨,给出了一种新颖的单用户系统和多用户系统的误码率分析方法。通过高斯近似法和Monte-Carlo模拟方法得到的数值仿真结果表明:瑞利衰落信道下,多载波频率分集CDMA具有良好的抗多径效果:随着用户数的增加,系统性能下降;在无线宽带数据业务传输中的性能大大优于CDMA,应用前景广阔。 相似文献
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在CDMA系统中,采用正交序列可以有效地减小多址干扰的影响。然后,当由于多径衰落的影响使码片间的相对移位增加时,系统中用户扩频序列间的相互正交性减弱,导致性能大大恶化。本文基于新近提出的广义正交序列,分析了采用该序列的多载波直接序列码多分址系统在瑞利衰落信道中的误比特性能。数值结果表明,当扩频序列间相互移位在零相关区之内时,扩频序列仍可保持正交,因而大大提高了系统误比特性能。 相似文献
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无线宽带数据传输中多载波CDMA系统的性能 总被引:1,自引:0,他引:1
在分析同步多载波CDMA系统基带发射、接收模型和多径衰落信道模型的基础上,提出一种新颖的误码率分析方法。对系统在瑞利(Rayleigh)衰落信道中的误码性能进行了理论研究,得到了BPSK调制条件下的系统误码率表达式。数值分析结果表明:多载波CDMA在无线宽带数据传输中性能大大优于CDMA,具有良好的应用前景。 相似文献
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LIU Xiao-ming LIU Yuan-an Wireless Communication Center Beijing University of Posts Telecommunications Beijing P.R. China 《中国邮电高校学报(英文版)》2004,11(Z1)
1 Introduction OrthogonalFrequencyDivisionMultiplexing(OFDM )isaneffectivetransmissionschemetocombatmultipathfading[1 ] .Byinsertingaguardin tervalbetweensymbolblockscalledcyclicprefix ,theInterSymbolInterference (ISI)canbemitigat ed.OFDMwasadoptedasthemodulationschemeforaDigitalAudioBroadcasting(DAB)system[2 ]andADSL (AsymmetryDigitalSubscriberLoop) [3]andwasalsoproposedastheterrestrialHDTVtransportinEurope[4] . OFDMsystemsareverysensitivetocarrierfre quencyoffset,andcarrie… 相似文献
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本文提出了一种在MU-MIMO-OFDM (Multiple-User Multiple-Input-Multiple-Output Orthogonal-Frequency-Division-Multiplexing)上行链路中,联合跟踪残留频偏(Residual Carrier Frequency Offset,RCFO)和信道的算法.本算法采用EM (Expectation Maximization)方法求解该非线性问题,并使用变分推断来近似原来复杂的隐变量的后验概率.在估计RCFO时,考虑了信道估计误差的概率分布,从而降低了信道估计误差对跟踪性能的影响.仿真中,本算法达到了较高的跟踪精度,尤其是在高信噪比时没有误差平台问题. 相似文献
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Yang Yawpo Jong Shu-Li Liu Ji-Chyun Liu Ching-Hwa 《Wireless Personal Communications》2003,27(3):247-265
In this paper, effects of carrier frequency offset on performance of uplink MC-CDMA (Multi-Carrier Code Division Multiple
Access) system in Nakagami fading channel are investigated through the theoretical analysis and Monte Carlo computer simulations.
Both perfect maximal-ratio combining (MRC) and equal gain combining (EGC) receivers are analyzed; the impact of imperfect
channel fading estimation on the performance of MRC is also explored. The performance of MC-CDMA system is also compared with
that of the conventional single-carrier DS-CDMA system. Our results indicate that the performance of MC-CDMA system is sensitive
to even small values of carrier frequency offset and that the performance of MC-CDMA system improves as number of subcarriers
increases. In perfect channel fading estimation, the overall performance of MRC is superior to EGC. However, when imperfect
or inaccurate channel fading estimation exists, which leads to serious performance degradation, EGC becomes superior to MRC.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Orthogonal frequency division multiplexing (OFDM) systems are more sensitive to carrier frequency offset (CFO) compared to
the conventional single carrier systems. CFO destroys the orthogonality among subcarriers, resulting in inter-carrier interference
(ICI) and degrading system performance. To mitigate the effect of the CFO, it has to be estimated and compensated before the
demodulation. The CFO can be divided into an integer part and a fractional part. In this paper, we investigate a maximum-likelihood
estimator (MLE) for estimating the integer part of the CFO in OFDM systems, which requires only one OFDM block as the pilot
symbols. To reduce the computational complexity of the MLE and improve the bandwidth efficiency, a suboptimum estimator (Sub
MLE) is studied. Based on the hypothesis testing method, a threshold Sub MLE (T-Sub MLE) is proposed to further reduce the
computational complexity. The performance analysis of the proposed T-Sub MLE is obtained and the analytical results match
the simulation results well. Numerical results show that the proposed estimators are effective and reliable in both additive
white Gaussian noise (AWGN) and frequency-selective fading channels in OFDM systems.
相似文献
Feng YangEmail: |
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本文提出一种适合于瑞利衰落信道多进制差分相移键控系统相位比较解调的性能分析方法,推导出符号错误率解析表示式,考虑了瑞利衰落、时间选择性衰落和高斯白噪声对体制性能的影响,并针对衰落功率谱为高斯型和矩形分别对二进制、四进制和八进制情形进行了数值计算。 相似文献
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差分跳频中,用户数据对频率选择的约束性比较弱。对此本文提出多序列跳频(MSFH)系统,其发送频率不仅是用户数据的函数,也受同步跳频序列严格约束,因此可以采用窄带接收更好地抑制带外干扰。具体地,数据分组从一簇相互正交的跳频序列中选出一个序列,该序列的当前频率由射频端直接发送,而无需对发送信号进行调制。得到了瑞利衰落信道中,未编码和采用卷积编码-硬/软判决Viterbi译码时MSFH符号误码率性能。计算和仿真表明,在相同编码增益下,MSFH误码率低于常规跳频系统;与差分跳频译码复杂度相当时,MSFH性能亦具有一定优势。 相似文献
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近来无源反向散射通信技术作为绿色物联网的关键技术,引起了广泛的关注。在无源反向散射通信系统中,收发节点与反射节点的振荡器差异、相对运动以及环境变化,导致接收端和发送端存在载波频率偏移(CFO)。CFO对信号检测和系统性能有重要影响,而当前多数无源反向散射通信系统研究忽略了CFO。该文设计了一种适用于频移键控调制(FSK)的CFO快速检测方法,不需要导频就能快速有效检测出CFO是否存在并找出存在的位置。首先,根据信号在CFO存在与否的不同,采用去直流后取模方法对信号进行处理,而后根据处理后的信号的特点,基于累积和(CUSUM)设计快速检测算法对载波频偏出现的位置进行检测,并对理论分析结果进行仿真验证,仿真结果表明取模检测可以有效检测出CFO出现的位置。 相似文献