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一种新OFDM系统及其信道盲估计性能的研究 总被引:1,自引:0,他引:1
提出了一种采用不等长分组新的OFDM系统。采用不等长分组的好处是不需要加循环前缀,就能在发射序列中引入周期平稳性,因此采用子空间算法可实现信道的盲辨识。还对信道盲估计性能进行了分析。 相似文献
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基于子空间分解的半盲信道估计 总被引:1,自引:1,他引:0
信道估计从大的角度可分为非盲估计和盲估计以及在此基础上产生的半盲估计.半盲估计在数据传输效率和收敛速度之间做一个折中,即采用较少的训练序列来获得信道的信息.文章详细介绍了基于子空间分解的半盲信道估计的算法. 相似文献
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基于子空间分解的OFDM信道盲辨识 总被引:3,自引:0,他引:3
该文提出一种基于子空间分解的正交频分复用(OFDM)信道的盲辨识算法,将OFDM信号等效为单输入多输出的过采样信号,采用过采样信号的循环稳态特性和子空间分解方法估计信道参数,算法不需要任何训练序列和周期性的引导信号,实现了0FDM信道的盲辨识。对于宽带OFDM移动通信系统,通常子信道数较大,信道响应持续时间短于0FDM符号周期,因此,可以将整个系统分为若干个子系统,各子系统分别进行信道辨识,能有效地降低信道估算的复杂性。 相似文献
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针对SIMO信道的经典盲估计方法,如子空间法(SS)等,都是基于接收端样本自相关阵的特征值分解(EVD)或奇异值分解(SVD)来实现信道估计的,而基于QR分解的SIMO信道盲辨识方法是最近提出的一种性能优良的新算法.本文将该算法推广为MIMO信道盲辨识算法,并且证明了在一定的假设下,即使各路源信号为空间相关且其统计特性未知时,该算法仍然保持有效.实验结果表明这种MIMO辨识算法具有收敛速度快、计算量小、无须对噪声做额外的处理、对噪声不敏感等优点.我们还将这种算法与经典的MIMO辨识算法进行了性能比较. 相似文献
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本文研究了OFDM空时发射分集系统的子空间信道盲估计方法。该方法仅利用空时编码及OFDM调制引入的冗余,在接收天线小于发射天线时,也可以对信道进行盲估计。对盲估计方法所共有的估计模糊性问题进行了详细的论述,证明估计仅存在两个标量不确定因子。这种方法不需要对信号进行冗余预编码,系统将有更高的速率;同时也不需要对系统输出进行过采样或采用多天线接收。由于不需要确切知道信道的阶数,算法对信道阶数过估计有较好的鲁棒性。 相似文献
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提出了一种基于多级维纳滤波(MSWF: Multistage Wiener Filter)的盲信噪比估计算法。结合信号子空间分解理论,该方法利用多级维纳滤波器的相关相减结构(CSA: Correlation Subtraction Algorithm)前向递推实现含噪信号空间分解,避免了传统方法对信号自相关矩阵进行复杂的特征值分解运算,并以此估计信号功率和噪声功率来完成盲信噪比估计。在加性高斯白噪声(AWGN)信道条件下进行信噪比估计仿真,仿真表明,当实际信噪比在-7~25dB范围内时,估计器的估计标准偏差小于0.5dB,且性能优于常规方法。设定实际信噪比为10dB,当接收码元数目为100时,对所有仿真的调制方式信噪比估计标准偏差小于0.35dB,证明了估计器在小样本支撑环境下实现信噪比快速盲估计的能力。 相似文献
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Dolph's method for determining the optimum element currents for half-wavelength equispaced discrete linear arrays is generalized to symmetric discrete linear arrays. The theorem proved gives sufficient conditions for the existence of optimum beam patterns for arrays with elements symmetrically positioned about the array center, but with fixed unequal spacings between the elements. The conditions are such that the Remes exchange algorithm for minimax approximation of functions can be employed to compute the optimum element currents corresponding to an optimum beam pattern directly from the given spacings of the elements. Half-wavelength spaced linear arrays satisfy the conditions of the theorem; therefore, it provides a new method of calculating the well-known Dolph-Chebyshev element currents. An example with unequal spacings is included to show the utility of the method even when the hypotheses of the theorem may not be met. 相似文献
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Pavlushkov V. Johannesson R. Zyablov V.V. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(2):700-708
In this correspondence, unequal error-correcting capabilities of convolutional codes are studied. For errors in the information symbols and code symbols, the free input- and output-distances, respectively, serve as "unequal" counterparts to the free distance. When communication takes place close to or above the channel capacity the error bursts tend to be long and the free distance is not any longer useful as the measure of the error correcting capability. Thus, the active burst distance for a given output and the active burst distance for a given input are introduced as "unequal" counterparts to the active burst distance and improved estimates of the unequal error-correcting capabilities of convolutional codes are obtained and illustrated by examples. Finally, it is shown how to obtain unequal error protection for both information and code symbols using woven convolutional codes. 相似文献
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利用信号的二阶统计特性实现信道盲估计。信道盲估计可以采用最小均方误差(MMSE),最小平方(LS)两种方法,并结合MonteCarlo仿真表明,在信噪比较低时,最小均方误差方法计算出的误码率性能比最小平方方法好。 相似文献
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Using polarization-maintaining fiber (PMF) sub-sections with unequal lengths, an all-fiber polarization mode dispersion (PMD) emulator with reduced number of polarization controllers is proposed and demonstrated. With six polarization controllers and seven PMF sections, each consists of four sub-sections with unequal lengths and spliced at 45° relative to each other, the generated PMD first- and second-order statistical distributions are close to those of the real fiber link with negligible deviations, therefore, the cost of all-fiber PMD emulators, mainly from the electrically driven polarization controllers, is significantly reduced. 相似文献
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Error-resilient image and video transmission over the Internet using unequal error protection 总被引:1,自引:0,他引:1
This paper presents a new bit-plane-wise unequal error protection algorithm for progressive bitstreams transmitted over lossy networks. The proposed algorithm protects a compressed embedded bitstream generated by a 3-D SPIHT algorithm by assigning an unequal amount of forward error correction (FEC) to each bit-plane. The proposed algorithm reduces the amount of side information needed to send the size of each code to the decoder by limiting the number of quality levels to the number of bit-planes to be sent while providing a graceful degradation of picture quality as packet losses increase. We also apply our proposed algorithm to transmission of JPEG 2000 coded images over the Internet. To get additional error-resilience at high packet loss rates, we extend our algorithm to multiple-substream unequal error protection. Simulation results show that the proposed algorithm is simple, fast and robust in hostile network conditions and, therefore, can provide reasonable picture quality for video applications under varying network conditions. 相似文献
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气体绝缘组合电器(gas insulated switchgear,GIS)以其占地面积小、不受天气影响、可靠性高等的优良性能在电力系统中的得到了广泛应用,然而,GIS内部会出现由于绝缘缺陷引起的局部放电(partial discharge,PD),PD长时间发展会导致GIS绝缘损害,对PD进行检测显得尤为重要。文章模拟了高压导体尖刺、盆式绝缘子表面金属颗粒和外壳尖刺3种典型的绝缘缺陷,采用脉冲电流法和超声波检测法对其产生的局部放电信号进行了检测,得到了相应的信号特性,对现场应用起到了一定的指导意义。 相似文献
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We analyze the performance for the noncoherent reception of M-ary orthogonal frequency shift keying with postdetection equal gain combining over a correlated fading channel. Two kinds of correlated fading statistics are considered: (1) Nakagami fading in which the diversity branches can have unequal signal-to-noise ratios (SNRs) as well as different m-parameters and (2) Rician fading in which the diversity branches can have unequal SNRs. Using the characteristic function of the combiner output SNR, closed-form expressions for the symbol error probability are obtained 相似文献