Devices and methods for generating channel state information (CSI) in wireless communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The present invention relates, in general, to wireless communications and, more specifically, to devices and methods for generating channel state information (CSI). According to the proposed method, a plurality of channel state information reference signals (CSI-RSs) is transmitted from a base station of a wireless communication system, wherein the plurality of CSI-RSs comprises two or more CSI-RS sets; and a user equipment in the wireless communication system selects a predefined number of CSI-RSs from CSI-RS sets received from the base station, and generates CSI based on the selected CSI-RSs, wherein the CSI comprises, for each of the selected CSI-RSs, respective parameters, including an identifier of the CSI-RS.

Description

DEVICES AND METHODS FOR GENERATING CHANNEL STATE INFORMATION (CSI) IN WIRELESS COMMUNICATION SYSTEM

[0001] The present invention relates, in general, to wireless communications and, more specifically, to devices and methods for generating and transmitting channel state information (CSI) in a wireless communication system.

[0002] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in “Sub 6GHz” bands such as 3.5GHz, but also in “Above 6GHz” bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] Nowadays more and more active deployment of 5th Generation (5G) New Radio (NR) networks takes place, whose advantages and capabilities are broadly known.

[0009] Base stations (BSs) in a 5G NR system use massive antenna arrays containing multiple transceiver antenna elements, which enable efficient implementation of multiple-input multiple-output (MIMO) technology, where a number of simultaneously transmitted spatial MIMO layers are generated to transmit data (e.g. physical downlink shared channel (PDSCH)) to one or more user equipments (UEs).

[0010] Generally speaking, a digital signal is transmitted using one or more digital ports connected to antenna elements of the base station, by means of a radio frequency unit that performs the function of converting the digital signal into an analog one and vice versa. For example, for the 3.5 GHz frequency range, up to 64 digital antenna ports can be used which enable to use, in base stations, various precoding schemes. For example, the spatial multiplexing (SM) technology enables to reuse of the same frequency-time resources for DL transmission of multiple signals (MIMO layers) to one or more user equipments, and the adaptive beamforming (BF) technology enables to dynamically steer power of a transmitted signal to one or more predefined directions. Advanced modulation techniques, such as orthogonal frequency-division multiplexing (OFDM), provide efficient broadband signal transmission.

[0011] More specifically, two approaches to DL beamforming are presently known to be used in wireless communication systems: analog beamforming (A-BF) and digital beamforming (D-BF). The combined implementation of these approaches is referred to as hybrid beamforming (H-BF).

[0012] A-BF is performed in the analog part of the base station and is applied, in the time domain, to a signal which has been already generated; this approach is characterized by relatively low computational costs, but also less flexibility. D-BF is performed in the digital part of the base station and can be applied in the frequency domain as well; this approach is much more flexible than A-BF, but also more computationally expensive.

[0013] In view of the problems existing in the art, as discussed above, the basic object of the present invention is to provide a method of generating and transmitting CSI that would provide proper support of DL H-BF for next generation communication systems, while avoiding the drawbacks of the prior art outlined above.

[0014] In the context of addressing this technical object, according to the first aspect of the present invention, a method of generating CSI in a wireless communication system is provided.

[0015] The method provided herein comprises: performing, from a base station of the wireless communication system, transmission of a plurality of CSI-RSs, wherein the plurality of CSI-RSs comprises two or more CSI-RS sets; and, in a user equipment in the wireless communication system, selecting a predefined number of CSI-RSs from the CSI-RS sets received from the base station, and generating the CSI based on the selected CSI-RSs, wherein the CSI comprises, for each of the selected CSI-RSs, respective parameters, including an identifier of the CSI-RS. Said parameters preferably include, at least, a RI, a CQI, and a PMI calculated in the user equipment for a respective CSI-RS among the selected CSI-RSs, wherein said identifier is a CRI, wherein the PMI is represented in the CSI by two parameters: PMI1 and PMI2, where PMI1 relates to DFT vectors, and PMI2 relates to polarization co-phasing in the precoding matrix. According to a preferred embodiment, the method provided herein further comprises: transmitting the generated CSI from the user equipment to the base station.

[0016] According to an embodiment, the base station uses, for the transmission of the plurality of CSI-RSs, a set of spatial beams, wherein the two or more CSI-RS sets include: a first CSI-RS set transmitted by using a subset of first type beams from the set of spatial beams, and a second CSI-RS set transmitted by using a subset of second type beams from the set of spatial beams. The first type beams can be narrower beams with a higher gain which are intended for SU-MIMO, and the second type beams can be wider beams with a lower gain which are intended for MU-MIMO.

[0017] In accordance with an embodiment, a number of CSI-RSs transmitted in each of the two or more CSI-RS sets is preset in the base station individually for the CSI-RS set and signaled in advance from the base station to the user equipment.

[0018] According to one embodiment, said selecting a predefined number of CSI-RSs, generating CSI, and transmitting the CSI are performed periodically, with at least one predetermined period. Said at least one predetermined period is preconfigured in the base station and signaled in advance from the base station to the user equipment. Moreover, the base station can further use DL control signaling (preferably, a MAC message) to indicate, to the user equipment, specific CSI-RSs based on which the CSI is to be generated.

[0019] According to another embodiment, said selecting a predefined number of CSI-RSs, generating CSI, and transmitting the CSI are performed upon reception of a CSI request from the base station. The CSI request is preferably transmitted by DCI and comprises a bit field, wherein a value of the bit field is respectively selected in the base station from a plurality of bit values, wherein each value of the bit field from at least part of the plurality of bit values is an indication of at least a predefined number of CSI-RSs based on which the CSI is to be generated. Said plurality of bit values can be preconfigured in the base station and signaled in advance from the base station to the user equipment by RRC signaling. In accordance with one implementation, the predefined number of CSI-RSs can be selected over all the received CSI-RS sets e.g. based on measuring received powers of CSI-RSs. In the context of this implementation, a respective power offset can be set in the base station with respect to CSI-RSs of each of at least one of the two or more CSI-RS sets, wherein the power offset is signaled in advance from the base station to the user equipment; wherein said selecting the predefined number of CSI-RSs over all the received CSI-RS sets can comprise: respectively applying, in the user equipment, the set power offset with respect to each of the at least one CSI-RS set. According to another implementation, each value of the bit field from the at least part of the plurality of bit values is further an indication of at least one CSI-RS set from the plurality of CSI-RSs, and said selecting a predefined number of CSI-RSs can comprise: selecting the predefined number of CSI-RSs, in accordance with the value of the bit field in the CSI request, in the indicated at least one CSI-RS set (e.g. independently in each of said at least one CSI-RS set), for instance, based on measuring received powers of CSI-RSs in the indicated at least one CSI-RS set.

[0020] In accordance with a preferred embodiment, the CSI is transmitted by using UCI, wherein said parameters of the CSI are arranged in a first UCI part and a second UCI part, wherein a payload size of the first UCI part is fixed, and a payload size of the second UCI part is variable and dependent on UCI contents in the first UCI part.

[0021] According to an embodiment, said parameters of the CSI comprise parameters relating to a WB report.

[0022] In accordance with one implementation, the first UCI part comprises a sequence of sets {CRIi, RIi, wCQIi}, where i, 1≤i≤K, is an index of a selected CSI-RS which is reported in the CSI, K is the predefined number of CSI-RSs. The sets {CRIi, RIi, wCQIi} can be ordered in said sequence according to received power levels of respective CSI-RSs.

[0023] In accordance with another implementation, the first UCI part comprises: a code point which is a result of combinatorial encoding and represents a set {CRIi}, and a sequence of sets {RIi, wCQIi} ordered according to an order of CRIi‘s in the set {CRIi}, where i, 1≤i≤K, is an index of a selected CSI-RS which is reported in the CSI, K is the predefined number of CSI-RSs.

[0024] According to an embodiment, said parameters of the CSI further comprise parameters relating to a SB report.

[0025] In accordance with one implementation, the first UCI part comprises a sequence of sets {CRIi, RIi, wCQIi, sCQIi}, where i, 1≤i≤K, is an index of a selected CSI-RS which is reported in the CSI, K is the predefined number of CSI-RSs. The sets {CRIi, RIi, wCQIi, sCQIi} can be ordered in said sequence according to received power levels of respective CSI-RSs.

[0026] In accordance with another implementation, the first UCI part comprises: a code point which is a result of combinatorial coding and represents a set {CRIi}, and a sequence of sets {RIi, wCQIi, sCQIi} ordered according to an order of CRIi's in the set {CRIi}, where i, 1≤i≤K, is an index of a selected CSI-RS which is reported in the CSI, K is the predefined number of CSI-RSs.

[0027] As an option, the second UCI part can comprise a sequence of sets {wPMI1i, wPMI2i} ordered according to an ordering of {CRIi} in the first UCI part, or the second UCI part can comprise a first set {wPMI1i}, followed by a second set {wPMI2i}, wherein each of the first set and the second set is ordered according to the ordering of {CRIi} in the first UCI part.

[0028] As an option, the second UCI part can comprise a first set {wPMI1i}, followed by a second set {sPMI2i(e)}, followed by a third set {sPMI2i(o)}, wherein each of the first set, the second set, and the third set is ordered according to an ordering of {CRIi} in the first UCI part, or the second UCI part can comprise a sequence of sets {wPMI1i, sPMI2i(e), sPMI2i(o)}, wherein the sets {wPMI1i, sPMI2i(e), sPMI2i(o)} are ordered in said sequence according to the ordering of {CRIi} in the first UCI part.

[0029] According to the second aspect of the present invention, a method of generating CSI in a wireless communication system is provided.

[0030] The method provided herein comprises: in a user equipment in the wireless communication system, receiving a CSI request from a base station of the wireless communication system, the CSI request comprising an indication of at least a predefined number of CSI-RSs based on which the CSI is to be generated; performing, from the base station, transmission of a plurality of CSI-RSs, wherein the plurality of CSI-RSs comprises two or more CSI-RS sets; and, in the user equipment, selecting, based on the indication in the received CSI request, the predefined number of CSI-RSs from the CSI-RS sets received from the base station, and generating the CSI based on the selected CSI-RSs, wherein the CSI comprises, for each of the selected CSI-RSs, respective parameters, including an identifier of the CSI-RS. Said parameters preferably include, at least, a RI, a CQI, and a PMI calculated in the user equipment for a respective CSI-RS among the selected CSI-RSs, wherein said identifier is a CRI, wherein the PMI is represented in the CSI by two parameters: PMI1 and PMI2, where PMI1 relates to DFT vectors, and PMI2 relates to polarization co-phasing in the precoding matrix. According to a preferred embodiment, the method further comprises: transmitting the generated CSI from the user equipment to the base station.

[0031] In accordance with an embodiment, the base station uses, for the transmission of the plurality of CSI-RSs, a set of spatial beams, wherein the two or more CSI-RS sets include: a first CSI-RS set transmitted by using a subset of first type beams from the set of spatial beams, and a second CSI-RS set transmitted by using a subset of second type beams from the set of spatial beams. The first type beams can be narrower beams with a higher gain which are intended for SU-MIMO, and the second type beams can be wider beams with a lower gain which are intended for MU-MIMO.

[0032] According to an embodiment, a number of CSI-RSs transmitted in each of the two or more CSI-RS sets can be preset in the base station individually for the CSI-RS set and signaled in advance from the base station to the user equipment.

[0033] In accordance with a preferred embodiment, the CSI request is transmitted by DCI, and comprises a bit field, wherein a value of the bit field is respectively selected in the base station from a plurality of bit values, wherein each value of the bit field from at least part of the plurality of bit values is an indication of at least a predefined number of CSI-RSs based on which the CSI is to be generated. Said plurality of bit values can be preconfigured in the base station and signaled in advance from the base station to the user equipment by RRC signaling. In accordance with one implementation, the predefined number of CSI-RSs can be selected over all the received CSI-RS sets e.g. based on measuring received powers of CSI-RSs. In the context of this implementation, a respective power offset can be set in the base station with respect to CSI-RSs of each of at least one of the two or more CSI-RS sets, wherein the power offset is signaled in advance from the base station to the user equipment; wherein said selecting the predefined number of CSI-RSs over all the received CSI-RS sets can comprise: respectively applying, in the user equipment, the set power offset with respect to each of the at least one CSI-RS set. According to another implementation, each value of the bit field from the at least part of the plurality of bit values is further an indication of at least one CSI-RS set from the plurality of CSI-RSs, and said selecting a predefined number of CSI-RSs can comprise: selecting the predefined number of CSI-RSs, in accordance with the value of the bit field in the CSI request, in the indicated at least one CSI-RS set (e.g. independently in each of said at least one CSI-RS set), for instance, based on measuring received powers of CSI-RSs in the indicated at least one CSI-RS set.

[0034] In accordance with a preferred embodiment, the CSI is transmitted by using UCI, wherein said parameters of the CSI are arranged in a first UCI part and a second UCI part, wherein a payload size of the first UCI part is fixed, and a payload size of the second UCI part is variable and dependent on UCI contents in the first UCI part.

[0035] According to an embodiment, said parameters of the CSI comprise parameters relating to a WB report.

[0036] In accordance with one implementation, the first UCI part comprises a sequence of sets {CRIi, RIi, wCQIi}, where i, 1≤i≤K, is an index of a selected CSI-RS which is reported in the CSI, K is the predefined number of CSI-RSs. The sets {CRIi, RIi, wCQIi} can be ordered in said sequence according to received power levels of respective CSI-RSs.

[0037] In accordance with another implementation, the first UCI part comprises: a code point which is a result of combinatorial encoding and represents a set {CRIi}, and a sequence of sets {RIi, wCQIi} ordered according to an order of CRIi's in the set {CRIi}, where i, 1≤i≤K, is an index of a selected CSI-RS which is reported in the CSI, K is the predefined number of CSI-RSs.

[0038] According to an embodiment, said parameters of the CSI further comprise parameters relating to a SB report.

[0039] In accordance with one implementation, the first UCI part comprises a sequence of sets {CRIi, RIi, wCQIi, sCQIi}, where i, 1≤i≤K, is an index of a selected CSI-RS which is reported in the CSI, K is the predefined number of CSI-RSs. The sets {CRIi, RIi, wCQIi, sCQIi} can be ordered in said sequence according to received power levels of respective CSI-RSs.

[0040] In accordance with another implementation, the first UCI part comprises: a code point which is a result of combinatorial coding and represents a set {CRIi}, and a sequence of sets {RIi, wCQIi, sCQIi} ordered according to an order of CRIi's in the set {CRIi}, where i, 1≤i≤K, is an index of a selected CSI-RS which is reported in the CSI, K is the predefined number of CSI-RSs.

[0041] As an option, the second UCI part can comprise a sequence of sets {wPMI1i, wPMI2i} ordered according to an ordering of {CRIi} in the first UCI part, or the second UCI part can comprise a first set {wPMI1i}, followed by a second set {wPMI2i}, wherein each of the first set and the second set is ordered according to the ordering of {CRIi} in the first UCI part.

[0042] As an option, the second UCI part can comprise a first set {wPMI1i}, followed by a second set {sPMI2i(e)}, followed by a third set {sPMI2i(o)}, wherein each of the first set, the second set, and the third set is ordered according to an ordering of {CRIi} in the first UCI part, or the second UCI part can comprise a sequence of sets {wPMI1i, sPMI2i(e), sPMI2i(o)}, wherein the sets {wPMI1i, sPMI2i(e), sPMI2i(o)} are ordered in said sequence according to the ordering of {CRIi} in the first UCI part.

[0043] According to the third aspect of the present invention, a wireless communication system is provided, the wireless communication system comprising, at least, a base station, the base station comprising, at least: transceiving units; data processing units; and data storage units, wherein the base station is configured to communicate with a user equipment comprising, at least: transceiving units; data processing units; and data storage units. The data storage units of the base station have computer-executable codes stored therein, and the data storage units of the user equipment have computer-executable codes stored therein. The computer-executable codes, when executed by the data processing units of the base station and the user equipment, cause the method according to any embodiment of the first and second aspects of the present invention to be performed.

[0044] The technical result achieved by the present invention is in enabling to flexibly generate and report CSI in the context of DL H-BF, along with supporting transmission of multiple CSI-RS sets (in particular, by using substantially different spatial beams) to a user equipment(s), and supporting the capability of simultaneously reporting, from the user equipment to the base station by the CSI, about several CSI-RSs (in particular, about CSI-RSs from different CSI-RS sets), thereby, in turn, providing more flexible scheduling of resources for DL transmission at the base station side.

[0045] Fig. 1 - a general scheme of an embodiment of interaction between a wireless network and a user equipment to provide implementation of DL H-BF according to 5G NR;

[0046] Fig. 2 - part of the scheme in Fig. 1 that illustrates operations by which generating, transmitting, and processing of CSI is provided according to 5G NR;

[0047] Fig. 3 - an illustration of selection of the best analog beam by a user equipment based on transmitted CSI-RSs in accordance with 5G NR;

[0048] Fig. 4a, 4b - illustrative embodiments of CSI transmission in UL by means of UCI according to 5G NR;

[0049] Fig. 5 - illustrations of implementation of the base station scheduler restriction;

[0050] Fig. 6 - an illustration of scheduling resources for DL transmission to user equipments with the scheduler restriction according to 5G NR, as illustrated in Fig. 5;

[0051] Fig. 7a, 7b - an illustration of two A-BF strategies in the context of DL H-BF in accordance with 5G NR;

[0052] Fig. 8 - an illustrative diagram of a wireless communication system in which embodiments of the present invention can be implemented;

[0053] Fig. 9, 10a, 10b - illustrations of interaction between a base station and a user equipment according to an embodiment of the present invention to provide implementation of DL H-BF;

[0054] Fig. 11a, 11b, 11c, 11d - illustrations of arrangement of parameters of transmitted CSI in UCI according to embodiments of the present invention;

[0055] Fig. 12a, 12b, 12c, 12d - illustrations of arrangement of parameters of transmitted CSI in UCI according to embodiments of the present invention;

[0056] Fig. 13 - a flowchart of a method of generating CSI for DL H-BF according to the present invention.

[0057] Fig. 14 illustrates a structure of implementation a structure of a UE according to an embodiment of the disclosure.

[0058] Fig. 15 illustrates a structure of implementation a structure of a base station according to an embodiment of the disclosure.

[0059] Adaptive beamforming methods using A-BF and D-BF (i.e. H-BF) are supported in 5G NR. The general scheme of interaction between a wireless communication network (NW) and a user equipment (UE) is described below with illustrative reference to Fig. 1, where H-BF is used for DL data transmission according to 5G NR.

[0060] A base station, which is part of the NW, broadcasts SS / PBCH block resources (SSBs) in all or some of spatial beams, where SS is a synchronization signal, PBCH is a physical broadcast channel (action 1). Such broadcasting can be performed by the base station periodically. In the left part of Fig. 1, the set of possible beams is illustrated by contours; hereinafter, these beams may be referred to as ‘analog beams’ without limitation, in order to indicate for the sake of clarity that digital DL precoding has not been applied yet to signals transmitted therein; however, this indication does not imply anyhow that any other digital processing could have been performed with respect to these spatial beams. Each SSB corresponds to one of the analog beams, i.e. for each SSB the base station uses one predefined analog beam.

[0061] The user equipment measures a level of received power (RSRP) of each of received SSBs, selects a required number of SSBs with larger RSRPs, and generates a report on the measurements, the report indicating SSB-RI indices of the selected SSBs and information about the respective RSRPs (action 2); thereafter, the generated report is transmitted by the user equipment to the base station over uplink (UL) in the physical layer (L1) (action 3).

[0062] The base station performs transmission, to the user equipment, of channel state information (CSI) reference signals (RSs) (action 4) whereto A-BF is accordingly applied in the analog part of the base station. As an option, the base station can use, for the transmission of CSI-RSs to the user equipment, one or more analog beams corresponding to the SSBs reported in the L1 report. Before the transmission of CSI-RSs, the base station can indicate to the user equipment which CSI-RSs will be transmitted in said one or more beams, i.e., in other words, configure the user equipment to performing channel estimation based on the indicated CSI-RSs, which become so-called 'active' CSI-RSs for the user equipment. This indication can be carried out by transmitting an RRC reconfiguration message (RRC reconfig) to the user equipment.

[0063] CSI-RSs, in general, are transmitted for obtaining, by user equipments, information about the channel state of digital antenna ports of the base station. Depending on implementation, each CSI-RS port can correspond to one digital antenna port, or additional virtualization is performed in such a way that each CSI-RS port can correspond to more than one (for example, two) digital antenna ports. In other words, in view of said additional virtualization, the virtualized representation of antenna elements of the base station antenna array in the form of CSI-RS antenna ports is ultimately used. It should be noted that when communicating with the base station, the user equipment considers each CSI-RS antenna port as a single emitting element, regardless of antenna elements encompassed thereby.

[0064] In accordance with 5G NR, CSI-RSs can be transmitted by a base station in the following modes:

[0065] ● aperiodically, when the base station transmits CSI-RSs when required, and a user equipment(s) is informed in advance (for example, by downlink control information (DCI)) about the CSI-RS transmission in a specific slot;

[0066] ● periodically, and in this case, the periodicity of the transmission is preconfigured in the base station and signaled to the user equipment(s) in advance;

[0067] ● semi-persistently, when preconfiguring is performed similarly to the periodic mode, but the base station uses DL control signaling (for example, a MAC message) to activate / deactivate specific CSI-RSs.

[0068] The user equipment generates CSI based on measurements performed with respect to received CSI-RSs (action 5). The generated CSI is transmitted from the user equipment to the base station as feedback channel information (action 6). Based on the received CSI, the base station performs digital beamforming (action 7) to perform DL transmission (for example, PDSCH) to the user equipment (action 8).

[0069] It should be emphasized herein that one of implementations of A-BF for transmitting CSI-RS resources to the user equipment has been described above with reference to actions 1-3 in Fig. 1 exclusively for illustrative purposes, and this implementation is not the only possible one: for instance, the base station can select analog beams for transmitting respective CSI-RS resources to the user equipment in a different way, using approaches known in the technical field which the present invention relates to. It should also be noted that the terms 'CSI-RS', 'CSI-RS signal', and 'CSI-RS resource' can be used interchangeably in the text of this application, which should be clear to a skilled artisan, at least in the context of 5G NR.

[0070] More detailed description regarding execution of operations corresponding to actions 4-7 in Fig. 1 will be given below with reference to Fig. 2.

[0071] The base station, which is part of the NW, performs transmission of a CSI-RS set comprised of N CSI-RSs each shown in Fig. 2 with a respective identifier IDi, where 1≤i≤N; it should be noted the identifiers are implied herein by which CSI-RS resources are uniquely designated in the 5G NR communication system. A-BF is performed with respect to the transmitted CSI-RS set in the base station, i.e. a separate analog beam is used to transmit each of the N CSI-RSs. As in the case of Fig. 1, in the left side of Fig. 2, the set of possible analog beams is illustrated by dashed contours, respectively.

[0072] In the user equipment, measurements are performed with respect to each of the received CSI-RSs, and one CSI-RS is selected based on the measurements performed. For example, this selection can be implemented based on measuring received power of the received CSI-RSs, where a CSI-RS with the largest received power is selected as said one CSI-RS. The analog beam used to transmit the selected CSI-RS can be referred to herein as the 'best' or 'highest quality' beam for the user equipment. Fig. 3 illustrates the selection by the user equipment of the beam, which was used to transmit the CSI-RS with ID2, as the best one.

[0073] Based on the selected CSI-RS, the user equipment performs the channel estimation to determine a number of parameters which are included into the CSI being generated. In particular, the user equipment selects a preferred number of MIMO layers corresponding to a number of data streams which are simultaneously transmitted from the base station and which the user equipment intends to receive. This number of MIMO layers is reflected in the CSI by such a parameter as a rank indicator (RI). The user equipment generates a precoding matrix from discrete Fourier transform vectors (DFT vectors) which are selected from a predetermined code book. The generated precoding matrix is reflected in the CSI by such a parameter as a precoding matrix indicator (PMI). In addition, the user equipment determines a channel quality indicator (CQI) which is also included into the CSI. Moreover, a CSI-RS resource index (CRI) of the selected CSI-RS is included into the CSI, and by means of the CRI the base station is substantially informed about the best beam for the user equipment. In particular, for illustration according to Fig. 3, the CRI will be an index of the CSI-RS with ID2, and, accordingly, RI, PMI, CQI will be determined specifically in relation to this CSI-RS.

[0074] The generated CSI, including inter alia CRI, RI, PMI, CQI, is transmitted from the user equipment to the base station. In accordance with 5G NR, CSI is transmitted by means of uplink control information (UCI) the UL transmission of which is scheduled in the base station. One of the main aspects associated with organizing the CSI transmission within UCI is that the base station, when scheduling the UCI transmission, can not know an exact number of bits that should be allocated for this transmission, since the CSI size can not be known in advance - in particular, a number of precoding vectors in the precoding matrix depends on a preferred number of MIMIO layers which is to be selected in the user equipment depending on the actual channel state and, accordingly, can not be known in the base station in said scheduling.

[0075] In 5G NR, this problem is solved by using the following approach.

[0076] Two parts are allocated in UCI for transmitting CSI: part 1 with a fixed payload size (in bits) and part 2 with a payload size that can be variable, where the payload size of part 2 depends on UCI contents in part 1. Parameters included by the CSI are distributed accordingly across UCI part 1 and UCI part 2. CSI parameters that require a constant or fixed number of bits for being transmitted are typically placed into UCI part 1, while parameters with a variable number of bits are typically placed into UCI part 2.

[0077] For UCI part 2, the omission mechanism is provided for, according to which, if total payload of the CSI parameters exceeds the payload size initially allocated by the base station when scheduling the UCI transmission, then some of the CSI parameters assigned for being placed into UCI part 2 are excluded from UCI to be transmitted to match the size allocated thereto. To implement the omission mechanism, the CSI parameters are ordered in UCI part 2 so that parameters that are less important for operating the system are placed at the end of part 2.

[0078] Fig. 4a shows an example corresponding to 5G NR, where CSI is a wideband report (WB). The respective CSI parameters relating to the WB report context are marked in the text and in the figures of the present application by symbol ‘w’.

[0079] According to 5G NR, PMI is represented in the CSI by two parameters: PMI1 and PMI2, where PMI1 refers to DFT vectors of the precoding matrix, and PMI2 corresponds to polarization co-phasing in the precoding matrix.

[0080] In accordance with the illustration of Fig. 4a, CRI, RI, wCQI from the CSI generated by the user equipment as the WB report are placed into UCI part 1. It should be explained herein that wCQI substantially denotes CQI calculated for the entire frequency band for which the CSI is being generated.

[0081] Both PMI parameters, ordered as wPMI1, wPMI2, are included into UCI part 2, i.e. parameter wPMI1, which relates to DFT vectors of the precoding matrix for said entire frequency band, is more important for operating the system than parameter wPMI2, which corresponds to co-phasing for said frequency band. Accordingly, when the omission mechanism is utilized, parameter wPMI2 can be excluded from the CSI transmitted in UCI.

[0082] Fig. 4b shows an example corresponding to 5G NR, where CSI is a sub-channel report (SB). The respective CSI parameters relating to the SB report context are marked in the text and in the figures of this application with symbol ‘s’. It should be explained herein that, in 5G NR, sub-channels refer to frequency blocks into which the entire frequency band, for which the CSI should be generated, is divided, each of said frequency blocks consisting of several adjacent physical resource blocks (PRB), where each PRB is typically comprised of 12 frequency subcarriers.

[0083] In accordance with the illustration of Fig. 4b, UCI part 1 again includes CRI, RI, wCQI, as well as sCQI. UCI part 2 in this case includes ordered pairs of parameters {wPMI1, sPMI2} for each of the frequency sub-channels, where even sub-channels have higher importance in the above sense. Therefore, when the omission mechanism is utilized, any of parameters {wPMI1, sPMI2} corresponding to odd frequency sub-channels can be excluded. Thereafter in the text and in drawings of the present application, sPMI2 for an even frequency sub-channel can be denoted as 'sPMI2(e)', and sPMI2 for an odd frequency sub-channel can be denoted as 'sPMI2(o)'.

[0084] The base station processes the received CSI and carries out scheduling of time-frequency resources for DL transmission to the user equipment. In particular, by means of CRI, the base station is substantially informed about the best beam for the user equipment (in the left part of Fig. 2, the best beam is accordingly shown by the solid contour among the set of analog beams); the base station also uses CQI to select a modulation and coding scheme (MCS), and applies the received precoding matrix for digital beamforming for the DL transmission (DL D-BF). For instance, in accordance with the illustration of Fig. 2, the best beam can be used to transmit PDSCH to the user equipment.

[0085] The 5G NR aspects that are associated, in particular, with implementation of the code book, the CSI-RS based channel estimation, and calculation of the precoding matrix at the user equipment side, the specificity of representation and transmission of CRI, RI, PMI, CQI, and other parameters as part of CSI, are disclosed in specifications TS 38.212 (see, in particular, section 6.3.2.1.2), TS 38.214 (see, in particular, section 5.2.2.1), and also reflected in publication RU 2811989, all of which are included in their entirety into this description by reference. In particular, 5G NR Type 1 code book (see Table 5.2.2.2.1-2 from TS 38.214) can be used as the code book. It should be noted that RU 2811989 also discloses advanced technologies for implementing DL precoding.

[0086] Next, with reference to Fig. 5, such DL H-BF related aspect as implementation of the restriction in a scheduler of a base station is described. As known, the main purpose of the base station scheduler is, in general, to decide which user equipment(s) to serve in a particular time resource (e.g. slot).

[0087] For illustration purposes, in the leftmost diagram of Fig. 5, the hexagon pictorially shows a cell sector which is served by the base station and in which a plurality of user equipments are located; the base station itself is assumed to be located in the hexagon vertex which is encircled in the diagram, and configured to use, in general, several analog beams for DL transmission. As discussed above, respective A-BF is applied to CSI-RSs transmitted from the base station to the user equipments, i.e. the CSI-RS transmission to each of the user equipments is performed in one or more of the several analog beams.

[0088] In the case considered in Fig. 5, it is assumed that the base station currently intends to use only one analog beam to serve the user equipments; and this beam will be symbolically referred to as the ‘first beam’ thereafter. The first analog beam will be the best one for one user equipments in the sector, and these user equipments are denoted by triangles in Fig. 5. For other user equipments, the first beam will be the second best, and these user equipments are denoted by circles in Fig. 5. Finally, for the remaining user equipments in the sector, the first beam will be the third best, and these user equipments are denoted by squares in Fig. 5.

[0089] Configuring of the base station scheduler restriction is illustrated in Fig. 5 by using a parameter K which substantially indicates a number of analog beams for which the base station should have the feedback in the form of CSI from user equipments in the served sector, and, accordingly, scheduling of DL transmission can be performed for said user equipments.

[0090] In the context of discussing the second left drawing in Fig. 5 which corresponds to the operational implementation according to 5G NR, it is assumed that the parameter K equal to 1 is preconfigured in the base station. In this case, the base station scheduler will schedule resources for DL transmission only to those user equipments for which the first analog beam is the best; accordingly, CSI (including at least CRI, RI, PMI, CQI) from these user equipments is to be available in the base station. The case with K=1 corresponds to the strongest scheduler restriction; this case is illustrated in the drawing under consideration by presence of triangles only, i.e. those user equipments for which the first beam is the best one. Such user equipments, as shown in Fig. 5 in accordance with the current scheduler restriction, will be symbolically referred to as ‘served’ in the description of this figure; the other user equipments, which are not shown in Fig. 5 in accordance with the current scheduler restriction, will be symbolically referred to as ‘unserved’ in this description. It can be seen from the illustration of the considered drawing that the served user equipments for which resource scheduling will be performed are concentrated basically in the area of the sector to the left of the base station, said area corresponding to the coverage area provided by the first beam. The considered restriction (K=1) can be preset in user equipments or signaled to user equipments in advance, for example, by means of a CSI request transmitted by the base station in DCI.

[0091] The strong scheduler restriction discussed above with reference to part of Fig. 5 is further illustrated in Fig. 6.

[0092] As in the case considered with reference to Fig. 2, the base station transmits a CSI-RS set comprised of N CSI-RSs, each having a respective IDi, 1≤i≤N. A-BF is performed in the base station with respect to the transmitted CSI-RS set, i.e. an individual analog beam is used to transmit each of the N CSI-RSs.

[0093] Fig. 6 shows two user equipments, UE1 and UE2, located in the coverage area of the base station and receiving the transmitted CSI-RS set.

[0094] As a result of measurements of the received CSI-RS resources, UE1 determines an analog beam that was used to transmit the CSI-RS with ID2 as the best one, and UE2 determines an analog beam that was used to transmit the CSI-RS with IDN as the best one. It should be reminded herein that, according to the restriction existing in 5G NR, each of the user equipments selects only one beam which is the best from the point of view of this user equipment. As noted earlier, in each of UE1 and UE2, a number of parameters are determined for the selected CSI-RS which are included, along with a respective CRI, into CSI being generated which is transmitted to the BS.

[0095] As in the case in Fig. 5, in the example under consideration, it is assumed that the base station currently intends to use only one analog beam to serve user equipments, while it is also assumed that this beam (in other words, the 'first beam' in the terminology of Fig. 5) is the analog beam that was used to transmit the CSI-RS with ID2, i.e. the best beam for UE1. Then, the base station scheduler will schedule resources for DL transmission only to UE1 based on the CSI received from UE1. In the terminology of the disclosure of Fig. 5, UE1 will be a 'served' user equipment, UE2 will accordingly be an 'unserved' one and will not be encompassed by the current DL transmission scheduling. Therefore, in the considered operation mode of the 5G NR system, due to the above restriction, there is no opportunity to perform DL transmission scheduling jointly for both UE1 and UE2.

[0096] Next, in the context of this discussion, the following aspect of analog beamforming in 5G NR is further addressed with reference to Fig. 7a, 7b.

[0097] Two A-BF strategies are supported in 5G NR in the context of DL H-BF. Analog beams corresponding to the first strategy are intended for optimizing the base station coverage area. Such beams are spatially directional to a high extent, with steering transmission power to a given direction (i.e. narrow beams with a higher gain) (see Fig. 7a). The analog beams according to the first A-BF strategy are preferable for scheduling DL data transmission to individual user equipments, while providing maximum throughput; in other words, such beams are optimized for single-user MIMO (SU-MIMO). Thereafter in the text of the present application these analog beams may be referred to as 'SU-MIMO beams' for brevity.

[0098] Analog beams corresponding to the second strategy are intended for providing simultaneous data transmission to multiple user equipments, i.e. such beams are optimized for multi-user MIMO (MU-MIMO). The analog beams according to the second A-BF strategy are wider with a lower gain (see Fig. 7b). Thereafter in the text of the present application these beams may be referred to as 'MU-MIMO beams' for brevity.

[0099] At the same time, from the point of view of the system, it is necessary that both described approaches to A-BF work efficiently.

[0100] In the 5G NR operation scenario described above with reference to Figs. 2, 5, 6, the base station can use both SU-MIMO beams and MU-MIMO beams to transmit a single CSI-RS set, i.e. substantially the subsets of substantially different analog beams. A user equipment(s) selects and reports (by means of CRI in CSI) one analog beam which is the best from the point of view of this user equipment, based substantially on the gain of this beam. As mentioned above, SU-MIMO beams have a higher gain than MU-MIMO beams; accordingly, in most cases, MU-MIMO beams will not be selected by user equipments. It should be emphasized herein again that, by indicating one CRI in the CSI, the user equipment informs the base station about one analog beam selected by the user equipment which is the best specifically from the point of view of said user equipment; however, from the point of view of the network, the selected beam may not be optimal, for example, in the case when the base station intends to simultaneously serve multiple user equipments (MU-MIMO).

[0101] Though deployment of 5G NR systems in the world is only spinning up, nevertheless active research is being already carried out now in different directions for standardization of next generation wireless communication systems, so called 6G, which will have characteristics superior to 5G NR.

[0102] In particular, for the 6G operating range of 8-13 GHz (UPPER MID BAND), it is planned to support, at base stations, extremely large antenna arrays (for instance, comprised of 3072 antenna elements), with hybrid analog and digital beamforming with a large number of antenna ports (≤ 256). Therefore, by supporting, in particular, up to 64 simultaneously transmitted spatial MIMO layers in UPPER MID BAND communication systems, the concept of radio interface with extremely large antenna array (xMIMO) will be rendered to a principally new level. Moreover, support of a set of reference signals similar to the one used in 5G NR, such as DMRS, CSI-RS, SRS, PT-RS, PSS / SSS, is planned in 6G.

[0103] At the same time, approaches used in 5G NR may not be always directly extended to next generation communication systems. In particular, the problems existing in 5G NR, which have been discussed above with reference to Figs. 2, 5-7 and are associated with transmission of one single CSI-RS set from the base station and reporting one best analog beam from the user equipment to the base station (one CRI as part of CSI), are not of substantial nature for operation of the 5G NR system, but they can become critical for 6G wireless communication systems where xMIMO will provide support for a much larger number of analog beams, along with providing support for greater spatial directionality the beams, i.e. the beams will be even narrower and with even a higher gain. In other words, the known technologies may provide insufficient support of DL H-BF for xMIMO systems.

[0104] Hereinafter reference is made to exemplary embodiments of the present invention which are illustrated in the accompanying drawings where the same reference numerals denote similar elements. It should be appreciated that the embodiments of the invention can have various forms and should not be considered to be limited by the descriptions given herein. Therefore, the exemplary embodiments are described hereinbelow with reference to the drawings to elucidate the essence of the aspects of the present invention.

[0105] Fig. 8 shows a general view of a wireless communication system, in which various aspects of the present invention can be implemented. As shown in Fig.8, user equipments (UE) 801 communicate with base station (BS) 802 in a radio access network (RAN) 800. UE 801 (e.g. UE 801-1, 801-2, 801-3,..) are distributed over the RAN 800, and each of the UEs 801 can be fixed or mobile. Broadly known examples of UEs are smartphones, tablets, modems, etc.

[0106] The base stations 802 (e.g. BSs 802-A, 802-B, 802-C) can provide coverage for a specific geographic area commonly referred to as 'cell'. The base stations 802 basically have fixed structure, but they can have mobile implementation as well. In general, the base stations can represent macro-BSs (as illustrated by the BSs 802-A, 802-B, 802-C in Fig.8), as well as pico-BSs for pico-cells or femto-BSs for femto-cells. Cells in turn can be divided into sectors.

[0107] Coordination and management of operating the base stations 802 can be provided by a network controller which is in communication therewith (for instance, via a backhaul connection). The RAN 800 may communicate with a core network (CN) (for example, via the network controller) which provides various network functions, such as e.g. access and mobility management, session management, authentication server function, application function, etc. Moreover, the base stations 802 in the RAN 800 can also connect to each other, for instance, via a direct physical connection, which is preferably a high-speed connection.

[0108] When a user equipment is moving within the RAN 800, handover of the user equipment from one BS to another BS can be performed. For example, the UE 801-3 can be handed over from the BS 802-B to the BS 802-A. While performing this, respective communication systems parameters are reconfigured in the user equipment for operation with the new base station. The user equipment can be also handed over between sectors of one base station.

[0109] In the considered wireless communication system, interaction is possible between a user equipment and a group of interconnected base stations, and such interaction can occur not only in the case of handing over the user equipment. One base station of the group of base stations is a serving base station for the user equipment, and various aspects of coordinating joint operation of the base stations of the group during such interaction can be performed in a centralized way (e.g. by the network controller) and / or by the serving base station.

[0110] The concept of Cloud RAN (C-RAN) implemented in the 8G NR wireless communication system, where said concept is in dividing a base station into three parts and using a special interface defined for information exchange between these functional parts. In particular, the base station can be divided into a radio unit (RU) which performs radio transceiver functions, a distributed unit (DU) for L1 (physical layer) computations and L2 (MAC layer) computations, and a centralized unit (CU) for L2 and L3 (radio resource control (RRC) layer) computations. Such a division enables to centralize CU units in a respective central network node, while DUs can be distributed to a greater extent, at cell nodes. In this case, switching of connections between cell sites can be performed at L1 layer, i.e. with relatively low latency. Support for this concept is also expected in 6G wireless communication networks.

[0111] It should be noticed that the description according to Fig.8 and the figure itself have exclusively illustrative, non-limiting nature with the aim of outlining the general operation environment of the present invention. Though only known basic components of the communication system are illustrated in Fig.8, it should be appreciated that the communication system can further include plural other elements.

[0112] Each of the BSs 802 shown in Fig.8 includes hardware and logical means to implement respective functions in the base station. The hardware means refer to, in particular, an antenna array comprised of transceiving antenna elements which have been discussed above, various specially configured processors, controllers, data storage devices, other circuit elements, as well as buses connecting them. The logical means refer to software which is stored in respective memory devices and configures respective circuit elements. Firmware directly hardwired in processors and controllers also refers to the software. The abovementioned hardware means are configured inter alia to perform various processing with respect to transmitted and received signals, including (de)modulation, (de)multiplexing, (de)coding, amplifying, filtering, digitizing, (de)interleaving, resource allocation, reception / transmission scheduling.

[0113] In a similar way, each of the UEs 801 shown in Fig.8 includes hardware and logical means to implement respective functions in the user equipment. The hardware means refer to, in particular, transceiving devices with respective antenna elements, various specially configured processor(s), controllers, data storage devices, other circuit elements, as well as buses connecting them. The logical means refer to software which is stored in respective memory devices and configures respective circuit elements. Firmware directly hardwired in controllers also refers to the software. The indicated hardware means are configured inter alia to perform various processing with respect to transmitted and received signals, including (de)modulation, (de)multiplexing, (de)coding, amplifying, filtering, digitizing, (de)interleaving. Moreover, the user equipment comprises means to interact with a user, including a touch screen, speakers / microphone, buttons, as well as user applications which are stored in the memory of the user equipment and executed by the processor of the user equipment in a respective operating system.

[0114] Examples of the abovementioned processors / controllers include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), discrete hardware integrated circuits, etc. Firmware / software executed by the processors / controllers should be understood broadly, as referring to computer-executable instructions, instruction sets, program code, code segments, subroutines, program modules, objects, procedures, etc. The software is stored in respective computer-readable media which can be implemented e.g. in the form of random-access memory (RAM), read-only memory (ROM), electrically erasable programmable (EEPROM), solid state storage devices, magnetic storage devices, optical storage devices, etc. which can be recorded with respective program codes and data structures that can be accessed by respective processors / controllers.

[0115] The hardware and software elements of base stations and user equipments, as listed above, are configured to enable performing, in the base stations and user equipments, the methods according to the present application which are described hereinbelow. Implementation itself of the component hardware means of the base stations and user equipments and specific configuring thereof, including by respective logical means, is known in the technical field which the present application relates to. Moreover, various functions according to the methods of the present application can be performed in plural separate elements or in one or more integral elements, as defined by design structural characteristics.

[0116] To solve the technical problem addressed by the present invention, as outlined above, one aspect of the present invention, in general, provides for transmitting a plurality of CSI-RS sets from a base station to a user equipment(s), as well as reporting from the user equipment, within CSI, about two or more CSI-RSs with respect to which the respective channel estimation has been performed.

[0117] This aspect is described in more detail with reference to Fig. 9 the format of which is similar to the format of Fig. 2.

[0118] A base station, which is part of the NW, transmits a plurality of CSI-RSs comprising two CSI-RS sets which are designated in Fig. 9 as CSI-RS set 1 and CSI-RS set 2, respectively. CSI-RS set 1 is comprised of N1 CSI-RSs, each, similarly to Fig. 2, shown in Fig. 9 with a respective identifier IDi, where 1≤i≤N1; CSI-RS set 2 is comprised of N2 CSI-RSs, each also shown in Fig. 9 with a respective identifier IDj, where 1≤j≤N2. A-BF is performed with respect to each of the two transmitted CSI-RS sets in the base station, i.e. an individual analog beam is used to transmit each CSI-RS of N1 CSI-RSs of CSI-RS set 1 and N2 CSI-RSs of CSI-RS set 2. It should be noted herein that there is no limiting reliance on actions 1-3 according to Fig. 1 for performing A-BF in the context of disclosure of the present invention.

[0119] Subsets of analog beams of different types from the entire plurality of analog beams usable by the base station to transmit the CSI-RS set can be respectively used to transmit CSI-RS set 1 and CSI-RS set 2. In particular, in the illustration of Fig. 9, it is assumed that SU-MIMO beams are correspondingly used to transmit CSI-RS set 1, and MU-MIMO beams are correspondingly used to transmit CSI-RS set 2. Each of these subsets of SU-MIMO and MU-MIMO beams is illustrated accordingly by dashed contours in the left side of Fig. 9. Due to the specificity of SU-MIMO beams and MU-MIMO beams, as described above, it is assumed in Fig. 9 that the number of SU-MIMO beams in their subset is greater than the number of MU-MIMO beams in the respective subset; therefore, N1>N2.

[0120] According to an embodiment of the present invention, the 5G NR approach can be used to inform the user equipment in advance about the plurality of CSI-RSs that should be received by the user equipment. In particular, according to 5G NR, the following structure is used to characterize a CSI-RS resource:

[0121]

[0122] Therefore, according to this embodiment, such a CSI-RS resource structure is signaled in advance from the base station to the user equipment for each of CSI-RSs that should become active for the user equipment (they may be all of CSI-RSs to be transmitted from the base station, or part of them). For example, an array of such CSI-RS resource structures that encompasses the entire plurality of CSI-RSs to be activated in the user equipment can be transmitted in advance from the base station to the user equipment. This signaling can be carried out by means of RRC signaling, for example, by using the RRC reconfig message mentioned above.

[0123] In addition, in accordance with the considered embodiment of the present invention, the base station signals in advance to the user equipment information notifying about CSI-RS sets that will be present in the plurality of CSI-RSs to be transmitted. This notification can be carried out, for example, by signaling in advance from the base station to the user equipment the following structure with respect to each of the CSI-RS sets:

[0124]

[0125] that is, again, a respective array of such structures can be transmitted to the user equipment. At the same time, this notification about the CSI-RS sets can be carried out in the same RRC reconfig message or separately from therefrom in a similar way.

[0126] As can be seen from the above consideration, presence of a specific one of the active CSI-RSs in a specific CSI-RS set can be identified in the user equipment, at least, based on the element nzp-CSI-RS-Resources in a respective structure NZP-CSI-RS-ResourceSet, said element providing unique identifiers NZP-CSI-RS-ResourceId of CSI-RS resources in the set; this element also allows to determine a number of CSI-RSs in said set.

[0127] Then, according to the considered aspect of the present invention, a predefined number K of CSI-RSs is selected in the user equipment from CSI-RS sets received from the base station, in order to generated CSI. Moreover, the value K is set in the base station and signaled in advance to the user equipment.

[0128] As one of the possible implementations, the configuring, for the user equipment side, of a specific selection of K CSI-RSs among the CSI-RS sets received from the base station can be carried out based on an indication contained in a CSI request transmitted from the base station. That is, the considered implementation relates to the aperiodic CSI-RS mode described above. At the top of Fig. 9, the transmission of the CSI request is indicated by the thick dashed arrow. As noted earlier, the CSI request is typically transmitted to the user equipment via DCI.

[0129] Furthermore, K can be set i) with respect to all the transmitted CSI-RS sets (i.e. K CSI-RSs are to be selected from the entire plurality of CSI-RSs), or ii) with respect to part of the CSI-RS sets (i.e. the user equipment should select K CSI-RSs over a specific CSI-RS set(s)) or with respect to each of the transmitted CSI-RS sets (i.e. K CSI-RSs are to be independently selected in each of the CSI-RS sets). The selection corresponding to option i) can be referred to thereafter as 'joint selection', and the selection corresponding to option ii) can be referred to thereafter as 'independent selection'.

[0130] As in the case of 5G NR, the selection itself of K CSI-RSs from the received CSI-RS sets can be performed based on measuring received power of each of the CSI-RSs, i.e. the predefined number K of CSI-RSs with larger received power values are selected. However, it should be obvious to a skilled artisan that said implementation is not the only possible one, and other measurements can be used to select K CSI-RSs - for example, based on the spectral efficiency or transmission performance metric.

[0131] For the case of the joint selection in the considered implementation, the base station can preset a power offset with respect to some of the transmitted CSI-RS sets, and this offset can be set at the level of a CSI-RS set or individual CSI-RSs of the CSI-RS set. The setting of the power offset can be carried out, for example, by means of the element powerControlOffset in the CSI-RS resource structure illustrated above. As a result, when selecting the predefined number K CSI-RSs, the user equipment applies preset power offsets to respective CSI-RSs. By means of this procedure, more flexible control can be ensured, at the base station side, with respect to the selection of CSI-RS resources performed by the user equipment.

[0132] The approach according to the considered one implementation is, in general, in encoding the abovementioned indication by means of a respective bit field in DCI, and, to this end, a respective code table is preconfigured in the base station, and the format of the code table is illustrated in a generalized way in Table 1:

[0133]

[0134] The ellipsis prior to two digits in the left column of Table 1 shows that a bit field by which a specific set of active CSI-RSs is encoded can have different lengths depending on implementation. In Table 1, each value of the bit field (except the one that encodes 'CSI is not requested') corresponds to a predefined target number Kiof CSI-RSs based on which CSI should be generated by the user equipment and reported to the base station, i.e. the target number of CRIs that should be included into the CSI being generated, along with respective parameters (such as RI, PMI, CQI).

[0135] The code table preconfigured in the base station is signaled in advance from the base station to the user equipment, for example, by RRC signaling.

[0136] Below, in Tables 2, 3, exemplary implementations of the code table, generally illustrated in Table 1, are given for the case where the respective DCI bit field has length 2 bits (Table 2) and length 3 bits (Table 3). Tables 2, 3 can be considered in a non-limiting way as corresponding to the example of the transmission of two CSI-RS sets, as discussed with reference to Fig. 9.

[0137]

[0138]

[0139] The base station, at its own discretion (for example, depending on the current state of the network), selects a bit field value in a respective code table, and this value is signaled to the user equipment in the DCI CSI request. Based on the bit field value contained in the received CSI request, the user equipment, according to its code table, determines how many CSI-RSs should be selected to generate CSI and from which received CSI-RS set(s) the CSI-RSs should be selected.

[0140] The bit values '01', '10', '11' in the exemplary implementation according to Table 2 indicate, respectively, with respect to the entire plurality of received CSI-RS sets, the numbers K1=1, K2=2, K3=3 of CRIs which are to be reported in CSI; that is, this implementation purely relates to the joint selection of CSI-RSs.

[0141] Upon reception, by the user equipment, of a CSI request with the bit field value '01', the user equipment will select one CSI-RS with the largest received power and report a respective CRI within CSI. Taking into account the above discussion, the base station, by means of said CRI, will be informed about one analog beam which is best for the user equipment and which was used to transmit the selected CSI-RS.

[0142] Then, upon reception, by the user equipment, of a CSI request with the bit field value '10', the user equipment will select two CSI-RSs with the largest and second largest received powers and report two respective CRIs within CSI. The base station, by means of these two CRIs, will be informed accordingly about the best and second best beams for the user equipment.

[0143] Finally, upon reception, by the user equipment, of a CSI request with the bit field value '11', the user equipment will select three CSI-RSs with the largest and second and third largest received powers and report three respective CRIs within CSI. In a similar way, the base station, by means of these three CRIs, will be informed accordingly about the best and second and third best beams for the user equipment.

[0144] In another exemplary implementation, according to Table 3, bit values (except the value '000') can respectively indicate not only the target number Kiof CRIs to be reported, but also which specific CSI-RS set(s) respective CSI-RSs should be selected from. For instance, the value '100' of the bit field in the DCI CSI request substantially instructs the user equipment to select two CSI-RSs with the largest and second largest received powers only from CSI-RS set 2, and report two respective CRIs and associated parameters within CSI. That is, in this case, the independent selection of the preset number of CSI-RSs is performed. At the same time, the value '101' instructs the user equipment to select one CSI-RS with the largest received power among both received CSI-RS sets; that is, in this case, the joint selection of the preset number of CSI-RSs is performed.

[0145] As seen, the implementation according to Table 3 is associated with a greater bit payload in DCI, but provides greater flexibility in configuring, for the user equipment, of a preset number of CSI-RSs to be selected.

[0146] Fig. 10, which basically develops the illustration according to Fig. 9, shows an example of performing, by a user equipment, of selection of a preset number of CSI-RSs from two received CSI-RS sets, under assumption that the user equipment has received, by DCI, a CSI request with the value of said bit field equal to '111' (see Table 3 above) or equal to '11' (see Table 2 above). In other words, the user equipment is instructed to select K=3 CSI-RSs among both 1 CSI-RS set and set CSI-RS 2, i.e. to perform the joint selection.

[0147] Fig. 10a shows CSI-RSs selected by the user equipment from CSI-RS set 1 for transmission of which SU-MIMO beams are used (see Fig. 9); the used subset of SU-MIMO beams is symbolically shown by dashed contours at the top of Fig. 10a. Fig. 10b shows CSI-RSs selected by the user equipment from CSI-RS set 2 for transmission of which MU-MIMO beams are used (see Fig. 9); the used subset of MU-MIMO beams is shown similarly by dashed contours at the top of Fig. 10b.

[0148] In the considered example, it is also assumed that a power offset has been set, in the base station, with respect to CSI-RS set 2 in the upward direction, in accordance with the implementation described above. This assignment of the power offset substantially indicates increased importance of MU-MIMO beams at the base station side.

[0149] This offset is applied by the user equipment when jointly selecting a preset number K of CSI-RSs from the two CSI-RS sets. As a result, despite the fact that, as noticed earlier, SU-MIMO beams are characterized by a higher gain, in the considered case the user equipment, in accordance with received power, selects two CSI-RSs from CSI-RS set 1, in particular, the CSI-RSs with ID2and IDN1(see Fig. 10a), as well as one CSI-RS from CSI-RS set 2, in particular, the CSI-RS with IDN2-1(see Fig. 10b). That is, for example, due to the applied power offset, the corrected received power of the CSI-RS with IDN2-1from CSI-RS set 2 has become the third largest in the considered joint selection; in other words, said application of the power offset has partially balanced the higher gain of the SU-MIMO beams.

[0150] Returning to Fig. 9, for each of the selected K=3 CSI-RSs, a set of parameters is determined in the user equipment (in particular, RI, PMI, CQI) which are included into the CSI being generated. Fig. 9 illustrates the transmission, from the user equipment to the base station, of the CSI containing: CRI1, RI1, PMI1, CQI1corresponding to the CSI-RS with IDN1selected from CSI-RS set 1; CRI2, RI2, PMI2, CQI2corresponding to the CSI-RS with IDN2selected from CSI-RS set 1; CRI3, RI3, PMI3, CQI3corresponding to the CSI-RS with IDN2-1selected from CSI-RS set 2. The analog beams reported by the respective CRIs are shown in each of the subsets by solid contours in the left pat of Fig. 9. As in the case of 5G NR, transmission of the CSI to the base station is preferably carried out by UCI. Approaches to distribution of the CSI parameters within UCI according to embodiments of the present invention will be described below.

[0151] The base station processes the received CSI and schedules time-frequency resources for DL transmission to the user equipment. As shown at the bottom of Fig. 9, the resources for transmitting PDSCH were scheduled by the base station with respect to the best MU-MIMO beam (CRI3), despite the fact that the CSI-RSs with greater received power corresponded to the two reported SU-MIMO beams (CRI1, CRI2).

[0152] It should be noted herein that, although Fig. 9, 10 show the transmission of the two CSI-RS sets, the present invention provides for simultaneous transmission of a greater number of CSI-RS sets, as well as transmission of one CSI-RS set, thereby providing backward compatibility with 5G NR; furthermore, the present invention also provides for the capability of reporting about other target numbers K of selected CSI-RSs different from three. Moreover, the usage of the subset of SU-MIMO beams and the subset of MU-MIMO beams for the respective transmission of CSI-RS sets, as shown in Figs. 9, 10, has rather illustrative than limiting nature; accordingly, the present invention encompasses other possible distributions of transmitted CSI-RS sets over usable analog beams. In general, a number of CSI-RSs in each of transmitted CSI-RS sets can be configured in the base station individually for the CSI-RS set.

[0153] Then, the usage of the aperiodic CSI-RS mode in the description of the illustration according to Figs. 9, 10 is also not a limitation, and the approach according to the present invention is equally applicable to the periodic and semi-persistent CSI-RS modes. For instance, in the periodic mode, transmitting a plurality of CSI-RSs from the base station, as well as selecting a predefined number of CSI-RSs, generating CSI, and transmitting the CSI in the user equipment are performed periodically, where the periods for said operations can be different. A respective period(s) is preconfigured in the base station and signaled in advance to the user equipment. As noted earlier, in the semi-persistent mode, the base station additionally uses downlink control signaling (for example, MAC signaling) to preliminary indicate (activate) specific CSI-RS resources to the user equipment. The approach corresponding to an embodiment of the present invention for configuring, for the user equipment side by the base station, the selection of a preset number of CSI-RS resources, as described above with reference to Figs. 9, 10 and Tables 1-3, is equally applicable to the two CSI-RS modes considered here. According to a possible implementation, said configuring (for example, by transmitting a respective bit value) can be carried out by MAC signaling, RRC signaling, or combination thereof.

[0154] In the context of DL H-BF, the illustrated approach according to the present invention provides support for transmitting, to a user equipment(s), several CSI-RS sets (in particular, by using substantially different analog beams) and support for the capability of simultaneously reporting, from the user equipment to the base station, about several selected CSI-RSs by the accordingly generated CSI (in particular, about CSI-RSs from different CSI-RS sets), thereby, in turn, providing more flexible scheduling of resources for DL transmission at the base station side. More specifically, upon reception of such CSI, the base station becomes more informed about the channel estimation performed by the user equipment(s), accordingly, the base station scheduler becomes less constrained and is enabled to schedule DL transmissions to a greater number of user equipments, along with support of efficient operation of both A-BF approaches, as described above, i.e. with optimization for SU-MIMO and with optimization for MU-MIMO. This, in general, provides improvement of efficiency of the entire system. It should be emphasized that said advantage is especially urgent for xMIMO systems which are characterized by wide frequency band and efficient spatial organization of DL transmissions and for which, accordingly, proper support for usage of MU-MIMO beams is very important.

[0155] Returning, in view of the foregoing, to Fig. 5, in the context of the presentation according to the second right drawing in this figure, it is assumed that the target number K of CSI-RSs is preconfigured in the base station as equal to 2. The preconfigured parameter K can be signaled to user equipments, for example, by using the approach described above with reference to Tables 1-3. In this case, the scheduler will schedule resources only for user equipments for which the first beam is either the best or the second best; accordingly, CSI reported from such user equipments should be available in the base station. The case with K=2 corresponds to a moderate scheduler restriction. This case is illustrated in the drawing under consideration by presence in the sector of triangles and circles only, i.e. the served user equipments for which the first beam is the best and second best; the other user equipments are not shown as unserved in accordance with the current moderate scheduler restriction.

[0156] Finally, in the context of discussing the rightmost drawing in Fig. 5, it is assumed that the parameter K equal to 3 is preconfigured in the base station. In this case, CSI from all the user equipments shown in Fig. 5 to be present in the sector can be available in the base station. The case with K=3 corresponds to a weak restriction in the base station scheduler, which is illustrated in the drawing under consideration by the presence of triangles, circles, and squares. In other words, DL transmissions (e.g. PDSCH) can be scheduled by the scheduler for any of the user equipments in the sector, regardless of the fact that the base station intends to use only the first beam, and, therefore, all the user equipments in the sector can be considered as served ones in the above sense. This case may correspond to the illustration of Fig. 9, 10, where, taking into account the three CSI-RSs reported by the CSI, one MU-MIMO beam (the first beam in the terminology according to Fig. 5) has been selected for scheduling DL transmissions to user equipments.

[0157] Thus, the arrows in Fig. 5 indicate the direction of relaxation of the base station scheduler restriction, as provided by the present invention. Again, the capability of providing CSI with respect to several analog beams (K>1), as supported by the present invention, provides mitigation of the above restriction imposed onto the base station scheduler in the context of DL H-BF, at least due to the fact that the more channel information is reported by user equipments to the base station, the more flexibility the scheduler has in terms of scheduling PDSCH transmissions to more user equipments.

[0158] Next, with reference to the diagrams of Fig. 11-12, transmission of CSI generated in a user equipment to a base station by UCI is described according to exemplary embodiments of the present invention.

[0159] As in the case of 5G NR, transmission of UCI, by which the generated CSI including inter alia CRI, RI, PMI, CQI is transmitted from the user equipment to the base station, is scheduled in advance in the base station. Then, similarly to 5G NR, in the considered embodiments, the two parts are allocated in UCI for transmitting the CSI: part 1 with a fixed payload size and part 2 with a payload size that can be variable, wherein the parameters included by the CSI are distributed accordingly across UCI part 1 and UCI part 2: CSI parameters that require a constant or fixed number of bits for being transmitted are preferably placed into UCI part 1, while parameters with a variable number of bits are preferably placed into UCI part 2; the omission mechanism described above is also supported for UCI part 2. Accordingly, in order to implement this mechanism, in the considered embodiments the CSI parameters are also ordered in UCI part 2 in such a way that parameters that are less important for operating the system are placed at the end of part 2.

[0160] Fig. 11a illustrates a first embodiment of filling UCI part 1 for the case where the CSI is a WB report.

[0161] In accordance with the illustration of Fig. 11a, UCI part 1 contains a sequence of sets {CRIi, RIi, wCQIi}, where i, 1≤i≤K, denotes an index of a CSI-RS among K selected CSI-RSs which are reported in the CSI by using respective CRIs (see the description above with reference to Fig. 9, 10 and Tables 1-3). The sets {CRIi, RIi, wCQIi} in said sequence can be ordered according to received power levels of respective CSI-RSs. For instance, {CRI1, RI1, wCQI1} will correspond to a CSI-RS resource with the highest received power level, {CRI2, RI2, wCQI2} will correspond to a CSI-RS resource with the second highest received power level, and so on. It should be noted that this way of ordering is not the only possible one, and other orderings of the considered sets in the sequence thereof, which UCI part 1 is comprised of, can be used.

[0162] Fig. 11b illustrates a second embodiment of filling UCI part 1 for the case where the CSI is a WB report.

[0163] In the considered embodiment, the combinatorial encoding is used. Namely, indices ci, i=0,...K-1, of K CSI-RSs, which are reported in the CSI by using respective CRIs, are encoded among a plurality of N consecutive CSI-RS indices, said plurality being common to all transmitted CSI-RS sets (in particular, for the embodiment disclosed with reference to Figs. 9, 10 and Tables 1-3, N=N1+N2), i.e. {ci}: 1≤c0<c1…<cK-1≤N, in the form of a code point pCRI:

[0164]

[0165]

[0166]

[0167] In accordance with the illustration of Fig. 11b, UCI part 1 contains: a code point pCRIwhich, by means of the indices {ci} encoded thereby, represents a set of respective {CRIi}; as well as a sequence of sets {RIi, wCQIi} ordered according to the order of CRIi's in the set {CRIi}. As compared to the first embodiment considered with reference to Fig. 11a, the second embodiment of Fig. 11b is obviously characterized by lower bit overhead in UCI.

[0168] Next, Fig. 12a illustrates a first embodiment of filling UCI part 1 for the case where the CSI is an SB report. Similarly to the disclosure of Fig. 11a, in accordance with the illustration of Fig. 12a, UCI part 1 contains a sequence of sets {CRIi, RIi, wCQIi, sCQIi}, where i, 1≤i≤K, denotes an index of a CRI among K CRIs reported in the CSI, wherein the sets {CRIi, RIi, wCQIi, sCQIi} in said sequence are also ordered according to received power levels of respective CSI-RSs.

[0169] Fig. 12b illustrates a second embodiment of filling UCI part 1 for the case where the CSI is an SB report. In the considered embodiment, similarly to the disclosure of Fig. 11b, the combinatorial encoding is involved by using equation (1), and, as a result, in accordance with the illustration of Fig. 12b, UCI part 1 contains: a code point pCRIwhich, by means of indices {ci} encoded thereby, represents a set of respective {CRIi}; and a sequence of sets {RIi, wCQIi, sCQIi} ordered according to the order of CRIi's in the set {CRIi}.

[0170] Fig. 11c, 11d respectively illustrate a first and second embodiments of filling UCI part 2 for the case where the CSI is a WB report.

[0171] In accordance with the illustration of Fig. 11c, UCI part 2 contains a sequence of sets {wPMI1i, wPMI2i}, and, according to the illustration of Fig. 11d, UCI part 2 contains a set {wPMI1i} followed by a set {wPMI2i}. In order to fill UCI part 1 shown in each of Figs. 11c, 11d, either the embodiment shown in Fig. 11a or the embodiment shown in Fig. 11b can be used in a non-limiting way, as well as either the embodiment shown in Fig. 12a or the embodiment shown in Fig. 12b can be used in a non-limiting way. In any of the indicated options of filling UCI part 1, the sequence of sets {wPMI1i, wPMI2i} in Fig. 11c and each of the sets {wPMI1i}, {wPMI2i} in Fig. 11d will be ordered in UCI part 2 according to the ordering of {CRIi} in UCI part 1.

[0172] Finally, Figs. 12c, 12d respectively illustrate a first and second embodiments of filling UCI part 2 for the case where the CSI is an SB report.

[0173] In accordance with the illustration of Fig. 12c, UCI part 2 contains a set {wPMI1i} followed by a set {sPMI2i(e)} for even frequency sub-channels, followed by a set {sPMI2i(o)} for odd frequency sub-channels, and, according to the illustration of Fig. 12d, a sequence of sets {wPMI1i, sPMI2i(e), sPMI2i(o)} is placed into UCI part 2.

[0174] In order to fill UCI part 1 shown in each of Figs. 12c, 12d, either the embodiment shown in Fig. 12a or the embodiment shown in Fig. 12b can be used in a non-limiting way, as well as either the embodiment shown in Fig. 11a or the embodiment shown in Fig. 11b can be used in a non-limiting way. For any of the indicated options of filling UCI part 1, each of the sets {wPMI1i}, {sPMI2i(e)}, {sPMI2i(o)} in Fig. 12c and the sequence of sets {wPMI1i, sPMI2i(e), sPMI2i(o)} in Fig. 12d will be ordered in UCI part 2 according to the ordering of {CRIi} in UCI part 1.

[0175] The embodiments discussed above with reference to Figs. 11-12 are basically an adaptation of the approach used in 5G NR for organizing transmission of CSI parameters within UCI for the present invention according to which the CSI parameters obtained based on several selected CSI-RS resources can be transmitted in the CSI. It should be emphasized that the present invention provides for usage of other options for distributing the CSI parameters over UCI which differ from the ones shown in Fig. 11-12.

[0176] Next, with reference to the flowchart of Fig. 13, a method 1300 of generating CSI in a wireless communication system in the context of DL H-BF is described.

[0177] In step 1310, a base station, for example, such as BS 802-A, 802-B, 802-C in Fig. 8, transmits a plurality of CSI-RSs which can comprise two or more CSI-RS sets. For example, as described above with reference to Fig. 9-10, the subset of SU-MIMO beams can be used to transmit one CSI-RS set, and the subset of MU-MIMO beams can be used to transmit another CSI-RS set. A number of transmitted CSI-RSs in each CSI-RS set of the plurality of CSI-RSs can be configured in the base station individually for the CSI-RS set.

[0178] In step 1320, the user equipment, for example, such as UE 801-1, 801-2,...in Fig. 8, selects a predefined number K of CSI-RSs from the CSI-RS sets received from the base station. In step 1320, the channel estimation is performed in the user equipment based on each of the selected K CSI-RSs to calculate a respective set of parameters, including RI, PMI, CQI. In this step, the user equipment also generates CSI by including thereinto, for each of the selected K of CSI-RSs, the set of parameters calculated for it and a respective CRI.

[0179] Steps 1310 and 1320 can be performed upon reception of a CSI request from the base station transmitted via DCI (see optional step 1305, shown as the dashed block in Fig. 13), where the exemplary embodiments of configuring a specific selection of K CSI-RSs among the received CSI-RS sets based on a value of the respective bit field in the CSI request have been discussed in detail above with reference to Figs. 9, 10 and Tables 1-3. It should be noted herein that step 1305 may be performed not before step 1310, as illustrated in Fig. 13, but after step 1310; this aspect does not impose a limitation onto the present invention.

[0180] In step 1330, the user equipment transmits the generated CSI to the base station, preferably by UCI. The options of arranging the parameters of the CSI within UCI are discussed in detail above with reference to Figs. 11-12.

[0181] Fig. 14 illustrates a structure of implementation a structure of a UE according to an embodiment of the disclosure.

[0182] The UE 1400 described with reference to FIGS. 1 to 13 may correspond to the UE of FIG. 14. Referring to FIG. 14, the UE may include a transceiver 1410, a memory 1420, and a controller 1430.

[0183] The transceiver 1410, controller 1430, and memory 1420 of the UE 1400 may be operated according to the above-described UE communication method. However, the components of the UE are not limited thereto. For example, the UE may include more or fewer components than the above-described components. The transceiver 1410, the controller 1430, and the memory 1420 may be implemented in the form of a single chip. The controller 1430 may include one or more processors.

[0184] The transceiver 1410 collectively refers to a transmitter of the UE 1400 and a receiver of the UE 1400 and may transmit and receive signals to / from another device. To that end, the transceiver 1410 may include a radio frequency (RF) transmitter for frequency-up converting and amplifying signals transmitted and an RF receiver for low-noise amplifying signals received and frequency-down converting the frequency of the received signals. However, this is merely an example of the transceiver 1410, and the components of the transceiver 1410 are not limited to the RF transmitter and the RF receiver.

[0185] The transceiver 1410 may receive signals via a radio channel, output the signals to the controller 1430, and transmit signals output from the controller 1430 via a radio channel.

[0186] The memory 1420 may store programs and data necessary for the operation of the UE 1400. The memory 1420 may store control information or data that is included in the signal obtained by the UE. The memory 1420 may include a storage medium, such as read only memory (ROM), random access memory (RAM), hard disk, CD-ROM, and digital versatile disc (DVD), or a combination of storage media. Rather than being separately provided, the memory 1420 may be embedded in the controller 1430.

[0187] The controller 1430 may control a series of processes for the UE to be able to operate according to the above-described embodiments.

[0188] Fig. 15 illustrates a structureof implementation a structure of a base station according to an embodiment of the disclosure.

[0189] The base station described with reference to FIGS. 1 to 13 may correspond to the base station of FIG. 15. The base station of FIG. 15 is one of AMF(Access and Mobility management Function), UDM(Unified Data Management), USER-ID Function, and 3rd party APP. Referring to FIG. 15, the base station may include a transceiver 1510, a memory 1520, and a controller 1530.

[0190] The transceiver 1510, controller 1530, and memory 1520 of the base station 1500 may be operated according to the above-described base station communication method. However, the components of the base station are not limited thereto. For example, the base station may include more or fewer components than the above-described components. The transceiver 1510, the controller 1530, and the memory 1520 may be implemented in the form of a single chip. The controller 1530 may include one or more processors.

[0191] The transceiver 1510 collectively refers to a transmitter of the base station and a receiver of the base station and may transmit and receive signals to / from another device. To that end, the transceiver 1510 may include a radio frequency (RF) transmitter for frequency-up converting and amplifying signals transmitted and an RF receiver for low-noise amplifying signals received and frequency-down converting the frequency of the received signals. However, this is merely an example of the transceiver 1510, and the components of the transceiver 1510 are not limited to the RF transmitter and the RF receiver.

[0192] The transceiver 1510 may receive signals via a radio channel, output the signals to the controller 1530, and transmit signals output from the controller 1530 via a radio channel.

[0193] The memory 1520 may store programs and data necessary for the operation of the base station. The memory 1520 may store control information or data that is included in the signal obtained by the base station. The memory 1520 may include a storage medium, such as read only memory (ROM), random access memory (RAM), hard disk, CD-ROM, and digital versatile disc (DVD), or a combination of storage media. Rather than being separately provided, the memory 1520 may be embedded in the controller 1530.

[0194] The controller 1530 may control a series of processes for the base station to be able to operate according to the above-described embodiments.

[0195] It should also be understood that the illustrated exemplary embodiments are only preferred, but not the only possible implementations of the invention. Specifically, the scope of the present invention is defined by the claims and equivalents thereof.

Claims

1.A method of generating channel state information (CSI) in a wireless communication system, the method comprising:performing, from a base station (BS) of the wireless communication system, transmission of a plurality of channel state information reference signals (CSI-RSs), wherein the plurality of CSI-RSs comprises two or more CSI-RS sets; andselecting a predefined number of CSI-RSs, by a user equipment (UE) in the wireless communication system, from the CSI-RS sets received from the base station, and generating the CSI based on the selected CSI-RSs, wherein the CSI comprises, for each of the selected CSI-RSs, respective parameters, including an identifier of the CSI-RS.2.The method of claim 1, further comprising: transmitting the generated CSI from the user equipment to the base station.3.The method of claim 1, wherein the parameters include, at least, a rank indicator (RI), a channel quality indicator (CQI), and an indicator of a precoding matrix (PMI) calculated in the user equipment for a respective CSI-RS among the selected CSI-RSs, wherein said identifier is a CSI-RS resource index (CRI), wherein the PMI is represented in the CSI by two parameters: PMI1 and PMI2, where PMI1 relates to DFT vectors, and PMI2 relates to polarization co-phasing in the precoding matrix.4.The method of claim 1, wherein the base station uses, for the transmission of the plurality of CSI-RSs, a set of spatial beams, wherein the two or more CSI-RS sets include: a first CSI-RS set transmitted by using a subset of first type beams from the set of spatial beams, and a second CSI-RS set transmitted by using a subset of second type beams from the set of spatial beams.5.The method of claim 4, wherein the first type beams are narrower beams with a higher gain which are intended for single-user MIMO (SU-MIMO), and the second type beams are wider beams with a lower gain which are intended for multi-user MIMO (MU-MIMO).6.The method of claim 1, wherein a number of CSI-RSs transmitted in each of the two or more CSI-RS sets is preset in the base station individually for the CSI-RS set and signaled in advance from the base station to the user equipment.7.The method of claim 2, wherein the selecting a predefined number of CSI-RSs, the generating the CSI, and the transmitting the generated CSI are performed upon reception of a CSI request from the base station.8.The method of claim 2, wherein the selecting a predefined number of CSI-RSs, the generating the CSI, and the transmitting the generated CSI are performed periodically, with at least one predetermined period, wherein the at least one predetermined period is preconfigured in the base station and signaled in advance from the base station to the user equipment.9.The method of claim 1, further comprising:receiving a CSI request, by a user equipment (UE) in the wireless communication system, from a base station (BS) of the wireless communication system, the CSI request comprising an indication of at least a predefined number of channel state information reference signals (CSI-RSs) based on which the CSI is to be generated.10.A device of generating channel state information (CSI) in a wireless communication system, the deceive comprising:a transceiver; anda processor configured to:perform, from a base station (BS) of the wireless communication system, transmission of a plurality of channel state information reference signals (CSI-RSs), wherein the plurality of CSI-RSs comprises two or more CSI-RS sets; andselect a predefined number of CSI-RSs, by a user equipment (UE) in the wireless communication system, from the CSI-RS sets received from the base station, and generating the CSI based on the selected CSI-RSs, wherein the CSI comprises, for each of the selected CSI-RSs, respective parameters, including an identifier of the CSI-RS.11.The device of claim 10, wherein the processor is configured to transmit the generated CSI from the user equipment to the base station.12.The device of claim 10, wherein the parameters include, at least, a rank indicator (RI), a channel quality indicator (CQI), and an indicator of a precoding matrix (PMI) calculated in the user equipment for a respective CSI-RS among the selected CSI-RSs, wherein said identifier is a CSI-RS resource index (CRI), wherein the PMI is represented in the CSI by two parameters: PMI1 and PMI2, where PMI1 relates to DFT vectors, and PMI2 relates to polarization co-phasing in the precoding matrix.13.The device of claim 10, wherein the base station uses, for the transmission of the plurality of CSI-RSs, a set of spatial beams, wherein the two or more CSI-RS sets include: a first CSI-RS set transmitted by using a subset of first type beams from the set of spatial beams, and a second CSI-RS set transmitted by using a subset of second type beams from the set of spatial beams.14.The device of claim 13, wherein the first type beams are narrower beams with a higher gain which are intended for single-user MIMO (SU-MIMO), and the second type beams are wider beams with a lower gain which are intended for multi-user MIMO (MU-MIMO).15.A non-transitory storage medium storing at least one computer-readable instruction, the at least one computer-readable instruction, when executed by at least one processor of an electronic device, enabling the electronic device to perform at least one operation, the at least one operation comprising:performing, from a base station (BS) of the wireless communication system, transmission of a plurality of channel state information reference signals (CSI-RSs), wherein the plurality of CSI-RSs comprises two or more CSI-RS sets; andselecting a predefined number of CSI-RSs, by a user equipment (UE) in the wireless communication system, from the CSI-RS sets received from the base station, and generating the CSI based on the selected CSI-RSs, wherein the CSI comprises, for each of the selected CSI-RSs, respective parameters, including an identifier of the CSI-RS.

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