FR2786639A1 - Data transmission by multi-carrier radio link includes estimation of reliability of channels to determine channels most suited to most important data - Google Patents

Abstract

The system ensure optimum transmission of critical data. The procedure provides transmission of data in the form of symbols transmitted on an electromagnetic channel. A measurement of the importance of data is attributed to each group of data to be transmitted, and the reliability of the transmission of carriers is dynamically estimated. The most important data is transmitted on the most reliable carriers, whilst the other data is transmitted on the other carriers in descending order of reliability, matching in this the decreasing importance of the data. The system may operate with a data source (10), a multi-carrier modulator (50), and a radio-frequency interface (60) leading to the transmission channel, with corresponding demodulation circuitry at the receiving end.

Description

The invention relates to the field of information transmission methods

  as an electromagnetic signal. It relates more particularly to the allocation of carrier frequencies for

  transmission using multicarrier type modulation.

  It is recalled that an information transmission system generally transmits symbols (each symbol being for example a sequence of binary data) to be transmitted in series, thus occupying a frequency band which must necessarily be greater than the reverse the duration of a symbol. When the symbol rate becomes too high, it is impossible to guarantee that the channel has identical amplitude and phase characteristics over the entire frequency space constituting the passband. These distortions induce interference between symbols, which must be fought with a device called equalizer, which is

relatively complex.

  One possibility to avoid this problem is to distribute the signal (formed by the sequence of symbols) to be transmitted over a large number of carriers in parallel, individually modulated at low speed. Because the bit rate is low for each carrier, the necessary bandwidth is smaller and therefore it is likely that the frequency and phase characteristics

  will be identical for all the frequencies constituting this band.

  This technique is called frequency division multiplexing, the position of the carriers being chosen so as to avoid interference between them. A special case is then orthogonal frequency division multiplexing (in English Orthogonal Frequency Division Multiplex, or OFDM according to the term commonly used by those skilled in the art), for which the spacing between two adjacent subcarriers (sub closest carriers in terms of frequency) corresponds to the inverse of the duration of an emitted symbol. A standard type multicarrier transmission system (see FIG. 1) comprises a data source 10, a parallel serial converter connected to a series of subcarriers, a multicarrier modulator 50 which transmits the data to an RF transmitter 60. In such a standard system , the

  data are distributed sequentially on the different subcarriers.

  For example, for a system using eight subcarriers, the data bearing the numbers 0, 8, 16, 24 will be transmitted on the subcarrier 30 of frequency l01, the data bearing the numbers 1, 9, 17, 25 will be transmitted on the frequency subcarrier 02 etc. It turns out that most of the transmission channels used (and in particular the so-called "radio channels") have transmission characteristics (attenuation, noise, phase shift, etc.) which vary according to the carrier frequency used. Some channels have characteristics that vary over time, for example because of so-called "multi-path" effects, because of elements entering the channel, etc. FIG. 2 presents an example with a symbolic representation of the transmission quality (SNR signal / noise ratio) on each of the sub-carriers in the case of eight sub-carriers, at two different times t = t, and t = t2. The transmission characteristics for each frequency varying over time, it can be seen in the example that the data X6

  is correctly transmitted at time t ", but may be erroneous at time t2.

  The notion of efficiency of such a multicarrier transmission is then linked to the resolution of the following problem with which power P must be transmitted to ensure the transmission of a certain data rate D with a quality Q in a physical transmission channel given? This efficiency can be defined as the ratio (bit rate x quality) / transmitted power. The solution generally adopted for this transmission efficiency problem is a compromise between, on the one hand, the energy emitted during transmission on the transmission channel. transmission and, on the other hand, the admissible error rate for the data transmitted. The operating principle of most of the existing devices is to increase the transmission power to counteract the degradation of the transmission channel and transmit all the data with the

  guarantee of an error rate below a predetermined threshold.

  Several techniques have been exposed to improve efficiency

of the transmission.

  These techniques are based on a different coding for the data

  considered the most important, before sending on the transmission channel.

  A technique described in US Pat. No. 5,425,050 introduces the concept of "pyramidal coding" by proposing the idea of creating two classes of data requiring two different levels of transmission quality. US Patent 5,467,132 describes a method for coding

  the data differently depending on their importance.

  Other techniques are based on a dynamic estimation of the transmission quality on each subcarrier, and on a modification of the number of bits per symbol transmitted to take account of this variation in transmission quality (we can cite in particular the patent document US 5

479,447).

  In summary, the conventional solutions to this problem of multicarrier transmission efficiency are: - increase in the transmission power so as to always transmit with a sufficient signal / noise level,

  - transmission channel survey and elimination of sub-

  most disturbed carriers, - addition of redundancy in the data by coding,

  - modification of the number of bits per symbol for the sub-

disturbed carriers.

  All these solutions lead to an increase in energy

  issued to transmit the same stream of data with constant quality.

  The present invention intends to propose a new method for transmitting information using multicarrier modulation, this method

  with better transmission efficiency.

  According to a second objective of the invention, it also uses

  noisy carriers, usually rejected by conventional techniques.

  According to another objective, the invention proposes a dynamic transmission method, which makes it possible to maintain optimum efficiency during

  variations in the characteristics of the transmission channel.

  Another object of the invention is to guarantee the correct transmission of the most important data, subject to a signal ratio

sufficient noise (SNR).

  The method also aims to reduce the energy emitted during transmission, compared to existing techniques, with equal efficiency. To this end, the method of transmitting data in the form of symbols transmitted on an electromagnetic channel is characterized in that a measure of importance is attributed to each data or group of data to be transmitted, in that the reliability of transmission of the carriers is estimated dynamically, and in that the most important data are transmitted on the most reliable carriers at all times, the other data being transmitted on the carriers of decreasing reliability, in order of decreasing importance

Datas.

  It is understood that this method makes it possible to take into account the importance of the data, not at the time of coding, but at the time of allocation of the transmission frequency, in an adaptive manner, when the reliability of the carriers (error rate during transmission) varies, and even taking advantage of very noisy carriers, for the transfer of less important data. This possible use of noisy carriers allows a gain in efficiency compared to conventional techniques, in which these carriers would have been avoided, and in which a single error rate common to all the data to be transmitted is defined beforehand. In addition, the dynamic nature of the process makes it possible to guarantee that in the event of a sharp deterioration in the reliability of the channel. transmission, the most important data will always be transmitted as a priority (ie on the most reliable channel) with the highest quality

possible at this time.

  Taking into account the importance of the data allows an energy saving compared to current processes because it can thus reduce the transmission power without altering the transmission quality of the

  important data, so without risking the loss of the substance of the message.

  This is an improvement compared to current methods in which one transmits with sufficient transmission power to guarantee

  a given signal-to-noise level (SNR) for all the frequencies used.

  According to a preferred implementation, the method of transmitting data from a local device to a remote device by a transmission channel, the local device comprising a data source, a multicarrier modulator, a radio-frequency interface, an inserted demodulator downstream of the radio-frequency interface to process the signal received on the transmission channel, coming from another remote transceiver, a pre-modulator part, inserted upstream of the multicarrier modulator and, a post-demodulator part, inserted downstream of the multicarrier demodulator, comprises operations of: - presentation by the pre-modulator part to the different inputs of the modulator, each input corresponding to a subcarrier, of the different data to be transmitted according to their importance and the level of transmission quality of each subcarrier, - insertion by the pre-modulator into the data of a signal representative d e the transmission quality observed on each subcarrier in the "return" direction, - insertion by the pre-modulator in the data of a signal representative of the order in which the various data to be transmitted at the input are arranged of the pre-modulator, - classification of the data by the pre-modulator according to their importance, - generation by the pre-modulator of the control signal of the allocation unit data / frequencies, - analysis by the post-demodulator part , of the transmission channel so as to provide a signal representative of the quality of the transmission of each subcarrier in the "return" direction, and - extraction by the post-demodulator of a signal representative of the quality of transmission observed by a remote receiver device on each subcarrier in the so-called "go" direction, - extraction by the post-demodulator of the DP signal (Data Position) representative of the order in which the d different data to be transmitted to the input of the pre-modulator of remote device B. - serialization by the post demodulator of the data received in

DP signal function.

  The invention also relates to a device for transmitting data to a remote device via a transmission channel, comprising a data source, a multicarrier modulator which transmits the data to a radio frequency interface, a demodulator inserted downstream of the radio interface frequencies for processing the signal received on the transmission channel, coming from the remote device, characterized in that the device according to the invention also comprises a pre-modulator means adapted to present to the different inputs of the modulator, each input corresponding to a subcarrier , the different data to be transmitted according to a classification of

their importance.

  According to a preferred embodiment, the pre-modulator means comprises: a means of presentation to the different inputs of the modulator, each input corresponding to a subcarrier, of the different data to be transmitted according to a classification of their importance as well as the level transmission quality of each subcarrier in the "forward" direction, and a means of inserting into the data to be transmitted a signal representative of the transmission quality observed on each subcarrier in the "return" direction , - and a means of insertion by the pre-modulator into the data of a DP signal representative of the order in which the various data to be transmitted are arranged at the input of the pre-modulator, - and a classification means data according to their importance, - and a means of generating the control signal of the allocation unit data / frequencies, and the device also comprises a post-demodula means tor comprising: a means of extracting the signal from the demodulator of a signal representative of the quality of transmission observed by the remote device on each subcarrier in the "forward" direction, said signal being generated by the remote device, - and a means of analysis of the transmission channel so as to

  provide the signal representative of the transmission quality of each sub-

  carrier in the "return" direction, - a means of extracting from the signal from the demodulator a DP signal, representative of the order in which the various data to be transmitted were arranged at the input of the pre-modulator of the remote device B. and a means of serializing the data received as a function of

this DP signal.

  The invention also relates to a telephone, a camera, a printer, a scanner, a camera, a computer, a fax machine, a television set, an audio / video player, characterized in that they include a

  device as succinctly set out above.

  The invention also relates to: - a means of storing information readable by a computer or a microprocessor retaining instructions of a computer program characterized in that it allows the implementation of the method of the invention as briefly described above, and - a removable information storage means, partially or totally, and readable by a computer or a microprocessor keeping instructions of a computer program characterized in that it allows the setting

  using the process of the invention as succinctly described above.

  The advantages of this device, this network, this phone, this camera, this printer, this scanner, this camera, this computer, this fax machine, this TV, this audio / video player, and of these storage means being the same as those of

  process as succinctly explained above, they are not recalled here.

  The description and the drawings which follow will allow better

  understand the objects and advantages of the invention. It is clear that this

  description is given by way of example, and is not limiting. In

  the drawings: FIG. 1 represents the block diagram of a standard transmission system by multicarrier modulation; - Figure 2 symbolically illustrates the transmission quality of each subcarrier in an example of transmission by a standard multicarrier system; - Figure 3 is a block diagram of the device according to the invention, according to a presentation similar to Figure 1; - Figure 4 illustrates the quality of transmission of each subcarrier in an example of transmission by a system according to the invention, according to a presentation similar to Figure 2; - Figure 5 illustrates an example of DS signal generation in the case of digitization of an analog source; - Figure 6 shows an algorithm performing the allocation of data on the different subcarriers; FIG. 7 shows the block diagram of a multicarrier transmission system including the calculation means necessary for the implementation of

  the data allocation algorithm in Figure 6.

  As can be seen in FIG. 3, which must be compared with FIG. I representing a standard multicarrier transmission system, there is in a device A according to the invention a data source 10, a

  multicarrier modulator 50 which transmits the data to a radio interface

  RF frequency 60. A demodulator 70 is inserted downstream of the radio interface.

  frequency RF 60 to process the signal received on the transmission channel, coming from another remote transceiver B (identical to device A)

not shown in the figure.

  The data source 10 generates a binary data stream which

constitutes the signal to be transmitted.

  In a conventional device not in accordance with the invention, this "series" type train is converted into a "parallel" train by the series-> parallel converter 20, so as to reduce the bit rate of the modulating signals. This parallel train is then sent to the multi-carrier modulator 50 which performs

  the modulation required for transmission on the chosen transmission channel.

  In the example presented, the serial train is transformed into an eight-bit parallel train. In this case, if the bit rate of the binary source is D, the bit rate

  of each train at the output of the serial -> parallel converter 20 will therefore be D / 8.

  Each of these trains then modulates a subcarrier using modulators 30, 31 ..., 37 (eight subcarriers in this example); modulation can be of different types: phase, amplitude or frequency modulation, according to conventional techniques which are beyond the scope of the invention.

  A summator 40 then adds all of the sub-

  carriers modulated so as to obtain the global signal S (t) which is then transmitted to the "Radio Frequency" interface (also noted RF) 60 It is important to note that the binary data X0, X1, X2, ... X7 , from converter 20 and used to modulate the subcarriers can be made up of several bits. They will therefore more generally be called "symbols". In this case, the modulations used can be complex (for example according to types known to those skilled in the art under the names QPSK, 8PSK, 16QAM, 64QAM, etc.) in order to improve the spectral efficiency. These elements constitute a conventional multi-carrier device, known to those skilled in the art. They will therefore not be detailed further in the

present description.

  On the other hand, the device according to the invention also comprises two parts which do not exist in conventional devices: namely, on the one hand, a pre-modulator part 100, inserted upstream of the conventional multi-carrier modulator (replacing the serial converter - parallel 20) and, on the other hand, a post-demodulator part 200, inserted downstream of the demodulator

multi-carrier 70.

  In summary, the pre-modulator part 100 presents to the different inputs of the modulator 50 (an input corresponding to each subcarrier 30, 31, etc.), the different data to be transmitted according to their

  importance and level of transmission quality of each subcarrier.

  This pre-modulator 100 also inserts into the data a

  signal 240 representative of the transmission quality observed on each sub-

  carrier in the so-called "return" direction, also noted B-> A.

  This pre-modulator 100 also inserts into the data a signal representative of the order of said data in the serial train, in the

direction A-> B.

  The post-demodulator part 200 performs on the one hand the analysis of the channel so as to provide the signal 240 representative of the quality of the transmission of each subcarrier 30, 31 ... in the so-called "return" direction, and , on the other hand, extracts a signal 230 representative of the transmission quality observed by a remote receiving device on each subcarrier in the

  direction called "go", also noted A-> B, this signal 230 being inserted by the pre-

  modulator 100 of the remote device located at the other end of the channel, so

  to control the local pre-modulator module 100.

  This post-demodulator 200 also extracts a signal "DP" 235 representative of the order in which the various data were arranged.

  transmit to the input of the remote transmitter's pre-modulator.

  More precisely, the pre-modulator part 100, inserted upstream of the multi-carrier modulator 50 consists of a data allocation unit "Data Allocation" 130, of a data insertion control unit "Control Data Insertion" 115, a data classification unit "Data Classification" 110 and a frequency allocation unit "Frequency

Allowance "120.

  The post-demodulator part 200 inserted downstream of the demodulator consists of a "Channel Analysis" channel analysis unit 220, of a frequency classification signal extractor unit 210 "FCD extractor", of a unit of extraction 215 "DP extractor" of the signal representative of the order of the data in the serial train presented to the remote pre-modulator, from a unit of

  "Data Serialization" 205 serialization (also called serializer).

  The electronic implementation details of these parts result from

  transmission method, as will be explained here.

  The channel analysis unit 220 performs the analysis of the transmission channel, for example, by evaluating different characteristics of known pilot signals inserted by the remote device B (located at the other end of the transmission channel). There are several analysis techniques (pilot signals at fixed frequencies, at frequencies sliding in time etc.) known from

one skilled in the art.

  The result of this analysis constitutes the signal 240 (signal called FCD or "Frequency Classification Data"). This is supplied to the control data insertion unit 115, which inserts it into the data stream to be transmitted, so as to inform the remote device B of the behavior of this transmission channel. This FCD signal 240 is therefore representative of the characteristics of the channel in the direction B-, A, as observed by the local device A. The signal extraction unit 210 FCD extracts from the data received and demodulated by the demodulator 70 a signal FCD 230, signal generated and inserted by the channel analysis parts 220 and insertion of control data 115 of the remote device B. This signal FCD 230 is representative of the characteristics of the channel in the direction A-> B, such as observed by the remote device B. The signal extraction unit 215 "DP extractor" extracts from the data received and demodulated by the demodulator 70 a signal 235, signal generated and inserted by the frequency allocation unit 120 and d insertion of control data 115 from the remote device B. This signal 235 is representative of the order of the data in the serial train presented to the pre-modulator 100 of the remote device B. This signal 235 will be used by the unit serialization 205 so as to transform the parallel train of the data received into a serial train identical to that presented to the pre-modulator of the remote device B. The classification unit of data to be transmitted 110 generates a DS (Data Significance) signal 111 representative the importance of each piece of data provided by the source. An example of generating a DS signal is

given figure 5.

  The frequency allocation unit 120 decides the distribution of the data on the different subcarriers on the basis of the signals DS 111 and FCD 230 (in the direction A - B), and possibly other parameters supplied by the user , and consequently generates a DAC 125 command signal

  Data Allocation Command.

  The frequency allocation unit 120 also provides a signal (Data Position) representative of the order that the data allocated to the different subcarriers had relatively to each other in the serial train presented to the pre-modulator 100. The signal 135 is used by the "Control Data Insertion" unit 115 which inserts it into the data to be transmitted so as to allow the serialization unit 205 of the remote device B to

  reclassify this data correctly after transmission.

  Different data-frequency allocation algorithms can be used. An example of a simple algorithm is given in Figure 6, not for

limiting.

  The data allocation control signal DAC 125 is sent to the data allocation unit 130 which then routes each data item supplied by the source 10 to the subcarrier.

  (input of modulator 50) chosen by the frequency allocation unit 120.

  For the correct functioning of the invention, the data supplied to the data allocation unit 130, to the control data insertion unit 115 and to the frequency allocation unit 120, must be correctly phased; which is done by using devices well known to those skilled in the art (for example a delay line for delaying the signal which is ahead). The complex signal from the modulator 50 is then transmitted to the RF unit 60 for transmission via the channel to the remote device B. FIG. 4 then illustrates an example of the distribution of the symbols to be transmitted on the different subcarriers for two instants t = tl and t = t2 different, in the case of a multicarrier transmission device according to the invention. The data index (0 to 7) corresponds to the order generated by the source 10. The variations in the characteristics of the channel are symbolized by the variation in the amplitude of arrows representing the subcarriers (signal / noise ratio, this which amounts for example to observing the attenuation of the channel at the

frequency considered).

  Assuming that the data is not of equal importance, and for example that the data with the highest index is the most important, we see that the important data will be correctly transmitted to all

  instant regardless of channel variations.

  Figure 5 then illustrates an example of DS signal generation

  111 (Data Significance) by the classification unit of data to be sent 110.

  In this particular case, the source 10 used comprises an analog source

  11, digitized before transmission. An analog converter unit

  digital 12 (ADC) generates a continuous series of bits for this purpose, each block of eight bits being representative of an analog value to be transmitted. By synchronizing the analog-digital converter unit 12 and the data classification unit 110, it is possible to simply generate a signal

  DS 111 which will take a different value for each bit.

  For example, if, in a set of bits DO, ... D7 supplied by the converter 12, the first bit D7 is the most significant, it suffices to make it correspond to a signal of maximum importance (i.e. index 7 here). Then index 6 is matched to the next bit D6, index 5 is bit D5 etc. This can be easily done using a 3-bit counter to perform the Data Classification function. This counter will be incremented by the converter's serial clock and initialized to 0 each time

new analog data.

  FIG. 6 gives an example of an algorithm performing the allocation of the data on the different subcarriers as a function of the level of

  disturbance measured on each subcarrier and the importance of the data.

  This algorithm is intended to be implemented by the allocation unit

frequencies 120.

  During the initialization step 310, the device reads the information

  contained in the FCD 230 and DS 111 signals and stores them.

  The first step 320 then consists in classifying the sub-

  carriers in descending order of disturbance and to store in memory the

table thus obtained.

  The following step 330 consists in classifying the indices of the data to be transmitted in order of increasing importance by using the information contained in the DS signal 111. The result of this classification is also

stored in memory.

  The next step 340 consists in transmitting the data allocation control signal DAC 125 to the data allocation unit 130, this DAC signal 125 being in fact composed of pairs (subcarriers, data index) After the exit of each couple, a test 350 is carried out to check whether all of the couples have been supplied (there are as many couples as there are subcarriers). If the test is negative, the following torque is provided; if the test is

positive, we go to step 360.

  The next step 360 consists in transmitting the signal 135 "Data Position", representative of the order that the data allocated to the different subcarriers had relatively to each other in the serial train presented to the pre-modulator, to the unit "Control Data Insertion" 115 which inserts it

in the data to be transmitted ..

  Then, we return to the initialization step 310 in order to

  prepare to supply the next allocation table (signal DAC 125).

  It should be noted that the updating of the FCD 230 signal can be done at a slower rate than that of the data to be transmitted. In this case, step 320 is not to be performed for each new piece of data, but only when

signal FCD 230 is refreshed.

  In a preferred embodiment, when the data always have the same level of relative importance (Analog-digital conversion for example), the Data Position signal can be omitted, knowing the order of classification of the frequencies then being sufficient to reclassify

data at reception.

  FIG. 7 describes an embodiment of the invention including a CPU 400, a temporary data storage unit 410, a program storage unit 420, character input means (keyboard for example) 430, image reproduction means 440

  and means allowing inputs-outputs 450.

  The algorithm described above can easily be integrated into this embodiment by a person skilled in the art, but other means of implementation are possible. In a variant using a coaxial cable transmission, the channel is "fixed", in that its quality does not vary over time, and it is therefore not necessary to estimate the channel, but the classification of the data can still allow the high frequencies which are the most attenuated to be used on this type of channel, by sending the data there

of lesser importance.

  It should be noted that the data source 10 could for example be an image compression system using progressive coding techniques such as coding in sub-bands, by fractals, by transform (Discrete Cosine Transform: DCT, wavelets) , as a video object (MPEG4); these systems naturally producing signals of variable importance, the data classification unit 110 can be reduced to a coding of this

level of importance.

  Furthermore, in an application of the invention with a view to another objective, it is possible to choose to favor an energy saving by using only the carriers which are very little noisy and therefore by transmitting at low power,

  even reduce the speed of the transmission (since there are fewer sub-

  carriers used simultaneously) and therefore take a little longer to transmit the message. The transmission principle remains

substantially analogous.

  The scope of the present invention is not limited to the details of the above embodiments considered by way of example, but extends to

  contrary to modifications within the reach of ordinary skill in the art.

Claims (19)

  1. A method of transmitting groups of data on a transmission channel using a multicarrier type modulation, characterized in that a measure of importance is assigned to each data or group of data to be transmitted, in that the reliability of transmission of carriers is estimated dynamically, and in that the most important data are transmitted on the most reliable carriers at all times, the other data being transmitted on the carriers of decreasing reliability, in order of importance decreasing data.   2. Method for transmitting data from a local device A to a remote device B by a transmission channel, the local device A comprising a data source (10), a multicarrier modulator (50), an RF radio frequency interface ( 60), a demodulator (70) inserted downstream of the radio frequency RF interface (60) to process the signal received on the transmission channel.   transmission, from another remote transceiver B, a pre-   modulator (100), inserted upstream of the multi-carrier modulator (50) and, a post-demodulator part (200), inserted downstream of the multi-carrier demodulator (70), characterized in that it comprises operations of presentation by the pre part -modulator (100) at the different inputs of the modulator (50), each input corresponding to a subcarrier, different data to be transmitted according to their importance and the level of transmission quality of each subcarrier (30, 31 .. .) in the direction "go" A-> B, - insertion by the pre-modulator (100) in the data of a signal (240) representative of the transmission quality observed on each subcarrier in the direction "return "B-> A, - insertion by the pre-modulator (100) into the data of a signal (135) representative of the order in which the various data to be transmitted are arranged at the input of the pre-modulator (100 ), - analysis by the post-demodulator part (200), of the channel of transmission so as to provide a signal (240) representative of the quality of the transmission of each subcarrier in the "return" direction B-> A, - extraction by the post-demodulator (200) of a signal (230 ) representative of the transmission quality observed by a remote receiver device B on each subcarrier (30, 31 ...) in the "go" direction A-> B, and - extraction from the signal from the demodulator of a signal DP, representative of the order in which the various data to be transmitted were arranged at the input of the pre-modulator of the remote device B. - serialization by the post-demodulator (200) of the data received based on this DP signal.   3. Device A for transmitting data to a remote device B by a transmission channel, comprising a data source (10), a multi-carrier modulator (50) which transmits the data to an RF radio frequency interface (60), a demodulator (70) inserted downstream of the radio frequency RF interface (60) to process the signal received on the transmission channel, coming from the remote device B, characterized in that the device according to the invention also includes a pre-modulator means (100) adapted to present to the different inputs of the modulator (50), each input corresponding to a given subcarrier, the different data to be transmitted according to a classification of their importance.   4. Device according to claim 3, characterized in that the pre-modulator means (100) comprises: - a presentation means (130) to the different inputs of the modulator (50) each input corresponding to a subcarrier, of the different data to forward based on a ranking of their   importance as well as the level of transmission quality of each sub-   carrier (30, 31 ...) in the direction "go" A -> B, - a means of insertion (115) in the data to be transmitted of a signal (240) representative of the quality of transmission observed on each subcarrier in the "return" direction B-> A, - and a means of insertion (115) in the data of a signal (135) representative of the order in which the various data to be transmitted are arranged the input of the pre-modulator (100), and in that the device also comprises: - a post-demodulator means (200) comprising: - an extraction means (210) from the signal from the demodulator (70) an FCD signal (230) representative of the transmission quality observed by the remote device B on each subcarrier (30, 31 ...) in the "go" direction A-> B, said signal being generated by the remote device B, - and an analysis means (220) of the transmission channel so as to provide the signal (240) representative of the quality of the transmission of each sub-po rteuse in the "return" direction B-> A, - and a means of extraction (215) from the signal from the demodulator (70) of a signal (235) representative of the order in which the various were arranged data to be transmitted to the input of the pre-modulator of the remote device B. - and a serialization means (205) of the data received as a function of the signal (235) representative of the order in which the various data to be transmitted were arranged the input of the remote device B pre-modulator.   5. Device according to any one of claims 3 to 4,   characterized in that the pre-modulator means (100) also includes a data classification unit (110) and a frequency allocation unit (120).   6. Device according to claim 5, characterized in that the classification unit of data to be transmitted (110) comprises means adapted to generate a DS signal (111) representative of the importance of each data provided by the source.   7. Device according to claim 5, characterized in that the frequency allocation unit (120) comprises means adapted to generate a DAC signal (125) for data allocation control (determining the distribution of the data on the different sub-carriers), from data including the signals DS (111) and FCD (230) A-> B and means adapted to generate a signal (135) representative of the order in which the   various data to be transmitted to the input of the pre-modulator (100).   8. Device according to claim 5, characterized in that the frequency allocation unit (120) comprises means adapted to perform operations: - initialization (310), in which the frequency allocation unit (120) reads the information contained in the signals FCD (230) and DS (111) and of memorization, - of classification (320) of the subcarriers by order of disturbance and memorization of the table thus obtained, - of classification (330 ) indices of the data to be transmitted in order of importance using the information contained in the DS signal (111) and memorizing the result of this classification, transmission (335) of the signal (135) relative position of the data to the others to the unit for inserting in the data to be transmitted (115), - for transmitting (340) the DAC signal (125) of data allocation command to the data allocation unit (130), this DAC signal (125) being in fact composed of couples (subcarriers, data index) - test to check whether all the couples have been supplied, so that if the test is negative, the following couple is supplied; and if the test is   positive, we return to the initialization step (310).   9. Device according to claim 5, characterized in that the data allocation unit (130) comprises means adapted to transfer each data item supplied by the source (10) to the subcarrier defined by the unit frequency allocation (120) in the control DAC signal (125) data allocation.   10. Device for transmitting data from device A to a   remote device B by a transmission channel, according to one of claims   3 to 9, characterized in that it comprises a CPU calculation unit (400), a temporary data storage unit (410), a program storage unit (420), means for entering characters (keyboard by example) (430), image restitution means (440) and means allowing inputs-outputs 450).   11. Telephone, characterized in that it comprises a device according to   any one of claims 3 to 9.   12. Photographic camera, characterized in that it comprises a   device according to any one of claims 3 to 9.   13. Printer, characterized in that it includes a device   according to any one of claims 3 to 9.   14. Scanner, characterized in that it comprises a device according to   any one of claims 3 to 9.   15. Camera, characterized in that it comprises a device   according to any one of claims 3 to 9.   16. Computer, characterized in that it comprises a device according to   any one of claims 3 to 9.   17. Fax machine, characterized in that it includes a device   according to any one of claims 3 to 9.   18. Television, characterized in that it comprises a device according to   any one of claims 3 to 9.   19. Audio / video player, characterized in that it includes a   device according to any one of claims 3 to 9.