ISSN:1124-318X    

DOI:10.1002/ett.4460060502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460060503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460060504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460060505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents a receiving scheme intended to combat the detrimental effects of intersymbol interference for digital transmissions protected by convolutional codes. The receiver performs two successive soft‐output decisions, achieved by a symbol detector and a channel decoder, through an iterative process. At each iteration, extrinsic information is extracted from the detection and decoding steps and is then used at the next iteration as in turbo‐decoding. From the implementation point of view, the receiver can be structured in a modular way and its performance, in bit error rate terms, is directly related to the number of modules used. Simulation results are presented for transmissions on Gauss and Rayleigh channels. The results obtained show that turbo‐equalization manages to overcome multipath effects, totally on Gauss channels, and partially but still satisfactorily on Rayleigh cha

ISSN:1124-318X    

DOI:10.1002/ett.4460060506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA general framework, based on ideas of Tanner, for the description of codes and iterative decoding (“turbo coding”) is developed. Just like trellis‐based code descriptions are naturally matched to Viterbi decoding, code descriptions based on Tanner graphs (which may be viewed as generalized trellises) are naturally matched to iterative decoding. Two basic iterative decoding algorithms (which are versions of the algorithms of Berrou et al. and of Hagenauer, respectively) are shown to be natural generalizations of the forward‐backward algorithm (Bahl et al.) and the Viterbi algorithm, respectively, to arbitrary Tanner graphs. The careful derivation of these algorithms clarifies, in particular, which a priori probabilities are admissible and how they are properly dealt with. For cycle codes (a class of binary linear block codes), a complete characterization is given of the error patterns that are corrected by the generalized Viterbi algorithm after infinitely many ite

ISSN:1124-318X    

DOI:10.1002/ett.4460060507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper we extend the idea of iterative decoding of two‐dimensional systematic convolutional codes ‐ so‐called “turbo” codes ‐ to threshold decoding. A threshold decoding algorithm is presented which uses soft information from the channel and a priori values in order to generate soft outputs. A soft output value can be split into three terms. The first two terms represent the soft input including the a priori value, while the third is called extrinsic value. The extrinsic value is passed on as a priori information to the following decoder. Surprisingly good simulation results were obtained for the Gaussian channel and the fully interleaved slowly Rayleigh fad

ISSN:1124-318X    

DOI:10.1002/ett.4460060508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper a brief overview of the concept of iterative processing is provided. Then a code construction for convolutional codes, that results in a signal structure amenable to iterative processing, is studied. This construction is analogous to product coding for block codes. It is shown that the construction shares a number of properties with die product coding construction, including the property that it is “commutative”. The relationship between the free distance and the interleaving factors is examined, and then exemplified with computer simulation resu

ISSN:1124-318X    

DOI:10.1002/ett.4460060509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAn optimal interleaving between two component encoders of a turbo‐code is proposed. The optimally criterion for any real constructable interleaver is given. For component codes with known weight distribution (WD), the WD of the turbo‐code with optimal interleaving is calculated. Furthermore, a method for approximate calculation of the WD of convolutional code with terminated feed‐forward and feed‐back encoders is proposed. Using this WD's and proposed interleaving, the union upper bounds on the bit error rate of the turbo‐code are given. It is shown that the often observed “break” in the performance curves of turbo‐codes is a result of their “broken” WD. For component codes lying on the Gilbert‐Varshamov bound, an upper bound on the ratio between the minimum distance of the turbo‐code and the component code is determined. The lower bounds on the signal‐to‐noise ratio needed to achieve error free decoding of turbo‐codes with random component coders are given. These bounds are compared with the Shannon limit and anal

ISSN:1124-318X    

DOI:10.1002/ett.4460060510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe recently proposed Turbo codes are applied to bandwidth efficient modulation schemes via multilevel coding. For this purpose, Turbo codes are extended for a wide range of fine tunable rates by puncturing. A straightforward derivation of iterative Turbo decoding and the concept of extrinsic information is presented. New design rules for multilevel codes with arbitrary component codes and codeword lengths are derived from information theory. Simulation results show that application of Turbo codes to properly designed multilevel coding schemes leads to digital transmission schemes with high power and bandwidth efficiency.

ISSN:1124-318X    

DOI:10.1002/ett.4460060511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY