FR2990580A1 - Method for transmitting broadband signal in communication network, involves transpositioning signal having bandwidth different from that of narrow-band signal in narrow-bands for delivering transposed signal - Google Patents

Abstract

The method involves decomposing a broadband signal (A) into a signal having a bandwidth corresponding to that of a narrow-band signal (B) in a communication network, and another signal having a bandwidth different from that of the narrow-band signal in the communication network. The signal having the bandwidth different from that of the narrow-band signal is transpositioned in narrow-bands (C', D') for delivering a transposed signal. The narrow-band signal and the transposed signal are combined, and the combined narrowband signal is output corresponding to the broadband signal. Independent claims are also included for the following: (1) a device for transmitting a broadband signal in a communication network (2) a method for receiving a broadband signal in a communication network (3) a device for receiving a broadband signal in a communication network (4) a computer program product for transmitting a broadband signal in a communication network.

Description

Methods and devices for transmitting and receiving a broadband signal, corresponding computer program. FIELD OF THE DISCLOSURE The field of the invention is that of radiofrequency communications.

More specifically, the invention relates to the transmission and reception of broadband signals in a communication network having a limited bandwidth, also called narrow band. The invention applies to any communication system whose core network limits the spectral transmission of the signal to the narrow band. In particular, the invention finds applications in the field of broadband telephony. 2. Prior art Broadband telephony differs from conventional telephony in having a larger bandwidth (50-7000Hz instead of 300-3400Hz), which makes it possible to obtain a "high definition" voice quality and therefore significantly improve the quality of listening.

The current communication terminals, DECT type (in English "Digital Enhanced Cordless Telephone", French "enhanced digital wireless phone"), smartphone (in English "smartphone"), handheld, tablet, etc., are thus adapted to this broadband telephony application, and can therefore send or receive communications over a very wide band of frequencies. In particular, they have an increased processing capacity.

However, most current communication networks, such as analogue networks or switched telephone networks, have a "narrowband" backbone, that is to say, allowing only communications on a band. limited frequency, for example of the order of 300 to 3400Hz. It is recalled that existing wired or mobile telephony networks can transmit the voice of a correspondent on a frequency band between 300 and 3400 Hz. Thus, a user subscribed to a high definition telephony service of a telecommunications operator with a terminal with a large bandwidth and a user subscribed to a telephony service of another telecommunications operator, which also has a terminal with a large bandwidth, will not be able to use their respective terminal and can only exchange information on a frequency band limited by the width of the bandwidth of the core network. There is therefore a need for a new technique for transmitting a broadband signal to overcome the constraints related to the bandwidth of the core network. 3. DISCLOSURE OF THE INVENTION The invention proposes a solution that does not have this drawback of the prior art, in the form of a method for transmitting a broadband signal in a communication network, said broadband signal presenting a bandwidth greater than the width of the communication network, called narrow band. According to the invention, the transmission method comprises the following steps: decomposition of the broadband signal into at least two signals, including: a signal having a bandwidth corresponding to that of the communication network, said narrowband signal, and least one signal having a bandwidth distinct from that of the communication network, said narrow out-of-band signal; transposing the narrow-band out-of-band signal (s) in the narrow band, delivering at least one transposed signal; combination of the narrowband signal and the one or more transposed signals, delivering a narrow band combined signal corresponding to the broadband signal. Thus, the invention proposes a new technique for transmitting a broadband signal in a limited frequency band, in the form of a combined narrowband signal. In other words, the broadband signal is "compressed" in a narrow band spectrum. It is thus possible to transmit a signal of better quality between two communication terminals. For example, if the broadband signal to be transmitted is a sound signal, the listening comfort for the recipient is significantly improved, since it recovers all broadband components of the signal and not only narrowband components. According to a particular aspect of the invention, the decomposition step uses a set of filters, comprising: at least one filter making it possible to isolate a portion of the broadband signal corresponding to the narrow band, delivering the narrowband signal, and at least one filter for isolating a low frequency portion of the broadband signal, corresponding to a band of frequencies lower than those of the narrow band, delivering a so-called narrow out-of-band signal; and / or at least one filter making it possible to isolate a high frequency portion of the broadband signal, corresponding to a band of frequencies greater than those of the narrow band, delivering a so-called narrow out-of-band signal. In other words, it is proposed according to the invention to separate the "narrowband" components of the broadband signal (ie the components located at the frequencies between 300 and 3400Hz) from the other components of the broadband signal. (ie components at frequencies between 50 and 300 Hz and between 3400 and 7000 Hz). It is thus possible to treat in a different way the "narrow band" components of the "out-of-band" components. According to another characteristic of the invention, the transposition step shifts the narrow out-of-band signal to a higher frequency band, if it has a lower frequency band than the narrow band, and / or shifts the signal off. narrow band to a lower frequency band if it has a higher frequency band than the narrow band.

In other words, the "out-of-band" components of the broadband signal are transposed up or down to transpose the narrow out-of-band signal (s) within the narrow band. A narrow out-of-band signal with frequencies between 50 and 300Hz is therefore shifted to higher frequencies (between 300 and 3400Hz), while a narrow out-of-band signal with frequencies between 3400 and 7000Hz is shifted to more low frequencies (between 300 and 3400Hz). According to another characteristic of the invention, the combination step implements a multiplexing of the narrow-band signal and the transposed signal or signals. According to a particular embodiment, the decomposition and transposition steps respectively deliver at least two narrow out-of-band signals (called lower and upper narrow out-of-band signals) and at least two corresponding transposed signals (called lower and upper transposed signals), and the transposed signals are mixed before the combination step, for example in an audio mixer (or "audio mixer" in English). It is thus possible to obtain a signal having all the characteristics of the broadband signal to be transmitted, but whose frequency band is limited to the narrow band. In this way, bandwidth limitations of the core network are overcome by transmitting the "full" broadband signal over the narrow band. It is noted that the various characteristics relating to the transmission method according to the invention can be combined or taken in isolation.

In another embodiment, the invention relates to a device for transmitting a broadband signal in a communication network, said broadband signal having a bandwidth width greater than that of the communication network, said narrow band. According to the invention, such a transmission device comprises: means for decomposing the broadband signal into at least two signals, including: a signal having a bandwidth corresponding to that of the communication network, said narrowband signal, and at least one signal having a bandwidth distinct from that of the communication network, said narrow out-of-band signal; means for transposing the narrow-band out-of-band signal (s) in the narrow band, delivering at least one transposed signal; means for combining the narrow-band signal and the transposed signal or signals, delivering a narrow-band combined signal corresponding to the broadband signal.

In this way, part of the intelligence of the communication network in the communication terminal is "deported". Such a transmission device is particularly suitable for implementing the transmission method described above. This is for example a communication terminal type DECT, smart phone, handheld, tablet, etc. It may of course include the various characteristics relating to the transmission method according to the invention. Thus, the features and advantages of this device are the same as those of the transmission method according to the invention, and are not detailed further.

The invention also relates to a method of receiving a signal in a communication network, said received signal corresponding to a broadband signal transmitted according to the transmission method described above. According to the invention, the reception method comprises the steps of: separating, in the received signal, the narrowband signal and the transposed signal or signals; transposing the at least one transposed signal out of the narrow band, delivering the at least one out-of-band signal; reconstruction of the broadband signal from the narrowband signal and the narrow out-of-band signal (s). Such a reception method is particularly adapted to receive a broadband signal transmitted according to the transmission method described above. It thus makes it possible to reconstruct a broadband signal transmitted in a limited frequency band in the form of a combined narrow-band signal. In other words, the broadband signal transmitted in a narrowband form is "decompressed". It is thus possible to recover a signal of better quality at a destination terminal of a communication. Again, if the broadband signal to be transmitted is a sound signal, the listening comfort for the recipient is significantly improved, since it recovers all broadband components of the signal and not only narrowband components. In particular, the decomposition and transposition steps implemented by the transmission method respectively delivering at least two narrow out-of-band signals (so-called upper and lower narrow out-of-band signals) and at least two corresponding transposed signals (called lower transposed signals and higher), the reception method implements a step of separating the signals transposed prior to the transposition step. For example, this separation step uses two filters making it possible to isolate on the one hand the lower transposed signal and on the other hand the higher transposed signal. In another embodiment, the invention relates to a device for receiving a signal in a communication network, said received signal corresponding to a broadband signal transmitted according to the transmission method described above. According to the invention, such a reception device comprises: means for separating, in the signal received, the narrow-band signal and the transposed signal or signals; means for transposing the one or more signals transposed outside the narrow band, delivering the out-of-band signal (s); means for reconstructing the broadband signal from the narrow-band signal and the out-of-band narrow-band signal (s). In this way, part of the intelligence of the communication network in the communication terminal is "deported". Such a reception device is particularly suitable for implementing the reception method described above. This is for example a communication terminal type DECT, smart phone, handheld, tablet, etc. It may of course include the various features relating to the reception method according to the invention. Thus, the features and advantages of this device are the same as those of the reception method according to the invention, and are not detailed further. Another aspect of the invention relates to one or more computer programs comprising instructions for implementing a transmission method and / or a reception method when the program or programs are executed by a processor.

The invention can thus be implemented in various ways, in particular in hardware ("hardware") or software ("software") form. 4. List of Figures Other features and advantages of the invention will appear more clearly on reading the following description of a particular embodiment, given as a simple illustrative and non-limiting example, and the accompanying drawings, among which: Figure 1 shows the main steps of a method of transmitting a broadband signal according to one embodiment of the invention; FIG. 2 illustrates the implementation of a transmission method according to FIG. 1; FIG. 3 shows the frequency bands of the different signals according to the invention; FIG. 4 shows the main steps of a method of receiving a signal according to one embodiment of the invention; FIG. 5 illustrates the implementation of a reception method according to FIG. 4; Figures 6 and 7 show respectively the structure of a transmission device and a receiving device according to a particular embodiment of the invention. 5. DESCRIPTION OF AN EMBODIMENT OF THE INVENTION The general principle of the invention is based on the compression of a broadband signal (also called an extended band signal) over a narrow band, so as to allow the transmission of all the characteristics of the broadband signal in a communication network bounded by a narrowband core network. More precisely, the invention proposes breaking down a "broadband" signal into "narrowband" signals that can be combined before transmission and then separated after reception to recreate the initial broadband signal. In particular, it proposes to compress and decompress a portion of the high and low bands of the broadband signal in a narrow band. An example of the invention for the transmission of sound signals in the context of exchanges between communication terminals is described below. According to the standards in force in this field, the term "broad band" ("wide band" or WB) refers to the range 50-7000Hz and the term "narrow band" refers to the range 300-3400Hz (in English "narrow band Or NB). Of course, the invention is not limited to these two frequency ranges and can be applied for the transmission of any signal having a bandwidth greater than that of the communication network. In relation to FIG. 1, the main steps implemented by a transmission method according to one embodiment of the invention are presented. These different steps are for example implemented within a transmitting communication terminal. To do this, it is considered that the aim is to transmit a broadband signal, denoted A, in a communication network having a narrow band core. Such a broadband signal A has a bandwidth limited by a low frequency BF and a high frequency 20 HF, such as 50Hz BF 300Hz and 3400Hz <HF <7000Hz. During a first step 11, the broadband signal A is decomposed into at least two signals, including: a signal having a bandwidth substantially equal to the narrow band, said narrowband signal B, and at least one signal having a bandwidth distinct from the narrow band, said out-of-band signal C and / or D. For example, as illustrated in Figure 2, the decomposition uses a set of filters to separate the components "narrow band" of broadband signal (ie components at frequencies between 300 and 3400Hz) of the other components of the broadband signal (ie components at frequencies between 50 and 300 Hz and between 3400 and 7000Hz). This set of filters comprises, for example: on a first branch, a high-pass filter having a cut-off frequency at 300 Hz (111) followed by a low-pass filter (in English "Low Shelf") 35 having a cutoff frequency at 3400Hz (112), for isolating a portion of the broadband signal A corresponding to the narrow band, delivering the narrowband signal B, on a second branch, a high pass filter having a cutoff frequency at the low frequency BF (113) followed by a low pass filter having a cutoff frequency at 300Hz (114), for isolating a low frequency portion of the broadband signal A, corresponding to a lower frequency band than those of the narrow band, between BF and 300Hz, delivering a so-called lower out-of-band signal C. This portion of the broadband signal corresponds to the lower part of the signal which does not pass conventionally through the resonant core. water narrow band, but that one nevertheless wishes to transmit; and on a third branch, a high pass filter having a cut-off frequency at 3400 Hz (115) followed by a low-pass filter having a high frequency cut-off frequency HF (116), for isolating a high frequency portion broadband signal A, corresponding to a band of frequencies higher than those of the narrow band, between 3400 and HF Hz, delivering a narrow out-of-band signal said higher D. This portion of the broadband signal corresponds to the upper part of the signal which does not pass conventionally through the core of the narrowband network, but which one nevertheless wishes to transmit.

It is noted that the filters of the second and third branches can be activated or not, depending on the value of the low frequency BF and the high frequency RF of the broadband signal A to be transmitted. Thus, if the value of the low frequency BF is equal to 300 Hz, the broadband signal A to be transmitted does not have any narrow out-of-band components smaller than the narrow band, and the lower narrow out-band signal C is considered to be zero. It is therefore not necessary to activate the filters of the second branch. Similarly, if the value of the high frequency RF is equal to 3400 Hz, the broadband signal A to be transmitted does not have any narrow out-of-band components greater than the narrow band, and the higher narrow out-of-band signal D is considered as no. It is therefore not necessary to activate the filters of the third branch. In a second step 12, the out-of-band out-of-band signal (lower narrow out-of-band signal C and / or higher close out-of-band signal D) is transposed in the narrow band to be transmitted in a narrow-band network. In other words, a narrow out-of-band signal having frequencies between BF and 300Hz (C) is transposed to higher frequencies, and / or a narrow out-of-band signal having frequencies between 3400 and HF (D) is transposed. ) to lower frequencies. A lower transposed signal C 'and / or a higher transposed signal D' are then obtained. For example, as illustrated in FIG. 2, this frequency shift is implemented using sound shift modules (also referred to as "pitch shift" or "pitch shifter"). A first PS + 121 pitch shift module is used to shift the narrow out-of-band components of the wideband signal below 300 Hz (C) upward (i.e. to higher frequencies). For example, this first module implements an offset of (300-BF) Hz, so that the lowest frequency of the lower narrow out-of-band signal (BF) is, after offset, equal to 300Hz. A second PS-122 pitch shifting module is used to shift the narrow out-of-band components of the wideband signal above 3400 Hz (D) downward (i.e. to lower frequencies). For example, this second module implements an offset of (HF-3400) Hz, so that the highest frequency of the upper narrowband out-of-band signal (HF) is, after offset, equal to 3400Hz. If several signals are obtained at the end of the decomposition steps (lower out-of-band signal C and higher out-of-band signal D) and transposition (corresponding transposed signals C 'and D'), and the transposed signals C 'and D' from the PS + 121 and PS-122 sound shift modules can be added by means of an audio mixer for example. In other words, the transposed signals C 'and D' are assembled to form a single signal.

Finally, during a third step 13, the narrow-band signal B and the transposed signal (s) C 'and / or D' are combined by a digital or analog multiplexing operation, delivering a combined narrow-band signal corresponding to the signal broadband transmitted in narrow band form, denoted S. As illustrated in FIG. 2, this combination can be implemented by means of a conventional time-division multiplexer, multiplexing the narrow-band signal B, and the transposed signal (s) C ' and D ', possibly after assembly of the transposed signals C' and D 'to form only one signal. The narrowband combined signal S obtained at the output of the multiplexer 13 therefore corresponds to the broadband signal in a narrow band form, in the sense that it carries the same information as the broadband signal A, but has a band of frequencies limited to the narrow band. . This signal can therefore be transmitted in an analog network that can pass only a narrow band of signal. FIG. 3 illustrates, for a better understanding, the frequency bands of the broadband signal A, the narrow-band signal B, the low-out-of-narrow-band signal C and its transposition C ', and the out-of-band signal D and its transposition D ', for a broadband transmission (WB) in a network having a core narrowband network (NB). The main steps implemented by a method for receiving a broadband signal transmitted in narrowband form, according to one embodiment of the invention, are now presented in relation to FIG. These different steps are for example implemented within a recipient communication terminal. Such a received signal, denoted R, corresponds to the broadband signal transmitted in a narrow band form (S) according to the technique described with reference to FIGS. 1 and 2. During a first step 41, it is separated by an operation of analog or digital demultiplexing the narrow-band signal B and the lower transposed signal (s) C 'and / or higher D' present in the received signal R. For example, as illustrated in FIG. 5, this separation can be implemented by means of FIG. a conventional time analog demultiplexer, demultiplexing the received signal R and making it possible to recover the narrowband signal B and the signal obtained after adding the lower transposed signals C 'and higher D'. The lower transposed signals C 'and higher D' can then be separated. As illustrated in FIG. 5, for example two filters are used to separate the lower transposed signals C 'and higher D'. As a reminder, the lower transposed signal C 'is obtained, on transmission, by shifting the lower narrow out-of-band signal by (300 - BF). The frequency band of the lower transposed signal C' is thus equal to [300 , 3002 / BF] Hz, that is to say [300, x1 Hz. In order to recover the lower narrow out-of-band signal C, it is therefore possible to implement a low-pass filter 411 having a cut-off frequency at X Hz (with X = 3002 / BF)). In the same way, the higher transposed signal D 'is obtained, on transmission, by shifting (3400 - HF) Hz the higher narrow out-of-band signal D. The frequency band of the higher transposed signal D' is thus equal to [34002 / HF, 3400)] Hz, ie [Y, 3400] Hz. To recover the upper narrow-band signal D, it is therefore possible to implement a high-pass filter 412 having a cut-off frequency at Y Hz (with Y = 34002 / HF). During a second step 42, the transposed signal (s) (C ', D') are transposed outside the narrow band, so as to find the out-of-band signal (s) (C, D). In other words, the lower transposed signal (C ') is transposed to lower frequencies, and / or the higher transposed signal (D') is transposed to higher frequencies. We then find the lower narrow-band signals C and / or higher D. For example, as shown in Figure 5, this frequency shift is implemented using tone displacement modules. A first PS-421 pitch shift module enables the narrow-band components of the broadband signal included in the band [300, X1 Hz to be shifted downward (ie to lower frequencies). For example, this first module implement an inverse shift offset implemented by the first module shift in height of sound PS + 121 implemented in the emission. A second PS + 422 pitch shifting module is able to shift upward (ie to higher frequencies) the narrow band components of the broadband signal included in the band [Y, 3400] Hz. For example, this second module an inverse offset to the offset implemented by the second module for shifting in height of the sound PS-122 implemented during transmission.

Finally, in a third step 43, the broadband signal A is reconstructed from the narrowband signal B and the lower narrowband signal C and / or higher D. For example, this reconstruction implements an audio mixer . It is thus possible to find, at a destination terminal, the entire broadband signal, even after passing through a narrow band communication network. Finally, it is noted that the current sound shift modules offer good quality solutions up to an octave shift. By way of example, by taking this setting, it is possible according to the invention to transmit a broadband signal having a frequency band ranging from a low frequency BF equal to 150 Hz (ie an octave below 300 Hz) to a high frequency. HF equal to 6800Hz (an octave above 3400Hz). The values of the frequencies X and Y (illustrated in FIG. 3) are thus respectively equal to 600 Hz (ie an octave above 300 Hz) and 1700 Hz (ie an octave below 3400 Hz). In absolute terms, the limit of the use of the invention with shifts of the same value on either side is when X becomes equal to Y. This point would be reached with a shift in pitch of an octave and ten semitones corresponding to a multiplying factor of 3.36 (% / 3400/300, for a value of 1012 Hz) This limit makes it possible to transmit a broadband signal having a frequency band ranging from 29.8 Hz (300 / 3.36) to 11424Hz (3400x3.36), thus including the broadband spectrum [50.7000] Hz.

Finally, in relation with FIGS. 6 and 7, the simplified structures of a communication terminal respectively implementing a technique for transmitting a broadband signal and a technique for receiving a corresponding signal according to the modes of transmission are presented. embodiment described above. Implemented as a transmitter, such a terminal comprises a memory 61 comprising a buffer memory, a processing unit 62, equipped for example with a microprocessor FP, and driven by the computer program 63, implementing the method of transmitting a broadband signal according to the invention. At initialization, the code instructions of the computer program 63 are for example loaded into a RAM memory before being executed by the processor of the processing unit 62. The processing unit 62 receives as input a signal broadband A to be transmitted. The microprocessor of the processing unit 62 implements the steps of the transmission method described above, according to the instructions of the computer program 63, to "compress" this broadband signal over a narrow band. For this, the terminal comprises, in addition to the buffer memory 61, means for decomposing the broadband signal into at least two signals, including a narrowband signal and at least one narrow out-of-band signal, means for transposing the signal or signals out narrow band in the narrow band, delivering at least one transposed signal, means for combining the narrowband signal and the transposed signal or signals, delivering a combined narrowband signal corresponding to the broadband signal, denoted S. These means are driven by the microprocessor of the processing unit 62. Implemented as a recipient, such a terminal comprises a memory 71 comprising a buffer memory, a processing unit 72, equipped for example with a microprocessor FP, and driven by the programming program. computer 73, implementing the reception method according to the invention. At initialization, the code instructions of the computer program 73 are for example loaded into a RAM memory before being executed by the processor of the processing unit 72. The processing unit 72 receives as input a signal received R, corresponding to a broadband signal S transmitted in narrow band form according to the transmission method of the invention. The microprocessor of the processing unit 72 implements the steps of the reception method described above, according to the instructions of the computer program 73, to "decompress" this received signal. For this, the terminal comprises, in addition to the buffer memory 71, means for separating, in the signal received, the narrow-band signal and the transposed signal or signals, means for transposing the transposed signal or signals outside the narrow band, providing the one or more out-of-band signals, and means for reconstructing the broadband signal A from the narrow-band signal and the one or more out-of-band signals. These means are controlled by the microprocessor of the processing unit 72. The invention is therefore particularly applicable in all telephony transmission systems having ad-hoc terminals and a core network called narrowband, such as the telephone network. switched. It can in particular be implemented in high definition terminals to carry out communications between different countries of the world in analog type EME networks (in English "Egypt and Middle East", in French "Egypt and Middle East") or AMEA (Africa, Middle East and Asia, Africa, Middle East and Asia).

Claims (11)

REVENDICATIONS1. A method of transmitting a broadband signal in a communication network, said broadband signal (A) having a bandwidth of a width greater than that of said communication network, said narrow band, characterized in that said transmission method comprises the following steps: decomposition (11) of said broadband signal (A) into at least two signals, including: o a signal having a bandwidth corresponding to that of said communication network, said narrowband signal (B), and o at least one signal having a bandwidth distinct from that of said communication network, said narrow out-of-band signal (C, D); transposing (12) said at least one narrow out-of-band signal into said narrow band (C ', D'), delivering at least one transposed signal; combining (13) said narrowband signal and said at least one transposed signal, delivering a combined narrowband signal, corresponding to said broadband signal. 2. Transmission method according to claim 1, characterized in that said decomposition step (11) uses a set of filters, comprising: at least one filter for isolating a portion of said broadband signal corresponding to said narrow band providing said narrowband signal, and at least one filter for isolating a low frequency portion of said broadband signal, corresponding to a lower frequency band than those of said narrowband, delivering a so-called narrow out-of-band signal; and / or at least one filter making it possible to isolate a high frequency portion of said broadband signal, corresponding to a band of frequencies higher than those of said narrow band, delivering a so-called narrow out-of-band signal. A transmission method according to claim 1, characterized in that said transposing step (12) shifts said at least one narrow out-of-band signal to a higher frequency band, if it has a lower frequency band than those of said narrow band, and / or shifts said at least one narrow out-of-band signal to a lower frequency band, if it has a higher frequency band than those of said narrow band. 4. Transmission method according to claim 1, characterized in that said combining step (13) implements a multiplexing of said narrowband signal and said at least one transposed signal. A transmission method according to claim 1, characterized in that said decomposing (11) and transposing steps (12) respectively deliver at least two narrow out-of-band signals and at least two corresponding transposed signals, and in that said signals transposed are mixed prior to said combining step. 6. Transmission method according to claim 1, characterized in that said broadband signal is a sound signal. 7. Device for transmitting a broadband signal in a communication network, said broadband signal (A) having a bandwidth greater in width than that of said communication network, said narrow band, characterized in that said transmission device comprises: means for decomposing (11) said broadband signal (A) into at least two signals, including: o a signal having a bandwidth corresponding to that of said communication network, said narrowband signal (B), and o to least one signal having a bandwidth distinct from that of said communication network, said narrow out-of-band signal (C, D); means for transposing (12) said at least one narrow out-of-band signal into said narrow band (C ', D'), delivering at least one transposed signal; combining means (13) of said narrowband signal and said at least one transposed signal, delivering a combined narrowband signal, corresponding to said broadband signal. A method of receiving a signal in a communication network, said received signal corresponding to a broadband signal transmitted according to the transmission method of claim 1, characterized in that said receiving method comprises the following steps: separation ( 41), in said received signal, said narrowband signal (B) and said at least one transposed signal (C ', D'); transposing (42) said at least one transposed signal (C ', D') out of said narrow band, delivering said at least one narrow out-of-band signal (C, D); reconstructing (43) said broadband signal (A) from said narrowband signal (B) and said at least one narrow out-of-band signal (C, D). 9. Reception method according to claim 8, characterized in that said steps of decomposition and transposition implemented by the transmission method respectively delivering at least two narrow out-of-band signals and at least two corresponding transposed signals, said method of reception implements a step of separating said transposed signals prior to said transposition step. 10. Apparatus for receiving a signal in a communication network, said received signal corresponding to a broadband signal transmitted according to the transmission method of claim 1, characterized in that said reception device comprises: separation means ( 41), in said received signal, said narrowband signal (B) and said at least one transposed signal (C ', D'), means for transposing (42) said at least one transposed signal (C ', D') outside said narrow band, delivering said at least one narrow out-of-band signal (C, D); means for reconstructing (43) said broadband signal (A) from said narrowband signal (B) and said at least one narrow out-of-band signal (C, D). A computer program comprising instructions for carrying out a method according to claim 1 or claim 8 when the program is executed by a processor.