共查询到18条相似文献,搜索用时 93 毫秒
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构建了一种循环酉矩阵群的非差分分布式空时码,该码字基于一个简易的三跳通信信道模型,可以应用于信道状态不是特别优良,或者由于通信距离两节点之间不能实现直接通信的情况,也可以应用于Ad hoc网络.在源节点处用循环对角酉矩阵群来构建发送码字,利用分集和的方法得到最优生成矩阵.在中继处利用广义Hadamard矩阵构建中继酉矩阵,对信号进行酉线性处理.并得出三跳通信模型下部分相干分布式空时码的译码公式,根据此公式得到如何选择生成矩阵来提高系统性能.最后对该码字进行仿真对比,得出在低信噪比情况下,两跳通信系统性能比三跳模型的好,但是在高信噪比下三跳通信模型要比两跳的更为优良,并且比差分编码性能提高3dB左右. 相似文献
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设计了一种采用预编码方式的准正交空时编码(quasi-orthogonal space time code, QOSTC),其编码方案是首先对发送信号向量进行与信道状态信息无关的酉变换,然后再进行正交编码.酉变换可将QOSTC信道能转化为并行复用传输信道,实现无符号间干扰的高速率并行传输,且接双端信号的最大似然(maximum likelihood,ML)符号译码可简化成线性译码,从而可采用简单的线性检测降低译码复杂度.仿真结果表明,在高信噪比下,酉变换的QOSTC线性检测比没有酉变换的QOSTC的ML检测差2dB左右,但其分集度几乎相同. 相似文献
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针对水声信道复杂多变、强多途和大起伏干扰等特点,提出采用码率兼容QC-LDPC码的自适应信道编码技术,以提高水声数据传输的可靠性和水声信道的信道吞吐率。建立了码率兼容QC-LDPC码在水声信道中的仿真模型,构造码率为1/2、2/3…5/6等一系列QC-LDPC码,在三种典型的水声信道中对其性能进行仿真。结果表明所设计的码率兼容QC-LDPC码在三种不同信道下可行有效,能较大地提高水声通信系统的性能。由于信道时延越长、信噪比越低,满足通信指标的码率就越低;并给出码率兼容QC-LDPC码在浅海水声信道中不同信噪比下满足通信性能指标的编码码率的查找表。码率兼容QC-LDPC码提高了水声通信的信道利用率,具有灵活的编译码性能,在水声自适应通信中具有很好的应用前景。 相似文献
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纠错编码技术在水声跳频通信中的性能研究 总被引:1,自引:0,他引:1
将水声跳频通信系统与纠错编码技术相结合进行了研究,针对复杂多变、强多途和起伏干扰的浅水水声信道,建立了基于BELLHOP射线模型的时变衰落水声信道模型,该信道模型建立起了信道特性与海洋环境参数之间的关系,在海洋环境参数给定的条件下可以精确仿真信道。在此基础上通过系统仿真的方法研究了卷积码、RS码和串行级联码三种纠错编码方案在水声跳频通信系统中的性能,给出了两种典型信道下的仿真结果并进行了对比分析,结果表明串行级联码具有更强的纠错能力,比较适合复杂多变的水声衰落信道。 相似文献
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针对Polar码性能收敛速度慢和低密度生成矩阵(LDGM)码存在高错误平层的问题,在保持这两种码的低编码复杂度和低译码复杂度不变的前提下,提出了一种将Po-lar码作为外码,LDGM码作为内码的串行级联Polar-LDGM编译码设计方案,使之可以接近二进制输入加性高斯白噪声(BI-AWGN)信道香农容量.通过对Polar-LDGM编译码系统模型的仿真,得到了近优的内外码编码速率组合与近优的内码码重.仿真结果表明,上述方案在保证低复杂度的前提下,可以获得良好的比特错误率(BER)性能,并可以有效地降低LDGM码错误平层. 相似文献
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近年来,为了提高无线频谱的利用率,一些学者提出了一种结合分集发送、调制和编码的空时码。空时码是应用于无线通信中的一种新的编码和信号处理技术,它将信道编码技术与分集技术相结合,从而提高信号在无线衰落信道中传输的可靠性,采用这种技术以后,可以大幅度地提高无线通信系统的信息容量和传输速率,并能有效地提高抗噪声和抗干扰的能力。 相似文献
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The performance analysis of high rate space-time trellis-coded modulation (HR-STTCM) using the Gauss-Chebyshev quadrature technique is presented. HR-STTCM is an example of space-time codes that combine the idea used in trellis coded modulation (TCM) design that is signal set expansion and set partitioning into its construction. HR-STTCM construction is based on the concatenation of an outer TCM encoder and inner space-time block code. This paper evaluates the exact pairwise error probability of HR- STTCM based on the Gauss-Chebyshev quadrature formula. Comparison of numerical and simulation results shows that the proposed method is accurate. The method used is shown to be computationally simpler than those in the literature. 相似文献
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The performances of orthogonal space-time block codes (OSTBCs) over Rician- Nakagami channels are investigated. In particular, we derive closed-form symbol error probability (SEP) expressions for OSTBC systems in which M-ary phase-shift-keying modulation and M-ary quadrature-amplitude modulation are used. These SEP results are expressed in terms of Lauricella's multivariate hypergeometric functions, which can be easily evaluated numerically. When the Rician-Nakagami channel degenerates to the Rician-Rayleigh channel, or equivalently the Rayleigh fading channel, the closed-form SEP expressions are rewritten in terms of higher transcendental functions, that is, Gauss hypergeometric function and Appell hypergeometric function. 相似文献
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The authors analyse concatenated bit-interleaved coded modulation and orthogonal space-time block codes (OSTBC) over fading channels in the absence and presence of channel state information (CSI) in receiver. The authors derive analytical expressions for bit and frame error probabilities based on which corresponding designing rules are proposed. The analytical results are for arbitrary rate of constituent STBC and arbitrary convolutional code, and for CSI-aware receiver is for any number of transmit and receive antennas. Simulation results are presented to confirm the validity of the proposed designing rules. Moreover, the simulation results show that the proposed system outperforms concatenated trellis coded modulation and OSTBC. 相似文献
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差分酉空时协作系统的多符号裁减自动球形译码 总被引:1,自引:1,他引:0
鉴于差分协作系统中多符号差分检测(multiple-symbol differential detection,MSDD)算法计算复杂度高的缺点,引入裁减自动球形译码(pruning automation sphere detection,PASD)算法来降低差分酉空时协作系统的检测复杂度.PASD算法是在球形译码的基础上,结合自动球形译码和裁减球形译码的思想而提出的.通过对扩展节点所消耗的复杂度和系统的误码率两方面来分析译码算法的性能.仿真分析表明,在差分酉空时协作系统中,PASD算法在误码性能几乎不变的情况下,复杂度曲线比球形译码(sphere detection,SD)算法收敛迅速.其中在分组长度N=5、信噪比SNR=15dB的情况下,PASD、SD算法的扩展点数分别为14.138 6、78.950 5,大大降低了系统的复杂度;同时,当SNR>16dB时,协作节点的增加有利于提高系统的误码性能,系统的复杂度性能并没有很大的损失. 相似文献
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传统的空时自适应处理(Space-Time Adaptive Processing,STAP)利用窄带混响和目标在空时平面的可分辨特征抑制窄带混响。对宽带混响和目标在空时平面分布特征进行研究,并通过理论推导,得出带宽对混响和目标空时分辨特征的影响公式。结果表明:宽带混响和目标在空时平面分布特征部分重叠,导致传统STAP效果不佳。在此基础上,借鉴STAP思想,并利用线性调频(Linear Frequency Modulation,LFM)信号在分数阶Fourier变换域上的聚焦性,分析了在空-分数阶Fourier域三维空间上抑制宽带LFM混响的可行性。 相似文献
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A versatile fading distribution that generalises many commonly used models for multi-path and shadow fading is the so-called generalised-K (KG) distribution. By considering the product of N independent but not necessarily identically distributed (n.i.d.) squared KG random variables (RVs), we derive exact closed-form expressions for the moment generating function, probability density function, cumulative distribution function and the moments of the cascaded KG fading channel. Expressions for the ergodic capacity and the error performance of different digital modulation schemes are also obtained. Based on the above mentioned formulas, we analyse the performance of orthogonal space-time block codes over multiple-input multipleoutput keyhole KG fading channels. Various performance evaluation results demonstrate the proposed mathematical analysis. 相似文献
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An uplink direct sequence spread spectrum communications systems employing a multi-sequence model over a quasi-static frequency-selective fading channel is considered. In analogy with bit-interleaved coded modulation (BICM) technique, a group of bits at the output of a bit-wise interleaver is mapped uniquely to a complex signalling vector belonging to an orthogonal plane sequence modulation signal space, which is constructed over a set of expanded signature sequences. This transmission system provides not only bandwidth efficiency offered by additional signal planes but also time diversity resulting from the BICM technique. It is observed that at high system traffic load error performance could degrade substantially due to user cross-correlations, multi-access asynchronism as well as channel frequency selectivity. The authors employ a 'turbo principle' receiver, consisting of a soft interference cancellation scheme, soft demappers and maximum a posteriori decoders, to avert this capacity loss by exploiting the serially concatenating structure at the transmitter. After simple mathematical manipulation, a soft space-time linear minimum mean-square error multi-user detector could even be explored on the basis of per signal plane per user. Both analytical performance-bound and computer simulation of the proposed framework in terms of bit-error rate (BER) are revealed. Further, performance comparisons with convolutionally coded and conventional bandwidth-efficient coded direct sequence code division multiple access systems under the same system conditions are illustrated. The authors have also investigated the impact of labelling maps on the BER performance. 相似文献
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Orthogonal space-time block codes (STBCs) are known to orthogonalise the multiple-input multiple-output (MIMO) wireless channel, thus reducing the space-time vector detection to a simpler scalar detection problem. The capacity of STBCs over correlated Rayleigh and Ricean flat-fading MIMO channels under different adaptive transmitting techniques is studied. Three adaptive schemes known as optimal power and rate allocation, total channel inversion with fixed rate policy and its truncated variant are studied. Taking into account the effect of channel correlation, closed-form expressions are obtained for the capacity of orthogonalised Rayleigh and Ricean MIMO channels under these adaptive transmission techniques in order to avoid Monte-Carlo simulations 相似文献