共查询到20条相似文献,搜索用时 15 毫秒
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This paper presents a novel Reed-Solomon codes based transmission scheme called RS-SC-CP. While RS-SC-CP is essentially a Reed-Solomon (RS) coded single carrier with cyclic prefix (SC-CP) system, a filter bank representation of the RS code is used. This filter bank representation unveils a DFT synthesis bank, just as in a traditional Orthogonal Frequency Division Multiplexing (OFDM) system (allbeit in a finite field). Therefore, RS-SC-CP is topologically equivalent with OFDM. As such, the RS-SC-CP system inherits the advantages of an SC-CP system over a traditional OFDM system like a low Peak to Average Power Ratio (PAPR). But, more importantly, it allows us to use a novel equalization technique that resembles a traditional OFDM equalizer. The equalizer of an RS-SC-CP receiver is split into two stages: the first stage encompasses a partial equalization in the complex field, which ensures that the residual channel response has integer coefficients. It is calculated using a Minimum Mean Square Error (MMSE) criterion. The residual ISI is removed by a Galois field equalizer in the second stage, posterior to the RS decoding removing the noise. Finally, the performance of the RS-SC-CP system is further evaluated by simulations showing the performance gain of the RS-SC-CP system compared to a traditional coded OFDM or single carrier with cyclic prefix (SC-CP) scheme. 相似文献
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Currently, the single-carrier cyclic prefix (SC-CP) uses a receiver based on a frequency-domain equaliser. It is proposed to use the lattice code decoder in SC-CP. Since the lattice code decoder is now available for near maximum-likelihood (ML) decoding, the proposed SC-CP detector outperforms the detector based on the equalising technique, especially for the channel with spectral s. 相似文献
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BER minimized OFDM systems with channel independent precoders 总被引:1,自引:0,他引:1
Yuan-Pei Lin See-May Phoong 《Signal Processing, IEEE Transactions on》2003,51(9):2369-2380
We consider the minimization of uncoded bit error rate (BER) for the orthogonal frequency division multiplexing (OFDM) system with an orthogonal precoder. We analyze the BER performance of precoded OFDM systems with zero forcing and minimum mean squared error (MMSE) receivers. In the case of MMSE receivers, we show that for quadrature phase shift keying (QPSK), there exists a class of optimal precoders that are channel independent. Examples of this class include the discrete Fourier transform (DFT) matrix and the Hadamard matrix. When the precoder is the DFT matrix, the resulting optimal transceiver becomes the single carrier system with cyclic prefix (SC-CP) system. We also show that the worst solution corresponds to the conventional OFDM system; the conventional OFDM system has the largest BER. In the case of zero forcing receivers, the design of optimal transceiver depends on the signal-to-noise ratio (SNR). For higher SNR, solutions of optimal precoders are the same as those of MMSE receivers. 相似文献
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This letter proposes a two-dimensional pilot-aided channel estimator for multicarrier and single carrier cyclic prefix assisted code division multiple access systems in the presence of timing-offset errors. Using optimal training sequences with special cyclic correlation properties can minimize the timing offset errors. Optimal and binary sub-optimal training sequences are designed in this context. Both theoretic analysis and simulation studies demonstrate significant performance improvement for the proposed method over conventional frequency domain channel estimation methods. 相似文献
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介绍了下行链路中基于循环前缀的单载波直接序列扩频技术(CP/CDMA)。这种技术结合了多载波系统中的循环前缀和频域均衡,具有较低的复杂度。同时保留了单载波系统发射端复杂度低的优点。在时变信道中,利用基于辅助数据的信道估计方法,即每隔一定帧数的数据帧发送一帧训练序列来估计信道。在仿真中使用了信道编码。 相似文献
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A new bandwidth efficient single carrier system with frequency domain equalisation is proposed. Turbo equalisation and cyclic prefix reconstruction are combined together to eliminate the normally required cyclic prefix for such a system. The proposed method achieves much better performance than the residual inter-symbol interference cancellation approach by utilising soft decoded information and introducing turbo equalisation. The performance of the proposed scheme is studied through simulations. 相似文献
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与传统的正交频分复用(OFDM)频域信道估计方法不同,提出了一种循环前缀为PN序列的OFDM信道估计方法:在时域OFDM符号中不插入传统意义上的循环前缀,而是插入PN序列作为训练序列,将PN序列与对应的接收序列作圆周相关处理获得信道频率响应估计;而由于PN序列周期性出现,它也起到了循环前缀的作用。仿真结果表明:在多径瑞利衰落信道中,在相同信噪比和相同信道利用率的条件下,提出的算法比频域梳状导频插入的时域滤波算法具有更高的信道估计精度。 相似文献
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To allow for a computationally efficient equalization scheme for the frequency-selective transmission channels encountered
in wireless local area network (WLAN) applications, cyclic prefix (CP) block transmission schemes have been proposed, such
as single-carrier CP (SC-CP) and multi-carrier CP (MC-CP) transmission, also known as orthogonal frequency division multiplexing
(OFDM). In this letter, however, we focus on the known symbol padding (KSP) transmission scheme. In this scheme known padded
sequences can be exploited for synchronization as well as for channel estimation. However, to simultaneously allow for low-complexity
frequency-domain equalization and accurate channel estimation within the KSP context, a modified KSP scheme is proposed, namely
shifted KSP (S-KSP). Comparing different block transmission schemes in the WLAN context, the S-KSP scheme is shown to offer
a very good performance. 相似文献
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This letter proposes a novel semi-blind layered space-frequency equalization (LSFE) receiver for single- carrier cyclic-prefix (SC-CP) multiple-input multiple-output (MIMO) systems with block transmission, based on independent component analysis (ICA). Simulation results show that semi- blind LSFE with various Doppler shifts can provide performance close to the case with perfect channel state information (CSI), using a training overhead of only 0.05%. It also significantly outperforms its orthogonal frequency division multiplexing (OFDM) counterpart with perfect CSI and semi-blind linear SC frequency domain equalization (SC-FDE) over a wide range of signal to noise ratios (SNRs). 相似文献
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The symbiotic FM radio data system(SRDS)is a radio data system that a specially designed OFDM signal co-lives with FM signal,which enables a significantly higher data rate than existing radio data systems.The cyclic prefix of the OFDM symbol has the same length as the OFDM body,which enables the analytic separation of the co-channel OFDM and FM signal at receiver side,utilizing the fact that the OFDM body and prefix is equal.In this work,we show that the OFDM body and prefix cannot be viewed as equal when there is sufficient carrier frequency offset(CFO).Thus,we propose a two-step CFO estimation algorithm for FM and SRDS hybrid signal.The first step estimates the coarse CFO by exploring the characteristics of the FM signal.Once the coarse CFO is removed,the residual CFO is small enough for FM and OFDM separation.The second step fine estimates CFO from the OFDM-only signal using its repeated PN structure after the separation.Detailed mathematical equations are formulated and simulation results are given.The results show that the proposed algorithm works fine with the simulation setup and has a final residual CFO less than 3.9Hz. 相似文献
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In time varying channels, symbol recovery for single carrier cyclic prefix (SCCP) systems becomes complicated, because the orthogonality of channel frequency response (CFR) matrix is destroyed. In response, we propose a block turbo equalization algorithm in the time domain for SCCP to cope with channel time variations. In particular, the band structure of the channel time response (CTR) matrix is exploited to reduce the computational complexity of matrix inversion. In order to use this equalization scheme, accurate channel state information (CSI) must be available. Accordingly, we present a doubly selective channel estimation method for SCCP block transmissions with the aid of a Karhunen-Loeve basis expansion model (KL-BEM). In this method, the channel estimates are firstly obtained by using the cyclic prefix (CP) of each block, and then further refined by employing an expectation maximization (EM) based iterative algorithm. Combining the iterative estimator with the proposed equalizer naturally results in a doubly iterative receiver, the performance of which is shown to come close to the performance with perfect CSI. 相似文献
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本文概述了数字电视地面广播传输系统中存在的非线性失真和相位噪声影响因素;用模型统一表达了CP-OFDM和TDS-OFDM的OFDM复包络信号;从理论上分析了循环前缀和不断插入的导频训练序列会导致基于CP-OFDM的数字电视地面广播传输系统比在同等的外界条件下的基于TDS-OFDM的数字电视地面广播传输系统具有更低的有效数据符号信噪比水平;详细推导了在非线性失真和相位噪声共同影响下的CP-OFDM系统和TDS-OFDM系统的有效数据符号的统一信噪比表达式;定义并统一表达了在非线性失真和相位噪声共同影响下的CP-OFDM系统和TDS-OFDM系统的性能恶化指标;从理论和计算机仿真两方面比较分析了受到各种不同非线性失真和相位噪声影响的基于CP-OFDM和基于TDS-OFDM的两种不同数字电视地面广播传输系统的性能恶化程度. 相似文献
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该文设计了一种联合判决-反馈均衡的单载波频域均衡(SC-FDE)系统,该系统用固定波形的短pn序列取代常规SC-FDE系统中的循环前缀(CP),并以多个短pn序列组成的长PN序列作信道训练从而解决快变信道的初始估计和跟踪问题。针对该系统,一种在时域内对接收的多个训练序列进行平均,然后提出了在频域对信道信息进行估计的信道训练算法,该算法与传统SC-FDE系统相比,其计算复杂度较低。另外,提出了一种增加纵向校验的LDPC码用于该系统中降低信噪比门限,提高系统的整体性能。仿真结果表明在多径衰落信道中,此系统可获得较为理想的结果。 相似文献
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一种新的PCC-OFDM定时时偏盲估计 总被引:4,自引:2,他引:2
多项式相消编码PCC是一种编码技术,在PCC—OFDM调制中,它把将发送的信息调制到一组加权的子载波而不是单个子载波中去。PCC能够显著地降低OFDM对载波频偏的敏感性。本文对PCC—OFDM系统提出了一种新的定时盲估计,估计器是在接收机中的FFT之前进行的。基于PCC—OFDM的符号波形特征,构建定时时偏估计度量函数。最大化度量来估计定时时偏。本估计器不需要训练序列、导频信号或周期前缀。仿真表明,估计器在一个OFDM符号内收敛,且误差较小。 相似文献
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Adriana Lipovac Vlatko Lipovac Borivoj Modlic 《Wireless Communications and Mobile Computing》2016,16(9):1065-1077
In this paper, we propose an analytical model for estimating the irreducible bit error ratio (BER) in multipath channel with small‐extent delay dispersion, such as indoor, where the signal‐to‐noise ratio is high, implying dominance of inter‐symbol interference as error‐generating mechanism. Both channel and overall orthogonal frequency‐division multiplexing (OFDM) symbols are modeled stochastically, resulting with novel expression for the residual BER prediction that is shown to analytically distinguish power delay profiles with equal delay spreads but having different profile shapes. In addition, the model could simply accommodate insertion of cyclic prefix onto the OFDM symbol, providing a means for either testing adequacy of any applied (standard) cyclic prefix length or finding its optimal value as a compromise between the performance enhancement achieved by inserting cyclic prefix and the consequently added redundancy. Finally, the model was modified as to include the analysis of effects of subcarrier frequency inaccuracy or Doppler shift, by adding additional equivalent delay dispersion with equal effect on BER degradation, while considering the system virtually free of carrier frequency offset. All analytically achieved results and conclusions are tested and successfully verified by conducted extensive Monte Carlo simulations. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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为了减小正交频分复用系统受频率偏差的影响,本文提出了基于循环前缀的频偏自适应跟踪算法,该算法利用循环前缀,对载波频偏进行跟踪.文中用最陡下降法和变步长自适应算法进行了计算机仿真,给出了频偏跟踪曲线和BPSK的星座图.理论分析和仿真结果表明,本文提出的方法运算复杂度低,并具有较好的收敛性,能够改善解调性能. 相似文献