Communication method and omamrc system comprising a selection during retransmissions taking into account the throughput of the sources and a single exchange of csi

Abstract

The present invention relates to a communication method which comprises transmission of a frame transporting messages and is intended for a telecommunication system having N nodes, including M sources (Formula I), N ≥ M ≥ 2, and one destination (D). Transmission comprises a maximum number of M + T max time intervals per transmitted frame, distributed between a first<sp / > phase and a second<sp / > phase. The selection of the sources to be assisted during the second<sp / > phase takes into account the predetermined numbers of retransmission intervals that are necessary and sufficient for the destination to decode the sources not yet correctly decoded and the throughputs assigned to the sources.

Description

[0001]DESCRIPTION TITLE: OMAMRC communication method and system with a selection during retransmissions taking into account the flow rate of the sources and a single CSI exchange Field of the invention The present invention relates to the field of digital communications. Within this field, the invention relates more particularly to the transmission of coded data within a telecommunications system defined by at least two sources and a destination with relaying by at least one node which can be one of the sources or a relay in the case where one or more relays complete the system. It is understood that a relay does not have a message to transmit. A relay is a node dedicated to relaying messages from the sources while a source has its own message to transmit and can also in certain cases relay messages from other sources, i.e. the source is said to be cooperative in this case.There are many relaying techniques known by their English names: "amplify and forward", "decode and forward", "compress-and-forward", "non-orthogonal amplify and forward", "dynamic decode and forward", etc. The invention applies in particular, but not exclusively, to the transmission of data via mobile networks, for example for real-time applications, or via, for example, sensor networks. Such a sensor network is a multi-user network, consisting of several sources, several relays and a recipient using an orthogonal multiple access scheme in time of the transmission channel between the relays and the sources, noted OMAMRC ("Orthogonal Multiple-Access Multiple-Relay Channel" according to English terminology).Prior Art The considered OMAMRC telecommunication system illustrated by Figure 1 has ^^ nodes and a destination with an implementation of a time orthogonal multiple access scheme of the transmission channel that applies between the ^^ nodes. The ^^ nodes include ^^ sources and ^^ − ^^ = ^^ relays. The maximum number of time slots per transmitted frame is ^^ + ^^. ^^ ^^ ^^ with M intervals allocated during a first phase to the successive transmission of the M sources and ^^^^ ^^ ^^ ^^≤ ^^ ^^ ^^ ^^intervals for one or more cooperative transmissions allocated during a second phase to one or more nodes selected by the destination according to a selection strategy. Such an OMAMRC transmission system implementing a selection strategy during the second phase is known from the article [1]. The OMAMRC transmission system described is such that each of the sources can operate at different times either exclusively as a source or as a relay node. The node terminology covers both a relay and a source acting as a relay node or as a source. A relay is distinguished from a source because it has no message to transmit of its own, i.e. it only retransmits messages from other nodes. The links between the different nodes of the system are subject to slow fading and white Gaussian noise.Knowledge of all the links in the system (CSI: Channel State Information) by the destination is not available. Indeed, the links between sources, between relays, between relays and sources are not directly observable by the destination and their knowledge by the destination requires an exchange of information between the sources, the relays and the destination. To limit the cost of the feedback overhead, represented by dotted lines in Figure 1, only information on the channel distribution / statistics (CDI: Channel Distribution Information) of all the links, e.g. average quality (e.g. average SNR, average SINR) of all the links, is assumed to be known by the destination in order to determine the rates allocated to the sources.Link adaptation is said to be slow type, that is to say that before any transmission, the destination allocates initial rates to the sources knowing the distribution of all the channels (CDI: Channel Distribution Information). In general, it is possible to go back to the CDI distribution on the basis of the knowledge of the average SNR or SINR of each link in the system. The transmissions of the messages from the sources are formatted in frames during which the CSI of the links are assumed to be constant (slow fading hypothesis). The rate allocation is assumed not to change for several hundred frames, it changes only with the changes of CDI. The method distinguishes three phases, an initial phase and, for each frame to be transmitted, a 1st phase and a 2nd phase. The transmission of a frame takes place in two phases which are possibly preceded by an additional phase called initial.During the initialization phase, the destination determines an initial flow rate ^^. ^^ for each source ^^ ^^taking into account the average quality (e.g. SNR) of each of the links in the system. The destination estimates the quality (e.g. SNR) of the direct links: source to destination and relay to destination using known techniques based on the use of reference signals. The quality of the source-source, relay-relay and source-relay links is estimated by the sources and relays using, for example, the reference signals. The sources and relays transmit the average qualities of the links to the destination. This transmission occurs before the initialization phase. Since only the average value of the quality of a link is taken into account, its refresh occurs on a long time scale, i.e. over a time that allows the rapid variations (fast fading) of the channel to be averaged.This time is of the order of the time required to travel several tens of wavelengths of the transmitted signal frequency for a given speed of a node in the system. The initialization phase occurs, for example, every 200 to 1000 frames. The destination sends the initial rates it has determined back to the sources via a return path. The initial rates remain constant between two occurrences of the initialization phase. During the first phase, the M sources successively transmit their message during the M time slots using modulation and coding schemes determined from the initial rates. During this phase, the number ^^1 of channel uses (channel use, i.e. resource element according to 3GPP terminology) is fixed and identical for each of the sources.During the first phase, independent sources broadcast their coded information sequences in the form of messages to a single recipient. Each source broadcasts its messages at its initial rate. The destination communicates its initial rate to each source via very limited rate control channels. Thus, during the first phase, the sources each transmit their respective message in turn during time slots, each dedicated to a source. Sources other than the one transmitting and possibly relays, of the "Half Duplex" type, receive the successive messages from the sources and decode them. During the second phase, the destination selects for the current slot ^^ a single node taken from among the sources and relays to cooperate.This node randomly selects the source it helps from among the one it has correctly decoded and the destination has not yet correctly decoded by transmitting a redundancy of the message from this source. This phase lasts at most ^^. ^^ ^^ ^^time slots. During this phase, the number ^^2 of channel uses is fixed and identical for each of the selected nodes (sources and relays). This article teaches control signals which consist, for the destination to broadcast M bits which indicate its set of correctly decoded sources at the interval ^^ − 1, for the nodes which have correctly decoded a source that the destination has not yet correctly decoded to transmit a signal on a dedicated unicast channel and for the others to remain silent and finally for the destination to broadcast the result of its selection according to the chosen selection strategy.The protocol followed by the exchanges limits the overhead linked to signaling while allowing a maximization of the average spectral efficiency (utility metric) within the system considered under the constraint of respecting an individual quality of service (QoS) per source, but it does not allow to predict with certainty which sources can be correctly decoded by the destination. Main characteristics of the invention The subject of the present invention is a communication method with transmission of a frame carrying at least one message intended for a telecommunication system comprising ^^ nodes including ^^ sources. ^^ ^^ ^^ { 1, … , ^^ } and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination, the nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase, the message from a source having been coded before transmission using an incremental redundancy type coding which generates several redundancies, the 1 ère phase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 nde phase includes at least one retransmission interval for a transmission of nodes having correct knowledge of the same source such that these nodes simultaneously transmit during the same retransmission interval the same redundancy of the same message from the same source not yet correctly decoded by the destination, the transmission channel encompassing the transmission channels between the nodes and the destination called direct and the transmission channels between the nodes called indirect, with initialization of a remaining time during the 2 ndephase to ^^ ^^ ^^ ^^ , the process implemented by the destination is such that it includes, after the 1 ère phase: - determination of the number of retransmission intervals necessary and sufficient for the destination to decode sources ^^ not yet correctly decoded based on knowledge of flow rates ^^ ^^allocated to these sources and knowledge of a quality of the different direct transmission channels and the different indirect transmission channels, - determination of a set of sources not yet correctly decoded respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals of the sources of the set is less than or equal to the remaining time, called sources to be helped, - broadcasting to the nodes in a certain form of the sources of the set and the necessary and sufficient numbers of retransmission intervals of these sources, - reception, for each source of the set, of the same redundancy of this same source coming from the nodes having correct knowledge of this same source during the necessary and sufficient number of retransmission intervals of this same source. A redundancy emitted by a source can be received by the destination after having followed a direct channel between this source and the destination.The same redundancy can be received later by the destination after having followed an indirect channel, i.e. having been received by one of the nodes, decoded correctly by this node and then transmitted by this node during the 2. e transmission phase. Depending on the protocol followed by the exchanges, the destination requires only once, at the end of the first phase or at the beginning of the second phase, information on the quality of the indirect channels. Knowing the quality of the direct channels, transmitting the quality of the indirect channels from the nodes to the destination allows it to determine exactly, per source, a number of retransmission intervals necessary and sufficient for the destination to correctly decode this source. Knowing these numbers of necessary and sufficient intervals for all sources, the destination determines the set of sources whose sum of the numbers of necessary and sufficient intervals is less than or equal to time T maxand which, according to a particular embodiment, makes it possible to achieve maximum spectral efficiency. The nodes successively assist each of the sources of the set for the duration corresponding exactly to the number of necessary and sufficient intervals of each of these sources. The same source is assisted by the nodes having correct knowledge of this same source. The method is stopped when all the sources of the set have been assisted by the nodes. Taking into account the determination of the necessary and sufficient numbers of intervals, the method guarantees that these sources are correctly decoded by the destination at the end of the retransmissions. The invention has the advantage of limiting control exchanges while making the best use of the available time of the 2 ndephase to decode a maximum of sources which, according to the particular embodiment, provide maximum spectral efficiency. The invention further makes it possible to avoid wasting a single retransmission if no source can be helped in the remaining time. The present invention further relates to a communication method with transmission of a frame carrying at least one message implemented by a telecommunications device intended for a telecommunications system comprising ^^ nodes including ^^ sources ^^ ^^ ^^ ^^ { 1, … , ^^ } and ^^ − ^^, relay, ^^ ≥ ^^ ≥ 2, and a destination, the device forming one of the sources, the nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the N nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 ndephase, the message from a source having been coded before transmission using an incremental redundancy type coding which generates several redundancies, the 1 ère phase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 nde phase comprises at least one retransmission interval for a transmission of nodes having correct knowledge of the same source such that these nodes simultaneously transmit during the same retransmission interval the same redundancy of the same message from the same source not yet correctly decoded by the destination, the transmission channel encompassing the transmission channels between the nodes and the destination called direct and the channels between the nodes called indirect, the method is such that it comprises: - transmission of a first redundancy of a message from the device during the 1 èrephase, - reception in a certain form of the sources of a set of sources not yet correctly decoded respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals is less than or equal to ^^ ^^ ^^ ^^ and necessary and sufficient numbers of retransmission intervals of the game sources, - transmission of a second redundancy of one of the game sources if the device has correct knowledge of this source, during a retransmission interval of the 2 nde phase, and this a number of times corresponding to the necessary and sufficient number of retransmission intervals of this source. The present invention further relates to a telecommunications device for transmitting a frame carrying at least one message, intended for a telecommunications system comprising ^^ nodes including ^^ sources ^^ ^^ ^^ ^^ { 1, … , ^^ }and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination, the nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase, the message from a source having been coded before transmission using an incremental redundancy type coding which generates several redundancies, the 1 ère phase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 ndephase comprises at least one retransmission interval for a transmission of nodes having correct knowledge of the same source such that these nodes simultaneously transmit during the same retransmission interval the same redundancy of the same message from the same source not yet correctly decoded by the destination, the transmission channel encompassing the transmission channels between the nodes and the destination called direct and the channels between the nodes called indirect, the device which corresponds to one of the sources comprises at least one microprocessor, a memory, a transmitter and a receiver, the transmitter comprises an encoder implementing an incremental redundancy type coding which generates several redundancies of the same message to be transmitted, the device is such that: - the transmitter is able to transmit a first redundancy of a message from the device during the 1 èrephase, - the receiver is able to receive, in a certain form, sources from a set of sources not yet correctly decoded respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals is less than or equal to ^^ ^^ ^^ ^^ and the necessary and sufficient numbers of retransmission intervals of the game sources, - the transmitter is furthermore able to transmit a second redundancy of one of the game sources if the device has correct knowledge of this source, during a retransmission interval of the 2 nde phase, and this a number of times corresponding to the necessary and sufficient number of retransmission intervals of this source. The invention further relates to a telecommunications device intended for a telecommunications system comprising ^^ nodes of which ^^ sources ^^ ^^ ^^ ^^ { 1, … , ^^ }to transmit a frame carrying at least one message, and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination, the nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase, the message from a source having been coded before transmission using an incremental redundancy type coding which generates several redundancies, the 1 ère phase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 ndephase comprises at least one retransmission interval for a transmission of nodes having correct knowledge of the same source such that these nodes simultaneously transmit during the same retransmission interval the same redundancy of the same message from the same source not yet correctly decoded by the destination, the transmission channel encompassing the transmission channels between the nodes and the destination called direct and the channels between the nodes called indirect, the device which corresponds to the destination comprises at least one microprocessor, a memory, a transmitter and a receiver, the receiver comprises a decoder implementing an incremental redundancy type decoding to decode the same message from the received redundancies,the device is such that: - the microprocessor is able to determine the number of retransmission intervals necessary and sufficient for the destination to decode sources not yet correctly decoded based on knowledge of flow rates, ^^allocated to these sources and knowledge of a quality of the different direct transmission channels and of the different indirect transmission channels, to determine a set of sources not yet correctly decoded respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals of the sources of the set is less than or equal to the remaining time, called sources to be helped, - the transmitter is able to broadcast to the nodes in a certain form of the sources of the set and the necessary and sufficient numbers of retransmission intervals of these sources, - the receiver is able to receive, for each source of the set, the same redundancy of this same source coming from the nodes having correct knowledge of this same source during the necessary and sufficient number of retransmission intervals of this same source.According to one embodiment, the form of the broadcast corresponds to the sending in an ordered form of the set and the necessary and sufficient numbers of retransmission intervals of the sources of the set. According to this mode, the determined set is ordered and communicated to the nodes by the destination with, according to the same order, the necessary and sufficient numbers of intervals for the sources of the set. According to one embodiment, the form of the broadcast corresponds to the successive sending of identifiers of the sources of the set and this, during respectively the necessary and sufficient numbers of retransmission intervals of the sources of the set. According to this mode, the destination broadcasts the identifier of the source to be helped at each retransmission interval. The destination thus broadcasts the same identifier a number of times determined by the necessary and sufficient number of retransmission intervals of this source.According to one embodiment, the sources of the set are indexed and ordered according to their index number. According to one embodiment, the sources of the set are ordered according to the number of retransmission intervals necessary and sufficient to decode them correctly. According to this mode, the determined numbers of retransmission intervals necessary and sufficient are classified according to their value between the sources of the set. And, preferably, the ordering goes from the smallest to the largest number of retransmission intervals necessary and sufficient. According to one embodiment, the method further comprises: - following the transmission of an acknowledgment of receipt by the destination, successive receptions of the ^^ sources, reception by the destination of indicators of the quality of the indirect channels transmitted by the nodes.In this mode, the sending of indirect channel quality indicators is triggered by the sending of the acknowledgment of receipt by the destination of the reception of the transmissions occurring during the 1. ère phase. According to one embodiment, the method further comprises, - evaluation of quality indicators of the direct channels from the successive receptions of the ^^ sources. According to one embodiment, as soon as the set is empty then the transmission of the frame is interrupted. According to one embodiment, the determined set of sources leads to maximum spectral efficiency. According to one embodiment, when determining a set of sources not yet correctly decoded leading to maximum spectral efficiency, among all the sets of sources not yet correctly decoded satisfying the condition of a sum of the necessary and sufficient numbers of retransmission intervals less than or equal to ^^ ^^ ^^ ^^, the method discards any game including a source ^^ and not including a source ^^ when ≤ ^^ ^^ and ^^ ^^ > ^^ ^^ , ^^ ^^ { 1, … , ^^ } . According to one embodiment, when determining a set of sources not yet correctly decoded leading to maximum spectral efficiency, among all the sets of sources not yet correctly decoded satisfying the condition of a sum of the necessary and sufficient numbers of retransmission intervals less than or equal to ^^ ^^ ^^ ^^ , the method discards any game including a source ^^ and not including a source ^^ when ^^ ^^ < ^^ ^^ and ^^ ^^ = ^^ ^^, ^^ ^^{1, … , ^^}. According to one embodiment, the method further comprises, following receipt of an acknowledgment by the destination of the first redundancy of the message from the device, transmission by the device of indicators of the quality of indirect channels between this device and other nodes. According to one embodiment, the device is such that the receiver is further capable of receiving an acknowledgment by the destination of the first redundancy of the message from the device, and such that the transmitter is further capable of transmitting, following receipt of the acknowledgment, indicators of the quality of indirect channels between this device and other nodes.The invention further relates to each of the specific software applications on one or more information media, said applications comprising program instructions adapted to the implementation of the communication method when these applications are executed by microprocessors. The invention further relates to configured memories comprising instruction codes corresponding respectively to each of the specific applications. The memory(s) may be incorporated into any entity or device capable of storing the program. The memory(s) may be of the ROM type, for example a CD ROM or a microelectronic circuit ROM, or of the magnetic type, for example a USB key or a hard disk. Furthermore, each specific application according to the invention may be downloaded from a server accessible on an Internet-type network.The features of embodiments of the invention may optionally be combined with each other to define a new embodiment. The features of embodiments presented above in the context of the communication method may optionally be applied to the software application and memory mentioned above as well as to the devices and system according to the invention.List of figures Other characteristics and advantages of the invention will appear more clearly on reading the following description of embodiments, given as simple illustrative and non-limiting examples, and the appended drawings, among which: [Fig 1] figure 1 is a diagram of an example of a system called OMAMRC (Orthogonal Multiple Access Multiple Relays Channel) described with regard to the prior art, [Fig 2] figure 2 is a diagram of a transmission cycle of a frame according to an example of implementation of the invention, [Fig 3] figure 3 is a diagram of the exchanges between the destination and the nodes, sources and relays, according to an embodiment of the invention. [Fig 4] figure 4 is a diagram of an embodiment of a base station according to the invention, [Fig 5] figure 5 is a diagram of an embodiment of a terminal according to the invention.Description of particular embodiments A channel use is the smallest granularity in time-frequency resource defined by the system which allows the transmission of a modulated symbol. The number of channel uses is linked to the available frequency band and to the transmission duration. An OMAMRC telecommunication system is illustrated by the already described figure 1. An OMAMRC type telecommunication system according to the invention comprises ^^ sources which belong to the set of sources ^^ = { ^^1, … ,. ^^ = ^^ − ^^ relays that belong to the relay set ^^ = { ^^1, … , ^^ ^^ } , ^^ ≥ ^^ ≥ 2, and a destination ^^. By convention, it is considered that ^^ ^^ = ^^ ∀ ^^ ∈ {1, … , ^^} and ^^ ^^= ^^ + ^^ ∀ ^^ ∈ {1, … , ^^}, in other words, we can confuse a source and its index, and a relay and its index (shifted by the value M of the number of sources). Each source in the game ^^ communicates with the unique destination with the help of other sources (user cooperation) and cooperating relays. The nodes, sources plus relays, are therefore indexed by Transmission cycle of a frame according to the invention A transmission cycle of a frame according to an exemplary implementation of the invention is illustrated by figure 2. The method according to the invention distinguishes two phases for each frame to be transmitted, one 1 ère phase and a 2 nde phase. The transmission of a frame is possibly preceded by an additional phase called initial during which the bit rates are allocated ^^ ^^ , ^^ ∀ ^^ ∈ { 1, … , ^^ } . The ^^ sources access the transmission channel according to a time orthogonal multiple access scheme during the 1ère phase. During the 2 ndephase, access to the transmission channel of the ^^ nodes which include the ^^ sources and possibly the ^^ relays is considered orthogonal because at each retransmission interval the active nodes transmit in parallel the same redundancy of the same message from the same source ^^. The ^^ nodes operate in a half-duplex mode which allows them to listen without interference to the transmissions of other nodes. The sources can behave as a relay when they do not only transmit their own message. The CSI of the links are assumed to be constant (slow fading assumption) during the transmission of a frame. From time to time, the destination allocates rates to the sources knowing the distribution of all direct and indirect channels (CDI: Channel Distribution Information). The rate allocation is assumed not to change for several hundred frames, it only changes with CDI changes.Each of the allocated bit rates unambiguously determines a modulation and coding scheme (MCS) and conversely each MCS determines a bit rate. The allocated bit rates are transmitted from the destination to the sources via very limited bit rate control channels (shown in dotted lines in Figure 1).To simplify the description, the following assumptions are made subsequently about the telecommunication system: - the sources, the relays and the destination are equipped with a single transmit antenna (or transmit antenna port); - the sources, the relays and the destination are equipped with a single receive antenna (or receive antenna port); - the sources, the relays and the destination are perfectly synchronized; - the sources are statistically independent (there is no correlation between them); - all the nodes transmit with the same power; - use is made of a CRC code assumed to be included in the ^^. ^^information bits from each source ^^ to determine whether the message associated with the information bits is correctly decoded or not, ^^ ∈ ^^ ; - the links between the different nodes suffer from additive noise and fading. The fading gains are fixed during the transmission of a frame carried out for a maximum duration of ^^ + ^^ ^^ ^^ ^^ time intervals, but can change independently from frame to frame. ^^ ^^ ^^ ^^ ≥ 1 is a system parameter; - the instantaneous quality of a direct channel / link in reception (CSIR Channel State Information at Receiver) is available at the destination, the destination estimates in a known manner the direct channels and therefore their quality by exploiting for example the reference signal(s) received during the 1 ère phase; - returns are error-free (no errors on control signals / channels). The following notations are used: • ^^ ^^ = ^^ ^^⁄ ^^1is a discrete variable representing the source rate ^^ provided by a link adaptation method implemented before the transmission of a frame or frames, • ^^^^ ^^ ^^ ^^is the number of retransmission intervals used during the 2 nde phase, ^^^^ ^^ ^^ ^^∈ {0, …, ^^ ^^ ^^ ^^}, it corresponds to the number of transmissions during this phase, • ^^ = ^^2⁄ ^^1is the ratio between the number of channel uses available at each time interval (slots) of the 2 nde phase and the number of channel uses available at each time interval (slots) of the 1 ère phase, • ^^ ^̅^,0 is the set of sources not correctly decoded by the destination at the end of the 1 ère phase, • ^^ ^^ ^^ is the set of sources correctly decoded by the node ^^ ∈ ^^ ∪ ℜ at the end of the retransmission interval ^^, ^^ ∈ { 1, … , ^^^^ ^^ ^^ ^^ } , • O ^^, ^^is the default indicator (outage) after the retransmissions helping the source ^^ which takes the value one when an individual fault event occurs and the value zero in other cases. O ^^, ^^ ^^ represents the source fault event ^^ i.e. the source is not decoded correctly after ^^ ^^ retransmissions helping this source, • ^^ ^^, ^^ represents the mutual information between the source ^^ ∈ {1, … , ^^} and the destination ^^, • is defined as the quality information of the equivalent channel between the nodes having decoded the same source ^^ and the destination, based on the knowledge of the fading of the direct channels and the indirect channels, for the ^^ ^^è ^^ ^^retransmission helping the source ^^, i.e., knowing the nodes having decoded the source ^^ after ^^ − 1 retransmissions helping it. An equivalent channel for the source ^^ is the result of a superposition (linear addition or combination) of the coefficients of the links of the nodes having decoded the source ^^ to the destination. This is due to the fact that the nodes ^^ ∈ ^^ emit the same signal ^^ ^^ up to a multiplicative coefficient ^^ ^^ where A is the subset of nodes that decoded the source ^^ and RV is the signal corresponding to an incremental redundancy of the message from the source ^^. Thus, at reception it follows that the channel can be written Multiplicative coefficients ^^ ^^ can be, for example, equal to ^^ ^^ = ^^, if each node ^^ ∈ ^^ has knowledge of the channel ℎ ^^, ^^ on the broadcast. The equivalent channel becomes This technique is known as "Equal Gain Combining" and allows for coherent addition of link fading. Transmission of a frame according to the invention Figure 3 schematically illustrates the exchanges between all the nodes and the destination ^^ according to an embodiment of the invention. The sources ^^ ∈ { 1, .. , ^^ } intervene during the 1 ère phase, the sources and relays ^^ ∈ {1, … , ^^ + ^^} intervene during the 2 nde phase. During the first phase of the process, the sources ^^ ∈ ^^ successively transmit their message after coding ^^ ^^ comprising ^^ ^^ bits of information ^^ ^^ ∈ ^^ ^ 2 ^ ^^ , ^^2 being the two-element Galois field. The message ^^ ^^ includes a CRC type code which allows the integrity of the message to be verified ^^ ^^ . The message ^^ ^^is encoded according to the MCS determined by the allocated bitrate. Considering that the MCS can be different between sources, the lengths of the encoded messages ^^1, … , ^^ ^^may be different between sources. The coding uses an incremental redundancy type code. The resulting codeword is segmented into successive redundancies. The incremental redundancy code can be of a systematic type, the information bits are then included in the first redundancy. Whether or not the incremental redundancy code is of a systematic type, it is such that the first redundancy can be decoded independently of the other redundancies.The incremental redundancy type code can be implemented, for example, by means of a finite family of rate-compatible punctured linear codes or rate-free codes modified to operate with finite lengths: raptor code (RC), rate-compatible punctured turbo code (RCPTC rate-compatible punctured turbo code), rate-compatible punctured convolutional code (RCPCC rate-compatible punctured convolutional code), rate-compatible LDPC (RCLDPC rate-compatible low-density parity check code). Transmission by a source conventionally comprises one or more reference signals. The destination estimates in a known manner the direct channel and therefore its quality between each of the sources and the destination, for example by exploiting the received reference signal(s). Whether during the first phase or the second phase, when a node transmits, in particular a source, the destination and the other nodes listen.The destination, sources, and relays attempt to decode the received redundancies at the end of a time interval. The success of decoding at each node is decided using the CRC. The destination and nodes thus determine their set of successfully decoded sources at the end of each interval preceding the current interval ^^, ^^. ^^, ^^−1 ^^ ^^, ^^−1 , with the convention that ^^ = 0 corresponds to the last transmission interval of the first phase. The 2 nde transmission phase of the process includes ^^ = {1, … , ^^^^ ^^ ^^ ^^} retransmission intervals. The term retransmission associated with an interval is used in connection with the 2 nde phase to clearly indicate that any transmission during this phase of a n ième redundancy of the message from a source ^^ occurs when this source ^^ has already transmitted the 1 ère redundancy of this same message during the 1 èrephase. Unlike the prior art, there is no exchange of decoding control between the destination and the nodes at each retransmission interval: the destination does not systematically send back at each retransmission interval its set of correctly decoded sources nor any indication of correct decoding or not, the nodes do not systematically transmit at each retransmission interval their set of correctly decoded sources nor any indication of their correct decoding or not. The destination acknowledges receipt ACK / NACK of the successive transmissions of the ^^ sources occurring during the 1 ère phase. According to an optimal embodiment in terms of control channel occupancy, the acknowledgment is coded on one bit. In response, and in case of ACK, the frame ends with ^^^^ ^^ ^^ ^^= 0, the sources move on to another message to be transmitted. In response, and in case of NACK, the nodes transmit to the destination quality information ^^ ^^ ^^^^ on all indirect channels: channels between sources, channels between sources and relays and channels between relays. The transmission by nodes ^^ ∈ {1, … , ^^ + ^^} of quality information ^^ ^^ ^^ ^^ on indirect channels for a determination by the destination of the sets of sources which can be helped in the time of the 2 nde phase, ie in the maximum time ^^ ^^ ^^ ^^, occurs only when ^^ = 0, i.e. at the end of the first phase or at the beginning of the second phase. The destination also knows the quality of all direct links. For direct channels between sources and destination, the estimation of the channel between source ^^ and destination is performed, for example, on the basis of the reference signals emitted by source ^^ when it transmits during the first phase. Since the channels are assumed to be invariant during a frame, this value is independent of the transmission or retransmission interval. This knowledge of the quality of the channel between source ^^ and destination allows the destination to estimate mutual information ^^ ^^, ^^representative of this quality and therefore of the channel capacity. During the second phase, the estimation of the direct channel between the relay ^^ ∈ { ^^ + 1, … , ^^ + ^^} and the destination is carried out, for example, on the basis of a reference signal emitted by the relay ^^ during the control exchange during which it transmits quality information of an indirect channel. The estimation can be limited to the relay nodes ^^ ∈ { ^^ + 1, … , ^^ + ^^} since the quality of the direct channels between the sources and the destination could be estimated during the 1 ère phase. This knowledge of the quality of all direct and indirect links allows the destination to estimate mutual information ^^ ^̅^, ^^ ( ^^) representative of the quality of the equivalent channel between all the nodes having decoded the source ^^ and the destination for the ^^ è ^^ ^^ re-transmission helping this source. The individual fault event of the source ^^ after ^^ ^^ broadcasts ^^ ^^, ^^ ^^, can be expressed in the following form: where ^^ ^̅^, ^^ ( ^^) is defined as the equivalent channel quality information between nodes that have decoded the same source ^^ and the destination, based on knowledge of the fading of the direct and indirect channels, for the ^^ ^^è ^^ ^^ retransmission helping the source ^^, i.e., knowing the nodes having decoded the source i after ^^ − 1 retransmissions helping it. Knowing the quality of all the links in the system and the flow rates attributed to the sources ^^ ^^ , the destination determines the number of retransmission intervals necessary and sufficient ^^ ^^ so that it can decode the sources ^^ ∈ ^^ ^̅^,0 that she has not yet correctly decoded: ^^ ^^ = ar ^^ tel ∶ Expression (1) reflects the fact that the source ^^ is decoded correctly after ^^ ^^ retransmissions if the flow ^^ ^^of the source is less than or equal to the sum of the transmission capacities. This sum of the transmission capacities includes the capacity of the direct channel ^^ ^^, ^^ between this source ^^ and the destination which occurs during the 1 ère phase and a weighted sum by ^^ of the capacities of the equivalent channels ^^ ^̅^, ^^ which occur during the second phase between the active nodes and the destination during ^^ ^^ retransmission intervals. The active nodes are those that have correctly decoded this source ^^ and that transmit the same redundancy of this same source ^^ for the retransmission ^^ to help the destination to decode it. The equivalent channel considered for the retransmission ^^ groups the channels between each of the nodes helping the source ^^ during this interval and the destination. The capacity of the channel between the source ^^ and the destination is deduced from the quality of the channel ie the mutual information ^^ ^^, ^^between the source ^^ ∈ {1, … , ^^} and the destination ^^. The capacity of the equivalent channel considered when the source ^^ is assisted for retransmission ^^ is evaluated by the mutual information ^^ ^̅^, ^^ (^^) between the set of nodes that help the source ^^ for the retransmission ^^ and the destination. This capacity depends on the number of retransmissions ^^ since a node can benefit from the transmissions to help a source ^^ during the 2 nde phase and correctly decode this source ^^ from a retransmission interval of the 2 nde phase when he had not decoded it at the end of the 1 ère phase. By retaining the smallest value of ^^ ^^ which allows inequality (1) to be respected, the process thus obtains the number ^^ ^^ of necessary and sufficient retransmission intervals during the 2 ndephase for the destination to be able to decode a source. Knowing the number of retransmission intervals necessary and sufficient for the destination to be able to decode all the sources not yet correctly decoded, the destination determines the possible subsets ^^ of sources taken from all the subsets of sources not yet correctly decoded by the destination at the end of the 1 ère phase, ^^( ^^ ^̅^,0 ), which can be decoded in time ^^ ^^ ^^ ^^ of the 2 nde phase. Among these subsets ^^, the destination selects, according to a particular embodiment, the set of sources ^^̂ which maximizes the spectral efficiency ^^^^ ^^ ^^ ^^ ^^: ^^̂ = argmax { ^^^^ ^^ ^^ ^^ ^^∑ =^^∈ ^^∪ ^^ ^^,0^^ ^^ ^^+ ^^ ∑ ^^∈ ^^ ^^ ^} (2) ^^∈ ^^( ^̅^ ^^,0 ) ^ such that ∑ ^^∈ ^^ ^^ ^^ ≤ ^^ ^^ ^^ ^^Maximizing spectral efficiency can be expressed as determining the subset ^^̂ taken from the set ^^( ^^ ^̅^,0 ) possible ^^ subsets of sources not yet correctly decoded by the destination at the end of the 1st phase leading to the largest ^^ sum of the source rates, ^^ ^^ ^^ . Regardless of the mode, the sources of this subset ^^̂ must be able to be decoded in the remaining time, ^^ ^^ ^^ ^^ ie such that the time of the 2 nde phase is greater than or equal to the sum of the number of retransmission intervals sufficient to decode each of the sources in this subset ^^̂. The destination jointly orders the set ^^̂ and the set of numbers ^^ of necessary and sufficient retransmission intervals of each source of the set ^^̂, that is to say that the sources of the set ^^̂ and the number ^^ ^^follow the same order. According to one embodiment, the sources are ordered according to the increasing or decreasing index value and the numbers ^^ ^^ are ordered according to this increasing or decreasing index value of the sources. According to another mode, the order follows the value of the numbers ^^ ^^ , for example from smallest to largest. According to a first embodiment, the destination broadcasts the set ^^̂ and the set of numbers ^^ ^^ jointly ordered to decode each source ^^ with ^^ ∈ ^^̂. The nodes receive the set ^^̂ and the set of number ^^ ^^ and their successive reading of the sources is done jointly with their successive reading of the numbers ^^ ^^ . At each retransmission interval, a node selects a source ^^̂ ^^ said source to help taken in the game ^^̂ and this as many times as the value of the number ^^ ^^associated with this source. Nodes having correct knowledge of this source, i.e. the source itself and nodes having correctly decoded this source (each node evaluates its set of decoded sources at the beginning of each retransmission interval), transmit the same redundancy ^^ ^^̂ ^^ of the same message from this same source during this interval using a data channel. In other words, for a source ^^ of ^^̂, all nodes having correct knowledge of this source transmit during the ^^ ^^consecutive retransmission intervals dedicated to helping this source. This step is repeated until reaching the last retransmission interval dedicated to helping the last source of ^^̂. At the end of the last interval, the transmission of the frame is finished, the process is repeated for a following frame. According to a second embodiment, the destination broadcasts to the nodes, at each retransmission interval, the same source ^^ to be helped as many times as the number of necessary and sufficient intervals determined for this source. This mode makes it possible to make the protocol followed by the exchanges more robust. Helping a source means helping the destination to decode this source by transmitting by the nodes having correct knowledge of this source the same redundancy of the message of this same source during the 2 ndephase. Nodes with correct knowledge of this source ^^ transmit the same redundancy during the current interval ^^ to help the destination decode the source ^^. The destination updates the set ^^̂ each time a source is correctly decoded. Whatever the mode, all the sources ^^ of the subset ^^̂ are thus considered successively. The method stops the transmission of a frame when the set ^^̂ is empty or when all the sources are correctly decoded or when no source can be correctly decoded in the remaining time. According to one embodiment, the method takes into account additional constraints when maximizing spectral efficiency. Thus, the method limits the possible subsets ^^ of sources by considering that some sources are better than others and by first retaining these best sources.A ^^ source is better than a ^^ source in two cases: 1st case) the flow rate of the ^^ source is higher than that of the ^^, ^^ source. ^^ > ^^ ^^ , while benefiting from a sufficient and necessary number of intervals smaller or equal, ≤ ^^ ^^ , 2nd case) the source ^^ benefits from a sufficient and necessary number of intervals smaller than or equal to that of the source ^^, ^^ ^^ < ^^ ^^ , and the two sources ^^ and ^^ have the same flow rate = ^^ ^^ . So, for two sources ^^ and ^^ such that ^^ ^^ ≤ ^^ ^^ and ^^ ^^ > ^^ ^^ , the process then discards any source set containing source ^^ but not source ^^. And for two sources ^^ and ^^ such that ^^ ^^ = ^^ ^^ and ^^ ^^ < ^^ ^^, the method then discards any set of sources containing the source ^^ but not the source ^^. Figure 4 is a diagram of the simplified structure of an embodiment of a device, a base station BS, according to an embodiment of the invention. This BS device is intended for an OMAMRC type telecommunications system comprising ^^ nodes including ^^ sources ^^ ^^ ^^ ^^ { 1, … , ^^ } and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ^^, i.e. the base station BS. The nodes operate in half-duplex mode, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase. The message from a source is encoded before transmission using an incremental redundancy type coding which generates several redundancies. The 1 èrephase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 nde phase includes at least one retransmission interval for a transmission from nodes having correctly decoded the same source ^^ ^^such that these nodes simultaneously transmit during the same retransmission interval the same redundancy of the message from the same source not yet correctly decoded by the destination. The transmission channel includes the transmission channels between the nodes and the destination called direct and the channels between the nodes called indirect before reaching the destination. The device BS comprises at least one microprocessor µP_BS whose operation is controlled by the execution of a program whose instructions allow the implementation of a communication method according to the invention, a memory MEM_BS, a transmitter EM_BS and a receiver RE_BS which are connected to each other through a bus Bu. Of course, the constituent elements of the device BS can be connected by means of a connection other than a bus. The receiver RE_BS comprises a decoder DECOD IR for decoding the received messages which have been coded on transmission according to an incremental redundancy type coding.The decoder attempts to decode a message received from a source starting from 1. ère redundancy. In case of failure, the decoder jointly decodes this 1 èreredundancy with the successive redundancies received during the retransmission intervals reserved for this same source. The microprocessor µP_BS controls the operations of the device BS. The storage unit MEM_BS stores at least the program for implementing the method according to an embodiment of the invention to be executed by the processor µP_BS, and various data, such as parameters used for calculations performed by the microprocessor µP_BS, intermediate data of calculations performed by the microprocessor µP_BS, etc. The microprocessor µP_BS can be formed by any known and suitable hardware or software, or by a combination of hardware and software.For example, the microprocessor µP_BS may be formed by dedicated hardware such as a processing circuit, or by a programmable processing unit such as a central processing unit (CPU) that executes a program stored in a memory thereof. The memory MEM_BS may be formed by any suitable means capable of storing the program(s) and data in a computer-readable manner. Examples of memory MEM_BS include computer-readable non-transitory storage media such as semiconductor memory devices, and magnetic, optical, or magneto-optical recording media loaded into a read-write unit. At initialization, the program code instructions are, for example, loaded into a buffer memory before being executed by the processor µP_BS.The microprocessor µP_BS controls the various components of the BS device. Thus, by executing the instructions, the microprocessor µP_BS enables the BS device to implement the communication method according to one embodiment of the invention. This method comprises: - determining numbers ^^. ^^ of retransmission intervals necessary and sufficient for the destination BS to decode sources ^^ not yet correctly decoded based on a knowledge of flow rates ^^ ^^ attributed to these sources and a knowledge of a quality ^^ ^^ ^^ ^^of the different direct transmission channels and the different indirect transmission channels, implemented by the microprocessor µP_BS, - determination of a set ^^̂ of sources not yet correctly decoded leading to a spectral efficiency ^^^^ ^^ ^^ ^^ ^^maximum and respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals is less than or equal to ^^ ^^ ^^ ^^, implemented by the microprocessor µP_BS, - transmission to the nodes in an ordered form of the set ^^̂ and the necessary and sufficient numbers of retransmission intervals of the sources of the set, implemented by the transmitter EM_BS, - reception, for each source of the set, of the same redundancy of this same source coming from the nodes having correct knowledge of this same source during the necessary and sufficient number of retransmission intervals of this same source, implemented by the receiver RE_BS. Figure 5 is a diagram of the simplified structure of an embodiment of a TAL device, according to an embodiment of the invention. This TAL device is intended for an OMAMRC type telecommunication system comprising ^^ nodes including ^^ sources ^^ ^^ ^^ ^^ { 1, … , ^^ } and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ^^. The TAL device corresponds to one of the ^^ sources ^^ ^^^^ ^^{1, … , ^^}. The TAL device may be a mobile terminal. The TAL device is capable of implementing a communication method according to the invention and therefore of transmitting a framed message. Of course, the device may successively transmit several messages. The nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase. The message from a source is encoded before transmission using an incremental redundancy type coding which generates several redundancies. The 1 ère phase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 ndephase includes at least one retransmission interval for a transmission from nodes having correctly decoded the same source ^^ ^^such that these nodes simultaneously transmit during the same retransmission interval the same redundancy of the message from the same source not yet correctly decoded by the destination. The transmission channel includes the transmission channels between the nodes and the destination called direct and the channels between the nodes called indirect before reaching the destination. The TAL device comprises at least one microprocessor µP whose operation is controlled by the execution of a program whose instructions allow the implementation of a communication method according to the invention, a memory MEM, a transmitter EM and a receiver RE which are connected to each other through a bus Bu. Of course, the constituent elements of the TAL device can be connected by means of a connection other than a bus. The transmitter EM comprises a COD IR encoder for encoding the messages to be transmitted according to an incremental redundancy type coding.The microprocessor µP controls the operations of the TAL device. The storage unit MEM stores at least the program for implementing the method according to an embodiment of the invention to be executed by the microprocessor µP, and various data, such as parameters used for calculations performed by the microprocessor µP, intermediate data of calculations performed by the microprocessor µP, etc. The microprocessor µP may be formed by any known and suitable hardware or software, or by a combination of hardware and software. For example, the microprocessor µP may be formed by dedicated hardware such as a processing circuit, or by a programmable processing unit such as a central processing unit (Central Processing Unit in English) which executes a program stored in a memory thereof.The MEM memory may be formed by any suitable means capable of storing the program(s) and data in a computer-readable manner. Examples of MEM memory include computer-readable non-transitory storage media such as semiconductor memory devices, and magnetic, optical, or magneto-optical recording media loaded into a read-write unit. Upon initialization, the program code instructions are, for example, loaded into a buffer memory before being executed by the microprocessor μP. The microprocessor μP controls the various components of the TAL device. Thus, by executing the instructions, the microprocessor μP enables the TAL device to implement the communication method according to an embodiment of the invention.The communication method implemented by the TAL device is such that it comprises an incremental redundancy type coding implemented by the coder of the EM transmitter which generates several redundancies of the same message to be transmitted. The communication method implemented by the TAL device further comprises: - transmission of a first redundancy of a message during the 1. ère phase, implemented by the transmitter EM, - reception of a set ^^̂ of sources not yet correctly decoded leading to a spectral efficiency ^^^^ ^^ ^^ ^^ ^^maximum and respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals is less than or equal to ^^ ^^ ^^ ^^ and the necessary and sufficient numbers of retransmission intervals of the game sources, in the same ordered form, implemented by the receiver RE, - transmission of a second redundancy of one of the sources ^^ ^^of the game if the device has correct knowledge of this source, during a retransmission interval of the 2 nde phase, and this a number of times corresponding to the necessary and sufficient number of retransmission intervals of this source, implemented by the EM transmitter. Example of implementation The description of an embodiment of the invention which follows is illustrated with an implementation by a system with ^^ = 3 sources, ^^ = {1,2,3}, ^^ = 3 relays, ^^ = {4,5,6}, and a destination. The parameter ^^ ^^ ^^ ^^ is set to five and the ratio ^^ = 1. The flow rates ^^ ^^ of the sources have the following values: ^^1= 1, ^^2= ​​2, ^^3= 3. ^^̂ is the set of incorrectly decoded sources which leads to the highest spectral efficiency ^^^^ ^^ ^^ ^^ ^^ and which satisfies the condition on the sum of the numbers of retransmission intervals which must be less than or equal to the remaining time. During the 2 ndephase, the selection of the source ^^ to be helped from the set ^^̂ at each retransmission interval takes place according to the algorithm in Appendix B. At the beginning of the 2 nde phase (or equivalently at the end of the 1 ère phase), step 1, i.e., ^^ = 1, the sets of sources correctly decoded by the nodes are as follows: ^^ 1,0 = {1}, ^^ 2,0 = {2}, ^^ 3,0 = { 3 } , ^^ 4,0 = ^^, ^^ 5,0 = {2,3}, ^^ 6,0 = {1,2,3}, ^^ ^^,0 = ^^. In other words, sources 1, 2, 3 and relay 4 have not yet decoded anything correctly at the end of 1 ère phase but as a source knows its own message its game contains at least this message. Relay 5 correctly decoded sources 2 and 3 and relay 6 correctly decoded sources 1, 2 and 3 at the end of 1 ère phase. The destination ^^ has not yet decoded anything correctly and therefore ^^ ^̅^,0 = {1,2,3} ≠ ^^ at the end of 1ère phase. In step 2, the destination determines the set ^^̂. This determination is carried out according to the algorithm in Appendix A. This determination is based on an exchange of control with the reception of the ^^ ^^ ^^ ^^ which occurs at the end of the 1 ère phase or equivalently at the beginning of the 2 nde phase, step 1 of the algorithm in Appendix A. This reception follows, for example, an acknowledgment of receipt issued by the destination at the end of the 1 ère phase. Alternatively, the destination may explicitly require that nodes transmit information related to the quality of indirect channels. Indirect channels include channels between sources, channels between sources and relays, and channels between relays, or broadly, channels between nodes preceding a channel between one of these nodes and the destination for transmission to the destination. From the transmissions occurring during the 1ère phase, the destination determines quality information of the direct channels, i.e. between the sources and the destination. The destination therefore has knowledge of quality indicators of all channels, i.e. direct and indirect. Step 2 of the algorithm in Appendix A. Based on this knowledge, the destination determines for each source ^^ the number ^^ ^^ of retransmission intervals necessary and sufficient to correctly decode this source ^^, not yet decoded, on the basis of knowledge of mutual information of the direct source ^^ destination link, of mutual information of the equivalent channels and of a rate ^^ ^^ assigned to this source ^^. The destination therefore calculates ^^ ^^ for all ^^ ∈ ^^ ^̅^,0 . This number is the smallest number ^^ ^^ of retransmissions at the end of which there is no decoding error, i.e. the flow rate of the source is less than or equal to the sum of a part of the direct channel capacity ^^ ^^, ^^ and on the other hand of the sum weighted by ^^ equivalent channels for the ^^ retransmission intervals. According to the example, ^^1= 2, ^^2= ​​2 and ^^3= 3. Step 3 of the algorithm in Appendix A. At the end of the 1 ère phase or equivalently at the beginning of the 2 nde phase, the destination determines the set of sources ^^̂ to help among the set of sources ^^ ^̅^,0 that it has not yet correctly decoded. The destination determines the set ^^̂ knowing the numbers of time intervals ^^ ^^ at the end of which the sources are correctly decoded. The set ^^̂ includes the set of sources not yet correctly decoded which satisfies the condition of the number of remaining retransmission intervals, i.e., each source in the set ^^̂ can be decoded in the remaining time ^^ ^^ ^^ ^^(since ^^ = 1) and which, according to a particular embodiment, leads to the highest spectral efficiency ^^^^ ^^ ^^ ^^ ^^. According to the example, the possible choices for ^^̂ which satisfy ∑ ^^∈ ^^ ^^ ^^ ≤ ^^ ^^ ^^ ^^ are : { 1 } , { 2 } , { 3 } , { 1.2 } , { 1.3 } , { 2.3 } . Knowing that ^^2> ^^1 and that ^^1= ^^2 then the destination can deduce that source 2 is better than source 1. The destination eliminates the possibilities {1} and {1,3} since it is better to choose {2} and {2,3}. The possible choices for ^^̂ are therefore reduced to: { 2 } , { 3 } , { 1.2 } , { 2.3 } The criterion of spectral efficiency per frame gives: Like ^^ {2} < ^^ {1,2} < ^^ {3} < ^^ {2,3}then ^^̂ = {2,3} with ^^2= ​​2 and ^^3= 3. Step 4 of the algorithm in Appendix A. The destination broadcasts to the nodes the set ^^̂ of ordered sources with the numbers ^^ ^^ corresponding number of retransmission intervals for all sources in the set ^^̂. According to the example, the destination broadcasts ({2,3}, 2, 3). Once the set ^^̂ and the numbers of intervals are sufficient and necessary ^^ ^^transmitted to the nodes using the algorithm in Appendix A, the process resumes the flow of the Algorithm in Appendix B. Step 3 of the algorithm in Appendix B. As long as all the sources in the set ^^̂ are not decoded, i.e. ^^̂ ≠ ∅ the destination performs steps 4-12. Step 4 of the Algorithm in Appendix B. The nodes successively select the sources to be helped from the set ^^̂ in the order in which they appear in the set, one after the other. The current selected source is the source ^^. According to the example, the nodes select ^^ = 2 twice, then ^^ = 3 three times. Step 5. As long as ^^ ^^ > 0, the current selected ^^ source is helped by the nodes which have correct knowledge of this source, the nodes perform steps 6-11, ie, each ^^ source is helped ^^ ^^times. Step 6. The nodes transmit simultaneously, in parallel, the same redundancy from the selected source. According to the example, the nodes transmit a second redundancy from source 2 and the same at the next iteration. Then the nodes transmit a second redundancy from source 3 and the same at the next two iterations. Step 7. The process increments the value of the current retransmission interval, ^^ ← ^^ + 1, and decrements the number of sufficient and necessary intervals ^^ ^^ from the selected source, ^^ ^^ ← ^^ ^^ − 1, at each iteration. Steps 8-10. If the selected source is decoded correctly at the end of the current retransmission interval ^^, ie, ^^ ^^= 0, the source is removed from the set ^^̂ of sources to be helped in step 9, ^^̂ ← ^^̂ \ { ^^}. Otherwise the process goes to step 11 and then loops back to step 5 until the selected source is decoded correctly. If the source is decoded correctly, the process goes to step 12 and then loops back to step 3 if there are still sources in the set ^^̂ of sources to be helped. According to the example ^^̂ = { 2, 3 } and the flow of steps 3-12 can be as follows. Step 4. Source selection 2. 1 ère loop 5-11 Step 5. As ^^2= ​​2 > 0, i.e. source 2 is not decoded correctly, then go to step 6. Step 6. Nodes with correct knowledge of source 2 send the same second redundancy. Step 7. Increment the current interval, ^^ ← ^^ + 1 = 2. Decrement ^^2, ^^2= ​​2 − 1 = 1. Step 8. As ^^2≠ 0, the process runs steps 5-11 a second time. 2 eloop 5-11 Step 6. Nodes with correct knowledge of source 2 send the same third redundancy. Step 7. Increment the current interval, ^^ ← ^^ + 1 = 3. Decrement ^^2, ^^2= ​​1 − 1 = 0. At the end of step 7, source 2 is decoded correctly then ^^2= ​​0. Step 8. ^^2= ​​0 is true so at step 9 source 2 is removed from ^^̂, ^^̂ ← ^^̂ \ { 2 } = { 3 } . The process loops to step 3, then 4. Step 4. Source selection ^^ = 3. 3 e loop 5-11 Step 5. As ^^3= 3 > 0, i.e. source 3 is not decoded correctly, then go to step 6. Step 6. Nodes with correct knowledge of source 3 send the same second redundancy. Step 7. Increment the current interval, ^^ ← ^^ + 1 = 4. Decrement ^^3, ^^3= 3 − 1 = 2. Step 8. As ^^3≠ 0, the process runs steps 5-11 a second time. 4 eloop 5-11 Step 5. As ^^3= 2 > 0, i.e. source 3 is not decoded correctly, then go to step 6. Step 6. Nodes with correct knowledge of source 3 send the same third redundancy. Step 7. Increment the current interval, ^^ ← ^^ + 1 = 4. Decrement ^^3, ^^3= 2 − 1 = 1. Step 8. As ^^3≠ 0, the process runs steps 5-11 a third time. 5 eloop 5-11 Step 5. As ^^3= 1 > 0, i.e. source 3 is not decoded correctly, then go to step 6. Step 6. Nodes with correct knowledge of source 3 send the same fourth redundancy. Step 7. Increment the current interval, ^^ ← ^^ + 1 = 5. Decrement ^^3, ^^3= 1 − 1 = 0. Step 8. ^^3= 0 is true, then in step 9 source 3 is removed from ^^̂, ^^̂ ← ^^̂ \ {3} = ∅. Loop 3-12 is terminated, the process is terminated since ^^̂ = ∅, i.e., there is no more source to help. [1] S. Cerović, R. Visoz, and L. Madier. "Efficient Cooperative HARQ for Multi-Source Multi-Relay Wireless Networks." 201811th International Workshop on Selected Topics in Wireless and Mobile Computing. IEEE, 2018. Appendix A Determining the set of sources that can be helped: if not all sources are decoded at the end of the transmission phase, the destination sends a NACK and ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ [Table 1] Appendix B Selection Strategy Algorithm: [Table 2] 1. ^^ ← 1 ; Start of the 1st transmission phase i.e. ^^ is initialized to 1, 2. ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ Calculation of the set ^^̂ at the beginning of the 2 nde phase according to Annex A ie using a control exchange with the reception of ^^ ^^ ^^ ^^ and communication at the nodes of ^^̂ and ^^ ^^ 3 . As long as ( ^^̂ ^^) do While ^^̂ contains a source do steps 4-12 i.e. frame decoding is stopped when ^^̂ is the empty set Successive selections of the Nodes successively select the sources of ^^̂ by the nodes, sources to help in the ordered set ^^̂. The ^^ ← 1st ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^̂ source ^^ is assumed to be the 1 ère source of the ordered game ^^̂ As long as ( ^^ ^^ > 0) do The source i is helped ^^ ^^ times ^^ ^^̂ ^^Nodes that have correctly decoded the source ^^ transmit the same redundancy in parallel ^^ ← ^^ + 1, ^^ ^^ ← ^^ ^^ − 1 Increment of the current round ^^ and decrement of the number of intervals ^^ ^^ 8. if ( ^^ ^^ = 0) then if ^^ was helped ^^ ^^ times at the end of the round ^^ so 9 . ^^ is deleted from ^^̂ 10. End of if 11. End of while 12. End of while

Claims

CLAIMS 1. Communication method with transmission of a frame carrying at least one message intended for a telecommunications system comprising ^^ nodes including ^^ sources ^^ ^^ ^^ ^^ { 1, … , ^^ } and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ( ^^), the nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase, the message from a source having been coded before transmission using an incremental redundancy type coding which generates several redundancies, the 1 ère phase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 ndephase includes at least one retransmission interval for a transmission from nodes having correct knowledge of the same source ( ^^ ^^ ) such that these nodes transmit simultaneously during the same retransmission interval the same redundancy of the same message from the same source not yet correctly decoded by the destination, the transmission channel encompassing the transmission channels between the nodes and the destination called direct and the transmission channels between the nodes called indirect, with initialization of a remaining time during the 2 nde phase to ^^ ^^ ^^ ^^ , the process implemented by the destination is such that it includes, after the 1 ère phase: - determination of numbers ( ^^ ^^ ) of retransmission intervals necessary and sufficient for the destination to decode sources ^^ not yet correctly decoded based on knowledge of flow rates attributed to these sources and a knowledge of a quality ( ^^ ^^ ^^ ^^ ) of the different direct transmission channels and of the different indirect transmission channels, - determination of a set ( ^^̂) of sources not yet correctly decoded respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals of the sources ( ^^ ^^ )of the game ( ^^̂) is less than or equal to the remaining time, said sources to be helped, - broadcasting to the nodes in a certain form of the sources of the game ( ^^̂) and the necessary and sufficient numbers of retransmission intervals of these sources, - receiving, for each source of the game, the same redundancy of this same source coming from the nodes having correct knowledge of this same source during the necessary and sufficient number of retransmission intervals of this same source.

2. Method according to claim 1, such that the form of the broadcast corresponds to the sending in an ordered form of the game ( ^^̂) and the necessary and sufficient numbers of retransmission intervals of the sources of the game.

3. Method according to claim 1, such that the form of the broadcast corresponds to the successive sending of identifiers of the sources of the game (^^̂) and this, during respectively the necessary and sufficient numbers of retransmission intervals of the sources of the game.

4. Method according to one of claims 1 to 3, such that the sources of the game (^^̂) are indexed and ordered according to their index number.

5. Method according to one of claims 1 to 3, such that the sources of the game (^^̂) are ordered according to the numbers of retransmission intervals necessary and sufficient to decode them correctly.

6. Method according to one of claims 1 to 5, further comprising: - following the transmission of an acknowledgment of receipt by the destination, successive receptions of the ^^ sources, reception by the destination of indicators of the quality (^^ ^^ ^^ ^^) indirect channels transmitted by the nodes.

7. Method according to one of claims 1 to 6, further comprising, - evaluation of quality indicators ( ^^ ^^ ^^ ^^ ) direct channels from successive receptions of the ^^ sources.

8. Method according to one of claims 1 to 7, such that, as soon as the set ( ^^̂) is empty then the transmission of the frame is interrupted.

9. Method according to one of claims 1 to 8, such that the determined set ( ^^̂) of sources leads to a maximum spectral efficiency ( ^^^^ ^^ ^^ ^^ ^^) .

10. Method according to one of claims 1 to 9, such that, when determining a set ( ^^̂) of sources not yet correctly decoded leading to a maximum spectral efficiency, among all the sets of sources not yet correctly decoded satisfying the condition of a sum of the necessary and sufficient numbers of retransmission intervals less than or equal to ^^ ^^ ^^ ^^, the method discards any game including a source ^^ and not including a source ^^ when ^^ ^^ ≤ ^^ ^^ And > ^^ ^^ , ^^ ^^ { 1, … , ^^ } , ^^ ^^ { 1, … , ^^ } .

11. Method according to one of claims 1 to 9, such that, when determining a set (^^̂) of sources not yet correctly decoded leading to maximum spectral efficiency, among all the sets of sources not yet correctly decoded satisfying the condition of a sum of the necessary and sufficient numbers of retransmission intervals less than or equal to ^^ ^^ ^^ ^^ , the method discards any game including a source ^^ and not including a source ^^ when ^^ ^^ < ^^ ^^ and ^^ ^^ = ^^ ^^, ^^ ^^{1, … , ^^}, ^^ ^^{1, … , ^^}.

12. Communication method with transmission of a frame carrying at least one message implemented by a telecommunications device intended for a telecommunications system comprising ^^ nodes including ^^ sources ( ^^ ^^ ^^ ^^{1, … , ^^}) and ^^ − ^^, relay, ^^ ≥ ^^ ≥ 2, and a destination ( ^^), the device forming one of the sources, the nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the N nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase, the message from a source having been coded before transmission using an incremental redundancy type coding which generates several redundancies, the 1 èrephase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 nde phase includes at least one retransmission interval for a transmission from nodes having correct knowledge of the same source ( ^^ ^^ ) such that these nodes simultaneously transmit during the same retransmission interval the same redundancy of the same message from the same source not yet correctly decoded by the destination, the transmission channel encompassing the transmission channels between the nodes and the destination called direct and the channels between the nodes called indirect, the method is such that it comprises: - transmission of a first redundancy of a message from the device during the 1 èrephase, - reception in a certain form of the sources of a set ( ^^̂) of sources not yet correctly decoded respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals is less than or equal to ^^ ^^ ^^ ^^ and the necessary and sufficient numbers of retransmission intervals of the game sources, - transmission of a second redundancy of one of the sources ( ^^ ^^ ) of the game if the device has correct knowledge of this source, during a retransmission interval of the 2 nde phase, and this a number of times corresponding to the necessary and sufficient number of retransmission intervals of this source.

13. Method according to claim 12 further comprising: - following the reception of an acknowledgment (ACK / NACK) of receipt by the destination of the first redundancy of the message of the device, transmission by the device of quality indicators ( ^^ ^^ ^^ ^^) of indirect channels between this device and other nodes.

14. Telecommunication device (TAL) for transmitting a frame carrying at least one message, intended for a telecommunication system comprising ^^ nodes of which ^^ sources ( ^^ ^^ ^^ ^^{1, … , ^^}) and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ( ^^), the nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase, the message from a source having been coded before transmission using an incremental redundancy type coding which generates several redundancies, the 1 ère phase includes ^^ intervals allocated respectively to the successive transmissions of the first redundancies of the messages from the sources and the second ndephase includes at least one retransmission interval for a transmission from nodes having correct knowledge of the same source ( ^^ ^^ ) such that these nodes simultaneously transmit during the same retransmission interval the same redundancy of the same message from the same source not yet correctly decoded by the destination, the transmission channel encompassing the transmission channels between the nodes and the destination called direct and the channels between the nodes called indirect, the device which corresponds to one of the sources comprises at least one microprocessor (µP), a memory (MEM), a transmitter (EM) and a receiver (RE), the transmitter (EM) comprises an encoder (COD IR) implementing an incremental redundancy type coding which generates several redundancies of the same message to be transmitted, the device is such that: - the transmitter (EM) is able to transmit a first redundancy of a message from the device during the 1 èrephase, - the receiver (RE) is able to receive, in a certain form, sources from a set ( ^^̂) of sources not yet correctly decoded respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals is less than or equal to ^^ ^^ ^^ ^^ and necessary and sufficient numbers of retransmission intervals of the game sources, - the transmitter (EM) is further capable of transmitting a second redundancy of one of the sources ( ^^ ^^ ) of the game if the device has correct knowledge of this source, during a retransmission interval of the 2 ndephase, and this a number of times corresponding to the necessary and sufficient number of retransmission intervals of this source.

15. Device (TAL) according to the preceding claim such that: - the receiver (RE) is further capable of receiving an acknowledgment of receipt by the destination of the first redundancy of the message of the device, - the transmitter (EM) is further capable of transmitting, following the reception of the acknowledgment of receipt, indicators of the quality ( ^^ ^^ ^^ ^^ ) of indirect channels between this device and other nodes.

16. Telecommunication device (BS) intended for a telecommunication system comprising ^^ nodes of which ^^ sources ( ^^ ^^ ^^ ^^ { 1, … , ^^ }) to transmit a frame carrying at least one message, and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ( ^^), the nodes operating in half-duplex mode, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase and a 2 nde phase, the message from a source having been coded before transmission according to a type coding incremental redundancy which generates several redundancies, the 1 ère phase includes ^^ intervals allocated respectively to the successive transmissions of ^^ first redundancies of the ^^ messages from the ^^ sources and the 2 nde phase includes at least one retransmission interval for a transmission from nodes having correct knowledge of the same source ( ^^ ^^) such that these nodes transmit simultaneously during the same retransmission interval the same redundancy of the same message from the same source not yet correctly decoded by the destination, the transmission channel encompassing the transmission channels between the nodes and the destination called direct and the channels between the nodes called indirect, the device which corresponds to the destination comprises at least one microprocessor (µP_BS), a memory (MEM_BS), a transmitter (EM_BS) and a receiver (RE_BS), the receiver (RE_BS) comprises a decoder (DECOD IR) implementing incremental redundancy type decoding to decode the same message from the received redundancies, the device is such that: - the microprocessor (µP_BS) is able to determine numbers ( ^^ ^^ ) of retransmission intervals necessary and sufficient for the destination to decode sources not yet correctly decoded based on knowledge of flow rates ^^ ^^attributed to these sources and a knowledge of a quality ( ^^ ^^ ^^ ^^ ) of the different direct transmission channels and the different indirect transmission channels, to determine a set ( ^^̂) of sources not yet correctly decoded respecting the condition that the sum of the necessary and sufficient numbers of retransmission intervals of the sources ( ^^ ^^ ) of the game ( ^^̂) is less than or equal to the remaining time, called sources to be helped, - the transmitter (EM_BS) is able to broadcast to the nodes in a certain form of the sources of the game ( ^^̂) and the necessary and sufficient numbers of retransmission intervals of these sources, - the receiver (RE_BS) is able to receive, for each source of the game, the same redundancy of this same source coming from the nodes having correct knowledge of this same source during the necessary and sufficient number of retransmission intervals of this same source.

17. System comprising ^^ nodes of which ^^ sources ( ^^^^ ^^ ^^{1, … , ^^}) and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ( ^^), for an implementation of a communication method according to one of claims 1 to 13.

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