一种简单的Turbo码的迭代停止判据

Turbo码提出之后,由于其优异的性能成为研究热点。但为了得到其优异的性能,在译码过程中需要进行多次迭代,这造成巨大的译码延时。在不影响性能的情况下,为减少译码延时,迭代停止在Turbo码迭代译码过程中十分重要。提出一种基于似然比绝对值大于某一门限的比特数目的迭代停止判据。并且给出平均迭代次数、译码性能的仿真。仿真结果证明该算法的有效性。     

新的turbo迭代译码停止判据

根据turbo迭代译码算法的一动态系统的观点,本文提出了一种新的迭代译码停止判据,根据该判据进行turbo译码时,平均迭代次数减少,同时,所获得的性能没有降低。     

一种用于cdna2000的新的Turbo码迭代译码方案

由于Ｔｕｒｂｏ码优异的纠错性能使得其在第三代移动通信（３Ｇ）系统中倍受重视。无论是ＷＣＤＭＡ还是ｃｄｍａ２０００都将其作为侯选的信道编码方案，并且将其列为３Ｇ的核心技术之一。本文将ｃｄｍａ２０００中的Ｔｕｒｂｏ码和同等译码复杂度的卷积码进行比较，给出了在加性白高斯噪声信道和瑞利衰落信道中的仿真结果。     

Turbo码译码算法的迭代准则

仿真分析了迭代次数对Turbo编码性能的影响,包括对误比特率(BER)和误帧率(FER)的影响.并通过对附加信息的距离变化进行度量,提出了一种新的迭代停止判断准则,这种准则能动态地选择迭代次数.     

Turbo码中迭代译码的迭代终止准则研究

本文介绍了Turbo码中迭代译码的两种新的迭代终止准则,并通过仿真研究了这两种迭代终止准则的性能。这两种迭代终止准则都是基于互熵（CE）的概念,但是后一种比CE准则更简单,具有更低的计算复杂度。     

一种简单的Turbo码迭代译码判据

针对Turbo码系统译码复杂度大、系统延时较大的缺点,我们主要分析了系统延时的原因和现有的迭代判据,并用符号变化比作为迭代提前结束的判据,实现了降低译码复杂度和译码延时的目的.通过仿真比较了它与其它判据的优缺点.     

Turbo码译码性能与循环迭代次数探讨

Turbo码中独有的循环迭代结构是Turbo码具有良好的译码性能的一个重要原因。本文重点探讨了循环迭代次数对Turbo码译码性能的影响。并对探讨结果进行了计算机仿真 ,模拟出信噪比 -误比特率曲线。     

一种新的迭代终止判决标准

提出用输入信息(外信息)或输出信息所含信息量来作为迭代终止判决标准。并分析了采用这种迭代终止判决标准后,译码器在不同条件下的性能。模拟计算表明采用这种判决方法后,译码性能几乎不变,迭代次数却减少了。     

Turbo码的译码算法

介绍了Turbo码的基本概念,详细推导了最大后验译码算法(MAP)、对数最大后验译码算法(LOG-MAP)、最大对数后验译码算法(MAX-LOG-MAP)以及软输出Viterbi算法(SOVA),利用上述算法对分量码进行译码,然后进行迭代,可以逼近最大似然译码。     

Turbo码的改进译码方法

本文在Turbo码的常用迭代译码方法的基础上加以改进,引入迭代步进因子以改善迭代译码的收敛特性,论文还给出了迭代步进因子的产生方法并进行了计算机仿真.     

A simple stopping criterion for turbo decoding

This article proposes a simple stopping criterion for turbo decoding that extends the existing sign change ratio (SCR) technique. The new sign difference ratio (SDR) criterion counts the sign differences between the a priori information and the extrinsic information. Unlike the SCR, it requires no extra data storage. Simulations comparing the new technique with other well known stopping criteria show that the proposed SDR scheme achieves similar performance in terms of the bit error rate (BER), frame error rate (FER), and the average number of iterations, while requiring lower complexity. A GENIE scheme is included as the limit of all possible stopping criteria     

Simple stopping criterion for turbo decoding

A simple and effective criterion for stopping the iteration process in turbo decoding with negligible degradation of the error performance is presented. The new, improved hard-decision-aided (IHDA) extends the existing hard-decision-aided (HDA). Unlike the HDA, it requires no extra data storage, while achieving similar performance in terms of the BER and average number of iterations     

A turbo code interleaver design criterion based on the performanceof iterative decoding

The performance of a turbo code is dependent on two code properties: its distance spectrum and its suitability to be iteratively decoded. Both these properties are influenced by the choice of interleaver used in the turbo encoder. This paper presents an interleaver design criterion that focuses on the performance of iterative decoding, based on the correlation properties of the extrinsic inputs. Interleavers designed with the proposed criterion achieve very competitive performances, both in terms of convergence rates and error correcting capabilities     

Bit-level stopping of turbo decoding

With iterative turbo decoding, the reliability of each bit in a frame converges at a different speed, i.e. some bits converge faster than others. This motivates us to propose a bit-level stopping scheme that prevents unnecessary iterations for those bits having already reached a satisfactory degree of reliability. Simulation results show that the proposed bit-level stopping can reduce up to 1/2 iteration when compared to the conventional frame-level stopping criteria while achieving the same bit error rate.     

Two simple stopping criteria for turbo decoding

This paper presents two simple and effective criteria for stopping the iteration process in turbo decoding with a negligible degradation of the error performance. Both criteria are devised based on the cross-entropy (CE) concept. They are as efficient as the CE criterion, but require much less and simpler computations     

Noncoherent iterative (turbo) decoding

Previously, noncoherent sequence detection schemes for coded linear and continuous phase modulations have been proposed, which deliver hard decisions by means of a Viterbi algorithm. The current trend in digital transmission systems toward iterative decoding algorithms motivates an extension of these schemes. In this paper, we propose two noncoherent soft-output decoding algorithms. The first solution has a structure similar to that of the well-known algorithm by Bahl et al. (1974), whereas the second is based on noncoherent sequence detection and a reduced-state soft-output Viterbi algorithm. Applications to the combined detection and decoding of differential or convolutional codes are considered. Further applications to noncoherent iterative decoding of turbo codes and serially concatenated interleaved codes are also considered. The proposed noncoherent detection schemes exhibit moderate performance loss with respect to corresponding coherent schemes and are very robust to phase and frequency instabilities     

Soft multiuser demodulation and iterative decoding for FH/SSMA with a block turbo code

The number of users that can be supported by frequency-hopped, spread-spectrum multiple-access systems can be increased greatly by using multiuser demodulation and iterative decoding. In the receiver employed hard-decision multiuser demodulation followed by iterative decoding, users exchange decoded information with each other. Additional information from multiuser demodulation in the first decoding iteration is limited by the hard-decision output of the multiuser demodulator. The error-correction used was an errors-and-erasures Reed-Solomon (RS) decoder. We revisit hard-decision demodulation and conventional RS decoding. Hard-decision multiuser demodulation is modified to provide a soft output, which is then given to a nonbinary block turbo code with shortened RS codes as the constituent codes. An iterative multiuser decoding algorithm is developed to do soft multiuser interference cancellation. This soft receiver with soft demodulation and decoding is shown to be more resistant to multiuser interference and channel noise, especially at lower values of signal-to-noise ratio. The results show a great improvement in the ability of the system to support more users (more than three times in some cases), as compared with systems that erase all hits or employ hard-decision multiuser demodulation followed by RS code. We examine the proposed method for synchronous as well as asynchronous frequency-hopped systems in both AWGN and fading channels.