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Turbo码译码的改进SOVA算法 总被引:1,自引:0,他引:1
Turbo编码自1993年提出以来,由于其出色的译码性能,在编码界得了广泛关注,逐渐被吸纳到一些标准化体系中,对于Turbo码的译码问题,目前已有许多种译码算法,在传统SOVA(软输出维特比算法)译码算法的基础上,给出了一种SOVA译码的改进算法,仿真结果表明该算法在译码性能等方面具有较强的优越性。 相似文献
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Turbo码是一种新的纠错编码,具有十分强的纠错能力,Turbo码编码端采用两个或两个以上的卷积并行级联构成,译码端则采用以基于软判决信息输入/输出的反馈迭代译码结构。译码算法是Turbo码设计的核心,现巳有的两种主要的译码算法-MAP和SOVA。SOVA是一种改进的维持比算法,使其可以逐比特输出与MAP算法类似的软判决信息。该文综述了Turbo码SOVA译码的几种改进方式,并分析了这几种改进方式及仿真结果。 相似文献
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Turbo码是一种新的纠错编码,具有十分强的纠错能力。Turbo码编码端采用两个或两个以上的卷积并行级联构成,译码端则采用以基于软判决信息输入/输出的反馈迭代译码结构。译码算法是Turbo码设计的核心,现已有的两种主要的译码算法——MAP和SOVA。SOVA是一种改进的维特比算法,使其可以逐比特输出与MAP算法类似的软判决信息。该文综述了Turbo码SOVA译码的几种改进方式,并分析了这几种改进方式及仿真结果。 相似文献
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Turbo码是一种新的纠错编码,具有十分强的纠错能力。Turbo码编码端采用两个或两个以上的卷积并行级联构成,译码端则采用以基于软判决信息输入/输出的反馈迭代译码结构。译码算法是Turbo码设计的核心,现已有的两种主要的译码算法——MAP和SOVA。SOVA是一种改进的维特比算法,使其可以逐比特输出与MAP算法类似的软判决信息。该文综述了Turbo码SOVA译码的几种改进方式,并分析了这几种改进方式及仿真结果。 相似文献
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The performance of parallel and serial concatenated codes on frequency-nonselective fading channels is considered. The analytical average upper bounds of the code performance over Rician channels with independent fading are derived. Furthermore, the log-likelihood ratios and extrinsic information for maximum a posteriori (MAP) probability and soft-output Viterbi algorithm (SOVA) decoding methods on fading channels are developed. The derived upper bounds are evaluated and compared to the simulated bit-error rates over independent fading channels. The performance of parallel and serial codes with MAP and SOVA iterative decoding methods, with and without channel state information, is evaluated by simulation over independent and correlated fading channels. It is shown that, on correlated fading channels, the serial concatenated codes perform better than parallel concatenated codes. Furthermore, it has been demonstrated that the SOVA decoder has almost the same performance as the MAP decoder if ideal channel state information is used on correlated Rayleigh fading channels. 相似文献
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The iterative decoding in turbo code has very high decoding complexity. This paper adopts the improved Log-MAP algorithm for
decoding of Space-Time Turbo Trellis Code (ST-Turbo TC) in the slow Rayleigh fading channels. Using the MacLaurin formulae,
the proposed algorithm expands the logarithmic function of the Log-MAP. It makes the computation much easier and the operation
of the hardware system much faster. Simulation results show that the proposed algorithm performs very closely to the Log-MAP
algorithm for decoding of ST-Turbo TC in slow Rayleigh fading channels. 相似文献
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Salim Kahveci 《Telecommunication Systems》2012,49(4):345-353
This study introduces a new low complexity Max-Log-MAP based channel estimation technique operating in a multi-path band limited
channel. The proposed estimation technique is based on an iterative procedure derived through the maximum a posteriori probability
approach. Wireless communication channels often undergo frequency selective fading that leads to inter-symbol interference,
which limits the performance of wireless indoor systems. Performance of the algorithms is assessed by combined analysis and
simulation. Results are presented and compared against the performance of conventional Log-MAP algorithm. The obtained results
show that the required bit-error-rate performance can be achieved with a lower number of iterations using the proposed low
complexity algorithm compared to using the conventional Log-MAP algorithm. 相似文献
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本文对非规则LDPC码在RICE信道的性能进行了分析和仿真,修正了BP译码算法,证明了RICE信道满足对称性,给出了RICE信道译码稳定性条件,推导出了RICE信道的Shannon容量限,采用VC编程对码长N=49512和3072进行了仿真,同时与同码长的Turbo码进行了比较;仿真结果表明LDPC码在码长N=49512、码率R=1/3时,与Shannon限相差1dB以内、在低信噪比时其性能优于Turbo码,以及LDPC码本身有很好的交织特性和抗衰落的能力;这进一步表明了LDPC码在包括RICE信道在内的各种信道中的性能都是非常优良的. 相似文献
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In this paper, we propose a novel and simple approach for dealing with the exaggerated extrinsic information produced by the soft-output Viterbi algorithm (SOVA). The proposed remedy is based on mathematical analysis and it involves using two attenuators, one applied to the immediate output of the SOVA and another applied to the extrinsic information before it is passed to the other decoder (assuming iterative decoding). The use of these attenuators aims at reducing the inherent strong correlation between the intrinsic information (input to the SOVA) and extrinsic information (output of the SOVA). We examine the modified SOVA (MSOVA) on additive white Gaussian noise (AWGN) and flat fading channels for parallel concatenated codes (PCCs) and serial concatenated codes (SCCs). We show that the MSOVA provides substantial performance improvements over both channels. For example, it provides improvements of about 0.8 to 1.0 dB at P/sub b/ = 10/sup -5/ in AWGN, and about 1.4 to 2.0 dB at P/sub b/ = 10/sup -5/ on fading channels. We also show that there are cases where the MSOVA is superior to the a posteriori probability (APP) algorithm. With this motivation, we extend the proposed modification to the APP algorithm with favorable results. We demonstrate that the modified APP (MAPP) provides performance improvements between 0.3 to 0.6 dB at P/sub b/ = 10/sup -5/ relative to the APP. We lastly mention that the proposed modifications, while they provide considerable performance improvements, keep the complexity of these decoders almost the same, which is remarkable. 相似文献
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Vidhyacharan Bhaskar 《International Journal of Wireless Information Networks》2005,12(3):159-168
In this paper, a detailed theoretical analysis of fading margin in an asynchronous code division multiple access (A-CDMA) system is discussed. Rayleigh and Rician frequency-selective slowly fading channels are considered. Probability distribution and density functions of the probability of error are derived for Rayleigh and Rician fading channels. The fluctuations in the channel capacity are proved to be directly proportional to the signal-to-noise ratio (SNR) variations. Fading margin is calculated for both Rayleigh and Rician fading channels as a function of the probability of error specification and the probability of unsatisfactory operation. 相似文献
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In this paper, the performance of space time‐turbo trellis coded modulation (ST‐TTCM) is evaluated over Rician and Rayleigh fading channels with imperfect phase. We modify Baum–Welch (BW) algorithm to estimate the fading and phase jitter parameters for multi‐antenna configurations. Thus, we assume that the channel parameters change slower than carrier frequency. We know that, at high data rate transmissions over wireless fading channels, space–time block codes (STBC) provide the maximal possible diversity advantage. Here, the combined effects of the amplitude and the phase of the received signal are considered, each one modelled by Rician and Tikhonov distributions, respectively. We investigate space time‐turbo trellis coded modulation (ST‐TTCM) for 8‐PSK for several Rician factor K and phase distortion factor η. Thus, our results reflect the degradations both due to the effects of the fading on the amplitude and phase noise of the received signal while the channel parameters are estimated by BW algorithm. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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A new exact explicit expression is derived for the ergodic capacity of maximal ratio combining (MRC) schemes over arbitrarily correlated Rician fading channels. This is used to study the effects of channel correlation on the ergodic capacity. Numerical results reveal that both the phase and the magnitude of correlation have an impact on the ergodic capacity of Rician fading channels. This is in contrast to correlated Rayleigh fading, where the phase of the correlation has no effect on the ergodic capacity. It is also observed that negatively correlated branches in Rician fading may lead to an increase in ergodic capacity beyond that obtained by uncorrelated branches. 相似文献
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Performance Analysis of the Dual-Hop Asymmetric Fading Channel 总被引:2,自引:0,他引:2
Suraweera H.A. Karagiannidis G.K. Smith P.J. 《Wireless Communications, IEEE Transactions on》2009,8(6):2783-2788
In real wireless communication environments, it is highly likely that different channels associated with a relay network could experience different fading phenomena. In this paper, we investigate the end-to-end performance of a dualhop fixed gain relaying system when the source-relay and the relay-destination channels experience Rayleigh/Rician and Rician/Rayleigh fading scenarios respectively. Analytical expressions for the cumulative distribution function of the end-to-end signal-to-noise ratio are derived and used to evaluate the outage probability and the average bit error probability of M-QAM modulations. Numerical and simulation results are presented to illustrate the impact of the Rician factor on the end-toend performance. Furthermore, these results confirm that the system exhibits an improved performance in a Rician/Rayleigh (source-relay link/relay-destination link) environment compared to a Rayleigh/Rician environment. 相似文献