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分集技术是对抗多径衰落的一种有效方法,而空时分组码(SpaceTime Block Code,STBC)和最大比合并算法(Maximum Ratio Combining,MRC)是两种常用的分集技术。提出了一种采用STBC和MRC相结合的算法,在已知信道矩阵H的前提下,计算出两种算法可达到的信噪比,动态选择信噪比较高的方法进行传输,从而提高整个系统的接收信噪比。通过仿真可以得到,当误比特率为10-3时,混合算法的性能比两种独立算法提高了3~4 dB。 相似文献
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发射分集是近年来才发展起来的一种技术,在第三代移动通信系统中已经开始普遍采用。本文简单介绍了几种发射分集技术,并分析了各自的优缺点。特别针对发射信号设计的新技术-空时码进行了详细讨论,然后论述了WCDMA中发射分集技术的应用,并进行了性能仿真比较。 相似文献
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发射分集(TD:transmit diversity)是第3代移动通信(3G)cdma2000和WCDMA系统采用的一项关键技术。它利用发射天线空间分隔以获得相互独立的衰落信号的发射和接收,改善系统性能。文中主要描述了几种发射分集技术的概念,特点及性能。 相似文献
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在移动通信中,高速下行数据通信技术一直是研究的热点。由于手机终端体积的限制,以及电池容量和价格方面的限制,在下行链路采用发分集将是未来移动通信很自然的选择。文章从实用的角度,时结合MIMO的空时分组码进行了分析,指出了由于它的译码只有线性复杂度,在移动通信下行链路中,将有很大的应用优势。 相似文献
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In this paper we propose the combination of space-time diversity techniques and signal space diversity, in order to improve communication system performance. Specifically, we use prior knowledge of the channel behavior to design a mapping algorithm to generate a two-dimensional constellation with the same number of symbols as MPSK constellations currently used in coherent space time block coding applications, to demonstrate that superior performance can be achieved. This is accomplished by constructing a two-dimensional map that results from the minimization of the estimated symbol error probability when transmission occurs in a fading environment. System performance for each each mapping is assessed in quasi-static Rayleigh fading channels. 相似文献
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针对线性离散多址复用(LDDMA)系统,文章研究在线性迫零(Zero-Force)接收机条件下的多用户选择分集与调度算法。对于用户子集选择算法,遍历搜索是最优的,但它所引起的繁重的计算复杂度,很难在实际中应用。基于此考虑,本文提出三种次优的贪婪选择准则:最大信道增益选择,最大信道容量选择与最大最小后验SNR选择。数值仿真结果表明:最大最小后验SNR准则可以提供较好的BER性能。 相似文献
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Space diversity reception, in which several signals received at different antennas are combined, is a well known method that can be used to combat the effects of fading in wireless systems. Also, trellis coded modulation (TCM), when combined with interleaving of sufficient depth, is known to provide some form of time diversity that allows the achievement of good error performance in fading environments. In this paper we consider the analysis of the error performance of reference-based Maximal Ratio Combining (MRC) systems when used in conjunction with trellis-coded MPSK modulation techniques over a Rayleigh fading channel. We also consider the analysis of MRC trellis-coded MPSK systems with conventional differential detection. The results are obtained by using a combination of theoretical analysis and simulation. Exact and near-exact expressions for the pairwise error-event probability in Rayleigh fading are derived. Monte-Carlo simulation results, which are more indicative of the exact system performance, are also given. 相似文献
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提出了一种分布式差分空时分集方案,通过对差分编码方式的改进,可使用多种星座形状来进行调制。在采用了QAM星座调制时,比传统的PSK调制具有更好的性能,可以改善无线网络中的能量效率。在不考虑协同节点间误码的情况下,分析和推导了平坦衰落瑞利信道下该方案的SER性能上限的表达式。仿真结果表明采用QAM调制下的DSTBC性能优于PSK调制下的DSTBC。同时在慢衰落的条件下,仿真结果和理论分析的结果吻合较好,说明了方案的有效性。 相似文献
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对于接收端和发送端均不具备信道状态信息的MIMO系统,本文将Cayley变换与对角块正交空时分组码结合,提出了一种新的酉空时分组码构造方法。新构造的空时分组码适用于任意发送天线数为偶数的MIMO系统,能提供满发送分集度和1.5符号/信道利用的信息传输率,并可采用球检测法等低计算复杂度检测算法得到准最优的检测结果。 相似文献
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In a multi-user communication system, cooperative diversity allows single-antenna mobile sets to achieve transmit diversity.
Cooperative diversity improves the communication capacity and enhances the robustness of a wireless link when a single channel
alone is not reliable. In this paper, a novel cooperative diversity scheme is introduced that enables simultaneous transmission
of non-redundant data from all cooperative terminals. By taking advantages of both high-rate full-diversity space-time codes
and the cooperative diversity, the proposed method provides high diversity gain beyond the number of physical transmit antennas
without compromising the data rates. In essence, the proposed system aims at higher data rates over the non-cooperative counterpart,
while maintaining the full diversity gain. 相似文献
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空间调制系统作为多输入多输出技术(Multi-input Multi-output,MIMO)的一种,优点是在减少多天线方案的复杂度和成本的同时,始终能够保证较高的数据传输速率。在每个信道使用间隙下,仅使用一根选定的天线(称为活动天线)发送数据信号,并且活动天线空间位置作为数据传输的附加维度。然而,空间调制技术的分析和设计依然面临许多挑战,编码空间调制方案就是其中一种。针对编码空间调制方案,重点论述了Trellis码、BMST码、LDPC码以及多元LDPC码等信道编码空间调制方案,并且分析了这几种方案的特点以及它们在MIMO中的应用。 相似文献