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交织器的引入使Turbo码对不同信息位具有明显的不等保护特性,从而对其性能产生影响。为了提高Turbo码译码性能,在给定的S距离伪随机交织器下,首先通过对多组随机输入信息序列的位误比特率仿真分析,找到对Turb0码性能影响较大的关键比特位置,然后在对Turbo码不等保护特性和已知比特Turbo码进行理论分析和研究的基础上,提出了关键比特不等保护和结合已知比特的Turbo码不等保护两种方案。最后,对提出的方案进行了仿真验证,结果表明在交织长度分别为200和400两种条件下,两种保护方案在高信噪比时与未保护相比均有0.2dB以上增益.且结合已知比特的Turbo码不等保护方案比关键比特保护方案性能更优。 相似文献
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在介绍Turbo编码、译码原理的基础上,建立一个典型BPSK通信系统模型,将Turbo码与其它编码方式分别运用于该系统模型,通过Matlab仿真,研究、分析了系统在不同编译码方式下的误比特性能,最后给出结论。 相似文献
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基于对Turbo编码器输出的系统比特和校验比特的不等错误保护(UEP),提出了一种新的比特交织Turbo编码调制(BITCM)的8PSK符号映射方案,即对于码率为1/3的Turbo码,校验比特映射到8PSK星座点中具有较好传输性能的比特位置上,而系统比特映射到较差传输性能的比特位置上。实现新映射方案的关键是比特交织器的设计。仿真结果表明,新的映射方案在AWGN信道下,误码率为10-3时,可获得大于0.2dB的信噪比增益,而这一增益的获得并没有牺牲频谱效率和增加系统的复杂性。 相似文献
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Turbo码具有逼近Shannon容量限的优异性能,介绍了应用于深空通信的Turbo码编码方案和相应的译码算法,并给出了采用修正Max-Log-Map译码算法的深空CCSDS标准Turbo码的软件仿真性能和硬件系统实测性能。通过计算机仿真和硬件实测结果表明,采用该修正Max-Log-Map译码算法的Turbo码译码器易于硬件实现,同时Turbo码仿真性能和实际性能一致,适用于实际工程应用。 相似文献
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介绍了一种短Turbo码交织器的设计方法 ,给出了一个短交织器的设计例子 ,其仿真结果表明 ,这种交织器对于短Turbo码很有效。在Turbo码帧长度处于 10 0到 10 0 0时 ,与Turbo码使用块交织和伪随机交织相比 ,误码性能有了大幅度的提高。 相似文献
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本文通过调整迭代解码过程中系统位接收值的加权系数,提出了一种Turbo码加权迭代解码算法。该算法改变了迭代运算后Turbo码解码器输出软值中系统位接收值信息和它的外部估计信息的比重,使Turbo码无论在低信噪比或是在高信噪比时均具有优良的纠错性能。仿真结果显示,采用Turbo码加权迭代解码算法,不仅能提高Turbo码的收敛速度,而且能进一步降低Turbo码解码时的地板值,使Turbo码的比特误码率在高、低信噪比时都能够得到进一步改善。 相似文献
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一种新颖的Turbo码MAP译码器 总被引:3,自引:0,他引:3
根据Turbo码trellis结束的情况及Turbo码的特征本文提出了一种新的Turbo码MAP译码器。这是基于MAP译码器中两个组成译码器性能的不一致所作改进,从分析和仿真结果我们可以看到该方法的优势。 相似文献
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在LTE中,为了获得正确无误的数据传输,要采用差错控制编码技术。LTE中是采用Viterbi和Turbo加速器来实现前向纠错。咬尾卷积码保证格形起始和终止于某个相同的状态,它具有不要求传输任何额外比特的优点。本文提出一种在FPGA中实现的咬尾卷积码的Viterbi译码算法,并在Xilinx的XC3S500E芯片上实现了该算法,最后对该算法性能进行了分析。 相似文献
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This paper investigates the incidence of trellis termination on the performance of turbo codes and accounts for the performance degradation often experienced in the absence of trellis termination. Analytical upper bounds on the performance for the ensemble of turbo codes using different trellis termination strategies as well as performance results obtained by computer simulation are presented. In the case of uniform interleaving, the performance differences between various termination methods are relatively small, except when using no trellis termination at all. 相似文献
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Hokfelt J. Edfors O. Maseng T. 《Selected Areas in Communications, IEEE Journal on》2001,19(5):838-847
The performance of a turbo code can be severely degraded if no trellis termination is employed. This paper investigates the implications of the choice of trellis termination method for turbo codes, and explains the origin of the performance degradation often experienced without trellis termination. An efficient method to derive the distance spectrum of turbo codes for different trellis termination methods is presented. Further, we present interleaver design rules that are tailored to each termination method. Using interleavers designed with these restrictions, we demonstrate that the performance difference between various termination methods is very small, including no trellis termination at all. For example, we demonstrate a turbo code with a 500-bit interleaver that exhibits no sign of an error floor for frame error rates as low as 10-8, even though no trellis termination is employed 相似文献
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In this letter we define and evaluate the average maximum-likelihood performance of the three ways of co-decoding turbo codes. In all cases the information sequence is split into blocks of N bits (N being the length of the interleaver used by the turbo code), that are encoded by the first constituent encoder and, after interleaving, by the second encoder. In the first operation mode, both constituent encoders work in a continuous fashion, whereas in the second, at the end of each block, a suitably chosen sequence of bits is appended to the information block in order to terminate the trellises of both constituent codes. In the third mode, the operation is similar to the second, but, instead of trellis termination, both constituent encoders are simply reset 相似文献
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van Dijk M. Egner S. Motwani R. Koppelaar A.G.C. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(9):2236-2241
In a parallel concatenated convolutional code, an information sequence is encoded by a convolutional encoder, and an interleaved version of the information sequence is encoded by another convolutional encoder. We discuss the situation in which we require both convolutional encoders to end in the all-zero state. To do so, we have to split an information word in two parts. One part contains the true information bits, and the second part contains the so-called tail bits, which are special bits with values computed such that both encoders end in the all-zero state. Depending on the interleaver, a different number of tail bits are needed. By using a constructive method, we give a characterization of all interleavers for a prescribed number of tail bits. We explain the method of encoding. In addition, simulations have been carried out to investigate the performance of codes resulting from simultaneous zero-tailing. This shows that simultaneous zero-tailing is similar in performance as compared to previously known zero-tailing methods (but with fewer trellis termination bits) and that it is better than zero-tailing just one of the encoders. 相似文献
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Kaza J. Chakrabarti C. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2004,12(9):968-977
Turbo codes have been chosen in the third generation cellular standard for high-throughput data communication. These codes achieve remarkably low bit error rates at the expense of high-computational complexity. Thus for hand held communication devices, designing energy efficient Turbo decoders is of great importance. In this paper, we present a suite of MAP-based Turbo decoding algorithms with energy-quality tradeoffs for additive white Gaussian noise (AWGN) and fading channels. We derive these algorithms by applying approximation techniques such as pruning the trellis, reducing the number of states, scaling the extrinsic information, applying sliding window, and early termination on the MAP-based algorithm. We show that a combination of these techniques can result in energy savings of 53.2%(50.0%) on a general purpose processor and energy savings of 80.66%(80.81%) on a hardware implementation for AWGN (fading) channels if a drop of 0.35 dB in SNR can be tolerated, at a bit error rate (BER) of 10/sup -5/. We also propose an adaptive Turbo decoding technique that is suitable for low power operation in noisy environments. 相似文献