WO1998052329A1 - Dispositif d'egalisation et de decodage pour un canal de transmission numerique selectif en frequence - Google Patents
Dispositif d'egalisation et de decodage pour un canal de transmission numerique selectif en frequence Download PDFInfo
- Publication number
- WO1998052329A1 WO1998052329A1 PCT/FR1998/000951 FR9800951W WO9852329A1 WO 1998052329 A1 WO1998052329 A1 WO 1998052329A1 FR 9800951 W FR9800951 W FR 9800951W WO 9852329 A1 WO9852329 A1 WO 9852329A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- filter
- output
- equalizer
- channel
- symbols
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03178—Arrangements involving sequence estimation techniques
- H04L25/03248—Arrangements for operating in conjunction with other apparatus
- H04L25/03286—Arrangements for operating in conjunction with other apparatus with channel-decoding circuitry
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0047—Decoding adapted to other signal detection operation
- H04L1/005—Iterative decoding, including iteration between signal detection and decoding operation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0054—Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
Definitions
- the present invention relates to an equalization and decoding device for a frequency selective digital transmission channel. PRESENTATION OF THE STATE OF THE TECHNICAL
- a receiver In digital transmission, a receiver can be seen as the cascading of several elementary functions, each function performing a specific processing such as filtering, demodulation, equalization, decoding, etc.
- the processing carried out by an elementary function uses only part of the information made available to it and thus, the overall performance of the receiver is sub-optimal.
- An object of the invention is to remedy this drawback.
- the authors propose a receiver which combines a suitable filter and an interference canceller to suppress the interference between symbols introduced by the frequency selectivity of a channel, without raising the noise level.
- the interference canceller is powered by the decoded symbols (firm decisions), produced beforehand by a receiver constituted by a simple transverse filter.
- the difference compared to the invention lies in the fact that on the one hand, our equalizer is powered by weighted decisions elaborated by a channel decoder and on the other hand, that an iterative processing process is used.
- the receivers described in [1] and [2] have lower performances than the proposed invention. Also, it has been proposed in:
- the device proposed by the invention is more particularly suitable for equalizing the channels having a temporal response spread over a large number of symbols.
- the invention relates to an equalization and decoding device comprising a module which comprises an equalizer and a weighted output decoder, characterized in that it comprises several modules of this type in series, each of which the equalizers minus a transverse filter intended in particular to reduce the noise power and which, for the modules of rank higher strictly than 1, receives a series of samples after the channel and delayed by an amount equal to the processing time of the previous modules.
- the equalizer of the modules of rank strictly higher than 1 comprises another transverse filter which is intended to reconstruct the interference between symbols present at the output of the first filter and which receives the output of the previous module, the output of the equalizer corresponding to the output of the first filter from which is removed the interference between symbols reconstructed by this second filter.
- the transverse filter which receives the series of samples from the channel is a filter which converges towards a suitable filter.
- the device comprises several cascaded modules, each module comprising an equalizer and a weighted output decoder.
- the equalizer of the rank 1 module includes a transverse filter intended to reduce the noise power and the interference between symbols. It receives a series of samples from the demodulator.
- the equalizer of the modules of rank strictly greater than 1 comprises, in a preferred embodiment, two transverse filters.
- the first, adapted to the channel is intended only to reduce the power of the noise and the second, is intended to reconstruct the interference between symbols present at the output of the adapted filter.
- the matched filter receives a series of samples from the demodulator delayed by an amount equal to the processing time of the previous modules, and the second transverse filter is supplied with the result of the average values of the symbols calculated from the output of the decoder. previous module channel.
- the output of the equalizer is equal to the output of the suitable filter to which the interference between symbols is removed. reconstructed by the second filter.
- the equalizer jointly uses the outputs of the demodulator and a channel decoder to try to overcome the interference between symbols introduced by the selectivity of the channel. It takes into account both the characteristics of the transmission channel and the redundancy introduced by the coding function, to carry out its processing. It is then possible to obtain performances analogous to those of an additive noise channel, white, Gaussian, without interference between symbols and with coding.
- the equalizer could also be of the decision type in the loop.
- FIG. 2 schematically illustrates the principle of an iterative structure of a decoding equalization device according to a possible embodiment of one invention
- FIG. 3 schematically shows the structure of a module of the structure illustrated in Figure 2;
- FIG. 4 is a graph on which we have drawn the zeros of the transfer function of the Porat and Friedlander channel;
- FIG. 5 is a graph which gives the error rate after decoding as a function of the Eb / nO ratio and which illustrates the performance of a device of the type shown in Figures 2 and 3 for MDP4 modulation on a channel de Porat and Friedlander;
- FIGS. 2 to 3 are a graph on which the error rate has been plotted after decoding as a function of the ratio Eb / nO, which illustrates the performance of a device of the type shown in FIGS. 2 to 3 for an MAQ-16 modulation on a Porat and Friedlander channel;
- FIGS. 7 and 8 give representations of constellations of signals at the input of the transverse filters of successive modules of a device of the type of that of FIGS. 2 and 3 for modulations respectively of type MDP-4 and MAQ-16 and an Eb / NO ratio respectively equal to 4 dB and 7 dB;
- FIG. 9 is a graph on which the zeros of the transfer function of the Proakis channel have been plotted;
- Figures 10 and 11 are graphs similar to those of Figures 5 and 6 illustrating the performance of a device according to the invention on a Proakis channel for MDP4 modulation and MAQ-16 modulation respectively.
- FIG. 1 illustrates the principle of a chain of transmission of binary data ⁇ k , transmitted by the information source at the rate of a data item every T b seconds. These data ⁇ ⁇ , are coded by a channel coder
- the symbols a n and b n take their value in the set
- the modulator, demodulator, transmission medium, transmission and reception filters assembly is represented in FIG. 1 by an equivalent discrete channel 4, disturbed by an additive noise w n .
- the output r n of the equivalent discrete channel is of the form:
- I (n) are the coefficients, possibly complex of the equivalent discrete channel, assumed to be normalized, these coefficients verifying for example the classical hypothesis:
- the quantities w n are samples of white noise, centered, Gaussian, independent of the symbols d n and of variance ⁇ 2 w .
- transfer function C (f) therefore introduces an interference between symbols whose causal and anti-causal parts relate respectively to L 2 and Li symbols.
- FIG. 2 A block diagram of a device in this sense is represented in FIG. 2.
- a module includes several functions, among which are an equalizer and a channel decoder.
- the input of a module p such that 1 ⁇ p P consists firstly of the samples ⁇ r n ⁇ p _ !
- the equalizer belonging to a module 1 ⁇ p ⁇ P can therefore benefit both from the output of the equivalent discrete channel and from the redundancy introduced by the coder to carry out its processing.
- FIG. 3 illustrates the structure of the elementary module which consists of an equalizer 4, a deinterlacer 5, a binary M-ary converter 6, a channel decoder with weighted output 7, of a function making it possible to evaluate the mean value d n 8 of the symbols d n and of an interleaver 9.
- the equalizer 4 is of the interference canceller type.
- the input of the filter P (f) is made up of the samples ⁇ r n ⁇ p _ ⁇ and that of the filter Q (f) is made of the mean values ⁇ d n ⁇ p _ 1 .
- the filter P (f) which converges, over the iterations towards a filter adapted to the response C (f) of the channel, has (L ⁇ + L 2 +1) coefficients and is used only to reduce the power of the noise w n .
- the theoretical equation of this adapted filter is ⁇ L >
- the theoretical equation of the optimal filter Q (f) is given by: ⁇ _ IL * L
- the output s n of the equalizer is then simply obtained by subtracting the interference y n between symbols reconstructed by the filter Q (f) at the output x n of the filter
- the coefficients of the equalizer filters are adaptively determined, using a stochastic gradient algorithm according to a criterion of the minimum of the quadrative error between the output s n of the equalizer and the decoded data â n .
- symbol interlacing is particularly advantageous.
- it makes it possible to overcome noise at the level of certain metrics, the performance at the output of the decoder then being better than if one is interleaving on binary data.
- interleaving by symbol makes it possible to use a coded trellis modulation.
- the M-ary conversion makes it possible to use a channel decoder whose structure is independent of the number of states of the MAQ-M modulation.
- the 2m samples associated with each sample s n can be obtained by calculating the logarithm of the likelihood ratio (LRV) of the coded data, from the samples s n using the following relation:
- Pr ⁇ c n> 1 - l / s n ⁇ ⁇ (c n ⁇ i ) K log - ⁇ - - 1 i - 1,2 ... 2m
- the samples ⁇ (c a , i) are presented at the input of a weighted output channel decoder, using for example if the coding is of convolutional type a Berrou-Adde algorithm as described in
- ⁇ (c n _ i ) can also be put in the form: ⁇ (c.) ⁇ k ⁇ (c.) + W (c.) (4) where k is a constant equal to 2 in the Berrou-Adde algorithm and W (c nr i) is the extrinsic information associated with the data c nfi . .
- W (c nr i) is the extrinsic information associated with the data c nfi .
- the performance of the device proposed by the invention merges with that of a channel without interference between symbols and with coding, as soon as the signal to noise ratio is greater than 4 dB for MDP-4 modulation and 7 dB for MAQ-16 modulation.
- these signals have a constellation very close to that of an MDP-4 modulation.
- the filter Q (f) is able to reconstruct the interference between symbols present at the output of the filter P (f).
- the device according to the invention makes it possible to completely overcome the frequency selectivity of this channel without, however, raising the noise level, which a decision equalizer in the loop (DFE) controlled by permanence by real data.
- DFE decision equalizer in the loop
- the eleven coefficients I of the channel proposed by Proakis eleven are real and constant.
- the position of the zeros on the unit circle of the transfer function of this channel is shown in Figure 9. [(004; -0.05; 0.07; -0.21; -0.5; 0.72;
- the bit error rate (Teb) has been represented as a function of the ratio E b / N 0 at the output of the turbo-equalizer, for a channel proposed by Proakis respectively for a four-state phase modulation (MDP-4) and an amplitude modulation according to two quadrature carriers in 16 states (MAQ-16).
- MDP-4 four-state phase modulation
- MAQ-16 two quadrature carriers in 16 states
- two iterations are enough for the performances of the turbo-equalizer to merge with those of a channel without interference between symbols and with coding, as soon as the signal to noise ratio is greater than or equal to 2 dB for an MDP modulation. -4 and 6 dB for MAQ modulation. 16.
- the turbo-equalizer always leads to better performance than the decision equalizer in the loop driven by the real data, even if the gain is no more than 0.5 dB, for an error rate of 10-5.
- the device which has just been described advantageously finds application for channels having impulse responses spanning a few tens of symbol durations. Indeed for these channels, it is not possible to use a receiver optimized according to the criterion of maximum likelihood.
- the invention will advantageously find application for transmissions on a radio mobile channel, on a cable channel or even on an underwater acoustic channel. It is applicable to any transmission system using linear modulations such as phase modulation with two or four states (MDP-2, MDP-4 or MAQ-4), amplitude modulations according to one or two carriers in quadrature (MAQ- M).
- linear modulations such as phase modulation with two or four states (MDP-2, MDP-4 or MAQ-4), amplitude modulations according to one or two carriers in quadrature (MAQ- M).
- the coding system may be of the convolutional or block type and the decoder must have a weighted output, that is to say capable of associating reliability information with each decoded symbol.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP54886998A JP4443634B2 (ja) | 1997-05-15 | 1998-05-13 | 周波数選択デジタル伝送チャネルの等化及び復号装置 |
US09/423,994 US6763076B1 (en) | 1997-05-15 | 1998-05-13 | Equalizing and decoding device for a frequency-selective digital transmission channel |
EP98924426A EP0981881B1 (fr) | 1997-05-15 | 1998-05-13 | Dispositif d'egalisation et de decodage pour un canal de transmission numerique selectif en frequence |
DE69804299T DE69804299T2 (de) | 1997-05-15 | 1998-05-13 | Entzerrungs- sowie dekodierungseinrichtung für einen frequenzselektiven kanal zur digitalen übertragung |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR97/05978 | 1997-05-15 | ||
FR9705978A FR2763454B1 (fr) | 1997-05-15 | 1997-05-15 | Dispositif d'egalisation et de decodage pour un canal de transmission numerique selectif en frequence |
Publications (1)
Publication Number | Publication Date |
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WO1998052329A1 true WO1998052329A1 (fr) | 1998-11-19 |
Family
ID=9506927
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/FR1998/000951 WO1998052329A1 (fr) | 1997-05-15 | 1998-05-13 | Dispositif d'egalisation et de decodage pour un canal de transmission numerique selectif en frequence |
Country Status (7)
Country | Link |
---|---|
US (1) | US6763076B1 (fr) |
EP (1) | EP0981881B1 (fr) |
JP (1) | JP4443634B2 (fr) |
CN (1) | CN1112011C (fr) |
DE (1) | DE69804299T2 (fr) |
FR (1) | FR2763454B1 (fr) |
WO (1) | WO1998052329A1 (fr) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011035919A (ja) * | 2002-04-16 | 2011-02-17 | Thomson Licensing | Hdtv受信器用連結等化器/トレリス復号器アーキテクチャ |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
ATE314770T1 (de) * | 2000-08-11 | 2006-01-15 | Mitsubishi Electric Inf Tech | Adaptive entzerrung und dekodierung für gespreizte kanalverzögerung |
FR2822001B1 (fr) * | 2001-03-06 | 2003-06-27 | France Telecom | Dispositif d'egalisation et de decodage de canaux selectifs en frequence |
US7369523B2 (en) * | 2002-02-20 | 2008-05-06 | Texas Instruments Incorporated | Data signal demodulation in a communication system |
AU2005318933B2 (en) | 2004-12-21 | 2011-04-14 | Emue Holdings Pty Ltd | Authentication device and/or method |
TWI550628B (zh) * | 2014-07-16 | 2016-09-21 | 群聯電子股份有限公司 | 解碼方法、記憶體儲存裝置及記憶體控制電路單元 |
FR3117300A1 (fr) | 2020-12-03 | 2022-06-10 | Orange | Procédé de télécommunication pour réception itérative et dispositifs correspondant |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1996024999A1 (fr) * | 1995-02-07 | 1996-08-15 | France Telecom | Dispositif de reception de signaux numeriques a structure iterative, module et procede correspondants |
Family Cites Families (3)
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US5265125A (en) * | 1990-11-16 | 1993-11-23 | Matsushita Electric Industrial Co., Ltd. | Signal detection apparatus for detecting digital information from PCM signal |
JPH10271051A (ja) * | 1997-03-11 | 1998-10-09 | Alcatel Alsthom Co General Electricite | 双方向等化を伴う送/受信装置 |
US6360369B1 (en) * | 1998-02-18 | 2002-03-19 | Paul F. Mahoney | Interference tolerant modem |
-
1997
- 1997-05-15 FR FR9705978A patent/FR2763454B1/fr not_active Expired - Lifetime
-
1998
- 1998-05-13 WO PCT/FR1998/000951 patent/WO1998052329A1/fr active IP Right Grant
- 1998-05-13 EP EP98924426A patent/EP0981881B1/fr not_active Expired - Lifetime
- 1998-05-13 JP JP54886998A patent/JP4443634B2/ja not_active Expired - Lifetime
- 1998-05-13 US US09/423,994 patent/US6763076B1/en not_active Expired - Lifetime
- 1998-05-13 DE DE69804299T patent/DE69804299T2/de not_active Expired - Lifetime
- 1998-05-13 CN CN98805136A patent/CN1112011C/zh not_active Expired - Lifetime
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1996024999A1 (fr) * | 1995-02-07 | 1996-08-15 | France Telecom | Dispositif de reception de signaux numeriques a structure iterative, module et procede correspondants |
Non-Patent Citations (3)
Title |
---|
BERROU C ET AL: "NEAR SHANNON LIMIT ERROR - CORRECTING CODING AND DECODING: TURBO-CODES (1)", PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), GENEVA, MAY 23 - 26, 1993, vol. 1 - 2 - 03, 23 May 1993 (1993-05-23), INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, pages 1064 - 1070, XP000371240 * |
DOUILLARD: "Iterative correction of intersymbol interference: Turbo-Equalization", EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, vol. 6, no. 5, October 1995 (1995-10-01), ITALY, pages 507 - 511, XP002055352 * |
SEDAT OL ER: "SOFT-DECISION MULTISTAGE DECODING OF MULTILEVEL0CODED QUATERNARY PARTIAL-RESPONSE SIGNALS", PROCEEDINGS OF THE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, TRONDHEIM, JUNE 27 - JULY 1, 1994, 1 May 1994 (1994-05-01), INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, pages 1242 - 1248, XP000438699 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011035919A (ja) * | 2002-04-16 | 2011-02-17 | Thomson Licensing | Hdtv受信器用連結等化器/トレリス復号器アーキテクチャ |
JP2013150350A (ja) * | 2002-04-16 | 2013-08-01 | Thomson Licensing | Hdtv受信器用連結等化器/トレリス復号器アーキテクチャ |
Also Published As
Publication number | Publication date |
---|---|
EP0981881B1 (fr) | 2002-03-20 |
US6763076B1 (en) | 2004-07-13 |
CN1256834A (zh) | 2000-06-14 |
FR2763454B1 (fr) | 1999-08-06 |
DE69804299T2 (de) | 2002-11-14 |
DE69804299D1 (de) | 2002-04-25 |
JP2001525139A (ja) | 2001-12-04 |
JP4443634B2 (ja) | 2010-03-31 |
CN1112011C (zh) | 2003-06-18 |
FR2763454A1 (fr) | 1998-11-20 |
EP0981881A1 (fr) | 2000-03-01 |
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