Mu-mimo communication method distinguishing between data and reference symbols for power allocation, and corresponding devices

Abstract

The invention relates to a communication method (1) which comprises: - by way of one dedicated control channel (PDCCH) per user equipment u, transmitting to U user equipments control information indicating for a user equipment u at least one power ratio (β PDSCH,l ) per time frequency resource element (RE) between reference symbols (DMRS) and data transmitted to the user equipment u for a given antenna port (l).

Description

[0001] DESCRIPTION TITLE: MU-MIMO communication method distinguishing between data and reference symbols for power allocation and corresponding devices Field of the invention The present invention relates to the field of telecommunications. Within this field, the invention relates more particularly to digital communications implemented by a communication system with a transmitter ^^^^ transmitting antennas and receivers with ^^^^ receiving antennas called MIMO (Multiple Input Multiple Output) which makes it possible to allocate a power level per spatial layer, i.e., per transmitting antenna port while maximizing a transmission rate. For downlink communication, the transmitter may be a base station, for example of the eNodeB (evolved Node B) or gNodeB type for networks based on LTE, LTE Advanced and subsequent technologies (5G, etc.), or a Wi-Fi access point, etc.A receiver can be a terminal such as a smartphone, tablet, connected object, etc. For uplink communications, there are as many transmitters as there are terminals and the receiver is a base station. The invention finds applications in any beamforming-based system, in particular in radio communication networks according to the 4G, 5G and following standards defined by the 3GPP, WiFi communication networks according to the various IEEE 802.11 standards, etc. Prior art Figure 1 illustrates a multi-user MIMO communication system with ^^^^ transmitting antennas ANT_E and ^^^^ receivers with ^^^^. ^^ ^^ ^ ^ ^^ ANT_R receiving antennas each with ^^^^ ^^ ^^ ^ ^ ^^< ^^^^. The system includes at least one access point, called a base station SB in cellular systems, and ^^^^ UE terminals, those of the users. In the LTE (3 / 4G) standard specified in 3GPP, the number of receiving antennas for a so-called "smart phone" terminal is at least two, while for the NR standard (5G of 3GPP), the number of receiving antennas for this type of terminal is specified at at least four antennas for certain bands (3.5GHz n77 / 78). For base stations, the number of transmitting antennas has continued to increase to reach up to 64, or even 128 antennas in massive MIMO. Note that an antenna port in the context of 3GPP mobile standards and in the context of the request is associated with a "logical" antenna which can group together one or more RF (Radio Frequency) chains, each RF chain including a digital to analog conversion and / or including an analog to digital conversion.The mapping of a logical antenna to ^^^^ ≥ 1 RF chains is done via a complex vector of dimension N: the signal sent to a logical antenna is multiplied by this complex vector to generate the N inputs of the N RF chains. Each antenna includes one or more radiating elements. If the number of transmit RF chains and receive RF chains is the same at the base station, this is not the case for mobiles which can have a number of transmit RF chains lower than the number of receive RF chains, typically two transmit RF chains for four receive RF chains. Regarding a base station, a transmit / receive RF chain is called "TXRU, Transceiver Units" in the 5G standard. Figure 2 which corresponds to figure 6.3-1 of the TS36.211 specification schematically illustrates part of the baseband processing of the data to be transmitted.According to this standard, it is expected that data can be encoded according to two streams with different rates. The encoded data put in the form of Cw code words are scrambled with an SCR scrambler, then mapped onto a constellation with a C_MAP mapper. The outputs of the mapper are divided into spatial layers by an L_MAP layer mapper. The different Lay spatial layers are then pre-coded by a PRE_COD pre-coder. The pre-coded data of the different spatial layers are mapped by resource element by a RE_MAP resource mapper. At the output of the resource mapper, the data of each spatial layer is injected into an OFDM multicarrier modulator to generate an OFDM symbol. These OFDM symbols feed the antenna ports. Each spatial layer to which an antenna port corresponds feeds a single user (or recipient) at a given time. A user can benefit from several spatial layers simultaneously.In the upstream channel, the processing specified by the TS36.211 normative document and corresponding to figure 5.3-1 of this document is very similar to that of figure 2. In a conventional manner for telecommunication systems with a transmission channel CH between a transmitting part EM and a receiving part RX1, RXu, RXU, the transmission resources are represented according to one or more time-frequency grids, a representation of which is given by figure 3 which corresponds to figure 6.2.2-1 of the TS36.211 specification of the LTE (4G) standard of the 3GPP. If we consider the context of the 4G or 5G standard, a radio time-frequency resource is a resource element (RE).A resource element, in this context, refers to the smallest time-frequency granularity that is identified by the indices ^^^^ and l (i.e., a subcarrier and a symbol time corresponding to the duration of a multi-carrier symbol, typically OFDM in the case of an OFDM multi-carrier transmission) on the time-frequency grid of Figure 3. On this grid, frequencies follow the vertical axis and time the horizontal axis. For the 5G standard, there is one time-frequency grid per antenna port and for each of the uplink and downlink directions. According to the terms of this standard, a frame is divided into subframes. Since the spacing between subcarriers of an OFDM symbol is configurable, each subframe includes a number of OFDM symbols that varies according to the spacing between subcarriers since the duration of a symbol is the inverse of the spacing between subcarriers.OFDM symbols are grouped into slots, each slot corresponding to the granularity of a scheduling decision known by elementary time interval (TTI). With reference to the radio communication networks specified within 3GPP, mechanisms are specified for a terminal to be connected to a base station. The Physical Downlink Shared Channel (PDSCH) is the main channel used for the transmission of data in unicast form and for the transmission of system information, later called data channel. The receiver determines the time-frequency resource elements it must decode by exploiting the control information defined semi-statically at the level of higher layers (RRC) and control information transmitted dynamically.A dedicated physical control channel per terminal, called PDCCH (Physical Downlink Control Channel), is used for the dynamic transmission of control information for the downlink and for the uplink, and for the scheduling of the PDSCH and PUSCH physical transmission channels. The PDCCH channel is organized according to several possible formats, called DCI (Downlink Control Information) formats. A DCI format consists of several fields, each field carrying specific information (e.g. transport blocks or PRB (Physical Resource Block) allocated (one or two transport blocks can be allocated), modulation and coding schemes or MCS (for "Modulation and Coding Scheme") allocated for each transport block, identification of the allocated antenna ports corresponding to the configuration by the RRC layer (semi-static) of the reference symbols, DMRS, number of spatial layers (rank), etc.).The information bits of a PDCCH channel (i.e. the bits of the DCI format) are then associated with a CRC code ("Cyclic Redundancy Check") to allow error detection. The particularity of this CRC code is that it is scrambled with the RNTI identifier of the terminal to which the PDCCH channel is dedicated. This allows the terminal to validate that the PDCCH channel it is decoding is indeed intended for it. Indeed, if another terminal (which has a different RNTI identifier) ​​tries to verify the validity of the PDCCH channel using this other RNTI identifier, the verification of the CRC code returns an error. As is known, the capacity of cellular mobile telecommunications networks, and in particular that of the networks specified in 3GPP (LTE / 3G-4G, 5G, etc.) is limited by interference. This interference can be of different natures.Among the most damaging in terms of cellular network capacity, we can distinguish in particular: - SU-MIMO interference (for Single User - Multiple Input Multiple Output) linked to the use of multiple antennas in transmission and reception, and which corresponds to the interference generated between MIMO data streams allocated to the same terminal; - MU-MIMO interference (for Multiple User - Multiple Input Multiple Output) linked to the use of multiple antennas in transmission and reception which corresponds to the interference generated between MIMO data streams allocated to different terminals; and - intercellular interference, generated between signals transmitted by different cells and intended for different terminals. Various methods for reducing the effect of this interference on network performance are known from the state of the art. Thus, MU-MIMO type interference can be treated in particular using beamforming.Beamforming is a signal processing technique used in MIMO communication systems comprising antenna or sensor arrays for directional transmission or reception of signals. This method consists of applying complex coefficients to the data streams transmitted or received by the antennas in order to assign them particular spatial properties (for example, a preferred direction). Thus, the complex coefficient applied to each antenna or antenna port is called the precoding coefficient and the set of these coefficients forms the precoding matrix ^^^^ implemented by the PRE_COD precoder. This precoding can be used to spatially separate streams intended for different terminals in order to allow receiving terminals to detect a stream with reduced interference from other streams.Beamforming is thus achieved by combining the elements of a phased array and amplitude controlled antenna array in such a way that: • signals interfere constructively in particular directions, • interference is destructive in other directions. Beamforming can be used on the transmitter side but also on the receiver side to achieve spatial selectivity. By applying appropriate precoding ^^^^, the transmitter can transmit data on the same time-frequency radio resources to several receivers with several spatial layers, a so-called MU-MIMO mode. The selection on the transmitter side of the appropriate precoding ^^^^ that maximizes spectral efficiency, evaluated for example by the sum of the MIMO communication rates, is subject to a transmission power constraint.The majority of prior art precoding algorithms are based on optimizing the performance of a MIMO transmission under a single total transmission power constraint. For example, water-filling power allocation, which allocates power based on channel conditions, maximizes SU-MIMO capacity under a single total transmission power constraint per resource element. Let ^^^^ be the data vector to be transmitted, ^^^^. each component of which has a power normalized to one, ^^^^ the total number of spatial layers transmitted to the ^^^^ receivers, ^^^^ = ∑ ^ ^ ^ ^ ^ ^ ^ ^ =^^^^ ^^^^ ^^^^ , ^^^^ the precoding matrix, ^^^^ = [ ^^^^ ^^^^ ^^^^ ^^^^ … ^^^^ ^^^^ ] ∈ ℂ ^^^^× ^^^^ avec^^^^ the number of transmitting antennas and ^^^^ the diagonal matrix of transmitted power per antenna port, ^^^^ = ^^^^ ^^^^ ^^^^ ^^^^( ^^^^ ^^^^ , ^^^^ ^^^^ ,⋯ , ^^^^ ^^^^ ) ∈ ℂ ^^^^× ^^^^ . The pre-coding matrix ^^^^ performs a virtualization of the ^^^^ transmitting antennas into ^^^^ antenna ports. The antenna concept can itself be based on a virtualization of radiating elements. For example, two radiating elements can have the same signal as input and therefore share the same virtualized antenna port. The pre-coding ^^^^ is described by a matrix of size ^^^^ × ^^^^, that is to say of ^^^^ rows, number of transmitting antennas, and ^^^^ columns, number of antenna ports, which can be written: The total transmission power constraint for a given resource element can then be expressed in the following form: where tr(… ) is the trace, ^^^^ †is the transconjugate matrix, called "daguer", that is to say the transposed matrix of the conjugate matrix of the matrix ^^^^, P maxis the maximum energy per resource element (EPRE). In the TS38.214 standard published by 3GPP (5G), under clause 4.1 "Power allocation for downlink" the ratio ^^^^ between the energy per resource element (EPRE) of the DMRS references and the energy per resource element (EPRE) of the data PDSCH channel is tabulated according to the configuration of the DMRS. The disadvantage of this approach is that a spatial layer with a very low power allocation will have a very noisy channel estimate because the associated DMRS will have very low power. By misuse of language in the application, the power per resource element designates the energy per resource element. The approach recalled above is not well adapted to real MIMO systems since these are characterized by a limitation of transmission power per power amplifier, i.e., per antenna (TXRU).Precoding algorithms must therefore satisfy these per-antenna power constraints while maximizing the performance of MIMO communications. The transmitted power constraint per antenna ^^^^ must therefore be given by the following expression:. Which can also be written in the form: where ^^^^^^^^ ^^^^ ^^^^is the maximum power per antenna per resource element and ^^^^ the power per resource element for the ^^^^ layer. ^^^^ The user's pre-coded channel ^^^^ corresponds to: ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ = ^^^^2^^^^2, … ,� ^^^^ ^^^^ ^^^^ ^^^^ ] with ^^^^ ^^^^ ℂ ^^^^ ^^^^^^^^× ^^^^the channel corresponding to the user ^^^^. At the receiver ^^^^, the pre-coded channel, i.e., which includes the pre-coding ^^^^, is estimated from the demodulation reference signals (Demodulation Reference Signal or DMRS for LTE or NR systems (5G of 3GPP)) orthogonal to each other (in frequency and / or in time and / or in code) which are transmitted on the same antenna ports as the data (data) intended for this receiver ^^^^ and which have therefore undergone the same pre-coding ^^^^. This estimation of the pre-coded channel is used in reception during the demodulation of the received signals and the decoding of the data. The DMRS symbols carried by a spatial layer to which an antenna port corresponds are orthogonal to the DMRS symbols carried by another spatial layer, i.e., another antenna port, and are not interfered by useful symbols. A DMRS symbol is specific to a user.The quality of the pre-coded channel estimation made in reception depends on the reception power of the DMRS signals. However, these DMRS signals, as for the data, are transmitted with a single maximum total power constraint ^^^. ^ ^^^^ ^^^^ ^^^^per resource element knowing that the different antenna ports share the same time-frequency resource elements. The disadvantage of this approach is that when the data and the DMRS reference symbols transmitted by an antenna port benefit from a very low allocated power then the channel estimation is very noisy. Main characteristics of the invention The subject of the invention is a communication method intended to be implemented by a base station of a MU-MIMO system with ^^^^ ≥ 2 user equipments, the system comprising ^^^^ ≥ 2 transmit antennas, at least ^^^^ antenna ports and ^^^^ ≥ 2 receive antennas distributed in ^^^^ ^^^^ ^^^^ ≥1 receiving antennas per user equipment, ^^^^ = ∑ ^^^^ ^^^^^^^^=1 ^^^^ ^^^^ , using transmission time-frequency radio resource elements allocated to at least one antenna port allocated to the user equipment ^^^^, among the ^^^^ antenna ports, 1 ≤ ^^^^ ≤ ^^^^, and dedicated to communication between the base station and the user equipment ^^^^, such that: communication control information between the base station and the ^^^^ user equipments, transmitted by the base station, indicates, for a user equipment ^^^^, at least one power ratio per time-frequency radio resource element between reference symbols and data transmitted to this user equipment ^^^^ for a given antenna port.The invention further relates to a communication method intended to be implemented by a user equipment taken from among ^^^^ user equipments of a MU-MIMO system with ^^^^ ≥ 2 user equipments and a base station, the system comprising ^^^^ ≥ 2 transmitting antennas, ^^^^ antenna ports and ^^^^ ≥ 2 receiving antennas distributed in ^^^^. ^^ ^^ ^ ^ ^^ ≥ 1 receiving antennas per user equipment, ^^^^ = ∑ ^ ^ ^ ^ ^ ^ ^ ^ =1^^^^ ^^ ^^ ^ ^ ^^, using transmission time-frequency radio resource elements allocated to at least one antenna port assigned to the user equipment ^^^^, among the ^^^^ antenna ports, 1 ≤ ^^^^ ≤ ^^^^, and dedicated to the communication between the base station and the user equipment ^^^^, such that: - control information for the communication between the base station and the user equipment, transmitted by the base station, indicates at least one power ratio per time-frequency radio resource element between reference symbols and data transmitted to this user equipment ^^^^ for a given antenna port. The invention further relates to a communication method intended for a MU-MIMO system with ^^^^ ≥ 2 user equipments, the system comprising ^^^^ ≥ 2 transmitting antennas, at least ^^^^ antenna ports and ^^^^ ≥ 2 receiving antennas distributed in ^^^^ ^^ ^^ ^ ^ ^^≥ 1 receiving antennas per user equipment, ^^^^ = ∑ ^ ^ ^ ^ ^ ^ ^ ^ =1^^^^ ^^ ^^ ^ ^ ^^ , that the power allocation distinguishes between power allocated to the data and power allocated to the reference symbols intended for one of the user equipments and takes into account a maximum power per transmitting antenna. The invention further relates to an access point comprising ^^^^ transmitting antennas, at least ^^^^ antenna ports, a transmitter, a receiver, a computer, such that the transmitter is capable of transmitting: - data to ^^^^ ≥ 2 user equipments, - control information indicating radio time frequency transmission resource elements allocated to at least one antenna port, among the ^^^^ antenna ports, assigned to a user equipment ^^^^, , 1 ≤ ^^^^ ≤ ^^^^, - via a control channel dedicated to the user equipment ^^^^, at least one power ratio per time frequency resource element between reference symbols and data transmitted to this user equipment ^^^^ for a given antenna port.The invention further relates to a telecommunications terminal comprising. ≥ 1 receiving antennas, a receiver, such that the receiver is capable of receiving: - reference symbols transmitted by an access point having at least ^^^^ transmitting antenna ports, - control information indicating transmission time-frequency radio resource elements allocated to at least one antenna port allocated to the terminal among the ^^^^ antenna ports, transmitted by the access point, - via a control channel dedicated to this terminal, at least one power ratio per time-frequency resource element, between reference symbols and data transmitted to this terminal for a given antenna port, transmitted by the access point. The invention further relates to a computer program on an information medium, said program comprising program instructions adapted to the implementation of a method according to the invention when said program is loaded and executed in a terminal or an access point.The invention further relates to an information medium comprising program instructions adapted to the implementation of a method according to the invention, when said program is loaded and executed in a terminal or an access point. The invention further relates to a digital signal received by a terminal, comprising reference symbols transmitted by an access point having at least ^^^^ antenna ports, control information indicating at least one power ratio per radio resource element time frequency transmission allocated to at least one antenna port allocated to the terminal among the ^^^^ antenna ports, between reference symbols and data transmitted to this terminal for a given antenna port. In the case of a MU-MIMO system, there is an overlap between users between the allocated time frequency resource elements even if the allocated ports are different between the users. User u benefits from at least one antenna port.Each user u among the U simultaneously scheduled users can benefit from one or more antenna ports. The ν. u ≥ 1 transmit antenna ports assigned to a user are distinct from the transmit antenna ports assigned to other users. The ν = ∑U u =1 ν uantenna ports correspond to inputs of a pre-coder whose M outputs feed the M transmit antennas of the MU-MIMO system. And the pre-coding applied to the reference symbols received by a user equipment is the same as that applied to the data intended for this same user equipment. According to the method, whether or not the data benefit from a power different from that of the reference symbols for the same antenna port, the user equipment u uses the power ratio received for an antenna port to correct the estimation of the pre-coded channel made from the reference symbols by weighting this estimation with the received ratio. A user equipment can thus estimate the pre-coded transmission channel, i.e., which includes the pre-coding, by exploiting the received DMRS, in good conditions, without it being necessary to transmit the pre-coder or information on the choice of this pre-coder.Indeed, the transmission of the power ratio per resource element between reference symbols and data for the same antenna port makes it possible to perform, in reception, a channel estimation independent of the power allocated to the data transmission channel. The pre-coding used in transmission can vary dynamically, i.e. at the rate of sending information on the control channel, the sending of the power ratios follows the same dynamics, i.e., it occurs at each transmission time interval. In particular, the invention relates to the optimization of power allocated per antenna port with a power constraint per antenna knowing the pre-coding ^^^^ by maximizing the dual function of the Lagrangian with an iterative “gradient descend” type algorithm. This approach significantly simplifies the calculations to be carried out by iteration compared to the state of the art.According to one embodiment, the user equipment ^^^^ receives the control information via a control channel dedicated to this equipment. The control channel is for example the PDCCH channel according to the 5G standard of the 3GPP. According to one embodiment of the invention, the control information further indicates a configuration of the reference symbols associated with the antenna ports. According to one embodiment of the invention, the control information indicates as many power ratios as antenna ports allocated to the user equipment ^^^^.According to one embodiment of the invention, the configuration is such that the antenna ports are grouped to form ^^^^^^^^ ^^^^ ^^^^groups such that the reference symbols are spatially code multiplexed between the antenna ports of the same group and according to which the control channel dedicated to the user equipment ^^^^ indicates a unique power ratio for each set of antenna ports belonging to the same group and allocated to the user equipment ^^^^. According to one embodiment of the invention, the method further comprising a use of the same pre-coding matrix to pre-code the data and the reference symbols to be transmitted to the user equipment ^^^^ and the composition of which depends on an estimation of the channels between the base station and each of the ^^^^ user equipment, the set of channels forming a global channel called MU-MIMO.According to one embodiment of the invention, the precoding matrix is ​​based on a pseudo-inversion of the MU-MIMO channel. According to one embodiment of the invention, the method further comprises a singular value decomposition of the matrix ^^^^. ^^^^ of the channel between the base station and each user equipment ^^^^ such that, ^^^^ ^^^^ = ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ † ^ ^^^ ∈ ℂ ^^^^ ^^^^× ^^^^ with ^^^^ ^^^^ ∈ ℂ ^ ^^^^ ^^^^ ^^^^ ^^^ ^^^^× ^^^^ ^^^^the matrix containing the set of so-called output eigenvectors, ^^^^ ^^^^ ∈ ℂ ^^^^× ^^^^ ^^^^ ^^^^ the matrix containing the set of so-called input eigenvectors and ^^^^ ^^^^ = ∈ ℂ ^^^^ ^^^^× ^^^^ ^^^^ ^^^^ ^^^^a square matrix containing the positive real singular values ​​arranged on the diagonal coefficients such that , the pseudo inversion being carried out on the matrix ^^^^ = matrix containing the set of so-called input eigenvectors of the MU-MIMO channel. According to one embodiment of the invention, the pre-coding matrix is ​​based on a regularized version of the inversion of the MU-MIMO channel. According to an embodiment of the invention, further comprising a determination of a power allocated to the data allocated to antenna ports and intended for the user ^^^^ to maximize a sum of the user rates, under the constraint of a maximum power per transmitting antenna, by alternating between a maximization of a Lagrangian ^^^^ with respect to the power matrix ^^^^ for a given value of ^^^^ and then, after an update of the value of the vector ^^^^ taking into account its gradient, a maximization of the Lagrangian ^^^^ with respect to ^^^^, with ^^^^ =[µ1, … , µ ^^^^] vector of the Lagrangian multipliers corresponding to the ^^^^ power constraints per antenna.According to one embodiment of the invention, the determination of a power allocated to the data also takes into account an EMF (for "ElectroMagnetic Field" in English) constraint at least one point in space defined by a distance from the base station. This mode makes it possible to comply with a dual constraint of electromagnetic exposure and power per antenna. According to one embodiment of the invention, the data is transmitted via a downlink data channel PDSCH of a 5G access network.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 a telecommunications system, [Fig 2] Figure 2 is a very generic diagram of a baseband architecture of a transmitter described in relation to the prior art, [Fig 3] Figure 3 is a diagram of a time-frequency grid of the resource elements described in relation to the prior art, [Fig 4] Figure 4 is a diagram illustrating different configurations of the grids associated with the antenna ports, [Fig 5] Figure 5 is a flowchart of an embodiment of a method according to the invention, [Fig 6] Figure 6 is a diagram of an embodiment of an access point according to the invention, [Fig 7] Figure 7 is a diagram illustrating a terminal according to the invention.Description of particular embodiments The invention is placed in the context of a multi-user MIMO communication system illustrated by Figure 1 already described in relation to the prior art. The MIMO system considered comprises at least one access point, called base station in cellular systems, and ^^^^ ≥ ^^^^ terminals, those of the users. Such a transmission system SYS comprises a transmitter EM and U receivers ^^^^ ^^^^1 … ^^^^ ^^^^ ^^^^ … ^^^^ ^^^^ ^^^^, in communication with the transmitter via a global channel CH between the transmitting antennas and the receiving antennas. ^^^^ is the number of receivers (also called “user equipment, terminals or users”) and ^^^^ is an integer between 1 and ^^^^ which is used to identify a receiver.For the rest, we designate a given receiver by its index (1, …, ^^^^, …, ^^^^), or by the reference RXi (example: ^^^^ ^^^^1, …, ^^^^ ^^^^ ^^^^, …, ^^^^ ^^^^ ^^^^ where 1… ^^^^… ^^^^ is the receiver index). The EM transmitter includes ^^^^ transmitting antennas ANT_E ( ^^^^ > 1), which can interfere with each other. In the same way, each receiver ^^^^ includes ^^^^. ^^ ^^ ^ ^ ^^ ANT_R receiving antennas ( ^^^^ ^^ ^^ ^ ^ ^^ ≥ 1), which can interfere with each other. The global channel CH can be described by a matrix ^^^^ of dimension ^^^^ × ^^^^ with ^^^^ = ^^^^ ^^^^ ^^^^. By applying appropriate pre-coding ^^^^, the transmitter can transmit data to multiple receivers on the same time-frequency resources while limiting interference at reception. In other words, the SYS transmission system is of the multi-user MIMO type. The pre-coding matrix ^^^^ realizes a virtualization of the ^^^^ transmitting antennas into ^^^^ antenna ports. The data vector intended for the user ^^^^ before pre-coding is of size ^^^^ ^^^^ i.e. the data before user pre-coding ^^^^ is spread over ^^^^ ^^^^ spatial layers. The pre-coding per user is described by a matrix of size ^^^^ × ^^^^ ^^^^ that is to say of ^^^^ lines and ^^^^ ^^^^ columns. The number of spatial layers that a receiver ^^^^ can receive cannot exceed min( ^^^^ ^^ ^^ ^ ^ ^^ , ^^^^). In the case of a single receiving antenna at the receiver ^^^^, ^^^^^^ ^^ ^ ^ ^^ = 1, it can only receive one spatial layer. The pre-coding ^^^^, for all users, is described by a matrix of size ^^^^ × ^^^^. The transmitter transmits reference symbols to each of the receivers using the same antenna port(s) as those used for the data intended for this receiver, i.e., these reference symbols are therefore pre-coded like the data using the same pre-coding. The pre-coding ^^^^ is described by a matrix of size ^^^^ × ^^^^, i.e. ^^^^ rows and ^^^^ columns, which can be written: The reference symbols transmitted to the different receivers are distributed in the time-frequency planes (grids) associated respectively with the antenna ports according to a specific configuration. The reference of this configuration is transmitted to the receivers via a protocol associated with the RRC layer and in a semi-static manner, that is to say on a time scale much higher than the scheduling of a receiving equipment which is done on the scale of an elementary time, called TTI. It is possible to distinguish different configurations of the DMRS symbols which define CDM (Code Division Multiplexing) groups associated with a number of antenna ports. Figure 4 illustrates the concept of configuration by CDM groups for the 5G standard. Each time-frequency grid whose structure corresponds to that of Figure 3 corresponds to a spatial layer or an antenna port.Whatever the configuration of the groups, when a resource element RE of a grid carries a reference symbol then there can be no data transmission for this same resource element on any of the grids (the power for data is therefore zero for this resource element for each of the grids), there is therefore no spatial interference between DMRS reference symbols and data. But, for this same resource element RE there can be a DMRS reference symbol on one or more other grids. In this case, to avoid interference between DMRS reference symbols between several grids, the DMRS reference symbols carried by the same resource element are coded with spreading codes of a code called spatial code which are different between the grids.Since the DMRS reference symbols of a grid can be distributed only in frequency, only in time or in time and frequency, the spreading code has a frequency dimension, or a time dimension or a frequency dimension and a time dimension. The upper part of Figure 4 represents a first example of configuration of the DMRS reference symbols. This configuration defines the CDM groups 0, 1 and 2 for six antenna ports, 1000-1005, when the DMRS symbols are simple (distributed over a single OFDM symbol time) and such that for a grid the DMRS symbols are grouped by two and occupy two RE resource elements along the frequency axis. Between two grids, i.e., two ports, of the same group the DMRS symbols occupy the same RE resource elements and are therefore coded differently with a spatial code so that the receiver can distinguish the different ports.Therefore, within the same group and between two ports, the DMRS symbols are orthogonal to each other due to the spatial code. Between the grids of two successive groups, for example between the CDM 0 and CDM 1 groups, the DMRS symbols are offset by two RE resource elements along the frequency axis. Therefore, between the grids of different groups, the DMRS symbols are orthogonal to each other in frequency. The lower part of Figure 4 represents a second example of configuration of the DMRS reference symbols. This configuration defines the CDM groups 0, 1 and 2 for twelve antenna ports, 1000-1011, when the DMRS symbols are double (distributed over two OFDM symbol times) and such that for a grid the DMRS symbols are grouped by four and occupy two RE resource elements along the frequency axis and two RE resource elements along the time axis.Between two grids of the same group, the DMRS symbols occupy the same RE resource elements and are therefore coded differently so that the receiver can distinguish the different ports. Therefore, within the same group and between two ports, the DMRS symbols are orthogonal to each other due to the spatial code. Between the grids of two successive groups, for example between groups CDM 0 and CDM 1, the DMRS symbols are offset by two RE resource elements along the frequency axis. Therefore, between the grids of different groups, the DMRS symbols are orthogonal to each other in frequency. As indicated above, the receiving equipment knows the configuration of the reference symbols, i.e. the maximum number of groups and the structure of these groups (reference symbol spread over one or more symbol times, on one or more frequencies, spatial code used, ports per group).According to the invention, power allocation distinguishes between data and reference symbols. Power allocation to reference symbols. Soit � ^^^^ ( ^^^^ ^^^^ ^^^^ ^^^^)^ ^^^ ^^^^ DMRS power reference symbols ^^^^( ^^^^ ^^^^ ^^^^ ^^^^)^ ^^^ for the antenna port ^^^^ and therefore for the estimation of the corresponding precoded channel ^^^^ ^^^^, with ^^^^ ∈ {1, … , ^^^^} the index of the resource elements carrying these symbols, with ^^^^ the number of reference symbols per antenna port. Depending on the configuration of the DMRS, the power per resource element (EPRE) per antenna, noted ^^^^^^^^ ^^^^ ^^^^, is shared or not between several DMRS symbols. Indeed, several cases are to be considered depending on the configuration of the DMRS: - 1. Case where the DMRS symbols between the different antenna ports are only code multiplexed (in the case of the examples in figure 4, they belong to the same CDM group, for example CDM group 0, that is to say that they are spatially multiplexed within the "CDM group", ie, the reference symbols occupy the same resource elements between the ports and the reference symbols of the same port are coded with a spreading code specific to the port and different from that of another port, the reference symbols of a port are therefore orthogonal in frequency and / or in time with the reference symbols of another port), it comes by taking up the relation (3):. o a. And in the case where the power between the antenna ports is the same, ^^^^( ^^^^ ^^^^ ^^^^ ^^^^)^ ^^^ = ^^^^0 is constant, In this case, according to the method according to the invention, the power allocated per resource element to the DMRS reference symbols for each antenna port ^^^^ which best exploits the power available per antenna ^^^^^^^^ ^^^^ ^^^^ is: In this case, the powers of the DMRS symbols belonging to the same "CDM ( ^^^^ ^ are therefore the same between the antenna ports (but not the ratio ^^ ^^^ ^^^^ ^^^^) group » so^^ ^^^^ ^^^^ ^^^^ ). o b. Or in the case where a signaling constraint imposes the transmission of a single ratio ^^^^ between the energy per resource element (EPRE) of the DMRS reference symbols and the energy per resource element (EPRE) of the data PDSCH channel: In this case, according to the method according to the invention, the power allocated per resource element to the DMRS reference symbols for each antenna port ^^^^ is: - 2. Case where DMRS symbols between different antenna ports are not multiplexed on the same resource element, i.e. the vector ^^^^ ^^^^ ∈ ℂ ^^^^ which is transmitted for the estimation of the pre-coded channel ^^^^ has a s� ( ^^^^ ^^^^ ^^^^ ^^^^)^ ^^^ only non-zero element ^^^^ ^^^^ ^^^^^^^^, ^^^^corresponding to the layer ^^^^, it comes by taking up the relation (3): In this case, according to the method according to the invention, the power allocated per resource element to the DMRS symbols for each antenna port ^^^^ which best exploits the power available per antenna ^^^^^^^^ ^^^^ ^^^^ is: - 3. General case of several “CDM groups”, for example, the first ^^^^1 DMRS symbols belong to a “CDM group” and the remaining ^^^^2 to another “CDM group”, o a. and in the case of an equidistributed allocation, the power allocated per resource element to the DMRS symbols for each antenna port ^^^^ which best exploits the power available per antenna ^^^^^^^^ ^^^^ ^^^^ is, according to the method according to the invention: And o b. or in the case where a signaling constraint imposes the transmission of a single report ^^^^ per “CDM group”, the power allocated per resource element to the DMRS symbols for each antenna port ^^^^ which best exploits the power available per antenna ^^^^^^^^ ^^^^ ^^^^ is, according to the method according to the invention: And From case 3), the allocated power can be determined when there are more than two “CDM groups” associated with a number ^^^^ ^^^^ of ports. In the case of an equidistributed allocation, the power allocated per resource element to the DMRS symbols for each antenna port ^^^^ is, according to the method according to the invention: In the case where a signaling constraint imposes the transmission of a single report ^^^^ per “CDM group”, the power allocated per resource element to the DMRS symbols for each antenna port ^^^^ is, according to the method according to the invention: The pre-coded channel can be expressed in the form of a matrix: And the ^^^^ ème matrix column ^^^^ ^^^^ ^^^^( ^^^^ ^^^^ ^^^^ ^^^^) ^^^^ ^^^^ is noted: ^^^^ ^ ^ ^ ^ ^ ^ ^^ ^^^^ ^^^^ ^^^^. The received signal ^^^^^^^^, ^^^^corresponding to the emission of a DMRS symbol carried by a resource element ^^^^ associated with the spatial layer ^^^^ has the following expression: With ^^^^^^^^, ^^^^the noise at reception associated with the spatial layer ^^^^ and the resource element ^^^^. The estimate ^ � ^^^ ^^^^ of the pre-coded channel ^^^^ ^^^^ can be obtained by multiplying ^^^^^^^^, ^^^^by ^^^^ ^ ∗ ^ ^^, ^^^^ and by "averaging / interpolating" on ^^^^ knowing that the other resource elements ^^^^ ∈ {1, … , ^^^^} of this layer ^^^^ which do not carry DMRS symbols carry data symbols which benefit from a power It then comes that: where ^^^^( ^^^^ ^^^^ ^^^^ ^^^^)^ ^^^ is the DMRS symbol power for the antenna port ^^^^ (carrying the spatial layer ^^^^) while is the data symbol power for antenna port ^^^^, per resource element. DMRS symbols and data symbols carried by antenna port resource elements ^^^^ are intended for the same user ^^^^. The channel estimate ^ � ^^^ ^^^^ associated with the antenna port ^^^^ requires knowledge of ^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^ = � ^^^^ ( ^^^^ ^^^^ ^^^^ ^^^^)^ ^^^ / ^^^^ ^^^^ ^^^^ ^^^^ ^^^^^ since ^ � ^^^ ^^^^ = ^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^ ^ � ^^^ ^^^^ ^^^ .Control information, acquired semi-statically or dynamically via a control channel, for example the PDCCH channel in 4G or 5G, dedicated to the user equipment ^^^^ indicates time-frequency resource elements RE allocated to the user equipment ^^^^. According to the invention, a control channel for data transmission between the transmitter and the user equipment ^^^^ indicates ^^^^ power ratios, ^^^^ / ^^( ^^^^ ^^^^ ^^^^ ^^^^)^ ^^^ ^^^^ ^^ ^^^^ or ^^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^= � ^^^^( ^^^^ ^^^^ ^^^^ ^^^^)^ ^^^ / ^^^^ ^^^^ , per radio resource element RE time frequency, between DMRS reference symbols and data transmitted to the user equipment ^^^^, ^^^^ ^^^^being the number of antenna ports allocated to a data transmission to the user equipment ^^^^. According to the invention, the control information intended for the ^^^^ receivers thus includes ^^^^ quantified power ratios for all spatial layers ^^^^ = 1, … , ^^^^ : Figure 5 very schematically illustrates a method according to the invention implemented by an access point, a base station in the case of a mobile access network. The base station comprises ^^^^ ≥ 2 transmitting antennas and at least ^^^^ antenna ports. The base station implements the communication method 1 to communicate at a given transmission interval (TTI) with ^^^^ user equipment (receivers).2 ≤ ^^^^ ≤ ^^^^. Each user equipment comprises ^^^^ ^^ ^^ ^ ^ ^^ ≥ 1 receiving antennas. The system which includes the base station and the ^^^^ user equipment therefore includes ^^^^ receiving antennas. The base station transmits, to each user equipment ^^^^ among the ^^^^ user equipments, information indicating radio resource elements time frequency transmission allocated to at least one antenna port, taken from among the ^^^^ antenna ports, assigned to the user equipment ^^^^. This transmission is done using a control channel dedicated to each user equipment ^^^^. According to the mobile telecommunications standards published by the 3GPP, for example 4G, 5G, this control channel is the PDCCH channel. And the information is carried by the DCI (Data Control Information) and indicates the radio resource elements RE time frequency for each transmit antenna port allocated to a user.According to method 1, control information dedicated to the user equipment u indicates a ratio ^^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^of powers per resource element RE time frequency between DMRS reference symbols and data transmitted to this user equipment u for a given antenna port ^^^^. For a downlink transmission, the control information is carried by the control channel which is dedicated to a user equipment and which is typically the PDCCH channel. When it receives the DMRS reference symbols associated with an antenna port ^^^^ intended for it, the receiver ^^^^ estimates the pre-coded channel ^. � ^^^ ^ ^ ^ ^ ^ ^ ^^ ^^^^ ^^^^ ^^^^. By exploiting the power ratio(s), ^^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^or� ^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^� 2 , received in the control information according to the invention, the receiver ^^^^ weights the pre-coded channel ^ �^^^ ^ ^ ^ ^ ^ ^ ^^ ^^^^ ^^^^ ^^^^estimated from the reference symbols and thus obtains the pre-coded channel ^ � ^^^ ^^^^ which subsequently allows it to equalize the received data associated with the same antenna port ^^^^. In the case of DMRS reference symbols belonging to different configuration groups, "CDM groups", according to the invention the method can transmit only one power ratio, ^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, per CDM group, per user, in the case where the ratio between the power of the DMRS and the data carried by the same antenna port is the same for all the DMRS ports belonging to a CDM group. Considering for illustrative purposes only a configuration with ^^^^^^^ ^^^^ ^^^^CDM groups, the channel estimation for a receiver ^^^^ from the DMRS symbols is based on a set ^^^^ ^^^^of CDM groups taken from the ^^^^^^^^ ^^^^ ^^^^CDM groups. Each user ^^^^ being mapped to one or more antenna ports, the set ^^^^ ^^^^ indicates the port numbers assigned during transmission to this user ^^^^. The method according to the invention determines the power ratios, ^^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^between the data and the reference symbols for each user ^^^^ and for each port assigned to this user, ^^^^ ∈ ^^^^ ^^^^ . According to one embodiment, the power ratios ^^^^^^^^ ^^^^ ^^^^ ^^^^, ^^^^, ^^^^ ∈ ^^^^ ^^^^ , are quantized, each on a number of bits ^^^^ > 1 (for example four), and are part of the control information transmitted to the receiver ^^^^, for example transmitted in the control channel (PDCCH / DCI) in the downlink. MU-MIMO downlink channel inversion The signal transmitted from the ^^^^ antennas is: With: ^^^^ = the data vector to be transmitted to ^^^^ scheduled receivers simultaneously, at a given transmission interval (TTI), each component of which has a power normalized to one with: ^^^^ ^^^^ ∈ ℂ ^^^^ ^^^^ the data vector intended for the receiver ^^^^ ∈ {1, … , ^^^^} and which is mapped onto ^^^^ ^^^^ spatial layers, ^^^^ = [ ^^^^1^^^^2… ^^^^ ^^^^ … ^^^^ ^^^^ ] ∈ ℂ ^^^^× ^^^^ the precoding matrix where ^^^^ is the total number of spatial layers transmitted ^^^^ = ^^^^ ^^^^ ∈ ℂ ^^^^× ^^^^ ^^^^ the pre-coding associated with the receiver ^^^^, ^^^^ = ^^^^ ^^^^ ^^^^ ^^^^( ^^^^1, ^^^^ ^^^^ ,⋯ , ^^^^ ^^^^ ,⋯ , ^^^^ ^^^^ ) ∈ ℂ ^^^^× ^^^^ the diagonal matrix of power transmitted per antenna port, ^^^^ ^^^^ = ^^^^ ^^^^ ^^^^ ^^^^( ^^^^ ^^^^,1 ,⋯ , ^^^^^^^^, ^^^^ ^^^^ ^ ^^^ ) ∈ ℂ ^^^^× ^^^^ ^^^^the diagonal power matrix associated with the spatial layers on which the reference symbols and data intended for the receiver are mapped ^^^^. received signal ^^^^ ^^^^ ∈ ℂ ^^^ ^^^^ The ^ ^^^^ for a receiver ^^^^ can be written: With: ^^^^ ^^^^ ∈ ℂ ^^^^ ^ ^ ^ ^ ^ ^ ^ ^× ^^^^ the transmission channel from the transmitter to ^^^^ transmitting antennas to the receiver ^^^^ to ^^^^ ^^ ^^ ^ ^ ^^ receiving antennas with ^^^^ ^^ ^^ ^ ^ ^^ < ^^^^, ^^^^ ^^^^ ∈ ℂ ^^^^ ^ ^ ^ ^ ^ ^ ^ ^ the noise vector such that 1 ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ 2 ^ ^^^^^^^ ^^^^ the interference due to signals intended for other receivers ^^^^ ≠ ^^^^, ^^^^ ∈{1, … , ^^^^}. The invention is placed in the context where the ^^^^ receivers are scheduled simultaneously. The signal vector received ^^^^ by the ^^^^ receivers is given by: 1 ^^^^ = ^^^^ ^^^^ ^^^^ 2 ^^^^+ ^^^^ with ^^^^ = [ ^^^^1 ^^^^ , ^^^^ ^ 2 ^^^ , ... , ^^^^ ^ ^ ^ ^ ^ ^ ^ ^ ] ^^^^ ∈ ℂ ^^^^×1 , ^^^^: = ∑ ^ ^ ^ ^ ^ ^ ^ ^ =1^^^^ ^^ ^^ ^ ^ ^^ the total number of receiving antennas, ^^^^ the combined (global) channel matrix ^^^^ = [ ^^^^1^^^^2… ^^^^ ^^^^ ] ^^^^ ∈ ℂ ^^^^× ^^^^ , noise vector such that ^ † ^^^ � ^^^^ ^^^^ � = ^^^^ ^^^^ ^^^^ ^^^^( ^^^^1 ,⋯ , ^^^^ ^^^^ ). Subsequently it is assumed that ^^^^� ^^^^ ^^^^† � = ^^^^ ^^^^ ^^^^ ^^^^( ^^^^1 2 ,⋯ , ^^^^ ^ 2 ^ ^^ ). According to a first embodiment of the invention, the transmitter's knowledge of the MU-MIMO channel (matrix ^^^^ i.e. the channel between the ^^^^ transmitting antennas and the ^^^^ receiving antennas, ^^^^ ∈ ℂ ^^^^× ^^^^ , ^^^^ = ^^^^ ^^ ^^ ^ ^ ^^ is the total number of receiving antennas) is assumed to be perfect, the pre-coding matrix used ^^^^ is the one obtained by pseudo-inversion of the channel (obtained using the so-called Zero Forcing technique) which allows the interference between the ^^^^ spatial layers to be cancelled, i.e., the layers are orthogonal to each other. For a receiver ^^^^, the channel matrix ^^^^ u can be decomposed into singular values ​​(SVD, Singular Value Decomposition) as follows: ^^^^ u = the matrix containing the set of so-called output eigenvectors, ^^^^ ^^^^ ∈ ℂ M× ^^^^ ^^^^ ^^^^ the matrix containing the set of so-called input eigenvectors and Σ ^^^^ = a square matrix containing the values positive real singulars arranged on the diagonal coefficients such that ^^^^ ^^^^,1 ≤ ^^^^ ^^^^,2 ≤ ⋯ ≤ ^^^^^^^^, ^^^^^^^^ ^ ^^^ . The received signal ^^^^ can then be written: Or again: Or again taking into account the composition of the matrix Σ u : According to the first embodiment of a method according to the invention, the Zero Forcing (ZF) technique is applied to the matrix ^^^^ =� ^^^^ ^^^^ † 2 … that is to say on the containing the set of so-called input eigenvectors. Thus, the method performs a pseudo-inverse of this matrix ^^^^ to obtain: ^^^^ ^^^^ ^^^^ = ∈ ℂ M×N. This pseudo-inverse matrix can be expressed in blocks: ^^^^ ^^^^ ^^^^ = [ ^^^^1 ^^^^ ^^^^ ^^^^2 ^^^^ ^^^^ , … , ^^^^ ^ ^ ^ ^^ ^ ^ ^ ^^^^ , … ^^^^ ^ ^^ ^ ^ ^ ^ ^ ^^^^ ] with ^^^^ ^^^^ ^ ^ ^ ^^ ^ ^ ^ ^^^^ ∈ ℂ ^^^^× ^^^^ ^^^^ . The pre-coding applied in MU-MIMO transmission for the data and reference symbols intended for the receiver ^^^^ corresponds to the ^^^^ ^^^^ first columns of ^^^^ ^ ^ ^ ^^ ^ ^ ^ ^^^^ : The combined precoding matrix, corresponding to the global channel, is ^^^^ = [ ^^^^1^^^^2… ^^^^ ^^^^ ] ∈ ℂ ^^^^× ^^^^ where ^^^^ is the total number of spatial layers transmitted ^^^^ = . It is clear that ^^^^ ^^^^ ∈ ℂ ^^^^× ^^^^ is an identity matrix ^^^^ ^^^^ to which was added, at each position initiale (∑ ^ ^^ ^ ^ ^ ^ = ^ 1 − ^^^^ ^^^^ null lines for all ^^^^ ∈ { 1, … , ^^^^ } . The diagonal power matrix ^^^^ = diag( ^^^^1,⋯ , ^^^^U) ∈ ℂ ^^^^× ^^^^ describes the power allocated per spatial layer ^^^^ ∈{1, … , ^^^^} where ^^^^ ^^^^ ∈ ℂ ^^^^ ^^^^× ^^^^ ^^^^ corresponds to the ^^^^ ^^^^ first eigenvalues ​​of ^^^^ ^^^^. To simplify the notations, it is considered that ^^^^ = diag(Q1,⋯ , ^^^^ ^^^^ ). It comes that ^^^^^^^^, ^^^^= ^^^^^^^^( ^^^^)+ ^^^^( ^^^^−1 defining ^^^^ ^^^^) = ∑ ^^^^=1 ^^^^ ^^^^ . Let ^^^^ ^^^^ the signal received by the receiver ^^^^. Le signal where ^^^^ ^^^^ = ^^^^ † ^ ^^^ ^^^^ ^^^^ is a spatially uncorrelated noise vector, i.e. Subsequently, the eigenvalue ^^^^ ^^^^= ^^^^( ^^^^)+ ^^^^ = , ∀( ^^^^, ^^^^ ) ∈ { 1, … , ^^^^ } × {1, … , ^^^^ ^^^^}, is called the eigenvalue associated with the layer ^^^^ ∈ {1, … , ^^^^}. Similarly, the variance ^^^^2^^^^= ^^^^( ^^^^)+ ^^^^ {1, … , ^^^^} × {1, … , ^^^^ ^^^^}, is called the variance of the layer ^^^^ ∈ {1, … , ^^^^}.ZF precoding (pseudo-inversion of the channel) allows to cancel the interference between the different 1 receivers (or, in other words, ZF precoding allows to cancel the term ∑^^^^≠ ^^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^ 2 ^ ^^^ ^^^^ ^^^^ ) in order to obtain ^^^^ ^^^^parallel channels without interference. The noise plus interference, SINR, of the receivers are decorrelated from each other because the receivers are spatially separated due to ZF pre-coding. Thus, according to the first embodiment, with Zero-Forcing pre-coding, the signal-to-noise plus interference ratio, SINR, (Signal-to-Interference-plus-Noise Ratio) of the spatial layer ^^^^ is given by:^ ^^^ Q SINR ^^^^ ^^^^ ^^^^ = ^^^^2 ^^^^ with the eigenvalue corresponding to the spatial layer ^^^^, ^^^^ ^^^^ the power allocated to space ^^^^, ^^^^ ^^ 2 ^ ^ the power of the spatial layer noise ^^^^. In the case where the channel suffers from bad radio conditions (corresponding to eigenvalues � ^^^^ ^^^^† � −1very wide), ZF precoding can lead to low SINR values ​​at reception. However, by simultaneously scheduling in MU-MIMO transmission only receivers in good radio conditions according to a particular embodiment of the invention, the use of ZF precoding remains a high-performance precoding solution. Given the limitations of ZF precoding in high noise (or low SNR) scenarios, according to a second embodiment of the invention, a regularized version of channel inversion, called MMSE (Minimum Mean Square-Error) precoding, is performed, this regularized version shows a significant gain at low SNR and converges towards the performance of ZF precoding at high SNR. MMSE precoding is given by: Since intra-user and inter-user interference can no longer be considered zero at low SNR, MMSE pre-coding attempts to maximize the SINR per spatial layer in reception. Power allocation to data per antenna port Power allocation Q ^^^^ to the data is determined to maximize the sum of the rates per antenna port which define channels orthogonal to each other due to pre-coding, under power constraints per antenna ^^^^ ^^^^ ^^^^ ^^^^: These constraints are also written in the form: According to the first embodiment, ZF pre-coding, the signal-to-noise ratio can be expressed in the form SNR ^^^^ is the eigenvalue corresponding to the spatial layer ^^^^, ^^^^ is the ^^^^ power allocated to the spatial layer ^^^^ and ^^^^ ^^ 2 ^ ^ is the noise power for layer ^^^^. Whatever the precoding ^^^^ = [^^^^1^^^^2… ^^^^ ^^^^ ] ∈ ℂ ^^^^× ^^^^ , for a receiver of the LMMSE type (with a matched whitening filter), the signal-to-noise ratio of the layer ^^^^ ∈ {1, … , ^^^^ ^^^^} can be expressed in the form: ^ effect, the received signal ^^^^ ^^^^ ∈ ℂ ^^^^ ^^^ In e ^^^^ for a receiver ^^^^ can be written: By defining ^^^^ ^^^^ = ^^^^ ^^^^ ^^^^ ^^^^ = [ ^^^^ ^^^^,1 ⋯ ^^^^ ^^^^, ^^^^ ^^^^ ] ∈ ℂ ^^^^ ^^^^ ^^^^× ^^^^ ^^^^, it comes: To solve the problem of optimization under constraints, whatever the pre-coding, the invention uses a Lagrangian defined by: With ^^^^ = [µ1, … , µ ^^^^ ] the vector of Lagrangian multipliers corresponding to the ^^^^ power constraints per antenna. According to the first mode, ZF pre-coding, the Lagangrian can be written in the form: Regardless of the precoding, the dual Lagrange function g is defined by: g( ^^^^) = m ^^a^^x ℒ( ^^^^ , ^^^^)Since the utility function (sum of the flow rates) is convex, minimizing the function g is equivalent to optimizing the utility function. Calculating the vector ^^^^ that minimizes g optimizes the utility function and therefore the flow rate. The method according to the invention maximizes the Lagrangian ^^^^ with respect to the power matrix ^^^^ for a given value of ^^^^, updates the value of the vector ^^^^ by taking into account its gradient and maximizes the Lagrangian ^^^^ with respect to ^^^^. Thus, the method according to the invention alternates between a maximization of the Lagrangian ^^^^ with respect to the power matrix ^^^^ for a given value of ^^^^ and, after an update of the value of the vector ^^^^ by taking into account its gradient, a maximization of the Lagrangian ^^^^ with respect to ^^^^.Repetition of these alternating maximizations according to a particular algorithm allows the method to converge towards the power allocation matrix that meets the constraints on the power per antenna. An implementation of this algorithm according to a first mode, when the pre-coding is of the ZF type, is given in a condensed form in Appendix A and described below. In an initial step, the following variables or parameters are initialized. The vector ^^^^ is initialized to a value ^^^^. ( ^^^^) , ^^^^ = ^^^^ ( ^^^^) = ^^^^ 1× ^^^^ , the power matrix is ​​initialized to ^^^^^^^^× ^^^^, ^^^^ ∗(−1) = ^^^^^^^^× ^^^^, the iteration index is initialized to zero, ^^^^ = 0, the tolerance factor ^^^^ is initialized to a given value, for example ^^^^ = 10 −3 , learning rates ^^^^ ^^^^ corresponding to the Lagrangian multiplier ^^^^ ^^^^ are initialized to a given value, for example ^^^^ ^^^^= 0.2. The function corresponding to the maximization of the Lagrangian with respect to the power matrix ^^^^ for a given value of ^^^^ is noted: ^^^^ ∗ = ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^( ^^^^ , ^^^^) ^ ^^^ The power allocated to the spatial layer ^^^^ ∈ {1, … , ^^^^} corresponds to a maximum of the function therefore: The diagonal matrix ^^^^ ∗ of the allocated powers is given by: ^^^^ ∗ ( ^^^^) = diag( ^^^^1 ∗ ( ^^^^), … , ^^^^ ^ ∗ ^ ^^ ( ^^^^)) (5)As by definition the dual Lagrange function is:g( ^^^^) = m ^^a ^^x ℒ( ^^^^ , ^^^^)then: g( ^^^^) = ℒ( ^^^^ ∗ ( ^^^^) , ^^^^). The method can calculate the initial values ​​of After the initialization step, the flow of the algorithm in Appendix A is as follows. - 1. Increment the index of the current iteration, ^^^^ = ^^^^ + 1, - 2. Given the value ^^^^ ∗(i−1)obtained in the previous iteration, the current value of g ( ^^^^ ) is given by g ( ^^^^ ) = ^^^^� and the gradient with respect to the vector ^^^^ is calculated as follows for all m ∈ {1, … , ^^^^}: - 3. Based on the gradient, the update of each Lagrangian multiplier for all m ∈ {1, … , ^^^^} is given by: with ^^^^ ^^^^ ^^^^ [ 0.1 ] the learning rate for the Lagrangian multiplier ^^^^ ^^^^ , -4. Calculation ∗ according to the equation ^^^^ ( ^^^^) = diag( ^^^^1∗( ^^^^), … , ^^^^ ^ ∗ ^ ^^ ( ^^^^))And reiteration of 1-4 untilAt the last iteration when the difference is less than the threshold ^^^^, the determined matrix ^^^^∗( ^^^^) =diag( ^^^^∗ ∗ ∗1( ^^^^), … , ^^^^ ^^^^( ^^^^)) includes the powers Q ^^^^ = ^^^^ ^^^^( ^^^^) for the data for each antenna port. According to a second mode, when the pre-coding is arbitrary, for example a MMSE type pre-coding, the calculation of ^^^^ ∗ = argmax ℒ( ^^^^ , ^^^^) based on the derivation given by equation (4) requires ^ ^^^ a numerical derivation of the Lagrangian. An implementation is given in condensed form in Appendix B. According to this mode, to obtain the derivative with respect to ^^^^ ^^^^ℒ ( ^^^^ , ^^^^ ) ^ ^^^ of the Lagrangian, ^^^^Q ^^^^ , the method according to the invention follows a gradient descend / ascend type approach which is based on a numerical derivative of^^^^ℒ( ^^^^ , ^^^^)^^^^Q ^^^^assuming that the Lagrangian function is locally convex (around ^^^^ (0) ^ ^^^ ). Power allocation constrained by limit of exposure to electromagnetic fields According to one embodiment of the invention, it takes into account an additional constraint linked to exposure to electromagnetic fields (EMFE Electromagnetic field exposure). The EMFE constraints are considered on a set ^^^^ of points in space, of any shape which does not necessarily correspond to a sphere: the received power ^^^^ ^^^^ at each point ^^^^ ^^^^ ^^^^ must not exceed a value ^^^^ ^^^^ ^^^^^^^^^^ ^^^^^determined by a regulatory text ( ^^^^ ^^^^ ≤ ^^^^ ^^^^ ^^^^ ^^^^^^^^ ^^^^ ^^^^∀ ^^^^ ^^^^ ^^^^). Each point ^^^^ ^^^^ ^^^^ can be identified by a distance to the transmitter. The received power ^^^ ^ ^ ^^^ at a point ^^^^ ^^^^ ^^^^ in space is given by: ^^^^ =� ^^^^ ^^^^ ^^^^ ^^^1 / 2 2 ^ ^^^ ^ ^^^^� with ^^^^ the transmitted data vector ^^^^ = [ ^^^^1 ^^^^ , ^^^^ ^ 2 ^^^ , ... , ^^^^ ^ ^ ^ ^ ^ ^ ^ ^ ] ^^^^ ∈ of which each component has a power normalized to 1, ^^^^ the total number of spatial layers transmitted ^^^^ = ^^^^ ^^^^ ,^^^^ ∈ ℂ ^^^^× ^^^^ the diagonal power matrix that describes the power allocated per spatial layer ^^^^ ∈ precoding matrix and ^^^^ ^^^^ ∈ ℂ 1× ^^^^ the vector representing the channel between the transmitter and the point ^^^^. These EMFE constraints are added to the constraints of transmission powers per antenna and the performance maximization problem is now given by: under constraints that: And under constraints that: To solve the constrained optimization problem, the invention uses a Lagrangian defined by: with ^^^^ = [µ1, … , µ ^^^^ , µ ^^^^+1 , … , µ^^^^+| ^^^^|] the vector of Lagrangian multipliers whose first ^^^^ elements correspond to the ^^^^ power constraints per antenna and the last | ^^^^| elements correspond to the | ^^^^ | EMFE constraints. According to this embodiment and with ZF pre-coding, the Lagrangian becomes: The algorithm described for the first embodiment can be adapted by considering all the constraints: transmission power per antenna and EMF constraints on the different points ^^^^ of the space. Thus, at iteration ^^^^, the calculation of the gradients ^^^^ ( ^^^^) ^ ^^^ for ^^^^ ∈ { ^^^^, … , ^^^^} corresponding to the antenna transmission power constraints is that given by expression (6) and the calculation of the gradients ^^^^ ( ^^^^) ^^^^ for ^^^^ ∈ { ^^^^ + ^^^^, … , ^^^^ + | ^^^^ |} corresponding to the EMFE constraints on the different points ^^^^ of the space is given by the following expression: Thus, according to this embodiment of the invention, the powers Q ^^^^determined according to the method respect the power constraint per antenna and are such that the power received at any point ^^^^ ^^^^ ^^^^ does not exceed the regulatory EMFE constraint. Figure 6 is a diagram of an embodiment of an access point according to the invention in the context of a 4G or 5G type telecommunications system. The access point PA comprises ^^^^ transmitting antennas ANT_E, at least ^^^^ antenna ports, a transmitter EM1, a receiver RE1, a memory MEM1 comprising a buffer memory, a computer (microprocessor) µP1 whose instructions allow the implementation of a telecommunications method 1 according to the invention. At initialization, the code instructions of the program Pg1 are for example loaded into the buffer memory MEM1 before being executed by the microprocessor µP1. The µP1 microprocessor controls the various components of the access point: the EM1 transmitter and the RE1 receiver.The access point PA further comprises a transmission chain which generally comprises at least a COD channel coding of input data DATA, a MIMO coding and an OFDM multi-carrier modulation to generate TBu data packets mapped to the time-frequency resource grids of the antenna ports respectively assigned to the user equipments ^^^^ (terminals). The transmitter EM1 makes it possible to transmit these TBu data packets to the user equipments ^^^^ via a PDSCH data channel. The transmitter EM1 further makes it possible to transmit: - DMRS reference symbols, - control information indicating ^^^^. ^^^^ antenna ports, among the ^^^^ antenna ports, allocated to a transmission of data to the user equipment ^^^^ and identifying resource elements RE time frequency transmission allocated to the ^^^^ ^^^^antenna ports, according to semi-static (RRC) and / or dynamic mechanisms via a PDCCH control channel dedicated to the user equipment ^^^^, - a power ratio ^^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^per time-frequency resource element RE, between DMRS reference symbols and data transmitted to this user equipment ^^^^, for a given antenna port ^^^^, this (or these) ratio(s) being transported by the PDCCH control channel dedicated to the user equipment ^^^^ . The receiver RE1 makes it possible to receive DMRS reference symbols transmitted by the terminals to estimate the uplink channel of each of the terminals for the demodulation of the data received by the receiver RE1.By executing the instructions, the microprocessor µP1 controls the transmitter EM1 to transmit control information indicating transmission time frequency resource elements RE allocated to at least one antenna port assigned to the user equipment ^^^^ among the ^^^^ antenna ports, via semi-static (RRC) and / or dynamic mechanisms (via a PDCCH control channel dedicated per user equipment ^^^^), and so that the PDCCH control channel dedicated to the user equipment u indicates at least one power ratio ^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^per time frequency resource element RE between DMRS reference symbols and data transmitted to this user equipment ^^^^ by the access point, for a given antenna port ^^^^. The simplified structure of an embodiment of a terminal according to the invention capable of implementing a reception method according to the invention is illustrated by figure 7. The terminal UE ^^^^ comprises. ≥ 1 receiving antennas RXu, a receiver RE2, a transmitter EM2, a memory MEM2 comprising a buffer memory, a computer (microprocessor) µP2 whose operation is controlled by the execution of a program Pg2 whose instructions allow the implementation of a telecommunications method 2 according to the invention. At initialization, the code instructions of the program Pg2 are for example loaded into the buffer memory MEM2 before being executed by the microprocessor µP2. The microprocessor µP2 controls the various components of the terminal, the receiver RE2 and the transmitter EM2. The receiver RE2 comprises an OFDM / MIMO / COD reception chain -1which performs the reverse operations of the access point's transmission chain to receive one or more TBu data packets transmitted by this access point via a PDSCH data transmission channel. The RE2 receiver also makes it possible to receive: - DMRS reference symbols transmitted by the access point, - control information indicating ^^^^ ^^^^ antenna ports, among the ^^^^ antenna ports, allocated to a transmission of data to the user equipment ^^^^ and identifying resource elements RE time frequency transmission allocated to the ^^^^ ^^^^antenna ports, according to semi-static (RRC) and / or dynamic mechanisms via a PDCCH control channel dedicated to the user equipment ^^^^, - at least one power report ^^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^per time-frequency RE resource element, between DMRS reference symbols and data transmitted to this user equipment ^^^^ per antenna port ^^^^, this or these reports being transported by the PDCCH control channel dedicated to the user equipment ^^^^ . The EM2 transmitter allows: - to transmit DMRS reference symbols.Thus, by executing the instructions, the microprocessor µP2 controls the receiver RE2 so that it receives, from the DMRS reference symbols, control information indicating transmission time frequency RE resource elements allocated to at least one antenna port allocated to this user equipment among the ^^^^ antenna ports as well as at least one power ratio ^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^per RE time frequency resource element between DMRS reference symbols and data transmitted by antenna port ^^^^ to this user equipment ^^^^.By executing the instructions, the microprocessor µP2 determines a first estimate of the pre-coded MU-MIMO channel by exploiting the received DMRS reference symbols, for an antenna port ^^^^ assigned to this user, and weights this first estimate with the power ratio ^^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^to obtain an estimate of the pre-coded channel of the TBu data intended for this user ^^^^ and received by the receiver RE2. The power control of the reference signals for the channel estimation at the receiver makes it possible to have a channel estimation quality independent of the power allocated to the data per spatial layer. This power control strategy requires transmitting from the transmitter to the receiver ^^^^ power ratios, ^^^^ ≤ ^^^^ ^^^^ ^^^^ ( ^^^^, ^^^^) being the number of spatial layers selected for transmissions to the ^^^^ user equipments.Accordingly, the invention also applies to one or more computer programs, in particular a computer program on or in an information medium, adapted to implement the invention. This program may use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code such as in a partially compiled form, or in any other form desirable for implementing a method according to the invention. The information medium may be any entity or device capable of storing the program. For example, the medium may comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a USB key or a hard disk.On the other hand, the information carrier may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention may in particular be downloaded from a network such as the Internet. Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question. According to techniques known to those skilled in the art, the transmitter, in order to calculate the pre-coder and the power ratios between the DMRS and the data, must know the transmitter-to-receiver channel in advance. This knowledge may be based on the principle of reciprocity in TDD. The transmitter estimates the receiver-to-transmitter channel using reference signals transmitted by the receiver.Channel reciprocity allows the transmitter-to-receiver channel to be deduced from the estimated receiver-to-transmitter channel. In the downstream direction, the reference signals emitted by the receiver (UE terminal) for the acquisition of the channel at transmission by reciprocity are the SRS while in the upstream direction the reference signals used are the CSI-RS (emitted by the access point). Another approach can be based on the return, from the receiver, of the “quantized” channel (codebook based MIMO) transmitter to receiver. For example, in the downstream direction, the receiver (UE terminal) can estimate this channel using the CSI-RS transmitted by the transmitter (access point PA).

[0002] Appendix A MU-MIMO Power Allocation Algorithm - 1. Initializing Learning Rates ^^^^ ^^^^ ^^^^ [ 0.1 ] ∀ ^^^^ = 1, … , ^^^^ for the ^^^^ constraints, for example ^^^^ ^^^^ = - 2. Initialization of the tolerance threshold ^^^^, for example ^^^^ = 10−3 , - 3. Initialization of multipliers ^^^^ Lagrangian to an initial value ^^^^ (0) , for example ^^^^ (0) = 1 1× ^^^^ , - 4. Initialization of the matrix = ^^^^^^^^× ^^^^, - 5. Initialization of the iteration index, ^^^^ = 0, - - do: - 8. ^^^^ = ^^^^ + 1, - 9. Calculation of the derivative (gradient) for all ^^^^ = 1, … , ^^^^ : - 10. Based on the gradient, calculation of the updates of the values ​​of the Lagrangian multipliers for all ^^^^ = 1, … , ^^^^: with ^^^^ ^^^^ the learning rate for the Lagrangian multiplier ^^^^ ^^^^ , - diag� ^^^^ ∗( ^^^^) , … , ^^^ ∗( ^^^^) 1 ^ ^^^^ � - 12. End of while, - 13. Supply of ^^^^ ∗ .

[0003] Appendix B MU-MIMO Power Allocation Algorithm for Any Precoding ^^^^ - 1. Initialization of Learning Rates ^^^^ ^^^^ ^^^^ [0,1] ∀ ^^^^ = 1, … , ^^^^, ^^^^^^^^ ^^^^ [0,1] ∀ ^^^^ = 1, … , for the ^^^^ constraints, for example ^^^^ ^^^^ = 0.2,∀ ^^^^ = 1, … , ^^^^, - 2. Initialization of the tolerance threshold ^^^^, for example ^^^^ = 10 −3 , - 3. Initialization of multipliers ^^^^ Lagrangian to an initial value ^^^^ (0) , For example - 4. Initialization of the matrix = ^^^^^^^^× ^^^^, - 5. Initialization ∀ ^^^^ ∈ { 1, … ^^^^ } , - 6. Initialization of the iteration index, ^^^^ = 0, - 7. As long - 8. ^^^^ = ^^^^ + 1, - 9. Calculation of the numerical derivative ^^^^ ( ^^^^) ^ ^^^ from the Lagangrian ℒ to the value ^^^^ ^^^^ for all ^^^^ =1, … , ^^^^ : - 10. Calculation of the derivative ∆ ( ^^^^) ^ ^^^ for all ^^^^ = 1, … , ^^^^ : - 11. Based on the gradient, calculation of updates, of the values ​​of the Lagrangian multipliers: and power: ^^^^ ( ^^^^) ^^^^ = ^^^^ ( ^^^^−1) ^ ^^^ + ^^^^ ^^^^ ^^^^ ( ^^^^) ^ ^^^ ,∀ ^^^^ = 1, … , ^^^^, - 12. End of while, - 13. Supply of ^^^^.

Claims

CLAIMS 1. Communication method (1) intended to be implemented by a base station of a MU-MIMO system with ^^^^ ≥ 2 user equipments (UE), the system comprising ^^^^ ≥ 2 transmitting antennas, at least ^^^^ antenna ports and ^^^^ ≥ 2 receiving antennas distributed in ^^^^ ^^ ^^ ^ ^ ^^ ≥ 1 receiving antennas per user equipment, ^^^^ = ∑ ^ ^ ^ ^ ^ ^ ^ ^ =1^^^^ ^^ ^^ ^ ^ ^^, using radio time-frequency transmission resource elements (RE) allocated to at least one antenna port assigned to the user equipment ^^^^, among the ^^^^ antenna ports, 1 ≤ ^^^^ ≤ ^^^^, and dedicated to the communication between the base station and the user equipment ^^^^, characterized in that: - control information of the communication between the base station and the ^^^^ user equipment (UE), transmitted by the base station, indicates, for a user equipment ^^^^, at least one power ratio ( ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^) per radio time frequency resource element (RE) between reference symbols (DMRS) and data transmitted to this user equipment ^^^^ for a given antenna port ( ^^^^).

2. Communication method (1) according to claim 1, according to which the control information is transmitted to the user equipment ^^^^ via a control channel (PDCCH) dedicated to this user equipment ^^^^.

3. Communication method (1) according to one of claims 1 and 2, according to which the control information further indicates a configuration of the reference symbols associated with the antenna ports.

4. Communication method (1) according to one of claims 1 to 3, according to which the control information, for the user equipment ^^^^, indicates as many power ratios as antenna ports allocated to the user equipment ^^^^. 5.A communication method (1) according to claim 3, wherein the configuration is such that the antenna ports are grouped to form ^^^^. ^^^^ ^^^^ ^^^^groups such that the reference symbols are spatially code multiplexed between the antenna ports of the same group and according to which the control channel (PDCCH) dedicated to the user equipment ^^^^ indicates a unique power ratio for each set of antenna ports belonging to the same group and allocated to the user equipment ^^^^.

6. Communication method (1) according to one of claims 1 to 5, further comprising a use of the same pre-coding matrix ( ^^^^) to pre-code the data and the reference symbols to be transmitted to the user equipment ^^^^ and the composition of which depends on an estimation of the channels between the base station and each of the ^^^^ user equipment, the set of channels forming a global channel called MU-MIMO.

7. Communication method (1) according to claim 6, such that the pre-coding matrix ( ^^^^) is based on a pseudo-inversion of the MU-MIMO channel.

8. Communication method (1) according to the preceding claim, further comprising a singular value decomposition of the matrix ^^^^ ^^^^ of the channel between the base station and each user equipment ^^^^ such that, ^^^^ ^^^^ ^ ^^^ = ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ † ^ ^^^ ∈ ℂ ^^^^ ^^^^× ^^^^ with ^^^^ ^^^^ ∈ ℂ ^^^^ ^^^^ ^^^^ ^^^^× ^^^^ ^^^^ the matrix containing the set of so-called output eigenvectors, ^^^^ ^^^^ ∈ ℂ M× ^^^^ ^^^^ ^^^^ the matrix c ontenant l’ensemble des vecteurs propres dits d’entrée et Σ ^^^^ = diag( ^^^^ ^^^^,1 , … , ℂ ^^^^ ^^^^ ^^^^ ^^^^× ^^^^ ^^^^ a square matrix containing the positive real singular values ​​arranged on the diagonal coefficients such that ^^^^ ^^^^,1 ≤ ^^^^ ^^^^,2 ≤ ⋯ ≤ ^^^^ ^^^^, ^^^^ ^^^^ ^ ^^^ , the pseudo inversion being performed on the matrix ^^^^ = said matrix containing the set of proper inputs of the MU-MIMO channel.

9. Communication method (1) according to claim 6, such that the pre-coding matrix (^^^^) is based on a regularized version of the inversion of the MU-MIMO channel.

10. Communication method (1) according to one of claims 1 to 9, further comprising a determination of an allocated power (Q ^^^^ ) to the data allocated to antenna ports and intended for the user ^^^^ to maximize a sum of the users' throughputs, subject to a maximum power constraint per transmitting antenna, by alternating between a maximization of a Lagrangian ^^^^ with respect to the power matrix ^^^^ for a given value of ^^^^ and then, after an update of the value of the vector ^^^^ taking into account its gradient, a maximization of the Lagrangian ^^^^ with respect to ^^^^, with ^^^^ = [µ1, … , µ ^^^^] vector of Lagrangian multipliers corresponding to the ^^^^ power constraints per antenna.

11. Communication method (1) according to claim 10, such as determining an allocated power (Q ^^^^ ) to the data further takes into account an EMF constraint, ElectroMagneticField, at at least one point in space defined by a distance to the base station.

12. Communication method (2) intended to be implemented by a user equipment taken from among ^^^^ user equipments (UE) of a MU-MIMO system with ^^^^ ≥ 2 user equipments (UE) and a base station, the system comprising ^^^^ ≥ 2 transmitting antennas, ^^^^ antenna ports and ^^^^ ≥ 2 receiving antennas distributed in ^^^^ ^^ ^^ ^ ^ ^^ ≥ 1 receiving antennas per user equipment, ^^^^ = ∑ ^ ^ ^ ^ ^ ^ ^ ^ =1^^^^ ^^ ^^ ^ ^ ^^, using radio time-frequency transmission resource elements (RE) allocated to at least one antenna port assigned to the user equipment ^^^^, among the ^^^^ antenna ports, 1 ≤ ^^^^ ≤ ^^^^, and dedicated to the communication between the base station and the user equipment ^^^^ characterized in that it comprises a step of receiving information for controlling the communication between the base station and the user equipment (UE), transmitted by the base station, said information indicating at least one power ratio per element of resource (RE) radio time frequency between reference symbols (DMRS) and data transmitted to this user equipment ^^^^ for a given antenna port ( ^^^^).

13. Communication method (1) for a MU-MIMO system with ^^^^ ≥ 2 user equipments (UE), the system comprising ^^^^ ≥ 2 transmitting antennas, at least ^^^^ antenna ports and ^^^^ ≥ 2 receiving antennas distributed in ≥ 1 receiving antennas per user equipment, ^^^^ = characterized in that the power allocation distinguishes between power allocated to data and power allocated to reference symbols intended for one of the user equipments and takes into account a maximum power per transmitting antenna.

14. Access point (AP) comprising ^^^^ transmitting antennas (ANT_E), at least ^^^^ antenna ports, a transmitter (EM1), a receiver (RE1), a computer (µP1), such that the transmitter (EM1) is able to transmit: - data (TBu) to ^^^^ ≥ 2 user equipments, - control information indicating radio time frequency transmission resource elements (RE) allocated to at least one antenna port, among the ^^^^ antenna ports, assigned to a user equipment ^^^^, , 1 ≤ ^^^^ ≤ ^^^^, characterized in that the transmitter (EM1) is further able to transmit: - via a control channel (PDCCH) dedicated to the user equipment ^^^^, at least one power report ( ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^) per resource element (RE) time frequency between reference symbols (DMRS) and data transmitted to this user equipment ^^^^ for a given antenna port ( ^^^^).

15. Telecommunications terminal (UEu) comprising ^^^^ ^^ ^^ ^ ^ ^^ ≥ 1 receiving antennas (RXu), a receiver (RE2), such that the receiver (RE2) is able to receive: - reference symbols (DMRS) transmitted by an access point (PA) having at least ^^^^ transmitting antenna ports, - control information indicating radio time frequency transmission resource elements (RE) allocated to at least one antenna port assigned to the terminal among the ^^^^ antenna ports, transmitted by the access point, characterized in that the receiver (RE2) is further able to receive: - via a control channel (PDCCH) dedicated to this terminal, at least one power report ( ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^) per resource element (RE) time frequency, between reference symbols (DMRS) and data transmitted to this terminal for a given antenna port (l), transmitted by the access point.

16. Digital signal received by a terminal, comprising reference symbols (DMRS) transmitted by an access point (AP) having at least ^^^^ antenna ports, control information indicating at least one power ratio ( ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^, ^^^^ ) per radio resource element (RE) time transmission frequency allocated to at least one antenna port assigned to the terminal among the ^^^^ antenna ports, between reference symbols (DMRS) and data transmitted to this terminal for a given antenna port ( ^^^^).

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