WO2011033217A1 - Pre-filtering of a data signal transmitted between two communicating entities via a wire transmission channel - Google Patents

Pre-filtering of a data signal transmitted between two communicating entities via a wire transmission channel Download PDF

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Publication number
WO2011033217A1
WO2011033217A1 PCT/FR2010/051908 FR2010051908W WO2011033217A1 WO 2011033217 A1 WO2011033217 A1 WO 2011033217A1 FR 2010051908 W FR2010051908 W FR 2010051908W WO 2011033217 A1 WO2011033217 A1 WO 2011033217A1
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WIPO (PCT)
Prior art keywords
communicating entity
transmission channel
channel
information
filtering
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PCT/FR2010/051908
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French (fr)
Inventor
Rehan Hashmat
Pascal Pagani
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France Telecom
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Publication of WO2011033217A1 publication Critical patent/WO2011033217A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/7163—Spread spectrum techniques using impulse radio
    • H04B1/71632—Signal aspects

Definitions

  • the present invention relates to the pre-filtering of a data signal transmitted between two communicating entities via a wired transmission channel.
  • the field of wired communications covers both local networks and access networks.
  • the data is transmitted, for example, via a coaxial cable, a conventional telephone cable or by line carrier lines (CPL), that is to say by the electrical network.
  • CPL line carrier lines
  • the data is for example transmitted by telephone cables using an xDSL technology.
  • the cables used constitute a difficult transmission channel, generating attenuations and multiple propagation paths. These phenomena are all the more troublesome as the data rates are higher and higher. Indeed, we use cables that are often pre-existing, whose initial purpose was not to transfer data at high speed.
  • a major disadvantage of wired communications is the generation of radiated signals. This phenomenon is particularly marked for power line systems. Indeed, in this case, the copper cables that are used to transmit a data signal behave as an antenna and part of the transmitted power is radiated. This results in attenuation of the signal received by a receiver. It can also lead to electromagnetic compatibility problems, such as interference with other services such as amateur radio or short wave broadcasting. These problems of electromagnetic compatibility are particularly sensitive for power lines in line, but are also present in other types of wired communication network.
  • a radio signal transmitted by an antenna of a communicating entity undergoes deformations as a function of the propagation conditions between an origin point defined at the output of the antenna. antenna and a destination point defined at the input of an antenna of the communicating entity destination.
  • the antenna signal is previously distorted by applying pre-processing coefficients as a function of the characteristics of the propagation channel between these two antennas. It is therefore necessary to characterize this propagation channel.
  • Time reversal is a technique of focusing waves, typically acoustic waves, based on time reversal invariance of the wave equation.
  • a temporally inverted wave propagates like a direct wave that goes back in time.
  • a brief pulse emitted from an origin point propagates in a propagation medium. Part of this wave received by a destination point is returned temporally before being returned to the propagation medium.
  • the wave converges towards the origin point by reforming a brief pulse.
  • the signal collected at the origin point is almost identical in its form to the original signal emitted at the origin point.
  • the inverted wave converges all the more precisely as the propagation medium is complex.
  • the temporal reversal of the propagation channel applied to the wave somehow makes it possible to overcome the effect of this channel during the transmission of the wave thus pre-distorted from the point of origin.
  • the technique of time reversal is applied to the radio communication networks to overcome the effect of the propagation channel on the antenna signal, in particular by reducing channel spread, and simplify the processing of symbols received after the crossing. of the canal.
  • the antenna signal transmitted by an antenna of the source communicating entity is thus pre-filtered by applying coefficients obtained from the time reversal of the impulse response of the propagation channel that this antenna signal must pass through.
  • time reversal designed in a wireless communication context is not applied to wired communications by those skilled in the art, which prefers known methods but complex to seek to reduce the effects of unwanted radiation.
  • the present invention aims to solve the disadvantages of the prior art by providing a method and a pre-filtering device using the time reversal technique in a wired communication context.
  • the invention proposes a method for pre-filtering a data signal transmitted between a first communicating entity and a second entity communicating via a wired transmission channel, characterized in that it comprises the steps of:
  • determining a pre-filtering to be applied to the data signal by applying a time reversal to the information on the transmission channel.
  • the level of the unintentionally radiated power in the wired network decreases significantly. This solves the problem of electromagnetic compatibility related, for example, with the carrier currents in line.
  • the signal-to-noise ratio improvement obtained by the invention makes it possible to reduce the power level to be transmitted.
  • the application of the time reversal is carried out by phase conjugation on the information on the transmission channel defined in the frequency domain. This is particularly advantageous for multi-carrier modulation systems.
  • the acquisition step comprises sub-steps of:
  • the acquisition step comprises sub-steps of:
  • This variant is advantageous when the transmission channel is symmetrical.
  • the test signal is a predetermined sequence or a pulse signal.
  • the invention also relates to a device for pre-filtering a data signal transmitted between a first communicating entity and a second communicating entity via a wire transmission channel, characterized in that it comprises:
  • the invention also relates to a communicating entity characterized in that it comprises a pre-filtering device as previously presented.
  • the communicating entity comprises means for transmitting a test signal to another entity communicating, via the wired transmission channel, and / or channel estimation means.
  • the invention also relates to a system comprising communicating entities connected by a wired transmission channel, characterized in that it comprises at least one communicating entity according to the invention.
  • the pre-filtering device, the communicating entity and the system have advantages similar to those of the method.
  • the various steps of the pre-filtering method are determined by computer program instructions.
  • the invention also relates to a computer program on an information medium, this program being capable of being implemented in a communicating entity or more generally in a computer, this program including instructions adapted to the setting implement steps of a method as described above.
  • This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.
  • the invention also relates to a computer readable information medium, and comprising instructions of the computer programs as mentioned above.
  • the information carrier may be any entity or device capable of storing the program.
  • the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard.
  • the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means.
  • the program according to the invention can be downloaded in particular on an Internet type network.
  • the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.
  • FIG. 1 represents an embodiment of a system according to the invention
  • FIG. 2 represents a method embodiment of the invention.
  • a system comprises at least two communicating entities EC1 and EC2 connected by a wired transmission channel CT.
  • the communicating entities are for example computers.
  • the transmission channel is part of a wired communication network which comprises for example coaxial cables, or telephone cables. It can also include a part of the power supply network, in the case of power line transmission in line.
  • the communicating entity EC1 is a data transmitter and that the communicating entity EC2 is a receiver of these same data.
  • an entity can be both transmitter and receiver of data.
  • the invention is not limited to a configuration with two communicating entities.
  • the communicating entity EC1 comprises:
  • the communicating entity EC1 comprises means for transmitting a test signal, or pilot signal, to the communicating entity EC2, via the wired transmission channel.
  • the communicating entity EC2 comprises channel estimation means.
  • it is the communicating entity EC2 which comprises means for transmitting a test signal and the communicating entity EC1 which comprises channel estimation means.
  • the communicating entities EC1 and EC2 comprise conventional means for transmitting and receiving data via the wired channel CT.
  • the communicating entity EC1 has the conventional architecture of a computer. It has a processor 11, a random access memory 12, a read-only memory 13 and means 14 for communication with the communicating entity EC2.
  • the read-only memory 13 constitutes a recording medium readable by the communicating entity EC1 on which is recorded a computer program P1 comprising instructions for performing the steps of a pre-filtering method according to the invention and whose the main steps are represented as a flowchart in Figure 2.
  • the architecture of the communicating entity EC2 is similar to that of the communicating entity EC1.
  • the communicating entity EC2 has a processor 21, a random access memory 22, a read-only memory 23 and means 24 for communicating with the communicating entity EC1.
  • the communicating entity EC1 transmits a signal s (t) via the wired transmission channel CT to the communicating entity EC2.
  • the latter receives a signal r (t).
  • R (f) S (f) XH (f)
  • R (f), S (f) and H (f) represent the signals in the frequency domain respectively obtained by Fourier transformation of the signals r (t), s (t) and h (t).
  • the signals are expressed in the frequency domain, but they can be expressed in the time domain in a completely equivalent manner.
  • a pre-filtering method according to the invention comprises steps E1 to E4 implemented in the communicating entity EC1.
  • Step E1 is the acquisition of information G (f) on the wired transmission channel CT by the first communicating entity EC1, by means of a channel estimation.
  • the information G (f) on the channel is then equal to the transfer function H (f) of the wired channel.
  • G (f) H (f) + N (f), where N (f) represents a noise, expressed in the frequency domain, generated by the process channel information acquisition.
  • the invention applies when the information on the channel is not complete.
  • the information G (f) may represent only the phase of the transfer function H (f).
  • the information G (f) on the wired channel is determined from the transfer function H (f) of the wired channel.
  • the information G (f) represents all or part of the transfer function H (f).
  • a first embodiment of acquisition of information on the channel comprises the transmission of a test signal, or pilot signal between the first communicating entity EC1 and the second.
  • the pilot signal is a sequence known or a pulse signal.
  • the channel is then estimated in the second communicating entity EC2, according to a technique known per se.
  • the channel information is then transmitted between the second communicating entity and the first via the wired communication channel.
  • a second embodiment is based on the fact that the channel is symmetrical between the two communicating entities.
  • the pilot signal is transmitted from the second communicating entity EC2 to the first.
  • the channel estimation is performed in the first communicating entity EC1, which avoids the transmission of the channel information.
  • Step E1 is followed by step E2 which is the determination of a pre-filtering to be applied to the data signal, by applying a time reversal to the information on the transmission channel.
  • This information is defined in the time domain. Equivalently, phase conjugation is performed on the information on the transmission channel defined in the frequency domain.
  • the filter can be normalized.
  • the pre-filtering function D (f) is obtained by:
  • the filter D (f) H * (f) / (E [
  • the next step E3 is the application of pre-filtering to the signal to be transmitted by the communicating entity EC1.
  • the next step E4 is the transmission of the pre-filtered signal S '(f) by the communicating entity EC1 to the communicating entity EC2, via the wired transmission channel CT.
  • the signal R '(f) received by the communicating entity EC2 is obtained by:
  • R '(f) S (f) x H * (f) / (E [
  • 2 ]) 1 2 x H (f) S (f) x
  • the pre-filtering is done in the frequency domain, which involves only complex number multiplication operations.
  • the pre-filtering can be done in the time domain, which requires the implementation of a convolution filter.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

The invention relates to a method of pre-filtering a data signal transmitted between a first communicating entity and a second communicating entity via a wire transmission channel, characterized in that said method comprises the steps of: - acquisition (E1) of information (G(f)) on the wire transmission channel by the first communicating entity, by means of a channel estimation, - determination (E2) of a pre-filtering process (D(f)) to be applied to the data signal by applying time reversal to the information on the transmission channel.

Description

Pré-filtrage d'un signal de données transmis entre deux entités communicantes via un canal de transmission fi la ire  Pre-filtering a data signal transmitted between two communicating entities via a fi lled transmission channel
La présente invention concerne le pré-filtrage d'un signal de données transmis entre deux entités communicantes via un canal de transmission filaire. The present invention relates to the pre-filtering of a data signal transmitted between two communicating entities via a wired transmission channel.
Le domaine des communications filaires recouvre aussi bien les réseaux locaux que les réseaux d'accès. The field of wired communications covers both local networks and access networks.
Dans un réseau local, les données sont par exemple transmises par l'intermédiaire d'un câble coaxial, d'un câble téléphonique classique ou encore par des courants porteurs en ligne (CPL), c'est-à-dire par le réseau électrique.  In a local area network, the data is transmitted, for example, via a coaxial cable, a conventional telephone cable or by line carrier lines (CPL), that is to say by the electrical network. .
Dans un réseau d'accès, les données sont par exemple transmises par des câbles téléphoniques selon une technologie xDSL.  In an access network, the data is for example transmitted by telephone cables using an xDSL technology.
De manière générale, les câbles utilisés constituent un canal de transmission difficile, générant des atténuations et des trajets de propagation multiples. Ces phénomènes sont d'autant plus gênants que les débits de données sont de plus en plus élevés. En effet, on utilise des câbles bien souvent pré-existants, dont le but initial n'était pas de transférer des données à haut débit.  In general, the cables used constitute a difficult transmission channel, generating attenuations and multiple propagation paths. These phenomena are all the more troublesome as the data rates are higher and higher. Indeed, we use cables that are often pre-existing, whose initial purpose was not to transfer data at high speed.
Un inconvénient majeur des communications filaires est la génération de signaux rayonnés. Ce phénomène est particulièrement marqué pour les systèmes de courant porteur en ligne. En effet, dans ce cas, les câbles de cuivre qui sont utilisés pour transmettre un signal de données se comportent comme une antenne et une partie de la puissance transmise est rayonnée. Cela a pour conséquence une atténuation du signal reçu par un récepteur. Cela peut aussi entraîner des problèmes de compatibilité électromagnétique, par exemple des interférences avec d'autres services tels que la radio amateur ou la diffusion en ondes courtes. Ces problèmes de compatibilité électromagnétique sont particulièrement sensibles pour les courants porteurs en ligne, mais sont aussi présents dans les autres types de réseau de communication filaire. A major disadvantage of wired communications is the generation of radiated signals. This phenomenon is particularly marked for power line systems. Indeed, in this case, the copper cables that are used to transmit a data signal behave as an antenna and part of the transmitted power is radiated. This results in attenuation of the signal received by a receiver. It can also lead to electromagnetic compatibility problems, such as interference with other services such as amateur radio or short wave broadcasting. These problems of electromagnetic compatibility are particularly sensitive for power lines in line, but are also present in other types of wired communication network.
Des techniques de prétraitement d'un signal à transmettre sont connues. Par exemple, le document EP 0936781 décrit une détermination de coefficients de pré-égalisation visant à annuler l'effet d'un canal de propagation avec mise en oeuvre d'une inversion matricielle complexe. Cette méthode s'applique à différents types de canaux, dont les canaux filaires, mais elle est d'une grande complexité calculatoire. Techniques for preprocessing a signal to be transmitted are known. For example, the document EP 0936781 describes a determination of pre-equalization coefficients for canceling the effect of a propagation channel with implementation of a complex matrix inversion. This method applies to different types of channels, including wired channels, but it is of great computational complexity.
Par ailleurs, dans le domaine des communications sans fil, un signal radio transmis par une antenne d'une entité communicante, dit signal d'antenne, subit des déformations en fonction des conditions de propagation entre un point d'origine défini en sortie de l'antenne d'origine et un point destinataire défini en entrée d'une antenne de l'entité communicante destinataire. Afin de limiter ces déformations, le signal d'antenne est préalablement distordu par application de coefficients de pré-traitement en fonction des caractéristiques du canal de propagation entre ces deux antennes. Il est donc nécessaire de caractériser ce canal de propagation. Moreover, in the field of wireless communications, a radio signal transmitted by an antenna of a communicating entity, called an antenna signal, undergoes deformations as a function of the propagation conditions between an origin point defined at the output of the antenna. antenna and a destination point defined at the input of an antenna of the communicating entity destination. In order to limit these deformations, the antenna signal is previously distorted by applying pre-processing coefficients as a function of the characteristics of the propagation channel between these two antennas. It is therefore necessary to characterize this propagation channel.
Parmi les méthodes de pré-traitement existantes, se distinguent les méthodes basées sur le retournement temporel du fait de leur complexité réduite et de leur performance.  Among the existing preprocessing methods, methods based on time reversal are distinguished by their reduced complexity and their performance.
Le retournement temporel est une technique de focalisation des ondes, typiquement des ondes acoustiques, qui repose sur l'invariance par renversement du temps de l'équation d'onde. Ainsi, une onde temporellement inversée se propage comme une onde directe qui remonterait le temps. Une impulsion brève émise d'un point origine se propage dans un milieu de propagation. Une partie de cette onde reçue par un point destinataire est retournée temporellement avant d'être renvoyée dans le milieu de propagation. L'onde converge vers le point origine en y reformant une impulsion brève. Le signal recueilli au point origine est quasi identique dans sa forme au signal d'origine émis au point origine. En particulier l'onde retournée converge d'autant plus précisément que le milieu de propagation est complexe. Le retournement temporel du canal de propagation appliqué à l'onde permet en quelque sorte de s'affranchir de l'effet de ce canal lors de la transmission de l'onde ainsi pré- distordue à partir du point d'origine. Time reversal is a technique of focusing waves, typically acoustic waves, based on time reversal invariance of the wave equation. Thus, a temporally inverted wave propagates like a direct wave that goes back in time. A brief pulse emitted from an origin point propagates in a propagation medium. Part of this wave received by a destination point is returned temporally before being returned to the propagation medium. The wave converges towards the origin point by reforming a brief pulse. The signal collected at the origin point is almost identical in its form to the original signal emitted at the origin point. In particular, the inverted wave converges all the more precisely as the propagation medium is complex. The temporal reversal of the propagation channel applied to the wave somehow makes it possible to overcome the effect of this channel during the transmission of the wave thus pre-distorted from the point of origin.
La technique du retournement temporel est appliquée aux réseaux de communication radio pour s'affranchir de l'effet du canal de propagation sur le signal d'antenne, notamment en réduisant l'étalement du canal, et simplifier le traitement de symboles reçus après la traversée du canal. Le signal d'antenne émis par une antenne de l'entité communicante d'origine est ainsi pré-filtré par application de coefficients obtenus à partir du retournement temporel de la réponse impulsionnelle du canal de propagation que ce signal d'antenne doit traverser.  The technique of time reversal is applied to the radio communication networks to overcome the effect of the propagation channel on the antenna signal, in particular by reducing channel spread, and simplify the processing of symbols received after the crossing. of the canal. The antenna signal transmitted by an antenna of the source communicating entity is thus pre-filtered by applying coefficients obtained from the time reversal of the impulse response of the propagation channel that this antenna signal must pass through.
Il est à noter que le problème de la réduction des effets de rayonnement indésirable, qui se pose pour des communications filaires, n'existe pas pour des communication radio.  It should be noted that the problem of reducing unwanted radiation effects, which arises for wired communications, does not exist for radio communication.
On comprend donc que le retournement temporel, conçu dans un contexte de communication sans fil n'est pas appliqué aux communications filaires par l'homme du métier, qui préfère des méthodes connues mais complexes pour chercher à réduire les effets de rayonnement indésirable.  It is therefore understood that the time reversal, designed in a wireless communication context is not applied to wired communications by those skilled in the art, which prefers known methods but complex to seek to reduce the effects of unwanted radiation.
La présente invention a pour but de résoudre les inconvénients de la technique antérieure en fournissant un procédé et un dispositif de pré-filtrage utilisant la technique de retournement temporel dans un contexte de communication filaire.  The present invention aims to solve the disadvantages of the prior art by providing a method and a pre-filtering device using the time reversal technique in a wired communication context.
A cette fin, l'invention propose un procédé de pré-filtrage d'un signal de données transmis entre une première entité communicante et une seconde entité communicante via un canal de transmission filaire, caractérisé en ce qu'il comporte les étapes de : To this end, the invention proposes a method for pre-filtering a data signal transmitted between a first communicating entity and a second entity communicating via a wired transmission channel, characterized in that it comprises the steps of:
- acquisition d'informations sur le canal de transmission filaire par la première entité communicante, au moyen d'une estimation de canal,  acquiring information on the wired transmission channel by the first communicating entity, by means of a channel estimation,
- détermination d'un pré-filtrage à appliquer au signal de données, en appliquant un retournement temporel aux informations sur le canal de transmission.  determining a pre-filtering to be applied to the data signal, by applying a time reversal to the information on the transmission channel.
Grâce à l'invention, les multi-trajets et la dispersion qui existent dans un réseau filaire sont pris en compte et les performances de systèmes de communication utilisant ce réseau filaire sont améliorées.  Thanks to the invention, multipath and dispersion that exist in a wired network are taken into account and the performance of communication systems using this wired network are improved.
Ainsi, le niveau de la puissance involontairement rayonnée dans le réseau filaire diminue de manière importante. Cela permet de résoudre le problème de compatibilité électromagnétique lié, par exemple, avec les courants porteurs en ligne.  Thus, the level of the unintentionally radiated power in the wired network decreases significantly. This solves the problem of electromagnetic compatibility related, for example, with the carrier currents in line.
En outre, il y a amélioration du gain global de puissance du signal au récepteur. La technique de retournement temporel limite intrinsèquement les effets de dispersion du canal. C'est avantageux pour des communications filaires où les incertitudes topologiques sont une source importante de dégradation de rapport signal à bruit au récepteur.  In addition, there is improvement of the overall power gain of the signal to the receiver. The time reversal technique intrinsically limits the effects of channel dispersion. This is advantageous for wired communications where topological uncertainties are an important source of signal to noise ratio degradation at the receiver.
En outre, l'amélioration de rapport signal à bruit obtenue par l'invention permet de réduire le niveau de puissance à transmettre.  In addition, the signal-to-noise ratio improvement obtained by the invention makes it possible to reduce the power level to be transmitted.
Ainsi, l'invention va à encontre des préjugés de l'homme du métier et améliore les transmissions sur canaux filaires.  Thus, the invention goes against the prejudices of those skilled in the art and improves transmissions on wire channels.
Selon une caractéristique préférée, l'application du retournement temporel s'effectue par conjugaison de phase sur les informations sur le canal de transmission définies dans le domaine fréquentiel. C'est particulièrement avantageux pour les systèmes à modulation multi-porteuses.  According to a preferred characteristic, the application of the time reversal is carried out by phase conjugation on the information on the transmission channel defined in the frequency domain. This is particularly advantageous for multi-carrier modulation systems.
Selon une caractéristique préférée, l'étape d'acquisition comporte des sous-étapes de : According to a preferred characteristic, the acquisition step comprises sub-steps of:
- transmission d'un signal de test entre la première entité communicante et la seconde, - estimation du canal par la seconde entité communicante, à partir du signal de test, pour déterminer les informations sur le canal de transmission,transmission of a test signal between the first communicating entity and the second, estimation of the channel by the second communicating entity, from the test signal, to determine the information on the transmission channel,
- transmission des informations sur le canal de transmission entre la seconde entité communicante et la première. - Transmission of information on the transmission channel between the second communicating entity and the first.
Ainsi le canal de transmission entre la première entité communicante et la seconde est estimé.  Thus the transmission channel between the first communicating entity and the second is estimated.
Alternativement, l'étape d'acquisition comporte des sous-étapes de : Alternatively, the acquisition step comprises sub-steps of:
- transmission d'un signal de test entre la seconde entité communicante et la première, transmission of a test signal between the second communicating entity and the first,
- estimation du canal par la première entité communicante, à partir du signal de test, pour déterminer les informations sur le canal de transmission.  - Estimation of the channel by the first communicating entity, from the test signal, to determine the information on the transmission channel.
Cette variante est avantageuse lorsque le canal de transmission est symétrique.  This variant is advantageous when the transmission channel is symmetrical.
Selon une caractéristique préférée, le signal de test est une séquence prédéterminée ou un signal impulsionnel.  According to a preferred characteristic, the test signal is a predetermined sequence or a pulse signal.
L'invention concerne aussi un dispositif de pré-filtrage d'un signal de données transmis entre une première entité communicante et une seconde entité communicante via un canal de transmission filaire, caractérisé en ce qu'il comporte : The invention also relates to a device for pre-filtering a data signal transmitted between a first communicating entity and a second communicating entity via a wire transmission channel, characterized in that it comprises:
- des moyens d'acquisition d'informations sur le canal de transmission filaire par la première entité communicante, au moyen d'une estimation de canal,  means for acquiring information on the wire transmission channel by the first communicating entity, by means of a channel estimation,
- des moyens de détermination d'un pré-filtrage à appliquer au signal de données, en appliquant un retournement temporel aux informations sur le canal de transmission.  means for determining a pre-filtering to be applied to the data signal, by applying a time reversal to the information on the transmission channel.
L'invention concerne aussi une entité communicante caractérisée en ce qu'elle comporte un dispositif de pré-filtrage tel que précédemment présenté. The invention also relates to a communicating entity characterized in that it comprises a pre-filtering device as previously presented.
En particulier, l'entité communicante selon l'invention comporte des moyens de transmission d'un signal de test vers une autre entité communicante, via le canal de transmission filaire, et/ou des moyens d'estimation de canal. In particular, the communicating entity according to the invention comprises means for transmitting a test signal to another entity communicating, via the wired transmission channel, and / or channel estimation means.
L'invention concerne aussi un système comportant des entités communicantes reliées par un canal de transmission filaire, caractérisé en ce qu'il comporte au moins une entité communicante selon l'invention.  The invention also relates to a system comprising communicating entities connected by a wired transmission channel, characterized in that it comprises at least one communicating entity according to the invention.
Le dispositif de pré-filtrage, l'entité communicante et le système présentent des avantages analogues à ceux du procédé. The pre-filtering device, the communicating entity and the system have advantages similar to those of the method.
Dans un mode particulier de réalisation, les différentes étapes du procédé de pré-filtrage sont déterminées par des instructions de programmes d'ordinateurs.  In a particular embodiment, the various steps of the pre-filtering method are determined by computer program instructions.
En conséquence, l'invention vise aussi un programme d'ordinateur sur un support d'informations, ce programme étant susceptible d'être mis en œuvre dans une entité communicante ou plus généralement dans un ordinateur, ce programme comportant des instructions adaptées à la mise en œuvre des étapes d'un procédé tel que décrit ci-dessus.  Consequently, the invention also relates to a computer program on an information medium, this program being capable of being implemented in a communicating entity or more generally in a computer, this program including instructions adapted to the setting implement steps of a method as described above.
Ce programme peut utiliser n'importe quel langage de programmation, et être sous la forme de code source, code objet, ou de code intermédiaire entre code source et code objet, tel que dans une forme partiellement compilée, ou dans n'importe quelle autre forme souhaitable.  This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.
L'invention vise aussi un support d'informations lisible par un ordinateur, et comportant des instructions des programmes d'ordinateur tels que mentionnés ci-dessus.  The invention also relates to a computer readable information medium, and comprising instructions of the computer programs as mentioned above.
Le support d'informations peut être n'importe quelle entité ou dispositif capable de stocker le programme. Par exemple, le support peut comporter un moyen de stockage, tel qu'une ROM, par exemple un CD ROM ou une ROM de circuit microélectronique, ou encore un moyen d'enregistrement magnétique, par exemple une disquette (floppy dise) ou un disque dur.  The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard.
D'autre part, le support d'informations peut être un support transmissible tel qu'un signal électrique ou optique, qui peut être acheminé via un câble électrique ou optique, par radio ou par d'autres moyens. Le programme selon l'invention peut être en particulier téléchargé sur un réseau de type Internet.  On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can be downloaded in particular on an Internet type network.
Alternativement, le support d'informations peut être un circuit intégré dans lequel le programme est incorporé, le circuit étant adapté pour exécuter ou pour être utilisé dans l'exécution du procédé en question. D'autres caractéristiques et avantages apparaîtront à la lecture de modes de réalisation préférés décrits en référence aux figures dans lesquelles : Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question. Other features and advantages will appear on reading preferred embodiments described with reference to the figures in which:
- la figure 1 représente un mode de réalisation de système selon l'invention,  FIG. 1 represents an embodiment of a system according to the invention,
- la figure 2 représente un mode de réalisation de procédé selon l'invention.  FIG. 2 represents a method embodiment of the invention.
Selon un mode de réalisation de l'invention représenté à la figure 1 , un système comporte au moins deux entités communicantes EC1 et EC2 reliées par un canal de transmission filaire CT. According to one embodiment of the invention shown in FIG. 1, a system comprises at least two communicating entities EC1 and EC2 connected by a wired transmission channel CT.
Les entités communicantes sont par exemples des ordinateurs. Le canal de transmission fait partie d'un réseau de communication filaire qui comporte par exemple des câbles coaxiaux, ou des câbles téléphoniques. Il peut aussi comporter une partie de réseau d'alimentation électrique, dans le cas de transmission par courant porteur en ligne.  The communicating entities are for example computers. The transmission channel is part of a wired communication network which comprises for example coaxial cables, or telephone cables. It can also include a part of the power supply network, in the case of power line transmission in line.
Dans un but de simplification de l'exposé, on considère dans la suite que l'entité communicante EC1 est un émetteur de données et que l'entité communicante EC2 est un récepteur de ces mêmes données.  For the sake of simplification of the disclosure, it is subsequently assumed that the communicating entity EC1 is a data transmitter and that the communicating entity EC2 is a receiver of these same data.
Bien entendu, une entité pourra être à la fois émetteur et récepteur de données. De même, l'invention n'est pas limitée à une configuration avec deux entités communicantes.  Of course, an entity can be both transmitter and receiver of data. Similarly, the invention is not limited to a configuration with two communicating entities.
Selon l'invention, l'entité communicante EC1 comporte :  According to the invention, the communicating entity EC1 comprises:
- des moyens d'acquisition d'informations sur le canal de transmission filaire, au moyen d'une estimation de canal,  means for acquiring information on the wired transmission channel, by means of a channel estimation,
- des moyens de détermination d'un pré-filtrage à appliquer au signal de données, en appliquant un retournement temporel aux informations sur le canal de transmission.  means for determining a pre-filtering to be applied to the data signal, by applying a time reversal to the information on the transmission channel.
L'entité communicante EC1 comporte des moyens de transmission d'un signal de test, ou signal pilote, vers l'entité communicante EC2, via le canal de transmission filaire. L'entité communicante EC2 comporte des moyens d'estimation de canal. En variante, c'est l'entité communicante EC2 qui comporte des moyens de transmission d'un signal de test et l'entité communicante EC1 qui comporte des moyens d'estimation de canal. The communicating entity EC1 comprises means for transmitting a test signal, or pilot signal, to the communicating entity EC2, via the wired transmission channel. The communicating entity EC2 comprises channel estimation means. As a variant, it is the communicating entity EC2 which comprises means for transmitting a test signal and the communicating entity EC1 which comprises channel estimation means.
Les entités communicantes EC1 et EC2 comportent des moyens classiques de transmission et réception de données via le canal filaire CT.  The communicating entities EC1 and EC2 comprise conventional means for transmitting and receiving data via the wired channel CT.
Dans l'exemple de réalisation décrit ici, l'entité communicante EC1 a l'architecture conventionnelle d'un ordinateur. Elle possède un processeur 11 , une mémoire vive 12, une mémoire morte 13 et des moyens 14 de communication avec l'entité communicante EC2.  In the exemplary embodiment described here, the communicating entity EC1 has the conventional architecture of a computer. It has a processor 11, a random access memory 12, a read-only memory 13 and means 14 for communication with the communicating entity EC2.
La mémoire morte 13 constitue un support d'enregistrement lisible par l'entité communicante EC1 sur lequel est enregistré un programme d'ordinateur P1 comprenant des instructions pour l'exécution des étapes d'un procédé de pré-filtrage selon l'invention et dont les principales étapes sont représentées sous forme d'organigramme à la figure 2.  The read-only memory 13 constitutes a recording medium readable by the communicating entity EC1 on which is recorded a computer program P1 comprising instructions for performing the steps of a pre-filtering method according to the invention and whose the main steps are represented as a flowchart in Figure 2.
L'architecture de l'entité communicante EC2 est similaire à celle de l'entité communicante EC1. L'entité communicante EC2 possède un processeur 21 , une mémoire vive 22, une mémoire morte 23 et des moyens 24 de communication avec l'entité communicante EC1.  The architecture of the communicating entity EC2 is similar to that of the communicating entity EC1. The communicating entity EC2 has a processor 21, a random access memory 22, a read-only memory 23 and means 24 for communicating with the communicating entity EC1.
En l'absence de pré-filtrage, l'entité communicante EC1 transmet un signal s(t) via le canal de transmission filaire CT vers l'entité communicante EC2. Cette dernière reçoit un signal r(t). In the absence of pre-filtering, the communicating entity EC1 transmits a signal s (t) via the wired transmission channel CT to the communicating entity EC2. The latter receives a signal r (t).
La relation entre le signal transmis et le signal reçu est : r(t) = s(t) ® h(t) où h(t) est la réponse impulsionnelle du canal et ® représente l'opération de convolution.  The relationship between the transmitted signal and the received signal is: r (t) = s (t) h h (t) where h (t) is the impulse response of the channel and représente represents the convolution operation.
Par transposition dans le domaine fréquentiel, on obtient :  By transposition in the frequency domain, we obtain:
R(f) = S(f) X H(f) Où R(f), S(f) et H(f) représentent les signaux dans le domaine fréquentiel respectivement obtenus par transformation de Fourier des signaux r(t), s(t) et h(t). R (f) = S (f) XH (f) Where R (f), S (f) and H (f) represent the signals in the frequency domain respectively obtained by Fourier transformation of the signals r (t), s (t) and h (t).
Dans la suite, on exprime les signaux dans le domaine fréquentiel, mais on peut les exprimer dans le domaine temporel de manière tout à fait équivalente.  In the following, the signals are expressed in the frequency domain, but they can be expressed in the time domain in a completely equivalent manner.
Le fonctionnement du système selon l'invention est décrit dans la suite à l'aide de l'organigramme de la figure 2.  The operation of the system according to the invention is described below using the flowchart of FIG. 2.
En référence à la figure 2, un procédé de pré-filtrage selon l'invention comporte des étapes E1 à E4 mises en oeuvre dans l'entité communicante EC1.  With reference to FIG. 2, a pre-filtering method according to the invention comprises steps E1 to E4 implemented in the communicating entity EC1.
L'étape E1 est l'acquisition d'informations G(f) sur le canal de transmission filaire CT par la première entité communicante EC1 , au moyen d'une estimation de canal.  Step E1 is the acquisition of information G (f) on the wired transmission channel CT by the first communicating entity EC1, by means of a channel estimation.
Dans un cas idéal, la première entité communicante EC1 acquiert toute les informations sur le canal, de sorte que l'égalité : G(f) = H(f) est vérifiée. Les informations G(f) sur le canal sont alors égales à la fonction de transfert H(f) du canal filaire.  In an ideal case, the first communicating entity EC1 acquires all the information on the channel, so that the equality: G (f) = H (f) is checked. The information G (f) on the channel is then equal to the transfer function H (f) of the wired channel.
Cependant, en pratique, les informations de canal sont souvent dégradées, on a donc G(f) = H(f) + N(f), où N(f) représente un bruit, exprimé dans le domaine fréquentiel, généré par le processus d'acquisition d'informations de canal.  However, in practice, the channel information is often degraded, so we have G (f) = H (f) + N (f), where N (f) represents a noise, expressed in the frequency domain, generated by the process channel information acquisition.
Il est à noter que l'invention s'applique lorsque les informations sur le canal ne sont pas complètes. Par exemple, les informations G(f) peuvent ne représenter que la phase de la fonction de transfert H(f).  It should be noted that the invention applies when the information on the channel is not complete. For example, the information G (f) may represent only the phase of the transfer function H (f).
De manière générale, les informations G(f) sur le canal filaire sont déterminées à partir de la fonction de transfert H(f) du canal filaire. Les informations G(f) représentent tout ou partie de la fonction de transfert H(f).  In general, the information G (f) on the wired channel is determined from the transfer function H (f) of the wired channel. The information G (f) represents all or part of the transfer function H (f).
Un premier mode de réalisation d'acquisition d'informations sur le canal comporte la transmission d'un signal de test, ou signal pilote entre la première entité communicante EC1 et la seconde. Le signal pilote est une séquence connue ou un signal impulsionnel. Le canal est ensuite estimé dans la seconde entité communicante EC2, selon une technique connue en soi. A first embodiment of acquisition of information on the channel comprises the transmission of a test signal, or pilot signal between the first communicating entity EC1 and the second. The pilot signal is a sequence known or a pulse signal. The channel is then estimated in the second communicating entity EC2, according to a technique known per se.
Les informations de canal sont alors transmises entre la seconde entité communicante et la première, via le canal de communication filaire.  The channel information is then transmitted between the second communicating entity and the first via the wired communication channel.
Un second mode de réalisation est fondé sur le fait que le canal est symétrique entre les deux entités communicantes. Selon ce mode, le signal pilote est transmis depuis la seconde entité communicante EC2 vers la première. L'estimation de canal est effectuée dans la première entité communicante EC1 , ce qui évite la transmission des informations de canal.  A second embodiment is based on the fact that the channel is symmetrical between the two communicating entities. In this mode, the pilot signal is transmitted from the second communicating entity EC2 to the first. The channel estimation is performed in the first communicating entity EC1, which avoids the transmission of the channel information.
L'étape E1 est suivie de l'étape E2 qui est la détermination d'un pré- filtrage à appliquer au signal de données, en appliquant un retournement temporel aux informations sur le canal de transmission. Ces informations sont définies dans le domaine temporel. De manière équivalente, on effectue une conjugaison de phase sur les informations sur le canal de transmission définies dans le domaine fréquentiel.  Step E1 is followed by step E2 which is the determination of a pre-filtering to be applied to the data signal, by applying a time reversal to the information on the transmission channel. This information is defined in the time domain. Equivalently, phase conjugation is performed on the information on the transmission channel defined in the frequency domain.
Le filtre peut être normalisé.  The filter can be normalized.
Dans le domaine fréquentiel, la fonction de pré-filtrage D(f) est obtenue par :  In the frequency domain, the pre-filtering function D (f) is obtained by:
D(f) = G*(f) / (E[|G(f)|2])1/2 D (f) = G * (f) / (E [| G (f) | 2 ] 1/2
Où * représente le complexe conjugué et E[.] représente en pratique la moyenne (ou en théorie l'espérance statistique). Where * represents the conjugate complex and E [.] Represents in practice the mean (or in theory the statistical expectation).
De manière équivalente dans le domaine temporel, le filtre d(t) est obtenu par : d(t) = g*(-t) / ( j| g(t) |2 dt )1/2 Equivalently in the time domain, the filter d (t) is obtained by: d (t) = g * (-t) / (j | g (t) | 2 dt) 1/2
Dans un cas idéal où il n'y a pas de bruit, c'est-à-dire si l'égalité G(f) = H(f) est vraie, on obtient : In an ideal case where there is no noise, that is, if the equality G (f) = H (f) is true, we obtain:
D(f) = H*(f) / (E[|H(f)|2]) Il est à noter que le filtre D(f) peut être aussi obtenu à partir d'une version modifiée de G(f), par exemple en ne prenant en compte que la phase ou encore en normalisant la puissance en utilisant une distribution non-uniforme de puissance dans le domaine fréquentiel. D (f) = H * (f) / (E [| H (f) | 2 ]) It should be noted that the filter D (f) can also be obtained from a modified version of G (f), for example by taking into account only the phase or else by normalizing the power using a non-linear distribution. uniform power in the frequency domain.
L'étape suivante E3 est l'application du pré-filtrage au signal à transmettre par l'entité communicante EC1. The next step E3 is the application of pre-filtering to the signal to be transmitted by the communicating entity EC1.
Le signal à transmettre est alors : S'(f) = S(f) x D(f)  The signal to be transmitted is then: S '(f) = S (f) x D (f)
L'étape suivante E4 est la transmission du signal pré-filtré S'(f) par l'entité communicante EC1 vers l'entité communicante EC2, via le canal de transmission filaire CT. The next step E4 is the transmission of the pre-filtered signal S '(f) by the communicating entity EC1 to the communicating entity EC2, via the wired transmission channel CT.
Le signal R'(f) reçu par l'entité communicante EC2 est obtenu par : The signal R '(f) received by the communicating entity EC2 is obtained by:
R'(f) = S'(f) x H(f) = S(f) x D(f) x H(f) Soit, si G(f) est égal à H(f) : R '(f) = S' (f) x H (f) = S (f) x D (f) x H (f) Let, if G (f) is equal to H (f):
R'(f) = S(f) x H*(f) / (E[|H(f)|2])1 2 x H(f) = S(f) x |H(f)|2/ (E[|H(f)|2])1/2 R '(f) = S (f) x H * (f) / (E [| H (f) | 2 ]) 1 2 x H (f) = S (f) x | H (f) | 2 / (E [| H (f) | 2 ]) 1/2
Il est à noter que pour un système de communication utilisant une modulation multi-porteuse, telle que l'OFDM, le pré-filtrage est fait dans le domaine fréquentiel, ce qui n'implique que des opérations de multiplications de nombres complexes. Dans d'autres cas, le pré-filtrage peut être fait dans le domaine temporel, ce qui nécessite la mise en œuvre d'un filtre de convolution. It should be noted that for a communication system using a multi-carrier modulation, such as OFDM, the pre-filtering is done in the frequency domain, which involves only complex number multiplication operations. In other cases, the pre-filtering can be done in the time domain, which requires the implementation of a convolution filter.

Claims

REVENDICATIONS
1. Procédé de pré-filtrage d'un signal de données transmis entre une première entité communicante et une seconde entité communicante via un canal de transmission filaire, caractérisé en ce qu'il comporte les étapes de : A method for pre-filtering a data signal transmitted between a first communicating entity and a second communicating entity via a wire transmission channel, characterized in that it comprises the steps of:
- acquisition (E1) d'informations (G(f)) sur le canal de transmission filaire par la première entité communicante, au moyen d'une estimation de canal, acquisition (E1) of information (G (f)) on the wired transmission channel by the first communicating entity, by means of a channel estimation,
- détermination (E2) d'un pré-filtrage (D(f)) à appliquer au signal de données, en appliquant un retournement temporel aux informations sur le canal de transmission. determining (E2) a pre-filtering (D (f)) to be applied to the data signal, by applying a time reversal to the information on the transmission channel.
2. Procédé de pré-filtrage selon la revendication 1 , caractérisé en ce que l'application du retournement temporel (E2) s'effectue par conjugaison de phase sur les informations sur le canal de transmission définies dans le domaine fréquentiel. 2. Pre-filtering method according to claim 1, characterized in that the application of the time reversal (E2) is performed by phase conjugation on the information on the transmission channel defined in the frequency domain.
3. Procédé de pré-filtrage selon la revendication 1 ou 2, caractérisé en ce que l'étape d'acquisition (E1) comporte des sous-étapes de : 3. Pre-filtering method according to claim 1 or 2, characterized in that the acquisition step (E1) comprises sub-steps of:
- transmission d'un signal de test entre la première entité communicante et la seconde,  transmission of a test signal between the first communicating entity and the second,
- estimation du canal par la seconde entité communicante, à partir du signal de test, pour déterminer les informations sur le canal de transmission, estimation of the channel by the second communicating entity, from the test signal, to determine the information on the transmission channel,
- transmission des informations sur le canal de transmission entre la seconde entité communicante et la première. - Transmission of information on the transmission channel between the second communicating entity and the first.
4. Procédé de pré-filtrage selon la revendication 1 ou 2, caractérisé en ce que l'étape d'acquisition (E1 ) comporte des sous-étapes de : 4. Pre-filtering method according to claim 1 or 2, characterized in that the acquisition step (E1) comprises sub-steps of:
- transmission d'un signal de test entre la seconde entité communicante et la première,  transmission of a test signal between the second communicating entity and the first,
- estimation du canal par la première entité communicante, à partir du signal de test, pour déterminer les informations sur le canal de transmission. - Estimation of the channel by the first communicating entity, from the test signal, to determine the information on the transmission channel.
5. Procédé de pré-filtrage selon la revendication 3 ou 4, caractérisé en ce que le signal de test est une séquence prédéterminée ou un signal impulsionnel. 5. Pre-filtering method according to claim 3 or 4, characterized in that the test signal is a predetermined sequence or a pulse signal.
6. Dispositif de pré-filtrage d'un signal de données transmis entre une première entité communicante (EC1) et une seconde entité communicante (EC2) via un canal de transmission filaire, caractérisé en ce qu'il comporte : 6. Device for pre-filtering a data signal transmitted between a first communicating entity (EC1) and a second communicating entity (EC2) via a wire transmission channel, characterized in that it comprises:
- des moyens d'acquisition d'informations (G(f)) sur le canal de transmission filaire par la première entité communicante, au moyen d'une estimation de canal,  means for acquiring information (G (f)) on the wired transmission channel by the first communicating entity, by means of a channel estimation,
- des moyens de détermination d'un pré-filtrage (D(f)) à appliquer au signal de données, en appliquant un retournement temporel aux informations sur le canal de transmission.  means for determining a pre-filtering (D (f)) to be applied to the data signal, by applying a time reversal to the information on the transmission channel.
7. Entité communicante caractérisé en ce qu'elle comporte un dispositif de pré-filtrage selon la revendication 6. 7. communicating entity characterized in that it comprises a pre-filter device according to claim 6.
8. Système comportant des entités communicantes reliées par un canal de transmission filaire, caractérisé en ce qu'il comporte au moins une entité communicante selon la revendication 7. 8. System comprising communicating entities connected by a wired transmission channel, characterized in that it comprises at least one communicating entity according to claim 7.
9. Programme d'ordinateur (P1 ) comportant des instructions pour l'exécution des étapes du procédé selon l'une quelconque des revendications 1 à 5 lorsque ledit programme (P1 ) est exécuté par un ordinateur. 9. Computer program (P1) comprising instructions for performing the steps of the method according to any one of claims 1 to 5 when said program (P1) is executed by a computer.
10. Support d'enregistrement (13) lisible par un ordinateur sur lequel est enregistré un programme d'ordinateur (P1 ) comprenant des instructions pour l'exécution des étapes du procédé selon l'une quelconque des revendications 1 à 5. A computer-readable recording medium (13) on which is stored a computer program (P1) comprising instructions for carrying out the steps of the method according to any one of claims 1 to 5.
PCT/FR2010/051908 2009-09-16 2010-09-14 Pre-filtering of a data signal transmitted between two communicating entities via a wire transmission channel WO2011033217A1 (en)

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CN102158858A (en) * 2011-05-27 2011-08-17 中国人民解放军信息工程大学 Method and device for encrypting MMSE (minimum mean square error) pre-equalization wireless channel based on multipath redundancy
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US9531461B2 (en) 2011-12-23 2016-12-27 Orange Method of grouping transmitter-receiver pairs for communicating over a communications network
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