Reference signal reporting and user device selection

Abstract

Example embodiments may include devices, methods and computer programs relating to reference signal reporting and / or user device selection in systems that incorporate a reconfigurable intelligent surface An example method may comprise receiving, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations, measuring, based on the first configuration, respective sets of parameters associated with the respective RS combinations and determining a subset of the respective RS combinations based at least in part on their respective sets of parameters. The method may also comprise reporting, to the network node, an indication of the determined subset and their respective sets of parameters.

Description

[0001] Reference Signal Reporting and User Device Selection

[0002] Field

[0003] Example embodiments may relate to devices, methods and computer programs associated with reference signal reporting and user device selection in systems that may utilize reconfigurable intelligent surfaces (RISs).

[0004] Background

[0005] Reconfigurable intelligent surfaces (RISs) are being investigated as a technology for cellular communication systems. A RIS typically consist of antenna elements that can be configured according to different use cases. RISs offer a programmable antenna array solution for controlling the propagation of signals.

[0006] Summary

[0007] The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0008] A first aspect provides a first apparatus, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: receive, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations; measure, based on the first configuration, respective sets of parameters associated with the plurality of RS combinations; determine a subset of the plurality of RS combinations based at least in part on their respective sets of parameters; and report, to the network node, an indication of the determined subset and their respective sets of parameters.

[0009] In some examples, one RS of a particular RS combination is associated with a beam of the network node and another RS of the particular RS combination is associated with a beam of a reconfigurable intelligent surface, RIS. In some examples, the plurality of RS combinations comprise combinations of channel state information reference signals, CSI-RS. In some examples, the subset is determined based on at least one of: the first configuration; or a pre-configuration of the first apparatus. In some examples, the respective sets of parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value. In some examples, ordering the plurality of RS combinations is based, at least in part, on their associated RI values, wherein the subset comprises up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values. In some examples, RS combinations having the same RI value are ordered based on their associated at least one CQI value. In some examples, the determined subset includes at least a first RS combination and a second RS combination which are adjacent in the order, and the reported indication comprises at least: an indication of the first RS combination and its associated RI and at least one CQI value, and an indication of the second RS combination, its associated RI value and at least one differential CQI value. In some examples, the at least one differential CQI value is determined based on the difference between the at least one CQI value associated with the second RS combination and the at least one CQI value associated with the first RS combination, the at least one differential CQI value being represented using fewer bits than the at least one CQI value associated with the second RS combination. In some examples, the determined subset includes at least one RS combination associated with first and second CQI values, and the reported indication comprises at least an indication of said at least one RS combination, its associated RI value, its associated first CQI value and a differential CQI value in place of the second CQI value, wherein the differential CQI value is determined based on the difference between the first and second CQI values and is represented using fewer bits than the second CQI value. In some examples, the reported indication comprises a representation of the at least one CQI value represented using a first number of bits; and the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further causes the first apparatus to: re-measure the respective sets of parameters associated with the plurality of RS combinations; and report, to the network node, an updated indication comprising a representation of the at least one CQI value represented using a second, larger, number of bits. In some examples, the determined subset includes only RS combinations having an associated RI value greater than one. In some examples, the first apparatus is comprised by a user device. A second aspect provides a method of a first apparatus comprising: receiving, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations; measuring, based on the first configuration, respective sets of parameters associated with the plurality of RS combinations; determining a subset of the plurality of RS combinations based at least in part on their respective sets of parameters; and reporting, to the network node, an indication of the determined subset and their respective sets of parameters.

[0010] In some examples, the second aspect may comprise other features relating to the first aspect.

[0011] A third aspect provides a computer program product comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the second aspect.

[0012] A fourth aspect provides a computer program product embodied on a non- transitory distribution medium readable by a computer and comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the second aspect.

[0013] A fifth aspect provides an apparatus comprising: means for receiving, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations; means for measuring, based on the first configuration, respective sets of parameters associated with the plurality of RS combinations; means for determining a subset of the plurality of RS combinations based at least in part on their respective sets of parameters; and means for reporting, to the network node, an indication of the determined subset and their respective sets of parameters. In some examples, the means may comprise at least one processor and at least one memory including computer program code configured to, with the at least one processor, cause the performance of the apparatus. The fifth aspect may comprise other features relating to the first aspect. A sixth aspect provides second apparatus, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a plurality of user devices, a first configuration for causing the plurality of user devices to measure a plurality of reference signal, RS, combinations associated with respective beam combinations to determine respective sets of parameters; cause transmission of the plurality of RS combinations using their associated respective beam combinations; receive, from the plurality of user devices, respective reports comprising indications of respective subsets of the respective RS combinations and their respective sets of parameters; and determine, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to the subset of user devices.

[0014] In some examples, one RS of a particular RS combination is transmitted using a beam of the network node and another RS of the particular RS combination is caused to be transmitted or reflected using a beam of the RIS. In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: transmit a second configuration to the RIS for causing the RIS to transmit or reflect the subsequent data to the subset of user devices using the at least one selected beam. In some examples, the plurality of RS combinations comprise respective combinations of channel state information reference signals, CSI-RS. In some examples, the respective sets of parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value. In some examples, the first configuration causes the user devices to determine their respective subsets by: ordering the plurality of RS combinations based, at least in part, on their associated RI values, and including in the subset up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values. In some examples, the first configuration causes the user devices to order the plurality of RS combinations having the same RI value based on their associated at least one CQI value.

[0015] In some examples, the first configuration causes the user devices to report, for first and second RS combinations which are adjacent in the order, at least: an indication of the first RS combination, its associated RI and at least one CQI value, and an indication of the second RS combination, its associated RI value and at least one differential CQI value. In some examples, the first configuration causes the user devices to determine the at least one differential CQI value based on the difference between the at least one CQI value associated with the second RS combination and the at least one CQI value associated with the first RS combination, the at least one differential CQI value being represented using fewer bits than the at least one CQI value associated with the second RS combination. In some examples, the first configuration causes the user devices to report, for at least one RS combination associated with first and second CQI values, at least: an indication of said at least one RS combination, its associated RI value, its associated first CQI value and a differential CQI value in place of the second CQI value, wherein the differential CQI value is determined based on the difference between the first and second CQI values and is represented using fewer bits than the second CQI value. In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: provide, with the first configuration, a first instruction for causing the plurality of user devices to indicate, with their respective subsets, CQI values represented using a first number of bits; determine the subset of user devices based, at least in part, on the CQI values represented using the first number of bits; and transmit a second instruction for causing the subset of user devices to repeat the measurements and to indicate, in respective updated reports, CQI values represented using a second, larger, number of bits, wherein the at least one beam of the RIS is determined based on the respective updated reports. In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: detect an above-threshold number of user devices in a cell associated with the second apparatus, wherein the first instruction is provided in response to the detection. In some examples, the second apparatus is comprised by a network node.

[0016] A seventh aspect provides a method of a second apparatus comprising: transmitting, to a plurality of user devices, a first configuration for causing the plurality of user devices to measure a plurality of reference signal, RS, combinations associated with respective beam combinations to determine respective sets of parameters; causing transmission of the plurality of RS combinations using their associated respective beam combinations; receiving, from the plurality of user devices, respective reports comprising indications of respective subsets of the respective RS combinations and their respective sets of parameters; and determining, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to the subset of user devices. In some examples, the seventh aspect may comprise other features relating to the sixth aspect.

[0017] An eighth aspect provides a computer program product comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the seventh aspect.

[0018] A ninth aspect provides a computer program product embodied on a non- transitory distribution medium readable by a computer and comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the seventh aspect.

[0019] A tenth aspect provides a second apparatus comprising: means for transmitting, to a plurality of user devices, a first configuration for causing the plurality of user devices to measure a plurality of reference signal, RS, combinations associated with respective beam combinations to determine respective sets of parameters; means for causing transmission of the plurality of RS combinations using their associated respective beam combinations; means for receiving, from the plurality of user devices, respective reports comprising indications of respective subsets of the respective RS combinations and their respective sets of parameters; and means for determining, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to the subset of user devices. In some examples, the means may comprise at least one processor and at least one memory including computer program code configured to, with the at least one processor, cause the performance of the apparatus. The tenth aspect may comprise other features relating to the first aspect. An eleventh aspect provides a first apparatus, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: receive, from a network node, a first configuration for measuring a plurality reference signal, RS, combinations associated with respective beam combinations; measure, based on the first configuration, respective sets of parameters associated with the plurality of RS combinations, wherein the respective sets of parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value; order the plurality of RS combinations based on their respective RI values as a first priority, and on the throughput sum of their respective at least one CQI value(s) as a second priority; determine a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values; and report, to the network node, an indication of the determined subset and their respective sets of parameters.

[0020] In some examples, one RS of a particular RS combination is associated with a beam of the network node and another RS of the particular RS combination is associated with a beam of a reconfigurable intelligent surface, RIS. In some examples, the plurality of RS combinations comprise combinations of channel state information reference signals, CSI-RS. In some examples, the subset is determined based on at least one of: the first configuration; or a pre-configuration of the first apparatus. In some examples, the determined subset includes at least a first RS combination and a second RS combination which are adjacent in the order, and the reported indication comprises at least: an indication of the first RS combination and its associated RI and at least one CQI value, and an indication of the second RS combination, its associated RI value and at least one differential CQI value. In some examples, the at least one differential CQI value is determined based on the difference between the at least one CQI value associated with the second RS combination and the at least one CQI value associated with the first RS combination, the at least one differential CQI value being represented using fewer bits than the at least one CQI value associated with the second RS combination. In some examples, the determined subset includes at least one RS combination associated with first and second CQI values, and the reported indication comprises at least an indication of said at least one RS combination, its associated RI value, its associated first CQI value and a differential CQI value in place of the second CQI value, wherein the differential CQI value is determined based on the difference between the first and second CQI values and is represented using fewer bits than the second CQI value. In some examples, the reported indication comprises a representation of the at least one CQI value represented using a first number of bits; and the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further causes the first apparatus to: re-measure the respective sets of parameters associated with the plurality of RS combinations; and report, to the network node, an updated indication comprising a representation of the at least one CQI value represented using a second, larger, number of bits. In some examples, the determined subset includes only RS combinations having an associated RI value greater than one. In some examples, the first apparatus is comprised by a user device.

[0021] A twelfth aspect provides a method of a first apparatus comprising: receiving, from a network node, a first configuration for measuring a plurality reference signal, RS, combinations associated with respective beam combinations; measuring, based on the first configuration, respective sets of parameters associated with the plurality of RS combinations, wherein the respective sets of parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value; ordering the plurality of RS combinations based on their respective RI values as a first priority, and on the throughput sum of their respective at least one CQI value(s) as a second priority; determining a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values; and reporting, to the network node, an indication of the determined subset and their respective sets of parameters. In some examples, the twelfth aspect may comprise other features relating to the eleventh aspect.

[0022] A thirteenth aspect provides a computer program product comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the twelfth aspect.

[0023] A fourteenth aspect provides a computer program product embodied on a non- transitory distribution medium readable by a computer and comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the twelfth aspect.

[0024] A fifteenth aspect provides an apparatus comprising: means for receiving, from a network node, a first configuration for measuring a plurality reference signal, RS, combinations associated with respective beam combinations; means for measuring, based on the first configuration, respective sets of parameters associated with the plurality of RS combinations, wherein the respective sets of parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value; means for ordering the plurality of RS combinations based on their respective RI values as a first priority, and on the throughput sum of their respective at least one CQI value(s) as a second priority; means for determining a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values; and means for reporting, to the network node, an indication of the determined subset and their respective sets of parameters. In some examples, the means may comprise at least one processor and at least one memory including computer program code configured to, with the at least one processor, cause the performance of the apparatus. The fifteenth aspect may comprise other features relating to the eleventh aspect.

[0025] A sixteenth aspect provides a second apparatus, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a plurality of user devices, a first configuration for causing the plurality of user devices to: (i) measure a plurality of reference signal, RS, combinations associated with respective beam combinations to determine respective sets of parameters, wherein the parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value; (ii) order the plurality of RS combinations based on their respective RI values as a first priority, and on the throughput sum of their respective CQI value(s) as a second priority; and (iii) determine a subset of the plurality of RS combinations comprising up to a predetermined number of the respective RS combinations associated with the highest-ordered values; cause transmission of the plurality of RS combinations using their associated respective beam combinations; receive, from the plurality of user devices, respective reports comprising an indication of their respective subsets of the plurality of RS combinations and their respective sets of parameters; and determine, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to said subset of user devices.

[0026] In some examples, one RS of the respective RS combinations is transmitted using a beam of the network node and another RS of the plurality of RS combinations is caused to be transmitted or reflected using a beam of the RIS. In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: transmit a second configuration to the RIS for causing the RIS to transmit or reflect the subsequent data to the subset of user devices using the at least one selected beam. In some examples, the plurality of RS combinations comprise respective combinations of channel state information reference signals, CSI-RS. In some examples, the first configuration further causes the user devices to report, for first and second RS combinations which are adjacent in the order, at least: an indication of the first RS combination and its associated RI and at least one CQI value, and an indication of the second RS combination, its associated RI value and at least one differential CQI value. In some examples, the first configuration causes the user devices to determine the at least one differential CQI value based on the difference between the at least one CQI value associated with the second RS combination and the at least one CQI value associated with the first RS combination, the at least one differential CQI value being represented using fewer bits than the at least one CQI value associated with the second RS combination. In some examples, the first configuration further causes the user devices to report, for at least one RS combination associated with first and second CQI values, at least: an indication of said at least one RS combination, its associated RI value, its associated first CQI value and a differential CQI value in place of the second CQI value, wherein the differential CQI value is determined based on the difference between the first and second CQI values and is represented using fewer bits than the second CQI value. In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: provide, with the first configuration, a first instruction for causing the plurality of user devices to indicate, in their respective reports, CQI values represented using a first number of bits; determine the subset of user devices based on the respective reports; and transmit a second instruction for causing the subset of user devices to repeat the measurements and to indicate, in respective updated reports, CQI values represented using a second, larger, number of bits, wherein the at least one beam of the RIS is determined based on the respective updated reports. In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: detect an above-threshold number of user devices in a cell associated with the second apparatus, wherein the first instruction is provided in response to the detection. In some examples, the second apparatus is comprised by a network node.

[0027] A seventeenth aspect provides a method of a second apparatus comprising: transmitting, to a plurality of user devices, a first configuration for causing the plurality of user devices to: (i) measure a plurality of reference signal, RS, combinations associated with respective beam combinations to determine respective sets of parameters, wherein the parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value; (ii) order the plurality of RS combinations based on their respective RI values as a first priority, and on the throughput sum of their respective CQI value(s) as a second priority; and (iii) determine a subset of the plurality of RS combinations comprising up to a predetermined number of the respective RS combinations associated with the highest-ordered values; causing transmission of the plurality of RS combinations using their associated respective beam combinations; receiving, from the plurality of user devices, respective reports comprising an indication of their respective subsets of the plurality of RS combinations and their respective sets of parameters; and determining, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to said subset of user devices. In some examples, the seventeenth aspect may comprise other features relating to the sixteenth aspect. An eighteenth aspect provides a computer program product comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the seventeenth aspect.

[0028] A nineteenth aspect provides a computer program product embodied on a non- transitory distribution medium readable by a computer and comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the seventeenth aspect.

[0029] A twentieth aspect provides an apparatus comprising: means for transmitting, to a plurality of user devices, a first configuration for causing the plurality of user devices to: (i) measure a plurality of reference signal, RS, combinations associated with respective beam combinations to determine respective sets of parameters, wherein the parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value; (ii) order the plurality of RS combinations based on their respective RI values as a first priority, and on the throughput sum of their respective CQI value(s) as a second priority; and (iii) determine a subset of the plurality of RS combinations comprising up to a predetermined number of the respective RS combinations associated with the highest-ordered values; means for causing transmission of the plurality of RS combinations using their associated respective beam combinations; means for receiving, from the plurality of user devices, respective reports comprising an indication of their respective subsets of the plurality of RS combinations and their respective sets of parameters; and means for determining, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to said subset of user devices. In some examples, the means may comprise at least one processor and at least one memory including computer program code configured to, with the at least one processor, cause the performance of the apparatus. The twentieth aspect may comprise other features relating to the sixteenth aspect.

[0030] A twenty-first aspect provides a first apparatus, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: receive, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations; estimate respective Shannon Capacity values associated with the plurality of RS combinations; order the plurality of RS combinations based on their respective Shannon Capacity values; determine a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered Shannon Capacity values; and report, to the network node, an indication of the determined subset and their respective Shannon Capacity values.

[0031] In some examples, one RS of a particular RS combination is associated with a beam of the network node and another RS of the particular RS combination is associated with a beam of a reconfigurable intelligent surface, RIS. In some examples, the plurality of RS combinations comprise respective combinations of channel state information reference signals, CSI-RS. In some examples, the subset is determined based on at least one of: the first configuration; or a preconfiguration of the first apparatus. In some examples, the determined subset includes at least a first RS combination and a second RS combination which are adjacent in the order, and the reported indication comprises at least: an indication of the first RS combination and its associated Shannon Capacity value, and an indication of the second RS combination and a differential Shannon Capacity value based on the difference between the Shannon Capacity value associated with the second RS combination and the Shannon Capacity value associated with the first RS combination. In some examples, the first apparatus is comprised by a user device.

[0032] A twenty-second aspect provides a method of a first apparatus comprising: receiving, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations; estimating respective Shannon Capacity values associated with the plurality of RS combinations; ordering the plurality of RS combinations based on their respective Shannon Capacity values; determining a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered Shannon Capacity values; and reporting, to the network node, an indication of the determined subset and their respective Shannon Capacity values. In some examples, the twenty-second aspect may comprise other features relating to the twenty-first aspect.

[0033] A twenty-third aspect provides a computer program product comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the twenty-second aspect.

[0034] A twenty fourth aspect provides a computer program product embodied on a non- transitory distribution medium readable by a computer and comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the twenty-second aspect.

[0035] A twenty-fifth aspect provides a first apparatus comprising: means for receiving, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations; means for estimating respective Shannon Capacity values associated with the plurality of RS combinations; means for ordering the plurality of RS combinations based on their respective Shannon Capacity values; means for determining a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered Shannon Capacity values; and means for reporting, to the network node, an indication of the determined subset and their respective Shannon Capacity values. In some examples, the means may comprise at least one processor and at least one memory including computer program code configured to, with the at least one processor, cause the performance of the apparatus. The twenty-fifth aspect may comprise other features relating to the twenty-first aspect.

[0036] A twenty-sixth aspect provides a second apparatus, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a plurality of user devices, a first configuration for causing the plurality of user devices to: measure a plurality of reference signal, RS, combinations associated with respective beam combinations; estimate respective Shannon Capacity values associated with the plurality of RS combinations; order the plurality of RS combinations based on their respective Shannon Capacity values; and determine a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered Shannon Capacity values; cause transmission of the plurality of RS combinations using their associated respective beam combinations; receive, from the plurality of user devices, respective reports comprising an indication of their respective subsets and their respective Shannon Capacity values; and determine, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflect subsequent data to said subset of user devices.

[0037] In some examples, one RS of a particular RS combination is transmitted using a beam of the network node and another RS of the particular RS combination is caused to be transmitted or reflected using a beam of the RIS. In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: transmit a second configuration to the RIS for causing the RIS to transmit or reflect the subsequent data to the subset of user devices using the at least one selected beam. In some examples, the plurality of RS combinations comprise respective combinations of channel state information reference signals, CSI-RS. In some examples, the first configuration further causes the user devices to report, for first and second RS combinations which are adjacent in the order, at least: an indication of the first RS combination and its associated Shannon Capacity value, and an indication of the second RS combination, and a differential Shannon Capacity value based on the difference between the Shannon Capacity value associated with the second RS combination and the Shannon Capacity value associated with the first RS combination. In some examples, the second apparatus is comprised by a network node.

[0038] A twenty-seventh aspect provides a method of a first apparatus comprising: transmitting, to a plurality of user devices, a first configuration for causing the plurality of user devices to: measure a plurality of reference signal, RS, combinations associated with respective beam combinations; estimate respective Shannon Capacity values associated with the plurality of RS combinations; order the plurality of RS combinations based on their respective Shannon Capacity values; and determine a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered Shannon Capacity values; causing transmission of the plurality of RS combinations using their associated respective beam combinations; receiving, from the plurality of user devices, respective reports comprising an indication of their respective subsets and their respective Shannon Capacity values; and determining, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflect subsequent data to said subset of user devices. In some examples, the twenty-seventh aspect may comprise other features relating to the twenty-sixth aspect.

[0039] A twenty-eighth aspect provides a computer program product comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the twenty-seventh aspect.

[0040] A twenty ninth aspect provides a computer program product embodied on a non- transitory distribution medium readable by a computer and comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the method of the twenty-seventh aspect.

[0041] A thirtieth aspect provides a second apparatus comprising: means for transmitting, to a plurality of user devices, a first configuration for causing the plurality of user devices to: measure a plurality of reference signal, RS, combinations associated with respective beam combinations; estimate respective Shannon Capacity values associated with the plurality of RS combinations; order the plurality of RS combinations based on their respective Shannon Capacity values; and determine a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered Shannon Capacity values; means for causing transmission of the plurality of RS combinations using their associated respective beam combinations; means for receiving, from the plurality of user devices, respective reports comprising an indication of their respective subsets and their respective Shannon Capacity values; and means for determining, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflect subsequent data to said subset of user devices. In some examples, the means may comprise at least one processor and at least one memory including computer program code configured to, with the at least one processor, cause the performance of the apparatus. The thirtieth aspect may comprise other features relating to the twenty-sixth aspect.

[0042] Brief Description of the Drawings

[0043] Example embodiments will now be described by way of non-limiting example, with reference to the accompanying drawings, in which:

[0044] FIGs. 1 to 2 are block diagrams of example systems;

[0045] FIG. 3 illustrates an example RIS architecture;

[0046] FIG. 4 illustrates a system in accordance with an example embodiment;

[0047] FIGS. 5 to 9 are flow diagrams in accordance with example embodiments;

[0048] FIG. 10 is a message flow sequence in accordance with an example embodiment;

[0049] FIG. 11 illustrates part of a resource grid;

[0050] FIG. 12 illustrates reference data useful for understanding an implementation example;

[0051] FIG. 13 is a schematic diagram of a system that may be used to implement one or more example embodiments; and

[0052] FIG. 14 illustrates tangible media for storing computer-readable code which, when run by a computer, may perform methods according to example embodiments described herein.

[0053] Detailed Description

[0054] Reconfigurable intelligent surfaces (RISs) are being investigated in industry and academia as a technology for cellular communication systems that could complement existing radio infrastructures. Reconfigurable intelligent surfaces consist of antenna elements (typically cheap antenna elements) that can be configured according to different use cases. RIS offers a programmable antenna array solution for controlling the propagation of signals, for example by changing electrical and magnetic properties of the reflective surface of RIS depending on the use case. RIS may be able to provide a cost-effective alternative to deploying new gNBs / acquiring new spectrum in some circumstances. FIG. 1 is a block diagram of an example system indicated generally by the reference numeral 10. The system 10 comprises a network node 12 (alternatively referred to as a network device) such as a transmission-reception point, TRP, a base station or a gNB, a user device, UE, 14 (or some other mobile communication device or terminal device) and a reconfigurable intelligent surface, RIS, 16. The RIS 16 may comprise a plurality of antenna elements that can be configured according to a desired use case. One configuration corresponds to a beam (e.g. a narrow beam) pointing in a given direction.

[0055] In the system 10, the RIS 16 may be configured to redirect or reflect signals from the network node 12 towards the UE 14 and vice-versa, such that the network node 12 and the UE 14 can still communicate despite the presence of, for example, an obstacle 18. Thus, the system 10 provides a simple coverage enhancement use case of a RIS.

[0056] FIG. 2 is a block diagram of an example system, indicated generally by the reference numeral 20. The system 20 includes a network node 22, a UE 24 and a RIS 26 (similar to the network node 12, UE 14 and RIS 16 of the system 10, but omitting the obstacle 18). A line-of-sight (LOS) connection exists between the network node 22 and the UE 24. However, a second communication link is also available via the RIS 26. Providing an additional physical path can, for example, provide capacity improvement in the event of a dominant LOS channel.

[0057] In the system 20, the RIS 26 can be exploited to increase channel rank, and therefore increase spectral efficiency for applications requiring large throughputs in the downlink. More specifically, there are scenarios where the link between the network node 22 and the UE 24 exhibits a strong line-of- sight (LOS) component, and as a result, only rank one MIMO transmission is possible. This is especially true in higher frequency bands, where RISs may be deployed (a smaller wavelength facilitates RIS deployment due to the RIS antenna spacing being a fraction of the wavelength, resulting in smaller RIS array size). The RIS 26 provides an additional propagation path and could increase the channel rank to two by proper configuration. Note also that there are cases where the channel rank is greater than one without RIS (e.g., equal to two with cross polarized antennas), in which case providing a RIS can be exploited to increase the rank to three. Example embodiments described below relate to such a scenario.

[0058] FIG. 3 shows an example RIS architecture, indicated generally by the reference numeral 40. The RIS architecture 40 may be used to implement the RISs 16, 26 and 36 described above, for example. The RIS 40 may include a number of passive elements (shown in white in FIG. 4) and, possibly, one or more active elements (shown in grey in FIG. 3).

[0059] The passive elements of the RIS 40 provide a planar array of passive reflecting elements that can reflect incoming rays with adjustable phase shifts and gains. The passive nature of the reflecting elements results in low hardware costs, low energy consumption, and the ability to naturally operate in full-duplex (FD) mode. Phases of the passive elements may be configured to reflect the incoming signal in the desired direction.

[0060] The active element(s) of the RIS 40 may be controlled by a RIS controller. The active elements may be used for functions such as communicating control messages between a RIS and a network node (such as any on the network nodes 12 and 22 described above) and / or for channel sensing.

[0061] FIG. 4 is a block diagram of a system, indicated generally by the reference numeral 40. The system 40 comprises a network node 42, first to fourth UEs 44A to 44D (UE1 to UE4), and a RIS 46.

[0062] The system 40 includes a quasi-static channel 47 between the network node 42 and the RIS 46 (since both entities are typically in a fixed location), a first set of network node-to-UE beams 48 and a second set of RIS-to-UE beams 49.

[0063] The system 40 shows a predefined grid of beams at both the BS and RIS. A tuple (BS beam, RIS beam, UE) or more can be selected that seeks to maximize the throughput in the cell in a signaling efficient manner.

[0064] Existing 3GPP channel state information (CSI) reporting mechanisms may be used to configure the system 40, but at the cost of a high signaling overhead. For example, assuming M network node beams 48 and N RIS beams 49, an existing 3GPP framework might allow the network node 42 to configure and instruct each of the plurality of UEs 44A to 44D to feedback x / V CSI reports. The network node 42 could then select the subset of UEs and BS / RIS beams that result in the highest data rate in the cell. This quickly becomes infeasible as it would require a lot of signaling in the uplink (UL) for even small values of M and N. For instance, with M = N=8 (as shown schematically in FIG. 4) each of the plurality of UEs 44A to 44D needs to feedback 64 CSI reports. Furthermore, there may be a large number of active UEs in the cell, not all of which benefit from the RIS 46. Having all such UEs feedback detailed CSI reports of RIS channels would unnecessarily overload their UL feedback channels.

[0065] Example embodiments relate to devices, methods and computer programs for improved reference signal, RS, and CSI reporting. Other example embodiments relate to devices, methods and computer programs for efficient selection of tuples (BS beam, RIS beam, UE) for improving data throughput in a cell.

[0066] FIG. 5 is a flow diagram showing operations 50 that may be performed by one or more example embodiments. The operations 50 may be performed by hardware, software, firmware or a combination thereof. The operations 50 may be performed by one, or respective, means, a means being any suitable means such as one or more processors or controllers in combination with computer-readable instructions provided on one or more memories.

[0067] The operations 50 may be performed by a UE. For example, with reference to FIG. 4, the operations 50 may be performed by one or more of the first to fourth UEs 44A to 44D in relation to the network node 42 and RIS 46.

[0068] A first operation 52 may comprise receiving, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations.

[0069] A second operation 54 may comprise measuring, for example based on the first configuration, respective sets of parameters associated with the respective RS combinations. A third operation 56 may comprise determining a subset of the respective RS combinations based at least in part on their respective sets of parameters.

[0070] In this context, a subset refers to a proper subset such that, in the case of MxN different RS combinations, the subset comprises a number less than MxN and, in some cases, much less than MxN.

[0071] A fourth operation 58 may comprise reporting, for example to the network node, an indication of the determined subset and their respective sets of parameters.

[0072] In some example embodiments, one RS of a particular RS combination is associated with a beam of the network node and another RS of the particular RS combination is associated with a beam of the RIS.

[0073] Referring to FIG. 4, the second operation 54 effectively measures two-dimensional channel characteristics for each RS combination, one dimension associated with a beam 48 of the network node 42 and another dimension associated with the channel 47 between the network node and the RIS 46 and the beam 49 of the RIS.

[0074] Assuming each RS combination comprises first and second RSs, the first and second RSs may be transmitted substantially simultaneously, for example using adjacent time-frequency resources on a resource grid.

[0075] For example, FIG. 11 illustrates part of a resource grid 1100 and indicates a first arrangement 112 whereby the first and second RSs are transmitted simultaneously using adjacent sub-carriers, SI, S2, at a common time slot, tl. FIG. 11 also illustrates a second, alternative, arrangement 114 whereby the first and second RSs are transmitted using a common sub-carrier, S2, at adjacent time slots, tl, t2.

[0076] In some example embodiments, the plurality of RS combinations comprise respective combinations of channel state information reference signals (CSI-RS). For example, and with reference to FIG. 4, a first CSI-RS of a particular RS combination may be associated with one of the M network node beams 48 and a second CSI-RS of the particular combination may be associated with one of the N RIS beams 49.

[0077] In some example embodiments, the first configuration may comprise one or more resource sets. The resource set(s) may indicate (up to MxN) respective RS combinations and associated (up to MxN) beam combinations. The resource set(s) may identify or index the RS combinations and their associated beam combinations with respective CSI resource indicators (CRIs), or similar. The resource set(s), for the respective CRIs, may indicate time and frequency resources for causing the UE to measure the respective combination of first and second CSI-RSs, one of which is transmitted by a beam of the network node 42 and the other of which is transmitted or reflected using a beam of the RIS 49.

[0078] In this regard, and with reference to FIG. 4, the network node 42 may configure or cause the RIS 49 to transmit the second CSI-RSs using a respective one of its N beams by transmitting over channel 47 a second configuration which configures or causes the RIS 46 to transmit or reflect the second CSI-RS using said one of its N beams.

[0079] The respective CRIs may therefore correspond to (up to) MxN different beam combinations.

[0080] For example, with reference to FIG. 4, and assuming M=N=8, the first configuration may comprise 64 CRIs indicated in part as follows:

[0081] CRI Network Node RIS

[0082] CSI-RS Beam ( ) CSI-RS Beam ( / V)

[0083] #1 #1 #1 #2 #1

[0084] #2 #1 #1 #3 #2

[0085] #3 #1 #1 #4 #3

[0086] #4 #1 #1 #5 #4

[0087] #63 #8 #8 #7 #7 #64 #8 #8 #8 #8

[0088] Table 1 - CRIs and Different Combinations of CSI-RS

[0089] Note that sequential CRIs need not use sequential CSI-RSs or sequential beam indexes which are used here for ease of reference.

[0090] The first configuration may therefore configure a user device, for example the first UE 44A, to perform beam measurements similar to a known beam sweeping procedure but, in this case, using pairs of transmitted RSs, one by the network node 42 and the other by, or reflected by, the RIS 46.

[0091] Different beam combinations may be transmitted over different time instances or time periods according to the first configuration.

[0092] In some example embodiments, the subset of the third operation 56 may be determined based on at least one of the first configuration, or a pre-configuration of the first UE 44A. In the former case, the first configuration instructs the UE 44A how to determine the subset. In the latter case, the UE 44A is pre-configured, or hard-wired, with instructions on how to determine the subset.

[0093] Various methods for determining the subset are disclosed.

[0094] In some example embodiments, the respective sets of parameters may comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value. The values are indicative of throughput that can be achieved over channels associated with the different combinations of CSI-RSs. Accordingly, respective sets of measured RI and CQI values may be determined for at least some of the CRIs indicated in Table 1. To illustrate, Table 2 indicates example measured RI and CQI values for only some CRIs indicated in Table 1.

[0095] CRI RI CQI

[0096] #1 2 13, 7

[0097] #2 1 5

[0098] #3 2 15, 7 #4 2 15, 9.

[0099] Table 2 - CRIs and Measured Parameter Values

[0100] In some example embodiments, the subset of the third operation 56 may be determined by ordering the respective RS combinations, or CRIs, based, at least in part, on their associated RI values, at least as a first priority.

[0101] In some example embodiments, only CRIs for which the RI is greater than one may comprise part of the subset.

[0102] The subset may comprise up to a predetermined number of the respective CRI- RS combinations associated with the highest-ordered values. The predetermined number is referred to hereinafter as T. T may be a value less than (and in some cases much less than) MxN as mentioned above. For example, T may be 2 or 3 or any suitable number. T may be indicated with the first configuration or is preconfigured in the user device.

[0103] Taking only the four CRIs of Table 2, the result of the ordering, by decreasing RI, is shown in Table 3.

[0104] CRI RI CQI

[0105] #1 2 13, 7

[0106] #3 2 15, 7

[0107] #4 2 15, 9

[0108] #2 1 5

[0109] Table 3 - CRIs ordered by RI

[0110] If T = 3, only the first three CRIs (different CRI-RS combinations) having index #1, #3 and #4 will comprise the subset.

[0111] In some embodiments, the ordering may also take into account respective values of CQI as a second priority. For example, CRIs (respective CSI-RS combinations) having the same RI value may be ordered based on their associated at least one CQI value. Where RI = 2, there will be two CQI values. The result of the ordering (based on decreasing RI and CQI(s)) for this case is shown in Table 4.

[0112] CRI RI CQI

[0113] #4 2 15, 9

[0114] #3 2 15, 7

[0115] #1 2 13, 7

[0116] #2 1 5

[0117] Table 4 - CRIs ordered by RI and CQI(s)

[0118] If T = 3, the subset will comprise the same three CRIs (respective CRI-RS combinations) as for the Table 3 example. However, if T = 2, the subset will comprise a different subset of CRIs (CRIs #4, #3).

[0119] Assuming T = 2 and the order given in Table 4, the UE 44A will in the fourth operation 58 report to the network node an indication of the subset and their respective sets of parameters, as shown in Table 5.

[0120] CRI RI CQI

[0121] #4 2 15, 9

[0122] #3 2 15, 7

[0123] Table 5 - Subset of CRIs and Parameters Reported to Network Node

[0124] In some example embodiments, the reporting of the subset may use differential CQI reporting to reduce the number of bits used to encode said at least one CQI value(s).

[0125] For example, the determined subset may include at least a first CRI and a second CRI which are adjacent in the order, for example CRI #4 and CRI #3 in the Table 5 example. The reported indication may comprise at least an indication of the first CRI = #4, and its associated RI = 2, and two CQI values = 15, 9, as well as an indication of the second CRI = #3, its associated RI =2 and differential CQI values in place of 15, 7. The differential CQI values may be determined based on the difference between the CQI values associated with the second RS combination and the CQI values associated with the first RS combination, e.g., 15-15, 9-7. Taking the subset of Table 5 as an example, this becomes:

[0126] CRI RI CQI

[0127] #4 2 15, 9

[0128] #3 2 0, 2

[0129] Table 6 - Differential Reporting of CQI value(s)

[0130] Additionally, or alternatively, other forms of differential encoding of CQI value(s) may be performed.

[0131] For example, where a CRI is associated with first and second CQI values, the second CQI value may be substituted with a differential CQI value based on the difference between the first and second CQI values. For example, for CRI #4, the CQI values may change from 15, 9 to 15, 6 based on 15 - 9 = 6.

[0132] FIGs. 6 to 8 are flow diagrams relating to different implementation examples, each of which may use at least some features of the FIG. 5 example.

[0133] First Implementation Example

[0134] FIG. 6 is a flow diagram of a first implementation example, showing operations 60 that may be performed by one or more example embodiments. The operations 60 may be performed by hardware, software, firmware or a combination thereof. The operations 60 may be performed by one, or respective, means, a means being any suitable means such as one or more processors or controllers in combination with computer-readable instructions provided on one or more memories.

[0135] The operations 60 may be performed by a UE. For example, with reference to FIG. 4, the operations 60 may be performed by one or more of the UEs 44A to 44D in relation to the network node or device 42 and RIS 46. A first operation 62 may comprise receiving, for example from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations.

[0136] A second operation 64 may comprise measuring, for example based on the first configuration, respective sets of parameters associated with the plurality of RS combinations, wherein the respective sets of parameters comprise at least a rank index, RI, value and at least one channel quality indicator, CQI, value.

[0137] A third operation 66A may comprise ordering the plurality of RS combinations based on, as a first priority, their respective RI values and, as a second priority, their respective at least on CQI value(s).

[0138] A fourth operation 66B may comprise determining a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values.

[0139] In this context, a subset refers to a proper subset such that, in the case of MxN different RS combinations, the subset is less than MxN and, in some cases, much less than MxN.

[0140] A fifth operation 68 may comprise reporting, to the network node, an indication of the determined subset and their respective sets of parameters.

[0141] The reporting of the subset may use differential CQI reporting to reduce the number of bits used to encode said at least one CQI value(s), as per the FIG. 5 example.

[0142] Also, only CRIs for which the RI is greater than one may comprise part of the subset.

[0143] Second Implementation Example

[0144] FIG. 7 is a flow diagram of a second implementation example, showing operations 70 that may be performed by one or more example embodiments. The operations 70 may be performed by hardware, software, firmware or a combination thereof. The operations 70 may be performed by one, or respective, means, a means being any suitable means such as one or more processors or controllers in combination with computer-readable instructions provided on one or more memories.

[0145] The operations 70 may be performed by a UE. For example, with reference to FIG. 4, the operations 70 may be performed by one or more of the UEs 44A to 44D in relation to the network node or device 42 and RIS 46.

[0146] A first operation 72 may comprise receiving, for example from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations.

[0147] A second operation 74 may comprise measuring, for example based on the first configuration, respective sets of parameters associated with the plurality of RS combinations, wherein the respective sets of parameters comprise at least a rank index, RI, value and at least one channel quality indicator, CQI, value.

[0148] A third operation 76A may comprise ordering the plurality of RS combinations based on, as a first priority, their respective RI values and, as a second priority, the throughput sum of their respective at least one CQI value(s).

[0149] A fourth operation 76B may comprise determining a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values.

[0150] In this context, a subset refers to a proper subset such that, in the case of MxN different RS combinations, the subset is less than MxN and, in some cases, much less than MxN.

[0151] A fifth operation 78 may comprise reporting, to the network node, an indication of the determined subset and their respective sets of parameters.

[0152] In this second implementation example, the ordering may be different from the first implementation example in that the ordering of the plurality of RS combinations is based on the sum of the corresponding CQI(s) throughput, basically the throughput summed over the layers. Throughput per layer can be obtained from reference data stored at, or accessible to, the UE, for example using CQI tables in 3GPP documentation such as in section 5.2.2.1 of 3GPP TS 38.214 which is given by way of example only. The reference data (specific CQI table) may be provided or configured in advance by the network node. FIG. 12 illustrates the 4-bit CQI table 2 under this section which is useful for understanding the following examples.

[0153] To illustrate, Table 7 indicates respective sets of measured RI and CQI values for only some CRIs indicated in Table 1.

[0154] CRI RI CQI

[0155] #5 2 13, 12

[0156] #6 2 15, 7

[0157] #7 2 15, 9

[0158] #8 1 5.

[0159] Table 7 - CRIs and Measured Parameter Values

[0160] The third operation 76A may order the CRIs as indicated in Table 8 assuming use of the FIG. 12 reference data.

[0161] CRI RI CQI Throughput Sum

[0162] #5 2 13, 12 6.2266+5.5547 11.79 bits / s / Hz

[0163] #7 2 15, 9 7.4063+3.9023 11.3 bits / s / Hz

[0164] #6 2 15, 7 7.4063+2.7305 10.14 bits / s / Hz

[0165] #8 1 5 1.9141 1.9141 bits / s / Hz

[0166] Table 8 - CRIs ordered by RI and summed CQI(s) throughput.

[0167] Assuming T = 2 and the order given in Table 8, the user device may in the fifth operation 78 report to the network node an indication of the subset and their respective sets of parameters, as shown in Table 9. The network node upon receiving the Table 9 information can determine respective throughput(s) using the CQI values and the same FIG. 12 reference data.

[0168] CRI RI CQI

[0169] #5 2 13, 12

[0170] #7 2 15, 9

[0171] Table 9 - Subset of CRIs and Parameters Reported to Network Node

[0172] The reporting of the subset may use differential CQI reporting to reduce the number of bits used to encode said at least one CQI value(s), as per the FIG. 5 example.

[0173] Also, only CRIs for which the RI is greater than one may comprise part of the subset.

[0174] Third Implementation Example

[0175] FIG. 8 is a flow diagram of a third implementation example, showing operations 80 that may be performed by one or more example embodiments. The operations 80 may be performed by hardware, software, firmware or a combination thereof. The operations 80 may be performed by one, or respective, means, a means being any suitable means such as one or more processors or controllers in combination with computer-readable instructions provided on one or more memories.

[0176] The operations 80 may be performed by a UE. For example, with reference to FIG. 4, the operations 80 may be performed by one or more of the UEs 44A to 44D in relation to the network node or device 42 and RIS 46.

[0177] A first operation 82 may comprise receiving, for example from a network node, a first configuration for measuring respective sets of parameters associated with a plurality reference signal, RS, combinations, the plurality of RS combinations being associated with respective beam combinations. A second operation 85 may comprise estimating respective Shannon Capacity values associated with the plurality of RS combinations.

[0178] A third operation 86A may comprise ordering the plurality of RS combinations based on their respective Shannon Capacity values.

[0179] A fourth operation 86B may comprise determining a subset of the plurality of RS combinations comprising up to a predetermined number of the plurality of RS combinations associated with the highest-ordered Shannon Capacity values.

[0180] In this context, a subset refers to a proper subset such that, in the case of MxN different RS combinations, the subset is less than MxN and, in some cases, much less than MxN.

[0181] A sixth operation 88 may comprise reporting, to the network node, an indication of the determined subset and their respective sets of parameters.

[0182] In this context, Shannon Capacity may refer to the Shannon Multiple Input Multiple Output (MIMO) Capacity, C, which may be given as:

[0183] C (bps) = Iog2 (det(l2 + HH* H) / o2) where det(.) refers to the determinant of a matrix, I2 is the identity matrix of size 2x2, H refers to the downlink (DL) channel that can be estimated by the user device for each respective RS combination, or CRI, and o2refers to additive noise power over the antennas of the user device.

[0184] For example, the downlink channel, H, for respective RS combinations, or CRIs, may be estimated based on measurements of said RSs of the respective RS combinations. H may be considered a matrix representing the channel impulse response comprising phase shifts between receive and transmit antennas or beams.

[0185] In this third implementation example, the ordering may be different from the first and / or second implementation examples. To illustrate, Table 10 indicates different sets of estimated Shannon Capacity values for only some CRIs indicated in Table 1.

[0186] CRI Estimated Shannon Capacity (C)

[0187] #9 5.54 Gbps

[0188] #10 8.04 Gbps

[0189] #11 1.60 Gbps

[0190] #12 10.65 Gbps

[0191] Table 10 - CRIs and Estimated Shannon Capacity Values

[0192] The fourth operation 86A may order the CRIs as indicated in Table 11.

[0193] CRI Estimated Shannon Capacity (C)

[0194] #12 10.65 Gbps

[0195] #10 8.04 Gbps

[0196] #9 5.54 Gbps

[0197] #11 1.60 Gbps

[0198] Table 11 - CRIs ordered by Shannon Capacity Value

[0199] Assuming T = 2 and the order given in Table 11, the user device may in the fifth operation 88 report to the network node an indication of the subset and their respective sets of parameters, as shown in Table 12.

[0200] CRI Estimated Shannon Capacity (C)

[0201] #12 10.65 Gbps

[0202] #10 8.04 Gbps

[0203] Table 12 - Subset of CRIs and Parameters Reported to Network Node

[0204] The reporting of the subset may use differential reporting to reduce the number of bits used to encode the second CRI of first and second adjacent CRIs in the order, for example by reporting the difference between 10.65 and 8.04 Gbps = 2.61 Gbps.

[0205] Also, only CRIs for which the Shannon Capacity is greater than a threshold may comprise part of the subset.

[0206] In general summary, it will be appreciated that user devices, for example one or more of UEs 44A to 44D in FIG. 4, may feedback, for example in a single report, measurements for only a subset of the CRIs to the network node 42 which is more efficient than reporting measurements for all MxN CRIs.

[0207] The network node 42 may in turn use the reported CRI subsets from at least some of the UEs 44A to 44D associated with the network node's cell for efficient selection of tuples (BS beam, RIS beam, UE) for improved data throughput in the cell.

[0208] In this regard, the network node 42 is aware from the first configuration that a particular reported RS combination (or CRI) from a particular UE is associated with a particular combination of beams, one associated with the network node 42 and another associated with the RIS 46. The network node 42 may therefore identify, first, which UEs will benefit most from allocating subsequent data streams to the RIS 46 to increase data throughput; some UEs that will not benefit, or will benefit less than others, may therefore be excluded. The network node 42 may further determine which combination of network node beams 48 and RIS beams 49 provide that increased data throughput for the particular UE or UEs based on their reported subsets.

[0209] Operations that may be performed at the network node 42 will now be described.

[0210] FIG. 9 is a flow diagram showing operations 90 that may be performed by one or more example embodiments. The operations 90 may be performed by hardware, software, firmware or a combination thereof. The operations 90 may be performed by one, or respective, means, a means being any suitable means such as one or more processors or controllers in combination with computer-readable instructions provided on one or more memories. The operations 90 may be performed at a network node. For example, with reference to FIG. 4, the operations 90 may be performed at the network node 42 in relation to at least some of the UEs 44A to 44D and RIS 46.

[0211] A first operation 92 may comprise transmitting, to a plurality of user devices, a first configuration for causing the plurality of user devices to measure a plurality of reference signal, RS, combinations associated with respective beam combinations to determine respective sets of parameters.

[0212] A second operation 94 may comprise causing transmission of the plurality of RS combinations using their associated respective beam combinations.

[0213] A third operation 96 may comprise receiving, from the plurality of user devices, or at least some thereof, respective reports comprising indications of respective subsets of the plurality of RS combinations and their respective sets of parameters.

[0214] A fourth operation 98 may comprise determining, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to the subset of user devices.

[0215] In some example embodiments, one RS of a particular RS combination is transmitted using a beam of the network node and another RS of the particular RS combination is caused to be transmitted or reflected using a beam of the RIS.

[0216] In some example embodiments, another operation may comprise transmitting a second configuration to the RIS for causing the RIS to transmit or reflect the subsequent data to the subset of user devices using the at least one selected beam. The RIS transmitted / reflected data stream may be independent of the data stream transmitted by the network node, with both streams transmitted simultaneously.

[0217] In some example embodiments, the plurality of RS combinations may comprise respective combinations of channel state information reference signals, CSI-RS. In some example embodiments, as per the first and second implementation examples, the first configuration may cause measurement of respective sets of parameters comprising at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value. In such cases, the first configuration may cause the user devices to determine their respective subsets by: ordering the different RS combinations based, at least in part, on their associated RI values, and including in the subset up to a predetermined number of the respective RS combinations associated with the highest-ordered values.

[0218] With regard to the first implementation example, the first configuration may cause the user devices to order the plurality of RS combinations having the same RI value based on their associated at least one CQI value. In other words, the order is determined based on the RI value as a first priority and the at least one CQI value as a second priority. Where the RI value is 2, there may be first and second CQI values.

[0219] With regard to the second implementation example, the first configuration may cause the user devices to order the plurality of RS combinations having the same RI value based on the throughput sum of their associated at least one CQI values. In other words, the order is determined based on the RI value as a first priority and the throughput sum of the at least one CQI value as a second priority.

[0220] In some example embodiments, the first configuration may cause the user devices to report, for first and second RS combinations which are adjacent in the order, at least: an indication of the first RS combination, its associated RI and at least one CQI value, and an indication of the second RS combination, its associated RI value and at least one differential CQI value. The at least one differential CQI value may be determined based on the difference between the at least one CQI value associated with the second RS combination and the at least one (corresponding) CQI value associated with the first RS combination, the at least one differential CQI value being represented using fewer bits than the at least one CQI value associated with the second RS combination. Additionally, or alternatively, a differential CQI value based on the difference between first and second CQI values of the same RS combination (CRI) may replace the second CQI value. In some example embodiments, the first configuration may comprise a first instruction for causing the plurality of user devices to indicate, with their respective subsets, CQI values (whether original or differential) represented using a first number of bits. The first number of bits may be a relatively small number of bits. The subset of user devices may be determined based, at least in part, on the CQI values represented using the first number of bits. Subsequently, another operation may comprise transmitting a second instruction to the subset of user devices for causing said user devices to repeat the measurements and to indicate, in respective updated reports, CQI values (original or differential) represented using a second, larger, number of bits. The at least one beam of the RIS may be determined based on the respective updated reports.

[0221] In this example, a two-stage beam sweeping procedure is provided, wherein the first stage enables the network node to decide on the subset of user devices using a relatively coarse measurement of CQI value(s) and the second stage enables the network node to decide on the beam combinations using more fine-grained CQI values. This may be particularly advantageous when an above-threshold number of user devices are in the network node's cell as it avoids overloading the UL radio resources in the first stage. Accordingly, the first instruction may be transmitted in response to detecting an above-threshold number of user devices in the cell associated with the network node. The second stage reporting may use existing 3GPP frameworks or the reporting framework disclosed herein.

[0222] In some example embodiments, the first configuration may further indicate that the subset should only comprise RS combinations having an RI value greater than one.

[0223] With regard to the third implementation example, the first configuration may cause the user devices to order the different RS combinations based on their respective Shannon Capacity values, wherein the subset comprises up to a predetermined number of RS combinations having the highest Shannon Capacity values. In all such examples, the first configuration may further indicate to the plurality of user devices the predetermined number, T, of how many RS combinations should comprise the reported subset. Alternatively, T may be pre-configured at the user device.

[0224] FIG. 10 illustrates a message flow sequence for explaining example embodiments. FIG. 10 is described in relation to the network node 42, RIS 46 and first to fourth UEs 44A to 44D illustrated in FIG. 4

[0225] In an operation la, the network node 42 configures one or more resource sets indicating time and frequency resources for measuring respective RS combinations (respective CRIs) associated with respective beam combinations; the one or more resource sets will comprise at least part of a first configuration to be provided to the first to fourth UEs 44A to 44D.

[0226] In an operation lb, the network node 42 configures network node beams over the one or more resource sets; in other words, it determines which first RSs of the respective RS combinations will be transmitted over which network node beams

[0227] 48.

[0228] In an operation lc, the network node 42 prepares a configuration of RIS beams over the resource sets; in other words, it determines which second RSs of the respective RS combinations will be transmitted / reflected over which RIS beams

[0229] 49.

[0230] In an operation 2, the network node 42 transmits the configuration of RIS beams to the RIS 46.

[0231] In an operation 3, the network node 42 transmits a first configuration to the first to fourth UEs 44A to 44D. The first configuration comprises at least the resource sets determined in operation la. The first configuration may also comprise indication(s) of at least one of: what parameters the first to fourth UEs 44A to 44D should measure, how they should determine their respective subsets, whether or not to use differential (CQI) reporting, or a value for T. In an operation 4, the network node 42 commences transmission, for example over a sequence of time instances or time periods, of first RSs of each RS combination, or CRI, using an associated network node beam 48 and causes transmission or reflection of second RSs of each said RS combination using an associated RIS beam 49 according to the first configuration. The first to fourth UEs 44A to 44D measure the first and second RSs of each said combination in accordance with their received first configuration.

[0232] In operations 5 to 8, respective first to fourth reports are received by the network node 42 from the first to fourth UEs 44A to 44D. The respective first to fourth reports indicate respective subsets of the different RS combinations, or CRIs, and their measured parameters in accordance with one of the examples described above. The respective first to fourth reports may optionally comprise low-rate feedback reports based on differential representations of, for example, CQI values or Shannon Capacity values.

[0233] In an operation 9, the network node 42 determines a subset of the first to fourth UEs 44A to 44D to subsequently transmit data to. For example, the network node 42 may select a predetermined number 1 / 1 / of UEs having highest associated values of CQI, throughput sum of CQIs, or Shannon Capacity. For example, the network node 42 may only select UEs having highest associated values of CQI, throughput sum of CQIs, or Shannon Capacity, over a predetermined threshold. Having selected the subset of the first to fourth UEs 44A to 44D, the network node may determine, for the subset, which network node beam(s) 48 and RIS beam(s) 49 to use for transmitting subsequent independent data streams.

[0234] For example, it may be determined based on the first to fourth reports that the first and second UEs 44A, 44B have highest measured values of RI and CQI (or Shannon Capacity) over the third and fourth UEs 44C, 44D, which are excluded. For the first UE 44A, the highest measured values may correspond to a first RS combination, or CRI, associated with network node beam "1" and RIS beam "6". This provides a first (UE, BS beam, RIS beam) tuple. For the second UE 44B, the highest measured values may correspond to a second RS combination, or CRI, associated with network node beam "5" and RIS beam "3". This provides a second (UE, BS beam, RIS beam) tuple. In an operation 10, the network node 42 may perform a scheduling decision on the basis of the determination of the first and second tuples.

[0235] For example, network node beam "1" and RIS beam "6" may be assigned to the first UE 44A for 66.66% of the time and network node beam "5" and RIS beam "3" may be assigned to the second UE 44B for 33.33% of the time or thereabouts.

[0236] The remaining RIS beams may not be used.

[0237] The RIS 46 may receive a second configuration based on the scheduling decision which causes transmission of first and second data streams for the first UE 44A using network node beam "1" and RIS beam "6" on every first and second time instance (slot) and transmission of third and fourth data streams for the second UE 44B using network node beam "5" and RIS beam "3" on every third instance (slot).

[0238] In an operation 11, the network node transmits the second data stream for the first UE 44A to the RIS 46; in accordance with the second configuration, the RIS 46 transmits or reflects the second data stream to the first UE 44A using RIS beam "6" at the first and second time instances (slots). In an operation 12, the network node transmits the fourth data stream for the second UE 44B to the RIS 46; in accordance with the second configuration, the RIS 46 transmits or reflects the fourth data stream to the second UE 44B using RIS beam "3" on the third time instance (slot).

[0239] Example Apparatus

[0240] FIG. 13 shows an apparatus according to some example embodiments. The apparatus may be configured to perform the operations described herein, for example operations described with reference to any disclosed process. The apparatus comprises at least one processor 312 and at least one memory 314 directly or closely connected to the processor. The memory 314 includes at least one random access memory (RAM) and at least one read-only memory (ROM). Computer program code (software) is stored in the memory 314 (typically in ROM). The apparatus may be connected to a transmitter (TX) and a receiver (RX). The apparatus may, optionally, be connected with a user interface (UI) 318 for instructing the apparatus and / or for outputting data. The at least one processor 312, with the at least one memory 314 and the computer program code instruction 315 are arranged to cause the apparatus to at least perform at least the method according to any preceding process, for example as disclosed in relation to the flow diagrams and message sequences of FIGs. 5 to 10 and related features thereof.

[0241] FIG. 14 shows a non-transitory media 365 according to some embodiments. The non-transitory media 254 is a computer readable storage medium. It may be e.g. a CD, a DVD, a USB stick, a blue ray disk, etc. The non-transitory media 365 stores computer program code, causing an apparatus to perform the method of any preceding process for example as disclosed in relation to the flow diagrams and related features thereof.

[0242] Names of network elements, protocols, and methods are based on current standards. In other versions or other technologies, the names of these network elements and / or protocols and / or methods may be different, as long as they provide a corresponding functionality. For example, embodiments may be deployed in 2G / 3G / 4G / 5G networks and further generations of 3GPP but also in non-3GPP radio networks such as WiFi.

[0243] A memory may be volatile or non-volatile. It may be e.g. a RAM, a SRAM, a flash memory, a FPGA block ram, a DCD, a CD, a USB stick, and a blue ray disk.

[0244] If not otherwise stated or otherwise made clear from the context, the statement that two entities are different means that they perform different functions. It does not necessarily mean that they are based on different hardware. That is, each of the entities described in the present description may be based on a different hardware, or some or all of the entities may be based on the same hardware. It does not necessarily mean that they are based on different software. That is, each of the entities described in the present description may be based on different software, or some or all of the entities may be based on the same software. Each of the entities described in the present description may be embodied in the cloud. Implementations of any of the above described blocks, apparatuses, systems, techniques or methods include, as non-limiting examples, implementations as hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0245] Some embodiments may be implemented in the cloud.

[0246] It is to be understood that what is described above is what is presently considered the preferred embodiments. However, it should be noted that the description of the preferred embodiments is given by way of example only and that various modifications may be made without departing from the scope as defined by the appended claims.

Claims

CLAIMS1. A first apparatus, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: receive, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations; measure, based on the first configuration, respective sets of parameters associated with the plurality of RS combinations; determine a subset of the plurality of RS combinations based at least in part on their respective sets of parameters; and report, to the network node, an indication of the determined subset and their respective sets of parameters.

2. The first apparatus of claim 1, wherein one RS of a particular RS combination is associated with a beam of the network node and another RS of the particular RS combination is associated with a beam of a reconfigurable intelligent surface, RIS.

3. The first apparatus of claim 1 or claim 2, wherein the plurality of RS combinations comprise combinations of channel state information reference signals, CSI-RS.

4. The first apparatus of any preceding claim, wherein the subset is determined based on at least one of: the first configuration; or a pre-configuration of the first apparatus.

5. The first apparatus of any preceding claim, wherein the respective sets of parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value.

6. The first apparatus of claim 5, wherein the subset is determined by: ordering the plurality of RS combinations based, at least in part, on their associated RI values, wherein the subset comprises up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values.

7. The first apparatus of claim 6, whereinRS combinations having the same RI value are ordered based on their associated at least one CQI value.

8. The first apparatus of claim 7, wherein the determined subset includes at least a first RS combination and a second RS combination which are adjacent in the order, and the reported indication comprises at least: an indication of the first RS combination and its associated RI and at least one CQI value, and an indication of the second RS combination, its associated RI value and at least one differential CQI value.

9. The first apparatus of claim 8, wherein the at least one differential CQI value is determined based on the difference between the at least one CQI value associated with the second RS combination and the at least one CQI value associated with the first RS combination, the at least one differential CQI value being represented using fewer bits than the at least one CQI value associated with the second RS combination.

10. The first apparatus of any of claims 6 to 9, wherein the determined subset includes at least one RS combination associated with first and second CQI values, and the reported indication comprises at least an indication of said at least one RS combination, its associated RI value, its associated first CQI value and a differential CQI value in place of the second CQI value, wherein the differential CQI value is determined based on the difference between the first and second CQI values and is represented using fewer bits than the second CQI value.4311. The first apparatus of any of claims 6 to 10, wherein the reported indication comprises a representation of the at least one CQI value represented using a first number of bits; and the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further causes the first apparatus to: re-measure the respective sets of parameters associated with the plurality of RS combinations; and report, to the network node, an updated indication comprising a representation of the at least one CQI value represented using a second, larger, number of bits.

12. The first apparatus of any of claims 5 to 11, wherein the determined subset includes only RS combinations having an associated RI value greater than one.

13. The first apparatus of any preceding claim, wherein the first apparatus is comprised by a user device.

14. A second apparatus, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a plurality of user devices, a first configuration for causing the plurality of user devices to measure a plurality of reference signal, RS, combinations associated with respective beam combinations to determine respective sets of parameters; cause transmission of the plurality of RS combinations using their associated respective beam combinations; receive, from the plurality of user devices, respective reports comprising indications of respective subsets of the respective RS combinations and their respective sets of parameters; and44determine, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to the subset of user devices.

15. The second apparatus of claim 14, wherein one RS of a particular RS combination is transmitted using a beam of the network node and another RS of the particular RS combination is caused to be transmitted or reflected using a beam of the RIS.

16. The second apparatus of claim 14 or claim 15, wherein the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: transmit a second configuration to the RIS for causing the RIS to transmit or reflect the subsequent data to the subset of user devices using the at least one selected beam.

17. The second apparatus of any of claims 14 to 16, wherein the plurality of RS combinations comprise respective combinations of channel state information reference signals, CSI-RS.

18. The second apparatus of any of claims 14 to 17, wherein the respective sets of parameters comprise at least a rank index, RI, value and at least one Channel Quality Indicator, CQI, value.

19. The second apparatus of any of claims 14 to 18, wherein the first configuration causes the user devices to determine their respective subsets by: ordering the plurality of RS combinations based, at least in part, on their associated RI values, and including in the subset up to a predetermined number of the plurality of RS combinations associated with the highest-ordered values.

20. The second apparatus of claim 19, wherein the first configuration causes the user devices to order the plurality of RS combinations having the same RI value based on their associated at least one CQI value.

21. The second apparatus of claim 20, wherein the first configuration causes the user devices to report, for first and second RS combinations which are adjacent in the order, at least: an indication of the first RS combination, its associated RI and at least one CQI value, and an indication of the second RS combination, its associated RI value and at least one differential CQI value.

22. The second apparatus of claim 21, wherein the first configuration causes the user devices to determine the at least one differential CQI value based on the difference between the at least one CQI value associated with the second RS combination and the at least one CQI value associated with the first RS combination, the at least one differential CQI value being represented using fewer bits than the at least one CQI value associated with the second RS combination.

23. The second apparatus of any of claims 19 to 22, wherein the first configuration causes the user devices to report, for at least one RS combination associated with first and second CQI values, at least: an indication of said at least one RS combination, its associated RI value, its associated first CQI value and a differential CQI value in place of the second CQI value, wherein the differential CQI value is determined based on the difference between the first and second CQI values and is represented using fewer bits than the second CQI value.

24. The second apparatus of any of claims 19 to 23, wherein the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to:provide, with the first configuration, a first instruction for causing the plurality of user devices to indicate, with their respective subsets, CQI values represented using a first number of bits; determine the subset of user devices based, at least in part, on the CQI values represented using the first number of bits; and transmit a second instruction for causing the subset of user devices to repeat the measurements and to indicate, in respective updated reports, CQI values represented using a second, larger, number of bits, wherein the at least one beam of the RIS is determined based on the respective updated reports.

25. The second apparatus of claim 24, wherein the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: detect an above-threshold number of user devices in a cell associated with the second apparatus, wherein the first instruction is provided in response to the detection.

26. The second apparatus of any of claims 14 to 25, wherein the second apparatus is comprised by a network node.

27. A method of a first apparatus, comprising: receiving, from a network node, a first configuration for measuring a plurality of reference signal, RS, combinations associated with respective beam combinations; measuring, based on the first configuration, respective sets of parameters associated with the plurality of RS combinations; determining a subset of the plurality of RS combinations based at least in part on their respective sets of parameters; and reporting, to the network node, an indication of the determined subset and their respective sets of parameters.

28. A method of a second apparatus, comprising: transmitting, to a plurality of user devices, a first configuration for causing the plurality of user devices to measure a plurality of reference signal, RS,47combinations associated with respective beam combinations to determine respective sets of parameters; causing transmission of the plurality of RS combinations using their associated respective beam combinations; receiving, from the plurality of user devices, respective reports comprising indications of respective subsets of the plurality of RS combinations and their respective sets of parameters, the respective subsets being determined by the user devices based at least in part on the respective sets of parameters; and determining, based on the respective reports, a subset of the plurality of user devices and at least one selected beam of a reconfigurable intelligent surface, RIS, for transmitting or reflecting subsequent data to the subset of user devices.48

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