Communication method and omamrc system with a selection during retransmissions taking into account a single conditional exchange of csi

Abstract

The present invention relates to a communication method with transmission of a frame transporting messages, intended for a telecommunication system having N nodes including M sources (S i iϵ{1,..., M}) and N — M relays, where N ≥ M ≥ 2, and one destination (D). The 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 numbers of retransmission intervals in order for the destination to decode the sources not yet correctly decoded and a sum of throughputs assigned to the sources. These numbers are first estimated and then determined following a conditional exchange of quality information (CSI j ) of the indirect channels.

Description

[0001] DESCRIPTION TITLE: OMAMRC communication method and system with selection during retransmissions taking into account a single conditional 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 may 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 sources while a source has its own message to transmit and may 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 telecommunication system illustrated by Figure 1 has N 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 a telecommunications system implementing a selection strategy during the second phase is known from the article [1]. The telecommunications 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 terminology node 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, 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. channel use (ie resource element according to 3GPP terminology) is fixed and identical for each source. The independent sources broadcast during the first phase their sequence of coded information in the form of a message for a single recipient. Each source broadcasts its message with its initial bit rate. The destination communicates to each source its initial bit rate via very limited bit 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 signaling overhead while allowing 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 predicting which sources can be correctly decoded by the destination nor making the best use of the time available during the 2. nde phase to decode a maximum of sources. 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 telecommunications system comprising N nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, and a destination, 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 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. 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 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 transmission channels between the nodes called indirect. The method comprises an initialization of a remaining time during the 2 ndephase to ^^ ^^ ^^ ^^ and a determination of a set ^^̂ of sources not yet correctly decoded taking into account numbers of retransmission intervals so that the destination can decode these sources in the remaining time, the sources of the set ^^̂ being such that the sum of their number of retransmission intervals is less than or equal to the remaining time, called sources to be helped. The method implemented by the destination is such that it comprises: - determination of the numbers of retransmission intervals on the basis of knowledge of the bit rates allocated to the sources and at least quality information of the different direct channels between the sources and the destination obtained from the transmissions occurring during the 1 èrephase, these determined numbers of intervals being at least sufficient for the destination to decode these sources, - reception of redundancies transmitted by the nodes having correct knowledge of the sources to be helped, during the determined numbers of intervals, for the destination to decode these sources, and updating of the remaining time after each retransmission interval and, - provided that the set ^^̂ is empty and that there remains at least one source not correctly decoded and that the remaining time is non-zero, determination of the numbers of retransmission intervals on the basis of knowledge of the rates allocated to these sources and knowledge of a quality of the different direct transmission channels and the different indirect transmission channels, these determined numbers of intervals being necessary and sufficient for the destination to decode sources ^^ not yet correctly decoded and,updating the set ^^̂ taking into account the necessary and sufficient numbers of intervals. The destination estimates a number of retransmission intervals sufficient to decode a source not yet correctly decoded on the basis of knowledge of the bit rate allocated to this source and at least the CSI quality information, j of the direct channel. A source is assisted for at most the sufficient number of retransmission intervals by the transmission of a redundancy during the 2 nde phase by the node(s) with correct knowledge of this source, i.e., the transmitted redundancy helps the destination to correctly decode this source. The estimates of the number of retransmission intervals for the different sources not yet correctly decoded may not be sufficient to optimize the use of the remaining time and correctly decode a maximum number of sources. A single transmission of CSI quality information jindirect channels is then conditionally triggered so that the destination determines exactly the number of retransmission intervals necessary and sufficient to decode the sources not yet correctly decoded. Knowing these exact numbers of necessary and sufficient intervals, the destination can then update the set of sources to be helped. The invention has the advantage of limiting the signaling overhead only in certain cases, of not wasting transmission if no source can be helped in the remaining time and of optimizing the number of sources that can be decoded correctly.The invention further relates to a method of communication with transmission of a frame carrying at least one message implemented by a telecommunications device intended for a telecommunications system comprising N nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 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 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 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 nde phase to ^^ ^^ ^^ ^^and determining a set ^^̂ of sources not yet correctly decoded taking into account numbers of retransmission intervals so that the destination can decode these sources in the remaining time, the sources of the set ^^̂ being such that the sum of their number of retransmission intervals is less than or equal to the remaining time, called sources to be helped, the method is such that it comprises: - transmission of a first redundancy of a message from the device during the 1 ère phase, - transmission during a retransmission interval of the 2 ndephase of a second redundancy of the message from a source of the set ^^̂ if the device has correct knowledge of this source, - conditional exchange of control with the destination during which the device transmits quality information of the indirect links of the device with the other nodes. The invention further relates to a telecommunication device for transmitting a frame carrying at least one message, intended for a telecommunication system comprising N nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 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 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 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 ^^ ^^ ^^ ^^and determining a set ^^̂ of sources not yet correctly decoded taking into account numbers of retransmission intervals so that the destination can decode these sources in the remaining time, the sources of the set ^^̂ being such that the sum of their number of retransmission intervals is less than or equal to the remaining time, called sources to be helped, 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 ère phase, - the transmitter is further capable of transmitting during a retransmission interval of the 2 ndephase a second redundancy of the message from a source of the set ^^̂ if the device has correct knowledge of this source, - the transmitter and the receiver being capable of a conditional exchange of control with the destination during which the device transmits quality information of the indirect links of the device with the other nodes. The invention further relates to a base station intended for a telecommunications system comprising N nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 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 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 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 nde phase to ^^ ^^ ^^ ^^and determination of a set ^^̂ of sources not yet correctly decoded taking into account numbers of retransmission intervals so that the destination can decode these sources in the remaining time, the sources of the set ^^̂ being such that the sum of their number of retransmission intervals is less than or equal to the remaining time, called sources to be helped, the base station corresponding to the destination comprises a decoder, a transmitter, a receiver, a microprocessor such that: - the receiver is able to receive successively during the 1 ère phase the ^^ first redundancies of the ^^ messages from the ^^ sources, - the microprocessor is able to determine the number of retransmission intervals on the basis of knowledge of the flow rates allocated to the sources and at least quality information of the different direct channels between the sources and the destination obtained from the transmissions occurring during the 1 èrephase, these determined numbers of intervals being at least sufficient for the destination to decode these sources, - the receiver is furthermore able to receive redundancies transmitted by the nodes having correct knowledge of the sources to be assisted, during the determined numbers of intervals, so that the base station decodes these sources, - the microprocessor is furthermore able to update the remaining time after each retransmission interval, - the microprocessor is furthermore able to determine numbers of retransmission intervals, provided that the set ^^̂ is empty, that there remains at least one source not correctly decoded and that the remaining time is not zero, on the basis of knowledge of the rates allocated to these sources and knowledge of a quality of the different direct transmission channels and of the different indirect transmission channels,these determined numbers of intervals being necessary and sufficient for the destination to decode sources not yet correctly decoded, and to update the set ^^̂ taking into account the necessary and sufficient numbers of intervals. The invention further relates to a telecommunications system comprising ^^ nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, and a destination, for an implementation of a communication method according to another subject of the invention. According to one embodiment, the sources of the set ^^̂ are those which maximize spectral efficiency. According to this mode, the set  of sources to be helped includes the sources not yet correctly decoded which make it possible to maximize spectral efficiency. This mode has the advantage of jointly optimizing the number of sources to be decoded and the total throughput achieved by the decoded sources. According to one embodiment,the method further comprises: - broadcasting to the ^^ nodes at each retransmission interval a source identifier taken from the set ^^̂ and this, a number of times equal to the number of intervals determined for the identified source. The successive selection by the destination of the sources to be helped can be carried out either randomly or in an ordered manner from among those of the set  before reaching the maximum time T, max of the 2 ephase. The scheduling can be done by successively selecting the sources according to the increasing numbers of the interval numbers. According to one embodiment, the broadcast source identifier is randomly selected from the sources of the set ^^̂. According to one embodiment, the method further comprises a comparison between the numbers of retransmission intervals of the sources of the set ^^̂ so that the broadcast source identifier is selected taking into account a scheduling of these numbers of retransmission intervals. According to this mode, the numbers of retransmission intervals are classified according to their value. And, preferably, the method first selects the source for which the number of retransmission intervals is the smallest. The same source is helped for the duration corresponding to this number or for a shorter duration if its correct decoding by the destination occurs before the end of the estimated number.The method thus successively considers the sources remaining to be correctly decoded. The method is stopped when all the sources are correctly decoded by the destination, when no source not yet correctly decoded can be helped or when the maximum time is reached. According to one embodiment, the method further comprises: - broadcasting to the ^^ nodes in an ordered form of the set ^^̂ and the numbers of retransmission intervals of the sources of the set. According to this mode, the destination transmits at most twice the set  and the numbers of retransmission intervals of the sources of the set, i.e., once before and once after updating the set Â. The set  is ordered and the numbers follow the same order.Thus, the nodes successively select the sources from the set  following the order and as the succession of the numbers of intervals follows the same order they can easily make the association between source and associated number of intervals. The ordering can for example be a function of the increasing numbers of the numbers of intervals or a function of the source identifiers. According to one embodiment, the method further comprises: - broadcasting a request to the ^^ nodes indicating to them to transmit channel quality information between the nodes, called indirect channels, - receiving quality information from the indirect channels. The broadcasting of the request occurs in particular under the condition that the set  is empty and that there remains at least one source not correctly decoded and that the remaining time is non-zero.According to one embodiment, if the correct decoding of a source occurs before the end of the at least sufficient number of retransmission intervals then the method updates the set ^^̂. Since the correct decoding by the destination of a source can occur before the end of the sufficient number of retransmission intervals, this mode can allow another source to be helped to benefit from the time not consumed to be decoded correctly. According to one embodiment, the determination of the at least sufficient numbers of retransmission intervals is further based on a transmission by the nodes at the beginning of the 2. ndephase of their set of correctly decoded sources. According to this mode, the determination of the at least sufficient number of retransmission intervals is more precise since it can take into account quality information on all direct links obtained from the transmission by the nodes of their set of correctly decoded sources. According to one embodiment, during a control exchange with the nodes at the beginning of the 2 ephase, the destination sends its set of correctly decoded sources and the nodes send their set of correctly decoded sources and not yet correctly decoded by the destination and such that the determination of the at least sufficient numbers of retransmission intervals is further based on the transmission by the nodes of their set of correctly decoded sources and not yet correctly decoded by the destination. This mode makes it possible to limit the control exchanges between the nodes and the destination while making it possible to obtain quality information on direct links obtained from the transmission by the nodes of their set of correctly decoded sources and therefore to refine the estimation of the at least sufficient numbers of retransmission intervals. According to one embodiment, if no source can be helped in the time remaining before the end of the 2 ndephase then the transmission of the frame is interrupted before the maximum number of retransmission intervals is used. The embodiment features presented above may optionally be combined with each other to define a new embodiment. 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 may be incorporated into any entity or device capable of storing the program.The memory 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 optional characteristics presented above in the context of the communication method may possibly apply to the software application and the memory mentioned above.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 so-called Cooperative OMAMRC (Orthogonal Multiple Access Multiple Relays Channel) system 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 protocol of the decoding control 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. A telecommunication system according to the invention comprises ^^ nodes including ^^ sources which belong to the set of sources ^^ =. and ^^ = ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, which belong to the relay set ^^ = { ^^1, … , ^^ ^^ } and a destination ^^. By convention, it is considered that ^^ ^^ = = ^^ + ^^ ∀ ^^ ∈ {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 set ^^ 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 ^^ ∈ { 1, … , ^^ + ^^ } . 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 1 ère phase. During the 2 ndephase, access to the transmission channel of the N nodes that 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 that 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 statistical 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 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 frames, • ^^^^ ^^ ^^ ^^is the number of retransmission intervals used during the 2 nde phase, ^^^^ ^^ ^^ ^^∈ {1, …, ^^ ^^ ^^ ^^ } , it corresponds to the number of transmissions during this phase, • ^^ = ^^2 ⁄ ^^1 is the ratio of the number of channel uses available at each slot 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, • O ^^, ^^ is the default indicator (outage) after l (l=0,…, ^^ ^^) 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 ^^ ^^ retransmission helping this source. • ^^ ^^, ^^ represents the mutual information between the source ^^ ∈ {1, … , ^^} and the destination ^^, • ^^ ^̅^, ^^ ( ^^) 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 ^^ 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 ^^ ^^ to a ready 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, the channel can be written: ℎ ∗ The multiplicative coefficients ^^ can be, for example, equal to ^ ^^, ^^ ^^ ^ ^^ = |ℎ ^^, ^^ | if each node ^^ ∈ ^^ with knowledge of 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 one embodiment. The sources ^^ ∈ ^^ 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 ^^ ^^ , ^^ 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 typically includes one or more reference signals. By exploiting these reference signals (pilot symbols, 3GPP LTE SRS signals, etc.), the destination can determine capacity information, in particular the gains (CSI Channel State Information) of the direct links: ^^. ^^ ^^ ^^ = {ℎ ^^1, ^^, … , ℎ^^ ^^ , ^^}, i.e., source-to-destination links and can therefore deduce the SNRs of these links and thus their quality and capacity. Whether during the first phase or the second phase, when a node transmits, in particular a source, the destination and other nodes listen. The destination, sources and relays attempt to decode the received redundancies at the end of a time interval. The success of the decoding at each node is decided using the CRC. The destination and nodes thus determine their set of correctly decoded sources at each time interval, ^^ ^^, ^^−1 ^^ ^^, ^^−1 . The 2 nde The transmission phase of the process includes ^^ = {1, … , ^^^^ ^^ ^^ ^^} retransmission intervals with the convention that ^^ = 0 corresponds to the last transmission interval of the first phase. The term retransmission associated with an interval is used in connection with the 2 ndephase 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 ère phase. According to the method, there is no exchange of decoding control between the destination and the nodes at each retransmission interval: on the one hand, 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, on the other hand, 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. At the beginning of the first phase, the destination estimates, for the sources not yet correctly decoded, ^^ ^^ ∈ ^^ ^̅^,0 , the numbers ^^ ^^sufficient retransmission intervals for the destination to decode these sources based on knowledge of the bit rates ^^ ^^ assigned to these sources and at least the capacity information of the different direct channels between the sources and the destination. According to a first embodiment, the numbers ^^ ^^ sufficient retransmission intervals are estimated based on the bit rates ^^ ^^ and only the knowledge of the fading of the different direct links between the sources and the destination. According to a second embodiment, the estimation of the numbers ^^ ^^ sufficient retransmission intervals further takes into account the knowledge of the source sets correctly decoded by the nodes at the end of the transmission phase by the destination. This information requires an exchange of correctly decoded source sets between the nodes and the destination at the end of the transmission phase. These numbers ^^^^ of sufficient retransmission intervals limit the exact number of intervals that are necessary and sufficient for the destination to decode the sources not yet correctly decoded. The set ^^̂ of sources to be helped includes among the sources not yet correctly decoded those or some of those that the destination is sure to be able to decode in the remaining time ^^ ^^ ^^ knowing the numbers ^^ ^^ of retransmission intervals sufficient to decode these sources. The optimal set ^^̂ of sources to be helped is the set of sources not yet decoded which optimizes spectral efficiency. At each retransmission interval ^^, the destination broadcasts the number of the source ^^ to be helped taken from the set ^^̂ of sources to be helped. At each retransmission interval ^^ and before selecting the number of a source to be helped, the remaining number of retransmission intervals ^^ ^^ ^^ is: ^^ ^^ ^^ = ^^ ^^ ^^ ^^− ^^^^ ^^ ^^ ^^. A ^^ = 0, ^^^^ ^^ ^^ ^^= 0, ^^ ^^ ^^ = ^^ ^^ ^^ ^^ . According to a first embodiment, the destination does not require an exchange of control at the end of the 1st phase. The capacity of the channel between a node ^^, ^^ ∈ {1, … , ^^}, and the destination is deduced from the quality of the channel, i.e. the mutual information ^^ ^^, ^^ between this node ^^ and the destination ^^. The number ^^ ^^ sufficient retransmission intervals to decode a source ^^ ^^ ∈ ^^ ^̅^,0 among the sources not yet correctly decoded by the destination is estimated from the information ^^ ^^, ^^ capacity of the direct channel between this source and the destination obtained from the transmission of this source occurring during the 1st phase: According to the second embodiment, the destination requires a control exchange at the end of the 1st phase to obtain the sets of sources correctly decoded by the nodes at the retransmission interval ^^ = 0. At the end of the control exchange, an equivalent channel is determined for each source ^^ not yet correctly decoded. This equivalent channel considered groups the channels between each of the nodes having correct knowledge of the source ^^ and the destination. The capacity of the equivalent channel is evaluated by the mutual information ^^ ^̅^, ^^ (1) determined between the set of nodes having correct knowledge of the source ^^ and the destination. The number ^^ ^^ sufficient retransmission intervals to decode a source not yet correctly decoded ∈ ^^ ^̅^,0is estimated from the capacity information of the direct channel between the source and the destination obtained from the transmission of this source occurring during the 1st phase and from the information ^^ ^̅^, ^^ (1) equivalent channel quality between nodes having correct knowledge of this same source and the destination determined from the sets of sources correctly decoded by the nodes: ^^ ^^ ^^ = ⌈ ^^ − ^^ ^^, ^^ ^^ ^^ ^̅^, ^^ (1)⌉ (2) Thus, according to this second mode, the nodes transmit to the destination their set of correctly decoded sources or at least their set of correctly decoded sources not yet correctly decoded by the destination only once, i.e. at the end of the last transmission interval, ^^ = 0 or equivalently at the beginning of the 1 er retransmission interval, ^^ = 1. Subsequently, the mutual information ^^ ^̅^, ^^(1) is defined as the information of the quality of the equivalent channel between the nodes having decoded the same source ^^ and the destination from the knowledge of the fading of the direct channels and the indirect channels for the first retransmission helping the source ^^, i.e., knowing the nodes having decoded the source ^^ after the transmission phase. The transmission by a node classically comprises one or more reference signals. The destination estimates in a known manner the channel and therefore its quality or its capacity between each of the nodes and the destination by exploiting for example the reference signal(s) received at this interval. By exploiting these reference signals (pilot symbols, SRS signals of 3GPP LTE, etc.), the destination can determine the gains (CSI Channel State Information) of the direct links between the relays and the destination and can therefore deduce the average SNR of these links and therefore their quality and their capacity. If the estimation of the ^^^^ is such that for all sources ^^ ∈ {1, … , ^^} the following inequality is satisfied: then all sources can be decoded without conditional exchange. All sources can be decoded correctly by the destination in the remaining time, the process choosing for example successively the sources to be helped and randomly. Knowing the numbers ^^ ^^ sufficient retransmission intervals to decode a source ^^ ^^ ∈ the destination determines the set ^^̂ of sources ∈ ^^ ^̅^,0 not yet correctly decoded for which the sum of the numbers ^^ ^^ of sufficient retransmission intervals is less than or equal to ^^ ^^ ^^ ^^ , ∑ ^^∈ ^^ ^^ ^^ ≤ ^^ ^^ ^^ ^^ , and, according to one embodiment, which maximize spectral efficiency ^^^^ ^^ ^^ ^^ ^^, say sources to help:} The destination selects at each retransmission interval a source, called the source to be helped, by broadcasting the number ^^ of the source taken from among the sources of the set ^^̂, ∈ ^^̂, via a control channel from the destination to the nodes. The nodes that have correctly decoded this source then transmit the same redundancy ^^ ^^̂ ^^ of the message from this source during this retransmission interval using a data channel to help the destination to correctly decode this source. As soon as the destination correctly decodes a source, it updates the set ^^̂ of sources to be helped. Whatever the embodiment, the method is particular in that it comprises a single conditional exchange of control of capability information, ^^ ^^ ^^ ^^ , to obtain capacity information on indirect links and determine a time, ie, a number of time intervals necessary and sufficient to decode a source not yet correctly decoded: ^^ ^^ = argm ∗in { ^^} such that ^^∈ℕ ^^ ^^ is therefore the exact number of time intervals to decode a source ^^ ^^ not yet decoded, ∈ ^^ ^̅^, ^^ , by the destination. After the conditional exchange the destination redetermines the set of sources to help ^^̂. Knowing the numbers ^^ ^^ of retransmission intervals necessary and sufficient to decode the sources ∈ ^^ ^̅^, ^^ from the time interval ^^, the destination redetermines the set ^^̂ of sources, called sources to be helped, not yet correctly decoded ∈ ^^ ^̅^, ^^ for which the sum of the numbers ^^ ^^ of necessary and sufficient retransmission intervals is less than or equal to ^^ ^^ ^^ ^^ , ∑ ^^∈ ^^ ^^ ^^ ≤ ^^ ^^ ^^ ^^, and which, according to one embodiment, maximizes spectral efficiency ^^^^ ^^ ^^ ^^ ^^: such as ^^∈ ^^ ^^ ^^ ≤ ^^ ^^ ^^ with ^^( ^^ ^̅^, ^^ ) the power play of ^^ ^̅^, ^^ that is, the set of all possible sets of sources not yet correctly decoded and ^^ any set of ^^ . The exchange to obtain the ^^ ^^ ^^ ^^ occurs only once. By conditioning this exchange, the process allows the signaling overhead to be limited while still allowing the decoding of the maximum number of sources that provide maximum total throughput. The destination requires this single conditional exchange of capacity information control ^^ ^^ ^^ ^^to obtain information on the capacity of indirect links and determine the time necessary and sufficient to decode a source not yet correctly decoded: - either when the set of sources to be helped is empty, ^^̂ = ∅, although the destination has not correctly decoded all the sources at the end of the 1 ère phase, the time remaining before the end of the frame transmission cycle being insufficient to decode at least one source among the sources not correctly decoded by the destination knowing the ^^ ^^ of the sources remaining to be decoded, - either when there are still sources to be decoded and when the destination has correctly decoded a source from the set of sources to be helped ^^̂ without using all the sufficient retransmission intervals of the number ^^ ^^ initially determined. The individual fault event of the source ^^ ^^ ^^, ^^ ^^ , can be expressed in the following form: This expression reflects the fact that the source ^^ is not decoded correctly at the end of retransmissions (helping this source) if the flow ^^ ^^ of the source is greater than the sum of the transmission capacities. This transmission capacity includes the capacity of the channel between this source ^^ and the destination which occurs during the 1 ère phase and a sum weighted by ^^ of the capacities of the equivalent channels which occur during the second phase. Figure 4 is a diagram of the simplified structure of an embodiment of a base station BS according to an embodiment of the invention. This base station is intended for a telecommunication system comprising ^^ nodes of which ^^ sources ^^ ^^^^ ^^{1, … , ^^} and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ^^, the base station BS corresponds to the destination. Access to the transmission channel between the nodes and the base station BS is of orthogonal multiple type. The protocol of exchanges between the nodes and the base station BS defines a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase of ^^ time intervals and a 2 e phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^. The base station 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 base station BS can be connected by means of a connection other than a bus. The receiver RE_BS comprises at least one decoder DECOD IR of received messages having been coded according to an incremental redundancy type coding which generates several redundancies. The decoder attempts to decode a message received from a source from the 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 base station 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, intermediate data of calculations performed by the microprocessor µP, 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 manner readable by a microprocessor. Examples of memory MEM_BS include non-transitory storage media such as semiconductor memory devices, and magnetic, optical, or magneto-optical recording media loaded into a read-write unit driven by the microprocessor. At initialization, the program code instructions are, for example, loaded into a buffer memory before being executed by the microprocessor µP_BS.The microprocessor µP_BS controls the various components of the base station BS. Thus, by executing the instructions, the microprocessor µP_BS enables the base station BS to implement the communication method according to an embodiment of the invention, which comprises: - reception during the 1. ère phase of ^^ first redundancies of ^^ messages from ^^ sources, ^^1, … , ^^ ^^ implemented by the receiver RE_BS, - a transmission of the number of a source ^^ selected not yet correctly decoded by the base station BS, called source to be helped, implemented by the transmitter EM_BS at each retransmission interval of the 2 e phase, - a reception during the same retransmission interval of the 2 nde phase, of the same second redundancy ^^ ^^̂ ^^ from the same source ^^ ^^selected and coming from different nodes having correct knowledge of this same source, implemented by the receiver RE_BS, - a conditional control exchange with the nodes during which the base station BS receives quality information from the indirect links ^^ ^^ ^^ ^^ , implemented by the transmitter EM_BS and by the receiver RE_BS. Figure 5 is a diagram of the simplified structure of an embodiment of a TAL terminal according to an embodiment of the invention. This terminal is intended for a telecommunication system comprising ^^ nodes including ^^ sources ^^ ^^ ^^ ^^ { 1, … , ^^ } and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ^^, the TAL terminal corresponds to one of the sources. Access to the transmission channel between the nodes and the destination is of orthogonal multiple type. The protocol of the exchanges between the nodes and the destination defines a maximum number of ^^ + ^^ ^^ ^^ ^^time intervals per transmitted frame distributed between a 1 ère phase of ^^ time intervals and a 2 e phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^. The TAL terminal 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 terminal can be connected by means of a connection other than a bus. The transmitter ER comprises at least one COD IR encoder of messages according to an incremental redundancy type encoding which generates several redundancies for the same message to be encoded. The microprocessor µP controls the operations of the TAL terminal.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 processor 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) which executes a program stored in a memory thereof. The memory MEM may be formed by any suitable means capable of storing the program or programs and data in a computer-readable manner.Examples of MEM memory include non-transitory storage media such as semiconductor memory devices, and magnetic, optical or magneto-optical recording media loaded into a read and write unit controlled by the microprocessor. At 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 terminal TAL. Thus, by executing the instructions, the microprocessor μP allows the implementation by the terminal TAL of the communication method according to an embodiment of the invention. The terminal TAL is capable of transmitting a framed message. Of course, the terminal TAL can transmit several messages successively.The communication method implemented by the TAL terminal is such that it comprises an incremental redundancy type coding implemented by the COD IR coder of the EM transmitter which generates several redundancies of the same message to be transmitted. The transmission by the TAL terminal is of the time division multiplexing type. The communication method implemented by the TAL terminal comprises: - a transmission of a first redundancy of the message from the terminal to be transmitted during the 1. ère phase, implemented by the EM transmitter, - a reception of a source number ^^ ^^ indicating a selected source not yet correctly decoded by the destination called source to be helped, implemented by the receiver RE, - a transmission during a retransmission interval of the 2 ndephase of a second redundancy of the message of this selected source if the terminal TAL has correct knowledge of this source, implemented by the transmitter EM, - a conditional control exchange with the destination during which the terminal TAL transmits quality information of the indirect links of the terminal TAL with the other nodes, implemented by the transmitter EM and by the receiver RE. Examples of particular modes of implementation The following description of an embodiment of the invention is illustrated with an implementation by an OMARC system with ^^ = 3 sources, ^^ = {1,2,3}, ^^ = 3 relays, ^^ = {4,5,6}, and a destination and according to the example of progress illustrated by the algorithm of Appendix B. The parameter ^^ ^^ ^^ ^^ is set at five. The flow rates ^^ ^^of the sources have the following values: ^^1= 1, ^^2= ​​2, ^^3= 3. ^^̂ is the set of incorrectly decoded sources that satisfies the condition on the sum of the numbers of retransmission intervals which must be less than the remaining time and which leads to the highest spectral efficiency ^^^^ ^^ ^^ ^^ ^^. According to the example, during the 2 nde phase, the selection at each retransmission interval of the source ^^ to be helped from the set ^^̂ takes place according to the algorithm in Appendix B. Step 1. At the end of the 1 ère phase, or at the beginning of the 2 nde phase, ie, ^^ = 1, the remaining time ^^ ^^ ^^ is initialized to ^^ ^^ ^^ ^^ , 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 1 ère phase. Step 2. The destination estimates a number of intervals needed ^^ ^^ for the destination to decode a source ^^ not yet decoded, ^^ ∈ ^^ ^̅^,0 , based on knowledge of at least one mutual information ^^ ^^, ^^ from the source link ^^ destination, direct channel, and a flow rate ^^ ^^ assigned to this source ^^. The destination therefore calculates ^^ ^^ for all ^^ ∈ ^^ ^̅^,0 . According to a 1 erembodiment, only the mutual information of the source link ^^ destination, direct channel, and the flow rate ^^ ^^ are taken into account for the calculation of ^^ ^^ : For the example according to this 1 er mode, variables ^^ ^^ have the following values: ^^1= 4, ^^2= ​​3, ^^3= 3. According to a 2 e embodiment, an exchange of control occurs with transmission by the nodes of their set of sources of which they have correct knowledge, ^^ ^^,0 The destination acknowledges the transmissions from the sources at the end of the 1 ère phase. If the acknowledgment indicates that it has not correctly decoded all sources, for example a NACK control signal, then the nodes transmit their set ^^ ^^,0 , ^^ ∈ ^^ ∪ ^^ = {1,2,3,4,5,6}. The estimate of ^^ ^^ can then take into account the mutual information of the source link ^^ destination, direct channel, of the flow rate ^^ ^^ and mutual information ^^^̅^, ^^ (1) of the equivalent channel between the nodes having correct knowledge of this source and the destination: For example, according to this 2 e mode, variables ^^ ^^ have the following values: ^^1= 3, ^^2= ​​2, ^^3= 3, Step 3. The destination determines the set ^^̂ of sources to help among the sources it has not yet correctly decoded ^^ ^̅^,0 . The set ^^̂ comprises the set of sources not yet correctly decoded that satisfies the condition of the number of remaining retransmission intervals, i.e., each source in the set ^^̂ is decoded in the remaining time ^^ ^^ ^^ ^^ (since ^^ = 0) and which leads to the highest spectral efficiency ^^^^ ^^ ^^ ^^ ^^. According to the example, according to the 1 er mode, the possible choices for ^^̂ which satisfy ∑ ^^∈ ^^ ^^ ^^ ≤ ^^ ^^ ^^ ^^ are: {1}, {2}, {3}. The criterion of spectral efficiency per frame gives: < < = According to the example, according to the 2 efashion, the possible choices for ^^̂ which satisfy ∑ ^^∈ ^^̂ ^^ ^^ ≤ ^^ ^^ ^^ ^^ are : { 1 } , { 2 } , { 3 } , { 1.2 } , { 2.3 } The criterion of spectral efficiency per frame gives: < < < < = Step 4. Initializing the control exchange indicator of ^^ ^^ ^^ ^^ to 0: ^^ ^^ ^^ ^^ ^^ ^^ ^^ = 0 According to the example, according to the 1 er mode and according to the 2 e mode, at current interval ^^ = 1 no exchange of control of ^^ ^^ ^^ ^^ has not intervened then the destination initializes the indicator to 0, ie, ^^ ^^ ^^ ^^ ^^ ^^ ^^ = 0. Step 5. If the set ^^̂ = ^^,.ie, no source can be helped in the remaining time and if ^^ ^̅^, ^^−1≠ ^^, ie, the destination could not decode all the sources then the process goes to step 6 otherwise the process goes to step 8. According to the example, for each of the two modes, the condition ^^̂ = ^^ and ^^ ^̅^, ^^ ≠ ^^ is not verified, so the process proceeds to step 8. Step 6. After a control exchange of ^^ ^^ ^^ ^^ to know the quality of the direct and indirect links, the method redetermines the set ^^̂. To this end, the method is carried out according to the algorithm of Appendix A. This determination of the set ^^̂ according to Appendix A is based on an exchange of control with the reception of the ^^ ^^ ^^ ^^indirect links, step 1 of the algorithm in Appendix A. The destination requires that the nodes transmit information related to the quality of the indirect channels. Indirect channels include all channels between sources, channels between relays, and channels between sources and relays, i.e., all channels between nodes. From the transmissions occurring during the 1 ère phase and during the 2 e phase, the destination can determine quality information of the direct channels, i.e., between the nodes 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 ^^ not yet correctly decoded the number of necessary and sufficient retransmission intervals ^^ ^^to correctly decode this source ^^, based on knowledge of mutual information of the direct source ^^ destination link, mutual information of the equivalent channels (for a given source, an equivalent channel at the interval ^^ is considered to be the aggregation of the channels between the nodes having correct knowledge of this same source at this interval ^^ and the destination) and the flow rate assigned to this source ^^. The destination therefore calculates ^^ ^^ for all ^^ ∈ ^^ ^̅^,t−1 . This number ^^ ^^ is the smallest number ^^ of retransmissions after which there is no decoding error, i.e., the bit 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 ∑ ^^ ^ ^=1 ^^ ^̅^, ^^( ^^) weighted by ^^ equivalent channels for the ^^ retransmission intervals (helping source i). Step 3 of the algorithm in Appendix A. The destination determines the set ^^̂ knowing the necessary and sufficient 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 leads to the highest spectral efficiency ^^^^ ^^ ^^ ^^ ^^ and which satisfies the condition of the number of remaining retransmission intervals, i.e., each source in the set ^^̂ is decoded in the remaining time. The destination broadcasts to the nodes jointly in the same order, the set ^^̂ and the necessary and sufficient numbers of time intervals ^^ ^^ = from each source in the game ^^̂. Step 7. The destination updates the control exchange indicator of ^^ ^^ ^^ ^^, ie, ^^ ^^ ^^ ^^ ^^ ^^ ^^ = −1 to signify that an exchange has already taken place and to avoid another subsequent exchange of control of ^^ ^^ ^^ ^^ by testing this indicator. Step 8. End of the if of step 5. Step 9. As long as there remains a source ^^ to help in the set ^^̂, ie, ^^̂ ≠ ^^, the process performs steps 10-38. According to the example, according to the 1 er mode, at ^^ = 1, ^^̂ = {3}. Then at ^^ = 4, ^^ ^^ ^^ = 2, ^^̂ = { 2 } (looping back from step 38 after re-determining ^^̂ between steps 17-20). According to the example, according to the 2 e mode, at ^^ = 1 ^^̂ = {2, 3} and at ^^ = 3, ^^̂ = { 3}. Step 10. Testing the indicator: if no exchange of ^^ ^^ ^^ ^^ has not yet taken place, the indicator is at zero, and the method goes to step 11 otherwise the method goes to step 28 to deal with the case where an exchange of ^^ ^^ ^^ ^^has already taken place. Step 11. At retransmission interval ^^, the destination selects a source ^^ from the set ^^̂. When there are multiple sources in ^^̂ then the first selection of a source can be random or can for example follow an ascending or descending order of the ^^ ^^ or source numbers. According to the example, according to the 1 er mode, at ^^ = 1, the destination selects source 3. Then at ^^ = 4, the destination selects source 2. According to the example, according to the 2 emode, at ^^ = 1, the destination selects source 2 then at ^^ = 3 the destination selects source 3. Step 12. The process repeats steps 13-27 until source ^^ is correctly decoded by the destination. Step 13. The destination requests help from the nodes for source ^^. At each retransmission interval ^^ the destination broadcasts to the nodes the number of the source ^^ to be helped by the nodes. The nodes having correct knowledge of this source ^^ transmit the same redundancy of this same source ^^ during the current retransmission interval ^^. According to the example, according to the 1 er mode, at ^^ = 1, at ^^ = 2 and at ^^ = 3 the destination broadcasts the number 3. At ^^ = 1, the nodes which have correct knowledge of the source 3 transmit a same 2 e redundancy of the message from source 3 considering that during the 1 ère phase source 3 transmitted a 1 èreredundancy of its message. Then at ^^ = 2 the nodes which have correct knowledge of the source 3 transmit the same 3 e redundancy of the message from source 3, then at ^^ = 3 the same 4 e redundancy of the message from source 3. Then at ^^ = 4 and at ^^ = 5 the destination broadcasts the number 2. The nodes which have correct knowledge of source 2 transmit the same redundancy of the message from source 2, i.e., a 2 e redundancy at ^^ = 4 and a 3 e redundancy at ^^ = 5 considering that during the 1 ère phase source 2 transmitted a 1 ère redundancy of his message. According to the example, according to the 2 e mode, at ^^ = 1, then at ^^ = 2, the destination broadcasts the number 2. Nodes that have correct knowledge of source 2 transmit the same redundancy of the message from source 2, i.e., a 2 e redundancy at ^^ = 1 and a 3 eredundancy at ^^ = 2 of the message from source 2. Then, after source 2 is correctly decoded, at ^^ = 3, at ^^ = 4 and at ^^ = 5, the destination broadcasts number 3. Nodes that have correct knowledge of source 3 transmit a same redundancy of the message from source 3, i.e., a 2 e redundancy at ^^ = 3, a 3 e redundancy at ^^ = 4 and a 4 e redundancy at ^^ = 5 of the message from source 3. Step 14. The method increments the value of the current retransmission interval, ^^ ← ^^ + 1. According to the example, according to the 1 er fashion, for the 1 ère loop (from step 12), ^^ = 3, ^^ = 1 + 1 = 2. When ^^ = 3, for the 2 e loop (from step 12), ^^ = 2 + 1 = 3. Then, ^^ = 2, for the 1 ère loop (from step 12) ^^ = 3 + 1 = 4 and for the 2 e loop (from step 12), ^^ = 4 + 1 = 5 and the source ^^ = 2 is decoded during this 2 e loop. According to the example, according to the 2 e fashion, for the 1ère loop (from step 12), ^^ = 2, ^^ = 1 + 1 = 2. When ^^ = 2, for the 2 e loop (from step 12), ^^ = 2 + 1 = 3 and the source ^^ = 2 is decoded during this 2 e loop and the next source is selected in step 11. ^^ = 3 + 1 = 4 for the 1 ère loop (from step 12) with ^^ = 3. When ^^ = 3, for the 2 e loop (from step 12), ^^ = 4 + 1 = 5. When ^^ = 3, for the 3 e loop (from step 12), ^^ = 5 + 1 = 6 and the source ^^ = 3 is decoded during this 3 e loop. Step 14. The process decrements the remaining time, ^^ ^^ ^^ ← ^^ ^^ ^^ − 1 and decrements the value of ^^ ^^ since ^^ was helped once by the nodes. According to the example, according to the 1 er mode, when ^^ ← 2, ^^ ^^ ^^ = ^^ ^^ ^^ ^^ − 1 = 4, ^^3= 2 then when ^^ ← 3, ^^ ^^ ^^ = 3, ^^3= 1 then when ^^ ← 4, ^^ ^^ ^^ = 2, ^^3= 0. Then when ^^ ← 5, ^^ ^^ ^^= 2 − 1 = 1, ^^2= ​​^^2= ​​1 then when ^^ ← 6, ^^ ^^ ^^ = 0, ^^2= ​​0. According to the example, according to the 2 e mode, when ^^ ← 2, ^^ ^^ ^^ = ^^ ^^ ^^ ^^ − 1 = 4, ^^2= ​​1 then when ^^ ← 3, ^^ ^^ ^^ = 3, ^^2= ​​0 then when ^^ ← 4, ^^ ^^ ^^ = 2, ^^3= 2, then when ^^ ← 5, ^^ ^^ ^^ = 1, ^^3= 1, then when ^^ ← 6, ^^ ^^ ^^ = 0, ^^3= 0. Step 15. If the destination has correctly decoded the source ^^ at the interval ^^ − 1 then the process performs steps 16-25 otherwise the process goes to step 26 then 27 and possibly loops back to step 12. According to the example, according to the 1 er mode, when ^^ = 3, source 3 is correctly decoded into three retransmission intervals since initially ^^3= 3. So as long as ^^ − 1 < 3 the process loops back to step 12. When ^^ = 4, ^^ ^^,3= {3} then the process proceeds to step 16. Then, when ^^ = 2, source 2 is correctly decoded in two retransmission intervals since ^^2= ​​^^2= ​​2. So as long as ^^ − 1 < 5 the process loops back to step 12. When ^^ = 6, ^^ ^^,5 = {2,3} then the process proceeds to step 16. According to the example, according to the 2 e mode, when ^^ = 2, source 2 is correctly decoded in two retransmission intervals since initially ^^2= ​​2. So as long as ^^ − 1 < 2 the process loops back to step 12. When ^^ = 3, ^^ ^^,2 = {2} then the process proceeds to step 16. Then, when ^^ = 3, source 3 is correctly decoded in three retransmission intervals since ^^3= 3. So as long as ^^ − 1 < 5 the process loops back to step 12. When ^^ = 6, ^^ ^^,5 = {2,3} then the method proceeds to step 16. Step 16. The correctly decoded source ^^ at the interval ^^ − 1 is removed from the set ^^̂ and the method proceeds to step 17. According to the example, according to the 1er mode, at ^^ = 4, the source ^^ = 3 is correctly decoded then ^^̂ = ^^̂ \ {3} = ∅ and ^^ ^^ ^^ = 2 and the process goes to step 17. Then at ^^ = 6, the source ^^ = 2 is correctly decoded so ^^̂ = ^^̂ \ { 2 } = ∅ and ^^ ^^ ^^ = 0 and the process proceeds to step 17. According to the example, according to the 2 e mode, at ^^ = 3, the source ^^ = 2 is correctly decoded then ^^̂ = ^^̂ \ {2} = {3} and ^^ ^^ ^^ = 3 and the process goes to step 17. Then at ^^ = 6, the source ^^ = 3 is correctly decoded so ^^̂ = ^^̂ \ { 3 } = ∅ and ^^ ^^ ^^ = 0 and the process goes to step 17. Step 17. If there are still sources to decode and time remaining then the process goes through steps 18-24 otherwise the process goes to step 25. According to the example, according to the 1 er mode, at ^^ = 4, ^^ ^̅^,3 = {1,2} ≠ ∅ and ^^ ^^ ^^ = 2 so the process goes to step 18. Then at ^^ = 6, ^^ ^̅^,5 = { 1 }≠ ∅ but ^^ ^^ ^^ = 0 then the process goes to step 25. According to the example, according to the 2 e mode, at ^^ = 3, ^^ ^̅^,2 = {1,3} ≠ ∅ and ^^ ^^ ^^ = 3 so the process goes to step 18. Then at ^^ = 6, ^^ ^̅^,5 = { 1 } ≠ ∅ but ^^ ^^ ^^ = 0 then the process proceeds to step 25. Step 18. If the source ^^ was decoded before the initially estimated time, i.e., ^^ ^^ > 0, then the process goes to step 19 and otherwise to step 20. According to the example, according to the 1 er mode, at ^^ = 4, ^^3= 0, ie, the destination needed the three intervals to decode the source 3 so the process goes to step 20. According to the example, according to the 2 e mode, at ^^ = 3, ^^2= ​​0, ie, the destination has indeed needed both intervals to decode source 2 so the process goes to step 20. Step 19. The destination redetermines the set ^^̂ of sources to help among the sources that it has not yet correctly decoded ^^ by using the algorithm in Appendix A. The set ^^̂ includes the set of sources not yet correctly decoded that satisfies the condition of the number of remaining retransmission intervals, i.e., each source in the set ^^̂ is decoded in the remaining time and that leads to the highest spectral efficiency ^^^^ ^^ ^^ ^^ ^^. Step 20. End of if of step 18. Step 21. If the set ^^̂ of sources to be helped is empty and no exchange of control of the qualities of the indirect links has yet taken place, i.e., ^^ ^^ ^^ ^^ ^^ ^^ ^^ = 0 then the method goes to step 22 and otherwise to step 24. According to the example, according to the 1 er mode, at ^^ = 4, ^^3= 0, ^^̂ = ∅ and ^^ ^^ ^^ ^^ ^^ ^^ ^^ = 0 then the process goes to step 22. According to the example, according to the 2 e mode, at ^^ = 3, ie, ^^̂ = { 3 }≠ ∅ then the process proceeds to step 24. Step 22. The destination determines the set ^^̂. This determination takes place according to the algorithm in Appendix A in the same way as in step 6. According to the example, according to the 1 er mode, at ^^ = 4, ^^ ^^ ^^ = 2, the process redetermines the set ^^̂. The destination calculates ^^ ^^ = for all ^^ ∈ ^^ ^̅^,t−1 = {1,2} knowing the quality of the indirect and direct channels. As according to the example = 2, ^^2= ​​2 and that ^^1= 1, ^^2= ​​2 then source 2 leads to a better spectral efficiency therefore ^^̂ = { 2 } . Step 23. The destination updates the control exchange indicator of ^^ ^^ ^^ ^^ , ie, ^^ ^^ ^^ ^^ ^^ ^^ ^^ = −1 to signify that an exchange has already taken place and to avoid another subsequent exchange of control of ^^ ^^ ^^ ^^by testing this indicator. Step 24. End of if of step 21. The method goes to step 25. Step 25. End of if of step 17. The method goes to step 26. Step 26. End of if of step 15. The method goes to step 27. Step 27. End of while loop of step 12. The method loops back to step 12 as long as the source ^^ is not decoded correctly and otherwise the method goes to step 38. According to the example, according to the 1 er mode and according to the 2 e fashion, there was no exchange of ^^ ^^ ^^ ^^ before step 10, the method proceeds to step 38. Step 28. Case where ^^ ^^ ^^ ^^ ^^ ^^ ^^ = −1 in step 10, i.e., an exchange of ^^ ^^ ^^ ^^ has already taken place before step 10. In this case, the process proceeds through steps 29-37. Step 29. The nodes successively select the ^^̂ ^^say sources to help taken in the game ^^̂, in the order they appear in the game, one after the other. Step 30. As long as for the source ^^ selected the number ^^ ^^ is not zero, the method performs steps 31-36, i.e., the loop is traversed ^^ ^^ times for source ^^. Step 31. At each retransmission interval ^^, the nodes having correct knowledge of this source ^^ transmit the same redundancy of this same source ^^ during the current retransmission interval ^^. Step 32. The method increments the value of the current retransmission interval, ^^ ← ^^ + 1. The method decrements the remaining time, ^^ ^^ ^^ ← ^^ ^^ ^^ − 1 and decrements the value of ^^ ^^ since ^^ has been helped once by the nodes. Step 33. If the source ^^ has been decoded during the current retransmission interval, i.e., ^^ ^^= 0 then the process goes to step 34 and otherwise to step 35. Step 34. The correctly decoded source ^^ is removed from the set ^^̂, ie, ^^̂ ← ^^̂ \ { ^^}. Step 35. End of the if of step 33. The process goes to step 36. Step 36. End of the while of step 30. If for the selected source ^^ the number ^^ ^^ is not zero then the process loops back to step 30 and otherwise the process goes to step 37. Step 37. End of the if of step 10. Step 38. End of the while of step 9. The process loops back as long as there are still sources to help in the game ^^̂ and otherwise ^^̂ = ∅ the process is finished, i.e., the transmission of the frame is interrupted, the process goes to the next frame. According to the example, according to the 1 er mode, at ^^ = 4 and ^^ ^^ ^^ = 2, the process loops back to step 9 with ^^̂ = {2}, ( ^^ ^^ ^^ = 2). Then at ^^ = 6, ^^ ^̅^,5 = {1} ≠ ∅, ^^̂ = ∅ but ^^ ^^ ^^= 0, ie, no other source can be decoded, this is the end of the frame transmission, the process moves on to the next frame. According to the example, according to the 2 e mode, at ^^ = 3 and ^^ ^^ ^^ = 3, the process loops back to step 9 with ^^̂ = {3}. Then at ^^ = 6, ^^ ^̅^,5 = {1} ≠ ∅, ^^̂ = ∅ and ^^ ^^ ^^ = 0, ie, no other source can be decoded, this is the end of the frame transmission, the process moves on to the next frame. According to the example, according to the 1 er mode and according to the 2 emode, at ^^ = 6 the transmission of the frame is interrupted, there is a decoding fault (outage event) of source 1. According to another embodiment, the selection of a source in step 9 can be done randomly among the sources of the set ^^̂. [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.

[0002] Appendix A Determination of the set ^^ of sources that can be helped: [Table 1] Calculation_ ^^_ ^^ ^^ ^^ ^^_ ^^ ^^ ^^ ^^ Appendix B Selection Strategy Algorithm: [Table 2] ^ ^ Start of the 1st transmission phase ie ^^ is initialized to 1, initialization of the remaining number ^^ ^^ ^^ of retransmission intervals to ^^ ^^ ^^ ^^ all ^^ ∈ ^^ ^̅^, ^^−1 Estimated number of retransmission intervals ^^ ^^to decode the source ^^ based on the CSI of the direct links only 3 . ^^̂ ← argmax ^^^^ ^^ ^^ ^^ ^^^^̂ includes the source set ^^∈ ^^( ^̅^ ^^, ^^−1 ) not correctly decoded st∑ ^^∈ ^^ ^^ ^^ ≤ ^^ ^^ ^^ leading to the highest spectral efficiency ^^^^ ^^ ^^ ^^ ^^ and satisfying the condition of the sum of the numbers of retransmission intervals ^^ ^^ less than the remaining time 4. ^^ ^^ ^^ ^^ ^^ ^^ ^^ ← 0 Initialization of a flag to zero ie no exchange of control requiring the transmission of all ^^ ^^ ^^ ^^ ^^̂ ← argmax ^^ ^^ ^^ ^^ ^^ ^^source sets not ^^∈ ^^( ^̅^ ^^, ^^−1 ) correctly decoded st∑ ^^∈ ^^ ^^ ^^ ≤ ^^ ^^ ^^ leading to the highest spectral efficiency ^^^^ ^^ ^^ ^^ ^^ and satisfying the condition of the number of retransmission intervals ^^ ^^less than the remaining time st = under constraint that End of if if ( ^^̂ = ^^ and ^^ ^^ ^^ ^^ ^^ ^^ = 0) then If ^^̂ is empty and no exchange of control for a reception of all the ^^ ^^ ^^ ^^ has not yet intervened then go to step 22 and otherwise to step 24 ^^ ^^ ^^ ^^ ^^ ^^_ ^^_ ^^ ^^ ^^ ^^_ ^^ ^^^^ Calculation of ^^̂ using a control exchange for a reception of all the ^^ ^^ ^^ ^^ and to determine the ^^ ^^ necessary and sufficient and communicate them to the nodes, in accordance with Annex A ^^ ^^ ^^ ^^ ^^ ^^ ^^ ← −1 Setting the flag to a negative value to indicate that an exchange of ^^ ^^ ^^ ^^ took place and thus prohibit more than one exchange of control requiring the transmission of all ^^ ^^ ^^ ^^End of if End of if End of if End of while e If a control exchange with transmission of all the CSIs has already taken place then go to step 29 otherwise go to step 37 The nodes successively select the The nodes help the sources sources of the ordered set ^^̂: ^^ ← 1 er element of ^^̂ ^^ ∈ ^^̂, ^^ ^^ times according to the order given by ^^̂ As long as ( ^^ ^^ > 0) do The source ^^ ^^ is helped ^^ ^^ times Nodes help the source ^^ Nodes that have correctly decoded ^^ transmit in parallel the same redundancy ^^ ← ^^ + 1, ^^ ^^ ← ^^ ^^ − 1 Increment of the current round ^^, decrement of ^^ ^^ since ^^ was helped once If ^^ was helped ^^ ^^ times at the end of the previous round then step 34 otherwise step 35 The nodes remove ^^ from the game ^^̂ sources to help at the end of ^^ ^^ the destination has correctly decoded the source ^^

Claims

CLAIMS 1. Communication method with transmission of a frame carrying at least one message intended for a telecommunications system comprising N 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 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 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 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 ^^ ^^ ^^ ^^ and determination of a set of sources ( ^^ ^^ ) not yet correctly decoded taking into account numbers (^^ ^^ ) of retransmission intervals so that the destination can decode these sources in the remaining time, the sources ( ^^ ^^) of the set ^^̂ being such that the sum of their number of retransmission intervals is less than or equal to the remaining time, called sources to be helped, the process implemented by the destination is such that it includes: - determination of the numbers ( ^^ ^^ ) of retransmission intervals based on knowledge of flow rates ( ^^ ^^ ) attributed to the sources ( ^^ ^^ ) and at least quality information of the different direct channels between the sources and the destination obtained from the transmissions occurring during the 1 ère phase, these numbers ( ^^ ^^ ) of determined intervals being at least sufficient for the destination to decode these sources, - reception of redundancies transmitted by the nodes having correct knowledge of the sources to be helped, during the numbers ( ^^ ^^) of determined intervals, so that the destination decodes these sources, and updating of the remaining time after each retransmission interval and, - provided that the set ^^̂ is empty and that there remains at least one source not correctly decoded and that the remaining time is non-zero, determination of the numbers ( ^^ ^^ ) of retransmission intervals based on knowledge of the flow rates ^^ ^^ attributed to these sources ( ^^ ^^ ) and a knowledge of a quality ( ^^ ^^ ^^ ^^ ) of the different direct transmission channels and the different indirect transmission channels, these numbers ( ^^ ^^ ) of determined intervals being necessary and sufficient for the destination to decode sources ^^ not yet correctly decoded, and update of the set ^^̂ taking into account the numbers ( ^^ ^^) of necessary and sufficient intervals.

2. Method according to claim 1, such that the sources ( ^^ ^^ ) of the set ^^̂ are those which maximize spectral efficiency.

3. Method according to one of claims 1 and 2, such that it comprises: - broadcasting to the ^^ nodes at each retransmission interval of a source identifier ( ^^ ^^ ) taken from the set ^^̂ and this, a number of times equal to the number ( ^^ ^^ ) of intervals determined for the identified source.

4. Method according to claim 3, such that the source identifier ( ^^ ^^ ) broadcast is randomly selected from the sources of the set ^^̂.

5. Method according to one of claims 1 to 4, further comprising a comparison between the numbers of retransmission intervals of the sources of the set ^^̂ so that the source identifier ( ^^ ^^) broadcast is selected taking into account an ordering of these numbers of retransmission intervals.

6. Method according to one of claims 1 and 2, such that it comprises: - broadcasting to the ^^ nodes in an ordered form of the set ^^̂ and the numbers of retransmission intervals of the sources of the set.

7. Method according to one of claims 1 to 6, such that it comprises: - broadcasting a request to the ^^ nodes indicating to them to transmit quality information of the channels between the nodes, called indirect channels, - receiving quality information ( ^^ ^^ ^^ ^^) indirect channels.

8. Method according to one of claims 1 to 7, such that, if the correct decoding of a source occurs before the end of the at least sufficient number of retransmission intervals then the method updates the set ^^̂.

9. Method according to one of claims 1 to 8, such that the determination of the at least sufficient numbers of retransmission intervals is further based on a transmission by the nodes at the beginning of the 2 nde phase of their set of correctly decoded sources.

10. Method according to one of claims 1 to 8, such as during an exchange of control with the nodes at the start of the 2 e phase, the destination sends its set of correctly decoded sources and the nodes send their set of correctly decoded sources and not yet correctly decoded by the destination and such that the determination of the at least sufficient numbers of retransmission intervals is further based on the transmission by the nodes of their set of correctly decoded sources and not yet correctly decoded by the destination.

11. Method according to one of claims 1 to 10 such that, if no source can be helped in the time remaining before the end of the 2 nde phase then the transmission of the frame is interrupted before the maximum number of retransmission intervals is used ( ^^^^ ^^ ^^ ^^< ^^ ^^ ^^ ^^ ).

12. Communication method with transmission of a frame carrying at least one message implemented by a telecommunications device intended for a telecommunications system comprising N 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 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 transmission channels between the nodes called indirect, with initialization of a remaining time during the 2 nde phase to ^^ ^^ ^^ ^^ and determination of a set of sources ( ^^ ^^ ) not yet correctly decoded taking into account numbers (^^ ^^ ) of retransmission intervals so that the destination can decode these sources in the remaining time, the sources ( ^^ ^^) of the set ^^̂ being such that the sum of their number of retransmission intervals is less than or equal to the remaining time, called sources to be helped, the method is such that it comprises: - transmission of a first redundancy of a message from the device during the 1 ère phase, - transmission during a retransmission interval of the 2 nde phase of a second redundancy of the message from a source of the set ^^̂ if the device has correct knowledge of this source, - conditional exchange of control with the destination during which the device transmits quality information of the indirect links of the device with the other nodes.

13. Telecommunication device (TAL) for transmitting a frame carrying at least one message, intended for a telecommunication system comprising N 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 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 ^^ ^^ ^^ ^^ and determination of a set ^^̂ of sources ( ^^ ^^ ) not yet correctly decoded taking into account numbers ( ^^ ^^ ) of retransmission intervals so that the destination can decode these sources in the remaining time, the sources ( ^^ ^^) of the set ^^̂ being such that the sum of their number of retransmission intervals is less than or equal to the remaining time, called sources to be helped, 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 ère phase, - the transmitter (EM) being further capable of transmitting during a retransmission interval of the 2 ndephase a second redundancy of the message from a source of the set ^^̂ if the device has correct knowledge of this source, - the transmitter (EM) and the receiver (RE) being capable of a conditional exchange of control with the destination during which the device transmits quality information of the indirect links of the device with the other nodes.

14. Base station (BS) intended for a telecommunication system comprising N 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 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 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 ^^ ^^ ^^ ^^ and determination of a set of sources ( ^^^^ ) not yet correctly decoded taking into account numbers (^^ ^^ ) of retransmission intervals for the destination to decode these sources in the remaining time, the sources ( ^^ ^^ ) of the set ^^̂ being such that the sum of their number of retransmission intervals is less than or equal to the remaining time, said sources to be helped, the base station corresponding to the destination comprises a decoder (DECOD IR), a transmitter (EM_BS), a receiver (RE_BS), a microprocessor (µP_BS) such that: - the receiver (RE_BS) is able to receive successively during the 1 ère phase the first ^^ redundancies ( ^^1, … , ^^ ^^ ) of ^^ messages from ^^ sources, - the microprocessor (µP_BS) is able to determine numbers ( ^^ ^^ ) of retransmission intervals based on knowledge of flow rates ( ^^ ^^ ) attributed to the sources ( ^^ ^^) and at least quality information of the different direct channels between the sources and the destination obtained from the transmissions occurring during the 1 ère phase, these numbers ( ^^ ^^ ) of determined intervals being at least sufficient for the destination to decode these sources, - the receiver (RE_BS) is furthermore able to receive redundancies transmitted by the nodes having correct knowledge of the sources to be helped, during the numbers ( ^^ ^^ ) of determined intervals, so that the base station (BS) decodes these sources, - the microprocessor (µP_BS) is further capable of updating the time remaining after each retransmission interval, - the microprocessor (µP_BS) is further capable of determining numbers ( ^^ ^^ ) of retransmission intervals, provided that the set ^^̂ is empty, that at least one source remains not correctly decoded and that the remaining time is not zero, based on knowledge of the flow rates ^^ ^^ attributed to these sources ( ^^ ^^ ) and a knowledge of a quality ( ^^ ^^ ^^ ^^ ) of the different direct transmission channels and the different indirect transmission channels, these numbers ( ^^ ^^ ) of determined intervals being necessary and sufficient for the destination to decode sources ^^ not yet correctly decoded and, to update the set ^^̂ taking into account the necessary and sufficient numbers of intervals.

15. Telecommunication 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 12.

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