Method, apparatus and computer program

Abstract

There is provided a user equipment comprising: means for receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment, and means for transmitting sounding reference signals using the first subset of antenna ports. The user equipment further comprising: means for performing measurements on reference signals received from the network entity using the second subset of antenna ports, means for transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements. The user equipment further comprising: means for receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of MIMO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports, and means for receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

Description

METHOD, APPARATUS AND COMPUTER PROGRAMTECHNICAL FIELD

[0001] Various examples of this disclosure relate to methods, apparatuses, and computer programs. In particular, methods, apparatuses, and computer programs associated with a communication network, wireless networking system, or cellular communications system. BACKGROUND

[0002] 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.

[0003] 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 are the so-called 5G (5th Generation) standards provided by 3GPP.SUMMARY

[0004] Some examples of this disclosure will be described with respect to certain aspects. These aspects are not intended to indicate key or essential features of the embodiments of this disclosure, nor are they intended to be used to limit the scope thereof. Other features, aspects, and elements will be readily 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.

[0005] According to a first aspect, there is provided a user equipment comprising: means for receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; means for transmitting sounding reference signals using the first subset of antenna ports; means for performing measurements on reference signals received from the network entity using the second subset of antenna ports; means for transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report is based on the measurements; and means for receiving, from the network entity, at least one block of data in at least one downlink transmission, using at least one of: the first subset of antenna ports, or the second subset of antenna ports.

[0006] According to a second 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 to perform: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report is based on the measurements; and receiving, from the network entity, at least one block of data in at least one downlink transmission, using at least one of: the first subset of antenna ports, or the second subset of antenna ports.

[0007] According to a third aspect, there is provided a user equipment comprising: circuitry configured to perform: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; circuitry configured to perform: transmitting sounding reference signals using the first subset of antenna ports; circuitry configured to perform: performing measurements on reference signals received from the network entity using the second subset of antenna ports; circuitry configured to perform: transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report is based on the measurements; and circuitry configured to perform: receiving, from the network entity, at least one block of data in at least one downlink transmission, using at least one of: the first subset of antenna ports, or the second subset of antenna ports.

[0008] According to a fourth aspect, there is provided a method performed by a user equipment, the method comprising: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report is based on the measurements; and receiving, from the network entity, at least one block of data in at least one downlink transmission, using at least one of: the first subset of antenna ports, or the second subset of antenna ports.

[0009] According to a fifth aspect, there is provided a computer program comprising instructions, which when executed by a user equipment, cause the user equipment to performat least the following: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report is based on the measurements; and receiving, from the network entity, at least one block of data in at least one downlink transmission, using at least one of: the first subset of antenna ports, or the second subset of antenna ports.

[0010] The following are applicable to each (e.g., one or more, including all) of the above first to fifth aspects.

[0011] In some examples, the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity, wherein the channel information is determined based on the measurements.

[0012] In some examples, the channel information comprises at least one of: coefficients for a channel matrix, sparse domain information of channel matrices, sparse domain information of channel matrices including beam information and / or delay taps information, principal component related information of channel matrices using an eigenvector basis, or principal component related information of channel matrices using a discrete Fourier transform basis.

[0013] In some examples, the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements.

[0014] In some examples, the precoding matrix information comprises at least one of: a precoding matrix indicator, a channel quality indicator, a rank indicator, or a layer indicator.

[0015] In some examples, the user equipment is caused to perform: transmitting, to the network entity, sounding reference signals using the antenna ports in the set of antenna ports at the user equipment.

[0016] In some examples, the user equipment is caused to perform: performing initial measurements on reference signals received from the network entity using the antenna ports in the set of antenna ports at the user equipment; transmitting, to the network entity, an initial CSI report, wherein the initial CSI report is based on the initial measurements.

[0017] In some examples, the user equipment is caused to perform: based on a received request for capabilities of the user equipment, transmitting, to the network entity, an indication that the user equipment supports a feature related to hybrid partial CSI reporting.

[0018] In some examples, the user equipment is caused to perform: based on a received request for capabilities of the user equipment, transmitting, to the network entity, information related to antenna ports of the user equipment, the information including a predeterminedorder associated with a mapping between the antenna ports and physical antennas of the user equipment.

[0019] According to a sixth aspect, there is provided a network entity comprising: means for transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; means for receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; means for transmitting, to the user equipment, reference signals; means for receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises information related to measurements performed on the reference signals; and means for transmitting, to the user equipment, at least one block of data in at least one downlink transmission that is beamformed based on the sounding reference signals received at the network entity and the information comprised in the CSI report.

[0020] According to a seventh aspect, there is provided a network entity comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the network entity to perform: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises information related to measurements performed on the reference signals; and transmitting, to the user equipment, at least one block of data in at least one downlink transmission that is beamformed based on the sounding reference signals received at the network entity and the information comprised in the CSI report.

[0021] According to an eighth aspect, there is provided a network entity comprising: circuitry configured to perform: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; circuitry configured to perform: receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; circuitry configured to perform: receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises information related to measurements performed on the reference signals; and circuitry configured to perform: transmitting, to the user equipment, at least one block ofdata in at least one downlink transmission that is beamformed based on the sounding reference signals received at the network entity and the information comprised in the CSI report.

[0022] According to a ninth aspect, there is provided a method performed by a network entity, the method comprising: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises information related to measurements performed on the reference signals; and transmitting, to the user equipment, at least one block of data in at least one downlink transmission that is beamformed based on the sounding reference signals received at the network entity and the information comprised in the CSI report.

[0023] According to a tenth aspect, there is provided a computer program comprising instructions, which when executed by a network entity, cause the network entity to perform at least the following: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises information related to measurements performed on the reference signals; and transmitting, to the user equipment, at least one block of data in at least one downlink transmission that is beamformed based on the sounding reference signals received at the network entity and the information comprised in the CSI report.

[0024] The following are applicable to each (e.g., one or more, including all) of the above sixth to tenth aspects.

[0025] In some examples, the network entity is caused to perform: receiving, from the user equipment, an initial sounding reference signal associated with each of the antenna ports in the set of antenna ports at the user equipment; determining, for each of the antenna ports of the user equipment, whether to include the respective antenna port in the first subset of antenna ports based on measurements performed on the respective initial sound reference signal.

[0026] In some examples, the determining whether to include the respective antenna port in the first subset of antenna ports comprises: determining, for each of the antenna ports of the user equipment, whether to include the respective antenna port in the first subset of antennaports based on a comparison between measurements performed on the respective initial sound reference signal and a threshold.

[0027] In some examples, the network entity is caused to perform: transmitting, to the user equipment, initial reference signals; receiving, from the user equipment, an initial CSI report, wherein the initial CSI report is based on initial measurements performing using the antenna ports in the set of antenna ports at the user equipment; based on the initial CSI report, determining whether remaining antenna ports of the user equipment that have not been determined for the first subset of antenna ports are suitable for CSI reporting; and based on the determining, including at least one of the remaining antenna ports of the user equipment in the second subset of antenna ports.

[0028] In some examples, the network entity is caused to perform: determining CSI for a channel between the network entity and the user equipment based on the sounding reference signals received by the network entity, and the information in the CSI report, wherein the transmitting of the at least one block of data is based on the CSI that has been determined for the channel.

[0029] In some examples, the determining CSI comprises: performing a re-assembling of CSI for the channel using the sounding reference signals received by the network entity from uplink, and the information in the CSI report from downlink.

[0030] In some examples, the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity, wherein the channel information is determined based on the measurements.

[0031] In some examples, the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements.

[0032] In some examples, the network entity is caused to perform: transmitting, to the user equipment, a request for capabilities of the user equipment related to hybrid partial channel state information reporting; and receiving, from the user equipment, an indication that the user equipment supports a feature related to hybrid partial CSI reporting.

[0033] In some examples, the network entity is caused to perform: transmitting, to the user equipment, a request for capabilities of the user equipment related to hybrid partial channel state information reporting; and receiving, from the user equipment, information related to antenna ports of the user equipment, the information including a predetermined order associated with a mapping between the antenna ports and physical antennas of the user equipment.

[0034] In some examples, the network entity is caused to perform: transmitting, to the user equipment, an indication to provide channel state information reports according to explicit channel based CSI reporting.

[0035] In some examples, the network entity is caused to perform: transmitting, to the user equipment, an indication to provide CSI reports according to precoding matrix based channel state information reporting.

[0036] According to an eleventh aspect, there is provided a user equipment comprising: means for receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; means for transmitting sounding reference signals using the first subset of antenna ports; means for performing measurements on reference signals received from the network entity using the second subset of antenna ports; means for transmitting, to the network entity, a channel state information, CSI, report according to explicit channel based CSI reporting, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity, wherein the channel information is determined based on the measurements; and means for receiving, from the network entity, at least one block of data in a downlink transmission.

[0037] According to a twelfth 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 to perform: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report according to explicit channel based CSI reporting, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity, wherein the channel information is determined based on the measurements; and receiving, from the network entity, at least one block of data in a downlink transmission.

[0038] According to a thirteenth aspect, there is provided a user equipment comprising: circuitry configured to perform: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; circuitry configured to perform: transmitting sounding reference signals using the first subset of antenna ports; circuitry configured to perform: performing measurements on reference signals received from the network entity using the second subset of antenna ports; circuitry configured to perform: transmitting, to the network entity, a channel state information, CSI, report according to explicit channel based CSIreporting, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity, wherein the channel information is determined based on the measurements; and circuitry configured to perform: receiving, from the network entity, at least one block of data in a downlink transmission.

[0039] According to a fourteenth aspect, there is provided a method performed by a user equipment, the method comprising: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report according to explicit channel based CSI reporting, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity, wherein the channel information is determined based on the measurements; and receiving, from the network entity, at least one block of data in a downlink transmission.

[0040] According to a fifteenth aspect, there is provided a computer program comprising instructions, which when executed by a user equipment, cause the user equipment to perform at least the following: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report according to explicit channel based CSI reporting, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity, wherein the channel information is determined based on the measurements; and receiving, from the network entity, at least one block of data in a downlink transmission.

[0041] The following are applicable to each (e.g., one or more, including all) of the above eleventh to fifteenth aspects.

[0042] In some examples, the information further comprises an indication to provide CSI reports according to explicit channel based CSI reporting.

[0043] In some examples, the user equipment is caused to perform: generating the CSI report based on the measurements, wherein the CSI report comprises the channel information.

[0044] In some examples, the CSI report, according to explicit channel based CSI reporting, comprises at least one of: coefficients for a channel matrix in an antenna domain or in afrequency domain, sparse domain information of channel matrices including beam information, delay taps information, principal component related information of channel matrices using an eigenvector basis or a discrete Fourier transform basis or any other type of basis for space and frequency domain.

[0045] In some examples, the user equipment is caused to perform: transmitting, to the network entity, initial sounding reference signals using the antenna ports in the set of antenna ports at the user equipment.

[0046] In some examples, the user equipment is caused to perform: performing initial measurements on initial reference signals received from the network entity using the antenna ports in the set of antenna ports at the user equipment; transmitting, to the network entity, an initial CSI report, wherein the initial CSI report is based on the initial measurements.

[0047] In some examples, the user equipment is caused to perform: based on a received request for capabilities of the user equipment, transmitting, to the network entity, an indication that the user equipment supports a feature related to hybrid partial CSI reporting.

[0048] In some examples, the user equipment is caused to perform: based on a received request for capabilities of the user equipment, transmitting, to the network entity, information related to antenna ports of the user equipment, the information including a predetermined order associated with the antenna ports.

[0049] According to a sixteenth aspect, there is provided a network entity comprising: means for transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; means for receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; means for transmitting, to the user equipment, reference signals; means for receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity; and means for transmitting, to the user equipment, a block of data in a downlink transmission that is beamformed based on the sounding reference signals received at the network entity, and the channel information comprised in the CSI report.

[0050] According to a seventeenth aspect, there is provided a network entity comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the network entity to perform: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports;transmitting, to the user equipment, reference signals; receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity; and transmitting, to the user equipment, a block of data in a downlink transmission that is beamformed based on the sounding reference signals received at the network entity, and the channel information comprised in the CSI report.

[0051] According to an eighteenth aspect, there is provided a network entity comprising: circuitry configured to perform: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; circuitry configured to perform: receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; circuitry configured to perform: receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity; and circuitry configured to perform: transmitting, to the user equipment, a block of data in a downlink transmission that is beamformed based on the sounding reference signals received at the network entity, and the channel information comprised in the CSI report.

[0052] According to a nineteenth aspect, there is provided a method performed by a network entity, the method comprising: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity; and transmitting, to the user equipment, a block of data in a downlink transmission that is beamformed based on the sounding reference signals received at the network entity, and the channel information comprised in the CSI report.

[0053] According to a twentieth aspect, there is provided a computer program comprising instructions, which when executed by a network entity, cause the network entity to perform at least the following: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding referencesignals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity; and transmitting, to the user equipment, a block of data in a downlink transmission that is beamformed based on the sounding reference signals received at the network entity, and the channel information comprised in the CSI report.

[0054] The following are applicable to each (e.g., one or more, including all) of the above sixteenth to twentieth aspects.

[0055] In some examples, the CSI report, according to explicit channel based CSI reporting, comprises at least one of: coefficients for a channel matrix in an antenna domain or in a frequency domain, sparse domain information of channel matrices including beam information, delay taps information, principal component related information of channel matrices using an eigenvector basis or a discrete Fourier transform basis or any other type of basis for space and frequency domain.

[0056] In some examples, the network entity is caused to perform: receiving, from the user equipment, an initial sounding reference signal associated with each of the antenna ports in the set of antenna ports at the user equipment; determining, for each of the antenna ports of the user equipment, whether to include the respective antenna port in the first subset of antenna ports based on measurements performed on the respective initial sound reference signal.

[0057] In some examples, the determining whether to include the respective antenna port in the first subset of antenna ports comprises: determining, for each of the antenna ports of the user equipment, whether to include the respective antenna port in the first subset of antenna ports based on a comparison between measurements performed on the respective initial sound reference signal and a threshold.

[0058] In some examples, the network entity is caused to perform: transmitting, to the user equipment, initial reference signals; receiving, from the user equipment, an initial CSI report, wherein the initial CSI report is based on initial measurements performing using the antenna ports in the set of antenna ports at the user equipment; based on the initial CSI report, determining whether remaining antenna ports of the user equipment that have not been determined for the first subset of antenna ports are suitable for CSI reporting; and based on the determining, including at least one of the remaining antenna ports of the user equipment in the second subset of antenna ports.

[0059] In some examples, the network entity is caused to perform: determining CSI for a channel between the network entity and the user equipment based on the sounding reference signals received by the network entity, and the information in the CSI report, wherein thetransmitting of the at least one block of data is based on the CSI that has been determined for the channel.

[0060] In some examples, the determining CSI comprises: performing a re-assembling of CSI for the channel using the sounding reference signals received by the network entity from uplink, and the information in the CSI report from downlink.

[0061] In some examples, the network entity is caused to perform: transmitting, to the user equipment, a request for capabilities of the user equipment related to hybrid partial channel state information reporting; and receiving, from the user equipment, an indication that the user equipment supports a feature related to hybrid partial CSI reporting.

[0062] In some examples, the network entity is caused to perform: transmitting, to the user equipment, a request for capabilities of the user equipment related to hybrid partial channel state information reporting; and receiving, from the user equipment, information related to antenna ports of the user equipment, the information including a predetermined order associated with a mapping between the antenna ports and physical antennas of the user equipment.

[0063] In some examples, the network entity is caused to perform: transmitting, to the user equipment, an indication to provide channel state information reports according to explicit channel based CSI reporting.

[0064] According to a twenty-first aspect, there is provided a user equipment comprising: means for receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; means for transmitting sounding reference signals using the first subset of antenna ports; means for performing measurements on reference signals received from the network entity using the second subset of antenna ports; means for transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements means for receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of Ml MO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports; and means for receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

[0065] According to a twenty-second aspect, there is provided a user equipment comprising: at least one processor, and at least one memory storing instructions that, when executed bythe at least one processor, cause the user equipment to perform: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of Ml MO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports; and receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of Ml MO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

[0066] According to a twenty-third aspect, there is provided a user equipment comprising: circuitry configured to perform: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; circuitry configured to perform: transmitting sounding reference signals using the first subset of antenna ports; circuitry configured to perform: performing measurements on reference signals received from the network entity using the second subset of antenna ports; circuitry configured to perform: transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements; circuitry configured to perform: receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of MIMO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports; and circuitry configured to perform: receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

[0067] According to a twenty-fourth aspect, there is provided a method performed by a user equipment, the method comprising: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports atthe user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of MIMO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports; and receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

[0068] According to a twenty-fifth aspect, there is provided a computer program comprising instructions, which when executed by a user equipment, cause the user equipment to perform at least the following: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements; receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of MIMO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports; and receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

[0069] The following are applicable to each (e.g., one or more, including all) of the above twenty-first to twenty-fifth aspects.

[0070] In some examples, the information further comprises an indication to provide CSI reports according to a precoding matrix based CSI reporting procedure.

[0071] In some examples, the user equipment is caused to perform: generating the CSI report based on the measurements, wherein the CSI report comprises the precoding matrix information.

[0072] In some examples, the precoding matrix information comprises at least one of: a precoding matrix indicator, a channel quality indicator, a rank indicator, or a layer indicator.

[0073] In some examples, the user equipment is caused to perform: transmitting, to the network entity, initial sounding reference signals using the antenna ports in the set of antenna ports at the user equipment.

[0074] In some examples, the user equipment is caused to perform: performing initial measurements on reference signals received from the network entity using the antenna ports in the set of antenna ports at the user equipment; transmitting, to the network entity, an initial CSI report, wherein the initial CSI report is based on the initial measurements.

[0075] In some examples, the user equipment is caused to perform: based on a received request for capabilities of the user equipment, transmitting, to the network entity, an indication that the user equipment supports a feature related to hybrid partial CSI reporting.

[0076] In some examples, the user equipment is caused to perform: based on a received request for capabilities of the user equipment, transmitting, to the network entity, information related to antenna ports of the user equipment, the information including a predetermined order associated with the antenna ports.

[0077] According to a twenty-sixth aspect, there is provided a network entity comprising: means for transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; means for receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; means for transmitting, to the user equipment, reference signals; means for receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information; and means for transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment and the network entity; and means for transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix information comprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

[0078] According to a twenty-seventh aspect, there is provided a network entity comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the network entity to perform: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from theuser equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information; and transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment and the network entity; and transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix information comprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

[0079] According to a twenty-eighth aspect, there is provided a network entity comprising: circuitry configured to perform: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; circuitry configured to perform: receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; circuitry configured to perform: transmitting, to the user equipment, reference signals; circuitry configured to perform: receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information; circuitry configured to perform: transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment and the network entity; and circuitry configured to perform: transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix information comprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

[0080] According to a twenty-nineth aspect, there is provided a method performed by a network entity, the method comprising: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information; and transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment andthe network entity; and transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix information comprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

[0081] According to a thirtieth aspect, there is provided a computer program comprising instructions, which when executed by a network entity, cause the network entity to perform at least the following: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information; and transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment and the network entity; and transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix information comprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

[0082] The following are applicable to each (e.g., one or more, including all) of the above twenty-sixth to thirtieth aspects.

[0083] In some examples, the precoding matrix information comprises at least one of: a precoding matrix indicator, a channel quality indicator, a rank indicator, or a layer indicator.

[0084] In some examples, the network entity is caused to perform: receiving, from the user equipment, an initial sounding reference signal associated with each of the antenna ports in the set of antenna ports at the user equipment; determining, for each of the antenna ports of the user equipment, whether to include the respective antenna port in the first subset of antenna ports based on measurements performed on the respective initial sound reference signal.

[0085] In some examples, the determining whether to include the respective antenna port in the first subset of antenna ports comprises: determining, for each of the antenna ports of the user equipment, whether to include the respective antenna port in the first subset of antenna ports based on a comparison between measurements performed on the respective initial sound reference signal and a threshold.

[0086] In some examples, the network entity is caused to perform: transmitting, to the user equipment, initial reference signals; receiving, from the user equipment, an initial CSI report,wherein the initial CSI report is based on initial measurements performing using the antenna ports in the set of antenna ports at the user equipment; based on the initial CSI report, determining whether remaining antenna ports of the user equipment that have not been determined for the first subset of antenna ports are suitable for CSI reporting; and based on the determining, including at least one of the remaining antenna ports of the user equipment in the second subset of antenna ports.

[0087] In some examples, the network entity is caused to perform: determining first CSI for a channel between the network entity and the user equipment based on the sounding reference signals received by the network entity, and second CSI for the channel based on the information in the CSI report, wherein the first downlink transmission is based on the first CSI and the second downlink transmission is based on the second CSI.

[0088] In some examples, the network entity is caused to perform: transmitting, to the user equipment, a request for capabilities of the user equipment related to hybrid partial channel state information reporting; and receiving, from the user equipment, an indication that the user equipment supports a feature related to hybrid partial CSI reporting.

[0089] In some examples, the network entity is caused to perform: transmitting, to the user equipment, a request for capabilities of the user equipment related to hybrid partial channel state information reporting; and receiving, from the user equipment, information related to antenna ports of the user equipment, the information including a predetermined order associated with a mapping between the antenna ports and physical antennas of the user equipment.

[0090] In some examples, the network entity is caused to perform: transmitting, to the user equipment, an indication to provide channel state information reports according to precoding matrix based CSI reporting.

[0091] A computer product stored on a medium may cause an apparatus to perform the methods as described herein.

[0092] A non-transitory computer readable medium comprising program instructions, that, when executed by an apparatus, cause the apparatus to perform the methods as described herein.

[0093] An electronic device may comprise apparatus as described herein.

[0094] Various other aspects and further embodiments are also described in the following detailed description and in the attached claims.

[0095] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims. The embodiments that do not fall under the scope of the claims are to be interpreted as examples useful for understanding the disclosure.

[0096] List of Abbreviations:AN: Access NetworkBS: Base StationCN: Core NetworkCSI: Channel state informationCSIT : CSI feedback to transmitterDL: Downlink eNB: eNodeB gNB: gNodeBLTE: Long Term EvolutionMIMO: Multiple in multiple outNG-RAN: Next Generation Radio Access NetworkNF: Network FunctionNR: New RadioNW: NetworkPDSCH: Physical downlink shared channelPLMN: Public Land Mobile NetworkRAN: Radio Access NetworkRF: Radio FrequencyRS: Reference signalSRS: Sounding reference signalTDD: Time division duplexUE: User EquipmentUL: Uplink3GPP: 3rdGeneration Partnership Project5G: 5thGeneration5GC: 5G Core network5G-AN: 5G Radio Access Network5GS: 5G SystemBRIEF DESCRIPTION OF DRAWINGS

[0097] Some examples will now be described, by way of illustrative and non-limiting example only, with reference to the accompanying drawings in which:

[0098] FIG. 1 shows a schematic representation of a 5G communication system;

[0099] FIG. 2 shows a schematic representation of an apparatus for the 5G communication system of FIG. 1 ;

[0100] FIG. 3 shows a schematic representation of a communication device;

[0101] FIG. 4 shows a schematic representation of signalling between a user equipment and a network entity for CSIT and non-CSIT;

[0102] FIG. 5 shows an example graphical representation of the relationship between SRS quality and distance between a user equipment and a network entity;

[0103] FIG. 6 shows a schematic representation of a baseband model for different antenna port SRS qualities associated with the graphical representation of FIG. 5;

[0104] FIG. 7 shows a schematic representation of explicit channel based CSI between a user equipment and a network entity;

[0105] FIG. 8 shows a schematic representation of precoding matrix based CSI between a user equipment and a network entity;

[0106] FIG. 9 shows a schematic representation of signalling between a network entity and a user equipment for the selection of antenna ports to be used for SRS at the user equipment;

[0107] FIG. 10 shows an example signalling and operations diagram for a user equipment and a network entity for hybrid LIL / DL CSI acquisition;

[0108] FIG. 11 shows an example flow diagram for a re-configuring of a hybrid LIL / DL CSI acquisition scheme;

[0109] FIG. 12 shows an example method flow diagram performed by an apparatus;

[0110] FIG. 13 shows another example method flow diagram performed by an apparatus;

[0111] FIG. 14 shows another example method flow diagram performed by an apparatus;

[0112] FIG. 15 shows another example method flow diagram performed by an apparatus;

[0113] FIG. 16 shows another example method flow diagram performed by an apparatus;

[0114] FIG. 17 shows another example method flow diagram performed by an apparatus; and

[0115] FIG. 18 shows a schematic representation of an apparatus.DETAILED DESCRIPTION

[0116] Channel state information (CSI) refers to the knowledge of a (radio) channel between a transmitter and receiver (e.g., a user equipment (UE) and a base station). In multiple-in multiple-out (MIMO) systems, CSI comprises information such as signal strength, phase shifts, time delays, and / or fading characteristics. CSI-based downlink beamforming in MIMO systems utilises CSI to optimize the transmission of data from a base station (e.g., gNodeB (gNB)) toa UE or other communication device. MIMO leverages multiple antennas at both the transmitter and receiver ends. By utilizing these multiple antennas, MIMO systems can transmit and receive data simultaneously, resulting in increased data throughput and improved signal quality.

[0117] There are various ways to obtain CSI in a MIMO system, such as by using reference signals (also referred to as ‘pilot signal’), or according to channel reciprocity. When using reference signals, a gNB transmits dedicated reference signals that a UE measures and uses to estimate a channel response. When obtaining CSI based on channel reciprocity (e.g., in time division duplex (TDD) systems), the network relies on uplink and downlink channels exhibiting similar characteristics (reciprocity) with a time difference. By analysing uplink transmissions from a UE (e.g., when a UE transmits sounding reference signals (SRS)), the gNB infers information about the downlink channel.

[0118] Based on the acquired CSI, the gNB is able to perform beamforming. In order to perform the beamforming, the gNB may perform beamforming weight calculation, using the CSI. The weights that are calculated are adjustments applied to the DL signal before transmission. The gNB may also perform a steering of the signal. By adjusting the weights, the gNB can steer the downlink signal in a specific direction, focusing the energy towards a location of the UE. A benefit of beamforming is that it may improve signal strength by focusing the downlink signal, and enhancing the received signal strength at the UE. This leads to better signal quality and data rates. Reduced interference may also be achieved through beamforming as the beamforming reduces energy wasted on irrelevant directions, minimizing interference with other UEs sharing the same frequency band. Furthermore, the improved signal quality and reduced interference allow the system to handle more UEs simultaneously without significant performance degradation, such that there is an increased system capacity.

[0119] Depending on the number, and type of resources that are available for CSI, different types of CSI-based beamforming techniques may be employed. CSI feedback to the transmitter (CSIT) comprises a communication device (e.g., a UE) providing CSI information to a gNB, such as Type I or Type II CSI feedback (e.g., in a CSI report). This information may comprise an implicit or explicit indication of precoding matrices (e.g., as specified in 3GPP standards) or explicit channel based CSI information. With explicit channel based CSI feedback, the actual measurements performed on a channel may be provided to the gNB, or other measured coefficients. Due to this, channel based CSI feedback has the advantage of a reduced computational complexity at the UE as it skips the precoding matrices calculation at the UE. Also it possesses the inherent capability of providing all channel characteristics as measured in the UE. For non-CSIT beamforming, the gNB does not rely on CSI feedback from the UE, and instead relies on signals (e.g., SRS) received on the UL, as is done in SRS baseddownlink beamforming. These two techniques (i.e., CSIT and non-CSIT) are depicted in FIG.4.

[0120] FIG. 4 shows a schematic representation of signalling between a user equipment and a network entity for CSIT and non-CSIT.

[0121] A network entity (e.g., a gNB) 401 is able to communicate with a communication device (e.g., a UE) 403 via a channel. The gNB 401 may be configured to transmit DL transmissions to the UE 403 using beamforming techniques that are based on CSI for the channel. In order to obtain the CSI, CSIT or non-CSIT methods may be used.

[0122] For non-CSIT, the UE 403 transmits SRSs 405 in the UL to the gNB 401. For CSIT, the gNB 401 transmits RSs 407 in the DL to the UE 403. The UE 403 receives and measures the RSs 407. The UE 403 then transmits a CSI report 409 to the gNB 401 in the UL, wherein the CSI report is based on the measurements of the RSs.

[0123] For CSI acquisition accuracy, the effectiveness of CSI-based beamforming depends on the accuracy of the acquired CSI. Factors like fast-changing channel conditions or high user mobility can impact accuracy. For feedback overhead (e.g., for CSIT), explicit (either from precoding matrices, e.g. Type II or direct channel) CSI feedback from the UE can introduce additional signalling and bit reporting overhead in order to achieve an improved CSI accuracy. For SRS overhead, the use of SRS with non-CSIT-based beamforming represents additional signalling overhead from the UE. For computational complexity, beamforming weight calculation can add computational complexity at the gNB. These challenges and considerations may be taken into account when determining whether CSIT or non-CSIT is suitable to be used for CSI acquisition in a communication system.

[0124] In many 5G TDD networks, CSI-based downlink beamforming utilises SRS based CSI acquisition as long as the UE is within a threshold range of the gNB allowing the SRS to be received with sufficient quality. When the UE goes beyond that SRS quality range, the network switches to CSI coming from CSIT (with less accuracy than SRS based CSI).

[0125] For SRS based downlink MIMO beamforming (non-CSIT), uplink signals from a UE are used to improve the quality of downlink transmissions sent from a gNB to the UE. Firstly, the UE transmits SRS from the UE to the gNB in the uplink. In TDD systems like 5G NR, the uplink and downlink channels are similar (reciprocal) with a slight time difference. The gNB analyses the received SRS to understand the channel between itself and the UE. Based on the channel estimation, the gNB calculates weights to adjust the downlink signal. The gNB applies these weights to the downlink signal, focusing the energy towards the UE's location. Benefits of this include: stronger signals (focused beams lead to stronger received signals at the UE, improving data rates and quality), reduced Interference (beamforming minimizes energywasted on irrelevant directions, reducing interference with other UEs), and increased capacity (improved signal quality and reduced interference allow the system to handle more UEs simultaneously with the use of multi-user MIMO). However, there may be limitations related to channel estimation accuracy and signalling overhead. Fast-changing channels or high UE mobility can affect the accuracy of channel estimation and beamforming. This is worsened due to the need of splitting the SRS transmission in frequency and / or antenna domain in order to tackle the lack of UE specific resources. Furthermore, as discussed above, sending and processing SRS signals requires additional UE specific resources, so a balance is needed.

[0126] In 5G frequency ranges below 6 GHz and 6G frequency ranges below 15GHz, UE antenna patterns are directive. When a UE is in use, a user may cover one or more of the physical antennas with their hand while gripping the UE. A user’s hand may attenuate, unevenly, some of the antenna(s) of the smartphone over others of the antennas. This means that, while some of the antennas, are suitable to be used for SRS based CSI acquisition, other antennas may not be. This is depicted in FIG. 5.

[0127] FIG. 5 shows an example graphical representation of the relationship between SRS quality and distance between a user equipment and a network entity.

[0128] On the x-axis of FIG. 5 is a distance (between a UE and a gNB). On the y-axis is the per antenna port (of the UE) SRS power. There is an indication on the y-axis of the SRS target power level, and a lower SRS power threshold (i.e. , a minimum power). Below the lower SRS power threshold, the antenna port would not be suitable for SRS (for CSI acquisition).

[0129] An antenna port is defined such that a channel over which a symbol on the antenna port is conveyed may be inferred from the channel over which another symbol on the same antenna port is conveyed. In this manner, an antenna port is a logical entity rather than a physical antenna element. Each antenna port may be associated with a specific set of reference signals. Specific transmissions use specific antenna ports and then those antenna ports are mapped onto one or more physical antenna elements. Mapping between antenna port and physical antenna may be: one to one, or one to many. One to one mapping is useful when operating in lower frequency bands which do not require beamforming (beamforming uses multiple physical antenna elements). While one to many mapping is useful for beamforming in higher frequency bands.

[0130] There is shown a UE 501 with four antenna ports. The four antenna ports may be mapped to four physical antenna elements. In a first case / scenario (CASE1), all four of the antenna ports are transmitting with suitable power / quality to a gNB 503. This is indicated with the line labelled 505. In a second case (CASE2), the UE is moving further from the gNB 503 and / or a user of the UE is blocking antenna(s), which means that one of the four antenna portsis not suitable for SRS. This is indicated with the line labelled 507. In a third case (CASE3), the UE is moving further from the gNB 503 and / or a user of the UE is blocking antenna(s), which means that two of the four antenna ports are not suitable for SRS. This is indicated with the line labelled 509. In a fourth case (CASE4), the UE is moving further from the gNB 503 and / or a user of the UE is blocking antenna(s), which means that three of the four antenna ports are not suitable for SRS. This is indicated with the line labelled 511. As indicated with lines 505-511 , the further that the UE 501 moves away from the gNB 503 the lower the SRS power per antenna port.

[0131] When one or more of the antenna ports are not suitable for SRS transmission, in current 5G systems, the UE may change the function / configuration of all 4 antenna ports, and stop using SRS based CSI and instead switch to use CSI feedback from the UE. Alternatively, the UE could continue to use all 4 antenna ports for SRS (even those antenna ports that do not meet the quality threshold), but at the cost of dropping one or more layers for Ml MO. Stated differently, the UE could continue, for example, to use 3 (good) antenna ports for SRS keeping also the 4th(bad) antenna port that does not meet the quality threshold, but this would be at the cost of dropping 1 layer for MIMO, with an unnecessary SRS transmission in all 4 antenna ports.

[0132] A baseband model of the uplink received signal at the gNB 503 from the UE 501 is depicted in FIG. 6. As discussed above alongside FIG. 5, in CASE1 all UE antenna ports transmit SRS with sufficient quality, then progressively as the UE 501 is moving further away from the gNB 503 and / or a user’s hand is covering antenna unevenly, CASE2, CASE3 and CASE4 then represent the progressive limitation of sounding (or determining) the H matrix via SRS. The H matrix is the matrix that represents the (radio) channel between the UE and gNB.

[0133] FIG. 6 shows a schematic representation of a baseband model for different antenna port SRS qualities associated with the graphical representation of FIG. 5.

[0134] In CASE1 601 , all of the four antenna ports of the UE 501 are used for transmitting SRS to the gNB 503. In the example of FIG. 6, there are 4 layers for MIMO, wherein ‘s’ represents a antenna port for SRS of the UE 501 , and ‘r’ represents a virtual antenna port of the gNB 503. In this manner, there is a 4x4 matrix for the H matrix.

[0135] When sounding (or determining) the H matrix, the gNB attempts to map channel links (or simply links’) of the 4 antenna ports of the UE to 4 antenna ports of gNB. When losing an antenna port from UE (i.e., when the antenna port is no longer suitable for transmitting SRS), the 4x4 matrix cannot be fully determined. This is depicted in CASE 2 603, CASE3 605 and CASE4 607. In CASE2 603, the antenna port ‘s4’ is not usable for SRS. In CASE3 605, antenna ports ‘s4’ and ‘s3’ are not usable for SRS. In CASE4, antenna ports ‘s4’, ‘s3’, and ‘s2’are not usable for SRS. In this manner, when using SRS in order to determine CSI at the gNB, the distance between the UE and the gNB may have a negative effect on the power / quality of the SRS being received by the gNB.

[0136] As described above, rather than using SRS based CSI acquisition, CSI-RS based CSI acquisition may be utilised. However, this involves the gNB transmitting RSs, the UE measuring those RSs and generating a CSI report before transmitting it to the gNB. This may increase signalling overhead, and increase processing at the UE.

[0137] One or more of the examples described below aim to address one or more of the problems identified above.

[0138] In examples, there is a user equipment (UE) which is configured to perform a method comprising: receiving, from a network entity (e.g., a gNB), information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment. The method further comprising: transmitting sounding reference signals using the first subset of antenna ports, and performing measurements on reference signals received from the network entity using the second subset of antenna ports. The method also comprises transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report is based on the measurements. The method further comprises: receiving, from the network entity, at least one block of data in at least one downlink transmission, using at least one of: the first subset of antenna ports, or the second subset of antenna ports.

[0139] This example will be described in more detail below, alongside FIGS. 4 to 18.

[0140] Before explaining the examples above in greater detail, an example communication device (as shown in FIG. 3) that is capable of transmitting SRS, and / or capable of determining and transmitting CSI reports will be described. The communication device is part of a communication system (as shown in FIG. 1). The communication device is able to communicate with one or more of the entities of the communication system (as shown in FIG. 1) via an apparatus (as shown in FIG. 2), which may be part of / comprised in a base station. As described above, a base station and communication device may communicate with each other, such that the base station is able to send DL transmissions to the communication device, e.g., using DL beamforming in MIMO.

[0141] Certain general aspects of the communication system and the communication device are briefly explained with reference to FIGS. 1 to 3 to assist in understanding the technology underlying the described examples.

[0142] FIG. 1 shows a schematic representation of a 5G communication system 100. In this manner, FIG. 1 illustrates an example of a communication network to which examples disclosed herein may be applied. The communication network or a cellular communication network may comprise a network node 110 providing one or more cells, such as cell 100, and a network node 112 providing one or more other cells, such as cell 102. Each cell may be, e.g., a macro cell, a micro cell, femto, or a pico cell, for example. The cell may define a coverage area or a service area of the corresponding access node.

[0143] The network node 110 may provide a user equipment (UE) 120 (one or more UEs) with wireless access to the communication network. The wireless access may comprise downlink (DL) communication from the network node to the UE 120 and uplink (UL) communication from the UE 120 to the network node. Examples of uplink channels comprise physical uplink control channel (PUCCH) for transmitting control information and physical uplink shared channel (PUSCH) for transmitting data towards the network. Examples of downlink channels comprise physical downlink control channel (PDCCH) for transmitting control information and physical downlink shared channel (PDSCH) for transmitting data towards the user equipment.

[0144] There may be a plurality of UEs 120, 122 in the system. Each of them may be served by the same or by different network nodes 110, 112. UE may be configured with dual connectivity (DC), wherein the UE, e.g. UE 120, may be connected to multiple network nodes 110, 112. The UEs 120, 122 may communicate with each other, in case device-to-device (D2D) communication interface is established between them via a so-called sidelink (SL). Such D2D communications may be referred to as machine-to-machine, peer-to-peer (P2P) communications, or vehicle-to-vehicle (V2V), for example.

[0145] In the case of multiple network nodes in the communication network, the network nodes may be connected to each other via an interface. LTE specifications call such an interface as X2 interface. An interface between an LTE node and a 5G node, or between two 5G nodes may be called Xn interface.

[0146] The network nodes 110 and 112 may be further connected via another interface to a core network 116 of the communication network. The LTE specifications specify the core network as an evolved packet core (EPC), and the core network may comprise e.g. a mobility management entity (MME) and a gateway node. The MME may handle mobility of terminal devices in a tracking area encompassing a plurality of cells and handle signalling connections between the terminal devices and the core network. The gateway node may handle data routing in the core network and to / from the terminal devices. The 5G specifications specify the core network as a 5G core (5GC). The 5G core may comprise e.g. an access and mobility management function (AMF) and a user plane function / gateway (UPF) and other functions.1The AMF may handle termination of non-access stratum (NAS) signalling, NAS ciphering & integrity protection, registration management, connection management, mobility management, access authentication and authorization, security context management. The UPF node may support packet routing and forwarding, packet inspection and quality of service (QoS) handling, for example.

[0147] FIG. 2 illustrates an example of an apparatus 200. The apparatus 200 may be for the 5G communication system of FIG. 1. The apparatus 200 may be for controlling a function of one or more network entities and / or network functions, such as the entities of the 5G-RAN or the 5GC as illustrated on FIG. 1. The apparatus 200 comprises at least one random access memory (RAM) 211a, at least one read only memory (ROM) 211 b, at least one processor 212, 213 and an input / output interface 214. The at least one processor 212, 213 is coupled to the RAM 211a and the ROM 211 b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215. The software code 215 may for example allow to perform one or more steps to perform one or more of the present aspects or examples. The software code 215 may be stored in the ROM 211 b. The apparatus 200 may be interconnected with another apparatus 200 controlling another entity / function of the 5G-AN or the 5GC. . In some examples, apparatus 200 may be configured to provide one or more functions of the 5G-AN or the 5GC. For example, apparatus 200 may be configured to perform at least some functionality of a particular function of the 5G-AN or the 5GC. For example, apparatus 200 may be configured to operate as a particular function of the 5G-AN or the 5GC. In alternative examples, apparatus 200 may be configured to perform at least some functionality of two or more functions of the 5G-AN and / or the 5GC. For example, apparatus 200 may be configured to operate as two or more functions of the 5G-AN and / or the 5GC. The apparatus 200 may comprise one or more circuits, or circuitry (not shown) which may be configured to perform one or more of the present aspects or examples.

[0148] FIG. 3 illustrates an example of a communication device 300. The communication device 300 may be similar to the communication device 102 illustrated in 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 are a user equipment, a terminal, 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, a Cellular Internet of things (CloT) device, or a terrestrial / maritime / aerial vehicle such as a car, a truck, a boat, an air plane, or a drone, or any combinations of these or the like. The communication device 300 may provide, for example, communication of data for carrying communications. Thecommunications may be one or more of voice, electronic mail (email), text message, multimedia, data, machine data and so on.

[0149] The communication device 300 may receive signals over an air or radio interface 307 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In FIG. 3, a transceiver apparatus is designated schematically by block 306. The transceiver apparatus 306 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

[0150] 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 systems 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 of the present aspects. The software code 308 may be stored in the ROM 302a. The communication device 300 may comprise one or more circuits, or circuitry (not shown) which may be configured to perform one or more of the present aspects or examples.

[0151] The processor, storage and other relevant control apparatus may be provided on an appropriate circuit board and / or in chipsets. This feature is denoted by reference 304. The communication device may optionally have a user interface such as keypad 305, touch sensitive screen or 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 the device.

[0152] In examples, there is provide a method for CSI acquisition which combines information that is obtainable from SRS (in the UL) and information from a CSI report that is based on measurements of CSI-RS (in the DL). As both UL and DL information is utilised for CSI acquisition, this may be referred to as a hybrid UL / DL CSI acquisition. It should be understood that the term ‘hybrid UL / DL CSI acquisition’ is an example only. In other examples, other suitable terms or descriptors may be used.

[0153] The hybrid UL / DL CSI acquisition may involve a communication device (e.g., a UE), and a network entity (e.g., a gNB). A UE has a set of antenna ports, wherein each antenna port in the set may be used for SRS transmission or reception of CSI-RS. In some examples, a subset of the antenna ports may be suitable for SRS transmission, wherein other antenna ports in the set may be used for CSI-RS reception. In this manner, at the network side, a gNB is able to determine (or recover) beamforming information for one or more layers of a channel(between the UE and gNB) based on the SRS received at the gNB. The gNB then determines beamforming information for the remaining layers of the channel based on a CSI report that is received from the UE, wherein the CSI report is based on measurements of CSI-RS. The CSI report that is sent, from the UE to the gNB, may comprise different information. In some examples, the CSI report may comprise a first type of information (herein referred to as explicit channel based CSI reporting), or a second type of information (herein referred to as precoding matrix based CSI reporting). These examples will be described in more detail below.

[0154] As described above, a communication device (e.g., a UE) may be configured to measure RSs (CSI-RSs) and then send a CSI report, wherein the CSI report is based on the measured RSs. A UE may be configured to / instructed to provide a CSI report according to explicit channel based CSI reporting, which is depicted in FIG. 7.

[0155] FIG. 7 shows a schematic representation of explicit channel based CSI between a user equipment and a network entity.

[0156] As shown in the example of FIG. 7, a UE has eight antenna ports 701. The eight antenna ports 701 may be considered to be a set of antenna ports (of the UE). A first subset 703 of the antenna ports 701 comprises four antenna ports. A second subset 705 of the antenna ports 701 comprises the other four antenna ports. In this example, the antenna ports in the first subset 703 and the second subset 705 do not overlap (i.e., there are the same antenna ports in both subsets 703, 705). In other examples, there may be at least one overlapping antenna port in both subsets 703, 705.

[0157] The UE obtains information related to the first subset 703 and second subset 705. The information may indicate at least one of the first subset 703 or the second subset. The information may be used to determine at least one of the first subset 703 or the second subset (e.g., information indicates that first subset = 5 out of 8 antenna ports, using this information the UE determines 3 remaining antenna ports of the 8 for the second subset). In some examples, the obtaining may comprise the UE selecting antenna ports to be included in at least one of the first antenna set 703 or the second antenna set 705. When the UE selects antenna ports, the UE may inform the gNB about the selection (e.g., about the first subset 703 and / or second subset 705). In other examples, the obtaining may comprise the UE receiving the information (e.g., from the network entity / gNB) related to the first subset 703 and second subset 705. The second subset 705 may be referred to as a complementary subset (or group) of antenna ports.

[0158] The antenna ports in the first subset 703 are to be used for SRS transmission. The antenna ports in the second subset 705 are to be used for reception of CSI-RS. The (obtained) information may indicate whether a subset should be used for SRS or CSI-RS.

[0159] In some examples, antenna ports for SRS (e.g., for the first subset 703) are grouped by a rule. For example, antenna ports with attenuation characteristics below a threshold and a power above a threshold are used for SRS-based CSI acquisition. Then, the complementary antenna ports (e.g., remaining antenna ports that are not selected for SRS) are used to determine CSI from DL via DL CSI-RS-based CSI acquisition / feedback (e.g., for the second subset 705).

[0160] CSI is determined based on information measured by the network (i.e., from SRS with the first subset 703 of antenna ports) and measured by the UE (i.e., from measured CSI-RS with the second subset 705 of antenna ports). First CSI 707 is measured by the network / gNB from the received SRS sent by the UE using the first subset 703 of the antenna ports 701. Second CSI is measured with the second subset 705 of the antenna ports 701 during DL CSI- RS reception.

[0161] The CSI-RS measured by the second subset 705 of antenna ports 701 are used to determine (or generate) a CSI report at the UE. For explicit channel based CSI reporting, the UE includes channel information (also referred to as ‘information about the channel’) in the CSI report. The channel information is related to the (radio) channel between the UE and the gNB. With explicit channel based CSI reporting, the UE does not (need to) calculate precoding matrices operations (e.g., precoding matrix approximation and / or exhaustive search for precoding matrix indices into a codebook). Some examples of channel information that may be comprised in the CSI report include: coefficients for a channel matrix (also referred to as H-matrix coefficients, or channel matrix coefficients) in an antenna domain and / or in a frequency domain, sparse domain information of the channel matrices including beam information and / or delay taps information, principal component related information of the channel matrices using an eigenvector basis, a discrete Fourier transform (DFT) basis or any other type of basis for space and / or frequency domain. The coefficients for the channel matrix may be considered gNB-UE links, or TX-Rx links.

[0162] The UE may receive an indication (or instruction) to provide a CSI report according to explicit channel based CSI reporting. For example, the gNB may send the indication to the UE. In other examples, the default CSI reporting may be channel based CSI reporting. Stated differently, the UE is preconfigured to provide the CSI report with channel information (e.g.,, the UE does not receive the indication to use channel based CSI reporting, as channel based CSI reporting is already configured by default).

[0163] In the explicit channel based CSI, a compressed CSI has an information signaling overhead proportional to the number of Rx antenna ports (or physical antennas). Due to this, a balancing of the UE antenna ports used for DL and UL is useful to control the signaling “bitoverhead” from the CSI obtained from the CSI DL acquisition, and / or the overhead due to SRS transmission in the UL channel.

[0164] It should be understood that the UE having eight antenna ports is an example only. In other examples, there may be fewer, or more, than eight antenna ports. Furthermore, it should be understood that the grouping of antenna ports within the set to form subsets is an example only.

[0165] Instead of providing a CSI report according to explicit channel based CSI reporting, the UE may utilise a precoding matrix based CSI reporting, which is depicted in FIG. 8.

[0166] FIG. 8 shows a schematic representation of precoding matrix based CSI between a user equipment and a network entity.

[0167] In a similar manner to FIG. 7, in FIG. 8, a UE has a set of antenna ports (e.g., a total of eight antenna ports). There is provided a first subset of the antenna ports and a second subset of the antenna ports (not shown in FIG. 8). In this example, the antenna ports in the first subset and the second subset do not overlap (i.e., there are the same antenna ports in both subsets). In other examples, there may be at least one overlapping antenna port in both subsets. The UE may receive information (e.g., from a network entity / gNB) that indicates the antenna ports in the first subset and second subset. The second subset may be referred to as a complementary subset (or group) of antenna ports.

[0168] The antenna ports in the first subset are to be used for SRS transmission. The antenna ports in the second subset are to be used for reception of CSI-RS. The information received by the UE may indicate whether a subset should be used for SRS or CSI-RS.

[0169] Antenna ports in the second subset are used for receiving and measuring CSI-RS from the gNB. The UE will send a CSI report, to the gNB, based on the measurements. According to precoding matrix based CSI reporting, the UE will determine precoding matrix information (also referred to as ‘information about a precoding matrix’) based on the measurements. The precoding matrix information is comprised in the CSI report that is sent to the gNB.

[0170] In some examples, antenna ports for SRS are selected (the first subset) and the remaining antenna ports (non-selected SRS ports) are used for CSI-RS reception (the second subset). By creating two subsets (or groups) of UE antenna ports, a PDSCH transmission (Tx) toward the UE is split into two transmissions. The two transmissions may be referred to as two instances, two Tx instances, or two parts, in other examples. For a first PDSCH Tx, the gNB obtains CSI from uplink SRS transmitted by the UE using the first subset of antenna ports. For a second PDSCH Tx, the gNB obtains CSI based on received CSI feedback from the UE, wherein the UE uses the second subset of antenna ports to determine precoding matrixinformation and other channel state information such as at least one of: a precoding matrix indicator (PMI), a channel quality indicator (CQI), a rank indicator (Rl), or a layer indicator (LI). In the example of FIG. 8, the first PDSCH Tx comprises a first number of MIMO layers of a channel, while the second PDSCH Tx comprises a second number of MIMO layers of the channel. The first and the second PDSCH transmissions, together, make up the full channel. The first PDSCH Tx (with CSI from SRS) is transmitted by the gNB, and received by the first subset of antenna ports at the UE. The second PDSCH Tx (with CSI from the CSI report) is transmitted by the gNB, and received by the second subset of antenna ports at the UE. This is depicted in FIG. 8.

[0171] In other examples, precoding matrix based CSI may be implemented by means of a hybrid UL / DL CSI scheme with a single PDSCH Tx (from the gNB) to all UE antenna ports. In this example, different types of implementations may be considered. For example, all the UE antenna ports may be used for CSI-RS reception (there may still be a subset of antenna ports used for SRS). In this example, there would be an overlapping of antenna ports being comprises in a first subset (for SRS) and a second subset (for CSI-RS). In some other examples, one or more UE antenna ports may be removed (i.e., not used for CSI-RS reception) when the measurements are below a power threshold.

[0172] In some examples, when there is a single PDSCH transmission to all UE antenna ports, the CSI report from the UE comprises information related to ‘missing’ MIMO layers. In this context, a ‘missing’ MIMO layer refers to CSI that could not be determined from SRS measurements at the gNB. This is because a subset of the antenna ports (e.g., the first subset) were selectable and usable for SRS. If the gNB has determined CSI for fewer than all of the MIMO layers, the gNB informs the UE about a measured rank in UL, in order to restrict the UE CSI reporting to a number of remaining MIMO layers. The gNB may send, to the UE, further information obtained from UL SRS channel acquisition. This further information may be used to facilitate orthogonal CSI layer recovery from DL CSI-RS. The type of the further information may be reference information, e.g. a list of selected beams, averaged CSI, or up to a near ground truth CSI in a long-term window. With the further information, non-precoded CSI-RS may be used. Then, the UE knows how to determine CSI feedback restricted by at least one of: the indication of the measured rank in the NW side (from UL SRS), or the additional information provided by the gNB. The UE then reports the other remaining MIMO layers (thus skipping the MIMO layers already recovered from UL). In other examples, the gNB may not assist the UE by providing the further information. Instead, the gNB provides a measured rank in uplink SRS. In order to enforce channel recovery, the CSI-RS may be precoded in a way that enables the acquisition of the other MIMO layers to those MIMO layers recovered in UL. The gNB may re-combine both the layer information obtained from UL (from SRSmeasurements) and the layer information obtained from DL (DL CSI reporting) and ensure layer re-orthogonalization.

[0173] The example depicted in FIG. 8 shows precoding matrix based CSI, which could enable a single PDSCH Tx from the gNB, or a separated PDSCH Tx per subset of antenna port at the UE (e.g., two transmissions, such that there is a transmission for each of the two subsets of antenna ports at the UE). In this example, there are four MIMO transmission layers 801 (also referred to as ‘MIMO layers’, or ‘MIMO streams’). In an example whereby there are separated PDSCH transmissions, a first PDSCH Tx (from the gNB to the UE) comprises the first two layers 803 of the four MIMO layers. A second PDSCH Tx (from the gNB to the UE) comprises the second two layers 805 of the four MIMO layers. The first two layers 803 are related to UL SRS measurements. The gNB determines first CSI 807 for the first two layers 803 based on the SRS that are received at the gNB. The second two layers 805 are related to DL CSI-RS measurements (performed by the UE). The gNB determines second CSI 809 for the second two layers based on a CSI report that is received from the UE, wherein the CSI report comprises precoding matrix information that is based on measurements performed by the UE. Based on the first CSI 807, the gNB will beamform the first instance PDSCH Tx to the first subset of antenna ports at the UE. Based on the second CSI 809, the gNB will beamform the second instance PDSCH Tx to the second subset of antenna ports at the UE.

[0174] In some examples, a UE will receive a CSI reporting configuration from the gNB (e.g., via higher layer or radio resource control (RRC) signaling). For a given CSI reporting configuration, a UE may be configured with associated SRS resources and antenna ports for antenna switching (e.g., xTyR). In xTyR, ‘x’ indicates a number of Tx antenna ports and y indicates a number of Rx antenna ports. The Tx and Rx are from the point of view of the UE, such that Tx is UL and Rx DL. The associated SRS resources may be all of the y / x SRS resources or a subset thereof. The associated antenna ports for SRS may be all ‘y’ of the antenna ports for SRS or a subset thereof. It should be understood that the terms ‘antenna ports for SRS’, and ‘SRS antenna ports’ may be used interchangeably, to describe antenna ports (or a single antenna) that are used for SRS transmission.

[0175] In some examples, the UE antenna ports for receiving the CSI-RS configured for CSI reporting may be the same as the UE antenna ports for transmitting SRS from the selected antenna ports from the associated SRS resources. The SRS antenna ports associated with the CSI acquisition are split in two subsets: a first subset of antenna ports (SRS antenna ports) associated with PDSCH layers determined by SRS-based UL channel acquisition, and a second subset of antenna ports (SRS antenna ports) associated with PDSCH layers determined by CSI reporting. The UE is configured to determine precoding matrix information (e.g., PMI, Rl, CQI and LI) corresponding to the layers associated with the second subset ofantenna ports. This may be under the assumption that the Tx antennas associated with the first subset are not used in the PDSCH reception of the reported layers. Stated differently, in this example, it may be assumed that the antenna ports in the first and second subsets do not overlap.

[0176] An example feedback scheme for determining / selecting antenna ports to be used for SRS is depicted in FIG. 9.

[0177] FIG. 9 shows a schematic representation of signalling between a network entity and a user equipment for the selection of antenna ports to be used for SRS at the user equipment.

[0178] At S901 , the UE transmits SRS towards the gNB. The UE perform the SRS transmission with a defined antenna port order. The antenna port order may have been previously defined or fixed (i.e., known by the gNB). The UE may transmit the SRS using all antenna ports of the UE. In the example of FIG. 9, the UE has four antenna ports. The port order (or antenna port order) is related to a mapping between physical antenna and antenna ports. For example, if physical antennas of a UE have indexes 1 , 2, 3, 4, the antenna ports could be mapped (arbitrarily) to these physical antennas (with a different indexing), e.g., 1 ->3, 2->1 , 3->4, 4->1. The mapping could change, e.g., due to phone rotation or any other type of manipulation, which triggers a re-mapping. Depending on how fast the physical-to-logical mapping changes it might be suitable to update the information about an order of the antenna ports with respect to physical antennas to ensure that gNB correctly indicates the selected antennas for the SRS subset.

[0179] At S903, the gNB receives the SRS from the UE. The gNB performs measurements on the SRS that have been received. Based on the measurements, the gNB is able to determine the antenna port of the UE associated with respective SRS / SRS measurements (as the port order has been defined, or is fixed).

[0180] In this manner, the (radio) channel between the UE and the gNB is sounded by a set of known SRS ports with an identification of a mapping of logical (i.e., antenna ports) to physical antenna in the UE. This is used by the gNB to identify the antenna ports to be selected as valid SRS antenna ports for UL CSI acquisition. The mapping may be implicit / explicit. Alternatively, the mapping may be previously agreed between the UE and gNB. Alternatively, the mapping may be based on identification signaling between the UE and gNB.

[0181] At S905, the gNB determines whether each of the antenna ports of the UE are suitable for SRS transmission, based on the measurements. The gNB may compare the SRS measurements associated with each of the four antenna ports with a threshold. Based on the comparison with the threshold, each antenna port of the UE may be selected for SRS (e.g., measurement above the threshold = selectable for SRS). The threshold may be associatedwith a quality condition for SRS based measurements, or a minimum power level for SRS based measurements (e.g., a reference signal receive quality (RSRQ) value threshold).

[0182] In some examples, a pre-selection threshold is also defined (or any other suitable name for the pre-selection threshold). The pre-selection threshold may be a power value. The preselection threshold (e.g., an RSRP value) may be used to determine a group or a maximum number of UE antenna ports that may be used (before the initial comparison to the threshold). Stated differently, there may be an additional threshold (i.e., the pre-selection threshold) which is used to pre-select antenna ports based on e.g., RSRP, so the potential selection of UE antenna ports may be narrowed down. Moreover, the threshold (e.g., the SRS threshold) may be tuned / configured based on the pre-selection threshold.

[0183] At S907, based on the determining in S905, the gNB transmits an indication, to the UE, of a subset of antenna ports of the UE to be used for SRS. For example, the gNB may provide a bitmap which indicates the subset of antenna ports. In this example, the bitmap = [0 1 0 1], wherein T means (valid) SRS antenna port, and ‘0’ means other or complementary antenna port (i.e., not for SRS).

[0184] In this manner, the indication from the gNB allows the UE to form two subsets of antenna ports at the UE. These include a first subset 909 of antenna ports which include antenna ports for SRS, and a second subset 911 of antenna ports which include complementary antenna ports (not for SRS). The complementary antenna ports in the second subset 911 may be utilised for CSI-RS. This is described in more detail below, alongside FIG. 10.

[0185] FIG. 10 shows an example signalling and operations diagram for a UE and a network entity for hybrid UL / DL CSI acquisition. In this example, the network entity is a gNB.

[0186] In order to enable hybrid UL / DL CSI acquisition at the gNB, the UE should have the capability to both transmit SRS using at least one of the antenna ports of the UE, and transmit a CSI report that is based on measurements of RSs on at least one of the antenna ports of the UE. This capability is referred to as hybrid partial CSI reporting (HP-CSIR). It should be understood that the terminology of HP-CSIR is an example only, and any suitable terminology may be used.

[0187] At S1001 , the gNB transmits (or sends) a request for capabilities of the UE related to HP-CSIR.

[0188] At S1002, the UE sends, to the gNB, an indication of capabilities of the UE related to HP-CSIR. In this example, it is assumed that the UE is capable of HP-CSIR. The UE may also send at least one of: an initial mapping between physical antenna and antenna ports at theUE, identifications of each of the antenna ports of the UE, or an indication of a port order. The port order may be fixed or predetermined.

[0189] The gNB may set a pre-selection threshold (e.g., an RSRP value threshold) which may be used to determine a group, or maximum number of UE antenna ports that might be used for SRS and CSI-RS (i.e. , pre-selected before selection for SRS). Stated differently, the preselection threshold is used to pre-filter / pre-select UE antenna ports that may not participate in the SRS and CSI-RS measurements. The total number of antenna ports for the hybrid UL / DL CSI may be less than the total number of UE antenna ports.

[0190] At S1003, the UE transmits SRS. The UE may use all of the antenna ports of the UE to transmit the SRS. In other examples, the UE uses fewer than all of the antenna ports, based on a pre-selecting of UE antenna ports using the pre-selection threshold.

[0191] At S1004, the gNB receives, from the UE, the SRS. The gNB performs measurements on the SRS, wherein the measurements are used to determine which antenna ports of the UE are suitable for SRS. Antenna ports of the UE which are suitable for SRS may be determined by comparing respective SRS measurements to a threshold. The threshold may be associated with a (minimum) quality condition for SRS, or a minimum power value for SRS. The antenna ports of the UE which are determined (suitable) for SRS, are grouped into a first subset of antenna ports of the UE.

[0192] At S1005, the gNB transmits, towards all antenna ports of the UE, reference signals (RSs) (or CSI-RSs).

[0193] At S1006, the UE receives the RSs and performs measurements on the RSs. The UE receives the RSs using all antenna ports of the UE. The UE generates a first CSI report based on the measurements. In this manner, the first CSI report is relevant to all antenna ports of the UE.

[0194] The first CSI report may be provided from the UE to the gNB with some information based, for example, on power related metrics from the measurements by the receiving UE antenna ports. Additionally, the first CSE report may also contain a traditional CSI report, e.g., PMI, CQI, Rl, previously pre-configured (e.g. by default).

[0195] At S1007, the gNB receives the first CSI report (also referred to as the ‘initial CSI report’) from the UE. Based on the first CSI report, the gNB determines whether the antenna ports (that are not selected for SRS) are suitable for HP-CSIR reporting (i.e., would be suitable for receiving CSI-RS). The antenna ports of the UE that are not selected for SRS may be termed ‘complementary’ antenna ports.

[0196] In this example, it is assumed that all of the antenna ports of the UE are suitable for either SRS or CSI-RS. For example, if the UE has 8 antenna ports, then 5 antenna ports may be suitable for SRS and the remaining 3 antenna ports are suitable for CSI-RS.

[0197] At S1008, based on the received information from the UE in S1003 and S1006, the gNB determines a configuration for hybrid UL / DL CSI acquisition. The gNB determines a first subset of antenna ports of the UE, wherein the first subset is for SRS transmission. The gNB determines a second subset of antenna ports of the UE, wherein the second subset is for receiving CSI-RS. In some examples, the antenna ports in the second subset are all different to the antenna ports in the first subset. In other examples, there may be overlapping between subsets. In some examples, all of the antenna ports of the UE are included in the second subset, to be used for receiving CSI-RS.

[0198] The configuration for hybrid UL / DL CSI acquisition may also comprise information related to a CSI codebook for the UE. In the context of CSI-RS, the information related to the CSI codebook comprises a number of matrices that may be selected as precoding matrices or matrices that allow representing the precoding matrices by combinations of such matrices. By selecting the precoding matrix information from the CSI codebook, it is possible to assign precoding weights to the antenna ports and beamform the MIMO transmission, for example, for PDSCH.

[0199] Based on whether the UE is to use explicit channel based CSI reporting, or precoding matrix based CSI reporting, the gNB also configures how the UE shall provide CSI feedback. In some examples, the configuration includes an explicit channel based CSI reporting configuration for the UE. In other examples, the configuration includes a precoding matrix based CSI reporting configuration for the UE.

[0200] In some examples, the configuration (for hybrid UL / DL CSI acquisition) comprises an indication for the UE to use explicit channel based CSI reporting, or precoding matrix based CSI reporting.

[0201] At S1009, the gNB transmits, to the UE, the configuration for hybrid UL / DL CSI acquisition. The configuration includes information related to the first subset of antenna ports at the UE, and the second subset of antenna ports at the UE. The first subset and the second subset are comprised within a set of antenna ports at the UE.

[0202] At S1010, the UE transmits SRS using the antenna ports in the first subset of antenna ports.

[0203] At S1011 , the gNB transmits RSs for DL CSI. The RSs are associated with second subset of antenna ports. Stated differently, the RSs are to be received by the second subsetof antenna ports. The second subset of antenna ports may comprise all antenna ports of the UE, or fewer than all of the antenna ports of the UE.

[0204] At S1012, the gNB receives, from the UE, the SRS. The gNB measures the received SRS, in the UL, to determine CSI for at least part of the (radio) channel between the UE and the gNB.

[0205] At S1013, the UE receives, from the gNB, the RSs. The UE uses the second subset of antenna ports to receive the RSs. The UE generates a second CSI report (also referred to as simply ‘the CSI report’, when the ‘first CSI report’ is referred to as the ‘initial CSI report’), wherein the second CSI report is based on the measurements in the second subset of antenna ports that received the RSs.

[0206] In some examples, the second CSI report comprises information about the channel (herein referred to as ‘channel information’). The channel information is related to the channel between the UE and the gNB. The channel information is determined, by the UE, based on the measurements. Channel information may be comprised in the second CSI report when the UE is configured for explicit channel based CSI reporting.

[0207] In some examples, the second CSI report comprises information about a precoding matrix (herein referred to as ‘precoding matrix information’). The precoding matrix information is determined, by the UE, based on the measurements. Precoding matrix information may be comprised in the second CSI report when the UE is configured for precoding matrix based CSI reporting. Examples of precoding matrix information comprises at least one of: PMI (also referred to as an index for a precoding matrix), CQI, Rl, LI.

[0208] In some examples, the UE receives, from the gNB, an indication of which MIMO layer(s) of the channel the gNB has already determined CSI for (based on the UL SRS). For example, the indication may comprise a rank indication. The generation of the second CSI report may be based on the indication (e.g., the rank indication). In this manner, the UE receives the indication from the network specifying the layers already recovered in UL (i.e. rank measured during UL SRS), Based on the indication, the UE reports information about the remaining MIMO layers of the channel.

[0209] In this manner, in some examples, the second CSI report is based on at least one of: the number of antenna ports (in the second subset), or the (rank) indication related to the UL SRS.

[0210] At S1014, the UE transmits, to the gNB, the second CSI report.

[0211] At S1015, the gNB determines CSI for the channel based on: the received SRS (in the UL), and the information in the second CSI report (related to the DL). In this manner, aconsolidate CSI for the channel is obtained by combining the LIL / DL. The determining of the (consolidate) CSI may comprise performing a channel information re-assembling (also referred to as a channel reconstruction). For example, when the second CSI report is associated with explicit channel based CSI, the gNB may perform an LIL / DL phase offset compensation, followed by a channel coefficient re-normalization. In another example, then the second CSI report is associated with precoding matrices based CSI, the gNB may perform a layer re-orthogonalization.

[0212] At S1016, the gNB transmits, to the UE, at least one block of data in a downlink transmission based on the determined CSI (in S1015). Stated differently, the downlink transmission is beamformed, to the UE, based on the received SRS (in the UL), and the information in the second CSI report (related to the DL). The downlink transmission may be a PDSCH transmission. A block of data may be, for example, a transport block (TB), or any other type of data.

[0213] In some examples, the downlink transmission is a single downlink transmission (e.g., single PDSCH transmission), that is transmitted towards all antenna ports of the UE. In some examples, the downlink transmission comprises: a first downlink transmission, and a second downlink transmission. A first block of data may be transmitted in the first downlink transmission. A second block of data may be transmitted in the second downlink transmission. This may be referred to as a first instance of a DL transmission and a second instance of the DL transmission. The first downlink transmission is transmitted on a first number of MIMO layers of the channel. The first downlink transmission is associated with CSI obtained from the transmitting of the SRS. The second downlink transmission is transmitted on a second number of MIMO layers of the channel. The second downlink transmission is associated with CSI obtained from the second CSI report. The first downlink transmission is transmitted, by the gNB, for the first subset of antenna ports of the UE. The second downlink transmission is transmitted, by the gNB, for the second subset of antenna ports of the UE. The first number of MIMO layers and the second number of MIMO layers may, combined, make up all of the MIMO layers of the channel (e.g., the channel has 6 MIMO layers, wherein the first number is 3 layers and the second number if 3 layers).

[0214] In some examples, the same data (e.g., the same content and same amount of data) is transmitted to the UE irrespective of whether a single DL TX, or two (separate) DL TXs, carries the data for the UE. Stated differently, for data that is to be transmitted to the UE, the data may be transmitted in a single DL TX, or split into two DL TXs.

[0215] It should be understood that the ordering of signalling and operations in FIG. 10 is given as an example only. In other examples, one or more of the steps may be performed ina different order. In some examples, one or more of the steps may not be performed (i.e., left out).

[0216] In some examples, when explicit channel based CSI reporting is to be used by the UE, the antenna ports selection may be indicated with a bitmap in the configuration. The bitmap may indicate (e.g., with a T) the antenna ports that are selected for SRS. The UE may understand that remaining (or complementary) antenna ports (i.e. those not indicated) may be used for DL CSI acquisition. An indication using the bitmap may also be used when the UE is to report according to precoding matrix based CSI when separate PDSCH instances are being transmitted to different subsets of UE antenna ports.

[0217] In some examples, when precoding matrix based CSI reporting is being used by the UE, and a single PDSCH instance is transmitted to all UE antenna ports, up to all UE antenna ports may be used for CSI-RS reception. In this case, the UE may be provided with, by the gNB, knowledge about a number of MIMO layers that were recovered / determined by the gNB in UL (with the SRS). Therefore, the gNB may provide, to the UE, a measured rank indication during UL measurements. In addition, a linkage between the configured CSI-RS resources and the configured SRS resources may be also provided. The SRS configuration may contain a link to the associated CSI-RS resources and / or the CSI-RS configuration may contain a link to the associated SRS resource(s).

[0218] As described above in FIG. 10, in S1003 to S1008, the hybrid UL / DL CSI acquisition is configured based on measurements associated with the UE (from SRS transmitted by the UE, and CSI-RS received by the UE). These measurements may change over time due to, for example, varying network conditions, or UE mobility. Based on these changes, there may be a re-configuration, as depicted in FIG. 11.

[0219] FIG. 11 shows an example flow diagram for a re-configuring of a hybrid UL / DL CSI acquisition scheme.

[0220] As described above, alongside FIG. 10, the HP-CSIR feature is a dynamic, and takes into account the measurements observed with the selected SRS ports and the complementary information obtained from the DL CSI report. For that reason, S1003 to S1008 of FIG. 10 may be periodically repeated. The period may be a long-term time window (e.g., tens or hundreds of milliseconds), to verify the status of the UE antenna ports for SRS transmission as well as for CSI-RS reception.

[0221] At S1101 , at time 0 (tO), there is a determination (by a gNB) of which antenna ports of the UE should be used for SRS transmission (i.e., for UL), and which antenna ports of the UE should be used for CSI-RS reception (i.e., for the DL). CSI-RS measurements 1151 and SRSmeasurements 1153 are used as input to make the determination in S1101. This is similar to S1003 to S1007 in FIG. 10.

[0222] At S1103, at t1 , additional CSI-RS measurements and SRS measurements may be performed, and then there is a determination (by the gNB) of whether the additional CSI-RS measurements and / or SRS measurements have changed, compared the CSI-RS measurements 1151 and SRS measurements 1153

[0223] At 1105, at t2, when the gNB determines that there has been a change in at least one of the CSI-RS measurements and the SRS measurements, then an HP-CSIR re-configuration is triggered. This is similar to a repeating of S1008 in FIG. 10.

[0224] Changes in the measurements may appear due to UE mobility and / or the dynamic network environment. A gradual and periodic reconfiguration may be suitable to ensure that the optimum / most efficient subsets of antenna ports are configured at the UE. Depending on the observed changes, S1009-S1015 in FIG. 10 may also be triggered again in order to reconfigure the SRS, CSI-RS resources and / or the DL CSI codebook.

[0225] In some examples, for the hybrid UL / DL CSI acquisition, a UE may provide indications, to a network entity (e.g., gNB), of antenna ports of the UE that are suitable for receiving CSI- RS, such that they could be selected for DL channel information acquisition by the gNB. For example, the UE may indicate, per antenna port, power measurements above a threshold while receiving CSI-RS, or a bitmap indicating one or more antenna ports.

[0226] In some examples, when the UE is providing CSI reports according to precoding matrix based CSI reporting, the UE receives an indication from the gNB specifying the layers that have been determined by the gNB based on the SRS received in the UL (e.g., rank measured during UL SRS). Based on the indication, the UE reports the remaining layers if the rank indicators show that other additional layers might also be recovered and reported based on a maximum attainable rank of the channel considering all UE Rx antennas.

[0227] In some examples, the UE may be informed of a link (or association) between the configured CSI-RS resources and the configured SRS resources, by the gNB. The SRS configuration may comprise a link to the associated CSI-RS resources and / or the CSI-RS configuration may comprise a link to the associated SRS resource(s).

[0228] In some examples, at the gNB, during a sounding for antenna port classification, the gNB may provide indications of (valid) SRS antenna ports that could be selected for UL channel information acquisition (e.g. by providing a bitmap indicating antenna ports). The gNB may also select also (valid) CSI-RS antenna ports at the UE and / or indicate the measured rank from UL channel acquisition to restrict the DL CSI acquisition.

[0229] In some examples, the gNB provides a CSI codebook configuration based on previously obtained measurements in UL and DL CSI during antenna port classification. This utilises a message including valid ports for LIL / DL and other corresponding parametrization.

[0230] One or more of the examples above have the advantage that CSI acquisition about a radio channel between a UE and gNB is improved. By determining / selecting which antenna ports of the UE will be suitable for transmitting SRS reduces the unnecessary transmission of SRS toward the gNB (compared to transmitting SRS on all antenna ports). This will reduce the UE energy consumption, and reduce potential congestion / interference for signals being transmitted / received. The selective SRS transmission may relax the issues surrounding reference / pilot contamination, and necessary coordination in the UL transmission for resource allocation for UEs intending to transmit SRS.

[0231] The partial recovery of CSI for the radio channel (between UE and gNB) with UL SRS leads to a reduction in the number of resources required for DL CSI report transmission, and thus implying a reduced bit overhead. There is a reduced bit overhead as there is a smaller amount of DL CSI, which is proportional to the number of Rx UE antenna ports (e.g., in the case of explicit channel based CSI). CSI compression schemes such as rule based compression, e.g. beam and / or delay domain compression, but also AI / ML based compression may be considered. Alternatively, the DL CSI could be also reduced by recovering a lower number of precoding matrix layers, orthogonal and complementary, to the already recovered layers from UL SRS.

[0232] FIG. 12 shows an example method flow performed by an apparatus. The apparatus may be a UE, or other communication device. The apparatus may comprise one or more means for performing the following method.

[0233] In S1201 , the method comprises: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment.

[0234] In S1203, the method comprises: transmitting sounding reference signals using the first subset of antenna ports.

[0235] In S1205, the method comprises: performing measurements on reference signals received from the network entity using the second subset of antenna ports.

[0236] In S1207, the method comprises: transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report is based on the measurements.

[0237] In S1209, the method comprises: receiving, from the network entity, at least one block of data in at least one downlink transmission, using at least one of: the first subset of antenna ports, or the second subset of antenna ports.

[0238] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 12 and are performed by the apparatus. In some examples, one or more of the method steps of FIG. 12 detailed above may not be performed, or may be performed in a different order.

[0239] FIG. 13 shows an example method flow performed by an apparatus. The apparatus may be a network entity. For example, a base station, gNB, transmission reception point, or other network node. The apparatus may comprise one or more means for performing the following method.

[0240] In S1301 , the method comprises: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment.

[0241] In S1303, the method comprises: receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports.

[0242] In S1305, the method comprises: transmitting, to the user equipment, reference signals.

[0243] In S1307, the method comprises: receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises information related to measurements performed on the reference signals.

[0244] In S1309, the method comprises: transmitting, to the user equipment, at least one block of data in at least one downlink transmission that is beamformed based on the sounding reference signals received at the network entity and the information comprised in the CSI report.

[0245] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 13 and are performed by the apparatus. In some examples, one or more of the method steps of FIG. 13 detailed above may not be performed, or may be performed in a different order.

[0246] FIG. 14 shows an example method flow performed by an apparatus. The apparatus may be a UE, or other communication device. The apparatus may comprise one or more means for performing the following method.

[0247] In S1401 , the method comprises: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment.

[0248] In S1403, the method comprises: transmitting sounding reference signals using the first subset of antenna ports.

[0249] In S1405, the method comprises: performing measurements on reference signals received from the network entity using the second subset of antenna ports.

[0250] In S1407, the method comprises: transmitting, to the network entity, a channel state information, CSI, report according to explicit channel based CSI reporting, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity, wherein the channel information is determined based on the measurements.

[0251] In S1409, the method comprises: receiving, from the network entity, at least one block of data in a downlink transmission.

[0252] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 14 and are performed by the apparatus. In some examples, one or more of the method steps of FIG. 14 detailed above may not be performed, or may be performed in a different order.

[0253] FIG. 15 shows an example method flow performed by an apparatus. The apparatus may be a network entity. For example, a base station, gNB, transmission reception point, or other network node. The apparatus may comprise one or more means for performing the following method.

[0254] In S1501 , the method comprises: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment.

[0255] In S1501 , the method comprises: receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports.

[0256] In S1501 , the method comprises: transmitting, to the user equipment, reference signals.

[0257] In S1501 , the method comprises: receiving, from the user equipment, a channel state information, CSI, report, wherein the CSI report comprises channel information, the channel information related to a channel between the user equipment and the network entity.

[0258] In S1501 , the method comprises: transmitting, to the user equipment, a block of data in a downlink transmission that is beamformed based on the sounding reference signals received at the network entity, and the channel information comprised in the CSI report.

[0259] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 15 and are performed by the apparatus. In some examples, one or more of the method steps of FIG. 15 detailed above may not be performed, or may be performed in a different order.

[0260] FIG. 16 shows an example method flow performed by an apparatus. The apparatus may be a UE, or other communication device. The apparatus may comprise one or more means for performing the following method.

[0261] In S1601 , the method comprises: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment.

[0262] In S1603, the method comprises: transmitting sounding reference signals using the first subset of antenna ports.

[0263] In S1605, the method comprises: performing measurements on reference signals received from the network entity using the second subset of antenna ports.

[0264] In S1607, the method comprises: transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements.

[0265] In S1609, the method comprises: receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of Ml MO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports.

[0266] In S1611 , the method comprises: receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

[0267] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 16 and are performed by the apparatus. In some examples, one or more of the method steps of FIG. 16 detailed above may not be performed, or may be performed in a different order.

[0268] FIG. 17 shows an example method flow performed by an apparatus. The apparatus may be a network entity. For example, a base station, gNB, transmission reception point, or other network node. The apparatus may comprise one or more means for performing the following method.

[0269] In S1701 , the method comprises: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment.

[0270] In S1703, the method comprises: receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports.

[0271] In S1705, the method comprises: transmitting, to the user equipment, reference signals.

[0272] In S1707, the method comprises: receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information.

[0273] In S1709, the method comprises: transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment and the network entity.

[0274] In S1711 , the method comprises: transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix information comprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

[0275] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 17 and are performed by the apparatus. In some examples, one or more of the method steps of FIG. 17 detailed above may not be performed, or may be performed in a different order.

[0276] FIG. 18 shows a schematic representation of an apparatus. FIG. 18 shows, by way of example, a block diagram of an apparatus 10. The apparatus 10 comprises, for example, at least one processor 12 and at least one memory 14 storing instructions 15 that, when executed by the at least one processor, cause the apparatus 10 at least to perform the method or methods as disclosed herein, and any of the embodiments thereof. In an example, the at least one memory and the instructions (e.g. a computer program code, software), are configured, with the at least one processor, to cause the apparatus 10 to perform the method or methods as disclosed herein, and any of the embodiments thereof.

[0277] A processor 12 may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with example embodiments described herein. As used in this application, 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 user equipment, 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 requires software (e.g., firmware) for operation, but the software maynot be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, 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.

[0278] The memory 14 may be implemented using any suitable data storage technology. The memory may comprise a database for storing data. The memory 14 may be at least in part external to apparatus 10 but accessible to apparatus 10.

[0279] The instructions 15 may be comprised in a computer readable medium or a non- transitory computer readable medium. A term non-transitory, as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. random access memory, RAM, vs. read only memory, ROM).

[0280] For example, the apparatus 10 is a communication device (or terminal device), e.g., such as one of the UEs in FIGS. 7 to 10. As another example, the apparatus is comprised in such a communication device, e.g. as a chipset configured to control the communication device. The apparatus 10 may be caused or configured to perform at least the method of any of FIGS. 12, 14, or 16, and / or any one or more of the embodiments described.

[0281] As another example, the apparatus 10 is a network entity (or network node), e.g. such as one of the network entities in of FIGS. 7 to 10. In another embodiment, the apparatus is comprised in such a network entity, e.g. as a chipset configured to control the network node. The apparatus 10 may be caused or configured to perform at least the method of any of FIGS. 13, 15 or 17, and / or any one or more of the embodiments described.

[0282] The apparatus 10 comprises a radio interface 16. The radio interface 16 may provide the apparatus 10 with communication capabilities. The radio interface 16 may comprise a receiver configured to receive information in accordance with at least one cellular or non- cellular standard. The radio interface 16 may comprise a transmitter configured to transmit information in accordance with at least one cellular or non-cellular standard. The receiver may comprise more than one receiver. The transmitter may comprise more than one transmitter. The radio interface 16 may comprise a transceiver configured to receive and transmit information in accordance with at least one cellular or non-cellular standard. The transceiver may comprise more than one transceiver.

[0283] The apparatus 10 may comprise a user interface 18 comprising, for example, at least one of a keypad, a microphone, a touch display, a display, a speaker, etc. The user interface 18 may be used to control the apparatus by the user. The user interface 18 may be external to the apparatus 10. For example, the apparatus 10 may be connected to another device, such as a computer, either via wireless or wired connection, and the apparatus 10 is controlled by the user via the computer.

[0284] In an embodiment, at least some of the processes described herein may be carried out by an apparatus comprising means for carrying out at least some of the described processes. Means for performing method steps as disclosed herein may include software and / or hardware components of the apparatus 10. For example, the at least one processor 12, the memory 14, and the computer program code form means for carrying out the method or methods as disclosed herein, and any of the embodiments thereof. As used herein the term “means” is to be construed in singular form, i.e. referring to a single element, or in plural form, i.e. referring to a combination of single elements. Therefore, terminology “means for [performing A, B, C]”, is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Further, terminology “means for performing A, means for performing B, means for performing C” is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C.lt is noted that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

[0285] The examples may thus vary within the scope of the attached claims. In general, some embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects 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 embodiments are not limited thereto. While various embodiments 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 nonlimiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0286] The examples may be implemented by computer software stored in a memory and executable by at least one data processor of the involved entities or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that anyprocedures 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 for example DVD and the data variants thereof, CD.

[0287] The term “non-transitory”, as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. RAM vs ROM).

[0288] 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 of the elements.

[0289] 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 include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

[0290] As used herein, the terms “means for”, “means for performing operations including”, “means configured to perform operations including”, or “means configured to perform” (or similar) may be any means that are suitable for performing the feature(s). The “means” may be configured to perform one or more of the functions and / or method steps previously described. For example, the “means” may include one or more of: at least one processor, at least one memory, transceiver circuitry, antenna circuitry, etc. It should be understood that these are provided as non-limiting examples.

[0291] Alternatively, or additionally some examples may be implemented using circuitry. The circuitry may be configured to perform one or more of the functions and / or method steps previously described. That circuitry may be provided in the base station and / or in the communications device.

[0292] As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analogue and / or digital circuitry); (b) combinations of hardware circuits and software, such as: (i) a combination of analogue 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 the communications device or base station to perform the various functions previously described; and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0293] This definition of circuitry applies to uses of the term “means” in this application, including in any claims. As a further example, as used in this application, 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 integrated device. 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 a server, a cellular network device, or other computing or network device.

[0294] The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of some embodiments. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings will still fall within the scope as defined in the appended claims.

Claims

CLAIMS1. A user equipment comprising: means for receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; means for transmitting sounding reference signals using the first subset of antenna ports; means for performing measurements on reference signals received from the network entity using the second subset of antenna ports; means for transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements; means for receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of MIMO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports; and means for receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

2. The user equipment according to claim 1 , wherein the information further comprises an indication to provide CSI reports according to a precoding matrix based CSI reporting procedure.

3. The user equipment according to claim 1 or claim 2, wherein the user equipment further comprises: means for generating the CSI report based on the measurements, wherein the CSI report comprises the precoding matrix information.

4. The user equipment according to any of claims 1 to 3, wherein the precoding matrix information comprises at least one of: a precoding matrix indicator, a channel quality indicator, a rank indicator, or a layer indicator.

5. The user equipment according to any of claims 1 to 4, further comprising:means for transmitting, to the network entity, initial sounding reference signals using the antenna ports in the set of antenna ports at the user equipment.

6. The user equipment according to any of claims 1 to 5, further comprising: means for performing initial measurements on reference signals received from the network entity using the antenna ports in the set of antenna ports at the user equipment; means for transmitting, to the network entity, an initial CSI report, wherein the initial CSI report is based on the initial measurements.

7. The user equipment according to any of claims 1 to 6, further comprising: means for, based on a received request for capabilities of the user equipment, transmitting, to the network entity, an indication that the user equipment supports a feature related to hybrid partial CSI reporting.

8. The user equipment according to any of claims 1 to 7, further comprising: means for, based on a received request for capabilities of the user equipment, transmitting, to the network entity, information related to antenna ports of the user equipment, the information including a predetermined order associated with the antenna ports.

9. A network entity comprising: means for transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; means for receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; means for transmitting, to the user equipment, reference signals; means for receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information; means for transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment and the network entity; and means for transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix informationcomprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

10. The network entity according to claim 9, wherein the precoding matrix information comprises at least one of: a precoding matrix indicator, a channel quality indicator, a rank indicator, or a layer indicator.11 . The network entity according to claim 9 or claim 10, wherein the network entity further comprises: means for receiving, from the user equipment, an initial sounding reference signal associated with each of the antenna ports in the set of antenna ports at the user equipment; means for determining, for each of the antenna ports of the user equipment, whether to include the respective antenna port in the first subset of antenna ports based on measurements performed on the respective initial sound reference signal.

12. The network entity according to any of claims 9 to 11 , wherein the means for determining whether to include the respective antenna port in the first subset of antenna ports comprises: means for determining, for each of the antenna ports of the user equipment, whether to include the respective antenna port in the first subset of antenna ports based on a comparison between measurements performed on the respective initial sound reference signal and a threshold.

13. The network entity according to claim 12, wherein the network entity further comprises: means for transmitting, to the user equipment, initial reference signals; means for receiving, from the user equipment, an initial CSI report, wherein the initial CSI report is based on initial measurements performing using the antenna ports in the set of antenna ports at the user equipment; means for, based on the initial CSI report, determining whether remaining antenna ports of the user equipment that have not been determined for the first subset of antenna ports are suitable for CSI reporting; and means for, based on the determining, including at least one of the remaining antenna ports of the user equipment in the second subset of antenna ports.

14. The network entity according to any of claims 9 to 13, wherein the network entity further comprises:means for determining first CSI for a channel between the network entity and the user equipment based on the sounding reference signals received by the network entity, and second CSI for the channel based on the information in the CSI report, wherein the first downlink transmission is based on the first CSI and the second downlink transmission is based on the second CSI.

15. The network entity according to any of claims 9 to 14, further comprising: means for transmitting, to the user equipment, a request for capabilities of the user equipment related to hybrid partial channel state information reporting; and means for receiving, from the user equipment, an indication that the user equipment supports a feature related to hybrid partial CSI reporting.

16. The network entity according to any of claims 9 to 15, further comprising: means for transmitting, to the user equipment, a request for capabilities of the user equipment related to hybrid partial channel state information reporting; and means for receiving, from the user equipment, information related to antenna ports of the user equipment, the information including a predetermined order associated with a mapping between the antenna ports and physical antennas of the user equipment.

17. The network entity according to any of claims 9 to 16, wherein the network entity further comprises: means for transmitting, to the user equipment, an indication to provide channel state information reports according to precoding matrix based CSI reporting.

18. A method performed by a user equipment, the method comprising: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports; transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements; receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of MIMO layers of achannel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports; and receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

19. A method performed by a network entity, the method comprising: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information; transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment and the network entity; and transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix information comprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

20. A computer program comprising instructions, which when executed by a user equipment, cause the user equipment to perform at least the following: receiving, from a network entity, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; transmitting sounding reference signals using the first subset of antenna ports; performing measurements on reference signals received from the network entity using the second subset of antenna ports;transmitting, to the network entity, a channel state information, CSI, report, wherein the CSI report comprises precoding matrix information, wherein the precoding matrix information is determined based on the measurements; receiving, from the network entity, a first block of data in a first downlink transmission, wherein the first downlink transmission is received on a first number of MIMO layers of a channel between the user equipment and the network entity, wherein the first block of data is received using the first subset of antenna ports; and receiving, from the network entity, a second block of data in a second downlink transmission, wherein the second downlink transmission is received on a second number of MIMO layers of the channel, wherein the second block of data is received using the second subset of antenna ports.

21. A computer program comprising instructions, which when executed by a network entity, cause the network entity to perform at least the following: transmitting, to a user equipment, information related to a first subset of antenna ports at the user equipment, and a second subset of antenna ports at the user equipment, wherein the first subset and the second subset are comprised within a set of antenna ports at the user equipment; receiving, from the user equipment, sounding reference signals associated with the first subset of antenna ports; transmitting, to the user equipment, reference signals; receiving, from the user equipment, a CSI report, wherein the CSI report comprises precoding matrix information; transmitting, to the user equipment, a first block of data in a first downlink transmission that is beamformed based on the sounding reference signals received at the network entity, wherein the first downlink transmission is transmitted on a first number of MIMO layers of a channel between the user equipment and the network entity; and transmitting, to the user equipment, a second block of data in a second downlink transmission that is beamformed based on the precoding matrix information comprised in the CSI report, wherein the second downlink transmission is transmitted on a second number of MIMO layers of the channel.

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