Receiving and sending processes, user equipment, configured access point, and digital signal

Abstract

Receiving and transmitting methods, user equipment, access point and digital signal. The invention relates to a method for receiving by a user device (3) at least one control message transmitted by a multi-antenna access point (2) of a network (NW-5G), wherein said at least one control message comprises, for at least one antenna port among NT≥2 antenna ports of the access point, information representing the maximum energy per resource element admissible by that antenna port for transmitting data signals to the user device. Figure for the abstract: Fig. 4.

Description

Title of the invention: Receiving and sending methods, user equipment, configured access point and digital signal. Prior art

[0001] The invention belongs to the general field of telecommunications.

[0002] It relates more specifically to communications between user equipment and an access point of a telecommunications network equipped with multiple antennas (i.e., an antenna array), each antenna potentially comprising one or more radiating elements (also called antenna elements or AEs). Such an access point is, for example, a base station of a 5G or 6G network, a Wi-Fi access point of a wireless network, etc. The user equipment (or UE) can be any type of terminal such as a smartphone, tablet, connected device, computer, etc.

[0003] MIMO (Multiple Input Multiple Output) technology is now widely used in communication networks, and in particular in 5G-NR (Fifth Generation New Radio) mobile networks. Many mechanisms have been adopted by the 3GPP standard since Release 15 to improve support for MIMO technology, and in particular to facilitate the deployment at base stations (also called gNodeBs) of massive MIMO antennas (also called massive MIMO or simply "massive MIMO"), i.e., antennas integrating a very large number of active antenna elements (typically several dozen or even hundreds of antenna elements).

[0004] A massive MIMO antenna is characterized by a maximum transmission power (or equivalently, a maximum energy per resource element) and by a number of RF (Radio Frequency) chains or transceiver units, more commonly called TXRUs (Transceiver Units). These RF chains are responsible for performing, in particular, digital-to-analog conversions for the downlink and vice versa for the uplink, and include power amplifiers. By way of illustration, antenna arrays deployed in the n78 (3.5 GHz) frequency band at 5G base stations can have up to 64 TXRUs.

[0005] In this MIMO context, the 3GPP specifications introduced the concept of an antenna port (or AP for "Antenna Port"). An antenna port is an abstract concept defined in paragraph 4.4.1 of the 3GPP document TS 38.211 entitled "Technical Specification Group Radio Access Network; NR; Physical channels and Modulation (Release 17) v 17.7.0 (2024-03) states that the channel on which a symbol from an antenna port is transmitted can be deduced from the channel on which another symbol from the same antenna port is transmitted. An AP antenna port of a base station is therefore a logical entity that does not necessarily coincide with a specific physical antenna or with a specific AE radiating element of a physical antenna of the base station, but rather reflects what is visible from the perspective of a UE communicating with the base station. An AP antenna port can effectively correspond to one or more TXRUs, which can themselves correspond to one or more AE radiating elements.

[0006] The notion of an AP antenna port can therefore be modeled by a dual level of virtualization, as illustrated in [Fig. 1]: - A first level of virtualization maps, via a first virtualization matrix denoted Vp, a logical antenna port (AP) of a base station to a group of TXRUs. More precisely, each antenna port (AP) is virtualized onto a different group of TXRUs but with the same cardinality (this is called TXRU partitioning); and - a second level of virtualization defines, via a second virtualization matrix denoted VT, the correspondence between a TXRU and a group of radiating elements AE. In [Fig. 1], NT, NTxru, and Næ respectively denote the number of antenna ports, the number of TXRUs, and the number of radiating elements at the input and / or output of each virtualization level. Consequently, for a given number of TXRUs, the larger the number of antenna ports, the smaller the number of TXRUs per antenna port, with the limit being one antenna port per TXRU. It should also be noted that the number of antenna ports used by the base station to communicate with a UE can vary from one UE to another, depending in particular on its capabilities.

[0007] Figure 2 schematically illustrates part of the baseband processing applied at a 5G network base station to the data to be transmitted downlink on its antenna ports. The double virtualization mentioned above is omitted in this figure for the sake of simplicity.

[0008] The data is first encoded according to one or two streams (for example, in 5G, a single stream can be used for up to ü=4 spatial layers), resulting in at most two encoded data streams or CW codewords, each stream being encoded with a specific channel coding efficiency. These at most two CW encoded data streams are scrambled with an SCR scrambler, and then the scrambled encoded data is mapped onto the constellation of a modulation (for example, QPSK modulation, 16QAM, 64QAM, 256QAM, or 1024QAM) with a mapper C_MAP. The mapper outputs are distributed across U spatial layers by an L_MAP layer mapper. For transmission over a single antenna port, only one spatial layer is used (ü=1). When spatial multiplexing is considered, the number U of spatial layers must be less than or equal to the minimum between the number Nt of antenna ports on the base station and the number NR of receiving antenna ports on the UE (the concept of a UE antenna port can be defined similarly to that of a base station antenna port). In the current state of the 5G standard, the maximum number of antenna ports that can be configured for a UE is NT=32.

[0009] The U spatial layers are then precoded using a PRECOD linear precoder. This precoding involves applying a precoding matrix W of dimensions NT x U to the constellation symbols carried by the U spatial layers (NT denoting the number of antenna ports): in other words, the symbols of the different spatial layers are mapped to the resources of each antenna port. The precoder allows a symbol from a spatial layer to be transmitted from each antenna port of the base station with a phase and amplitude coefficient (derived from the precoding matrix W). A UE (or receiver) can benefit from several spatial layers simultaneously. In the case of codebook-based MIMO transmission, the precoding matrix W is determined using dictionaries or "codebooks" configured at the base station and UE levels.

[0010] For each antenna port used, the pre-coded complex constellation symbols are then mapped to Resource Elements (REs) by a RE_MAP resource mapper. An RE resource element represents the smallest granularity of time-frequency radio resource used for transmissions on the network. The concept of a resource element is described in detail for a 5G network in 3GPP TS 38.211 vl7.7.0, section 4.4.3. A resource element is defined as a physical resource identified for each antenna port p by indices (k,l)p>|J on a time-frequency resource grid, where p denotes a subcarrier spacing configuration, k is an index in the frequency domain, and l refers to a symbol position in the time domain relative to a reference point.For an OFDMA (Orthogonal Frequency Division Multiplexing Access) system, such as that used in 5G networks, such a resource element corresponds to a subcarrier and a symbol time corresponding to the duration of a multicarrier symbol.

[0011] At the output of the RE_MAP resource mapper, the resource elements associated with the different antenna ports are injected into a GEN-OFDM multi-carrier OFDM (Orthogonal Frequency Division Multiplexing) modulator to generate an OFDM symbol. These OFDM symbols feed the antenna ports of the base station.

[0012] In accordance with the 5G standard, the base station transmits NZP CSI-RS reference signals (for "Non-Zero Power Channel State Information Reference Signals"), known to the UE, so that the UE can estimate channel state information (or CSI for "Channel State Information") from the base station's NT antenna ports dedicated to communications with the UE. This estimation of CSI information based on the NZP CSI-RS reference signals is intended to allow the UE to determine a precoder and a modulation and coding scheme (MCS) that maximizes communication performance (typically its spectral efficiency).

[0013] The UE then sends back to the base station a report containing quantified channel status CSI information, described in detail for example in the 3GPP TS 38.214 document entitled "Technical Specification Group Radio Access Network; NR; Physical Layer procedures for data (Release 17)", v 17.7.0 (2023-09) in paragraph 5.2.2. This CSI information includes in particular a channel quality indicator CQI (for "Channel Quality Indicator"), or equivalently the modulation and coding scheme index MCS thus determined by the UE, a rank indicator RI (for "Rank Indicator"), and a precoding matrix indicator PMI (for "Precoding Matrix Indicator") corresponding to the precoder determined by the UE.To limit the resources required for the return path to the base station, 3GPP has standardized two types of dictionaries or "codebooks" for precoder selection, called "Type I" codebook and "enhanced Type II" codebook ("e-Type II" hereafter). These codebooks are detailed for several antenna port and spatial layer configurations in section 5.2.2.2 of 3GPP document TS 38.214 V17.7.0 (2023-09).

[0014] The document by X. Fu et al., entitled "A Tutorial on Downlink Precoder Selection Strategies for 3GPP MIMO Codebooks," IEEE Access, vol. 11, 2023, hereinafter referred to as Dl, describes various strategies that the UE can consider for selecting a Type I or e-Type II precoder. This selection is based on knowledge of the transmission channel and the noise plus interference covariance estimated from measurements performed on resource elements identified as "CSI for Interference Measurement" (CSLIM). These resource elements can, for example, carry zero-power CSI-RS reference signals (or ZP CSI-RS for "Zero Power CSI-RS") allowing such an estimation of interference. The selection also takes into account a constraint on the overall energy PT in transmission per resource element, accumulated over the NT antenna ports of the base station, for example PT=1 in document Dl.

[0015] In practice, the base station is also required to comply with local energy constraints related to its implementation, and more specifically to that of its multiple RF chains (TXRUs) and the power amplifiers that comprise them. These power amplifiers impose energy limitations at the level of each TXRU to ensure their linear operation. Thus, for a number NTXru of identical TXRUs and an overall energy PT per resource element not to be exceeded during communication with a UE, it is desirable that the energy per transmitting resource element reach Pt / Ntxru per TXRU, or equivalently, that the energy per resource element per antenna port reach PT / NT, where NT denotes the number of antenna ports dedicated to communication with the UE.

[0016] The characteristics of the power amplifiers (typically their maximum rated power or their backoff) are implementation choices made by the base station supplier. Furthermore, the absolute value of the total PT energy per resource element accumulated on the base station antenna NTports dedicated to communications with the UE is not necessarily known to the UE (the information elements that allow the UE to obtain this absolute value being, in fact, optional according to the 5G standard).

[0017] However, the inventors have found that in the case of precoders having amplitude-modulated coefficients, such as the eType II precoders defined by the 3GPP standard for 5G networks, taking into account the maximum global energy constraint PT is not sufficient to ensure that such local energy constraints per antenna port are verified.

[0018] Indeed, for U spatial layers, the overall energy constraint is written: 100191

[0020] where Pi denotes the energy per resource element of the spatial layer indexed by l. This constraint takes into account the normalization of the precoder W such that = il with H the conjugate transposed operator and Iv the identity matrix of dimension v. An obvious optimal solution satisfying this constraint (i.e. allowing optimization of reception performance at the UE level) is P; = PT V / , in other words, to have an energy per resource element equally distributed over the ü spatial layers.

[0021] The local constraints mentioned above to be checked at the level of each antenna port APt, t=l,...,NT, of the base station are written:

[0022] yu ,w |2p<£i

[0023] where wtj, t — 1, 2Vy, l = 1, ... 0, denote the coefficients of the precoding matrix W.

[0024] For a Type I codebook, whose coefficients are not amplitude modulated, it can be shown that: 100251

[0026] It follows that the equidistribution of energy on the U spatial layers with Pi = PT V l can still be verified.

[0027] On the other hand, for an e-Type II codebook, whose coefficients are modulated in amplitude, we generally have:

[0028] |W |2 JL

[0029] It follows that an equal distribution of energy over the spatial layers, i.e. Pi ~ ?lpc vh respecting the local energy constraints (or LPC for "Local Power Constraints" in English), leads to: 100301 v,= 1,...WT

[0031] or

[0032] „ < fT LPC

[0033] In other words, to take into account the local energy constraints per antenna port present at the base station level, a backoff must be applied with respect to the maximum resource element energy Pt that can be reached under global constraint only.

[0034] If this backoff is not taken into account by the UE, the base station must modify the energy emitted per sub-band and possibly correct the CSI information reported by the UE by choosing a pre-coder and / or an MCS scheme different from those indicated by the UE. This correction is performed based on the ACK / NACK acknowledgments of the transmission protocol (outer loop link adaptation). However, the base station's knowledge of the downlink transmission channel and the interference it encounters is less precise than that of the UE. Such operation is therefore not optimal and can lead to significant performance degradation.

[0035] Figure 3 illustrates the impact of local energy constraints on communication performance in a single-user MIMO context using an e-Type II precoder selected by means of a frequency-domain selection strategy as described in document DI. This performance is given in terms of spectral energy (expressed in bits per unit area). Channel utilization (bpcu, or "bit per channel utilization") as a function of the signal-to-noise ratio (SNR, or "signal-to-noise ratio") (expressed in dB). The results in [Fig. 3] were generated using the simulation parameters described in detail in Table 3 of document D1, for a CDL-C propagation channel model as defined by the 3GPP standard.

[0036] In this figure:

[0037] - the curve entitled "Bound GPC" assumes that the base station has no local power constraint. This is possible if, for example, each amplifier of the TXRUs is capable of delivering the total power Pt (and is not limited to PT / NTXRU). This corresponds to an oversizing of the amplifiers per TXRU which is not viable from a cost / performance trade-off point of view in the case of a large number of antennas. This curve is therefore an upper bound of the performance achievable in terms of spectral efficiency for massive MIMO (in the results presented here NT=32 antenna ports);

[0038] - the curve entitled "GPC+LPC" corresponds to an assumption made at the level of the EU when selecting the precoder of an energy per resource element transmitted per antenna port equal to Plpc assuming a specific base station implementation choice corresponding to amplifiers per TXRU not exceeding the PT / NTXRIJ power; and

[0039] - the curve entitled "GPC @UE + backoff @BS" corresponds to information CSI of channel state calculated by the UE based on the assumption of a cumulative energy per resource element on the antenna ports equal to Pp (global constraint), and a backoff applied by the base station to return to an energy Plpc per antenna port always assuming the same specific base station implementation choice.

[0040] It is clear from these curves that the backoff required to account for the practical energy constraints present at the base station (overall energy constraint and local energy constraints per antenna port) significantly impacts performance in regions corresponding to a low or medium signal-to-noise ratio (less than 30 dB). The performance degradation is even more pronounced when the base station applies the backoff. Description of the invention

[0041] The invention makes it possible to remedy these drawbacks in particular by providing a method for receiving, by a user device, at least one control message transmitted by a multi-antenna access point of a network, in which said at least one control message comprises, for at least one antenna port among Nt>2 access point antenna ports, a first representative piece of information of an energy per resource element admissible by this antenna port to transmit data signals to the user equipment.

[0042] Correspondingly, the invention also relates to user equipment comprising a receiving module configured to receive at least one control message emitted by a multi-antenna access point of a network, said at least one control message comprising, for at least one antenna port among NT>2 antenna ports of the access point, a first information representative of an energy per resource element admissible by that antenna port to transmit data signals to the user equipment.

[0043] According to the invention, the access point informs the user equipment, by means of a control message, of the local energy constraints per resource element that apply to it. These constraints are advantageously indicated to the user equipment by antenna port, as these are the only elements visible to the user equipment (unlike the TXRUs and the radiating elements of the antennas), by means of the reference signals that it receives and uses to estimate the channel state information and determine the best precoder and MCS scheme to apply, taking into account this channel state information.They therefore take into account the virtualization existing between antenna ports and TXRUs, and between TXRUs and radiating elements, known only to the base station, and the configuration in terms of antenna ports associated with the user equipment in question, while reflecting the limitations of the TXRUs due to power amplifiers.

[0044] The maximum permissible energy per resource element for an antenna port reflects the access point's capacity in terms of the energy that can be emitted at each of its antenna ports. This capacity reflects not only the maximum energy that must not be exceeded for each of its antenna ports during communications with the user equipment, but also, where applicable, the flexibility the access point has with respect to the energy transmitted by each of its antenna ports, taking into account the actual operation of its TXRUs (and in particular their maximum power). This can be particularly advantageous when the TXRUs are oversized and support a maximum power exceeding the maximum nominal transmission power of the access point's antenna array.The user equipment can indeed exploit this oversizing to approach the performance that would be obtained if the access point were subjected only to a global energy constraint per resource element cumulative across all its antenna ports (see the "Bound GPC" curve in [Fig.3]).

[0045] Furthermore, even if each antenna port of the access point is associated with the same number of TXRUs, the groups of TXRUs associated with the different antenna ports differ, and can admit different energies, resulting in potentially different energies per resource element per antenna port.

[0046] In the prior art, this information is known only to the access point, since it depends on the implementation choices of the access point provider. In contrast, the invention proposes to expose this capability to the user equipment, so that it can exploit it and, in particular, optimally select a precoder and an MCS scheme perfectly suited to the transmission channel. It should be noted that acquiring the channel state information (CSI) during transmission is a crucial step in MIMO systems for characterizing the channel properties and thus determining appropriate transmission parameters that optimize the quality of received communication.

[0047] Thus, thanks to the visibility it has, the user equipment can not only take into account, when making this choice, a local constraint at the level of each antenna port of the access point, but it can also exploit an additional degree of freedom which consists of not necessarily transmitting the same power on all antenna ports, and of exploiting, where appropriate, the margins it has with respect to the maximum nominal transmission power of the antenna network at the level of each TXRU. Due to the operation of the TXRUs and more particularly their power amplifiers, the user equipment can, thanks to knowledge of the maximum permissible energy by each antenna port of the access point, tolerate variations between the local energy constraints at the level of the antenna ports of the access point, while balancing them to ensure the maximum overall energy constraint per resource element.In other words, the invention makes it possible to consider energies per resource element emitted at the level of the antenna ports of the access point distinct from one antenna port to another, taking into account a possible oversizing of the TXRUs, while respecting the overall energy constraint (i.e. cumulative on the NT antenna ports) per resource element emitted by the access point.

[0048] In a particular embodiment, the reception method further comprises:

[0049] - a step of estimating transmission parameters for said signals data taking into account said first information included in the control message for said at least one antenna port of the access point and a PT energy per cumulative resource element on the NT antenna ports of the access point fixed to transmit said data signals; and

[0050] - a step of sending the estimated transmission parameters to the access point.

[0051] This embodiment allows the access point to receive a more appropriate estimate of the channel state relative to the actual transmission conditions, requiring little or no correction before being used by the access point. In effect, the local constraints at the access point's antenna ports are already taken into account by the user equipment when estimating transmission parameters: the access point can therefore rely on this estimate without having to apply a backoff to ensure that its local and global constraints (given by the PT energy) in terms of energy are met. Network performance is thus improved, and the complexity of implementing the baseband processing performed by the access point is reduced.

[0052] In a particular embodiment, the cumulative PT energy on the NT antenna ports is obtained by the user equipment from at least one second piece of information included in said at least one control message.

[0053] Typically, in the example of a 5G network as described above, the cumulative PT energy on the NT antenna ports can be obtained by the user equipment from information elements transmitted where appropriate by the base station and in particular the ss-PBCH-BlockPower parameters relating to the power of the SSS synchronization signals (for "Secondary Synchronization Signal" in English), powerControlOffsetSS defining the power offset between the NZP CSLRS resource elements and the SSS resource elements, and powerControlOffset defining the offset between the data signal resource elements and the CSLRS signal resource elements.

[0054] Alternatively, consideration may be given to including in the control message an element of information valued directly with the PT energy.

[0055] In a particular embodiment, the receiving process further includes a step of sending information representative of energies per spatial layer considered by the user equipment during the estimation step and corresponding to said estimated transmission parameters.

[0056] This embodiment allows the access point to know the assumption about the energies per spatial layer made by the user equipment during the optimization of the pre-encoder and the MCS scheme. It thus allows the user equipment to consider selection strategies that allow for different energies per spatial layer.

[0057] Information representing energies per spatial layer can take different forms: the energies themselves, a variation parameter (or "offset" in English) relative to a reference energy allowing these energies to be found, etc.

[0058] In view of the foregoing, the invention therefore relies not only on the user equipment but also on the access point which informs the user equipment of the local and global energy constraints which it must respect on its antenna ports.

[0059] According to another aspect, the invention therefore also relates to a method of sending at least one control message to a user equipment by a multi-antenna access point of a network, in which said at least one control message comprises, for at least one antenna port among NT>2 antenna ports of the access point, a first information representative of an energy per resource element admissible by that antenna port to transmit data signals to the user equipment.

[0060] Correspondingly, the invention also relates to a multi-antenna access point of a network, said access point comprising a sending module, configured to send to a user equipment at least one control message comprising, for at least one antenna port among NT>2 of antenna ports of the access point, a first information representative of an energy per resource element admissible by this antenna port to transmit data signals to the user equipment.

[0061] The sending method and the access point have the same advantages as the receiving method and the user equipment according to the invention.

[0062] In a particular embodiment of the invention, said at least one control message is a message conforming to the RRC, Radio Resource Control protocol.

[0063] This embodiment has a preferred but not limiting application in the context of a 5G or 6G network. However, the invention is not limited to such an application and can be used for other networks, for example for a WLAN network.

[0064] It is conceivable that the initial information relating to the various antenna ports of the access point could be conveyed in a single control message. This allows the user equipment to benefit from this initial information more quickly. Alternatively, however, separate control messages could be used to inform the user equipment.

[0065] Furthermore, in a particular embodiment, said at least one control message includes said first information per antenna port, that is to say said first information for each of the NT antenna ports of the access point: the user equipment thus receives as many first information (NT) as there are antenna ports used in the configuration chosen for communications between the access point and the user equipment.

[0066] In another embodiment, it may be envisaged to send said at least one control message a said first piece of information only for antenna ports supporting an energy per resource element greater than a given reference energy, for example greater than the ratio PT / NT, where PT denotes an energy by cumulative resource element on the NT antenna ports of the access point fixed to transmit said data signals.

[0067] In yet another embodiment, said at least one control message includes said first information valid for the NT antenna ports of the access point.

[0068] These embodiments make it possible to limit the resources needed to inform the user equipment of the access point constraints and thus preserve bandwidth in particular.

[0069] Each first piece of information sent for at least one antenna port can take different forms.

[0070] In a particular embodiment, this first information representing the maximum permissible energy per resource element by an antenna port is properly speaking said maximum permissible energy per resource element by this antenna port.

[0071] In another embodiment, this first piece of information is an admissible surplus by the antenna port with respect to the PT / NT ratio.

[0072] Of course, other forms can be considered as alternatives.

[0073] According to another aspect, the invention also relates to a digital signal transmitted between a multi-antenna access point of a network and a user equipment, said digital signal carrying at least one control message comprising, for at least one antenna port among NT>2 antenna ports of the access point, a first information representative of an energy per resource element admissible by that antenna port to transmit data signals to the user equipment.

[0074] In a particular embodiment, the receiving and sending processes are implemented by a computer.

[0075] The invention also relates to a computer program on a recording medium, this program being capable of being implemented in a computer or more generally in user equipment according to the invention and comprising instructions adapted to the implementation of a receiving process as described above.

[0076] The invention also relates to a computer program on a recording medium, this program being capable of being implemented in a computer or more generally in an access point according to the invention and comprising instructions adapted to the implementation of a sending method as described above.

[0077] Each of these programs can use any programming language, and be in the form of source code, object code, or intermediate code. source and object code, such as in a partially compiled form, or in any other desirable form.

[0078] The invention also relates to an information medium or a recording medium readable by a computer, and comprising instructions for a computer program as mentioned above.

[0079] The information or recording medium can be any entity or device capable of storing programs. For example, the medium may include 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 hard disk drive, or a flash memory.

[0080] On the other hand, the information or recording medium can be a transmissible medium such as an electrical or optical signal, which can be transmitted via an electrical or optical cable, by radio link, by wireless optical link or by other means.

[0081] The program according to the invention can in particular be downloaded onto an Internet-type network.

[0082] Alternatively, the information or recording medium may be an integrated circuit in which a program is incorporated, the circuit being adapted to execute or to be used in the execution of the receiving and sending processes according to the invention.

[0083] According to another aspect, the invention also relates to a communication system comprising at least one access point of a network and at least one user equipment conforming to the invention.

[0084] It can also be envisaged, in other embodiments, that the receiving and sending processes, the digital signal, the user equipment, the access point and the communication system according to the invention have in combination all or part of the aforementioned characteristics. Brief description of the drawings

[0085] Other features and advantages of the present invention will become apparent from the description below, with reference to the accompanying drawings, which illustrate an example of an embodiment without being limiting in any way. In the figures:

[0086] [Fig-1] the [Fig.1], already described, illustrates the abstract notion of antenna port;

[0087] [Fig.2] Fig.2, already described, represents the baseband processing implemented operated by a base station of a 5G NR network for downlink communications;

[0088] [Fig.3] The [Fig.3], already described, illustrates performance results obtained for an e-Type II pre-coder according to the energy constraints taken into account by the user equipment;

[0089] [Fig.4] [Fig.4] represents a communication system according to the invention, in a particular embodiment;

[0090] [Fig.5] [Fig.5] schematically represents the hardware architecture of a computer, user equipment or access point according to the invention in a particular embodiment;

[0091] [Fig.6] [Fig.6] represents the main steps of a sending method according to the invention as implemented by an access point according to the invention in a particular embodiment;

[0092] [Fig.7] [Fig.7] represents the main steps of a reception process according to the invention as implemented by a user equipment according to the invention in a particular embodiment;

[0093] [Fig.8] [Fig.8] illustrates the gain provided by the invention. Description of the invention

[0094] Fig. 4 represents, in its environment, a MIMO communication system 1, according to the invention, in a particular embodiment.

[0095] The communication system 1 comprises: - at least one multi-antenna access point 2 of an NW-5G telecommunications network, conforming to the invention; and - at least one user equipment (or UE) 3, attached to the access point AP, conforming to the invention.

[0096] In the example shown in [Fig. 4], the NW-5G network is a 5G NR network, and access point 2 is a gNB base station of this 5G NR network. Of course, the invention applies in other contexts, typically to networks other than a 5G NR network, such as a 6G access network, a Wi-Fi network, etc., and incidentally, to access points other than a gNB base station corresponding to the access points allowing access to such networks.

[0097] Furthermore, for the sake of simplicity, Figure 4 shows a single gNB 2 base station of the NW-5G network and a single user device 3 connected to this base station. However, the invention also applies in a context where all or part of the base stations of the NW-5G network conform to the invention, as well as all or part of the user devices connected to these base stations. There is no limitation on the nature of the user device 3; it could be a smartphone, a tablet, a laptop, etc.

[0098] The invention applies in a MIMO environment, in downlink mode (for communications from base station 2 to user equipment 3). Thus, base station 2 is equipped with multiple transmitting antennas (by (e.g., NTX antennas), said antennas being associated with one or more RF chains (also called TXRUs hereafter) comprising power amplifiers. User equipment 3, on the other hand, is equipped with multiple receiving antennas (e.g., NRX antennas, Nj denoting a number less than NTX). Each antenna of base station 2 and user equipment 3 may comprise one or more radiating elements.

[0099] By way of illustration, the 4G (LTE) standard requires a number of receiving antennas greater than or equal to 2 for user devices such as smartphones, while the 5G standard allows this number to be increased to at least 4 receiving antennas for certain bands (for example, for the n78 band (3.5GHz)). For base stations, the number of TXRUs typically reaches 64 at present for a number of antenna elements equal to 192 in massive MIMO.

[0100] In the embodiment described herein, the base station 2 is also equipped with multiple receiving antennas, and the user equipment 3 with multiple transmitting antennas. However, other configurations are possible, the invention applying, as mentioned above, to the downlink.

[0101] The radio propagation channel between the multiple transmitting (respectively receiving) antennas of base station 2 and the multiple receiving (respectively transmitting) antennas of user equipment 3 is denoted CH-DL (respectively CH-UL). In the embodiment described here, no assumption is made about the reciprocity of the radio propagation channel; in other words, the CH-DL and CH-UL channels are considered to be different.

[0102] No assumption is made about the number of transmit and receive antennas available to the base station 2 and the user equipment 3. The invention is particularly applicable in a massive MIMO context; however, it is not limited to this context, and can be considered regardless of the number of antennas used by the base station 2 and the user equipment 3.

[0103] As mentioned previously and illustrated in [Fig. 1], the 3GPP standard defined the abstract notion of an AP antenna port of a base station, according to which the radio channel on which a symbol from an antenna port is transmitted can be deduced from the radio channel on which another symbol from the same antenna port is transmitted. Incidentally, the propagation channels corresponding to two distinct antenna ports are considered different. An AP antenna port is therefore a logical entity that does not necessarily coincide with a specific physical antenna of base station 2 or with a specific AE radiating element of a physical antenna of base station 2, but reflects what is visible from the point of view of a user device communicating with base station 2, such as user device 3. Through dual virtualization, an AP antenna port of base station 2 can thus correspond to one or more TXRUs of base station 2 which may themselves correspond to one or more AE radiating elements of a physical antenna of base station 2.

[0104] In [Fig. 4], for the sake of simplicity, only NT(>2) antenna ports AP of base station 2 have been represented, the double virtualization explained above not appearing explicitly in [Fig. 4]. As can be seen from the above, the notion of antenna port is a very general abstract notion which covers both cases where there is a "1-1" correspondence between an antenna port and a physical antenna or radiating element and cases where there is a "1-N" correspondence between an antenna port and a plurality N of physical antennas or radiating elements.

[0105] Furthermore, as mentioned previously, the number NT of antenna ports configured on base station 2 for a given number of TXRUs can fluctuate over time, typically depending on the user equipment (and in particular its capabilities) served by base station 2. For example, for communication with user equipment 3 supporting at most 16 antenna ports, base station 2 may use a transmission configuration in which at most 16 of its antenna ports are configured (i.e., used during this communication). This configuration determines the number of CSI-RS reference signals sent to user equipment 3 for channel state and interference estimation (in the previous example, these CSI-RS signals are configured with 16 antenna ports), the precoding used (e.g., codebook), etc. The document TS 38.214 vl7.7.0 (see in particular table 5.2.2.2.1-2) describes different configurations that can be considered for a 5G network. Furthermore, for energy consumption reasons, some TXRUs may be deactivated, so that the distribution of antenna ports can only be done on the active TXRUs.

[0106] In the embodiment described herein, the base station 2 and the user equipment 3 have the hardware architecture of a computer 4, as shown in [Fig. 5]. This hardware architecture includes, in particular, a processor (PROC), random access memory (MEM), read-only memory (ROM), non-volatile memory (NVM), and communication means via, in particular, the NW-5G network, relying on the multiple transmit and receive antennas of the base station 2 and the user equipment 3.

[0107] The COM communication means implement, in particular for base station 2, baseband processing similar or identical to that described above with reference to [Fig. 2] and detailed in particular in documents 3GPP TS 38.211 vl7.7.0 and TS 38.214 vl7.7.0. This baseband processing includes, in particular, as described above, the application of a pre-encoder A linear PRE_COD characterized by a pre-coding matrix W of dimensions NT x ü, where ü denotes the number of spatial layers considered. When spatial multiplexing is considered, the pre-coding matrix W is determined based on codebooks configured at the base station 2 and user equipment 3, namely, in the embodiment described here, the Type I and e-Type II codebooks described in section 5.2.2.2 of document TS 38.214 vl7.7.0. It should be noted that base station 2 is free to choose a pre-coder different from the one reported by user equipment 3. The report from user equipment 3 is, in this sense, information about the channel state that can be used in very diverse communication contexts (single-user MIMO, multi-user MIMO).

[0108] Of course, the invention also applies in other contexts, to other precodings, other codebooks, etc.

[0109] The non-volatile NVM memory constitutes a recording medium according to the invention, readable by the PROC processor and on which a program according to the invention is recorded.

[0110] This program, denoted PROG2 when the hardware architecture of computer 4 is that of an access point according to the invention, such as base station 2, is stored in the non-volatile NVM memory and comprises instructions defining the main steps of a sending method according to the invention. More specifically, it defines the functional modules of base station 2 (shown in [Fig. 4]), which rely on and / or control all or part of the PROC, MEM, ROM, NVM, and COM elements of computer 4 mentioned above. These functional modules include, in particular, in the embodiment described herein: - a 2A sending module, configured to send to a user device attached to base station 2, and more specifically here to user device 3, at least one control message including, for at least one antenna port among NT antenna ports of base station 2 used to communicate with user device 3, initial information representing the maximum energy per resource element permissible by that antenna port for transmitting data signals to user device 3; and - a 2B receiving module, configured to receive from user equipment 3, transmission parameters representing the CH-DL channel status CSI information between base station 2 and user equipment 3, via user equipment 3. In the example considered here of a 5G-NR type NW-5G network, these transmission parameters include, in particular, a CQI channel quality indicator (typically a modulation and coding scheme index), an indicator of rank RI and a PMI precoding matrix indicator. The receiving module 2B can also be configured to receive other information from user equipment 3, as described in more detail later.

[0111] The functions of modules 2A and 2B are described further later with reference to the steps of the sending process according to the invention.

[0112] When the hardware architecture of the computer 4 is that of a user device 3 according to the invention, the program stored in the non-volatile memory NVM is a PROG3 program comprising instructions defining the main steps of a reception process according to the invention. More specifically, it defines the functional modules of the user device 3 (shown in [Fig. 4]), which rely on and / or control all or part of the PROC, MEM, ROM, NVM, and COM elements of the computer 4 mentioned above. These functional modules include, in particular, in the embodiment described herein: - a 3A receiving module, configured to receive said at least one control message emitted by the 2A sending module of base station 2 to which user equipment 3 is attached, said at least one control message comprising, for at least one antenna port among the NT antenna ports of base station 2 associated with user equipment 3, said first information representing a maximum permissible energy per resource element by that antenna port to transmit data signals to user equipment 3; - a 3B estimation module, configured to estimate the CH-DL channel status CSI information between base station 2 and user equipment 3, this CSI information including, as mentioned previously, the channel quality indicator CQI, the rank indicator RI, and the precoding matrix indicator PMI; and - a 3C sending module, configured to send to base station 2 the transmission parameters representing the CSI channel state information estimated by the 3B estimation module. The CSI channel state information can also be supplemented by other information as described in more detail later.

[0113] The functions of modules 3A to 3C are described further later with reference to the steps of the acceptance process according to the invention.

[0114] We will now describe with reference to Figures 6 and 7 the main steps of the sending ([Fig.6]) and receiving ([Fig.7]) processes as implemented respectively by the base station 2 and by the user equipment 3, in a particular embodiment of the invention.

[0115] As previously stated, in accordance with the 5G standard, the base station 2 configures NZP CSI-RS reference signals to be sent on NT selected antenna ports to communicate with user equipment 3, so that the latter can estimate channel status and interference (step E10, [Fig. 6]). The configuration of the NZP CSI-RS signals and their mapping to resource elements are described in particular in section 7.4.1.5 of 3GPP TS 38.211 v17.7.0 (2024-03) and in section 5.2.2.3 of TS 38.214 v17.7.0. This configuration and mapping are communicated by base station 2 to user equipment 3 in a control message M conforming to the RRC protocol (or simply hereafter RRC message or M message) (step E20), specifically in the information elements CSL-ResourceConfig, NZP-CSI-RS-Resource, and NZP-CSI-RS-ResourceSet, defined in TS document 38.331, entitled "Technical Specification Group Radio Access Network; NR; Radio Resource Control (RRC) protocol specification (Release 17)" vl7.8.0 (2024-03) (see pages 580-581 and 700-703).

[0116] For the sake of reference, the NZP-CSI-RS-Resource information element as currently defined by the 3GPP standard in document TS 38.331 is reproduced in Table 1 below.

[0117] [Tables] - ASN1START - TAG-NZP-CSLRS-RESOURCE-START NZP-CSI-RS-Resource ::= SEQUENCE { nzp-CSLRS-Resourceld NZP-CSLRS-Resourceld, resourceMapping CSI-RS-ResourceMapping, powerControlOffset INTEGER (-8..15), powerControlOffsetSS ENUMERATED{db-3, dbO, db3, db6] OPTIONAL, — Need R scramblinglD Scramblingld, periodicityAndOffset CSI-ResourcePeriodicityAndOffset OPTIONAL, — Co nd PeriodicOrSemiPersistent qcl-InfoPeriodicCSLRS TCLStateld OPTIONAL, — Cond Periodic } Information item NZP-CSI-RS-Resource (TS 38.311 vl7.8.0)

[0118] In this information element, the powerControlOffset field designates the offset in dB between the energy of a resource element of the PDSCH channel and the energy of a resource element of an NZP CSI-RS reference signal. The powerControlOffsetSS field designates the offset in dB between the energy of a resource element of an NZP CSI-RS reference signal and the energy of a resource element of an SSS (Secondary Synchronization Signal). User equipment 3 also knows the energy per resource element of an SSS synchronization signal from the information element ss-PBCH-BlockPower, provided by the upper layers (notably RRC) and transmitted in the information block SIB1 (for "System Information Block Type I") broadcast by base station 2 on the NW-5G network cell in which user equipment 3 is located, in a way known per se and not described in detail here.

[0119] It should be noted that the person skilled in the art uses the term "power" in English, i.e., "puissance" in French, in the aforementioned information elements. However, the quantities designated are, in the case of an OFDM-type transmission system (and incidentally for a 5G NR network transmission system), equivalent to energy per resource element (or EPRE for "Energy Per Resource Element" in English).

[0120] In accordance with the invention, in addition to this information (“second information” within the meaning of the invention), the base station 2, via its transmitting module 2A, sends to the user equipment 3, for at least one of its NT antenna ports APt, t=l,...,NT configured (i.e. activated) for the user equipment 3, information (first information within the meaning of the invention) INFOt representing the maximum permissible energy per resource element for that antenna port to transmit data signals to the user equipment 3. In the embodiment described here, this first information INFOt is transmitted for each of its NT antenna ports configured for the user equipment 3; hereafter, maxEPREt denotes the maximum permissible energy per resource element for the antenna port APt, t=l,...,NT, represented by the information INFOt.

[0121] The energies maxEPREt, t=l,...,NT, (and incidentally the information INFOt, t=l, .. ,,Nt) reflect the effective capacity of base station 2 in terms of energies that can be emitted at its antenna ports, taking into account the operation of its TXRUs; in other words, they reflect the effective energy constraints respected by base station 2 for each of its antenna ports, and not only globally across all of its antenna ports. This is known in Each TXRU has an optimal operating range over which its integrated power amplifier exhibits linear behavior. It is common practice to apply a backoff (power reduction) at base station 2 relative to the maximum power (or equivalently, the energy per resource element) of this range to ensure this linear behavior. This maximum energy does not necessarily correspond to the nominal energy set per resource element for the antenna array to transmit data signals and applied to each TXRU; this nominal energy per resource element and per TXRU is denoted PT / NTXRU, where PT is the nominal energy of the antenna array set per resource element to transmit data signals (PT is, for example, the maximum energy per resource element that can be transmitted) and NTXRU is the number of TXRUs.The power amplifier can be oversized relative to PT / NTXRU, allowing fluctuations around PT / NTXRU, and in particular an energy surplus relative to this average energy.

[0122] Each power amplifier thus has its own effective implementation characteristics, known only to base station 2, which can result in a maximum energy and / or backoff that may differ from one amplifier to another, and therefore, incidentally, from one TXRU to another. Thus, even if each antenna port APt is associated with the same number of TXRUs of base station 2, the groups of TXRUs associated with the different antenna ports differ, and may have different maximum powers, and incidentally, different maximum energies per resource element, resulting in potentially different energies per resource element per antenna port, and potentially different from the maximum energy of the antenna array reported to each antenna port, PT / NT.

[0123] The first INFOt information representing the maxEPREt energies, t=1, ...,Nt, can be obtained by base station 2 from knowledge of the maximum permissible energies of the TXRUs involved in the downlink and the relationship between these TXRUs and each antenna port APt, t=1, ...,NT. As mentioned previously, each antenna port is associated via a linear relationship with a group of TXRUs of base station 2, each group comprising the same number of TXRUs but distinct TXRUs. The maximum permissible maxEPREt energy per resource element for antenna port APt is therefore equal to the sum of the maximum permissible energies of each TXRU in the group of TXRUs of base station 2 associated with that antenna port. For illustrative purposes, consider an antenna array comprising 64 TXRUs, in which each TXRU can transmit an energy per resource element of x.PT / 64, where x denotes a real multiplicative factor greater than or equal to 1. If an antenna port corresponds to the virtualization of 4 TXRUs, it follows that maxEPREt=x.PT / 64 or x.PT / 16.

[0124] In the embodiment described herein, the first INFOt information representing the energies maxEPREt, t=l,...,NT is sent by the transmitting module 2A of base station 2 in the control message M, and more particularly in the form of a DeltaPowers sequence of length NT with parameters DeltaPowerPerAP transmitted in the NZP-CSL RS-Resource information element illustrated in Table 1. The maximum number of ports is given by the parameter maxNrofPorts, for example taken as 32 here, in the context of a 5G NR network. The control message M is carried by a digital signal according to the invention.

[0125] Table 2 below represents a possible example of the modification of the information element NZP-CSI-RS-Resource to integrate the DeltaPowers sequence of the DeltaPowerPerAP parameters (appearing in bold characters in Table 2).

[0126] [Tables2] - ASN1START - TAG-NZP-CSLRS-RESOURCE-START NZP-CSI-RS-Resource ::= SEQUENCE { nzp-CSLRS-Resourceld NZP-CSLRS-Resourceld, resourceMapping CSLRS-ResourceMapping, powerControlOffset INTEGER (-8..15), DeltaPowers SEQUENCE(SIZE(l,...,maxNrolPorts)) OF DeltaPowerPe rAP DeltaPowerPerAP INTEGER (0..Y), powerControlOffsetSS ENUMERATED{db-3, dbO, db3, db6] OPTIONAL, — Need R scramblinglD Scramblingld, periodicityAndOffset CSLResourcePeriodicityAndOffset OPTIONAL, — Co nd PeriodicOrSemiPersistent qcl-InfoPeriodicCSLRS TCLStateld OPTIONAL, — Cond Periodic } Example of a modified NZP-CSI-RS-Resource information element for the implementation of the invention

[0127] The new parameter DeltaPowerPerAP is, according to this example, an integer whose value is expressed in dB and is between 0 and Y dB, where Y is a positive real number. Here, for each antenna port activated by base station 2 to communicate with user equipment 3, it reflects the maximum excess (APt)dB (first piece of information in the sense of the invention) in dB in terms of the energy allowed by the antenna port APt relative to the PT / NT ratio. If we denote APt as the corresponding linear value, we obtain the following for the antenna port APt of base station 2:

[0128] maxEPRet= (PT / NT).APt

[0129] with APt a real number greater than or equal to 1, which may differ from one antenna port to another or be identical for all ports depending on the implementation characteristics of the TXRUs of base station 2. It is noted that similarly to what was described previously for maxEPREt, the surplus APt is obtained by base station 2 from the surpluses admissible by the TXRUs virtualized by the antenna port APt.

[0130] In the example in Table 2, the DeltaPowerPerAP parameter is provided for each antenna port of base station 2 activated for user equipment 3, allowing for distinct DeltaPowerPerAP parameters from one antenna port to another. If this parameter is the same for all antenna ports of base station 2 activated for user equipment 3, a single DeltaPowerPerAP parameter equal, for example, to (AP0)dB could be transmitted instead of the DeltaPowers sequence of parameters.

[0131] Of course, these are only examples of implementations of the invention, which are provided here for illustrative purposes only. Alternative ways of transmitting the initial INFOt information relating to the various activated antenna ports of base station 2 can be considered. For example, the initial information can be transmitted in separate RRC messages, be mandatory, be presented as a percentage of the PT / NT ratio, etc. According to another example, the initial INFOt information provided in the control message M for each antenna port APt, t=l,...,NT may not take the form of excess APt relative to the PT / NT ratio as in the example in Table 2, but correspond directly to the value of the maximum permissible energy EPREt per element of the maximum permissible resource for the antenna port APt in question, etc.According to yet another example, it is possible to consider transmitting in the control message M only the first INFOt information which relates to supporting antenna ports. a surplus compared to the PT / NT ratio. Other configurations can also be considered.

[0132] The control message M is sent by the sending module 2A of base station 2 to user equipment 3 on the PDSCH channel, in a manner known per se and not described in detail here.

[0133] Base station 2 also sends predefined NZP CSLRS reference signals to user equipment 3 via its NT antenna ports, corresponding to the configuration advertised in the control message M (step E30), as described in particular in 3GPP TS 38.211 vl7.7.0. The NZP CSLRS reference signals define the antenna ports to which the W precoder is applied. The NZP CSLRS reference signals allow user equipment 3 to estimate the CSI status information of the downlink channel, and in particular the CQI, RI, and PMI parameters mentioned previously. It should be noted that the antenna ports associated with the NZP CSLRS reference signals may themselves undergo precoding transparent to the user equipment. This precoding (which is distinct from the W precoding) then becomes part of the channel measured by the user equipment.

[0134] With reference to [Fig. 7], user equipment 3 receives, via its receiver module 3A, the control message M sent by base station 2 (step F10). In the embodiment described here, user equipment 3 extracts from the control message M the various parameters transmitted in the information elements contained in message M, and in particular the first INFOt information transmitted for the antenna ports APt, t=l, ..., NT. It stores them, for example, in its non-volatile memory (NVM).

[0135] User equipment 3 also receives the NZP CSLRS reference signals transmitted by base station 2 via each of its APt, t=l,...,NT antenna ports configured for user equipment 3 (step F20). It then performs, via its estimation module 3B, the estimation of the CH-DL downlink channel from the received NZP CSLRS reference signals, in a manner known per se (step F30).

[0136] The NZP CSLRS reference signals are indeed transmitted by base station 2 orthogonally on the NT antenna ports APt, t=l,...,NT, so that the signal received by the receiving module 3A of user equipment 3 can be written, for each antenna port APt, t=l,...,NT, as follows:

[0137] = HxPIRS+n

[0138] where: - H denotes the NT x NR dimension CH-DL downlink channel matrix for the sub-band considered, NR being the number of receiving antenna ports of user equipment 3;

[0139]

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] - designates the NZP CSI-RS signal emitted via the APt antenna port: ^CSI-'RS — where and is the t-th column of the I^T identity matrix and | |2 ] = Pcsirs denoting the energy per resource element of a CSI-RS NZP reference signal; and - n denotes noise and interference. The result is that: yCSI'RS = ^csi-rs Hx™™+n = + n with : St^PcSI-RS = l where Pcsi-rs denotes the energy per resource element of an NZP CSI-RS reference signal. User equipment 3 knows, via the information elements received in the control message M, the energy of a resource element of an SSS synchronization signal (given by the ss-PBCH-BlockPowef field), as well as the offset in dBm between the energy of a resource element of an NZP CSI-RS reference signal and the energy of a resource element of an SSS synchronization signal (given by the powerControlOffsetSS' field). It can deduce the Pcsi-rs energy per resource element of an NZP CSI-RS reference signal and estimate, for each APt antenna port, the downlink propagation channel seen by the NZP CSI-RS signals, i.e., £ _ t . nt ~ y* CSI-RS nt The estimation module 3B also estimates the interference covariance matrix plus noise E[nnH], in a self-known manner, from the CSLIM interference measurement resource elements. Furthermore, if we denote by x the column vector of dimension U (corresponding to ü spatial layers) of the data signals transmitted to user equipment 3 on the PDSCH channel, via the NT antenna ports of base station 2, the signal λ received by user equipment 3 is written: j = HWx + n where W denotes the precoding matrix applied to these data signals (of NT xu dimensions). It should be noted that, in accordance with the 3GPP standard, the precoding matrix W is normalized and satisfies: WHW^Uü It follows that for a given spatial layer ü, we have: Lu 2 1 / =)1¾) ~ ô

[0153] where denotes the coefficient of the precoding matrix W corresponding to the APt antenna port and the spatial layer.

[0154] The energy P per resource element of a data signal, accumulated over the NT The antenna ports of the base station are then given by:

[0155] P~e[xhWHWx]

[0156] This results in the following model (Modl / W), conditioned on the pre-coder W:

[0157] y = ^H^x + n

[0158] with£[ = uetEfxj^

[0159] Assuming that P=PT, if the estimation module 3B also has the ratio PpDscH between the energy PT of a resource element of a data signal transmitted on the PDSCH channel and the energy of a resource element of a reference signal NZP CSLRS, it is able to determine, from the knowledge of the energy Pcsi-rs and the channel estimation, the energy PT per resource element of a signal

[0160]

[0161]

[0162]

[0163] of data transmitted on the PDSCH channel to user equipment 3 and deduce the propagation channel ^p & in downlink seen by the data signals sent by base station 2 on the PDSCH channel to user equipment 3 for each antenna port APt, t=l,...,NT. We have indeed: fi = "PDSCH Pcmrs The value of the ratio [Sposcuest given where applicable in dB by the (optional) powerControlOffset field. Using the estimations performed, the estimation module 3B is able to estimate the state information of the CSI channel, and more specifically to select transmission parameters including the PMI precoding matrix and the corresponding CQI and RI parameters to send back to base station 2 (step F40). In the embodiment described here, this selection is made from the codebooks defined in paragraph 5.2.2.2 of the 3GPP TS 38.214 vl7.7.0 (2023-09) document. It should be noted, however, that the selection of the MCS modulation and coding scheme for link adaptation, as well as the selection of the precoding matrix and the RI parameter, are not strictly described in the 3GPP standard; Their implementation is left to the discretion of the manufacturer of the user equipment 3. As examples, to proceed to the determination of the CQI, RI and PMI transmission parameters, the estimation module 3B can rely on one of the techniques described in the document D1 cited above (for example a frequency domain selection technique or "FD-strategy"), adapting the teaching of this document to take into account the global and local constraints existing in terms of energy per resource element, described in more detail below.

[0164] It should be noted that the DI document is based on the assumption of a global constraint only on the energy Pt per cumulative resource element on the NT antenna ports of base station 2, and that according to this global constraint, the energy Pt per cumulative resource element on the NT antenna ports is normalized to 1. A person skilled in the art would be able to adapt the selection strategies described in this document to take into account other constraints in terms of energy, and in particular the global and local constraints stated below.

[0165] The global energy constraint (GPC) is written as follows:

[0166] (GPC)

[0167] where Pi denotes the energy per resource element for the spatial layer indexed by cumulative over the NT antenna ports.

[0168] The local energy constraints (LPCt), t=l,.. .,NT, are written, for each APt antenna port of base station 2, as follows:

[0169] 12p < maxEPRet

[0170] or, equivalently:

[0171] yU iv APt(LPCt) ^=1™ rl~NT

[0172] either formulation may be used depending on what is exposed to user equipment 3 in the INFOt information received in the control message M.

[0173] It is noted that, in certain cases, these constraints may take other equivalent forms.

[0174] For example, in the case where all TXRUs are identical, we can assume that APt = AP0, for all t = l,...,NT. In this case, the local energy constraints (LPCt), t = l,...,NT, can be written as: 101751

[0176] In addition, when estimating the CQI, PMI and RI transmission parameters, the estimation module 3B can impose an energy Pi per cumulative resource element on the Nt antenna ports, identical for each spatial layer l, l = 1, i.e. Pi~ Plpc Vl-V ..., □ (in other words an equal distribution of energy on the ü spatial layers).

[0177] The global and local energy constraints to be verified jointly are then written:

[0178] Plpc^Pt (GPC”)

[0179] etW=l, :

[0180] AP0 (LPCt”)

[0181]

[0182]

[0183]

[0184]

[0185]

[0186]

[0187] The optimal choice for the energy per spatial layer, Plpc, given these constraints, is then: „ . / Pr.AP0 „ \ P t Pf1 min I ox ? Pt i It is this energy Plpc per resource element that the user equipment estimation module 3B considers when selecting the CQI, RI, and PMI transmission parameters. As a result, the energy per resource element of the data signals transmitted by base station 2 using these transmission parameters is, in this case, P = Plpc - Pt- Other hypotheses can be considered; for example, one could explore an additional degree of freedom by allowing distinct Pi energies per resource element for the different spatial layers. To this end, the estimation module 3B can use a selection technique similar to that described in French patent application FR 2306435, which maximizes the transmission rates per antenna port (cumulative across the different spatial layers). In this scenario, the distribution of energies on the different spatial layers corresponding to the CQI, PMI and RI parameters estimated by the estimation module 3B must be communicated to base station 2. Regardless of the assumptions considered, following the estimation of the CQI, PMI and RI transmission parameters by the estimation module 3B, the user equipment 3, via its sending module 3C, sends the transmission parameters thus estimated to the base station 2 (step F50), in a manner known in itself. Base station 2's knowledge of the spatial layer energy allocation criterion applied by user equipment 3 during the estimation of the CQI transmission parameters leads to greater efficiency. Thus, if this criterion differs from an equal distribution of energy across the spatial layers, in the embodiment described here, user equipment 3, via its 3C transmission module, also sends base station 2 information representative of the spatial layer energies considered by user equipment 3's estimation module 3B, corresponding to the CQI, PMI, and RI transmission parameters sent to base station 2 during step F40. Such information can, for example, consist of the energies allocated to the spatial layers themselves, or a Zp] offset value in dB for each spatial layer relative to an energy ^''dB reference (for example with respect to the PT energy, leading to Pj — (with linear value corresponding to j ), etc.

[0188] Upon receiving the CSI channel status information transmitted by user equipment 3, including the CQI, PMI, and RI transmission parameters (step E40), base station 2 is free to apply or not the transmission parameters estimated by user equipment 3 to transmit data signals to user equipment 3 over the PDSCH channel (including, where applicable, the spatial layer energies reported by user equipment 3), in a manner known per se and described in 3GPP documents TS38.211 vl7.7.0, paragraph 7.3.1, and TS38.214 vl7.7.0 (step E50). However, the invention improves the reliability of the transmission parameters estimated by user equipment 3 and the probability that base station 2 will use such transmission parameters as they are in their current state during its communications with user equipment 3.

[0189] Figure 8 illustrates the benefit provided by the invention, through consideration of the effective capacity of the base station in terms of energy that can be transmitted via its antenna ports. Simulation assumptions similar to those of Figure 3, and described in Document DI at Table 3, were considered, with a CDC-C propagation channel model as defined by the 3GPP standard. The simulation results are given in terms of spectral energy (expressed in bcpcu) as a function of the signal-to-noise ratio or SNR (expressed in dB). These results were obtained using the frequency-domain selection strategy described in Document DI, adapted to take into account different types of energy constraints. Furthermore, they were generated by considering an equal distribution of energy across the different spatial layers and TXRUs all having the same operating characteristics.

[0190] The different curves obtained correspond to different APO values. Furthermore, the "Bound GPC", "GPC+LPC" and "GPC @UE + backoff @BS" curves have been reproduced for reference.

[0191] It appears in [Fig. 8] that the flexibility provided by the invention, by allowing user equipment to exploit the oversizing of the TXRUs, makes it possible to approach the "Bound GPC" limit despite the existence of local energy constraints at the base station. A value of AP0 = 2 dB is sufficient to reach this limit, while respecting the overall energy constraint of a maximum energy per cumulative resource element on the antenna ports equal to PT.

[0192] It should be noted that the "Bound GPC" limit is theoretically attainable for a value of AP0=101ogi0(NT), in other words, for a number of ports NT=32 as in [Fig. 8], a value of AP0=15dB. [Fig. 8] shows that, thanks to the invention, this limit is practically reached with an oversizing per antenna port of only 2dB, and a value of AP0=ldB already allows a substantial gain in terms of performance. The invention therefore makes it easy to achieve a good compromise between implementation cost and performance.

Claims

Demands

1. Method of receiving (F10) by a user equipment (3) at least one control message (M) issued by a multi-antenna access point (2) of a network, wherein said at least one control message comprises, for at least one antenna port among NT>2 antenna ports of the access point, a first piece of information (INFOt) representative of the maximum energy per resource element admissible by that antenna port for transmitting data signals to the user equipment.

2. A receiving method according to claim 1 further comprising: - a step (F40) of estimating transmission parameters for said data signals taking into account said first information included in the control message for said at least one antenna port of the access point and a PT energy per cumulative resource element on the Nt antenna ports of the access point fixed to transmit said data signals; and - a step (F50) of sending said estimated transmission parameters to the access point.

3. A receiving method according to claim 2 wherein the cumulative PT energy on the NT antenna ports is obtained by the user equipment from at least one second piece of information included in said at least one control message.

4. A receiving method according to claim 2 or 3 further comprising a sending step (F50) of information representative of energies per spatial layer considered by the user equipment during the estimation step and corresponding to said estimated transmission parameters.

5. Method of sending (E10) at least one control message (M) to a user equipment by a multi-antenna access point of a network, wherein said at least one control message comprises, for at least one antenna port among NT>2 antenna ports of the access point, a first information representative of an energy per resource element admissible by that antenna port to transmit data signals to the user equipment.

6. A method according to any one of claims 1 to 5 wherein said first information (INFOt) is the maximum allowable energy per resource element through the antenna port.

7. A method according to any one of claims 1 to 6 wherein said first information (INFOt) is an allowable surplus by the antenna port with respect to a PT / NT ratio, where PT denotes an energy per resource element accumulated on the NT antenna ports of the access point fixed to transmit said data signals.

8. A method according to any one of claims 1 to 7 wherein said at least one control message comprises said first information for each of the NT antenna ports of the access point.

9. A method according to any one of claims 1 to 7 wherein said at least one control message comprises said first information valid for the NT antenna ports of the access point.

10. A method according to any one of claims 1 to 9 wherein said at least one control message is a message conforming to the RRC, Radio Resource Control protocol.

11. User equipment (3) comprising a receiving module (3A) configured to receive at least one control message issued by a multi-antenna access point of a network, said at least one control message comprising, for at least one antenna port among NT>2 antenna ports of the access point, a first representative piece of information of maximum energy per resource element admissible by that antenna port for transmitting data signals to the user equipment.

12. A multi-antenna access point (2) of a network, said access point comprising a sending module (2A) configured to send to a user equipment at least one control message comprising, for at least one antenna port among NT>2 antenna ports of the access point, a first representative piece of information of maximum energy per resource element admissible by that antenna port for transmitting data signals to the user equipment.

13. Communication system (1) comprising: - at least one access point (2) of a network according to claim 12; and - at least one user equipment (3) according to claim 11. 33

14. Digital signal transmitted between a multi-antenna access point of a network and a user equipment (3), said digital signal carrying at least one control message (M) comprising, for at least one antenna port among NT>2 antenna ports of the access point, information representative of the maximum energy per resource element admissible by that antenna port for transmitting data signals to the user equipment.

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