Method, apparatus and computer program

Abstract

A User Equipment: obtains configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the User

Description

[2] A communication network can be seen as a facility that enables communications between two or more communication devices or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network. A communication device may be provided with a service by an application server. [3] Such communication networks operate in accordance with standards, such as those provided by 3GPP (Third Generation Partnership Project) or ETSI (European Telecommunications Standards Institute). Examples of standards provided by 3GPP are the so-called 3GPP standards for cellular technology generations, such as 3GPP standards for 4G technology and 3GPP standards for 5G technology. SUMMARY [4] Some example embodiments of this disclosure will be described with respect to certain aspects. These aspects are not intended to indicate key or essential features of the various example embodiments of this disclosure, nor are they intended to be used to limit the scope of thereof. Other features, aspects, and elements will be apparent to a person skilled in the art in view of this disclosure. For example, it should be appreciated that further aspects may be provided by the combination of any two or more of the various aspects described below. [5] According to an aspect there is provided a user equipment comprising means for: obtaining configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the user equipment and with at least one uplink reference signal resource; determining power headroom values for the uplink signal transmission associated with each of the plurality of antenna ports of the user equipment; and sending, to at least one network node, based on the determined power headroom values and the configuration information, a power headroom report indicating the determined power headroom values associated with at least two of the plurality of antenna ports, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set. [6] Obtaining the configuration information may comprise at least one of: receiving the configuration information from the at least one network node; or obtaining the configuration information based on information hard coded at the user equipment. [7] The at least two of the plurality of antenna ports may be associated with different uplink reference signal resources of the same uplink reference signal resource set; or the at least two of the plurality of antenna ports may be associated with the same uplink reference signal resources of the same uplink reference signal resource set. [8] A number of power headroom fields comprised in the power headroom report may be based on the number of simultaneously transmitting antenna ports of the user equipment in the uplink direction. [9] The means may be further for: sending, to the at least one network node, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

[10] The configuration information may comprise at least one of: a first threshold value for determining at least one subset of the plurality of antenna ports; an indication of at least one subset of the plurality of antenna ports; a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; or a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

[11] The means may be further for: determining a power headroom value associated with each of the plurality of antenna ports; and determining, based on the second threshold value and the power headroom value associated with the each of the plurality of antenna ports, a number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report, wherein the sending the power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports is based on the determined number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report.

[12] The means may be further for: determining the at least one subset of the plurality of antenna ports, each subset comprising one or more antenna ports, wherein the power headroom report comprises, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the determined power headroom for the respective at least one subset of the plurality of antenna ports.

[13] Determining the at least one subset of the plurality of antenna ports may comprise one of: determining the at least one subset of the plurality of antenna ports based on the determined power headroom for each of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of the one or more antenna ports comprised in the subset is less than the first threshold value; or determining the at least one subset of the plurality of antenna ports based on the indication of the at least one subset of the plurality of antenna ports.

[14] The means may be further for: sending, to the at least one network node, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value, wherein the configuration information is received from the at least one network node, and wherein the first threshold value and / or the second threshold value is based on the indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

[15] The plurality of antenna ports may be comprised in a single subset, wherein a difference between the determined power headroom of the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

[16] The power headroom report may further comprise information indicating at least one of: a size of the power headroom report; a number of power headroom values comprised in the report; a number of antenna ports for which the power headroom is reported; a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

[17] The means may be further for: receiving, from the at least one network node, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the sent power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; and sending, to the at least one network node, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

[18] According to an aspect there is provided an apparatus comprising means for: receiving, from a user equipment, a power headroom report indicating power headroom values associated with at least two of a plurality of antenna ports of the user equipment, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set; and determining, based on the power headroom report, at least one transmission power for uplink transmission by the user equipment from at least one of the plurality of antenna ports.

[19] The at least two of the plurality of antenna ports may be associated with different uplink reference signal resources of the same uplink reference signal resource set; or the at least two of the plurality of antenna ports may be associated with the same uplink reference signal resources of the same uplink reference signal resource set.

[20] The means may be further for: sending, to the user equipment, configuration information for power headroom reporting, the configuration information being associated with uplink reference signal transmission from the plurality of antenna ports of the user equipment.

[21] The configuration information may comprise at least one of: a first threshold value for determining at least one subset of the plurality of antenna ports; an indication of at least one subset of the plurality of antenna ports; a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

[22] The power headroom report may comprise, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the power headroom associated with the respective at least one subset of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of one or more antenna ports comprised in the subset is less than the first threshold value.

[23] The means may be further for: receiving, from the user equipment, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction; determining, based on the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction, the at least one subset of the plurality of antenna ports; and sending, to the user equipment, the configuration information indicating the at least one subset of the plurality of antenna ports.

[24] The means may be further for: receiving, from the user equipment, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value; and determining the first threshold value and / or the user equipment’s preferred second threshold value based on the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

[25] The plurality of antenna ports may be comprised in a single subset, wherein a difference between the determined power headroom associated with the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

[26] The power headroom report may further comprise information indicating at least one of: a size of the power headroom report; a number of power headroom values comprised in the report; a number of antenna ports for which the power headroom is reported; a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

[27] The means may be further for: sending, to the user equipment, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the received power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; and receiving, from the user equipment, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

[28] According to an aspect, there is provided a user equipment comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to: obtain configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the user equipment and with at least one uplink reference signal resource; determine power headroom values for the uplink signal transmission associated with each of the plurality of antenna ports of the user equipment; and send, to at least one network node, based on the determined power headroom values and the configuration information, a power headroom report indicating the determined power headroom values associated with at least two of the plurality of antenna ports, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set.

[29] The at least one processor may cause the user equipment to: receive the configuration information from the at least one network node; and / or obtain the configuration information based on information hard coded at the user equipment.

[30] The at least two of the plurality of antenna ports may be associated with different uplink reference signal resources of the same uplink reference signal resource set; or the at least two of the plurality of antenna ports may be associated with the same uplink reference signal resources of the same uplink reference signal resource set.

[31] A number of power headroom fields comprised in the power headroom report may be based on the number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

[32] The at least one processor may further cause the user equipment to: send, to the at least one network node, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

[33] The configuration information may comprise at least one of: a first threshold value for determining at least one subset of the plurality of antenna ports; an indication of at least one subset of the plurality of antenna ports; a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; or a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

[34] The at least one processor may further cause the user equipment to: determine a power headroom value associated with each of the plurality of antenna ports; and determine, based on the second threshold value and the power headroom value associated with the each of the plurality of antenna ports, a number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report, wherein the at least one processor may be cause the user equipment to send the power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports based on the determined number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report.

[35] The at least one processor may further cause the user equipment to: determine the at least one subset of the plurality of antenna ports, each subset comprising one or more antenna ports, wherein the power headroom report comprises, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the determined power headroom for the respective at least one subset of the plurality of antenna ports.

[36] The at least one processor may cause the user equipment to: determine the at least one subset of the plurality of antenna ports based on the determined power headroom for each of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of the one or more antenna ports comprised in the subset is less than the first threshold value; or determine the at least one subset of the plurality of antenna ports based on the indication of the at least one subset of the plurality of antenna ports.

[37] The at least one processor may further cause the user equipment to: send, to the at least one network node, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value, wherein the configuration information is received from the at least one network node, and wherein the first threshold value and / or the second threshold value is based on the indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

[38] The plurality of antenna ports may be comprised in a single subset, wherein a difference between the determined power headroom of the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

[39] The power headroom report may further comprise information indicating at least one of: a size of the power headroom report; a number of power headroom values comprised in the report; a number of antenna ports for which the power headroom is reported; a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

[40] The at least one processor may further cause the user equipment to: receive, from the at least one network node, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the sent power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; and send, to the at least one network node, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

[41] According to an aspect there is provided an apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, a power headroom report indicating power headroom values associated with at least two of a plurality of antenna ports of the user equipment, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set; and determine, based on the power headroom report, at least one transmission power for uplink transmission by the user equipment from at least one of the plurality of antenna ports.

[42] The at least two of the plurality of antenna ports may be associated with different uplink reference signal resources of the same uplink reference signal resource set; or the at least two of the plurality of antenna ports may be associated with the same uplink reference signal resources of the same uplink reference signal resource set.

[43] The at least one processor may further cause the apparatus to: send, to the user equipment, configuration information for power headroom reporting, the configuration information being associated with uplink reference signal transmission from the plurality of antenna ports of the user equipment.

[44] The configuration information may comprise at least one of: a first threshold value for determining at least one subset of the plurality of antenna ports; an indication of at least one subset of the plurality of antenna ports; a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

[45] The power headroom report may comprise, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the power headroom associated with the respective at least one subset of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of one or more antenna ports comprised in the subset is less than the first threshold value.

[46] The at least one processor may further cause the apparatus to: receive, from the user equipment, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction; determine, based on the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction, the at least one subset of the plurality of antenna ports; and send, to the user equipment, the configuration information indicating the at least one subset of the plurality of antenna ports.

[47] The at least one processor may further cause the apparatus to: receive, from the user equipment, an indication of the user equipments preferred first threshold value and / or the user equipment’s preferred second threshold value; and determine the first threshold value and / or the user equipment’s preferred second threshold value based on the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

[48] The plurality of antenna ports may be comprised in a single subset, wherein a difference between the determined power headroom associated with the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

[49] The power headroom report may further comprise information indicating at least one of: a size of the power headroom report; a number of power headroom values comprised in the report; a number of antenna ports for which the power headroom is reported; a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

[50] The at least one processor may further cause the apparatus to: send, to the user equipment, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the received power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; and receive, from the user equipment, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

[51] According to an aspect, there is provided a method comprising: obtaining configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the user equipment and with at least one uplink reference signal resource; determining power headroom values for the uplink signal transmission associated with each of the plurality of antenna ports of the user equipment; and sending, to at least one network node, based on the determined power headroom values and the configuration information, a power headroom report indicating the determined power headroom values associated with at least two of the plurality of antenna ports, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set.

[52] Obtaining the configuration information may comprise at least one of: receiving the configuration information from the at least one network node; or obtaining the configuration information based on information hard coded at the user equipment.

[53] The at least two of the plurality of antenna ports may be associated with different uplink reference signal resources of the same uplink reference signal resource set; or the at least two of the plurality of antenna ports may be associated with the same uplink reference signal resources of the same uplink reference signal resource set.

[54] A number of power headroom fields comprised in the power headroom report may be based on the number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

[55] The method may further comprise: sending, to the at least one network node, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

[56] The configuration information may comprise at least one of: a first threshold value for determining at least one subset of the plurality of antenna ports; an indication of at least one subset of the plurality of antenna ports; a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; or a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

[57] The method may further comprise: determining a power headroom value associated with each of the plurality of antenna ports; and determining, based on the second threshold value and the power headroom value associated with the each of the plurality of antenna ports, a number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report, wherein the sending the power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports is based on the determined number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report.

[58] The method may further comprise: determining the at least one subset of the plurality of antenna ports, each subset comprising one or more antenna ports, wherein the power headroom report comprises, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the determined power headroom for the respective at least one subset of the plurality of antenna ports.

[59] Determining the at least one subset of the plurality of antenna ports may comprise one of: determining the at least one subset of the plurality of antenna ports based on the determined power headroom for each of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of the one or more antenna ports comprised in the subset is less than the first threshold value; or determining the at least one subset of the plurality of antenna ports based on the indication of the at least one subset of the plurality of antenna ports.

[60] The method may further comprise: sending, to the at least one network node, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value, wherein the configuration information is received from the at least one network node, and wherein the first threshold value and / or the second threshold value is based on the indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

[61] The plurality of antenna ports may be comprised in a single subset, wherein a difference between the determined power headroom of the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

[62] The power headroom report may further comprise information indicating at least one of: a size of the power headroom report; a number of power headroom values comprised in the report; a number of antenna ports for which the power headroom is reported; a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

[63] The method may further comprise: receiving, from the at least one network node, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the sent power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; and sending, to the at least one network node, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

[64] According to an aspect there is provided a method comprising: receiving, from a user equipment, a power headroom report indicating power headroom values associated with at least two of a plurality of antenna ports of the user equipment, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set; and determining, based on the power headroom report, at least one transmission power for uplink transmission by the user equipment from at least one of the plurality of antenna ports.

[65] The at least two of the plurality of antenna ports may be associated with different uplink reference signal resources of the same uplink reference signal resource set; or the at least two of the plurality of antenna ports may be associated with the same uplink reference signal resources of the same uplink reference signal resource set.

[66] The method may further comprise: sending, to the user equipment, configuration information for power headroom reporting, the configuration information being associated with uplink reference signal transmission from the plurality of antenna ports of the user equipment.

[67] The configuration information may comprise at least one of: a first threshold value for determining at least one subset of the plurality of antenna ports; an indication of at least one subset of the plurality of antenna ports; a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

[68] The power headroom report may comprise, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the power headroom associated with the respective at least one subset of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of one or more antenna ports comprised in the subset is less than the first threshold value.

[69] The method may further comprise: receiving, from the user equipment, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction; determining, based on the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction, the at least one subset of the plurality of antenna ports; and sending, to the user equipment, the configuration information indicating the at least one subset of the plurality of antenna ports.

[70] The method may further comprise: receiving, from the user equipment, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value; and determining the first threshold value and / or the user equipment’s preferred second threshold value based on the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

[71] The plurality of antenna ports may be comprised in a single subset, wherein a difference between the determined power headroom associated with the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

[72] The power headroom report may further comprise information indicating at least one of: a size of the power headroom report; a number of power headroom values comprised in the report; a number of antenna ports for which the power headroom is reported; a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

[73] The method may further comprise: sending, to the user equipment, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the received power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; and receiving, from the user equipment, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

[74] According to an aspect, there is provided a computer readable medium comprising instructions which, when executed by a user equipment, cause the user equipment to perform at least the following: obtaining configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the user equipment and with at least one uplink reference signal resource; determining power headroom values for the uplink signal transmission associated with each of the plurality of antenna ports of the user equipment; and sending, to at least one network node, based on the determined power headroom values and the configuration information, a power headroom report indicating the determined power headroom values associated with at least two of the plurality of antenna ports, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set.

[75] Obtaining the configuration information may comprise at least one of: receiving the configuration information from the at least one network node; or obtaining the configuration information based on information hard coded at the user equipment.

[76] The at least two of the plurality of antenna ports may be associated with different uplink reference signal resources of the same uplink reference signal resource set; or the at least two of the plurality of antenna ports may be associated with the same uplink reference signal resources of the same uplink reference signal resource set.

[77] A number of power headroom fields comprised in the power headroom report may be based on the number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

[78] The instructions, when executed by the user equipment, may cause the user equipment to further perform: sending, to the at least one network node, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

[79] The configuration information may comprise at least one of: a first threshold value for determining at least one subset of the plurality of antenna ports; an indication of at least one subset of the plurality of antenna ports; a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; or a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

[80] The instructions, when executed by the user equipment, may cause the user equipment to further perform: determining a power headroom value associated with each of the plurality of antenna ports; and determining, based on the second threshold value and the power headroom value associated with the each of the plurality of antenna ports, a number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report, wherein the sending the power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports is based on the determined number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report.

[81] The instructions, when executed by the user equipment, may cause the user equipment to further perform: determining the at least one subset of the plurality of antenna ports, each subset comprising one or more antenna ports, wherein the power headroom report comprises, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the determined power headroom for the respective at least one subset of the plurality of antenna ports.

[82] Determining the at least one subset of the plurality of antenna ports may comprise one of: determining the at least one subset of the plurality of antenna ports based on the determined power headroom for each of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of the one or more antenna ports comprised in the subset is less than the first threshold value; or determining the at least one subset of the plurality of antenna ports based on the indication of the at least one subset of the plurality of antenna ports.

[83] The instructions, when executed by the user equipment, may cause the user equipment to further perform: sending, to the at least one network node, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value, wherein the configuration information is received from the at least one network node, and wherein the first threshold value and / or the second threshold value is based on the indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

[84] The plurality of antenna ports may be comprised in a single subset, wherein a difference between the determined power headroom of the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

[85] The power headroom report may further comprise information indicating at least one of: a size of the power headroom report; a number of power headroom values comprised in the report; a number of antenna ports for which the power headroom is reported; a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

[86] The instructions, when executed by the user equipment, may cause the user equipment to further perform: receiving, from the at least one network node, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the sent power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; and sending, to the at least one network node, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

[87] According to an aspect, there is provided a computer readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: receiving, from a user equipment, a power headroom report indicating power headroom values associated with at least two of a plurality of antenna ports of the user equipment, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set; and determining, based on the power headroom report, at least one transmission power for uplink transmission by the user equipment from at least one of the plurality of antenna ports.

[88] The at least two of the plurality of antenna ports may be associated with different uplink reference signal resources of the same uplink reference signal resource set; or the at least two of the plurality of antenna ports may be associated with the same uplink reference signal resources of the same uplink reference signal resource set.

[89] The instructions, when executed by the apparatus, may cause the apparatus to further perform: sending, to the user equipment, configuration information for power headroom reporting, the configuration information being associated with uplink reference signal transmission from the plurality of antenna ports of the user equipment.

[90] The configuration information may comprise at least one of: a first threshold value for determining at least one subset of the plurality of antenna ports; an indication of at least one subset of the plurality of antenna ports; a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

[91] The power headroom report may comprise, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the power headroom associated with the respective at least one subset of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of one or more antenna ports comprised in the subset is less than the first threshold value.

[92] The instructions, when executed by the apparatus, may cause the apparatus to further perform: receiving, from the user equipment, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction; determining, based on the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction, the at least one subset of the plurality of antenna ports; and sending, to the user equipment, the configuration information indicating the at least one subset of the plurality of antenna ports.

[93] The instructions, when executed by the apparatus, may cause the apparatus to further perform: receiving, from the user equipment, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value; and determining the first threshold value and / or the user equipment’s preferred second threshold value based on the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

[94] The plurality of antenna ports may be comprised in a single subset, wherein a difference between the determined power headroom associated with the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

[95] The power headroom report may further comprise information indicating at least one of: a size of the power headroom report; a number of power headroom values comprised in the report; a number of antenna ports for which the power headroom is reported; a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

[96] The instructions, when executed by the apparatus, may cause the apparatus to further perform: sending, to the user equipment, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the received power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; and receiving, from the user equipment, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

[97] According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions that, when executed by an apparatus, cause the apparatus to perform at least the method according to any of the preceding aspects.

[98] In the above, many different aspects have been described. As previously noted, it should be appreciated that further aspects may be provided by the combination of any two or more of the aspects described above. Other features, aspects, and elements will become apparent in view of the following. DESCRIPTION OF FIGURES

[99] Some example embodiments will now be described, by way of non-limiting and illustrative example only, with reference to the accompanying Figures (FIGs.) in which:

[100] FIG. 1 shows a representation of a 5th generation communication system;

[101] FIG. 2 shows a representation of an apparatus for the communication system of FIG. 1 according to some example embodiments;

[102] FIG. 3 shows a representation of an apparatus according to some example embodiments;

[103] FIG. 4 shows a method according to some examples;

[104] FIG. 5 shows a method according to some examples;

[105] FIGs. 6a-d illustrate example power headroom reports at different time instants;

[106] FIG. 7 shows a signalling exchange according to some examples; and

[107] FIG. 8 shows a schematic representation of an apparatus according to some examples. DETAILED DESCRIPTION

[108] In the following various example embodiments are explained with reference to communication devices capable of communication with a communication system. Before explaining in detail the various example embodiments of this disclosure, a 5th generation communication system (5GS), an access network and a core network (5GC) thereof, and communication devices are briefly explained with reference to FIG. 1, 2 and 3.

[109] FIG. 1 shows a schematic representation of a 5G communication system (5GS). The 5GS may comprise a user equipment (UE) or Terminal 100, an access network, such as a 5G radio access network (5G-RAN) 101 or next generation radio access network (NG-RAN), a 5G core network 102, and one or more application functions 103. An application function 103 may be deployed in the 5GS as trusted application function or may be deployed or host on one or more application servers of the data network (DN) 104. Such application functions are untrusted application functions. The 5GS connects the UE to a data network the access network and the 5GC 102 (e.g., a UPF of the 5GC).

[110] The 5G-RAN 101 may comprise one or more radio access nodes, such as a gNodeB (gNB). A gNB may include one or more gNodeB (gNB) distributed units (DUs) connected to one or more gNodeB (gNB) centralized units (CUs).

[111] The 5GC may comprise the following network functions: Network Slice Selection Function (NSSF); Network Exposure Function (NEF) 105; Network Repository Function (NRF); Policy Control Function (PCF); Unified Data Management (UDM) 106; Application Function (AF) 103; Authentication Server Function (AUSF) 107; an Access and Mobility Management Function (AMF) 108; Session Management Function (SMF) 109; and a user plane function (UPF) 110. FIG. 1 also shows the various interfaces (N1, N2 etc.) that may be implemented between the various elements of the system. It should be understood that not all of the above network functions are shown in FIG. 1, and that in some examples the 5GC may comprise additional network functions other than those mentioned above.

[112] FIG. 2 illustrates an example of a control apparatus 200 for controlling a function of the access network (e.g., a 5G-RAN or the NG-RAN illustrated in FIG. 1) of FIG. 1. The control apparatus 200 may comprise at least one random access memory (RAM) 211a, at least on read only memory (ROM) 211b, at least one processor 212, 213 and a network interface 214. The at least one processor 212, 213 may be coupled to the RAM 211a and the ROM 211b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215. Execution of the software code 215 may, for example, may cause the apparatus to perform operations for controlling a function of the access network. The software code 215 may be stored in the ROM 211b. The control apparatus 200 may be interconnected with another control apparatus 200 for controlling another function of the 5G-RAN or the NG-RAN. In some embodiments, each function of the 5G-RAN or the NG-RAN is deployed or hosted on a control apparatus 200. In alternative embodiments, two or more functions of the 5G-RAN or the NG-RAN may share a control apparatus.

[113] FIG. 3 illustrates an example of a communication device 300, such as the UE of FIG. 1. The communication device 300 may be provided by any device capable of sending and receiving radio signals. Non-limiting examples of a communication device 300 comprise a user equipment, a mobile station (MS) or mobile device, such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), a personal data assistant (PDA) or a tablet provided with wireless communication capabilities, a machine-type communications (MTC) device, an Internet of things (loT) type communication device or any combinations of these or the like. The communication device 300 may comprise a transceiver for transmitting and / or receiving, for example, wireless signals carrying communications, for example radio signals. The communications may be one or more of voice, electronic mail (email), text messages, multimedia data, machine data and so on.

[114] The communication device 300 may receive wireless signals (e.g., radio signals) over an air or radio interface 307 via appropriate apparatus for receiving and may transmit wireless signals via appropriate apparatus for transmitting radio signals. In FIG. 3 transceiver is designated schematically by block 306. The transceiver 306 may comprise, for example, a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device and may comprise one or more antenna elements. The antenna arrangement may be a multi-input multi output (MIMO) antenna.

[115] The communication device 300 may be provided with at least one processor 301, at least one memory ROM 302a, at least one RAM 302b and other possible components 303 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access networks (e.g., the 5G-RAN or NG-RAN illustrated in FIG. 1) and other communication devices. The at least one processor 301 is coupled to the RAM 302b and the ROM 302a. The at least one processor 301 may be configured to execute an appropriate software code 308. The software code 308 may, for example, allow to perform one or more operations of the communication device. The software code 308 may be stored in the ROM 302a.

[116] The processor, the ROM, and the RAM, the transceiver and other circuitry of the communication device (e.g., a modem) can be provided on a circuit board, in chipsets, or in a system on chip. The circuit board, chipsets or system on chip is denoted by reference 304. The communication device 300 may optionally have a user interface, such as keypad 305, a touch sensitive screen or a pad, combinations thereof or the like. Optionally one or more of a display, a speaker and a microphone may be provided depending on the type of communication device.

[117] Some examples of the present disclosure may relate to power headroom (PH) reporting. PH may refer to a difference between a maximum transmission power of a UE (i.e., a maximum UL transmission power) and a transmission power that the UE is using (i.e., a currently used UL transmission power). In some examples the PH may be associated with a particular UL signal, for example an UL reference signal (RS), such as a Sounding Reference Signal (SRS). That is to say, the PH may indicate a difference between a maximum transmission power for the UL signal and a currently used transmission power for the UL signal.

[118] The UE may report the PH by sending, to a transmission-reception point (TRP) of the network (e.g., a TRP of an access node, such as a gNB), a PH report (PHR). The network may then adapt the transmission power of the UE based on the PHR. For example, the network may determine and allocate a transmission power level to the UE based on the PHR.

[119] The PHR may comprise a PH field which indicates the PH level / value of the UE. The length of the PH field may be 6 bits. The reported PH and the corresponding PH levels / values may be measured values in dB, for example as specified in 3GPP TS 38.133.

[120] The PHR may also comprise a field indicating a maximum power capacity of the UE, which may be denoted PCMAX,f,c herein. PCMAX,f,c may for example be as specified in 3GPP TS 38.213, and may be used for calculation of the preceding PH field. The reported PCMAX,f,c and the corresponding nominal UE transmit power levels may be measured values in dBm, for example as specified in 3GPP TS 38.133.

[121] In the case of these being multiple TRPs for a same cell, the PHR may be extended to enable PH reporting of two TRPs of the same cell in the same PHR. In some examples, the PHR may comprise a first PH field and a second PH field. The first PH field may indicate the PH level / value associated with a first UL RS resource set. The second PH field may indicate the PH level / value associated with a second UL RS resource set. The length of the PH fields and the measured values may be as described previously. The PHR may also comprise PCMAX,f,c as described previously.

[122] According to some existing PH reporting mechanisms, a UE may therefore report a single PH value (associated with a single UL RS resource set for UL RS transmission to a single TRP), or two PH values (associated with two different UL RS resource sets for UL RS transmission to two different TRPs). The number of PH fields in the PHR is limited to one field per UL RS resource set.

[123] However, if the UE has multiple antenna ports, the UE may have a different PH associated with different antenna ports, even for the same UL RS resource set. For example, different antenna ports may have different directive radiation patterns and power amplification capabilities, and therefore may be associated with a different PH. Furthermore, the conditions experienced by the different antenna ports may vary dynamically and may not be the same, and the number of antenna ports used by the UE may also vary dynamically. Some existing PH reporting mechanisms may not be capable of defining the PH dynamically and with sufficient granularity to enable the network to send appropriate transmission power control commands to the UE to optimize UE performance.

[124] Some examples of the present disclosure may address one or more of these issues. Some examples may provide mechanisms for improved PH reporting. Some examples may provide dynamic PH reporting, and may enable reporting of multiple PH values for a same UL RS resource set.

[125] Reference is made to FIG. 4, which shows methods according to some examples. The method of FIG. 4 may be performed by a UE.

[126] At 400, the method may comprise obtaining configuration information for PH reporting, the configuration information being associated with UL transmission from a plurality of antenna ports of the UE and at least one UL RS resource. The configuration information may indicate to the UE to perform PH reporting with a dynamic number of PH fields comprised in the PHR. The configuration information may be associated with a particular UL RS resource set (e.g., a particular srs-ResourceSetID or SRS-ResourcelD).

[127] At 402, the method may comprise determining power headroom values for UL signal transmission associated with each of the plurality of antenna ports of the UE. The PH values may be as described previously. In some examples the determined power headroom values may be associated with individual antenna ports and / or a combination of the antenna ports.

[128] At 404, the method may comprise sending, to at least one network node, based on the determined PH values and the configuration information, a PHR indicating the determined PH values associated with at least two of the plurality of antenna ports, wherein at least two of the plurality of antenna ports are associated with a same UL RS resource set. The PHR may comprise one or more PH fields. Each PH field may indicate the determined PH value for one or more antenna ports.

[129] Reference is made to FIG. 5, which shows a method according to some examples. The method of FIG. 5 may be performed by a network node(e.g., an access node such as a gNB or other apparatus comprising a TRP).

[130] At 500, the method comprises receiving, from a user equipment, a PHR indicating PH values associated with at least two of a plurality of antenna ports of the user equipment, wherein at least two of the plurality of antenna ports are associated with a same UL RS resource set. The PHR and PH values may be as described previously.

[131] At 502, the method comprises determining, based on the PHR, at least one transmission power for UL transmission by the user equipment from at least one of the plurality of antenna ports.

[132] As mentioned, in some examples the UE may obtain configuration information for PH reporting. In some examples the configuration information may comprise one or more of: (a) a first threshold value for determining at least one subset of the plurality of antenna ports; (b) an indication of at least one subset of the plurality of antenna ports; (c) a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; (d) a number of PH fields to be included in the PHR.

[133] In some examples the UE may obtain the configuration information by receiving the configuration information from a network node. In some examples the configuration information may be determined by the network (e.g., network node, TRP, access node, or other network entity) and be received at the UE via a medium access control (MAC) control element (CE) or other suitable message. Additionally or alternatively, the UE may obtain the configuration information based on information hard coded at the user equipment. It should be understood that various different combinations are possible for obtaining the configuration information - for instance, the UE may receive the first threshold value from the network node, and may obtain the second threshold value from hard coded information.

[134] In some examples the network node may determine the configuration information and send the configuration information to the UE. In some examples the network node may determine the configuration information based on at least one of: (a) a number of TRPs associated with UL RS resource sets allocated to the UE; (b) the coresetpoolindex associated with the UL RS resource set(s) allocated to the UE; (c) the UL RS resource set identifier(s) allocated to the UE.

[135] In some examples the UE may send, to the network node, an indication of the UE’s preferred first threshold value and / or the UE’s preferred second threshold value. The network node may determine the first threshold value and / or the second threshold value to be used based on the UE’s preferred first threshold value and / or the UE’s preferred second threshold value. The network node may then send the configuration information comprising the first threshold value and / or second threshold value to the UE based on the determined value(s).

[136] In some examples, at least two of the plurality of antenna ports may be associated with different UL RS resources of the same UL RS resource set. For example, the UE may comprise a first antenna port associated with first UL RS resources associated with UL RS resource set #1, and a second antenna port associated with second UL RS resources associated with UL RS resource set #1. In other words, the UE may be configured to transmit the UL RS via the first antenna port using the first UL RS resources, and transmit the UL RS via the second antenna port using the second UL RS resources. In some examples the plurality of antenna ports may comprise SRS antenna ports.

[137] In other examples, at least two of the plurality of antenna ports may be associated with the same UL RS of the same UL RS resource set. For example, the UE may comprise a first antenna port associated with first UL RS resources associated with UL RS resource set #1, and a second antenna port associated with the first UL RS resources associated with UL RS resource set #1. In other words, the UE may be configured to transmit the UL RS via the first antenna port using the first UL RS resources, and transmit the UL RS via the second antenna port using the first UL RS resources.

[138] In some examples the UE may group PH values associated with one or more antenna ports into the same PH field when sending the PHR. For example, the UE may determine at least one subset of the plurality of antenna ports, where each subset comprises one or more antenna ports. The PH value included in the PH field may indicate the PH associated with the subset.

[139] In some examples, the PH values associated with the antenna ports comprised in the subset may be “similar” values. That is to say, a difference between the determined PH associated with the antenna ports comprised in the subset may be less than a threshold value. The threshold value may be the first threshold value comprised in the configuration information. The UE may therefore determine at least one subset of the plurality of antenna ports based on the determined PH associated with each of the plurality of antenna ports and the first threshold value.

[140] In some examples the plurality of antenna ports may be comprised in a single subset. That is to say, a difference between the determined PH associated with all of the plurality of antenna ports may be less than the first threshold value. The UE may therefore send a PHR comprising a single PH value associated with the plurality of antenna ports. The single PH value may therefore indicate the determined PH values associated with all of the plurality of antenna ports.

[141] In other examples, the plurality of antenna ports may be comprised in multiple subsets. For example, the UE may comprise four antenna ports. The PHR may comprise two PH fields - a first field indicating the PH value associated with antenna ports 1 and 3, and a second field indicating the PH value associated with antenna ports 2 and 4. It should be understood that this example is provided for illustrative purposes only, and that in other examples different numbers of antenna ports and subset groupings are possible.

[142] In some examples a number of PH fields comprised in the PHR may be based on a number of simultaneously transmitting antenna ports of the UE in the UL direction. For example, if the UE is simultaneously transmitting UL RS using four antenna ports, the number of PH fields comprised in the report may be four. However, as explained above, in some examples the UE may combine the PH for multiple antenna ports associated with similar PH values into a single PH field, and thus in some examples the number of PH fields comprised in the PHR may not be the same as the number of simultaneously transmitting antenna ports of the UE in the UL direction.

[143] In some examples the UE may send, to the network node, an indication of the maximum possible number of simultaneously transmitting antenna ports of the UE in the UL direction. The network node may determine the configuration information based at least in part on this indication. For example, when the UE has a relatively large maximum possible number of simultaneously transmitting antenna ports, the network node may set a relatively large first threshold value, such that the PH values associated with more antenna ports are grouped together in order to avoid the PHR being excessively large.

[144] In some examples the PHR may be reported for different types of UL transmission, such as but not limited to physical uplink shared channel (PUSCH), physical uplink control channel (PLICCH) or RS (e.g., SRS). For example, as defined in 3GPP TS 38.321, the Power Headroom reporting procedure may be used to provide the serving gNB with the following information: (a) - Type 1 power headroom: the difference between the nominal UE maximum transmit power and the estimated power for UL-SCH transmission per activated Serving Cell; (b) - Type 2 power headroom: the difference between the nominal UE maximum transmit power and the estimated power for UL-SCH and PUCCH transmission on SpCell of the other MAC entity (i.e. E-UTRA MAC entity in EN-DC, NE-DC, and NGEN-DC cases); (c) - Type 3 power headroom: the difference between the nominal UE maximum transmit power and the estimated power for SRS transmission per activated Serving Cell ”

[145] In some examples the PHR may comprise additional information to the PH fields. The additional information may in some examples be comprised in a bitmap included in the same message used to send the PHR, or may be sent separately. In some examples the additional information may comprise PCMAX,f,c as described previously. In some examples the additional information may comprise information indicating at least one of: (a) A size of the PHR; (b) A number of PH values comprised in the PHR; (c) A number of antenna ports for which the PHR is reported; or (d) A number of subsets of antenna ports for which the PHR is reported and an indication of the antenna ports comprised within each subset.

[146] In some examples, when the UE reports PHR comprising multiple PH values for the same UL RS resource, the UE may implicitly indicate that it is capable of transmitting UL signal(s) on the same UL beam via different antenna ports. The network may select which antenna port(s) the UE is to transmit the UL signal(s)via based on the available headroom and adapt the UE scheduling accordingly - for example the network may schedule or re-schedule UL transmission via the antenna port(s) with the largest available PH. This may help increase UE throughput and make more efficient use of network resources.

[147] For example, the network node may determine, based on the PHR, at least one transmission power for UL transmission by the UE from at least one antenna port. The network node may send, to the UE, information indicating the at least one transmission power for the uplink transmission by the UE from the at least one of the plurality of antenna ports. The information indicating the at least one transmission power for the uplink transmission by the UE from the at least one of the plurality of antenna ports may be sent to the UE in a transmission power control (TPC) command. The UE may then send, to the at least one TRP based on the information indicating the at least one transmission power, the UL transmission from the at least one of the plurality of antenna ports.

[148] As explained previously, in some examples (e.g., according to in 3GPP TS 38.133), the UE may report a single PH value (associated with a single UL RS resource set for UL RS transmission to a single TRP), or two PH values (associated with two different UL RS resource sets for UL RS transmission to two different TRPs), where the number of PH fields in the PHR is limited to one field per UL RS resource set.. In some examples the UE may determine a PH value associated with an antenna port or a subset / group of antenna ports of the user equipment; and determine, based on the second threshold value and the PH value associated with each antenna port or sub / group of antenna ports of the user equipment, a number of power headroom values associated with a number of antenna ports and / or subsets of antenna ports and an UL RS resource and / or resource set, to be included in the power headroom report. The UE may send the PHR indicating the determined power headroom values associated with the at least two of the plurality of antenna ports for the same UL RS resource of resource set based on the determined number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report. For example, when the PH value associated with one of the antenna ports is above the second threshold value, the UE may determine to include two or more PH values associated with the same UL RS resource set in the PHR, and when the PH value associated with one of the antenna ports is below the second threshold value, the UE may determine to send a PHR with only one PH value associated with an UL RS resource set (e.g., as per 3GPP TS 38.133).

[149] Two examples are provided below to help explain many of the concepts described above. It should be understood that these examples are for illustrative purposes only, and that different examples are possible within the scope of the present disclosure.

[150] Example 1: single UL RS resource set

[151] In this illustrative example, the UE is configured for UL RS transmission with UL RS resource set #1. The UE may utilise up to 4 antenna ports simultaneously for UL transmission. The UE is configured with a maximum PH difference threshold of 3 dB (i.e., the first threshold value is 3 dB).

[152] The UE utilizes antenna ports 1-4 for UL transmission using UL RS resource set #1. The UE calculates PH values for each of the ports as follows: (a) PH for transmission to UL RS resource set #1 via antenna port 1 - PH1p1 (b) PH for transmission to UL RS resource set #1 via antenna port 2 - PH1p2 (c) PH for transmission to UL RS resource set #1 via antenna port 3 - PH1p3 (d) PH for transmission to UL RS resource set #1 via antenna port 4 - PH1p4

[153] The UE determines the differences in PH values and compares those values to the first threshold as follows: (a) abs(PH1p1 - PH1p3) <3 dB; (b) abs(PH1p2 - PH1p4) <3 dB; (c) abs(PH1p1 - PH1p2) >3 dB.

[154] The UE determines two subsets of antenna ports - a first subset comprising antenna ports 1 and 3, and a second subset comprising antenna ports 2 and 4. The UE sends a PHR to the network node comprising a first PH field indicating the PH values associated with the first subset (i.e. for antenna ports 1 and 3) and a second PH field indicating the PH values associated with the second subset (i.e. for antenna ports 2 and 4). The PHR thus comprises two PH values associated with UL RS resource set #1.

[155] Example 2: two UL RS resource sets

[156] In this illustrative example, the UE is configured for UL RS transmission with UL RS resource set #1 and UL RS resource set #2. The UE may utilise up to 4 antenna ports simultaneously for UL transmission. The UE is configured with a maximum PH difference threshold of 3 dB (i.e., the first threshold value is 3 dB).

[157] The UE utilizes antenna ports 1 and 2 for UL transmission using UL RS resource set #1, and antenna ports 3 and 4 for UL transmission using UL RS resource set #2. The UE calculates PH values for each of the ports as follows: (a) PH for transmission to UL RS resource set #1 via antenna port 1 - PH1p1 (b) PH for transmission to UL RS resource set #1 via antenna port 2 - PH1p2 (c) PH for transmission to UL RS resource set #2 via antenna port 3 - PH1p3 (d) PH for transmission to UL RS resource set #2 via antenna port 4 - PH1p4

[158] The UE determines the differences in PH values and compares those values to the first threshold as follows: (a) abs(PH1p1 - PH1p2) <3 dB; (b) abs(PH1p3 - PH1p4) <3dB.

[159] The UE determines two subsets of antenna ports - a first subset comprising antenna ports 1 and 2, and a second subset comprising antenna ports 3 and 4. The UE sends a PHR to the network node comprising a first PH field indicating the PH values associated with the first subset for UL RS resource set #1 (i.e. for antenna ports 1 and 2) and a second PH field indicating the PH values associated with the second subset for UL RS resource set #2 (i.e. for antenna ports 3 and 4). The PHR thus comprises a first PH value associated with UL RS resource set #1 (indicating PH values for antenna ports 1 and 2), and a second PH value associated with UL RS resource set #2 (indicating PH values for antenna ports 3 and 4).

[160] Some examples may be applied to multiple-input multiple-output (MIMO) use cases. For example, one UL RS resource set may be associated to one TRP, and so when multiple PH values are reported on the same UL RS resource set, those multiple PH values are associated with the same TRP (but associated with different MIMO layers). Example 1 above illustrates an example of MIMO on a single TRP with multiple PH value reporting, where one PH value per antenna port is reported, which may help balance the layers and increase UL user throughput. Example 2 above illustrates a case of multiple TRP, where multiple PH values are reported on each of the TRPs.

[161] In some examples the PHR generated by the UE may dynamically change over time, for example based on channel characteristics, changes in configuration information received from the network node, UE-side decisions relating to antenna port activation etc.

[162] Reference is made to FIGs. 6a-d which illustrate some example PHRs at different time instants t1, t2, t3 and t4.

[163] With reference to FIG. 6a, at time instant t1 the PHR comprises two PH fields. Field PH1 represents PH1p1 and PH1p2 and is associated with UL RS resource set#1. Field PH2 represents PH2p3 and PH2p4 and is associated with UL RS resource set #2. The PHR illustrated in FIG. 6a may therefore represent example 2 described above. The association between the PH fields and the different UL RS resource sets is represented by the different patterns in FIG. 6a (and similarly in FIGs. 6b-d).

[164] With reference to FIG. 6b, after some time, at time instant t2 the channel conditions change such that the difference between PH2p3 and PH2p4 is no longer within the first threshold (e.g., abs(PH2p3 - PH2p4) >3 dB), but the difference between PH1p1 and PH1p2 remains within the first threshold. Accordingly the PHR at time instant t2 comprises three PH fields. Field PH1 represents PH1p1 and PH1p2 and is associated with UL RS resource set #1. Field PH2 represents PH2p3 and is associated with UL RS resource set #2. Field PH3 represents PH2p4 and is associated with UL RS resource set #2.

[165] With reference to FIG. 6c, after some further time, at time instant t3 the channel conditions change such that the difference between PH1p1 and PH1p2 is no longer within the first threshold (e.g., abs(PH1p1 - PH1p2) >3 dB), and the difference between PH2p3 and PH2p4 remains greater than the first threshold (e.g., abs(PH2p3 - PH2p4) >3 dB). Accordingly the PHR at time instant t3 comprises four PH fields. Field PH1 represents PH1p1 and is associated with UL RS resource set#1. Field PH2 represents PH1p2 and is associated with UL RS resource set #1. Field PH3 represents PH2p3 and is associated with UL RS resource set #2. Field PH4 represents PH2p4 and is associated with UL RS resource set #2.

[166] With reference to FIG. 6d, after yet more time, at time instant t4 the UE determines (either autonomously or based on signalling from the TRP), to re-allocate antenna port 2 to UL RS transmissions for UL RS resource set #2. The difference between PH2p2 and PH2p3 is greater than the first threshold, the difference between PH2p2 and PH2p4 is greater than the first threshold, and the difference between PH2p3 and PH2p4 is greater than the first threshold. Accordingly the PHR at time instant t4 comprises four PH fields. Field PH1 represents PH1p1 and is associated with UL RS resource set#1. Field PH2 represents PH2p2 and is associated with UL RS resource set #2. Field PH3 represents PH2p3 and is associated with UL RS resource set #2. Field PH4 represents PH2p4 and is associated with UL RS resource set #2.

[167] Some examples may be applied to multiple-input multiple-output (MIMO) and beamforming user cases requiring the same UL RS resource set for each PH value - each PH value reflecting the different transmitter configurations.

[168] There may be multiple sources of power imbalance between antenna branches or antenna ports, and / or between transmission layers, be it at the transmission or reception side. Such sources may be, for example, Tx antenna gain imbalance (e.g., by design, UE may have different quality antennas for different chains), pathloss, shadowing, hand gripping, UE Tx power calibration errors; in addition, at least for SRS switching, insertion losses and trace losses could also be sources of power imbalance. At least some those sources of power imbalance could lead to large power, and thus SINR, imbalance between (MIMO) transmission layers. By applying the concepts described herein, some examples may report the PH for different antenna branches / antenna ports / transmission layers (e.g., MIMO layers) associated with the same UL RS resource set, which may allow the network node to account for the power imbalance at the UE antenna ports / branches / transmission layers dynamically. It should be understood that while some examples described herein have made reference to antenna ports, the same concepts may be applied to antenna branches and / or transmission layers.

[169] Reference is made to FIG. 7, which shows a signalling exchange according to some examples.

[170] At 700, the UE sends, to the network node, information indicating the UE’s capability for PH reporting. For example, the UE may indicate, to the network node, the UE’s capability in terms of at least one of: (a) A number of supported PH fields in the PHR (e.g., 1, 2, 4); (b) A maximum number of PH fields (e.g., 4); (c) PH thresholds supported by the UE (i.e., different values of the first threshold supported by the UE, e.g., 1, 3, 6 dB); (d) A number of UL antenna ports.

[171] Optionally, at 702 the UE may send, to the network node, information indicating the UE’s preferred threshold values as described previously. The UE’s preferred threshold difference values may be included in the information sent at 700, or may be sent separately as shown in FIG. 7.

[172] At 704, the network node sends, to the UE, configuration information enabling PH reporting with a dynamic number of PH fields. The configuration information may be as described previously. For example, the configuration information may comprise information for grouping PH values for subsets of ports, the difference threshold value(s), etc. The network node may determine the configuration information (e.g., values of the first and second threshold) based on parameters, such as but not limited to, channel conditions, load information, rank / modulation coding scheme information, etc. Optionally, the network node may determine the configuration information based on the UE’s preferred threshold difference values, if received at 702. In some examples the UE may obtain configuration information indicating multiple values of PH fields per UL RS resource set (e.g., by receiving an RRC message including the configuration information), and the network node may send an indication to the UE as to which of the multiple values to use (e.g., by sending a MAC message including the indication).

[173] At 706, the network node sends DL RS to the UE. In some examples the UE may receive DL RS from multiple TRPs of the network node - for example TRP1 may send DL RS #1 to the UE and TRP2 may send DL RS #2 to the UE.

[174] At 708, the UE determines the PH value associated with each antenna port of the UE for UL transmission for each UL RS resource set. The UE may determine, based on the determined PH values, one or more subsets of antenna ports as described previously.

[175] For example, the UE may determine PH1p1, PH1p2, PH2p3, and PH2p4, and determine to group antenna ports 1 and 2 (based on the difference between PH1p1 and PH 1 p2) into a first subset, and antenna ports 3 and 4 (based on the difference between PH2p3 and PH2p4) into a second subset, as described previously.

[176] At 710, the UE sends a PHR to the network node. The PHR may be as described previously. Following the example in step 708, the UE may send a PHR comprising a first PH field indicating a PH associated with antenna port 1 (which is associated with UL RS resource set#1) and a second PH field indicating a PH associated with antenna port 2 (which is also associated with UL RS resource set #1)). That is to say, the PHR sent by the UE indicates two PH’s associated with the same UL RS resource set (e.g., the value of the first PH field associated with UL RS resource set#1; and the value of the second PH field is also associated with UL RS resource set#1).

[177] At 712 the network node determines, based on the PHR received at 710, at least one transmission power for UL transmission by the UE from at least one of the plurality of antenna ports. In some examples the network node may determine other UL transmission related parameters, such as physical resource block allocation, based on the PHR.

[178] At 714, the network node sends, to the UE, a message indicating the at least one transmission power determined at 712. For example, the network node may send a transmission power control command to the UE indicating the at least one transmission power.

[179] At 716, the UE performs UL transmission based on the message received at 714. For example, the UE may send an uplink transmission to the network node from at least one of the plurality of antenna ports according to the indicated transmission power.

[180] Examples have been described whereby a UE may be enabled for dynamic PH reporting, where the PHR indicates PH values associated with at least two of a plurality of antenna ports, where the at least two of the plurality of antenna ports are associated with a same UL RS resource set. The described examples may improve PH reporting by providing dynamic PH reporting, and may enable reporting of multiple PH values for a same UL RS resource set. This may enable the network to better allocate UL resources to different antenna ports of the UE to optimize throughput.

[181] In some examples there is provided a user equipment comprising means for: obtaining configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the user equipment and with at least one uplink reference signal resource; determining power headroom values for the uplink signal transmission associated with each of the plurality of antenna ports of the user equipment; and sending, to at least one network node, based on the determined power headroom values and the configuration information, a power headroom report indicating the determined power headroom values associated with at least two of the plurality of antenna ports, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set.

[182] In some examples there is provided an apparatus comprising means for: receiving, from a user equipment, a power headroom report indicating power headroom values associated with at least two of a plurality of antenna ports of the user equipment, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set; and determining, based on the power headroom report, at least one transmission power for uplink transmission by the user equipment from at least one of the plurality of antenna ports.

[183] In some examples there is provided a user equipment comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to: obtain configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the user equipment and with at least one uplink reference signal resource; determine power headroom values for the uplink signal transmission associated with each of the plurality of antenna ports of the user equipment; and send, to at least one network node, based on the determined power headroom values and the configuration information, a power headroom report indicating the determined power headroom values associated with at least two of the plurality of antenna ports, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set.

[184] In some examples there is provided an apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, a power headroom report indicating power headroom values associated with at least two of a plurality of antenna ports of the user equipment, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set; and determine, based on the power headroom report, at least one transmission power for uplink transmission by the user equipment from at least one of the plurality of antenna ports.

[185] FIG. 8 shows a schematic representation of non-volatile memory media 800a (e.g., computer disc (CD) or digital versatile disc (DVD)) and 800b (e.g. universal serial bus (USB) memory stick) storing instructions and / or parameters 802 which when executed by a processor allow the processor to perform one or more of the steps of the method of FIG. 4 or 5.

[186] It is understood that references in the above to various network functions (e.g., to an AMF, an SMF, etc.) may be implemented by apparatus that perform at least some of the functionality associated with those network functions. Further, an apparatus configured to implement a network function may further be configured to implement a virtual network function instance of that network function.

[187] It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and / or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

[188] It is noted that whilst some example embodiments have been described in relation to 5G networks, similar example embodiments can be applied in relation to other networks and communication systems. Therefore, although certain example embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, further example embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

[189] It is also noted herein that there are several variations and modifications which may be made to the various example embodiments described herein without departing from the scope of this disclosure.

[190] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements. As used herein, the expression “and / or” includes any and all combinations of the listed terms, including at least any one of the elements, at least any two or more of the elements, or at least all of the elements.

[191] As used herein, the term “or” refers to a non-exclusive “or” unless otherwise indicated (e.g., use of “or else” or “or in the alternative”).

[192] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included. Analogously, performing a step or functionality “based on A” does not indicate that the step or functionality is performed solely based on “A” as one or more additional conditions may be included.

[193] In general, the various embodiments may be implemented in hardware or special purpose circuitry, software, logic or any combination thereof. Some aspects of the disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting and illustrative examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[194] As used herein, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that utilizes software (e.g., firmware) for operation, but the software may not be present when it is not utilized for operation.”

[195] This definition of circuitry applies to all uses of this term herein, including in any claims. As a further example, as used herein, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[196] The embodiments of this disclosure may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and / or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computerexecutable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

[197] Further in this regard it should be noted that any blocks of the logic flow as in the FIGs. may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media, such as hard disk or floppy disks, and optical media, such as DVD and the data variants thereof, CD. The physical media is a non-transitory media.

[198] The term “non-transitory,” as used herein, is a limitation of the medium itself (e.g., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[199] The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

[200] Various example embodiments of the disclosure may be practiced in various components, such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

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

[202] The foregoing description has provided, by way of non-limiting and illustrative examples, a full and informative description of the various example embodiments of this disclosure. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of this disclosure, when read in conjunction with the drawings and the claims. However, all such and similar modifications of the teachings will still fall within the various example embodiments of this disclosure. By way of non-limiting and illustrative example, there is a further example embodiment comprising a combination of one or more example embodiments with any of the other example embodiments previously discussed.

Claims

1. A user equipment comprising means for:obtaining configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the user equipment and with at least one uplink reference signal resource;determining power headroom values for the uplink signal transmission associated with each of the plurality of antenna ports of the user equipment; andsending, to at least one network node, based on the determined power headroom values and the configuration information, a power headroom report indicating the determined power headroom values associated with at least two of the plurality of antenna ports,wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set.

2. The user equipment of claim 1, wherein obtaining the configuration information comprises at least one of:receiving the configuration information from the at least one network node; orobtaining the configuration information based on information hard coded at the user equipment.

3. The user equipment of claim 1 or 2, wherein:the at least two of the plurality of antenna ports are associated with different uplink reference signal resources of the same uplink reference signal resource set; orthe at least two of the plurality of antenna ports are associated with the same uplink reference signal resources of the same uplink reference signal resource set.

4. The user equipment of any preceding claim, wherein a number of power headroom fields comprised in the power headroom report is based on the number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

5. The user equipment of any preceding claim, wherein the means is further for:sending, to the at least one network node, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction.

6. The user equipment of any preceding claim, wherein the configuration information comprises at least one of:a first threshold value for determining at least one subset of the plurality of antenna ports;an indication of at least one subset of the plurality of antenna ports;a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report; ora number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

7. The user equipment of claim 6, wherein the means is further for:determining a power headroom value associated with each of the plurality of antenna ports; anddetermining, based on the second threshold value and the power headroom value associated with the each of the plurality of antenna ports, a number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report,wherein the sending the power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports is based on the determined number of power headroom values and / or antenna ports and / or subsets of antenna ports to be included in the power headroom report.

8. The user equipment claim 6 or 7, wherein the means is further for:determining the at least one subset of the plurality of antenna ports, each subset comprising one or more antenna ports,wherein the power headroom report comprises, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the determined power headroom for the respective at least one subset of the plurality of antenna ports.

9. The user equipment of claim 8, wherein determining the at least one subset of the plurality of antenna ports comprises one of:determining the at least one subset of the plurality of antenna ports based on the determined power headroom for each of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of the one or more antenna ports comprised in the subset is less than the first threshold value; ordetermining the at least one subset of the plurality of antenna ports based on the indication of the at least one subset of the plurality of antenna ports.

10. The user equipment of claim 9, wherein the means is further for:sending, to the at least one network node, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value, wherein the configuration information is received from the at least one network node, and wherein the first threshold value and / or the second threshold value is based on the indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

11. The user equipment of claim 9 or 10, wherein the plurality of antenna ports are comprised in a single subset, wherein a difference between the determined power headroom of the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

12. The user equipment of any preceding claim, wherein the power headroom report further comprises information indicating at least one of:a size of the power headroom report;a number of power headroom values comprised in the report;a number of antenna ports for which the power headroom is reported;a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

13. The user equipment of any preceding claim, wherein the means is further for: receiving, from the at least one network node, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the sent power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; andsending, to the at least one network node, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

14. An apparatus comprising means for:receiving, from a user equipment, a power headroom report indicating power headroom values associated with at least two of a plurality of antenna ports of the userequipment, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set; anddetermining, based on the power headroom report, at least one transmission power for uplink transmission by the user equipment from at least one of the plurality of antenna ports.

15. The apparatus of claim 14, wherein:the at least two of the plurality of antenna ports are associated with different uplink reference signal resources of the same uplink reference signal resource set; orthe at least two of the plurality of antenna ports are associated with the same uplink reference signal resources of the same uplink reference signal resource set.

16. The apparatus of claim 14 or 15, wherein the means is further for:sending, to the user equipment, configuration information for power headroom reporting, the configuration information being associated with uplink reference signal transmission from the plurality of antenna ports of the user equipment.

17. The apparatus of claim 16, wherein the configuration information comprises at least one of:a first threshold value for determining at least one subset of the plurality of antenna ports;an indication of at least one subset of the plurality of antenna ports;a second threshold value for triggering the user equipment to report a plurality of power headroom values in the power headroom report;a number of power headroom fields to be included in the power headroom report, wherein each power headroom field indicates the power headroom value associated with at least one of the antenna ports.

18. The apparatus of claim 17, wherein the power headroom report comprises, for each of the at least one subset of the plurality of antenna ports, a power headroom field comprising an indication of the power headroom associated with the respective at least one subset of the plurality of antenna ports, wherein for each subset a difference between the determined power headroom of one or more antenna ports comprised in the subset is less than the first threshold value.

19. The apparatus of claim 17 or 18, wherein the means is further for:receiving, from the user equipment, an indication of the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction;determining, based on the maximum possible number of simultaneously transmitting antenna ports of the user equipment in the uplink direction, the at least one subset of the plurality of antenna ports; andsending, to the user equipment, the configuration information indicating the at least one subset of the plurality of antenna ports.

20. The apparatus of any of claims 17 to 19, wherein the means is further for:receiving, from the user equipment, an indication of the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value; anddetermining the first threshold value and / or the user equipment’s preferred second threshold value based on the user equipment’s preferred first threshold value and / or the user equipment’s preferred second threshold value.

21. The apparatus of any of claims 18 to 20, wherein the plurality of antenna ports are comprised in a single subset, wherein a difference between the determined power headroom associated with the plurality of antenna ports is less than the first threshold value, and wherein the power headroom report comprises a single power headroom value associated with the plurality of antenna ports.

22. The apparatus of any of claims 14 to 21, wherein the power headroom report further comprises information indicating at least one of:a size of the power headroom report;a number of power headroom values comprised in the report;a number of antenna ports for which the power headroom is reported;a number of subsets of antenna ports for which the power headroom is reported; or an indication of the antenna ports comprised within each subset of antenna ports for which the power headroom is reported.

23. The apparatus of any of claims 14 to 22, wherein the means is further for:sending, to the user equipment, information indicating at least one transmission power for the uplink transmission by the user equipment from at least one of the plurality of antenna ports, wherein the information indicating the at least one transmission power is based on the received power headroom report indicating the determined power headroom values associated with the at least two of the plurality of antenna ports; andreceiving, from the user equipment, based on the information indicating the at least one transmission power, the uplink transmission from the at least one of the plurality of antenna ports.

24. A method comprising:obtaining configuration information for power headroom reporting, the configuration information being associated with uplink transmission from a plurality of antenna ports of the user equipment and with at least one uplink reference signal resource;determining power headroom values for the uplink signal transmission associated with each of the plurality of antenna ports of the user equipment; andsending, to the at least one network node, based on the determined power headroom values and the configuration information, a power headroom report indicating the determined power headroom values associated with at least two of the plurality of antenna ports,wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set.

25. A method comprising:receiving, from a user equipment, a power headroom report indicating power headroom values associated with at least two of a plurality of antenna ports of the user equipment, wherein the at least two of the plurality of antenna ports are associated with a same uplink reference signal resource set; anddetermining, based on the power headroom report, at least one transmission power for uplink transmission by the user equipment from at least one of the plurality of antenna ports.

Images