Omamrc method and system with fdm transmission and multiple cooperations per sub-band

Abstract

The present invention relates to a method for transmitting messages intended for an OMAMRC telecommunication system having N nodes, including M sources (s i iϵ{1,.... M}), optionally L relays (r 1;..., r L ) and one destination. The transmission is FDM transmission in a band divided into B mutually orthogonal sub-bands. The method comprises: - transmitting M first redundancies of the M messages of the M sources during the 1st phase; - receiving, via the nodes, scheduling information (formula I) indicating, per sub-band, a selected source which is not yet correctly decoded by the destination and is referred to as the source to be helped, the scheduling information taking into account a constraint of a maximum emission power per node; and - transmitting, on a single sub-band during a single retransmission interval of the 2nd phase, active nodes having correct knowledge of a single selected source (s i ) of a single second redundancy of a single message of a single source, the transmission of one node over a plurality of sub-bands being under the constraint of a maximum emission power of the node.

Description

[0001] DESCRIPTION TITLE: OMAMRC method and system with FDM transmission and multiple sub-band cooperations 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 between at least two sources and a destination with relaying by the cooperation of at least one node which may be one of the sources or a relay distinct from a source. 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 of the transmission channel between the relays and the destination, noted OMAMRC ("Orthogonal Multiple-Access Multiple-Relay Channel" according to English terminology). Prior art An OMAMRC transmission system implementing a frequency division multiplexing type transmission known as FDM is known from application WO 2021 / 260308 published on December 30, 2021.The OMAMRC telecommunication system described in Figure 1 includes ^^ sources that belong to the source set ^^ = {1, … , ^^}, possibly ^^ relays that belong to the relay set ^^ = { ^^ + 1, … , ^^ + ^^}, ^^ ≥ 2, ^^ ≥ 0, and a destination ^^. Each source in the set ^^ communicates with the unique destination with the help of other sources (user cooperation) and cooperating relays. Nodes include relays and sources that can behave as a relay when they are not transmitting their own message. The nodes, ^^ sources and ^^ relays, access the transmission channel according to an orthogonal frequency multiple access scheme and operate in a full-duplex mode that allows them to listen to the transmissions of other nodes without interference. The channel band is divided into B sub-bands whose number is assumed to be greater than or equal to the number of sources: B ≥ ^^.Each sub-band associated with a time slot determines F channel utilizations (F resource elements). At each time slot, FDM transmission occurs on the band divided into B orthogonal sub-bands. A transmission cycle of a frame, illustrated by Figure 2, lasts 1 + ^^^^ ^^ ^^ ^^time slots with ^^^^ ^^ ^^ ^^≤ ^^. ^^ ^^ ^^ and ^^ ^^ ^^ ^^ the maximum number of time slots for a transmission cycle. At each time slot, none, one or more sub-bands are allocated to a node according to a partition and each sub-band is allocated at each time slot to at most one node. During the first time slot (first phase) all sources ^^1, … , ^^ ^^transmit, assuming that B ≥ ^^, respectively on one or more sub-bands allocated to each source. During the following intervals called retransmission (second phase), only the nodes selected from among the sources and the relays transmit and their transmission takes place on the sub-band(s) respectively allocated to them according to a partition determined for each current interval. Thus, at each of these intervals, the destination determines the vector ^^̂ ^^ ∈ ( ^^ ∪ ^^ ) ^^ of dimension B of the nodes to transmit at interval ^^ with the constraint that each sub-band is allocated to at most one node. The node selected for cooperative transmission transmits ^^ ^^ ^^after multi-user coding of the words it has correctly decoded. The selected node can transmit parities determined from the messages in its set of correctly decoded sources using joint network coding and channel coding (Joint Network Channel Coding in English terminology). The other nodes and the destination can improve their own decoding by exploiting the transmission of the selected node and update their set of correctly decoded sources accordingly. The destination thus controls the transmission of the nodes by using a return channel. This improves spectral efficiency and reliability by increasing the probability of decoding all sources by the destination.Main characteristics of the invention The present invention relates to a method for transmitting framed messages intended for a telecommunications system comprising a destination and ^^ nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, with orthogonal multiple access to the transmission channel between the ^^ nodes, with a maximum number of ^^ + ^^. ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase of ^^ time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^, the message from a source having been coded before transmission according to an incremental redundancy type coding which generates several redundancies, the transmission being of the frequency division multiplexing type on a band divided into ^^ ≥ 2 mutually orthogonal sub-bands, ^^ ≤ ^^ ^^. The method is such that it comprises: - a transmission of ^^ first redundancies of the ^^ messages from the ^^ sources during the 1 ère phase, - reception by the nodes of scheduling information indicating per sub-band a selected source not yet correctly decoded by the destination called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, - transmission on the same sub-band during the same retransmission interval of the 2 ndephase, of so-called active nodes having correct knowledge of the same selected source, of the same second redundancy of the same message from the same source, the transmission of a node on several sub-bands being subject to the constraint of a maximum transmission power of the node. The allocation of orthogonal sub-bands between the sources makes it possible to reduce the time required to transmit data since all the sources transmit their first redundancy on one or more sub-bands of one of the T time slots of the 1 ère phase. When the 1 ère phase includes a single time interval, T = 1, then all sources emit simultaneously during this same time interval which allows to have a 1 ère very fast phase. Such a method is therefore well suited for services requiring latency. The transmission of the same redundancy simultaneously during the same retransmission interval of the 2 ephase by all nodes having correct knowledge of the same source makes it possible to increase the power at reception at the destination and thus to greatly reduce the probability of a false alarm, i.e. incorrect decoding. This improvement allows for optimization of the throughput and / or makes it possible to reduce the transmission power of the sources for the same throughput. The nodes having correct knowledge of the same source are both the nodes having correctly decoded this same source and the source itself. These nodes other than the source are capable of cooperation by transmitting the same redundancy of this same source during a retransmission interval. The transmission of these nodes is said to be cooperative.In the case where the system includes relays other than the sources, a cooperative transmission is either a transmission by a relay or a transmission by a source capable of helping the destination to decode a source that it has not yet correctly decoded. A cooperative transmission is a transmission by a node that contains information relating to at least one message from another node. The transmission of a relay is, by nature, a cooperative transmission but also the transmission of a source (which is capable of cooperation) which includes in its transmission information relating to at least one message from another source. The cooperation of the nodes ensures an increase in the reliability of the transmissions. The transmission of a node on a sub-band depends on its transmission on other sub-bands. Indeed, a node has a transmission power P which must be distributed over all the sub-bands for which it is active.The power emitted by a node for a sub-band is a function of its power emitted on the other sub-bands for which it is active and the sum of the powers emitted per band cannot exceed P. The selection of the sources to be helped is implemented by a device called a scheduler which can correspond to the destination as well as to another device which has knowledge on the quality of the links within the system considered. The scheduler sends back to the nodes a scheduling information identifying the selected sources to be helped, i.e. selected among the sources that the destination has not yet correctly decoded. The scheduling information also includes the allocation of sub-bands for a retransmission by the nodes of a redundancy of the selected sources. For example, this information can be in the form of an integer Q: for B sub-bands, this integer Q can be determined as follows, Q = p0+ p1M + ⋯ + p.B−1 M B−1 where p i + 1 is the source identifier taking its value in the set {1,..,M} associated with the i ^^è ^^ ^^ + 1 band taking its value in the set {1, … , B}. The invention further relates to a method for transmitting messages put into frames implemented by a telecommunications device intended for a telecommunications system with ^^ nodes including ^^ sources and ^^ − ^^ relays and the device, ^^ ≥ ^^ ≥ 2, with orthogonal multiple access to the transmission channel between the ^^ nodes, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase of T time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^, the message from a source having been coded before transmission according to an incremental redundancy type coding which generates several redundancies, the transmission being of the frequency division multiplexing type on a band divided into B mutually orthogonal sub-bands, ^^ ≤ ^^ ^^. The method is such that it comprises: - simultaneous reception by the device during the 1 ère phase on at least ^^ sub-bands of ^^ first redundancies of the ^^ messages of the ^^ sources, - a transmission by the device of scheduling information indicating per sub-band a selected source not yet correctly decoded by the device called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, - a reception by the device, on the same sub-band of the same retransmission interval of the 2 ndephase, of the same second redundancy of the same selected source and coming from different nodes having correct knowledge of this same source. The invention further relates to a method for transmitting messages put into frames implemented by a telecommunications device intended for a telecommunications system with ^^ nodes including ^^ sources and ^^ − ^^ relays and a destination, ^^ ≥ ^^ ≥ 2, the device being one of the sources, 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 of ^^ time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^, the transmission being of the frequency division multiplexing type on a band divided into ^^ mutually orthogonal sub-bands, ^^ ≤ ^^ ^^. The method is such that it comprises: - coding of a message before transmission according to an incremental redundancy type coding which generates several redundancies, - transmission of a first redundancy of a message from the source during the 1 ère phase, - a reception of scheduling information indicating per sub-band a selected source not yet correctly decoded by the destination called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, - a transmission during a retransmission interval of the 2 ndephase of a second redundancy of the message of the selected sources on the respective sub-bands, for the sources for which the device has correct knowledge, the transmission of the device on several sub-bands being subject to a maximum transmission power constraint. The invention further relates to a telecommunication device for transmitting framed messages, intended for a telecommunication system comprising ^^ nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, and a destination ^^, 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 of ^^ time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^, the transmission being of the frequency division multiplexing type on a band divided into ^^ ≥ 2 mutually orthogonal sub-bands, ^^ ≤ ^^ ^^, the device which corresponds to one of the sources comprises at least one microprocessor, a memory, a transmission chain and a reception chain, the transmission chain comprises an encoder implementing an incremental redundancy type coding which generates several redundancies of the same message to be transmitted, and is such that: - the transmission chain is capable of transmitting a first redundancy of the message to be transmitted during the 1 ère phase, - the reception chain is able to receive scheduling information ^^̂ ^^of size ^^ indicating per sub-band a selected source not yet correctly decoded by the destination called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, - the transmission chain is furthermore capable of transmitting during a retransmission interval of the 2 ndephase a second redundancy of the message of the selected sources on the respective sub-bands, for the sources for which the device has correct knowledge, the transmission on several sub-bands being subject to a maximum transmission power constraint. The invention further relates to a telecommunication device for transmitting framed messages, intended for a telecommunication system comprising ^^ nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, and a destination ^^, 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 of ^^ time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^, the transmission being of the frequency division multiplexing type on a band divided into ^^ ≥ 2 sub-bands orthogonal to each other, ^^ ≤ ^^ ^^. The device which corresponds to one of the sources comprises at least one microprocessor, a memory, a transmission chain and a reception chain, and is such that: - the reception chain is capable of receiving simultaneously during the 1 ère phase on at least ^^ sub-bands of ^^ first redundancies of the ^^ messages of the ^^ sources, - the transmission chain is able to transmit scheduling information indicating per sub-band a selected source not yet correctly decoded by the device called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, - the reception chain is further able to receive on the same sub-band of the same retransmission interval of the 2 ndephase, the same second redundancy of the same selected source and coming from different nodes having correct knowledge of this same source. The invention further relates to a telecommunications system comprising a destination and ^^ nodes including ^^ sources and ^^ − ^^ relays, ^^ ≥ 2, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, adapted for implementing a transmission method according to one of the objects of the invention. According to one embodiment, the scheduling information is determined on the basis of mutual information per sub-band ^^, ^^^^ ^^ ^^ , ^^, ^^, of an equivalent channel between the nodes having correct knowledge of the same source to be helped and the destination. The criterion taken into account based on the mutual information makes it possible to tend towards maximizing spectral efficiency.The mutual information depends on the number of sub-bands for which a node is active, i.e. which transmits a redundancy for the same source or several sources for these different sub-bands. The selection of the sources to be helped therefore takes into account the fact that each of the nodes which transmits a redundancy of a selected source to be helped transmits on the allocated sub-bands and this for the different sources to be helped of which it has correct knowledge. The determination of the scheduling information is therefore subject to the constraint of a maximum transmission power per node. According to one embodiment, the transmission method further comprises: - transmission of the sets of sources correctly decoded by the nodes at the end of the transmission interval of the 1. èrephase. The information transmitted by the nodes allows the destination to select the sources to help it decode a maximum number of sources. According to one embodiment, the transmission method further comprises: - reception by the nodes of a set of sources correctly decoded by the destination among the sources received by the destination during the 1 ère phase, - transmission by the nodes of sets of sources correctly decoded by the nodes and not yet correctly decoded by the destination at the end of the 1 ère phase. According to this protocol, the destination sends back to the nodes its set of correctly decoded sources after receiving data transmitted during the 1 ertransmission interval. This feedback can occur via a control channel. According to a particularly simple embodiment, the destination feedbacks M bits which indicate for each of the M sources whether it is correctly decoded or not. If all the sources are correctly decoded by the destination, i.e. its set of correctly decoded sources contains the M sources, a new frame is transmitted. The information transmitted by the nodes allows the destination to more efficiently select the sources to help it decode a maximum number of sources. According to one embodiment, the scheduling information is obtained by comparing, between different possible scheduling information of sources to be helped per sub-band, the sum over the ^^ sub-bands of mutual information per sub-band ^^ of an equivalent channel between the nodes having correct knowledge of the same source to be helped and the destination.According to one embodiment, the scheduling information comprising ^^ components, the components are determined sequentially sub-band after sub-band and, for a given sub-band ^^, the component is obtained by determining between the different sources to be helped a maximum of a sum comprising on the one hand the sum over the sub-bands from 1 to ^^ − 1 of mutual information of an equivalent channel between the nodes having correct knowledge of the same source to be helped and the destination and on the other hand mutual information of an equivalent channel between the nodes having correct knowledge of the same source to be helped and the destination for the sub-band ^^. According to one embodiment, a transmission channel between a node taken from among the ^^ nodes and the destination for the sub-band ^^ is written in the form ℎ. ^^, ^^ ^^− ^^ ^^ ^^, ^^with ℎ ^^, ^^ an amplitude and ^^ ^^, ^^a phase factor, the process is such that, when each of the nodes having correct knowledge of the same selected source knows the phase ^^ ^^, ^^ of the transmission channel between this node ^^ and the destination, the transmission by each of these nodes of the same second redundancy of this same source is modulated by the phase factor corresponds to the conjugate ℎ ^ ∗ ^ , ^^ of the amplitude ℎ ^^, ^^ of the transmission channel between this node and the destination divided by its norm |ℎ ^^, ^^ |. According to one embodiment, a transmission channel between a node taken from among the ^^ nodes and the destination for the sub-band ^^ is written in the form ℎ ^^, ^^ ^^− ^^ ^^ ^^, ^^with ℎ ^^, ^^ an amplitude and ^^ ^^, ^^a phase factor, the nodes having correct knowledge of the same source selected for the sub-band ^^ being grouped into a first and a second group of nodes such that each of the nodes of the first group knows the phase ^^ ^^, ^^ of the transmission channel between this node and the destination for the sub-band ^^ and each of the nodes of the second group does not know the phase ^^ ^^, ^^ of the transmission channel between this node and the destination for the sub-band ^^, the method is such that the transmission by a node a of the first group of the same second redundancy of a source is modulated by the phase factor ^^− ^^ ^^ ^^, ^^= corresponds to the conjugate ℎ ^ ∗ ^ , ^^ of the amplitude ℎ ^^, ^^of the transmission channel between this node ^^ and the destination divided by its norm and such that the transmission by a node a of the second group of the same second redundancy of the source occurs without phase correction. According to one embodiment, for the same source, the first redundancy and the second redundancy are different. The different modes can be combined with each other to form other modes. The devices and system according to the invention are adapted to implement the different embodiments of the method according to the invention. 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 transmission method when these applications are executed by processors.The invention further relates to configured memories comprising instruction codes corresponding respectively to each of the specific applications. The memory can be incorporated into any entity or device capable of storing the program. The memory can 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 can be downloaded from a server accessible on an Internet-type network. The optional characteristics presented above in the context of the transmission method can possibly be applied 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 an OMAMRC (Orthogonal Multiple Access Multiple Relays Channel) system according to the prior art, [Fig 2] figure 2 is a diagram of a transmission cycle of a frame according to the prior art, [Fig 3] figure 3 is a diagram of a transmission cycle of a frame according to the invention, [Fig 4] figure 4 is a diagram of the protocol for the exchange of information between the destination and the nodes, sources and relays, according to an embodiment of the invention, [Fig 5] figure 5 is a diagram of the simplified structure of a telecommunications device according to the invention.Description of particular embodiments of the invention An OMAMRC system is illustrated in Figure 1. In the context of the invention, such a system comprises ^^ nodes including ^^ sources which belong to the set of sources ^^ = {1, … , ^^} and ^^ = ^^ − ^^ relays which belong to the set of relays ^^ = { ^^ + 1, … , ^^ + ^^} and a destination ^^. ^^ ≥ 0. ^^ ≥ ^^ ≥ 2. When ^^ = ^^, the system comprises only two sources and the destination. When ^^ > ^^, the system comprises at least two sources and at least one relay and the destination. A diagram of a transmission cycle of a frame according to the invention is illustrated in Figure 3. 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 the transmission duration.Each source in the set ^^ communicates with the single destination with the help of other sources (user cooperation in English terminology) and cooperating relays. Nodes include relays and sources that can behave like a relay when they are not transmitting their own message. The ^^ nodes, ^^ sources and ^^ relays, access the transmission channel according to an orthogonal frequency multiple access scheme and operate in a full-duplex mode that allows them to listen to the transmissions of other nodes without interference. The channel band is divided into B sub-bands. Each sub-band associated with a time slot ^^ determines F channel utilizations (F resource elements in English terminology). In the case of transmission with OFDM modulation, a sub-band can include, for example, as many sub-carriers as an OFDM symbol.Each source transmits its framed data to the destination with the help of other sources and relays. A frame occupies time slots during the transmission of ^^ messages from the respective ^^ sources. A transmission cycle, i.e. the transmission of a frame, illustrated in Figure 3, takes place during ^^ + ^^^^ ^^ ^^ ^^ time slots. ^^ ≥ 1 is the number of transmission slots of the 1. ère phase with one or more channel sub-bands allocated for each source ^^. ^^^^ ^^ ^^ ^^the number of retransmission intervals of the 2 e phase with one or more channel subbands allocated to assist each selected source ^^, ^^^^ ^^ ^^ ^^≤ ^^ ^^ ^^ ^^ and ^^ ^^ ^^ ^^the maximum number of retransmission intervals. The determination of the sources to be assisted and the allocation of sub-bands are implemented by a scheduler. The mode described corresponds to the case where the scheduler is hosted by the destination. The number of channel uses is assumed to be identical for each transmission time interval and each retransmission time interval: B × F. ^^ ^^ is a variable representing the initial flow rate of the source ^^ which can take its values ​​in the finite set { ^̅^1, … , ^̅^^^ ^^ ^^ ^^}. A transmission interval has the capacity ^^ 1, ^^ channel usages for each source ^^. During the first phase each source ^^ ∈ ^^ emits a message during ^^ 1, ^^ channel uses, ^^ ∈ {1, … , ^^ 1, ^^}, the number ^^ 1, ^^of channel uses dependent on the source s. A retransmission interval has a capacity of ^^2 channel uses for each source ^^. ^^ ^^ is a variable representing the ratio ^^2 / ^^ 1, ^^ which can take its values ​​from a finite set The initial flow rates of the sources are generally determined by the destination during an initial phase which precedes any transmission phase. The increase in the initial flow rates ^̅^ ^^ and reports is performed via very limited bit rate control channels. The initial phase occurs at most before each transmission phase of a frame. When ^^ = 1 then the number of sub-bands is assumed to be greater than or equal to the number of sources: B ≥ ^^. When ^^ > 1 then the number of sub-bands times the number of transmission intervals is assumed to be greater than or equal to the number of sources: BT ≥ ^^. An embodiment of the protocol for exchanges between the nodes and the destination is illustrated in Figure 4. During the first phase, the first ^^ time intervals, all sources transmit respectively on one or more sub-bands allocated to each source. The allocation of one or more sub-bands to a source is defined in a partition that can be determined by the destination and communicated to the sources by the destination via a control channel.When ^^ = 1 all sources transmit simultaneously respectively on one or more sub-bands allocated to each source. When ^^ > 1 all sources transmit during one or more of the transmission intervals on one or more sub-bands allocated to each source. Some sources may transmit simultaneously on different sub-bands. At each retransmission time interval, none, one or more sub-bands are allocated for a source to be helped. The scheduler, the destination according to the described mode, transmits to the nodes a scheduling information which can have the form of a vector. The scheduling information ^^̂. ^^determines a partition of the sources to be helped for the different sub-bands. Thus, the partitions can be different between each of the retransmission intervals. Only nodes having correct knowledge of the same source of the partition simultaneously transmit the same redundancy of this same source on one or more of the same sub-bands. These nodes include the nodes having correctly decoded this same source and the source itself, these nodes are said to be cooperative.To simplify the description, the following assumptions are made subsequently on the OMAMRC system: - the sources, the relays are equipped with a single transmitting antenna; - the sources, the relays, and the destination are equipped with a single receiving antenna; - 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 maximum power ^^; - use is made of a CRC code assumed to be included in the ^^. ^^ bits of information from each source ^^ to determine whether a message 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 ^^ ^^ ^^ ^^ ^^ ^^ ≥ 1 are system parameters; - the instantaneous quality of the direct channel / link in reception (CSIR Channel State Information at Receiver) is available at the destination, sources and relays; - the returns are error-free (no error on the control signals). The following notations are used: • a node which intervenes during the 2 e phase is noted with ^^ ∈ { 1, … , ^^ + ^^ } , if ^^ ≤ ^^ node i is a source i denoted ^^ ^^ in figure 1, ^^ ∈ {1, … , ^^}, otherwise ^^ > ^^, ^^ ∈ { ^^ + 1, … , ^^ + ^^ } and the node is a relay denoted ^^1,…, ^^ ^^ in figure 1, • ^^ ^^ is the scheduling information. It contains the sources to be assisted for the retransmission interval ^^ during the second phase. When it has the form of a vector, ^^ ^^ ∈ ( ^^ ) ^^, the scheduling information is of dimension B. The ^^ ^^ℎ element ^^ ^^, ^^ of the vector ^^ ^^ indicate the source to help for this ^^ ^^ℎ sub-band during this time interval ^^, ^^ ∈ {1, … , ^^ } . The order in the vector ^^ ^^ corresponds to the order of the sub-bands. The ordering information can take other forms, this information can for example be in the form of an integer ^^. For B sub-bands, this integer ^^ can be determined as follows, ^^ = where ^^ ^^ + 1 is the source identifier taking its value in the set {1,..,M} associated with the ^^ è ^^ ^^ + 1 band taking its value in the set {1, … , ^^}. For example, an ordered set of three elements belonging to {0,..,9} for example (1,2,3) can be written (there is a bijection) in the form of an integer ^^ = 321 or 1 + 2 × 10 + 3 × 10 2in base 10. An ordered set of three elements belonging to {0,..,M-1} for example ( ^^1, ^^2, ^^3) can be written (there is a bijection) in base M in the form of an integer ^^ = p1+ p2× M + p3× M 2 . So the data of an integer base M makes it possible to identify an ntuple whose elements are integers of a set {0,…,M- 1}. The rest of the description considers that the ordering information has the form of a vector. • ^^ ^^, ^^ is the average signal-to-noise ratio (SNR) which takes into account the effects of channel attenuation (path-loss according to English terminology) and masking (shadowing according to English terminology) between the node ^^ (source or relay) and the node ^^ (source, relay or destination). • ℎ ^^, ^^ is the channel fading gain between node ^^ (source or relay) and node ^^ (source, relay or destination) which follows a circularly symmetric complex Gaussian distribution with zero mean and variance ^^ ^^, ^^, the gains are independent of each other. • ^^ ^^ ∈ ({0, … , ^^}) M+L is the vector of dimension ^^ + ^^ of the number of sub-bands for which a node is active, or not, to help one or more sources which varies between 0 (the node is not active) and B (the node is active for all sub-bands) for the retransmission interval (time slot) ^^ during the second phase. The ^^ ^^ℎ element ^^ ^^, ^^ of the vector ^^ ^^ denotes the number of sub-bands for which node i, source or relay, is active at the retransmission interval (time slot) t, ^^ ∈ {1, … , ^^ + ^^}, • ^^^^ ^^ ^^ ^^is the number of retransmission time slots ie during the second phase which leads to zero faults for all sources (the individual outage event of each of the sources is zero ie ^^ ^^, ^^ = 0): Example of implementation of the invention During the first phase, each source s ∈ ^^ transmits after coding a message ^^ ^^ comprising ^^ ^^ bits of information ^^ ^^ ∈ ^^ ^ 2 ^ ^^ , ^^2 being the two-element Galois field. The message ^^ ^^ includes a CRC type code which allows the integrity of the message to be verified ^^ ^^ . The message ^^ ^^is encoded according to the initial MCS. Since the initial MCSs may be different between sources, the lengths of the encoded messages may be different between sources. The encoding uses an incremental redundancy code. The resulting codeword is segmented into redundancy blocks. The incremental redundancy code may 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 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 convolutional code (RCPCC), rate-compatible LDPC (RCLDPC), rate-compatible low-density parity check code (LDPC). According to the implementation example described and illustrated in Figure 4, the parameter ^^ = 1. Thus, during the first phase, the ^^ sources simultaneously transmit a 1. ère redundancy of their respective messages … , ^^ ^^1 ^^ ^^during the transmission interval on respectively the allocated sub-bands with respectively modulation and coding schemes determined from the values ​​of the initial bit rates of the sources. Each transmitted message corresponding to a source ^^ ∈ ^^, a correctly decoded message is assimilated to the corresponding source by abuse of notation. Whether during the first phase or the second phase, when a node, in particular a source transmits, the destination and the other nodes listen. Each full-duplex node can transmit on one or more sub-bands and simultaneously listen to all the other nodes transmitting on another sub-band. The destination, the sources and the relays attempt to decode the received messages at the end of a time interval. The success of the decoding at each node is decided using the CRC. The destination and the nodes thus determine their set of correctly decoded sources.According to the embodiment, during the second phase, at the time interval (round according to English terminology) t, the destination ^^ transmits its set of sources correctly decoded at the end of the previous time interval ^^. ^^, ^^−1 using for example a feedback broadcast control channel, ^^ = {1, … , ^^^^ ^^ ^^ ^^}. This feedback can consist of a vector of ^^ bits. If the decoding of all sources by the destination is correct ^^ ^^, ^^−1 = ^^, the current cycle is stopped, a new cycle can start. A transmission cycle of a new frame begins with the erasure of the memories of the relays and the destination and with the transmission by the sources of new messages. The number of time intervals (rounds) used during the second phase ^^^^ ^^ ^^ ^^= {1, … , ^^ ^^ ^^ ^^} depends on the decoding success at the destination. The nodes, both sources and relays, compare the set ^^ ^^, ^^−1from sources correctly decoded by the destination to their set of correctly decoded sources ^^ ^^, ^^−1 and deduce the game of sources for which they can help the destination: = ^^ ^^, ^^−1 ∩ ^^ ^̅^, ^^−1 . By convention, we note ^^ c,t ⊆ ^^ the set of messages (or sources) correctly decoded by the node ^^ ∈ ^^ ∪ ℜ ∪ { d } at the end of time interval t (round t), t ∈ { 0, … , ^^ ^^ ^^ ^^ } including for a source its own message. The end of the time interval (round) t = 0 corresponds to the end of the first phase. The number of time intervals (time-slots) used during the second phase ^^^^ ^^ ^^ ^^= { 1, … , ^^ ^^ ^^ ^^ } depends on the decoding success at the destination. If a node's set includes at least one source not included in the set ^^ ^^, ^^−1of the destination, the node informs the destination using for example a dedicated unicast control channel. The information transmitted by a node can consist of its set of sources of which it has correct knowledge, i.e. which it has correctly decoded, including for a source the knowledge of its own message, or, as illustrated by Figure 4, in sources of which it has correct knowledge and which the destination has not yet correctly decoded, During this second phase, the destination follows a certain strategy to decide which source(s) to help. The destination informs the nodes of this selection by transmitting the vector ^^̂ ^^ sources to help for each sub-band using for example a return broadcast control channel. The vector ^^̂ ^^defines a partition of the sources to be helped on the respective sub-bands. The destination thus controls the transmission of the nodes using a return channel. This improves spectral efficiency and reliability by increasing the probability of decoding all sources by the destination. For each source in the partition, all nodes that have correct knowledge of this source transmit at interval ^^ the same redundancy of this same source on one or more of the same sub-bands. The set of redundancies transmitted at interval ^^ is denoted ^^ ^^ ^^ ^^̂ ^^. Nodes and the destination can improve their own decoding by exploiting the retransmission of a redundancy from a source on one or more sub-bands on which they do not transmit and update accordingly their set of correctly decoded sources. Selection strategies The selection of the source to be helped for each sub-band depends on the channel state between the different nodes that transmit the same redundancy and the destination. The state of a channel can be evaluated by the mutual information which is a function of the SNR of this channel / link. By exploiting reference signals (pilot symbols, SRS signals of 3GPP LTE, etc.), the destination can determine the gains (CSI: Channel State Information according to the English terminology) of the direct links per sub-band ^^ ∈ : ^^^^ ^^ ^^, ^^= {ℎ ^^1, ^^ , … , ℎ^^ ^^ , ^^, ℎ ^^1, ^^, … , ℎ^^ ^^ , ^^}, i.e., source-to-destination and relay-to-destination links, and can therefore derive the average SNRs of these links. The channel statistics of each link are assumed to follow a centered circular complex Gaussian distribution, and the statistics are independent between links. It is therefore sufficient to consider only the average SNR as a measure of the statistics of a link. The signal received by the destination at retransmission interval ^^ on sub-band ^^ can be written as: ^^ ^^,t, ^^ = ℎ^^ ^^, ^^ ^^,t, ^^^^ ^^ ^^ + ^^ ^^, ^^ (2) With: ^^ ^^ the set of nodes having correct knowledge of the source ^^ ^^ at the end of the time interval ^^ − 1, ℎ^^ ^^, ^^ ^^, ^^, ^^the equivalent channel resulting from the transmission during the retransmission interval ^^ on the sub-band ^^ by all the nodes belonging to ^^ ^^ of the same RVX redundancy version ^^ ^^ and ^^^^, ^^ a complex Gaussian random variable with circular symmetry such that ^^ ^^, ^^ ~ ^^ ^^ ( 0, 2σ 2) Transmission during the 2 nd phase, by the nodes having correct knowledge of a source to be helped selected and identified in the vector ^^̂ ^^ , can take place according to several embodiments. According to a first embodiment, none of the nodes ^^ ∈ ^^ ^^ , ^^ ^^ being the set of nodes having correct knowledge of the source ^^ (i.e. of the message ^^ ^^ emitted by the source ^^ ^^ ) at the end of slot ^^ − 1, does not know the phase ^^ ^^, ^^ of the transmission channel ℎ ^^, ^^ on the sub-band ^^ linking it to the destination ^^. The equivalent channel for a source ^^ ^^ to help on the sub-band ^^ can then be expressed in the form: This mode corresponds to a combination that is not coherent at reception. According to a second mode, each of the nodes ^^ ∈ ^^^^ , ^^ ^^ being the set of nodes having correct knowledge of the source ^^ (i.e. of the message ^^ ^^ emitted by the source ^^ ^^ ) at the end of slot ^^ − 1, knows phase ^^ ^^, ^^ of the transmission channel ℎ ^^, ^^ on the sub-band ^^ linking it to the destination ^^. Upon receipt of the vector ^^̂ ^^ from sources ^^ ^^ to help, each node ^^ ∈ ^^ ^^ transmits at the retransmission interval ^^ on the same sub-band ^^ the same message redundancy ^^ ^^ emitted by the source ^^ ^^ modulated by a phase factor ^^− ^^ ^^ ^^, ^^= ℎ ^ ∗ ^ , ^^ / |ℎ ^^, ^^ | with ^^ 2 = −1 and where corresponds to the conjugate ℎ ^ ∗ ^ , ^^ of the transmission channel ℎ ^^, ^^ linking node ^^ to destination ^^ divided by its norm |ℎ ^^, ^^ | so that all these redundancies transmitted by the nodes ^^ ∈ ^^ ^^are received at the same time by the destination in a coherent manner. Thus, the equivalent channel for the aided source ^^ ^^ on the sub-band ^^ is expressed in the form: Such a transmission mode, called "equal gain combining" in English terminology, makes it possible to obtain, on the destination side, a coherent combination of all the signals emitted by the nodes having correct knowledge of the message emitted by the source. i selected. According to a third mode, the set ^^ ^^ nodes having correct knowledge of the source ^^ at the end of the slot ^^ − 1 decomposes into two groups of nodes, ^^ ^^ and ^^ ^^ . Each node of the first group of nodes, ^^ ∈ ^^ ^^ , knows the phase ^^ ^^, ^^ of the transmission channel ℎ ^^, ^^ on the sub-band ^^ linking it to the destination ^^. Each node of the second group, doesn't know the phase ^^ ^^, ^^of the transmission channel on the sub-band ^^ linking it to the destination ^^. Upon receipt of the vector ^^̂ ^^ of sources to help, each node of the first group, ^^ ∈ ^^ ^^ , transmits at the retransmission interval ^^ on the same sub-band ^^ the same message redundancy ^^ ^^ emitted by the source ^^ ^^ modulated by a phase factor ^^− ^^ ^^ ^^, ^^= ℎ ^ ∗ ^ , ^^ / |ℎ ^^, ^^ | with ^^ 2 = −1 and where ℎ ^ ∗ ^, ^^ / |ℎ ^^, ^^ | corresponds to the conjugate ℎ ^ ∗ ^, ^^ of the transmission channel ℎ ^^, ^^ linking node ^^ to destination ^^ divided by its norm |ℎ ^^, ^^ | so that all these redundancies transmitted by the nodes of the first group are received at the same time by the destination in a coherent manner. And each node belonging to the second group ^^ ^^transmits at the retransmission interval ^^ on the same sub-band ^^ the same message redundancy ^^ ^^ emitted by the source ^^ ^^ without phase modulation. This mode can occur, for example, during a transient period during which the destination has not yet been able to determine the information relating to the phase factors e −jφa,b for all nodes. Over time, the destination can provide such information to all nodes in the system, further improving the transmission quality. In this mode, the equivalent channel can be expressed as: For all these modes, the signal-to-noise ratio associated with the equivalent channel is ^^ ^^ ^^( ^^ ^^ , ^^, ^^) = 2 assuming that ^^ {| ^^ ^^ ^^ |} = 1. The mutual information ^^^^ ^^, ^^, ^^associated with the equivalent channel is a function of the SNR, i.e. The transmission power of a node is shared in frequency between the different sub-bands for which the node is active for the same retransmission interval and cannot exceed the maximum power ^^. Therefore, the mutual information associated with the equivalent channel, ^^^^ ^^, ^^, ^^with ^^ ∈ {1, … , ^^}, ^^ ∈ {1, … , ^^}, and ^^ ∈ {1, … , ^^ ^^ ^^ ^^} depends on the number of sub-bands ^^ ^^, ^^ for which the node ^^ which belongs to the set ^^ ^^is active, i.e. transmits a redundancy for the same source or several sources for these different sub-bands. The selection of the sources to be helped takes into account the fact that each of the nodes which transmits a redundancy of a selected source to be helped transmits on the allocated sub-bands and this for the different sources to be helped of which it has correct knowledge. The selection of the sources is therefore under the constraint that each node which transmits has its transmission power distributed on the sub-bands for which it is active. According to a first mode of selection implemented in algorithm 1 of the appendix, at a retransmission interval ^^, the scheduler considers all the possible vectors, ^^ ^^ ∈ {1, … , ^^} ^^ , of sources of size ^^ taken from the sources to be helped ie, these sources are taken from the sources not yet decoded by the destination The selected vector is the one that allows to achieve the greatest mutual information knowing that the mutual information depends for each sub-band on the equivalent channel between the different nodes that transmit the same redundancy and the destination. The optimal vector of sources to help for the ^^ sub-bands, ^^̂ ^^ ∈ {1, … , ^^} ^^ among these different possible vectors is the following: ^^̂ ^^ ∈ argmax ^^∈{ ^̅^ ^^, ^^−1} ^^ Thus, the optimal vector ^^̂ ^^ for the retransmission interval ^^ includes the set of sources for which the sum over the ^^ sub-bands of the mutual information, ^^^^ ^^ ^^ , ^^, ^^, is the highest, each mutual information being associated with the equivalent transmission channel established between each of the nodes having error-free knowledge of the same source to be helped, destination. In other words, the destination selects the vector of sources to be helped for which the average mutual information "harvested" is the largest. This average mutual information is a sum depending on the equivalent SNR per sub-band, so the optimization must be joint on all sub-bands because the power emitted by a node must be shared between the sub-bands for which the node is active. According to a second selection mode implemented in algorithm 2 of the appendix, the destination sequentially selects the sources to be helped, sub-band after sub-band. Thus, at a retransmission interval ^^, for each of the sub-bands ^^ taken successively, the destination selects, among the sources to be helped, the source noted ^^̂ ^^, ^^ such that: ^^̂ ^^, ^ ∈ argmax {∑ ^^−1 ^ ^=1 ^^∈ ^̅^ ^^, ^^−1 The selected source ^^̂ ^^, ^^for the sub-band ^^ is that, among the sources to be helped, ^^ ∈ ^^ ^̅^, ^^−1 , which maximizes the sum including on the one hand the sum over the sub-bands from 1 to ^^ − 1 of the mutual information of the equivalent channel for each of these sub-bands, ∑ ^^−1 ^ ^=1 ^^^^ ^^̂ ^^, ^^ , ^^, ^^, and on the other hand the mutual information of the equivalent channel of the sub-band ^^, ^^^^ ^^, ^^, ^^. This 2 e selection mode is less complex than 1 er mode. Each selection mode is of course combined with the different transmission modes detailed above. Figure 5 is a diagram of the simplified structure of an embodiment of a DIS telecommunications device according to an embodiment of the invention. This DIS device is intended for an OMAMRC telecommunications system comprising ^^ nodes including ^^ sources ^^ ^^ ^^ ^^ { 1, … , ^^ }and ^^ − ^^ relay, ^^ ≥ ^^ ≥ 2, and a destination ^^. Access to the transmission channel between the nodes and the destination is of orthogonal multiple type. The protocol of 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 DIS device comprises at least one microprocessor µP whose operation is controlled by the execution of a program Pg whose instructions allow the implementation of a transmission method according to the invention, a memory MEM, a transmission chain EM and a reception chain RE which are connected to each other through a bus Bu. Of course, the constituent elements of the DIS device can be connected by means of a connection other than a bus. The microprocessor µP controls the operations of the DIS device. The storage unit MEM stores at least the program Pg for the implementation of 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 carried out by the microprocessor µP, intermediate data of calculations carried out 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 (CPU) that executes a program stored in a memory thereof. The memory MEM may be formed by any suitable means capable of storing the program Pg or programs and data in a computer-readable manner. Examples of memory MEM include computer-readable non-transitory storage media such as semiconductor memory devices, and magnetic, optical, or magneto-optical recording media loaded into a read-write unit.At initialization, the code instructions of the program Pg are for example loaded into a buffer memory before being executed by the processor μP. The microprocessor μP controls the various components of the device DIS. Thus, by executing the instructions, the microprocessor μP allows the device DIS to implement the transmission method according to an embodiment of the invention. According to an embodiment of the invention, the device DIS is one of the ^^ sources ^^. ^^ ^^ ^^ { 1, … , ^^ }. According to this mode, the DIS device can be a mobile terminal. According to this mode, the DIS device is capable of transmitting a framed message. Of course, the device can transmit several messages successively. The transmission method implemented by the device is such that it comprises an incremental redundancy type coding implemented by a coder of the EM transmission chain which generates several redundancies of the same message to be transmitted. The transmission by the device is of the frequency division multiplexing type on a band divided into B mutually orthogonal sub-bands, M ≤ BT. The transmission method by the DIS device further comprises: - a transmission of a first redundancy of the message to be transmitted during the 1 ère phase, implemented by the EM transmission chain, - a reception of scheduling information ^^̂ ^^indicating by sub-band a selected source not yet correctly decoded by the destination called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, implemented by the reception chain RE, - a transmission during a retransmission interval of the 2 ndephase of a second redundancy of the message of the selected sources on the respective sub-bands, for the sources for which the device has correct knowledge, implemented by the transmission chain EM. By executing the instructions, the microprocessor µP checks that the transmission of the DIS device on several sub-bands does not exceed the maximum transmission power constraint of this device. According to an embodiment of the invention, the DIS device corresponds to the destination ^^ of the OMAMRC telecommunication system. According to this mode, the device can be a base station. This device is then intended for an OMAMRC telecommunication system comprising ^^ nodes and this device which plays the role of the destination ^^. Thus by executing the instructions, the microprocessor µP allows the implementation by the device ^^ ^^ ^^ of the transmission method which comprises: - simultaneous reception during the 1 èrephase on at least ^^ sub-bands of ^^ first redundancies of the ^^ messages of the ^^ sources, implemented by the reception chain RE, - a transmission of scheduling information ^^̂ ^^ indicating by sub-band a selected source not yet correctly decoded by the device called source to be assisted, the scheduling information taking into account a constraint of a maximum transmission power per node, implemented by the EM transmission chain, - a reception, on the same sub-band of the same retransmission interval of the 2 nde phase, of the same second redundancy of the same source ^^ ^^ selected and coming from different nodes having correct knowledge of this same source, implemented by the RE reception chain.

[0002] Appendix Algorithm 1 of Selection Strategy 1. ^^ ← 1 Initialize the index of the current retransmission interval 2. While ( ^^ ^̅^, ^^−1 ≠ ^^ and ^^ ≤ ^^ ^^ ^^ ^^) do The transmission of a frame is completed when all sources are correctly decoded or when the current time indicator reaches ^^ ^^ ^^ ^^ 3. ^^ ^^, ^^−1 The destination ^^ transmits to the nodes its set of correctly decoded sources 4. ^^ ^ ′ ^, ^^−1 = ∩ ^^ ^̅^, ^^−1 The nodes ^^ transmit to the destination their set of correctly decoded sources and not yet correctly decoded by the destination 5. The destination determines the vector argmax ^^∈{ ^̅^ ^^, ^^−1} ^^ optimal ^^̂ ^^ sources to help 6. ^^̂ ^^ The destination ^^ transmits to the nodes the optimal vector ^^̂ ^^ 7 ^^ ^^ ^^^^̂ ^^, ^^Nodes having correct knowledge of the source ^^̂ ^^, ^^transmit in parallel the same redundancy ^^ ^^ ^^^^̂ ^^, ^^on the same sub-band ^^ during the same interval ^^ 8. ^^ ← ^^ + 1 Increment of the index of the current retransmission interval 9. End of while Algorithm 2 of selection strategy Initialization of the index of the current retransmission interval 2 . Tant que ≠ ^^ and ^^ ≤ ^^ ^^ ^^ ^^) doThe transmission of a frame is completed when all sources are correctly decoded or when the current time indicator reaches ^^ ^^ ^^ ^^ ^^̂ ^^ The destination ^^ transmits to the nodes the optimal vector ^^̂ ^^ Nodes having correct knowledge of the source ^^̂ ^^, ^^ transmit in parallel the same redundancy on the same sub-band ^^ during the same interval ^^ ^^ ← ^^ + 1 Increment of the index of the current retransmission interval by while

Claims

CLAIMS 1. Method for transmitting framed messages intended for a telecommunications system comprising a destination ( ^^) and ^^ nodes of which ^^ sources ( ^^ ^^ ^^ ^^ { 1, … , ^^ } ) and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, with orthogonal multiple access to the transmission channel between the ^^ nodes, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase of ^^ time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^, the message from a source having been coded before transmission according to an incremental redundancy type coding which generates several redundancies, the transmission being of the frequency division multiplexing type on a band divided into ^^ ≥ 2 mutually orthogonal sub-bands, ^^ ≤ ^^ ^^, such that the method comprises: - transmission of ^^ first redundancies of the ^^ messages from the ^^ sources during the 1 ère phase and characterized in that the method further comprises: - reception by the nodes of scheduling information ( ^^̂ ^^ ) indicating per sub-band a selected source not yet correctly decoded by the destination called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, - transmission on the same sub-band during the same retransmission interval of the 2 nde phase, of so-called active nodes having correct knowledge of the same source ( ^^ ^^) selected, of the same second redundancy of the same message from the same source, the transmission of a node on several sub-bands being subject to the constraint of a maximum transmission power of the node.

2. Transmission method according to claim 1, further comprising: - transmission of the sets of sources correctly decoded by the nodes at the end of the transmission interval of the 1 ère phase.

3. Transmission method according to claim 1 further comprising: - reception by the nodes of a set of sources correctly decoded by the destination among the sources received by the destination during the 1 ère phase, - transmission by the nodes of sets of sources correctly decoded by the nodes and not yet correctly decoded by the destination at the end of the 1 ère phase.

4. Transmission method according to one of claims 1 to 3, according to which the scheduling information ( ^^̂ ^^) is obtained by comparing, between different possible ordering information of sources to be helped by sub-band, the sum over the ^^ sub- bands of mutual information by sub-band ^^ of an equivalent channel between the nodes having correct knowledge of the same source to be helped and the destination.

5. Transmission method according to one of claims 1 to 4 according to which, the scheduling information ( ^^̂ ^^) comprising ^^ components, the components are determined sequentially sub-band after sub-band and, for a given sub-band ^^, the component is obtained by determining between the different sources to be helped a maximum of a sum comprising on the one hand the sum over the sub-bands from 1 to ^^ − 1 of mutual information of an equivalent channel between the nodes having correct knowledge of the same source to be helped and the destination and on the other hand mutual information of an equivalent channel between the nodes having correct knowledge of the same source to be helped and the destination for the sub-band ^^.

6. Transmission method according to one of claims 1 to 5, a transmission channel between a node taken from among the ^^ nodes and the destination ( ^^) for the sub-band ^^ being written in the form ℎ ^^, ^^ ^^− ^^ ^^ ^^, ^^with ℎ ^^, ^^ an amplitude and ^^ ^^, ^^a phase factor, the process is such that, when each of the nodes having correct knowledge of the same source ( ^^ ^^ ) selected knows the phase ^^ ^^, ^^ of the transmission channel between this node ^^ and the destination ( ^^), the transmission by each of these nodes of the same second redundancy of this same source ( ^^ ^^ ) is modulated by the phase factor = ℎ ^ ∗ ^, ^^ / |ℎ ^^, ^^ | with ^^ 2 = −1 and where ℎ ^ ∗ ^, ^^ / |ℎ ^^, ^^ | corresponds to the conjugate ℎ ^ ∗ ^, ^^ of the amplitude ℎ ^^, ^^ of the transmission channel between this node and the destination ( ^^) divided by its norm |ℎ ^^, ^^ |.

7. Transmission method according to one of claims 1 to 5, a transmission channel between a node taken from among the ^^ nodes and the destination (^^) for the sub-band ^^ being written in the form ℎ ^^, ^^^^− ^^ ^^ ^^, ^^with ℎ ^^, ^^ an amplitude and ^^ ^^, ^^ a phase factor, the nodes having correct knowledge of the same source ^^ ^^ selected for the sub-band ^^ being grouped into a first and a second group of nodes such that each of the nodes of the first group knows the phase ^^ ^^, ^^ of the transmission channel between this node and the destination (^^) for the sub-band ^^ and each of the nodes of the second group does not know the phase ^^ ^^, ^^ of the transmission channel between this node and the destination (^^) for the sub-band ^^, the method is such that the transmission by a node has the first group of the same second redundancy of the source ^^ ^^ is modulated by the phase factor ^^− ^^ ^^ ^^, ^^= corresponds to the conjugate ℎ ^ ∗ ^ , ^^ of the amplitude ℎ ^^, ^^ of the transmission channel between this node ^^ and the destination ( ^^) divided by its norm |ℎ ^^, ^^| and such that the transmission by a node has of the second group of the same second redundancy of the source ^^ ^^ intervenes without phase correction.

8. Method of transmitting messages in frames implemented by a telecommunications device intended for a telecommunications system with ^^ nodes whose ^^ sources ( ^^ ^^ ^^ ^^ { 1, … , ^^ } ) and ^^ − ^^ relay and the device ( ^^), ^^ ≥ ^^ ≥ 2, with orthogonal multiple access to the transmission channel between the ^^ nodes, with a maximum number of ^^ + ^^ ^^ ^^ ^^ time intervals per transmitted frame distributed between a 1 ère phase of T time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^, the message from a source having been coded before transmission according to an incremental redundancy type coding which generates several redundancies, the transmission being of the frequency division multiplexing type on a band divided into B mutually orthogonal sub-bands, ^^ ≤ ^^ ^^, such that the method comprises: - simultaneous reception by the device during the 1 ère phase on at least ^^ sub-bands of ^^ first redundancies of the ^^ messages of the ^^ sources, characterized in that the method further comprises: - transmission by the device of scheduling information ( ^^̂ ^^ ) indicating per sub-band a selected source not yet correctly decoded by the device called source to be assisted, the scheduling information taking into account a constraint of a maximum transmission power per node, - reception by the device, on the same sub-band of the same retransmission interval of the 2 ndephase, of the same second redundancy of the same source ( ^^ ^^ ) selected and coming from different nodes having correct knowledge of this same source.

9. Transmission method according to claim 8 further comprising: - transmission by the device of a set of sources correctly decoded by the device among the sources received by the device during the 1 ère phase, - reception by the device of sets of sources correctly decoded by the nodes and not yet correctly decoded by the device at the end of the 1 ère phase.

10. Method for transmitting messages in frames implemented by a telecommunications device intended for a telecommunications system with ^^ nodes whose ^^ sources ( ^^ ^^^^ ^^{1, … , ^^}) and ^^ − ^^ relay and a destination ( ^^), ^^ ≥ ^^ ≥ 2, the device forming one of the sources, 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 of ^^ time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^ , including a coding of a message before transmission according to an incremental redundancy type coding which generates several redundancies, the transmission being of the frequency division multiplexing type on a band divided into ^^ sub-bands orthogonal to each other, ^^ ≤ ^^ ^^, such that the method further comprises: - transmission of a first redundancy of a message from the source during the 1 èrephase, characterized in that the method further comprises: - receiving scheduling information ( ^^̂ ^^ ) indicating per sub-band a selected source not yet correctly decoded by the destination called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, - transmission during a retransmission interval of the 2 ndephase of a second redundancy of the message of the selected sources on the respective sub-bands, for the sources for which the device has correct knowledge, the transmission of the device on several sub-bands being subject to a maximum transmission power constraint.

11. Transmission method according to one of claims 1 to 10 according to which, for the same source, the first redundancy and the second redundancy are different.

12. Transmission method according to one of claims 1 to 11, according to which the scheduling information is determined on the basis of mutual information per sub-band ^^, ^^^^ ^^ ^^ , ^^, ^^, of an equivalent channel between the nodes having correct knowledge of the same source to be helped and the destination.

13. Telecommunication device (DIS) for transmitting framed messages, intended for a telecommunication system comprising ^^ nodes of which ^^ sources ( ^^ ^^^^ ^^{1, … , ^^}) and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, and a destination ^^, 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 of ^^ time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^, the transmission being of the frequency division multiplexing type on a band divided into ^^ ≥ 2 mutually orthogonal sub-bands, ^^ ≤ ^^ ^^, the device which corresponds to one of the sources comprises at least one microprocessor µP, a memory (MEM), a transmission chain (EM) and a reception chain (RE), the transmission chain (EM) comprises an encoder implementing an incremental redundancy type coding which generates several redundancies of the same message to be transmitted, such that: - the transmission chain (EM) is capable of transmitting a first redundancy of the message to be transmitted during the 1 ère phase, - the reception chain (RE) is able to receive scheduling information ^^̂ ^^of size ^^ indicating per sub-band a selected source not yet correctly decoded by the destination called source to be helped, the scheduling information taking into account a constraint of a maximum transmission power per node, - the transmission chain (EM) is furthermore capable of transmitting during a retransmission interval of the 2 nde phase a second redundancy of the message of the selected sources on the respective sub-bands, for the sources for which the device has correct knowledge, the transmission on several sub-bands being subject to a maximum transmission power constraint.

14. Telecommunication device (DIS) for transmitting framed messages, intended for a telecommunication system comprising ^^ nodes of which ^^ sources ( ^^ ^^^^ ^^{1, … , ^^}) and ^^ − ^^ relays, ^^ ≥ ^^ ≥ 2, and a destination ( ^^), 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 of ^^ time intervals and a 2 nde phase of at least one so-called retransmission time interval, 1 ≤ ^^ ^^ ^^ ^^ , the transmission being of the frequency division multiplexing type on a band divided into ^^ ≥ 2 sub-bands orthogonal to each other, ^^ ≤ ^^ ^^, the device which corresponds to one of the sources comprises at least one microprocessor (µP), a memory (MEM), a transmission chain (EM) and a reception chain (RE), such that: - the reception chain (RE) is capable of receiving simultaneously during the 1 èrephase on at least ^^ sub-bands of ^^ first redundancies of the ^^ messages of the ^^ sources, - the transmission chain (EM) is able to transmit scheduling information ( ^^̂ ^^ ) indicating per sub-band a selected source not yet correctly decoded by the device called source to be assisted, the scheduling information taking into account a constraint of a maximum transmission power per node, - the reception chain (RE) is furthermore capable of receiving on the same sub-band of the same retransmission interval of the 2 nde phase, the same second redundancy from the same source ( ^^ ^^ ) selected and coming from different nodes having correct knowledge of this same source.

15. Telecommunication system comprising a destination ( ^^) and ^^ nodes whose ^^ sources ( ^^ ^^ ^^ ^^ { 1, … , ^^ }) and ^^ − ^^ relay, ^^ ≥ 2, with orthogonal multiple access to the transmission channel between the ^^ nodes and the destination, suitable for implementing a transmission method according to one of claims 1 to 12.

16. Computer program on an information medium, said program comprising program instructions adapted to the implementation of a method according to any one of claims 1 to 12 when said program is loaded and executed in telecommunications equipment.

17. Information medium comprising program instructions adapted to the implementation of a method according to any one of claims 1 to 12, when said program is loaded and executed in telecommunications equipment.

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