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1.
Combinatorial analysis of the minimum distance of turbo codes 总被引:2,自引:0,他引:2
Breiling M. Huber J.B. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2001,47(7):2737-2750
In this paper, new upper bounds on the maximum attainable minimum Hamming distance of turbo codes with arbitrary-including the best-interleavers are established using a combinatorial approach. These upper bounds depend on the interleaver length, the code rate, and the scramblers employed in the encoder. Examples of the new bounds for particular turbo codes are given and discussed. The new bounds are tighter than all existing ones and prove that the minimum Hamming distance of turbo codes cannot asymptotically grow at a rate more than the third root of the codeword length 相似文献
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Interleaver design for turbo codes 总被引:6,自引:0,他引:6
Sadjadpour H.R. Sloane N.J.A. Salehi M. Nebe G. 《Selected Areas in Communications, IEEE Journal on》2001,19(5):831-837
The performance of a turbo code with short block length depends critically on the interleaver design. There are two major criteria in the design of an interleaver: the distance spectrum of the code and the correlation between the information input data and the soft output of each decoder corresponding to its parity bits. This paper describes a new interleaver design for turbo codes with short block length based on these two criteria. A deterministic interleaver suitable for turbo codes is also described. Simulation results compare the new interleaver design to different existing interleavers 相似文献
3.
Alvarado A. Agrell E. Szczecinski L. Svensson A. 《Communications, IEEE Transactions on》2010,58(2):500-510
In this paper we formally analyze the interleaver and code design for QAM-based BICM transmissions using the binary reflected Gray code. We develop analytical bounds on the bit error rate and we use them to predict the performance of BICM when unequal error protection (UEP) is introduced by the constellation labeling. Based on these bounds the optimum design of interleaver and code is found, and numerical results for representative configurations are presented. When the new design is used, the improvements may reach 2 dB, and they are obtained without any increase on the transceiver?s complexity. We also introduce the concept of generalized optimum distance spectrum convolutional codes, which are the optimum codes for QAM-based BICM transmissions. 相似文献
4.
Serial concatenation of interleaved codes: performance analysis,design, and iterative decoding 总被引:24,自引:0,他引:24
Benedetto S. Divsalar D. Montorsi G. Pollara F. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1998,44(3):909-926
A serially concatenated code with interleaver consists of the cascade of an outer encoder, an interleaver permuting the outer codewords bits, and an inner encoder whose input words are the permuted outer codewords. The construction can be generalized to h cascaded encoders separated by h-1 interleavers. We obtain upper bounds to the average maximum-likelihood bit error probability of serially concatenated block and convolutional coding schemes. Then, we derive design guidelines for the outer and inner encoders that maximize the interleaver gain and the asymptotic slope of the error probability curves. Finally, we propose a new, low-complexity iterative decoding algorithm. Throughout the paper, extensive comparisons with parallel concatenated convolutional codes known as “turbo codes” are performed, showing that the new scheme can offer superior performance 相似文献
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Sason I. Shamai S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2000,46(1):24-47
The ensemble performance of parallel and serial concatenated turbo codes is considered, where the ensemble is generated by a uniform choice of the interleaver and of the component codes taken from the set of time-varying recursive systematic convolutional codes. Following the derivation of the input-output weight enumeration functions of the ensembles of random parallel and serial concatenated turbo codes, the tangential sphere upper bound is employed to provide improved upper bounds on the block and bit error probabilities of these ensembles of codes for the binary-input additive white Gaussian noise (AWGN) channel, based on coherent detection of equi-energy antipodal signals and maximum-likelihood decoding. The influence of the interleaver length and the memory length of the component codes is investigated. The improved bounding technique proposed here is compared to the conventional union bound and to a alternative bounding technique by Duman and Salehi (1998) which incorporates modified Gallager bounds. The advantage of the derived bounds is demonstrated for a variety of parallel and serial concatenated coding schemes with either fixed or random recursive systematic convolutional component codes, and it is especially pronounced in the region exceeding the cutoff rate, where the performance of turbo codes is most appealing. These upper bounds are also compared to simulation results of the iterative decoding algorithm 相似文献
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Benedetto S. Divsalar D. Montorsi G. Pollara F. 《Selected Areas in Communications, IEEE Journal on》1998,16(2):231-244
A double serially concatenated code with two interleavers consists of the cascade of an outer encoder, an interleaver permuting the outer codeword bits, a middle encoder, another interleaver permuting the middle codeword bits, and an inner encoder whose input words are the permuted middle codewords. The construction can be generalized to h cascaded encoders separated by h-1 interleavers, where h>3. We obtain upper bounds to the average maximum likelihood bit-error probability of double serially concatenated block and convolutional coding schemes. Then, we derive design guidelines for the outer, middle, and inner codes that maximize the interleaver gain and the asymptotic slope of the error probability curves. Finally, we propose a low-complexity iterative decoding algorithm. Comparisons with parallel concatenated convolutional codes, known as “turbo codes”, and with the proposed serially concatenated convolutional codes are also presented, showing that in some cases, the new schemes offer better performance 相似文献
10.
We consider short frame turbo codes, suitable for delay-sensitive services such as conversational speech, or for encoding single ATM cells. We compare the uniform interleaver bound of Benedetto and Montorsi, and a union bound obtained by estimating the weight distribution due to the actual pseudo-random interleaver, with the simulated BER using an iterative decoder. We show that the uniform interleaver bound is significantly pessimistic at high SNR, where the random interleaver union bound is quite close. However, at lower SNR the ber exceeds the union bound, showing that it does not achieve ml decoding. We also consider half rate turbo codes formed by puncturing various proportions of the data and parity sequences, and adapt the uniform interleaver bounds for these codes. We show that while the union bounds predict better performance for data-punctured codes, in practice they perform better only at high snr and for limited proportions of data puncturing. 相似文献
11.
Turbo-codes have been hailed as the ultimate step toward achieving the capacity limit Shannon established some 50 years ago. We look at the performance of turbo-codes with respect to various information theoretic error bounds. This comparison suggests that, if (block, or) frame error rates are considered, careful interleaver design is necessary to ensure an error performance within a fraction of a decibel of the theoretical limit for large block sizes, while random interleavers perform well for block sizes smaller than about 2 K. If the bit error performance is considered, interleaver design seems to have only a minor effect, and the codes perform close to the limit for all block sizes considered 相似文献
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Contention-Free Interleavers for High-Throughput Turbo Decoding 总被引:1,自引:0,他引:1
Nimbalker A. Blankenship T.K. Classon B. Fuja T.E. Costello D.J. 《Communications, IEEE Transactions on》2008,56(8):1258-1267
13.
Combined turbo codes and interleaver design 总被引:1,自引:0,他引:1
The impact of the distance spectrum and interleaver structure on the bit error probability of turbo codes is considered. A new turbo code design method for Gaussian channels is presented. The proposed method combines a search for good component codes with interleaver design. The optimal distance spectrum is used as the design criterion to construct good turbo component codes at low signal-to-noise ratios (SNRs). In addition, an interleaver design method is proposed. This design improves the code performance at high SNR. Search for good component codes at low SNR is combined with a code matched interleaver design. This results in new turbo codes with a superior error performance relative to the best known codes at both low and high SNR. The performance is verified by both analysis and simulation 相似文献
14.
This paper investigates the combination of a new block interleaver design and a noniterative decision feedback receiver/decoder for IS-95 code-division multiple-access (CDMA) uplink in additive white Gaussian noise and a Rayleigh fading multipath environment. The new interleaver design yields better performance than the currently used IS-95 interleaver, with Eb/N0 improvements of 0.27 to 0.76 dB. At the same time, the new interleaver design improves the effectiveness of a noniterative decision feedback receiver/decoder herein presented. The performance of the proposed design is measured via computer simulation for both coherent and noncoherent detection. A mathematical justification is also given to show the reason why the performance is improved using the proposed design. Based on these results, it is concluded that the use of the new interleaver design with noniterative decision feedback decoding can improve the quality of service and/or capacity of a modified cellular IS-95 system or a system using a similar concatenation of convolutional coding, interleaving, and orthogonal Walsh modulation. Although the approach presented is applied to the uplink of IS-95, it can also be applied to similar M-ary systems 相似文献
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Orhan Gazi 《Wireless Personal Communications》2012,65(3):555-566
In this article we introduce a new collision free prunable random interleaver. The suggested interleaver is a joint structure involving rectangular and S-random interleaver. It comprises a general model for all kind of collision free prunable random interleavers. In addition, it can be designed for any number of parallel processors and any length of information sequence vector and can be considered also as a template for collision free prunable interleavers. The proposed interleaver can be used with all kind of turbo-like codes. The performance of the proposed interleaver is measured with parallel decodable serially concatenated convolutional codes (PDSCCCs) and compared to the PDSCCCs?? performance with collision full S-random interleaver. 相似文献
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低信噪比下随机交织器识别 总被引:1,自引:0,他引:1
针对Turbo码随机交织器参数识别问题,充分利用信道截获数据的软判决信息,提出了一种基于对数符合度的交织映射关系识别算法。该算法从计算总的编码方程成立概率出发,定义了能很好衡量概率大小的对数符合度概念,极大地简化了计算复杂度,使得计算量仅与截获码块数目和交织长度的平方有关,计算方式仅为大小比较与符号提取;再利用正确交织位置能够使总的编码方程成立的概率达到最大这一特性,依次实现各个位置的交织关系的识别。与现有算法相比,所提算法识别性能稍差,但计算复杂度更低。仿真结果表明,在信噪比为0 dB、交织长度为200时,仅需要截获码块数目为500,其正确识别率就能达到100%。 相似文献
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Turbo码是一种新的纠错码,具有十分突出的纠错能力。Turbo码编码器由两个或两个以上的分量码编码器和交织器并行级联而成。S.Benedetto和G.Montersi(1996)中提出了设计Turbo码的新参数有效自由距离d2(Effective Free Distance)。D.Divsalar和R.J.McEliece(1996)给出了有效自由距离的两个上限,但未给出证明。本文从理论上对d2的两个上限进行证明。 相似文献
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This letter considers the decoding of the IS-95(A) uplink code in an effort to assess its best achievable performance. Union bounds on the bit error probability for the IS-95(A) indicate that the interleaver affects significantly system performance. Computer simulation results for iterative decoding show that performance gains in the order of 0.6 dB can be obtained when the sequential interleaver is replaced by a pseudorandom interleaver of same size. Improving iterative decoding for this code while maintaining the original sequential interleaver, results only in minor performance gains over published results 相似文献
20.
A novel all-fiber optical interleaver with flat-top passband 总被引:1,自引:0,他引:1
Huai Wei Lu Bao Ge Zhang Min Zhi Li Guan Wei Luo 《Photonics Technology Letters, IEEE》2006,18(13):1469-1471
An all-fiber optical interleaver with almost rectangular wavelength response is developed by using a new configuration. The device consists of a 2/spl times/2 and a 3/spl times/3 directional fiber coupler. Based on the digital approximation method of Fourier series, the relationships among the splitting ratios of the couplers, the length difference of interference arms, and the intensity transmission spectrum are analyzed. The results indicate that a uniform flattop spectral response can be obtained by the configuration when the length difference of interference arms and the coupling coefficient of the couplers, with some certain values, are given. The passband and stopband of optical interleaver are improved remarkably. The coupling ratio of couplers and the proportion of the length differences can be controlled accurately in the course of fabricating the interleaver. A novel structure of an interleaver is fabricated by using the fused biconical taper technics in experiment. The experimental results are in good agreement with the analytical ones. 相似文献