Beam control feedback messaging using shared antenna weights

Abstract

Various examples of the disclosure pertain to reporting on channel reference signals, e.g., channel state information reference signals. Shared antenna weights (411) for multiple different beam selections may be used.

Description

[0001] D E S C R I P T I O N

[0002] BEAM CONTROL FEEDBACK MESSAGING USING SHARED ANTENNA WEIGHTS TECHNICAL FIELD

[0003] Various examples of the disclosure generally pertain to beam control. Various examples specifically relate to a reporting procedure to provide a feedback message based on monitoring channel state reference signals.

[0004] BACKGROUND

[0005] Channel sounding in 3rd Generation Partnership Project (3GPP) cellular networks involves the use of channel state reference signals - in particular, Channel State Information (CSI) reference signals - transmitted between the base station (BS) and user equipment (UE) to assess the channel conditions. CSI reference signals enable the UE to measure channel characteristics, such as path loss, fading, and interference. This may be helpful as part of beam control when identifying appropriate precoders at a multi-antenna transmit point.

[0006] Multiple Input Multiple Output (MIMO) is a multi-antenna technique that employs multiple antennas at a transmit point (e.g., a BS or a 3GPP Transmit Receive Point, TRP) and / or a receive point (e.g., a UE). MIMO facilitates beamforming and / or the simultaneous transmission and reception of multiple data streams over the same radio channel, enhancing the network's capacity and speed without necessitating additional spectrum.

[0007] Beamforming directs transmitted signals (TX beamforming) along specific directions or paths (beams). This is achieved by adjusting the phase and amplitude of the signal at each antenna element of an antenna array.

[0008] Multiple parallel data streams can be achieved by using multiple transmission layers, where each layer represents an independent data stream. Different transmission layers may be associated with different eigenmodes of the radio channel. Eigenmodes represent the independent paths through which signals can be transmitted with minimal interference, each characterized by a singular value that indicates the strength of the channel in that mode. Using multiple transmit points spatially offset from each other and jointly transmitting data -e.g., multiple TRPs - is another strategy to enhance network performance, allowing signals to be transmitted to the UE from various geographical locations. Spatial diversity is thereby obtained.

[0009] In all such techniques, the appropriate transmit precoder is determined using beam control (also referred to as “beam management” or “channel sounding” or “channel state information acquisition”). Here, channel state reference signals - e.g., CSI reference signals - may be transmitted by a TX point and received by the RX point. For instance, CSI reference signals may be transmitted by a BS and received by a UE. Then, a feedback message is provided based on monitoring the channel state reference signals at the RX point, thereby enabling determining of the appropriate TX precoder at the TX point.

[0010] There are many different beam control procedures known. For example, type-ll precoder construction in 3GPP 5G cellular networks (here referred to as channel state information acquisition) includes the use of beam selection and precoding matrices (i.e., antenna weights for each selected beam) determined at the UE based on the CSI reference signals. Type-ll precoder construction thus selects and linearly combines multiple TX beams, as opposed to Type I precoders, which select only one TX beam. To do so, CSI reference signals are transmitted by a BS of the cellular NW using multiple TX beams (TX beam sweep for CSI reference signals). A feedback message from the UE includes a selection of one or more of the multiple TX beams; as well as antenna weights for that selection of the multiple TX beams, i.e., amplitude and phase relationship for the beam selection.

[0011] This reporting may be executed for each TRP of the cellular network (NW) and / or for each transmission layer. This results in a situation in which the required feedback messages cause significant signaling overhead. In particular, many information bits may be required for signaling the antenna weights, since these are complex numbers (amplitude and phase). SUMMARY

[0012] Hereinafter, techniques for beam control in Ml MO communication systems are disclosed. In particular, advanced techniques of providing feedback messages upon monitoring for channel state reference signals - e.g., 3GPP-specified CSI reference signals - are disclosed.

[0013] This need is met by the features of the independent claims. The features of the independent claims define embodiments.

[0014] A method for use in a wireless communication device is disclosed. The wireless communication device is connected to a communications network. The method includes monitoring for channel state reference signals. The channel state reference signals are transmitted by at least one transmit point of the communications network. The channel state reference signals are transmitted using a plurality of transmit beams. The method also includes providing, to the communication network, at least one feedback message based on said monitoring. The at least one feedback message is indicative of a first beam selection from the plurality transmit beams and further indicative of a second beam selection from the plurality transmit beams. The at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection. The antenna weights comprise one or more shared antenna weights, each one of the one or more shared antenna weights being jointly assigned to a respective transmit beam of the first beam selection and a respective transmit beam of the second beam selection. A method of use in device of a communications network is disclosed. A wireless communication device is connected to the communications network. The method includes triggering at least one transmit point of the cellular network to transmit channel state reference signals using a plurality of transmit beams. The method laso includes obtaining, from the wireless communication device, at least one feedback message. The at least one feedback message is indicative of a first beam selection from the multiple transmit beams and further indicative of a second beam selection from the multiple transmit beams. The at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection. The antenna weights comprise one or more shared antenna weights, wherein each of the one or more shared antenna weights is jointly assigned to a transmit beam of the first selection and a transmit beam of the second selection.

[0015] A method for use in a wireless communication device is disclosed. The wireless communication device is connected to a communications network. The method includes monitoring for channel state reference signals transmitted by multiple transmit points of the communications network using a plurality of transmit beams. The method also includes providing, to the communication network, at least one feedback message based on said monitoring. The at least one feedback message is indicative of a request for muting of at least one of the multiple transmit points.

[0016] A wireless communication device connectable to a communications network is disclosed. The wireless communication device includes circuitry configured to monitor for channel state reference signals transmitted by at least one transmit point of the communications network using a plurality of transmit beams. The circuitry is further configured to provide, to the communication network, at least one feedback message based on said monitoring. The at least one feedback message is indicative of a first beam selection from the plurality transmit beams and further indicative of a second beam selection from the plurality transmit beams. The at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection. The antenna weights comprise one or more shared antenna weights, each one of the one or more shared antenna weights being jointly assigned to a respective transmit beam of the first beam selection and a respective transmit beam of the second beam selection.

[0017] A device of a communications network to which a wireless communication device is connectable is disclosed. The device includes circuitry configured to trigger at least one transmit point of the cellular network to transmit channel state reference signals using a plurality of transmit beams and further configured to obtain, from the wireless communication device, at least one feedback message. The at least one feedback message is indicative of a first beam selection from the multiple transmit beams and further indicative of a second beam selection from the multiple transmit beams,

[0018] wherein the at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection. The antenna weights comprise one or more shared antenna weights, wherein each of the one or more shared antenna weights is jointly assigned to a transmit beam of the first selection and a transmit beam of the second selection.

[0019] A wireless communication device connectable to a communications network is disclosed. The wireless communication device includes circuitry configured to obtain, from the communications network, a control message indicative of a reporting configuration for providing at least one feedback message based on monitoring for channel state reference signals transmitted by at least one transmit point of the communications network using a plurality of transmit beams, the at least one feedback message being indicative of multiple beam selections from the plurality of transmit beams. The reporting configuration is associated with one or more shared antenna weights indicated by the at least one feedback message, each of the one or more shared antenna weights being jointly assigned to multiple beam selections from the plurality of transmit beams.

[0020] A wireless communication device connectable to a communications network is disclosed. The wireless communication device comprising circuitry configured to monitor for channel state reference signals transmitted by a multiple transmit points of the communications network using a plurality of transmit beams, and to provide, to the communication network, at least one feedback message based on said monitoring. The at least one feedback message being indicative of a request for muting of at least one of the multiple transmit points.

[0021] A system includes a wireless communication device as disclosed above and a device of a communications network as disclosed above.

[0022] It is to be understood that the features mentioned above and those yet to be explained below may be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the disclosure.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart of a method for beam control including transmission of multiple CSI reference signals and feedback messaging for one or more data layers according to various examples.

[0024] FIG. 2 schematically illustrates a beam sweep including multiple TX beams for CSI reference signals according to various examples.

[0025] FIG. 3 schematically illustrates two beam sweeps including multiple TX beams for CSI reference signals from two different transmit points according to various examples.

[0026] FIG. 4 generally corresponds to FIG. 3 and illustrates feedback messages indicative of a beam selection and antenna weights for the TX beams of each beam sweep, wherein shared antenna weights are not used.

[0027] FIG. 5 illustrates the feedback messages of FIG. 4 in further detail.

[0028] FIG. 6 generally corresponds to FIG. 3 and illustrates feedback messages indicative of a beam selection and antenna weights for the TX beams of each beam sweep, wherein shared antenna weights are used.

[0029] FIG. 7A is a first option for implementing the feedback messages of FIG. 6 according to various examples.

[0030] FIG. 7B is a second option for implementing the feedback messages of FIG. 6 according to various examples.

[0031] FIG. 8 is a third option for implementing the feedback messages of FIG. 6 according to various examples.

[0032] FIG. 9 illustrates a performance metric for a first scenario as a number of TX beams in a beam sweep according to various examples.

[0033] FIG. 10 illustrates another performance metric for the first scenario of FIG. 9 according to various examples.

[0034] FIG. 11 illustrates another performance metric for the first scenario of FIG. 9 according to various examples.

[0035] FIG. 12 illustrates a performance metric for a second scenario as a number of TX beams according to various examples.

[0036] FIG. 13 illustrates another performance metric for the second scenario of FIG. 12 according to various examples.

[0037] FIG. 14 illustrates another performance metric for the second scenario of FIG. 12 according to various examples. FIG. 15 schematically illustrates a communication system formed by a cellular network and a UE connected to the cellular network.

[0038] FIG. 16 schematically illustrates a base station according to various examples.

[0039] FIG. 17 schematically illustrates a UE according to various examples.

[0040] FIG. 18 is a flowchart of a method for use in a UE according to various examples.

[0041] FIG. 19 is a flowchart for use in a device of a communications network, e.g., in a BS of a cellular network, according to various examples.

[0042] FIG. 20 is a signaling diagram according to various examples.

[0043] FIG. 21 is a signaling diagram according to various examples.

[0044] FIG. 22 is a signaling diagram according to various examples.

[0045] DETAILED DESCRIPTION

[0046] Some examples of the present disclosure generally provide for a plurality of circuits or other electrical devices. All references to the circuits and other electrical devices and the functionality provided by each are not intended to be limited to encompassing only what is illustrated and described herein. While particular labels may be assigned to the various circuits or other electrical devices disclosed, such labels are not intended to limit the scope of operation for the circuits and the other electrical devices. Such circuits and other electrical devices may be combined with each other and / or separated in any manner based on the particular type of electrical implementation that is desired. It is recognized that any circuit or other electrical device disclosed herein may include any number of microcontrollers, a graphics processor unit (GPU), a tensor processing unit (TPU), integrated circuits such as application-specific integrated circuits or field-programmable gate array (FPGA) circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, any one or more of the electrical devices may be configured to execute a program code that is embodied in a non-transitory computer readable medium programmed to perform any number of the functions as disclosed.

[0047] In the following, embodiments of the disclosure will be described in detail with reference to the accompanying drawings. It is to be understood that the following description of embodiments is not to be taken in a limiting sense. The scope of the disclosure is not intended to be limited by the embodiments described hereinafter or by the drawings, which are taken to be illustrative only.

[0048] The drawings are to be regarded as being schematic representations and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by an indirect connection or coupling. A coupling between components may also be established over a wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0049] Hereinafter, techniques for operating a wireless communication system are disclosed. The wireless communication system includes one or more TX points and an RX point. For instance, the one or more TX points may be implemented by a BSs of a cellular network or TRPs connected to BSs. The RX point may be implemented by a UE connected to the cellular network. The techniques disclosed herein are also applicable to Wi-Fi communication between an access point (AP) and a connected station device (STA). An AP serves as the central transmitter and receiver in a wireless local area communications network, handling the distribution of data to and from the STA that connect to the network. The STA represents any device, such as a smartphone, laptop, or tablet, that connects to the AP to access the network and its resources.

[0050] The wireless communication system employs multi-antenna techniques. In particular, one or more TX points include an antenna array for which a TX precoder is to be found. This is based on a beam control procedure. The beam control procedure includes transmitting channel state reference signals, e.g., 3GPP CSI reference signals or IEEE 802.11 Null Data Packets (NDPs). Hereinafter, techniques are disclosed for an implementation of the wireless communication system by a cellular network and a UE connected to the cellular network. The UE is connected to the cellular network through a serving BS. The cellular network may include multiple TRPs per BS.

[0051] For facilitating beam control, a BS transmits multiple CSI reference signals using a TX beam sweep. If the BS has control over multiple TRPs, each TRP is triggered to transmit multiple CSI reference signals using a respective TX beam sweep. The UE monitors, i.e., attempts to receive, the CSI reference signals and provides one or more feedback messages based on said monitoring. According to various examples, a so-called Type-ll precoder construction is used. This means that the UE is requested to select at least one TX beam from the multiple TX beams on which CSI reference signals are transmitted. Furthermore, if multiple TX beams are included in a respective UE beam selection, the UE provides antenna weights, i.e., amplitude and phase relationships amongst those TX beams included in the beam selection. Assume, for now, a single TRP. Type-ll precoder construction works as illustrated in the flowchart of FIG. 1: The TRP transmits a number, N, of CSI reference signals (box 3005) on multiple TX beams. For each transmission / data layer (box 3020), where the number of data layers is referred to as the rank, the UE reports (box 3015) the indices of M beams to be used by the network (beam selection) and M weighting coefficients (antenna weights) to be applied at each beam, i.e., amplitude scaling and phase.

[0052] This is exemplified in the following example. Assume a TRP with 4 antennas, set N = 8, M = 3 and rank=2 (i.e., two data layer). The 4 antennas and N = 8 assumptions imply that the network triggers that TRP 165 (cf. FIG. 2) to transmit N = 8 instances of the CSI-RS, each time with a new transmit configuration, i.e., on 8 beams 201-208. For example, n:th instance may, e.g., use the configuration^, whered

[0053] 1 1

[0054] T J7T

[0055] 1 e 8 e~ e~

[0056] ]2lt > b^ J12n 1 > ^2 by > bs

[0057] e 8 e~ e 8 -1- j3n J187T

[0058] The UE 102 m

[0059]

[0060] ay be unaware & fhe vectors'^, the effective channels zn= hbnwhere h is a row vector capturing the channel between the TRP and a UE having at least two antennas. For layer 1, the UE may now report as a feedback message, e.g., the indices I±= {1,3,5} (this is the beam selection) and coefficients = {0.5,1 - j, 2j} (these are the antenna weights), while for the second layer it may report (e.g.) the indices I2= {1,6,7} and coefficients C2= {2,-1 + j, 1 - 2j}. Based on this, the cellular network may form its transmission s of two data symbols x±and x2towards the UE as

[0061] s = b1x 0.5 + b3x (1 - j) + b5x 2j)x1+ b1x 2 + b6x (-1 + j) + b7x (1 - 2J))X2.

[0062] The sets are chosen / 1, / 2, C1, C2to produce (near-)optimal performance. The particular optimization to do so is out-of-scope of the subject disclosure.

[0063] Note that the coefficients defining the antenna weights require a significant number of information bits, because these are complex numbers (to define amplitude scaling and phase relationship). Such complex numbers may be transmitted as pairs (a, b), a, b e HR of real and imaginary parts, or as pairs p,<p),p > 0, <p e [0,2TT) of magnitudes and phases. Currently, 3GPP uses the second approach.

[0064] Consider now the case of two TRPs 165, 166 (cf. FIG. 3), and base the discussion on the above example. Each TRP 165, 166 may now sound N' = 4 beams, so that a total of N = 2Nr= 8 beams 211-218 are still received at the UE 102. Assume that b - b4(i.e., beams 211-214) are beams transmitted from TRP 165 while b5- b8(i.e., beams 215-218) are transmitted from TRP 166. The index reports I4and I2(beam selection) involve beams from both TRPs. This is shown in FIG. 4.

[0065] FIG. 4 illustrates the situation for N = 4 beams, rank 1, and M = 2. Again, M is the number of applied beams. Assume that the UE 102 should feedback individual index and coefficient reports to both TRPs 165, 166, i.e., it should provide two feedback messages 301, 302 indicative of (I1, C1) and ( / 2, C2) to each TRP. Note that the sub-scripts in I4and I2earlier in the text referred to the layer index. Each beam selection includes TX beams of a single TRP only. E.g., in view of example of FIG. 3, I1may only contain elements from the set {1,2, 3, 4} and I2only elements from {5, 6, 7, 8}.

[0066] To each TRP, the UE should identify which two (since M = 2) out of the 4 TRP beams that should be used, and the corresponding weights. There are ) = 6 ways in which 2 elements (i.e., beam indices) can be chosen from 4; these are: (1,2), (1,3), (1,4), (2,3), (2,4), (3,4). Consequently, and for each TRP, the UE may indicate which two beams that should be applied using log2(6) bits indicating an integer from 1 to 6, i.e., reporting Ike {1,2, 3, 4, 5, 6}. This equates to a pre-defined compressed sorting scheme; the sorting is not explicitly signaled, but predefined. The sorting scheme is compressed and would not allow for, e.g., signaling the beam with the higher beam index before the beam with the smaller beam index, e.g., a beam selection of (3,2) cannot be signaled. It is now assumed, as convention, that the first element in Ckshould be applied to the smaller beam-number in the beam pair indicated by Ik. For example, a report to the first TRP I1= 3, C1= (2, -5) (C1generally includes complex numbers; but for simplification the imaginary parts are omitted in this discussion) implies that TRP 165 should activate beams 1 and 4 (beams 211 and 214, marked in bold in FIG. 4); i.e., the third pair above where beam 1 should have weight 2 and beam 4 should have weight -5. With this convention, note that there is never any confusion which beam that is associated with the coefficients in C1. Altogether, the UE 102 needs to report 2 log2(6) bits for the beam selections 401, 402 I1, 12, respectively and 4 complex numbers X1... X4 for each set of antenna weights 411, 412, C1, C2(cf. FIG. 5). For instance, in the illustration, the TRP 166 activates the beam 3 and 4, i.e., TX beams 217, 218.

[0067] Various techniques are based on the finding that in some situations, the network may like to serve a UE from a single TRP, so that the reports I±and I2are not permissible reports. That is, the elements in I±and I2may either belong to the set {1,2, 3, 4}, or {5, 6, 7, 8}, but not a combination thereof.

[0068] Various techniques are based on the further finding that it may be of interest for the network to have flexibility to choose between the precoder for different TRPs. This situation may for example occur whenever the network has multiple UEs to serve, and some beams are occupied by other UEs. This increases the size of the feedback message. For example, for a first transmission layer, the UE needs to report two index-sets and two coefficient sets, i.e., one for each TRP.

[0069] This flexibility is addressed by the techniques disclosed hereinafter. According to various examples, multiple beam selections (e.g., I±and / 2) are reported by the UE to the cellular network. However, instead of reporting completely independent antenna weights for each of the multiple beam selections, the antenna weights reported for each TX beam of the multiple beam selections include one or more shared antenna weights. A shared antenna weight is an antenna weight that is jointly assigned to TX beams of multiple different beam selections. For instance, it may be applicable to a first TX beam of a first beam selection and to a second TX beam of a second beam selection. Thus, the shared antenna weights are, in other words, reused across multiple beam selections. This enables reducing the signaling overhead for the one or more feedback messages.

[0070] Next, referring to FIG. 6, use of shared antenna weights is exemplified. Here, a single coefficient set C is consided, i.e., using only shared antenna weights (in general, only some antenna weights may be shared antenna weights, i.e., a mix of shared and non-shared antenna weights is possible or even necessary, e.g., when beam selections include a different count of TX beams). There is only a single coefficient report C. The coefficients in C forming the shared antenna weights are computed in such a way that it is irrelevant which TRP applies them. Assume that C = (2, -5) as before, and that TRP 165 should apply the coefficient 2 for beam 1 and -5 for beam 4. As such, it suffices to report the same feedback message 301 to TRP 165 as FIG. 4, namely, I1= 3 and C = (2,-5). However, assume now that TRP 166 should activate beams 3 and 4, but that the coefficient 2 should be applied to beam 4 while the coefficient -5 should be applied to beam 3. I.e., the sorting of C should be inverted. That is, it is no longer true that the first coefficient in C should be applied to the smaller beam index for I2. Thus, additional information needs to be signaled. Various options are conceivable. Some options are explained below.

[0071] Firstly, the sorting of the beam selection I2of the feedback message 302 may be explicitly signaled (other than for the feedback message 301 where the sorting - due to the compression - is not explicitly signaled, but rather predefined and compressed). This gives the freedom to adjust the sorting beyond the sorting in a predefined, compressed sorting scheme used for I1. For instance, the actual pair (4,3) - i.e., including the sorting - is included in the feedback message 302 and not only the index 6 which corresponds to (3,4). There are 12 ordered pairs of selecting 2 elements from a list of 4 without repeats. In general, selecting M elements from N without repeats can be done in= N(N~ 1) ■■■ QV - M + 1) ways. Altogether, in the

[0072]

[0073] example of FIG. 6, the number of transferred information bits is for representing I1and I2is

[0074]

[0075] where pog2is the number of information bits for representing I1using the predefined,

[0076]

[0077] compressed sorting that requires a certain order of the selected TX beams; and where M l is the number of information bits for representing I2explicitly including the sorting. Here, [x ] is the smallest integer larger or equal to x (“ceiling”-function). In other words, an information element indicative of / 1(i.e., a first beam selection) includes a certain number of information bits and another information element indicative of I2(i.e., a second beam selection) includes another certain number of information bits, wherein one of the information elements is smaller than the other information element. (The number of signaling bits to carry these information bits may be affected by lower-layer compression; this is out of scope of the discussion here). The configurations used for encoding the beam selections by these information elements are, accordingly, different. This is also shown in FIG. 7A. Importantly, one only needs M = 2 complex numbers to represent C, i.e., fewer than in FIG. 4 or FIG. 5. As representation of complex numbers are more voluminous, this is usually a saving compared with the case in FIG. 4 and FIG. 5.

[0078] Secondly, instead of explicitly signaling the sorting of the second beam selection (resulting in more information bits required for the information element indicative of the second beam selection), a mapping 430 of the antenna weights to the TX beams of the second beam selection may be signaled. This is shown in FIG. 7B. The mapping 430 indicates that the first shared antenna weight (denoted by the complex number X1) applies to the first TX beam of the second beam selection 402; while the second shared antenna weight (denoted by the complex number X2) applies to the first TX beam of the second beam selection 402.

[0079] As a general rule, there are various options of signaling the mapping. An example of signaling the mapping is illustrated in FIG. 7B. Here, the mapping is as a list of M integers (“2” and “1” in FIG. 7B). These integers are The mapping is a generally permutation of the integersl.... M. Since there are Ml permutations, the mapping can be coded using an information element with[log2M!] Information bits. In FIG. 7A as well as in FIG. 7B, the feedback messages 301, 302 include only a single respective shared information element (X1 and X2) for each shared antenna weight 411. These shared antenna weights 411 are associated with both beam selections 401, 402. This is different for the scenario of FIG. 8 where the information elements (X1 and X2) defining the shared antenna weights are included in both feedback messages 301, 302.

[0080] It is noted that in the scenario of FIG. 7A, FIG. 7B, and FIG. 8, the size of the beam selection 401 equals the size of the beam selection 402, i.e., two TX beams are selected respectively, e.g., TX beams 211, 215 for the first beam selection 401 and TX beams 217, 218 for the second beam selection 402 (cf. FIG. 6). Also, in the illustrated scenarios, all antenna weights are shared antenna weights. I.e., there aren’t any non-shared antenna weights. However, as a general rule, not all antenna weights need to be shared antenna weights. This is, in particular, an implication for scenarios in which the number of TX beams of the multiple beam selections differ from each other.

[0081] It is noted that in the scenario of FIG. 7A, FIG. 7B, and FIG. 8 multiple information elements are used to signal the beam selection 401 as well as the beam selection 402. In other implementations, a single information element is included in a single message, that single information element being indicative of, both, the beam selection 401 as well as the beam selection 402.

[0082] In such case (i.e., a single information element indicative of both beams selections), the number of coded bits is This does not require that the same TX beam

[0083]

[0084] indices are included in both beam selections, i.e., the same TX beams need not selected for both TRPs. Rather, the amount of information sent this way is the same as when using two information elements; however, the information is coded more effectively. Instead of using two information elements, i.e., = {1... and I2= {1... M! j, a single integer I12is used

[0085]

[0086] that ranges in 1... A lj. For example, I12= ^ + G2>!)■ This way, [ ] is only

[0087]

[0088]

[0089] used once instead of twice, and the total bit count may be decreased by one. Note that with the coding above, and I2can be recovered from I12by

[0090] h = Gi2 - l)mod + 1

[0091] I

[0092]

[0093] 2= | ( / i2 - 1) / © | + 1

[0094] L \A / J

[0095] where |%J returns the largest integer smaller or equal to x.

[0096] Generally, consider a count of the multiple first transmit beams is M1, and a count of the multiple second transmit beams is M2(generally, M1#= M2is possible; but it is also possible that M1= M2), and a count of the transmit beams of the first beam selection is N1, and a count of the transmit beams of the second beam selection is N2. Then, the first information element comprises pog2(^1)] information bits; and the second information element comprises

[0097] ©M2!information bits.

[0098] Note that this format is selected if N1> N2. If N2> N the coding l°g2(^2)] + is more compact, i.e., it generally requires less bits. In order words, the first

[0099]

[0100] information element uses the largest of N1and / V2and the second information element, the smallest.

[0101] Next, numerical tests illustrate the impact of using shared antenna weights on the system performance. For this, a single antenna UE is assumed, a single subcarrier, and a network which has sounded a total of N = 2N' beams, where each TRP has sounded N' beams. The channels from TRP 1 within the N' beams to the UE, i.e., the znvariables are represented by the row vector g1= [

[0102]

[0103] g},...,g^J while the channels from TRP 2 are represented by the row vector g2= [g2,...,g^J. It is assumed that the UE should report M beams per TRP. Let I1= {

[0104]

[0105] ni,n2,...,71^}, I2= {n2,n2,...,71^} denote the reported beam indices for TRPs 1 and 2, respectively, and C = {c!,c2,...,cM} the unique coefficient vector.

[0106] Then, the precoder construction is obtained by solving the following optimization problem ZM

[0107] |cm|2< P

[0108]

[0109] where

[0110] y g\c£

[0111]

[0112] f=l

[0113] In words, ykis just the received power if TRP k activates the beams indicated in the set Ikand uses the weight coefficients in C. Then, the optimization problem states that one should find the beam indices and coefficients that maximizes the minimum SNR if the network arbitrarily chooses to activate TRP 1 or 2. P denotes a TX power in arbitrary units. The constraint £"=1|cm|2< P enforces that the BS does not use more transmit power than P, where P is the maximum transmit power the BS is capable of.

[0114] In some embodiments, the inequality in the equations above is replaced by a strict equality, m=i\cm\2= P ■ Accordingly, the precoding vectors thus calculated represent directions. An alternative optimization could be to maximize the sum of the SNRs rather than maximizing the minimum one. Such optimization would read ZM

[0115] \cmI2< P.

[0116]

[0117] m=l

[0118] To optimize the expected rate (at high SNR), one could alternatively aim to solve the optimization ZM

[0119] \cmI2< P.

[0120]

[0121] m=l To demonstrate effectiveness, benchmarks are used to compare against the use of the shared antenna weights. Two different benchmarks, each one with its own operational meaning, are discussed below.

[0122] The first benchmark is discussed first. ZM

[0123] |c^|2< P

[0124] m=l

[0125] and ZM

[0126] \Cm \2P

[0127]

[0128] m=l

[0129] These two values represent the highest achievable received powers from TRPs 1 and 2 if the UE reports both an index and a coefficient set for each TRP individually. The first benchmark is produced by arguing that the network may now choose the highest of the two powers. Thus, TB, I = maxC / i,^)- Next, the second benchmark is discussed. Taking the highest value maxCy- ^) is somewhat counterproductive. If the goal of the system was to maximize the received power, then it would suffice for the UE to report the beam indices and coefficients for the TRP that offers the highest power. The whole point of reporting a setting for both TRPs is that it should offer flexibility for the network to choose a TRP. Therefore, the rationale of the second benchmark is that the network would choose one of the two TRPs with equal probability. Thus, the second benchmark is the average received power yB 2=

[0130]

[0131] Multiple performance metrics are possible.

[0132] Performance metric 1. After solving the optimization problem, the two values y±and y2(i.e., the received powers from TRPs 1 and 2 if TRP 1 would apply I1, C or TRP 2 would apply I2, C) need not to be equal. Performance metric 1 is here defined as the minimum of the two values; this is the received power which can be guaranteed to the network no matter if the network chooses to serve the UE from TRP 1 or 2. Formally, yP 1= min(y1,y2).

[0133] Performance metric 2. The second performance metric is in line with benchmark 1, namely, that the network would choose the better of the two TRPs. Thus, yP 2= max(y1,y2).

[0134] Performance metric 3. The first performance metric may be slightly pessimistic as oftentimes the network may choose the stronger of the two TRPs. A third metric is produced by arguing that the network chooses TRP based on other considerations than received power at the UE - similar to the arguments leading to benchmark 2. Thus, the average received power is the relevant metric. Formally yP 3=Ky^+y2\

[0135]

[0136] Finally, due to the nature of the optimization problem, in most cases, except for small values of M, we have y±= y2, so that yP 3= yP 2= yP 1.

[0137] Results are discussed for a first parameter setting. In a first parameter setting, M = N'. That is, antenna weights are reported for all sounded beams by the TRPs. In FIG. 9, FIG. 10, and FIG. 11, comparisons between the benchmarks and the performance metrics are plotted. In all cases, the underlying variables znare independent complex Gaussians. FIG. 9: The lower line gives the relation between the proposed method and separate coefficient reports for a case in which the network chooses the serving TRP based on other considerations than the received power at the UE; for example, the need for serving other UEs. The curve suggests that less than 1.5dB loss appears by compressing the reports into a single coefficient report, and for a large value of M = N', the loss converges to 1 dB. One may consider this to be the most fair comparison, and the one that should be regarded as the basis of evaluating the method. The upper line displays the relation between the absolutely best performance possible with two coefficient reports, and the received power offered by a single coefficient report when the TRP is chosen randomly.

[0138] FIG. 10: This plot shows the relation of the results with optimal choice of TRPs based on either a single report or two reports. As can be seen, there is about 2dB loss of only having a single report. But the rationale behind this comparison is that the network chooses TRP solely based on the received power at the UE. Thus, there is little motivation for the UE to send a jointly optimized coefficient report in the first place. Thus, the only difference to the upper curve of FIG. 9 occurs for small N'.

[0139] FIG. 11: In this case, the guaranteed performance is used as performance metric. The upper line shows the loss to the absolutely best one can achieve: two reports and optimal choice of TRPs. Thus, the plot shows “the largest loss that we can guarantee to not be exceeded by our method compared with the absolutely best one could have achieved”. The second line shows the results between what we can guarantee with random TRP selection based on two reports. Next, a second parameter setting is discussed. Here, N' = 2M. That is, coefficients for half of the sounded beams are reported. Results are shown in FIG. 12 (corresponding to FIG. 9), FIG.

[0140] 13 (corresponding to FIG. 10), and FIG. 14 (corresponding to FIG. 11), and a general conclusion is that the proposed method performs comparatively better in this case.

[0141] FIG. 15 schematically illustrates a communication system 150 according various examples. The UE 102 is connected to a cellular network 160 via a BS 161. The BS 161 controls two TRP 165, 166. The cellular network 160 also includes a further BS 162 including a further TRP 167 as well as a core network 151. The number of TRPs 165, 166 may vary. The cellular network 160 does not necessarily need to employ TRPs, i.e., the BSs may locally transmit and receive. It is not required in all scenarios that a BS has a separate TRP.

[0142] For instance, illustrated in FIG. 16 is an implementation of a BS 101 - e.g., implementing any one of the discussed BSs such as the BS 161 or the BS 162 - including a transmission interface 1012 that includes an antenna array 1013 including multiple transmit antennas. If the BSs has access to a TRP, the transmission interface 1012 including the antenna array 1013 is implemented by the TRP, e.g., in a remote location. The BS 101 also includes a processor 1011 and the memory 1015. The processor 1011 may load program code from the memory 1015 and execute the program code. The processor 1011, upon loading the program code, may execute the program code, causing the processor 1011 to perform techniques as disclosed herein, e.g.: configuring a beam control procedure at a UE; configuring reporting scheme for providing feedback messages upon monitoring for CSI reference signals, obtaining feedback messages, determining a transmit precoder, i.e., amplitude and phase for each of the antennas of one or antenna array such as the antenna array 1013, based on the feedback messages, etc.

[0143] FIG. 17 schematically illustrates the UE 102. The UE 102 includes a processor 1021, a transmission interface 1022, and a memory 1025. In the illustrated scenario the UE 102 includes a single antenna 1024; but may generally also include multiple antennas in an array. For instance, the UE may include two or more antennas in an antenna array. The processor 1021 may load program code from the memory 1025 and execute the program code. Executing the program code causes the processor 1021 to perform techniques as disclosed herein, e.g., obtaining a control message indicative of a configuration for beam control, e.g., a reporting configuration for providing feedback messages responsive to monitoring for channel state information reference signals; monitoring for the CSI reference signals; providing feedback messages based on such monitoring for the CSI reference signals; etc.

[0144] FIG. 18 is a flowchart of a method according to various examples. The method of FIG. 18 may be executed by a UE connected to a communications network, e.g., to a wireless local area network or to cellular network. For instance, the cellular network may be a 3GPP-specified cellular network. For sake of simplicity, reference is made to a cellular implementation. For instance, the method of FIG. 18 may be executed by a processor of the UE, upon loading and executing program code from a memory. The method of FIG. 18 may be executed by the processor 1021 of the UE 102, upon loading program code from the memory 1025 and upon executing the program code.

[0145] At box 905, a control message - e.g., a Layer 3 control message such as a Radio Resource Configuration (RRC) control message - indicative of configuration of a beam control procedure is obtained.

[0146] For instance, a reporting configuration for providing at least one feedback message based on monitoring for CSI reference signals may be configured. The CSI reference signals are transmitted by one or TRPs of the communications network. Each CSI reference signal is transmitted using a respective TX beam. The at least one feedback message is indicative of multiple beam selections from the plurality of transmit beams.

[0147] For instance, such reporting configuration may be associated with one or shared antenna weights that are indicated by the least one feedback message, the reporting configuration may allow or even mandate the UE to use such shared antenna weights. Without the reporting configuration allowing the UE to use such shared antenna weights, the UE may individually determine, for each beam selection, non-shared antenna weights for each selected beam of that particular beam selection.

[0148] Alternatively or additionally, the reporting configuration may activate using shared information elements in the at least one feedback message. Here, each shared information element may be associated with two or more of the multiple beam selections. Each of the shared information elements may be indicative of a respective shared antenna weights that is jointly assigned to multiple TX beams of the multiple beam selections of the plurality of transmit beams. Accordingly, in other words, a shared antenna weights are not signaled, to the communications network, redundantly multiple times (cf. FIG. 8); rather, respective information may only be signaled once, e.g., as has been previously explained in connection with, e.g., FIG. 7A as well as FIG. 7B (antenna weights 411 only included in the feedback message 301).

[0149] As previously discussed in connection with FIG. 7A, the information elements for indicating different beam selections differ from each other in some scenarios, i.e., are constructed in accordance with different configurations. The reporting configuration can be indicative of such differing configurations of the information elements indicative of the beam selections.

[0150] For instance, the reporting configuration can be indicative of using a predefined, compressed sorting scheme for indicating a first one of the multiple beam selection; and using an explicit sorting scheme for indicating a second one of the multiple beam selections. By doing so, there is the possibility to provide a single, sorted listing of the antenna weights to be used for each of the transmit beams in the first and second beam selections; a predefined mapping may then employed between the antenna weights and TX beams, e.g., a pre-defined 1:1 mapping, i.e., the first antenna weight is applied to the first TX beam in the first beam selection as well as to the first beam and the second beam selection, the second antenna weight is applied to the second beam in the first beam selection as well as to the second beam and the 2nd beam selection, and so forth. The reporting configuration may alternatively activated signaling of the mapping, as previously discussed in connection with FIG. 7B. Here, the same predefined sorting may be used for, both, the information element carrying the first beam selection as well as for the information element carrying the second beam selection. On the other hand, by varying the mapping of the antenna weights to the TX beams, it would be possible, e.g., that the first antenna weights is applied to the first TX beam in the first beam selection but to the second or third beam or any arbitrary TX beam in the second beam selection. A specific information element may be configured to carry that mapping.

[0151] The configuration at box 905 is not limited to a reporting configuration.

[0152] For example, at box 905, the UE may alternatively or additionally obtain an indication of one or more constraints associated with a received power imbalance between the multiple beam selections. Alternatively or additionally, the one or more constraints may be associated with other performance indicators. For example, one could consider an imbalance of the estimated achievable rates between the multiple beam selections, or with respect to the single-TRP activation case. Other performance parameters might be possible. Such constraints can be considered when signaling the antenna weights. For instance, the one or more constraints may include a maximum received power imbalance and / or a relative weighting of the received powers associated with different ones of the multiple beam selections. Based on such received power imbalance, a selection between (i) activation of multiple TRPs and / or data streams, and (ii) activation of a single TRP and / or single transmission layer is facilitated. If the imbalance of the received power exceeds a certain threshold, it may be beneficial to select (ii), to free-up the spectrum and / or TRP for serving other UEs.

[0153] Box 905 is optional. In some scenarios, the configuration may be (at least partly) predefined or pre-configured.

[0154] At box 910, the UE monitors for CSI reference signals that are transmitted by a first TRP of the cellular network using the plurality of TX beams. The UE attempts to receive the CSI reference signals transmitted by the first transmit point in a respective TX beam sweep. The respective time-frequency resources may be predefined or may be indicated by the configuration 905. Then, at box 920, the UE may optionally monitor for CSI reference signals that are transmitted by a 2nd transmit point of the communications network using a plurality of TX beams. The UE attempts to receive the CSI reference signals that are transmitted by the 2nd transmit point in the respective TX beam sweep. The respective time-frequency resources may be predefined or may be indicated by the configuration 905.

[0155] Box 920 is optional. In some scenarios, the UE may only monitor for CSI reference signals from a single transmit point, e.g., from a single BS of a 3GPP-specified cellular network. It is also possible that the UE monitors for CSI reference signals for more than 2 transmit points. For instance, the UE may monitor for CSI reference signals transmitted by 3 or 4 TRPs of a cellular network. Accordingly, box 920 may be duplicated a number of times.

[0156] At box 925, the UE provides one or more feedback messages. For instance, the UE may provide a single feedback message that includes all relevant information, i.e., All information elements required to indicate all beam selections and all information elements required to indicate all antenna weights. In other scenarios, the UE may provide multiple feedback messages, e.g., one feedback message associated with the monitoring at box 910 and another feedback message associated with the monitoring in box 920.

[0157] For instance, each beam selection may be associated with a respective feedback message. It would also be possible that each TRP is associated with a respective feedback message. For instance, if different beam selections pertain to different transmission layers, single feedback message may be used; while, if different beam selections pertain to different TRPs, multiple feedback messages may be used.

[0158] The at least one feedback message is indicative of multiple beam selections from all TX beams for which monitoring has been performed in box 910 and, optionally, at box 920.

[0159] The at least one feedback message is also indicative, for each of the multiple beam selections, of respective antenna weights for each TX beam and that beam selection. These antenna weights specify an amplitude scaling and phase relationship of the TX beams in each beam selection.

[0160] The at least one feedback message also includes one or more shared antenna weights. Each of the one or more shared antenna weights is jointly assigned to a respective TX beam of two or more of the multiple beam selections.

[0161] As a general rule, the multiple beam selections may be associated with different TRPs of the cellular network. This corresponds to a scenario in which box 910 as well as box 920 are executed. Here, different beam selections pertain to different TRPs. I.e., a given beam selection exclusively includes TX beams provided by that single TRP that is associated with the given beam selection. In such a scenario, multiple feedback messages may be provided, each of the multiple feedback messages including a respective beam selection. The shared antenna weights need not be included in each feedback message; rather, the shared antenna weights may only be included in a single one of the feedback messages, avoiding duplicate signaling. Such a scenario has been previously discussed in connection with FIG.

[0162] 7A and FIG. 7B; here, the shared antenna weights 411 are only included in the feedback message 301; but are not included in the feedback message 302.

[0163] Above, a scenario has been disclosed in which the multiple beam selections are associated with different TRPs of the cellular network. It is also possible that the multiple beam selections are associated with different transmission / data layers of a multi-antenna transmission from the communications network to the UE. In such a scenario, box 920 needs not to be executed. In some scenarios, the one or more feedback message is provided at box 925 may not be indicative of a beam selection for multiple transmit points, e.g., multiple TRPs - even if CSI reference signals have been monitor for multiple transmit points, i.e., even if box 910 as well as box 920 have both been executed. In particular, it may occur that a power imbalance between a received power from different transmit points exceeds a certain predefined threshold, e.g., as indicated by the configuration of box 905. Then, it may be possible to request muting of a particular one of the different transmit points in the one or more feedback messages.

[0164] For instance, the UE may obtain an indication of one or more constraints associated with a received power imbalance or performance parameter of a first received power with using the first beam selection and a second received power by using the second beam selection. Then, the predicted power imbalance can be compared against this constraint and if the constraint is not fulfilled, then the UE may request muting of a particular one of the different transmit points. Such a request for muting may be an explicit request, e.g., indicative of an identity of the to-be-muted transmit point. The request may also be an implicit request, e.g., by only indicating a beam selection and associated antenna weights for a not-to-be-muted transmit point and not providing respective feedback for the to-be-muted transmit point.

[0165] FIG. 19 is a flowchart of a method according to various examples. The method of FIG. 90 may be executed by a device of a communications network. For instance, the method of FIG. 19 may be executed by an AP of a wireless local area communications network; or by a BS or another radio-access-network (RAN) device of a cellular network. For sake of simplicity, reference is made to a cellular implementation. A UE is connected to the cellular network. For instance, the method of FIG. 19 may be executed by a processor (e.g., the processor 1011 of the BS 101) upon loading program code from a memory (e.g., the memory 1015 of the BS 101) and upon executing the program code. The method of FIG. 19 is inter-related to the method of FIG. 18.

[0166] At box 950, a control message indicative of a beam control configuration is provided to the UE. Box 950, accordingly, corresponds to box 905.

[0167] Box 950 is optional; the configuration may be predefined.

[0168] At box 955, transmission of CSI reference signals using multiple TX beams from a first TRP is triggered. Box 955, accordingly, corresponds to box 910 of the method of FIG. 18.

[0169] Triggering transmission of CSI reference signals can include providing a respective trigger message to a remote device, e.g., a remote TRP connected to a BS; triggering transmission of CSI reference signals can, alternatively, include, triggering local RF circuitry to transmit the CSI reference signals. Box 960 - an optional box - includes triggering transmission of CSI reference signals to the UE and from a second TRP. Box 960, accordingly, corresponds to box 920 of the method of FIG. 18.

[0170] At box 965, one or more feedback messages associated with the CSI reference signals transmitted previously at box 955 and optionally at box 960 are obtained. A feedback message is indicative of a respective beam selection and associated antenna weights for each selected TX beam; one or more shared antenna weights may be used. Box 965, accordingly, corresponds to box 925 of the method of FIG. 18.

[0171] At box 970, transmission of data signals may be triggered using at least one transmit precoder, e.g., if downlink (DL) data is scheduled for delivery to the UE. For instance, two TRPs may be triggered to transmit data signals using a respective transmit precoder. The one or more transmit precoders are determined in accordance with the one or more feedback messages 965.

[0172] Various options are conceivable for translating the beam selection and antenna weights of box 965 into transmit precoders, from using the exact requested beams and antenna weights to introducing some or complete deviation from the UE requested TX beams and precoders. FIG. 20 is a signaling diagram of signaling between the BS 161, the TRP 165, the TRP 166 as well as the UE 102.

[0173] At 5005, the BS 161, provides a control message 4005 indicative of a configuration associated with beam control to the UE 102. 5005 can, accordingly, implement box 905 of the method of FIG. 18 as well as box 950 of the method of FIG. 19.

[0174] The BS 161, at 5010, triggers the TRP 165 to transmit multiple CSI reference signals 4010 on a TX beam sweep. The UE monitors and ultimately receives the CSI reference signals 4010. Thus, 5010 implements box 910 and box 955.

[0175] The BS 161, at 5015, triggers the TRP 166 to transmit multiple CSI reference signals 4010 on a TX beam sweep. The UE 102 monitors and ultimately receives these CSI reference signals 4010. Thus, 5015 implements box 920 as well as box 960.

[0176] At 5020, the UE 102 provides one or feedback messages, in the illustrated scenario a single feedback message 4015 is provided. The BS 161 obtains the feedback message. Thus, 5020 implements box 925 as well as box 965.

[0177] Then, the BS 161 - e.g., responsive to DL data being scheduled in a TX buffer - configures precoders using respective control messages 4016 at 5025 at each TRP 165, 166 and, at 5030, triggers both TRP 165 as well as TRP 166 to transmit data signals 4020 using these TX precoders. Thus, 5025 and 5030 implement box 970.

[0178] Above, a scenario has been disclosed in which multiple TRPs transmit CSI reference signals 4010 using respective TX beam sweeps. Furthermore, a beam selection and associated antenna weights or signaled by the UE 102 for each of the TRPs 165, 166. Multiple beam selections are not only possible for spatially distanced transmit points, e.g., the TRPs 165, 166; but also for multiple data layers. This is shown in FIG. 21.

[0179] FIG. 21 is a signaling diagram of signaling between the BS 161 as well as the UE 102. FIG.

[0180] 21 generally corresponds to FIG. 20; however, in FIG. 21, the BS 161 transmits the CSI reference signals 4010 at 5010 and transmits the data signals 4020 at 5030 using multiple transmission layers, i.e., rank 2. Multiple TRPs are not involved.

[0181] Yet another scenario is shown in FIG. 22 which generally corresponds to FIG. 21: however, the BS 161 employs the TRP 165 to implement two transmission layers.

[0182] Summarizing, at least the following EXAMPLES have been disclosed.

[0183] EXAMPLE 1. A method for use in a wireless communication device connected to a communications network, the method comprising:

[0184] - monitoring for channel state reference signals transmitted by at least one transmit point of the communications network using a plurality of transmit beams, and

[0185] - providing, to the communication network, at least one feedback message based on said monitoring,

[0186] wherein the at least one feedback message is indicative of a first beam selection from the plurality transmit beams and further indicative of a second beam selection from the plurality transmit beams,

[0187] wherein the at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection,

[0188] wherein the antenna weights comprise one or more shared antenna weights, each one of the one or more shared antenna weights being jointly assigned to a respective transmit beam of the first beam selection and a respective transmit beam of the second beam selection. EXAMPLE 2. The method of EXAMPLE 1,

[0189] wherein the plurality of transmit beams comprise multiple first transmit beams associated with a first transmit point of the communications network,

[0190] wherein the plurality of transmit beams comprise multiple second transmit beams associated with a second transmit point of the communications network,

[0191] wherein the first beam selection is from the multiple first transmit beams, wherein the second beam selection is from the multiple second transmit beams.

[0192] EXAMPLE S. The method of EXAMPLE 2,

[0193] wherein the at least one feedback message comprises a first feedback message and a second feedback message,

[0194] wherein the first feedback message is indicative of the one or more shared antenna weights,

[0195] wherein the second feedback message is not indicative of the one or more shared antenna weights.

[0196] EXAMPLE 4. The method of EXAMPLE 1,

[0197] wherein the first beam selection is associated with a first layer of a multi-antenna transmission from the communications network to the wireless communication device, wherein the second beam selection is associated with a second layer of the multiantenna transmission.

[0198] EXAMPLE 5. The method of any one of EXAMPLES 1 to 4, wherein the at least one feedback message comprises, for each of the one or more shared antenna weights, a single respective shared information element associated with both the first beam selection and the second beam selection.

[0199] EXAMPLE 6. The method of any one of EXAMPLES 1 to 4,

[0200] wherein the at least one feedback message comprises, for each of the one or more shared antenna weights, a first information element associated with the first beam selection and a second information element associated with the second beam selection.

[0201] EXAMPLE 7. The method of any one of the preceding EXAMPLES,

[0202] Wherein the at least one feedback message comprises a single information element that is indicative of the first beam selection as well as of the second beam selection.

[0203] EXAMPLE 8. The method of any one of the preceding EXAMPLES, further comprising:

[0204] - obtaining (905), from the communications network, a control message indicative of a reporting configuration for providing the at least one feedback message.

[0205] EXAMPLE 9. The method of EXAMPLES 5 and 8,

[0206] wherein the reporting configuration activates use of the shared information elements. EXAMPLE 10. The method of EXAMPLE 8 or 9,

[0207] wherein the reporting configuration provides a first configuration of a first information element of the at least one feedback message for indicating the first beam selection, wherein the reporting configuration provides a second configuration of a second information element of the at least one feedback message for indicating the second beam selection,

[0208] wherein the first configuration is different than the second configuration.

[0209] EXAMPLE 11. The method of any one of EXAMPLES 8 to 10,

[0210] Wherein the reporting configuration activates used of a single information element that is indicative of the first beam selection as well as of the second beam selection.

[0211] EXAMPLE 12. The method of any one of the preceding EXAMPLES,

[0212] wherein the at least one feedback message comprises a first information element for indicating the first beam selection,

[0213] wherein the at least one feedback message comprises a second information element for indicating the second beam selection,

[0214] wherein a first configuration of the first information element is different than a second configuration of the second information element.

[0215] EXAMPLE 13. The method of EXAMPLE 12,

[0216] wherein the first information element signals each selected transmit beam using a first number of bits,

[0217] wherein the second information element signals each selected transmit beam using a second number of bits,

[0218] wherein the first number of bits is smaller than the second number of bits.

[0219] EXAMPLE 14. The method of EXAMPLE 2 or 3, and of EXAMPLE 12 or 13,

[0220] wherein a count of the multiple first transmit beams is M1,

[0221] wherein a count of the multiple second transmit beams is M2,

[0222] wherein a count of the transmit beams of the first beam selection is N1, wherein a count of the transmit beams of the second beam selection is N2, wherein the first information element comprises og2)] information bits, wherein the second information element comprises log2' information bits. EXAMPLE 15. The method of any one of the preceding EXAMPLI

[0223]

[0224] wherein the at least one feedback message comprises an information element indicative of a mapping of each of the one or more shared antenna weights to a respective one of the one or more transmit beams of the second beam selection.

[0225] EXAMPLE 16. The method of any one of the preceding EXAMPLES, further comprising:

[0226] - obtaining (905), from the communications network, an indication of one or more constraints associated with a received power imbalance or performance parameter of a first received power when using the first beam selection and a second received power when using the second beam selection,

[0227] wherein the antenna weights are in accordance with the one or more constraints. EXAMPLE 17. The method of EXAMPLE 16,

[0228] wherein the one or more constraints comprises a maximum received power imbalance. EXAMPLE 18. The method of EXAMPLE 16 or 17,

[0229] wherein the one or more constraints comprise a relative weighting of the first received power and the second received power.

[0230] EXAMPLE 19. The method of any one of EXAMPLES 1 to 18,

[0231] wherein a first count of the transmit beams of the first beam selection is different than a second count of the transmit beams of the second beam selection,

[0232] wherein the second count is larger than the first count,

[0233] wherein the antenna weights comprise a non-shared antenna weight exclusively assigned to one or more transmit beams of the second beam selection.

[0234] EXAMPLE 20. The method of any one of EXAMPLES 1 to 18,

[0235] wherein a first count of the transmit beams of the first beam selection is different than a second count of the transmit beams of the second beam selection,

[0236] wherein the second count is the same as the first count,

[0237] wherein the antenna weights do not comprise any non-shared antenna weights exclusively assigned to one or more transmit beams of the second beam selection.

[0238] EXAMPLE 21. A method of use in a device of a communications network to which a wireless communication device is connected, the method comprising:

[0239] - triggering at least one transmit point of the communications network to transmit channel state reference signals using a plurality of transmit beams,

[0240] - obtaining, from the wireless communication device, at least one feedback message, wherein the at least one feedback message is indicative of a first beam selection from the plurality of transmit beams and further indicative of a second beam selection from the plurality of transmit beams,

[0241] wherein the at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection, wherein the antenna weights comprise one or more shared antenna weights, wherein each of the one or more shared antenna weights is jointly assigned to a transmit beam of the first selection and a transmit beam of the second selection.

[0242] EXAMPLE 22. The method of EXAMPLE 21, further comprising:

[0243] - upon obtaining the at least one feedback message, triggering the at least one transmit point of the communications network to transmit data signals using at least one transmit precoder.

[0244] EXAMPLE 23. A method for use in a wireless communication device connected to a communications network, the method comprising:

[0245] - obtaining (905), from the communications network, a control message indicative of a reporting configuration for providing at least one feedback message based on monitoring for channel state reference signals transmitted by at least one transmit point of the communications network using a plurality of transmit beams, the at least one feedback message being indicative of multiple beam selections from the plurality of transmit beams, wherein the reporting configuration is associated with one or more shared antenna weights indicated by the at least one feedback message, each of the one or more shared antenna weights being jointly assigned to multiple beam selections from the plurality of transmit beams.

[0246] EXAMPLE 24. The method of EXAMPLE 23,

[0247] wherein the reporting configuration activates using shared information elements in the at least one feedback message that are each associated with two or more of the multiple beam selections and that are each indicative of a respective shared antenna weight jointly assigned to multiple transmit beams of multiple beam selections from the plurality of transmit beams. EXAMPLE 25. A method for use in a wireless communication device connected to a communications network, the method comprising:

[0248] - monitoring for channel state reference signals transmitted by multiple transmit points of the communications network using a plurality of transmit beams, and

[0249] - providing, to the communication network, at least one feedback message based on said monitoring,

[0250] wherein the at least one feedback message being indicative of a request for muting of at least one of the multiple transmit points.

[0251] EXAMPLE 26. The method of EXAMPLE 25, further comprising:

[0252] - obtaining, from the communications network, a control message indicative of a reporting configuration for providing the at least one feedback message,

[0253] wherein the reporting configuration allows the request for muting the at least one of the multiple transmit points.

[0254] EXAMPLE 27. The method of EXAMPLE 25 or 26, further comprising:

[0255] - obtaining (905), from the communications network, an indication of one or more constraints associated with a received power imbalance or performance parameter of a first received power when using a first beam selection and a second received power when using the second beam selection, EXAMPLE 28. A wireless communication device connectable to a communications network and comprising circuitry configured to:

[0256] - monitor for channel state reference signals transmitted by at least one transmit point of the communications network using a plurality of transmit beams, and

[0257] - provide, to the communication network, at least one feedback message based on said monitoring,

[0258] wherein the at least one feedback message is indicative of a first beam selection from the plurality transmit beams and further indicative of a second beam selection from the plurality transmit beams,

[0259] wherein the at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection,

[0260] wherein the antenna weights comprise one or more shared antenna weights, each one of the one or more shared antenna weights being jointly assigned to a respective transmit beam of the first beam selection and a respective transmit beam of the second beam selection. EXAMPLE 29. The wireless communication device of EXAMPLE 28, wherein the circuitry is configured to execute the method of any one of EXAMPLES 1 to 20.

[0261] EXAMPLE 30. A device of a communications network to which a wireless communication device is connectable, the device comprising circuitry configured to:

[0262] - trigger at least one transmit point of the communications network to transmit channel state reference signals using a plurality of transmit beams,

[0263] - obtain, from the wireless communication device, at least one feedback message, wherein the at least one feedback message is indicative of a first beam selection from the plurality of transmit beams and further indicative of a second beam selection from the plurality of transmit beams,

[0264] wherein the at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection,

[0265] wherein the antenna weights comprise one or more shared antenna weights, wherein each of the one or more shared antenna weights is jointly assigned to a transmit beam of the first selection and a transmit beam of the second selection.

[0266] EXAMPLE 31. The device of EXAMPLE 30, wherein the device is a base station of a cellular network.

[0267] EXAMPLE 32. The device of EXAMPLE 30 or 31, wherein the circuitry is configured to execute the method of EXAMPLE 21 or 22.

[0268] EXAMPLE 33. A wireless communication device connectable to a communications network, the wireless communication device comprising circuitry configured to:

[0269] - obtain (905), from the communications network, a control message indicative of a reporting configuration for providing at least one feedback message based on monitoring for channel state reference signals transmitted by at least one transmit point of the communications network using a plurality of transmit beams, the at least one feedback message being indicative of multiple beam selections from the plurality of transmit beams, wherein the reporting configuration is associated with one or more shared antenna weights indicated by the at least one feedback message, each of the one or more shared antenna weights being jointly assigned to multiple beam selections from the plurality of transmit beams.

[0270] EXAMPLE 34. The wireless communication device of EXAMPLE 33, wherein the circuitry is configured to execute the method of EXAMPLE 23 or 24.

[0271] EXAMPLE 35. A wireless communication device connectable to a communications network, the wireless communication device comprising circuitry configured to:

[0272] - monitor for channel state reference signals transmitted by a multiple transmit points of the communications network using a plurality of transmit beams, and

[0273] - provide, to the communication network, at least one feedback message based on said monitoring,

[0274] wherein the at least one feedback message being indicative of a request for muting of at least one of the multiple transmit points.

[0275] EXAMPLE 36. The wireless communication device of EXAMPLE 35, wherein the circuitry is configured to execute the method of EXAMPLE 25 or 26.

[0276] Although the disclosure has been shown and described with respect to certain preferred embodiments, equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present disclosure includes all such equivalents and modifications and is limited only by the scope of the appended claims.

[0277] For illustration, various examples have been disclosed above in which multiple beam selections are determined and signaled by a UE, different ones of the multiple beam selections being associated with different TRPs. Similarly, multiple beam selections may be associated with multiple layers. It would also be possible that multiple beam selections are associated with different TRPs and with different layers.

[0278] For further illustration, various examples have been disclosed in connection with a scenario in which a wireless communication system is implemented by a cellular network to which a UE is connected. However, similar techniques may be readily employed for other types of communication systems, e.g., an implementation by a STA connected to a wireless local area network through an AP. In the same context, techniques have been disclosed in which the channel state reference signals are implemented by CSI reference signals. However, other types of channel state reference signals may be employed for channel sounding and beam control.

Claims

C L A I M S1. A method for use in a wireless communication device connected to a communications network, the method comprising:- monitoring for channel state reference signals transmitted by at least one transmit point of the communications network using a plurality of transmit beams, and- providing, to the communication network, at least one feedback message based on said monitoring,wherein the at least one feedback message is indicative of a first beam selection from the plurality transmit beams and further indicative of a second beam selection from the plurality transmit beams,wherein the at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection,wherein the antenna weights comprise one or more shared antenna weights, each one of the one or more shared antenna weights being jointly assigned to a respective transmit beam of the first beam selection and a respective transmit beam of the second beam selection.

2. The method of claim 1,wherein the plurality of transmit beams comprise multiple first transmit beams associated with a first transmit point of the communications network,wherein the plurality of transmit beams comprise multiple second transmit beams associated with a second transmit point of the communications network,wherein the first beam selection is from the multiple first transmit beams, wherein the second beam selection is from the multiple second transmit beams.

3. The method of claim 2,wherein the at least one feedback message comprises a first feedback message and a second feedback message,wherein the first feedback message is indicative of the one or more shared antenna weights,wherein the second feedback message is not indicative of the one or more shared antenna weights.

4. The method of claim 1,wherein the first beam selection is associated with a first layer of a multi-antenna transmission from the communications network to the wireless communication device, wherein the second beam selection is associated with a second layer of the multiantenna transmission.

5. The method of claim 1,wherein the at least one feedback message comprises, for each of the one or more shared antenna weights, a single respective shared information element associated with both the first beam selection and the second beam selection.

6. The method of claim 1,wherein the at least one feedback message comprises, for each of the one or more shared antenna weights, a first information element associated with the first beam selection and a second information element associated with the second beam selection.

7. The method of claim 1,wherein the at least one feedback message comprises a single information element that is indicative of the first beam selection as well as of the second beam selection.

8. The method of claim 1, further comprising:- obtaining (905), from the communications network, a control message indicative of a reporting configuration for providing the at least one feedback message.

9. The method of claim 8,wherein the reporting configuration provides a first configuration of a first information element of the at least one feedback message for indicating the first beam selection, 10. The method of claim 1,wherein the at least one feedback message comprises a first information element for indicating the first beam selection,wherein the at least one feedback message comprises a second information element for indicating the second beam selection,wherein a first configuration of the first information element is different than a second configuration of the second information element.

11. The method of claim 10,wherein the first information element signals each selected transmit beam using a first number of bits,wherein the second information element signals each selected transmit beam using a second number of bits,wherein the first number of bits is smaller than the second number of bits.

12. The method of claim 1,wherein the at least one feedback message comprises an information element indicative of a mapping of each of the one or more shared antenna weights to a respective one of the one or more transmit beams of the second beam selection.

13. The method of claim 1, further comprising:- obtaining (905), from the communications network, an indication of one or more constraints associated with a received power imbalance or performance parameter of a first received power when using the first beam selection and a second received power when using the second beam selection,wherein the antenna weights are in accordance with the one or more constraints.

14. The method of claim 1,wherein a first count of the transmit beams of the first beam selection is different than a second count of the transmit beams of the second beam selection,wherein the second count is larger than the first count,wherein the antenna weights comprises a non-shared antenna weights exclusively assigned to one or more transmit beams of the second beam selection.

15. The method of claim 1,wherein a first count of the transmit beams of the first beam selection is different than a second count of the transmit beams of the second beam selection,wherein the second count is the same as the first count,wherein the antenna weights does not comprise any non-shared antenna weights exclusively assigned to one or more transmit beams of the second beam selection.

16. A method of use in a device of a communications network to which a wireless communication device is connected, the method comprising:- triggering at least one transmit point of the communications network to transmit channel state reference signals using a plurality of transmit beams,- obtaining, from the wireless communication device, at least one feedback message, wherein the at least one feedback message is indicative of a first beam selection from the plurality of transmit beams and further indicative of a second beam selection from the plurality of transmit beams,wherein the at least one feedback message is further indicative of antenna weights for each transmit beam of the first beam selection and for each transmit beam of the second beam selection,wherein the antenna weights comprise one or more shared antenna weights, wherein each of the one or more shared antenna weights is jointly assigned to a transmit beam of the first selection and a transmit beam of the second selection.

17. The method of claim 16, further comprising:- upon obtaining the at least one feedback message, triggering the at least one transmit point of the communications network to transmit data signals using at least one transmit precoder.

18. A method for use in a wireless communication device connected to a communications network, the method comprising:- monitoring for channel state reference signals transmitted by multiple transmit points of the communications network using a plurality of transmit beams, and- providing, to the communication network, at least one feedback message based on said monitoring,wherein the at least one feedback message being indicative of a request for muting of at least one of the multiple transmit points.

19. The method of claim 18, further comprising:- obtaining, from the communications network, a control message indicative of a reporting configuration for providing the at least one feedback message,wherein the reporting configuration allows the request for muting the at least one of the multiple transmit points.

20. The method of claim 18, further comprising:- obtaining (905), from the communications network, an indication of one or more constraints associated with a received power imbalance or performance parameter of a first received power when using a first beam selection and a second received power when using the second beam selection.

Images