共查询到18条相似文献,搜索用时 109 毫秒
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针对对流层散射信号的时域衰落特点给出了一种适用于单天线、单发通道和单收通道轻便散射站的新型信号时间分集方法,即将待发送信息符号按等时间间隔多次延迟后重组为一个新的发送序列并共享带宽发出,在接收端对各冗余发送信息进行合并从而获得分集增益。分析了该体制的扩谱隐频率分集作用以及与各种前向纠错编码方法的兼容特性。实测结果表明,在平坦衰落与频率选择性衰落信道中信号的平滑能力均与传统的多天线空间分集体制相当。 相似文献
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在使用2付发射天线、2付接收天线和2个发射频率的传统散射通信系统基础上,提出了一种应用于单载波频域均衡(SC-FDE)散射通信系统的多输入多输出(MIMO)技术方案,可以在保证4重分集的情况下提供2倍的数据传输速率。提出的MIMO技术方案只需在发射端增加2部发射机,不需改变接收机的射频支路结构,具有实现简单的优点。仿真表明,提出的MIMO技术方案在无信道编译码时的误比特率(BER)性能比相应的传统分集系统性能恶化约1.9dB,在进行(64,57)(64,57)Turbo乘积码编译码时的性能恶化只有1.6dB,因此,与使用单独的2套传统分集系统提供2倍的数据传输速率相比,分别具有1.1dB和1.4dB的功率增益,而且具有体积小、成本低的优点。 相似文献
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在无线通信网络中,信号在传输过程中出现衰落和损耗的现象一直都是广受关注的问题.空时频发射分集技术的应用,可以提高通信网络的质量,保证传输信道的稳定性,降低接收设备的复杂度,在无线通信网络中得到了广泛的应用.文章对发射分集技术的特点及基础原理进行了阐述,对空时频编码技术进行了分析,通过仿真软件对实际情况进行模拟,提出了基于空时频发射分集技术的设计方案. 相似文献
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由于对流层散射信道存在严重的衰落现象,故而传统的锁相环机制在散射通信中往往难以奏效。针对此问题,提出了基于提载滤波器幅频特性的校频技术和基于CORDIC算法的校频技术,详细阐述了这2种技术的工作原理及具体实现方案,并对这2种校频技术分别进行了评估,给出了基于CORDIC算法的校频技术在信道模拟仪上的测试数据和结论。 相似文献
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针对发射分集下的OFDM系统,提出了一种子载波频域均衡接收机设计方法。在保持子载波数恒定的条件下减少循环前缀的长度,并推导出最优分集合并系数。仿真结果表明,在发射分集条件下,本文提出的子载波频域均衡器有效地抑制了OFDM系统中由于循环前缀小于信道最大时延扩展所造成干扰和各个信道信号之间的互干扰,获得了较好的系统性能。 相似文献
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基于FB-FDE的地空通信分集接收技术 总被引:1,自引:0,他引:1
提出了基于滤波器组频域均衡(FB-FDE)的分集接收方法,充分利用了FB-FDE技术抗多径能力强和动态时变适应性好的特性,较好地解决了低仰角下的地空信道快速时变的频率选择性衰落问题。并且通过建立低仰角下地空信道天线的相关性模型,从理论上分析了天线相关性对FB-FDE技术的分集接收性能的影响。仿真试验表明,天线相关系数为0.5时能获得较好的接收分集增益。 相似文献
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大容量散射调制解调器设计方案探讨 总被引:1,自引:0,他引:1
简要介绍了近年来国外大容量散射通信的发展水平和主要技术特点,并根据我国现有的技术基础和对大容量散射通信的需求背景等因素对我国的16Mbps大容量散射调制解调器和编解码器的设计方案进行了探讨。最后分别给出了16Mbps大容量散射通信系统在白高斯噪声信道、信道模拟器及实际野外信道上的测试结果,从而证实了大容量散射调制解调器在采用自适应判决反馈均衡及Turbo乘积码的技术体制下,具备了可靠传输16Mb/s的数字信号的能力。 相似文献
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《Communications, IEEE Transactions on》2006,54(10):1870-1877
In this paper, we consider wireless multicarrier communications systems applying different transmit-antenna diversity techniques. Whereas the transmitter has available multiple antennas, we assume a single antenna at the receiver. Thus, we consider multiple-input single-output multicarrier transmission systems which are of special interest for downlink mobile radio applications. For these systems, we investigate the matched-filter bounds (MFBs) which represent the performance in an environment free of any interference and, thus, are lower bounds on the achievable performance. Especially, we focus on the analytical determination of the MFBs for selection diversity (SD), since this transmit-antenna diversity technique requires the least amount of preprocessing at the transmitter. Based on the derived MFBs, SD is investigated in detail, and compared with other transmit-antenna diversity techniques which are based on the maximum-ratio and the equal-gain transmission principles, respectively. 相似文献
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In this letter, we propose two efficient symbol detection algorithms for OFDM-based wireless LANs with space-frequency transmit diversity (SF-TD) scheme. In case that SF-TD scheme is applied to OFDM-based wireless LANs, the interference caused by insufficient number of sub-carriers may be generated between adjacent sub-carriers, and it degrades the overall system performance seriously. The proposed algorithms eliminate this interference in a parallel or sequential manner and achieve a considerable performance improvement over a conventional detection algorithm 相似文献
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This paper investigates the transmis-sion scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi... 相似文献
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《Communications, IEEE Transactions on》2005,53(8):1413-1413
Filterbank multicarrier modulation (FBMCM) is an attractive technology for high-speed twisted-pair transmission, and for broadband wireless communications, as well. In wireline applications, signal transmission takes place at baseband, so the issue of carrier acquisition and tracking for coherent demodulation does not apply. On the contrary, in wireless communications, carrier-frequency recovery reveals the Achille's heel of multicarrier modulation, so that robust signal-processing algorithms are needed in this respect. In this paper, we derive a nondata-aided carrier-frequency-offset recovery method for wireless FBMCM modems. In particular, we illustrate how to derive a low-complexity closed-loop tracker starting from a maximum-likelihood approach. We then show that the proposed simplifications do not entail large performance losses. In this respect, we derive the standard performance metrics of a closed-loop tracker (S-curve, root mean square estimation error, acquisition time), both on the additive white Gaussian noise channel and on a typical static frequency-selective wireless channel. We also demonstrate by simulation good robustness of the frequency tracker with respect to FBMCM symbol-timing errors. 相似文献