共查询到19条相似文献,搜索用时 140 毫秒
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在传统的方案中,将准正交空时码(quasi-orthogonal space-time block codes)经过调制之后强行转换为酉空时码(unitary space-time codes)再进行差分编码.将调制方案进行改进,以使得码元之间的距离增大,以提高其编码增益,从而提高系统性能.与传统的准正交差分空时码相比,所提方案误码性能得以提高. 相似文献
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差分酉空时调制(DUSTM)是一种应用于时变衰落信道下的多天线调制方法。该方法在慢衰落信道下无需知道信道状态信息而能获得全发送分集增益。但是,在快速衰落信道下,其性能明显恶化并且呈现出较高的误码平层。该文通过在差分酉空时调制中引入矩阵分割和子矩阵交织等操作提出了一种基于子矩阵交织的差分酉空时调制(SMI-DUSTM)方案,并对其性能进行了分析。性能分析和相应的计算机仿真证明了SMI-DUSTM 不仅能够继承DUSTM在慢衰落信道下的优点,而且在快速衰落信道下能够保持良好的系统性能。 相似文献
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本文提出了一种采用分布式差分空时分组编码和检测的协同分集方案,在不需要信道状态信息(CSI)的情况下可以实现满分集和全速率发射,并推导了相关瑞利信道下该方案误码率(BER)性能上限的解析表达式。传统的差分空时分组编码对整个码块进行差分,而协同分集下的任何一个协同用户进行差分编码时都不知道整个码块的信息。本文所提出的差分BPSK调制方案,通过将两协同用户的信息分别被调制到相互正交的实轴和虚轴上,从而将码块的联合差分转化为各用户独立差分。分析了在协同用户间不同的信道状态信息(CSI)和协同用户到接收用户不同的CSI情况下本文所提出发射方案的性能。仿真结果表明本文所提出的方案获得了明显的分集增益,同时也较好的吻合了理论分析的结果。 相似文献
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提出了一种应用于MIMO-OFDM系统的基于循环延迟分集的多流差分酉空时频编码方案.该方案利用了差分和酉矩阵技术、结合了正交空时码的分集优势,在不需要信道估计的情况下较大程度地改善了整个MIMO-OFDM系统的误码性能. 相似文献
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一种串行Turbo-DFH迭代解调译码方案 总被引:2,自引:1,他引:1
该文将差分跳频(DFH)系统的频率转移过程视为一种编码,提出了一种串行Turbo-DFH迭代解调译码方案。该方案的编码器由外编码器,交织器和差分跳频转移函数串行级联组成,译码器采用串行迭代结构译码。并针对DFH系统的特点,推导了一种新的DFH系统软输入软输出算法。仿真结果表明,该解调译码方案相对传统的DFH解调算法,性能得到了明显的改善。 相似文献
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In this paper, time-spreading wavelength-hopping optical CDMA system using trellis coded modulation scheme is investigated. The carrier hopping prime code and its shifted version are employed as signature sequences. Since the carrier hopping prime code is a symmetric code, the out of phase autocorrelation is zero. Applying the orthogonality of the signature sequences, the ternary transmission mechanism can be achieved. The proposed coding scheme is simple in both transmitter and receiver. As the multiple access interference and beat noise are the major deterioration of system performance, using coding scheme is an effective way to reduce the error floor. The numerical results reveal that the proposed coding scheme can significantly improve the system performance. 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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针对双卫星中继协作通信系统中存在非符号周期整数倍的时延差问题,提出了一种双采样的差分空时正交频分复用(D-OFDM2)方案。所提方案在卫星信道条件未知的情况下,基于具有时延容忍的 D-OFDM编码,在接收端构造了一种双采样方法。该方法在以符号速率采样的同时,对当前主瓣大于相邻旁瓣的区间内增加一次采样,并将两次采样结果等增益合并。仿真结果表明,在系统时延差为非符号周期整数倍的情况下,该方法较单采样方法能获得更高的接收信噪比,同时改善了系统误码性能。 相似文献
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In differential chain coding (DCC), the bandwidth efficient relative vector is sensitive to channel errors, resulting in error propagation and corruption of the decoding process. A robust differential chain coding scheme is presented for stopping error propagation in the relative vector without increasing its bandwidth or using an additional forward error correction code. In this scheme, the relative vector is combined with the previous absolute vector to form a new error-resistant channel codeword. Experiments showed that, compared to DCC, the new scheme notably improves subjective quality when subject to transmission errors 相似文献
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针对全球移动通信系统 (GSM) 的安全机制不能实现端到端安全通信问题,提出了一种低复杂度基于脉冲调制的数据传输方案及优化方法。分别设计了基于脉冲位置调制及脉位结合极性调制的类语音信号,给出了基于跳时脉冲的帧同步方法。搭建了基于脉冲调制的GSM语音信道数据传输仿真平台,分析比较了不同调制阶数和不同自适应多速率编码 (AMR) 码率下系统的性能。为了提高系统可靠性,引入卷积码进一步降低了系统误码率。仿真结果表明,4阶脉冲调制最适用于语音信道,所提脉冲调制方法与传统低复杂度频移键控 (FSK) 调制方式误码率近似,但传输速率高,且提出的脉位结合极性调制进一步提高了传输速率,总提高比例达到36%。 相似文献
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Xiaoping Jin Xinqiang Han Ning Jin Youming Li Zhengquan Li Xiuming Wang 《International Journal of Communication Systems》2016,29(3):553-566
This paper focuses on noncoherent detection scheme for multiple‐input multiple‐output two‐way relay channel network with two two‐antennas source nodes and one single‐antenna relay node. An orthogonal differential space–time network coding (ODSTNC) scheme based on relay detection and forward protocol is proposed. The proposed scheme combines space–time coding with network coding, and the differential modulation and detection are used in both multiple access stage and broadcast stage. The multiple‐symbol differential detection is employed at the relay. The maximum likelihood decision and its low‐complexity sphere decoding decision are given. The upper and lower bounds on the average symbol error probability for this system under differential binary phase shift keying (DBPSK) are derived, and a diversity order of 2 is confirmed to be achieved. The simulation results show that the ODSTNC scheme has good performance, and it is available for the applications of far distance signal transmission between two terminals where channel state information is unknown. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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The visual quality is a critical factor in prediction video coding over packet-switched networks. However, the traditional MSE-based error resilient video coding cannot correlate well with the perceptual characteristics of the human visual system (HVS). This paper proposes a structural similarity (SSIM) based error resilient video coding scheme to improve the visual quality of compressed videos over packet-switched networks. In the proposed scheme, a SSIM-based end-to-end distortion model is developed to estimate the perceptual distortion due to quantization, error concealment, and error propagation. Based on this model, an adaptive mode selection strategy is presented to enhance the communication robustness of compressed videos. Experiments show that the proposed scheme significantly improves the visual quality for H.264/AVC video coding over packet-switched networks. 相似文献