Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/155—Ground-based stations
  • H04B7/15592—Adapting at the relay station communication parameters for supporting cooperative relaying, i.e. transmission of the same data via direct - and relayed path
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
  • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
  • H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
  • H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
  • H04L1/0076—Distributed coding, e.g. network coding, involving channel coding
  • H04L1/0077—Cooperative coding
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/155—Ground-based stations
  • H04B7/15521—Ground-based stations combining by calculations packets received from different stations before transmitting the combined packets as part of network coding
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L2001/0092—Error control systems characterised by the topology of the transmission link
  • H04L2001/0097—Relays

Definitions

• TITLE OMAMRC process and system with FDM transmission
• 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 at least two nodes which can be relays or sources.
• a relay has no message to transmit.
• a relay is a node dedicated to relaying messages from sources while a source has its own message to be transmitted and can also in certain cases relay messages from other sources i.e. the source is said to be cooperative in this case.
• 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 networks of sensors.
• Such a network of sensors is a multi-user network, made up of several sources, several relays and a recipient using a time-orthogonal multiple access scheme of the transmission channel between the relays and the destination, denoted OMAMRC (“Orthogonal Multiple- Access Multiple-Relay Charnel ”according to the English terminology).
• OMAMRC Orthogonal Multiple- Access Multiple-Relay Charnel
• OMAMRC transmission system implementing a slow link adaptation is known from application WO 2019/162592 published on August 29, 2019.
• the OMAMRC telecommunication system describes has M sources, possibly L relays and a destination, M ⁇ 2, L ⁇ 0 and it uses an orthogonal time multiple access scheme of the transmission channel which applies between the nodes taken from among the M sources and the L relays.
• the maximum number of time slots per transmitted frame is M + T max with M slots allocated during a first phase to successive transmissions from M sources and T used ⁇ T max slots for one or more cooperative retransmissions allocated during a second phase to one or more nodes selected by the destination according to a selection strategy.
• the OMAMRC transmission system considered comprises at least two sources, each of these sources being able to operate at different times either as a source or as a relay node.
• the system may optionally further include relays.
• the Node terminology covers both a relay and a source acting as a relay node or as a source.
• the system considered is such that the sources can themselves be relays.
• the relay differs from a source because it has no message to transmit of its own, ie it only retransmits messages from other nodes. The relay always performs a cooperative retransmission.
• the links between the different nodes of the system are subject to slow fading and Gaussian white noise.
• Knowledge of all system links (CSI:
• Channel State Information by destination is not available. Indeed, the links between the sources, between the relays, between the relays and the sources are not directly observable by the destination and their knowledge by the destination would require an excessive exchange of information between the sources, the relays and the destination. .
• CDI Channel Distribution Information
• CDI Channel Distribution Information
• the link adaptation is slow, that is to say that before any transmission, the destination allocates initial rates to sources knowing the distribution of all channels (CDI: Channel Distribution Information).
• CDI Channel Distribution Information
• the transmissions of the messages from the sources are divided into frames during which the CSIs of the links are assumed to be constant (slow fading assumption).
• the rate allocation is assumed not to change for several hundred frames, it only changes with CDI changes.
• the transmission of a frame takes place in two phases which are optionally preceded by an additional so-called initial phase.
• the destination determines an initial throughput for each source taking into account the average quality (eg SNR) of each of the links in the system.
• SNR average quality
• the destination estimates the quality (for example SNR) of the direct links: source to destination and relay to destination according to 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 the relays by using, for example, the reference signals.
• the sources and the relays transmit to the destination the average qualities of the links. This transmission takes place before the initialization phase. Only the average value of the quality of a link being taken into account, its refresh takes place on a long time scale, that is to say over a period of time. which allows to average the rapid variations (fast fading) of the channel. This time is of the order of the time required to travel several tens of wavelengths of the frequency of the signal transmitted for a given speed.
• the initialization phase occurs for example every 200 to 1000 frames.
• the destination goes back to the sources via a return path the initial rates that it determined.
• the initial flow rates remain constant between two occurrences of the initialization phase.
• the M sources successively transmit their message during the M time slots using respectively modulation and coding schemes determined from the initial bit rates.
• the number N 1 of uses of the channel (channel use, ie resource element according to 3GPP terminology) is fixed and identical for each of the sources.
• the messages from the sources are retransmitted in a cooperative manner by the relays and / or by the sources.
• This phase lasts at most T max time slots.
• the number N 2 of channel use is fixed and identical for each of the sources.
• the independent sources broadcast during the first phase their coded information sequences in the form of messages to the attention of a single recipient.
• Each source broadcasts its messages at the initial rate.
• the destination communicates its initial rate to each source via very limited rate control channels.
• the sources each transmit their respective message in turn during time slots (time slots) each dedicated to a source.
• Sources other than the one transmitting and possibly the relays, of the "Half Duplex" type receive successive messages from the sources, decode them and, if they are selected, generate a message only from the messages from the sources decoded without error.
• the selected nodes then access the channel orthogonal in time to each other during the second phase to retransmit their generated message to the destination.
• the destination can choose which node should retransmit at any given time.
• the method implements a strategy to maximize the average spectral efficiency (utility metric) within the system considered under constraint to respect an individual quality of service (QoS) per source ie an average individual BLER per source:
• R i is a variable which takes from the discrete values taken in a finite set the number of flow rates corresponding to the different coding and modulation schemes (MCS, Modulation and Coding Scheme) available for transmission,
• T used ⁇ T max presents the number of cooperative retransmissions used during the 2 nd phase
• E, (T used ) is the average of the number of cooperative retransmissions used during the second phase
• BLERi represents the block error rate for source i.
• BLERi denotes the function with multiple variables BLERi (R 1 ..., R M ) which depends on the current value taken by the flow variables R 1 ..., R M.
• the algorithm based on an interference-free or “Genie Aided” approach is used to solve the problem of optimization of multidimensional allocation of throughput (rate). This approach consists in independently determining each initial rate of a source by assuming that all the messages of the other sources are known by the destination and the relays then in iteratively determining the rates by initializing their value with the values determined according to the approach. "Genie Aided”.
• the utility metric which consists of spectral efficiency is conditioned by the node selection strategy that occurs during the second phase.
• the present invention relates to a method of transmitting messages intended for an OMAMRC telecommunication system with M sources s t ie ⁇ 1, ..., M), possibly L relay r 1 ..., r L and a destination, M ⁇ 2, L ⁇ 0, M ⁇ B.
• the transmission is of the LDM type on a band divided into B orthogonal sub-bands between them.
• the method is such that it comprises: a simultaneous transmission of the M sources during a time interval with allocation of at least one sub-band per source and at least one cooperative retransmission during a time interval of at least one relay node taken from among the M sources and the L relays selected according to a selection strategy with allocation of at least one sub-band per selected node, to maximize a quality of service metric.
• the allocation of sub-bands between the sources makes it possible to reduce the time necessary for transmitting data since the sources transmit simultaneously in one and the same first time slot (time slot). Such a process is therefore well suited for services requiring in terms of latency.
• the allocation of one or more sub-bands per source as well that the source selection strategy at subsequent intervals, are performed to maximize a quality of service metric, eg BLER, spectral efficiency. Maximizing the quality of service makes it possible to optimize the bit rate or to reduce the transmission power of the sources for the same bit rate.
• the slot or slots following the first time slot are dedicated to retransmissions including at least one cooperative retransmission.
• a cooperative retransmission is either a transmission by a relay or a transmission by a source capable of helping the destination to decode at least one other source.
• a non-cooperative retransmission a retransmission by the source of its own message.
• a cooperative retransmission is a transmission by one node that contains information about at least one message from another node.
• the transmission of a relay is by nature a cooperative retransmission 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 relay nodes ensures an increase in the reliability of the transmissions.
• the selection strategy is such that a relay node which decodes a set of sources at a time interval t can only cooperate at a time interval t + 1 for a single source of its set.
• This embodiment makes it possible to obtain a direct expression of the individual cut-off event of a source, that is to say without the need to obtain the cut-off events of all the subgroups of the sources containing the source considered.
• the choice of the source, among the sources not yet decoded without error by the destination, with which the node cooperates can be random, the transmission from the node to the destination therefore includes the indication of the source with which it cooperates.
• the common cutoff of a set of sources is obtained simply as the union of the individual cuts of the sources of the set.
• the method is such that: the destination broadcasts to the relay nodes its set of correctly decoded sources among the sources received during a transmission interval, the relay nodes which have correctly decoded a source not correctly decoded by the destination informs the destination, the destination broadcasts to the relay nodes a vector ⁇ t comprising the relay nodes selected for the subbands for cooperative or non-cooperative retransmission during the next transmission interval.
• the destination sends its set of correctly decoded sources back to the relay nodes after receiving data transmitted during a transmission interval.
• This feedback can take place via a control channel.
• the destination goes up 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 ie its set of correctly decoded sources contains the M sources, a new frame is transmitted.
• a relay node informs the destination by transmitting a single bit in a control channel.
• the signaling of the relay nodes to the destination is minimal and therefore has the advantage of consuming very little channel resource.
• the destination can implement a selection strategy which, for example, consists in maximizing at a given time interval t the sum of the mutual information between the nodes that can help with their allocated subbands and the destination
• a relay node informs the destination by transmitting its set of correctly decoded sources.
• the signaling of the relay nodes to the destination according to the latter mode consumes more channel resources. But the information transmitted allows the destination to select relay nodes more efficiently to help it decode as many sources as possible.
• the destination selects the relay nodes allowing it to correctly decode the most sources at the end of the cooperative or non-cooperative retransmission.
• the destination returns to the relay nodes a vector in which are selected the relay nodes which maximize the number of sources correctly decoded by these relay nodes and not yet correctly decoded by the destination.
• the vector further includes the allocation of the subbands to the selected relay nodes.
• the destination selects the relay nodes such that the sum of the mutual information between the nodes which can help with their allocated subbands and the destination is maximized.
• the method chooses the vector which maximizes the sum of the mutual information between the nodes which can help with their associated subbands and the destination:
• the method is with slow link adaptation and is such that rates allocated to the sources are determined to maximize a metric expressed as an average utility function under constraint of an average individual BLER for each source: a variable representing the initial flow allocated to the source i, i ⁇ ⁇ 1, ..., M)
• K j the number of data transmitted on n o, i XF uses of the channel by source i
• T used the number of time slots used for cooperative / possibly non-cooperative retransmissions
• E (T used ) an average of the number of time slots used for cooperative / possibly non-cooperative retransmissions
• the method is with rapid link adaptation and is such that the bit rates allocated to the sources are determined to maximize a metric expressed in the form of an average utility function under the constraint of the individual cuts of the sources:
• T used Ie number of time slots used for cooperative / possibly non-cooperative retransmissions a variable representing the initial bit rate allocated to the source i, i ⁇ ⁇ 1,, M ⁇ .
• a further subject of the invention is a system comprising M sources ..., s M , L relay r 1 ..., r L and a destination d, 0, for implementing a transmission method according to 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 may be of the ROM type, for example a CD ROM or a microelectronic circuit ROM, or else of the magnetic type, for example a USB key or a hard disk.
• 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 optionally be applied to the software application and to the memory mentioned above.
• FIG. 1 is a diagram of an example of a so-called Cooperative OMAMRC (Orthogonal Multiple Access Multiple Relays Channel) system according to the invention
• FIG. 2 is a diagram of a transmission cycle of a frame according to an exemplary implementation of the invention
• FIG. 3 is a diagram of the protocol for the exchange of information between the destination and the nodes, sources and relays, according to one embodiment of the invention.
• 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 times the channel is used is related to the available frequency band and the transmission time.
• Each source in the game S communicates with the unique destination with the help of other sources (user cooperation) and cooperating relays.
• the sources, relays, and destination are equipped with a single receiving antenna
• T max ⁇ 1 is a system parameter; - the instantaneous quality of the channel / direct link in reception (CSIR Channel State information at Receiver) is available at the destination, at the sources and at the relays;
• Nodes include relays and sources that can behave like a relay when they are not sending their own message.
• the nodes, M sources and L relays access the transmission channel in an orthogonal frequency multiple access pattern and operate in a full-duplex mode that allows them to listen to transmissions from other nodes without interference.
• the channel strip is divided into B sub-bands the number of which is assumed to be greater than or equal to the number of sources: B ⁇ M.
• Each sub-band associated with a time interval determines F uses of the channel (F element resource).
• a sub-band can include, for example, as many sub-carriers as an OFDM symbol.
• N B X F.
• a transmission cycle lasts 1 + T used timeslots with T used ⁇ T max and T max the maximum number of timeslots. At each time interval, none, one or more sub-bands are allocated to a node according to a first partition.
• all the sources transmit, assuming that B 3 M, respectively on one or more sub-bands allocated to each source.
• the partitions can be different between all the transmission intervals including the first.
• the selection of the nodes and the allocation of the sub-bands are implemented by a scheduler, typically hosted by the destination.
• the selected node i is a source i denoted S i , i ⁇ ⁇ 1, ..., M) otherwise i> M and the selected node is a relay i - M denoted r iM , i ⁇ ⁇ M + 1,, M + L ⁇ ,
• B is the vector of dimension B of the nodes selected for the transmission interval t, both during the first phase and during the second phase.
• the i th element a ti of the vector a t designates the i th sub-band and the selected node active during this time interval t in this sub-band i, i ⁇ ⁇ 1, ..., B ⁇ .
• the order in the vector corresponds to the order of the sub-bands.
• n t ⁇ ⁇ 0, ..., B ⁇ M + L is the vector of dimension M + L of the number of sub-bands allocated for each node which varies between 0 (the node is inactive) and B (the node occupies all sub-bands), source or relay, for the transmission interval (time slot) t whether during the first phase or during the second phase.
• the i th element n ti of the vector n t designates the number of sub-bands allocated to node i at the transmission interval (time slot) t, i ⁇ ⁇ 1, ..., M + L ⁇ .
• the sum of the component elements the vector n t is equal to B the number of sub-bands.
• h ab is the attenuation gain of the channel (fading) between node a (source or relay) and node b (source, relay or destination) which follows a complex circular symmetric Gaussian distribution with zero mean and variance y a , b , the gains are independent of each other,
• T used is the minimum number of retransmission time intervals ie during the second phase which leads to zero faults for all the sources (the individual cut-off event of each of the sources is equal to zero):
• the individual cut-off event of the source s after the interval t (round t) retransmission depends on the vector t of selecting nodes, the vector n t allocation of sub-bands and the game has been $ _i sources decoded at the end of the preceding interval, t-1.
• a 0 is the selection vector of the source nodes transmitting during the transmission phase
• n 0 is the allocation vector of sub-bands allocated for each source during the transmission phase
• ⁇ S d 0 is the set of sources decoded by the destination at the end of the first phase.
• the common failure event F or I and sub set of sources S after time interval t (round t) is the event that at least one source of subset B is not decoded correctly by the destination at the end of this interval t. Subsequently, the dependencies of are omitted to simplify the notations.
• I e j had sources not successfully decoded by the destination at the end of the time interval t (round t). From an analytical point of view, the event of common cut-off of a subset S of sources occurs ie is satisfied if the vector of the bit rates of these sources is not included in the corresponding MAC capacity region.
• [P] represents the brackets of Iverson i.e. which gives the value 1 if the event P is satisfied and the value 0 if not,
• T ; j the mutual fading information block from node i to destination d for the rti i sub-bands allocated to node i at time interval l ⁇ ⁇ 1, .., T used ): (5) where I ai /, d is the mutual information between the node a which is allocated the sub-band / at the time interval (round) l E ⁇ 1, ..., T used ⁇ and the destination d.
• Mutual information depends on the power transmitted on the sub-band of the channel ie between node a ; t and the destination d with P T the total power of this node. If node i is not selected at time interval l then the mutual information block is zero.
• the cutout event for a given source s is defined in the form: which is by definition the intersection of all the common breaking events corresponding to a set of sources ⁇ including the source s.
• This approach makes it possible to predict the result of implementing a parity check (CRC check) without going through the simulation of the entire transmission (modulation coding) and reception (detection / demodulation, decoding) chain. ).
• CRC check parity check
• It defines an abstraction of the physical layer.
• Certain adjustments obtained by simulation (called calibration within the framework of the abstractions of the physical layer) for a given coding scheme can be carried out by introducing weighting parameters of the mutual information and / or SNRs of the links.
• the two transmission phases of the transmission method can be preceded by an initial phase of determining an initial rate.
• This phase can occur once every several hundred frames (ie each time the quality statistics of the channel / link change) in the “slow fading” case, we speak of slow link adaptation. Or this phase can occur much more frequently and at most each cycle, we speak of rapid link adaptation.
• the link adaptation is fast or slow, the bit rate of each source and the allocation of sub-bands are known before the start of transmission.
• the destination can determine the gains (CSI Channel State Information) of the direct links that is, source-to-destination and relay-to-destination links. The destination can therefore deduce average values for the direct links within the framework of a slow adaptation.
• the statistics of the channels are assumed to be constant between two initialization phases, the transmission to the destination of the metrics by the sources and the relays may only take place at the same rate as the initialization phase.
• the channel statistic of each link is assumed to follow a circular-centered complex Gaussian distribution and the statistics are independent between the links.
• the destination transmits for each source s a representative value (index, MCS, bit rate, etc.) of an initial bit rate R j .
• Each of the initial rates unambiguously determines an initial modulation and coding scheme (MCS) or conversely each initial MCS determines an initial rate.
• MCS modulation and coding scheme
• the rise of the initial flow rates R [ is carried out via very limited flow control channels.
• These initial rates are determined by the destination so as to maximize a quality of service metric, for example an average spectral efficiency.
• the quality of service metric is, according to one embodiment, an average spectral efficiency which is expressed in the form:
• T used I e number of time slots used for cooperative or non-cooperative retransmissions
• E (T used ) an average of the number of time slots used for the retransmissions whether they are cooperative or non-cooperative
• bit rate and the allocation of sub-bands by source remain unchanged for several hundred transmissions of messages from the sources, which makes it possible to average the block error rate (BLER) of the source i on the channel statistics (CDI: Channel Distribution Information) known to the destination.
• BLER block error rate
• CDI Channel Distribution Information
• the quality of service metric is, according to one embodiment, an average utility function under constraint of the individual cuts of the sources defined by transmitted message and the throughput and the allocation of sub. -bands can change from one message to the next:
• O it is the individual cut-off event of source i at the retransmission interval t which is equal to one in the event of a fault or zero in the event of success (correctly decoded source), O ⁇ 0 is the individual cut-out event at the end of the transmission phase (first phase of a time interval),
• each source i ⁇ 1, 2, 3) transmits its code words.
• the number of sub-bands allocated to a source differs between the sources.
• the sub-bands fi, Î2 and fs are allocated to the source 1
• the sub-band f 3 is allocated to the source 2
• the sub-band f * is allocated to the source 3.
• the vector of allocation of sub-bands by node is thus During the second so-called retransmission phase and for the first time interval, only the sources 2, 3 and the relay 2 are selected and the sub-band fi is allocated to the source 3, the sub-bands f 2 , Î 3 and f * are allocated to relay 5 and the sub-band fs is allocated to source 2.
• n 2 [2,0,0,3,0] T.
• FIG. 3 An embodiment of the protocol for the exchanges between the nodes and the destination is illustrated in FIG. 3.
• 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 the M messages from the respectively M sources.
• the transmission of a frame (which defines a transmission cycle) takes place during 1 + T used time intervals: 1 interval for the 1 st phase of capacity n oi uses the channel for each source i, T used intervals for the 2 e capacity phase n ti uses the channel for each source i.
• each source s ⁇ S transmits after coding a message u s comprising K s information bits u s being the two-element Galois body.
• the message u s includes a CRC type code which allows the integrity of message u s to be checked.
• the message u s is coded according to the initial MCS. Since the initial MCSs may be different between sources, the lengths of the encoded messages may be different between the sources.
• the encoding uses an incrementally redundant code. The resulting code word is segmented into redundancy blocks. The incremental redundancy code can be of the systematic type, the information bits are then included in the first block.
• the incrementally redundant code is of the systematic type, it is such that the first block can be decoded independently of the other blocks.
• the incremental redundancy code can be achieved for example by means of a finite family of punched linear codes with compatible yields or of non-yielding codes modified to operate with finite lengths: raptor code (RC), punched turbo code of compatible yield ( RCPTC rate compatible punctured turbo code), rate compatible punctured convolutional code (RCPCC rate compatible punctured convolutional code), LDPC rate compatible (RCLDPC rate compatible low density parity check code).
• RC raptor code
• RCPTC rate compatible punctured turbo code rate compatible punctured convolutional code
• RCPCC rate compatible punctured convolutional code rate compatible punctured convolutional code
• LDPC rate compatible low density parity check code LDPC rate compatible
• each full-duplex node can transmit and listen simultaneously to all the other nodes given that, to transmit, each node is allocated one or more sub-bands which are different between the nodes.
• the destination, sources and relays attempt to decode messages received at the end of a time interval. Success of decoding at each node is decided using CRC. The destination and the nodes thus determine their set of correctly decoded sources.
• the destination d transmits its set of correctly decoded sources at the end of the previous time interval S dt _ 1 using for example a control channel of feedback broadcast control channel.
• t ⁇ 1, ..., T used ).
• This return can consist of a vector of M bits.
• the nodes, sources and relays compare the set S dt _ 1 to their set of correctly decoded sources.
• the node informs the destination thereof by using for example a dedicated control channel of unicast type.
• the information transmitted by a node can consist of its set of correctly decoded sources or, as illustrated by FIG. 3, of a bit, for example set to one.
• the destination follows a certain strategy to decide which node (s) selected to transmit at the time interval (round) t.
• the destination informs the nodes of this selection by transmitting the vector a t using for example the return broadcast control channel.
• Each node which receives the vector a t can determine whether it is selected and on which sub-band (s) it should transmit.
• At least one selected node, source or relay During this second phase and for at least one retransmission interval among the T used retransmission intervals, at least one selected node, source or relay, generates a cooperative retransmission. Outside of the at least one time slot, the retransmissions can be cooperative or non-cooperative.
• the node selected for retransmission transmits u at after multi-user encoding, the words or part of the words that it has correctly decoded.
• the selected node can transmit parities determined from messages from its correctly decoded source set using Joint Network Channel Coding.
• the other nodes and the destination can improve their own decoding by exploiting the transmission of the selected node and update their correctly decoded source set accordingly.
• the destination thus controls the transmission of the nodes using a return channel. This improves spectral efficiency and reliability by increasing the likelihood that all sources will be decoded by the destination.
• the destination selects those which maximize the sum of the mutual information among the set Zt of the different allocations of sub-bands to the nodes which can help at the interval t.
• This strategy only requires knowledge of the nodes that can help, it is compatible with the way in which the nodes transmit information in the form of a bit.
• the selection criterion can be expressed in the form: (8) with Z t the set of possible vectors a t which correspond to the selection of the nodes which can help the destination at the interval (round) t.
• the destination selects the nodes which make it possible to obtain the most newly correctly decoded sources at the destination at the end of the current interval t ie which maximize the cardinality of the set of sources correctly decoded by the destination at the end of the current interval t.
• the method reviews all the possible values of the vector a t and retains the one which leads to the greatest number of newly decoded sources.
• the method does not take into account the nodes which cannot help the non-sources. still decoded since it targets the greatest number of newly decoded sources, ie; only the nodes i which satisfy
• This strategy further requires knowledge of the correctly decoded source set of all previously selected nodes.
• the method chooses the vector a t which maximizes the sum of the mutual information. In fact, at a time interval t, this is the only element that can be maximized to maximize the right part of the individual cut-off events and of the common cut-off events.
• the presence of C ti in the expression of the common cut event reflects the fact that the only nodes that can be selected are those that can help, ie having decoded at least one source not yet decoded by the destination.
• the selection criterion can then be expressed in the form: (9) with A t the set of candidate nodes which maximize the clearance of the destination at the end of the interval (round) t.

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• 2020
  • 2020-06-24 FR FR2006623A patent/FR3111495A1/fr not_active Withdrawn
• 2021
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  • 2021-06-18 US US18/002,736 patent/US20230246704A1/en active Pending
  • 2021-06-18 CN CN202180045475.0A patent/CN115769510A/zh active Pending
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