Patent Description:
In wireless communication systems, such as <NUM> NR systems, multiple transmission and reception point (multi-TRP) technology may be used for implementing transmissions to and from a particular g Node B (gNB) or similar base station (BS). The TRPs may be any of a number of wireless devices such as macro-cells, small cells, pico-cells, femto-cells, remote radio heads (RRHs), or relay nodes as examples. Multi-TRP technology engenders a gNB that includes dynamic coordination between multiple numbers of TRPs to provide joint scheduling and transmissions and receptions. A wireless device, such as a user equipment (UE), may be then served by multiple TRPs to improve its signal transmission/reception, which results in increased throughput, among other things.

Feedback for determining and reporting channel state information from UEs to a radio access network in such systems, such as feedback through channel state information (CSI) and precoding matrix indicators (PMIs), in particular, includes the UE measuring various radio channel state parameters and reporting the results to the network (i.e., the gNB) with the CSI feedback, which is then used to determine the precoders and/or beamforming in the gNB. Further, multi-TRP systems are a development of massive multiple-input, multiple-output (MIMO) systems wherein the number of gNB or base station (BS) antennas is increased with multiple TRPs. Since the number of feedback bits for codebooks (i.e., a set of precoders or precoding matrices) scales linearly with the number of antennas in a MIMO system, the overhead on the uplink from UE to gNB is increased due to the greater amount of feedback information.

The document <CIT> discloses CSI reporting in a multi-TRP system according to the preamble of claim <NUM>.

<NPL>) discloses Type-II feedback employing spatial domain and frequency domain basis matrices.

Accordingly, as the demand for mobile broadband access continues to increase, research and development continues to advance wireless communication technologies, including reducing CSI (e.g., PMI) overhead to improve and enhance the user experience with mobile communications.

According to a first aspect, a method for a user equipment (UE) to report channel state information (CSI) for a plurality of transmission and reception points (TRPs) in a communication system is disclosed. The method includes measuring downlink (DL) channels received from a plurality of TRPs, and determining a plurality of transmission hypotheses based on the measured DL channels from the plurality of TRPs. Furthermore, the method includes transmitting channel state information (CSI) to a network in the communication system, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain basis matrix.

In another aspect, an apparatus for wireless communication is disclosed. The apparatus includes means for measuring downlink (DL) channels received in a user equipment (UE) from a plurality of transmission and reception points (TRPs) in a communication system, and means for determining a plurality of transmission hypotheses based on the measured DL channels from the plurality of TRPs. Also, the apparatus includes means for transmitting channel state information (CSI) to a network in the communication system, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain basis matrix.

According to yet another aspect, a non-transitory computer-readable medium storing computer-executable code is disclosed. The code includes code for causing a computer to measure downlink (DL) channels received in a user equipment (UE) from a plurality of transmission and reception points (TRPs) in a communication system, and determine a plurality of transmission hypotheses based on the measured DL channels from the plurality of TRPs. The code also includes code for causing a computer to transmit channel state information (CSI) to a network in the communication system, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain basis matrix.

In yet another, unclaimed, aspect, an apparatus for wireless communication is disclosed that includes at least one processor, a transceiver communicatively coupled to the at least one processor, and a memory communicatively coupled to the at least one processor. The at least one processor is further configured to measure downlink (DL) channels received from a plurality of transmission and reception points (TRPs) in a communication system, and determine a plurality of transmission hypotheses based on the measured DL channels from the plurality of TRPs. Moreover, the at least one processor is configured to transmit channel state information (CSI) to a network in the communication system, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain basis matrix.

In yet another aspect, a method for a base station to configure channel state information (CSI) reporting in a multiple transmission and reception point (TRP) communication system is disclosed. The method includes configuring a UE to determine a plurality of transmission hypotheses based on the measured downlink (DL) channels from a plurality of TRPs. Additionally, the method includes receiving CSI from the UE, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain matrix.

According to another aspect, an apparatus for wireless communication is disclosed including means for configuring a user equipment (UE) to determine a plurality of transmission hypotheses based on measured downlink (DL) channels from a plurality of TRPs. Additionally, the apparatus includes means for receiving channel state information (CSI) from the UE, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain basis matrix.

In still another aspect, a non-transitory computer-readable medium storing computer-executable code is disclosed. The code includes code for causing a computer to configure a user equipment (UE) to determine a plurality of transmission hypotheses based on measured downlink (DL) channels from a plurality of TRPs. The code further includes code for causing a computer to receive channel state information (CSI) from the UE, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain basis matrix.

According to yet one final, unclaimed, aspect, an apparatus for wireless communication is disclosed including at least one processor, a transceiver communicatively coupled to the at least one processor, and a memory communicatively coupled to the at least one processor. The at least one processor is further configured to configure a user equipment (UE) to determine a plurality of transmission hypotheses based on measured downlink (DL) channels from a plurality of TRPs. Further, the at least one processor is also configured to receive channel state information (CSI) from the UE, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain basis matrix.

Other aspects, features, and embodiments will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments in conjunction with the accompanying figures. While features may be discussed relative to certain embodiments and figures below, all embodiments can include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments discussed herein.

While aspects and embodiments are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Innovations described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, packaging arrangements. For example, embodiments and/or uses may come about via integrated chip embodiments and other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, AI-enabled devices, etc.). While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described innovations may occur. Implementations may range a spectrum from chip-level or modular components to non-modular, non-chip-level implementations and further to aggregate, distributed, or OEM devices or systems incorporating one or more aspects of the described innovations. In some practical settings, devices incorporating described aspects and features may also necessarily include additional components and features for implementation and practice of claimed and described embodiments. For example, transmission and reception of wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including antenna, RF-chains, power amplifiers, modulators, buffer, processor(s), interleaver, adders/summers, etc.). It is intended that innovations described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, end-user devices, etc. of varying sizes, shapes and constitution.

As discussed above, CSI feedback, particularly when used in multiple-TRP systems and/or massive MIMO schemes, can cause the CSI overhead to increase. Accordingly, the present disclosure provides a CSI feedback scheme to report PMI for multiple transmission hypotheses jointly or combined. It is noted here that a transmission hypothesis for a UE includes transmitting a signal from a certain one or more TRPs to the UE. This scheme provides improved efficiency for a wireless network as compared with schemes that separately report the PMI for each multi-TRP transmission hypothesis. Joint or combined PMI reporting of multiple multi-TRP transmission hypothesis may significantly reduce the PMI feedback payload thereby improving spectrum efficiency and enhancing coverage for the wireless network.

The radio access network <NUM> is further illustrated supporting wireless communication for multiple mobile apparatuses. A mobile apparatus may be referred to as user equipment (UE) in 3GPP standards, but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. A UE may be an apparatus (e.g., a mobile apparatus) that provides a user with access to network services.

Within the present document, a "mobile" apparatus need not necessarily have a capability to move, and may be stationary. The term mobile apparatus or mobile device broadly refers to a diverse array of devices and technologies. UEs may include a number of hardware structural components sized, shaped, and arranged to help in communication; such components can include antennas, antenna arrays, RF chains, amplifiers, one or more processors, etc. electrically coupled to each other. For example, some non-limiting examples of a mobile apparatus include a mobile, a cellular (cell) phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal computer (PC), a notebook, a netbook, a smartbook, a tablet, a personal digital assistant (PDA), and a broad array of embedded systems, e.g., corresponding to an "Internet of things" (IoT). A mobile apparatus may additionally be an automotive or other transportation vehicle, a remote sensor or actuator, a robot or robotics device, a satellite radio, a global positioning system (GPS) device, an object tracking device, a drone, a multi-copter, a quad-copter, a remote control device, a consumer and/or wearable device, such as eyewear, a wearable camera, a virtual reality device, a smart watch, a health or fitness tracker, a digital audio player (e.g., MP3 player), a camera, a game console, etc. A mobile apparatus may additionally be a digital home or smart home device such as a home audio, video, and/or multimedia device, an appliance, a vending machine, intelligent lighting, a home security system, a smart meter, etc. A mobile apparatus may additionally be a smart energy device, a security device, a solar panel or solar array, a municipal infrastructure device controlling electric power (e.g., a smart grid), lighting, water, etc.; an industrial automation and enterprise device; a logistics controller; agricultural equipment; military defense equipment, vehicles, aircraft, ships, and weaponry, etc. Still further, a mobile apparatus may provide for connected medicine or telemedicine support, e.g., health care at a distance. Telehealth devices may include telehealth monitoring devices and telehealth administration devices, whose communication may be given preferential treatment or prioritized access over other types of information, e.g., in terms of prioritized access for transport of critical service data, and/or relevant QoS for transport of critical service data.

Referring now to <FIG>, by way of example and without limitation, a schematic illustration of a RAN <NUM> is provided. In some examples, the RAN <NUM> may be the same as the RAN <NUM> described above and illustrated in <FIG>. The geographic area covered by the RAN <NUM> may be divided into cellular regions (cells) that can be uniquely identified by a user equipment (UE) based on an identification broadcasted from one access point or base station. <FIG> illustrates macrocells <NUM>, <NUM>, and <NUM>, and a small cell <NUM>, each of which may include one or more sectors (not shown). A sector is a sub-area of a cell. All sectors within one cell are served by the same base station. A radio link within a sector can be identified by a single logical identification belonging to that sector. In a cell that is divided into sectors, the multiple sectors within a cell can be formed by groups of antennas with each antenna responsible for communication with UEs in a portion of the cell.

Within the RAN <NUM>, the cells may include UEs that may be in communication with one or more sectors of each cell. Further, each base station <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may be configured to provide an access point to a core network <NUM> (see <FIG>) for all the UEs in the respective cells. For example, UEs <NUM> and <NUM> may be in communication with base station <NUM>; UEs <NUM> and <NUM> may be in communication with base station <NUM>; UEs <NUM> and <NUM> may be in communication with base station <NUM> by way of RRH <NUM>; UE <NUM> may be in communication with base station <NUM>; and UE <NUM> may be in communication with mobile base station <NUM>. In some examples, the UEs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM> may be the same as the UE/scheduled entity <NUM> described above and illustrated in <FIG>.

In a further aspect of the RAN <NUM>, sidelink signals may be used between UEs without necessarily relying on scheduling or control information from a base station. For example, two or more UEs (e.g., UEs <NUM> and <NUM>) may communicate with each other using peer to peer (P2P) or sidelink signals <NUM> without relaying that communication through a base station (e.g., base station <NUM>). In a further example, UE <NUM> is illustrated communicating with UEs <NUM> and <NUM>. Here, the UE <NUM> may function as a scheduling entity or a primary sidelink device, and UEs <NUM> and <NUM> may function as a scheduled entity or a non-primary (e.g., secondary) sidelink device. In still another example, a UE may function as a scheduling entity in a device-to-device (D2D), peer-to-peer (P2P), or vehicle-to-vehicle (V2V) network, and/or in a mesh network. In a mesh network example, UEs <NUM> and <NUM> may optionally communicate directly with one another in addition to communicating with the scheduling entity <NUM>. Thus, in a wireless communication system with scheduled access to time-frequency resources and having a cellular configuration, a P2P configuration, or a mesh configuration, a scheduling entity and one or more scheduled entities may communicate utilizing the scheduled resources.

In the radio access network <NUM>, the ability for a UE to communicate while moving, independent of its location, is referred to as mobility. The various physical channels between the UE and the radio access network are generally set up, maintained, and released under the control of an access and mobility management function (AMF, not illustrated, part of the core network <NUM> in <FIG>), which may include a security context management function (SCMF) that manages the security context for both the control plane and the user plane functionality, and a security anchor function (SEAF) that performs authentication.

In various aspects of the disclosure, a radio access network <NUM> may utilize DL-based mobility or UL-based mobility to enable mobility and handovers (i.e., the transfer of a UE's connection from one radio channel to another). In a network configured for DL-based mobility, during a call with a scheduling entity, or at any other time, a UE may monitor various parameters of the signal from its serving cell as well as various parameters of neighboring cells. Depending on the quality of these parameters, the UE may maintain communication with one or more of the neighboring cells. During this time, if the UE moves from one cell to another, or if signal quality from a neighboring cell exceeds that from the serving cell for a given amount of time, the UE may undertake a handoff or handover from the serving cell to the neighboring (target) cell. For example, UE <NUM> (illustrated as a vehicle, although any suitable form of UE may be used) may move from the geographic area corresponding to its serving cell <NUM> to the geographic area corresponding to a neighbor cell <NUM>. When the signal strength or quality from the neighbor cell <NUM> exceeds that of its serving cell <NUM> for a given amount of time, the UE <NUM> may transmit a reporting message to its serving base station <NUM> indicating this condition. In response, the UE <NUM> may receive a handover command, and the UE may undergo a handover to the cell <NUM>.

In a network configured for UL-based mobility, UL reference signals from each UE may be utilized by the network to select a serving cell for each UE. In some examples, the base stations <NUM>, <NUM>, and <NUM>/<NUM> may broadcast unified synchronization signals (e.g., unified Primary Synchronization Signals (PSSs), unified Secondary Synchronization Signals (SSSs) and unified Physical Broadcast Channels (PBCH)). The UEs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may receive the unified synchronization signals, derive the carrier frequency and slot timing from the synchronization signals, and in response to deriving timing, transmit an uplink pilot or reference signal. The uplink pilot signal transmitted by a UE (e.g., UE <NUM>) may be concurrently received by two or more cells (e.g., base stations <NUM> and <NUM>/<NUM>) within the radio access network <NUM>. Each of the cells may measure a strength of the pilot signal, and the radio access network (e.g., one or more of the base stations <NUM> and <NUM>/<NUM> and/or a central node within the core network) may determine a serving cell for the UE <NUM>. As the UE <NUM> moves through the radio access network <NUM>, the network may continue to monitor the uplink pilot signal transmitted by the UE <NUM>. When the signal strength or quality of the pilot signal measured by a neighboring cell exceeds that of the signal strength or quality measured by the serving cell, the network <NUM> may handover the UE <NUM> from the serving cell to the neighboring cell, with or without informing the UE <NUM>.

In some aspects of the disclosure, the scheduling entity and/or scheduled entity may be configured for beamforming and/or multiple-input multiple-output (MIMO) technology. <FIG> illustrates an example of a wireless communication system <NUM> supporting MIMO. In a MIMO system, a transmitter <NUM> includes multiple transmit antennas <NUM> (e.g., N transmit antennas) and a receiver <NUM> includes multiple receive antennas <NUM> (e.g., M receive antennas). Thus, there are N × M signal paths <NUM> from the transmit antennas <NUM> to the receive antennas <NUM>. Each of the transmitter <NUM> and the receiver <NUM> may be implemented, for example, within a scheduling entity <NUM>, a scheduled entity <NUM>, or any other suitable wireless communication device.

The use of such multiple antenna technology enables the wireless communication system to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data, also referred to as layers, simultaneously on the same time-frequency resource. The data streams may be transmitted to a single UE to increase the data rate or to multiple UEs to increase the overall system capacity, the latter being referred to as multi-user MIMO (MU-MIMO). This is achieved by spatially precoding each data stream (i.e., multiplying the data streams with different weighting and phase shifting) and then transmitting each spatially precoded stream through multiple transmit antennas on the downlink. The spatially precoded data streams arrive at the UE(s) with different spatial signatures, which enables each of the UE(s) to recover the one or more data streams destined for that UE. On the uplink, each UE transmits a spatially precoded data stream, which enables the base station to identify the source of each spatially precoded data stream.

The number of data streams or layers corresponds to the rank of the transmission. In general, the rank of the MIMO system <NUM> is limited by the number of transmit or receive antennas <NUM> or <NUM>, whichever is lower. In addition, the channel conditions at the UE, as well as other considerations, such as the available resources at the base station, may also affect the transmission rank. For example, the rank (and therefore, the number of data streams) assigned to a particular UE on the downlink may be determined based on the rank indicator (RI) transmitted from the UE to the base station. The RI may be determined based on the antenna configuration (e.g., the number of transmit and receive antennas) and a measured signal-to-interference-and-noise ratio (SINR) on each of the receive antennas. The RI may indicate, for example, the number of layers that may be supported under the current channel conditions. The base station may use the RI, along with resource information (e.g., the available resources and amount of data to be scheduled for the UE), to assign a transmission rank to the UE.

In Time Division Duplex (TDD) systems, the UL and DL are reciprocal, in that each uses different time slots of the same frequency bandwidth. Therefore, in TDD systems, the base station may assign the rank for DL MIMO transmissions based on UL SINR measurements (e.g., based on a Sounding Reference Signal (SRS) transmitted from the UE or other pilot signal). Based on the assigned rank, the base station may then transmit the CSI-RS with separate C-RS sequences for each layer to provide for multilayer channel estimation. From the CSI-RS, the UE may measure the channel quality across layers and resource blocks and feed back the CQI and RI values to the base station for use in updating the rank and assigning REs for future downlink transmissions.

In the simplest case, as shown in <FIG>, a rank-<NUM> spatial multiplexing transmission on a 2x2 MIMO antenna configuration will transmit one data stream from each transmit antenna <NUM>. Each data stream reaches each receive antenna <NUM> along a different signal path <NUM>. The receiver <NUM> may then reconstruct the data streams using the received signals from each receive antenna <NUM>.

The air interface in the radio access network <NUM> may utilize one or more multiplexing and multiple access algorithms to enable simultaneous communication of the various devices. For example, <NUM> NR specifications provide multiple access for UL transmissions from UEs <NUM> and <NUM> to base station <NUM>, and for multiplexing for DL transmissions from base station <NUM> to one or more UEs <NUM> and <NUM>, utilizing orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP). In addition, for UL transmissions, <NUM> NR specifications provide support for discrete Fourier transform-spread-OFDM (DFT-s-OFDM) with a CP (also referred to as single-carrier FDMA (SC-FDMA)). However, within the scope of the present disclosure, multiplexing and multiple access are not limited to the above schemes, and may be provided utilizing time division multiple access (TDMA), code division multiple access (CDMA), frequency division multiple access (FDMA), sparse code multiple access (SCMA), resource spread multiple access (RSMA), or other suitable multiple access schemes. Further, multiplexing DL transmissions from the base station <NUM> to UEs <NUM> and <NUM> may be provided utilizing time division multiplexing (TDM), code division multiplexing (CDM), frequency division multiplexing (FDM), orthogonal frequency division multiplexing (OFDM), sparse code multiplexing (SCM), or other suitable multiplexing schemes.

<FIG> illustrates, by way of example and without limitation, a schematic illustration of a portion <NUM> of a RAN utilizing multi-TRPs. In this example, two exemplary transmission and reception points (TRP-<NUM> and TRP-<NUM>) are shown at <NUM> and <NUM>, but application of the presently disclosed CSI reporting schemes is not limited to this specific number of TRPs. In this example, the two TRPs <NUM>, <NUM> are used to effectuate communications for a single gNB <NUM>, which is shown communicatively coupled to the TRPs <NUM>, <NUM>. In particular, the gNB <NUM> can transmit from different TRPs (e.g., TRPs <NUM> or <NUM>) to a UE <NUM> on multiple DL channels (e.g., physical downlink shared channel (PDSCH) links), which enhances diversity gain, DL system capacity, and/or DL cell coverage. In turn, the UE <NUM> may measure and/or determine channel state information (CSI) that is transmitted on UL channels (e.g., a physical uplink control channel (PUCCH)) to one or more of the TRPs <NUM>, <NUM> to the network (e.g., the gNB <NUM>). As will be discussed in more detail later, the present disclosure provides for a CSI scheme that jointly reports multiple CSI or PMI hypotheses from a UE (e.g., UE <NUM>) to the network or gNB (e.g., gNB <NUM>).

With reference back to the system of <FIG>, it is noted that the transmitter <NUM>, within the context of a multi-TRP system such as that illustrated in <FIG>, may constitute a gNB and that multiple TRPs may be used to implement the gNB. Furthermore, each TRP (e.g., <NUM>, <NUM>) may respectively employ MIMO technology where each TRP transmits using multiple antennas. Still further, each TRP <NUM>, <NUM> may employ a same precoding that is determined based on the CSI feedback from the UE for each of the multiple TRPs, but are not necessarily limited to such.

It is noted here that precoding, also known as transmit beamforming, involves the canceling of multiuser interference by multiplying transmit signals for DL transmissions by precoding matrixes or vectors. The derivation of these precoding matrixes is based on the CSI information including PMI that is received from one or more UEs, and which will be explained in more detail later. Precoding is an interference pre-cancelation technique that exploits the spatial degrees of freedom offered by the multiple transmit antennas to simultaneously serve UEs with one or more antennas.

The transmissions of CSI and PMI reporting disclosed herein may each be transmitted over radio access technologies using carriers that may be organized into frames, subframes, and slots. Various aspects of the present disclosure will be described with reference to an OFDM waveform, schematically illustrated in <FIG>. Within the present disclosure, a frame refers to a duration of <NUM> for wireless transmissions, with each frame consisting of <NUM> subframes of <NUM> each. On a given carrier, there may be one set of frames in the UL, and another set of frames in the DL.

Referring now to <FIG>, an expanded view of an exemplary DL subframe <NUM> is illustrated, showing an OFDM resource grid <NUM>. However, as those skilled in the art will readily appreciate, the PHY transmission structure for any particular application may vary from the example described here, depending on any number of factors. Here, time is in the horizontal direction with units of OFDM symbols; and frequency is in the vertical direction with units of subcarriers or tones.

The resource grid <NUM> may be used to schematically represent time-frequency resources for a given antenna port. That is, in a MIMO implementation with multiple antenna ports available, a corresponding multiple number of resource grids <NUM> may be available for communication. The resource grid <NUM> is divided into multiple resource elements (REs) <NUM>. An RE, which is <NUM> subcarrier × <NUM> symbol, is the smallest discrete part of the time-frequency grid, and contains a single complex value representing data from a physical channel or signal. Depending on the modulation utilized in a particular implementation, each RE may represent one or more bits of information. In some examples, a block of REs may be referred to as a physical resource block (PRB) or more simply a resource block (RB) <NUM>, which contains any suitable number of consecutive subcarriers in the frequency domain. In one example, an RB may include <NUM> subcarriers, a number independent of the numerology used. In some examples, depending on the numerology, an RB may include any suitable number of consecutive OFDM symbols in the time domain. Within the present disclosure, it is assumed that a single RB such as the RB <NUM> entirely corresponds to a single direction of communication (either transmission or reception for a given device).

A UE generally utilizes only a subset of the resource grid <NUM>. An RB may be the smallest unit of resources that can be allocated to a UE. Thus, the more RBs scheduled for a UE, and the higher the modulation scheme chosen for the air interface, the higher the data rate for the UE.

Each subframe <NUM> (e.g., a <NUM> subframe) may consist of one or multiple adjacent slots. In the example shown in <FIG>, one subframe <NUM> includes four slots <NUM>, as an illustrative example. In some examples, a slot may be defined according to a specified number of OFDM symbols with a given cyclic prefix (CP) length. For example, a slot may include <NUM> or <NUM> OFDM symbols with a nominal CP. Additional examples may include mini-slots having a shorter duration (e.g., <NUM>, <NUM>, <NUM>, or <NUM> OFDM symbols). These mini-slots may in some cases be transmitted occupying resources scheduled for ongoing slot transmissions for the same or for different UEs.

An expanded view of one of the slots <NUM> illustrates the slot <NUM> including a control region <NUM> and a data region <NUM>. In general, the control region <NUM> may carry control channels (e.g., PDCCH), and the data region <NUM> may carry data channels (e.g., PDSCH or PUSCH). Of course, a slot may contain all DL, all UL, or at least one DL portion and at least one UL portion. The simple structure illustrated in <FIG> is merely exemplary in nature, and different slot structures may be utilized, and may include one or more of each of the control region(s) and data region(s).

Although not illustrated in <FIG>, the various REs <NUM> within an RB <NUM> may be scheduled to carry one or more physical channels, including control channels, shared channels, data channels, etc. Other REs <NUM> within the RB <NUM> may also carry pilots or reference signals. These pilots or reference signals may provide for a receiving device to perform channel estimation of the corresponding channel, which may enable coherent demodulation/detection of the control and/or data channels within the RB <NUM>.

In a DL transmission, the transmitting device (e.g., the scheduling entity <NUM>) may allocate one or more REs <NUM> (e.g., within a control region <NUM>) to carry DL control information <NUM> including one or more DL control channels that generally carry information originating from higher layers, such as a physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), etc., to one or more scheduled entities <NUM>. In addition, DL REs may be allocated to carry DL physical signals that generally do not carry information originating from higher layers. These DL physical signals may include a primary synchronization signal (PSS); a secondary synchronization signal (SSS); demodulation reference signals (DM-RS); phase-tracking reference signals (PT-RS); channel-state information reference signals (CSI-RS); etc..

The synchronization signals PSS and SSS (collectively referred to as SS), and in some examples, the PBCH, may be transmitted in an SS block that includes <NUM> consecutive OFDM symbols, numbered via a time index in increasing order from <NUM> to <NUM>. In the frequency domain, the SS block may extend over <NUM> contiguous subcarriers, with the subcarriers being numbered via a frequency index in increasing order from <NUM> to <NUM>. Of course, the present disclosure is not limited to this specific SS block configuration. Other nonlimiting examples may utilize greater or fewer than two synchronization signals; may include one or more supplemental channels in addition to the PBCH; may omit a PBCH; and/or may utilize nonconsecutive symbols for an SS block, within the scope of the present disclosure.

The PDCCH may carry downlink control information (DCI) for one or more UEs in a cell. This can include, but is not limited to, power control commands, scheduling information, a grant, and/or an assignment of REs for DL and UL transmissions.

In an UL transmission, a transmitting device (e.g., a scheduled entity <NUM>) may utilize one or more REs <NUM> to carry UL control information <NUM> (UCI). The UCI can originate from higher layers via one or more UL control channels, such as a physical uplink control channel (PUCCH), a physical random access channel (PRACH), etc., to the scheduling entity <NUM>. Further, UL REs may carry UL physical signals that generally do not carry information originating from higher layers, such as demodulation reference signals (DM-RS), phase-tracking reference signals (PT-RS), sounding reference signals (SRS), etc. In some examples, the control information <NUM> may include a scheduling request (SR), i.e., a request for the scheduling entity <NUM> to schedule uplink transmissions. Here, in response to the SR transmitted on the control channel <NUM>, the scheduling entity <NUM> may transmit downlink control information <NUM> that may schedule resources for uplink packet transmissions.

UL control information may also include hybrid automatic repeat request (HARQ) feedback such as an acknowledgment (ACK) or negative acknowledgment (NACK), channel state information (CSI), or any other suitable UL control information. HARQ is a technique well-known to those of ordinary skill in the art, wherein the integrity of packet transmissions may be checked at the receiving side for accuracy, e.g., utilizing any suitable integrity checking mechanism, such as a checksum or a cyclic redundancy check (CRC). If the integrity of the transmission confirmed, an ACK may be transmitted, whereas if not confirmed, a NACK may be transmitted. In response to a NACK, the transmitting device may send a HARQ retransmission, which may implement chase combining, incremental redundancy, etc..

In addition to control information, one or more REs <NUM> (e.g., within the data region <NUM>) may be allocated for user data or traffic data. Such traffic may be carried on one or more traffic channels, such as, for a DL transmission, a physical downlink shared channel (PDSCH); or for an UL transmission, a physical uplink shared channel (PUSCH).

In order for a UE to gain initial access to a cell, the RAN may provide system information (SI) characterizing the cell. This system information may be provided utilizing minimum system information (MSI), and other system information (OSI). The MSI may be periodically broadcast over the cell to provide the most basic information required for initial cell access, and for acquiring any OSI that may be broadcast periodically or sent on-demand. In some examples, the MSI may be provided over two different downlink channels. For example, the PBCH may carry a master information block (MIB), and the PDSCH may carry a system information block type <NUM> (SIB1). In the art, SIB1 may be referred to as the remaining minimum system information (RMSI).

OSI may include any SI that is not broadcast in the MSI. In some examples, the PDSCH may carry a plurality of SIBs, not limited to SIB1, discussed above. Here, the OSI may be provided in these SIBs, e.g., SIB2 and above.

The channels or carriers described above and illustrated in <FIG> and <FIG> are not necessarily all the channels or carriers that may be utilized between a scheduling entity <NUM> and scheduled entities <NUM>, and those of ordinary skill in the art will recognize that other channels or carriers may be utilized in addition to those illustrated, such as other traffic, control, and feedback channels.

According to various 3GPP new radio specifications, including Releases <NUM> and <NUM>, various codebooks (or precoding matrices or precoders) include two types (e.g., Type <NUM> and Type <NUM>) that have been specified for the channel state information (CSI) feedback in the support of advanced MIMO operation. Both types of codebook are constructed from <NUM>-D discrete Fourier transform (DFT) based grid of beams, and enable the CSI feedback for beam selection as well as PSK based co-phase combining between two polarizations. One type of codebook includes what is known as a "Type II" or "Type-<NUM>" codebook. Type-<NUM> codebook based CSI feedback enables more explicit channel feedback than a Type-<NUM> based CSI feedback in that both beam direction and amplitude are reported by the UE in the CSI feedback. Type-<NUM> codebook based CSI feedback reports the wideband and subband amplitude information of the selected beams. As a result, a more accurate CSI may be obtained from the Type-<NUM> codebook based CSI feedback so that better precoded DL MIMO transmissions can be employed by the network and a channel can be characterized with more accurate spatial and amplitude information. In one particular example, the Type-<NUM> codebook was specified without frequency compression for CSI feedback. An example of this type of Type-<NUM> codebook without frequency compression is illustrated in <FIG>.

As shown in <FIG>, a precoding matrix or vector (which is interchangeable with "precoder") W <NUM> for the wideband or a frequency subband is determined by a matrix product of CSI feedback information received from a UE and shown generally at box <NUM>. The CSI feedback information in box <NUM> consists of a spatial domain basis matrix W<NUM> <NUM> and a coefficient matrix W<NUM> <NUM>. In particular, the spatial domain basis matrix W<NUM> <NUM> is a P x <NUM> matrix consisting of an L number of beams (i.e., Z columns) per polarization group. In this exemplary case, since there are two polarization groups, there are a total of <NUM> beams. The value P is equal to 2N<NUM>N<NUM> where N<NUM> and N<NUM> are the numbers of horizontal and vertical antenna elements, respectively.

Matrix <NUM> is a <NUM> × Nlayer coefficient matrix containing coefficients for each beam's contribution in each layer. In matrix <NUM>, one column represents one layer, and one element <NUM> therein represents one beam within this layer. The value Nlayer represents the number of spatial layers, which corresponds to the number of columns in matrix <NUM>.

Since the spatial domain basis matrix <NUM> is a P × <NUM> matrix and the coefficient matrix <NUM> is <NUM> x Nlayer matrix, the product or quantization of these matrices yields a precoding matrix <NUM> having a size of P × Nlayer. When the precoding matrix <NUM> is wideband, the component matrixes W<NUM> <NUM> and W<NUM> <NUM> are both wideband. On the other hand, when the precoding matrix <NUM> is subband, the spatial domain basis matrix W<NUM> <NUM> is still wideband, but the coefficient matrix W<NUM> <NUM> is subband. A UE reports (or issues a report of) the quantization results of W<NUM> <NUM> and W<NUM> <NUM> as PMI in the CSI over UL channels to the network (e.g., the gNB). In turn, the network or gNB uses the quantization results to determine the precoder matrix W based on the product of W<NUM> <NUM> and coefficient matrix W<NUM> <NUM> as is illustrated in <FIG>.

Other Type <NUM> codebooks include frequency compression to further reduce the CSI overhead. An example of this type of Type-<NUM> codebook with frequency compression is illustrated in <FIG>, where for one layer the precoding matrix is determined by exploiting the sparsity of both the spatial and frequency domains.

As shown in <FIG>, a precoding matrix or vector W <NUM> for a spatial layer is determined by a matrix product of CSI feedback information shown generally at box <NUM>. Box <NUM> includes a spatial domain basis matrix W<NUM> <NUM>, a coefficient matrix W̃<NUM> <NUM>, and a frequency domain basis matrix <MAT> <NUM>. In particular, the spatial domain basis matrix W<NUM> <NUM> is a P x <NUM> matrix consisting of an L number of beams (i.e., Z columns) per polarization group. As there are two polarization groups, there are a total of <NUM> beams. The value P is equal to <NUM>N<NUM>N<NUM> where N<NUM> and N<NUM> are the numbers of horizontal and vertical antenna elements, respectively.

The coefficient matrix W̃<NUM> <NUM> consists of linear combination coefficients including amplitude and phase, where each element represents the coefficient of a tap for a beam. This matrix <NUM> is a <NUM> x M matrix, wherein M is the number of frequency-domain compression basis vectors. The frequency domain basis matrix <MAT> <NUM> is a M x N3 matrix consisting of an N<NUM> number of subbands where each row is a basis vector. The matrix <NUM> is used to perform compression in the frequency domain. For example, the basis vectors in frequency domain basis matrix <MAT> <NUM> are derived from a certain number of columns in a DFT matrix. A UE then reports (or issues a report of) the quantization results of W<NUM> <NUM>, coefficient matrix W̃<NUM> <NUM>, and frequency domain basis matrix <MAT> <NUM> as PMI in the CSI over UL channels to the gNB. In turn, the network or gNB uses the quantization results to determine the precoder matrix W based on the product of W<NUM> <NUM>, coefficient matrix W̃<NUM> <NUM>, and frequency domain basis matrix <MAT> <NUM>, as is illustrated in <FIG>.

When the CSI feedback schemes discussed in <FIG> and <FIG> are utilized in a multi-TRP scenario, the amount of CSI overhead significantly increases. In particular, in order to optimize TRP selection and precoding determination, a UE needs to provide CSI feedback for various transmission hypotheses. Knowing the CSI for multiple transmission hypotheses is beneficial for a gNB to be able to decide a proper DL transmission mode that optimally addresses all aspects of the network (e.g., spectrum efficiency, energy efficiency, fairness, service QoS, etc.).

Of further note here, a transmission hypothesis contains a set of signal TRPs and a set of interference TRPs. Since the constructions of signal TRPs or interference TRPs are various, the number of possible transmission hypotheses increases significantly with the number of TRPs. For example, when a gNB connects TRP-<NUM> and TRP-<NUM> (e.g., <NUM> and <NUM> in <FIG>), then the possible transmission hypotheses include: <NUM>) transmitting a signal from TRP-<NUM> without interference; <NUM>) transmitting a signal from TRP-<NUM> without interference; <NUM>) transmitting signals from TRP-<NUM> and TRP-<NUM>; <NUM>) transmitting a signal from TRP-<NUM> with interference from TRP-<NUM>; and/or <NUM>) transmitting s signal from TRP-<NUM> with interference from TRP-<NUM>. In this case, if UE follows reports CSI separately for each of these transmission hypotheses, the CSI payload may increase greatly. Such an increase makes it is quite difficult for a UE to feed back such a large amount of CSI via the UL channels. Yet further, it is noted that typically the largest portion within a CSI report is PMI, especially if a Type-<NUM> codebook PMI is applied. Thus, in order to reduce the CSI payload, an effective way reduce the CSI payload is to reduce the constituent PMI payload. Accordingly, aspects of the present disclosure seek to provide schemes that reduce the PMI feedback amount, particularly in cases where a UE is required to feed back CSI that covers multiple multi-TRP hypotheses.

In an aspect, the present disclosure provides schemes where a UE may be configured (such as through RRC messaging from the gNB) to jointly report a Type-<NUM> codebook based PMI for a plurality of transmission hypotheses. In this scheme, a UE is configured to measure the channels for all concerned TRPs in the multi-TRP system. The UE then reports the PMI within the CSI to the network (i.e., a gNB). The reporting may be based on the whether the Type-<NUM> codebook is without frequency compression (e.g., the example of <FIG>) or with frequency compression (e.g., the example of <FIG>) as will be discussed in more detail below.

In particular, for a type II codebook without frequency compression, such as was discussed in connection with <FIG>, the UE may be configured to first report a spatial domain basis matrix that is shared by or common to all transmission hypotheses of the plurality of transmission hypotheses. The UE then reports a wideband or a list of per-subband coefficient matrixes respectively for each transmission hypothesis, wherein the product of the spatial domain basis matrix and the coefficient matrix constitutes a DL precoding matrix. As an example, <FIG> illustrates that the DL precoding matrix <NUM> W may be the product of a common spatial domain basis matrix that is common for all transmission hypotheses W<NUM> <NUM> and also a coefficient matrix W<NUM> <NUM>. The coefficient matrix <NUM> may be a wideband coefficient matrix or a list of subband coefficient matrixes, for each referred transmission hypothesis.

In an aspect, it is noted that in a CSI report configuration determined by network (e.g., a gNB), the UE may be configured to report the PMI for a plurality of transmission hypotheses, based on identical spatial domain basis matrix and respective coefficient matrixes of the Type-<NUM> codebook without frequency compression. For these transmission hypotheses, in an aspect all of the concerned TRPs may be divided into two sets: (<NUM>) a signal TRP set in which each TRP acts as a signal TRP at least in one transmission hypothesis (the size is denoted as NTRP), and (<NUM>) an interference TRP set in which each TRP does not act as a signal TRP in any transmission hypothesis.

Based on the above CSI report configuration, a UE is configured to measure radio channels of the concerned TRPs. In a first portion of the PMI (i.e., PMI Part <NUM> that includes the spatial domain basis matrixes), the UE then is configured to calculate and report a common, joint, or shared spatial domain basis matrix that optimally matches with the coefficient matrixes of all transmission hypotheses. In an aspect, the common spatial domain basis matrix is composed of a list of matrixes corresponding to all signal TRPs included in the CSI report configuration. For example, the spatial domain basis matrix <MAT>. Moreover, the UE may be configured to report the quantization of spatial domain basis matrix W<NUM>. In particular, a UE can report the quantization of the matrixes <MAT> through <MAT>.

Moreover, according to other aspects it is noted that in order to limit the size of CSI payload, the network (e.g., gNB) may be configured to regulate some of the parameters that are used for CSI reporting by the UE. In one example, a gNB may configure a parameter L_ind<IMG>vidual, which means that the number of columns in a spatial domain basis matrix (which is also equivalent to the number of spatial domain beams) of each spatial domain basis matrix <MAT> is equal to the L_individual, where n is constrained by the range <NUM>≤n≤NTRP.

In another example, the gNB may configure a parameter L_all where the sum of the number of columns (equivalent to the number of spatial domain beams) of each spatial domain basis matrix <MAT> is set equal to the value L_all. In still another example of parameter regulation, a gNB may configure a parameter L_(max,individual), which means that the number of columns (equivalent to the number of spatial domain beams) of each spatial domain basis matrix <MAT> should be not larger than this value L_(max,individual). In still another example, a gNB may configure a parameter L_(max,all), where the sum of the number of columns (equivalent to the number of spatial domain beams) of each spatial domain basis matrix <MAT> should not be larger than L_(max,all).

As mentioned above, a UE may be configured to calculate a spatial domain basis matrix W<NUM> that optimally matches with the coefficient matrixes of all transmission hypotheses. In one exemplary option, this calculation may be performed by individually calculating the matrixes <MAT> through <MAT> that respectively matches with a channel response matrix of each TRP in the signal TRP set assuming there is no co-transmission from other TRPs. In a second alternative option, the calculation may be performed for each transmission hypothesis by first calculating a list of matrixes that best match the respective transmission hypothesis. For example, for a Transmission Hypothesis <NUM>, the calculation includes the transmitting signals from TRP1 and TRP2, and then calculating a <MAT> and a <MAT> that best matches the transmission hypothesis. After calculating the list of matrixes, the calculation then further includes integrating the resultant matrixes of all transmission hypotheses for each TRP (i.e., combining the different columns ). For example, assuming an M number of hypotheses, the integration would be the column combination as represented by a spatial domain basis matrix <MAT> <MAT>. It will be appreciated that the first calculation option <NUM> has lower complexity, but that the second, alternate option will yield better performance.

For another portion of the PMI (i.e., PMI Part <NUM> that includes the coefficient matrixes), the UE may be configured to calculate and report a coefficient matrix W<NUM> for each TRP and each transmission hypothesis, where the calculation is based on the calculated common spatial domain basis matrix. Based on the particular CSI report configuration, the UE will report either a wideband coefficient matrix or a list of subband coefficient matrixes for each referred transmission hypothesis that is configured in the CSI report configuration. As an example, a UE may report a wideband coefficient matrix <MAT> or a list of subband matrixes <MAT>, where i is in the range of <NUM>≤i≤Nsubband for TRP <NUM> and transmission hypothesis <NUM>. This resultant matrix may be then quantized so that the CSI payload is reduced.

In some other aspects, in order to reduce the CSI payload, the coefficient matrixes of two transmission hypotheses for one TRP that have some relationship, shared characteristics, or commonalities may be reduced to reporting only one matrix in the payload. For example, given a scenario where coefficient matrix <MAT> then only one of these matrixes need be reported in the CSI payload. In another example, columns from one coefficient matrix can be used to construct another coefficient matrix such as a <MAT> being composed of one or more columns of coefficient matrix <MAT>. Of further note, in the instances where this reduction of CSI is employed, it is noted that since the gNB configures the CSI reporting, the gNB will recognize that the reception of only one coefficient matrix means that the coefficient matrix <MAT>, as one example.

In further aspects, for a Type-<NUM> codebook with frequency compression, such as was discussed in connection with <FIG>, the CSI reporting scheme may include reporting, during Part <NUM> of the PMI, a spatial domain basis matrix that is shared by or are common to all transmission hypotheses similar to the methods discussed above. Additionally, in a codebook with frequency compression, the Part <NUM> reporting also includes reporting a frequency domain matrix that is shared by or is common to all transmission hypotheses. Additionally, the UE may be configured to report a list of per-layer coefficient matrixes for each transmission hypothesis, respectively, where the product of the spatial domain basis matrix, the coefficient matrixes, and the frequency domain basis matrix constitutes a DL precoding matrix W. As an example, <FIG> illustrates that the DL precoding matrix <NUM> W may be the product of a common spatial domain basis matrix W<NUM> that is common for all TRP hypotheses <NUM>, a coefficient matrix W̃<NUM> <NUM>, and a common frequency domain basis matrix Wf <NUM>. The coefficient matrix <NUM> may be for each TRP and each transmission hypothesis.

According to aspects, for another CSI report configuration, a gNB may configure a UE to report PMI for a plurality of multi-TRP transmission hypotheses, based on an identical spatial domain basis matrix (i.e., a matrix with shared or common spatial domain characteristics across the plurality of hypotheses), an identical frequency domain basis matrix (i.e., a matrix with shared or common frequency domain characteristics across the plurality of hypotheses), and respective coefficient matrixes of Type-<NUM> codebook with frequency compression.

Based on above CSI report configuration, a UE may be configured to measure radio channels of the concerned TRPs, and then, for PMI Part <NUM>, calculate and report a common spatial domain basis matrix that optimally matches with the coefficient matrixes of all of the plurality of transmission hypotheses. In some examples, the common spatial domain basis matrix W<NUM> and the common frequency domain basis matrix Wf may be composed of a list of matrixes corresponding to all signal TRPs included in the CSI report configuration. For example, <MAT>, and <MAT>. The UE may be configured to then report the quantization of W<NUM> and Wf. In particular, the UE can report the quantization of <MAT>, <MAT>, respectively.

In some aspects, in order to limit the size of the CSI payload, a network (e.g., gNB) may regulate some of the parameters for CSI reporting. The regulated parameters for the common spatial domain basis matrix W<NUM> that were discussed previously for a Type-<NUM> codebook without frequency compression are equally applicable to a Type-<NUM> codebook with frequency regulation. Additionally, other parameters for the frequency domain basis matrix Wf may be regulated according a number of various schemes. In one example, a network (e.g., gNB) may configure a parameter L'individual, which means that the number of columns (which are equivalent to the number of frequency-domain beams) of each frequency domain basis matrix <MAT> is equal to the L'individual parameter where n is in the range of <NUM> ≤ n ≤ NTRP.

In another example, the network (e.g., a gNB) may configure a parameter L'all, which means that the sum of the number of columns (which is equivalent to the number of frequency-domain beams) of each frequency-domain basis matrix <MAT> is equal to Lall. In yet another example, the network (e.g., a gNB) may configure a parameter L'max,individual, which means that the number of columns (equivalent to the number of frequency-domain beams) of each frequency-domain basis matrix <MAT> should be not larger than L'max,individual. In still another example, the network (e.g., gNB) may configure a parameter L'max,all, which means that the sum of the number of columns (equivalent to the number of frequency-domain beams) of each frequency-domain basis matrix <MAT> should be not be set larger than L'max,all.

The methodology for calculating the spatial domain basis matrix W<NUM> and the frequency domain basis matrix Wf to optimally match with the coefficient matrixes for all transmission hypotheses can be performed in a manner similar to the instance of a Type-<NUM> codebook without frequency compression as discussed earlier. In particular, this calculation may include calculating the spatial domain or frequency domain basis matrix for each TRP based on its channel response matrix assuming there is no co-transmission. In another alternative, this calculation may include calculating the spatial domain or frequency domain basis matrix for each TRP and each transmission hypothesis, and then integrating (e.g., combining) the sub-matrixes for each TRP and all transmission hypotheses.

Furthermore, for Type-<NUM> codebook schemes with frequency compression, the determination of the Part <NUM> PMI (i.e., the calculation of the coefficient matrix W̃<NUM>) may be based on the calculated common spatial domain basis matrix and the common frequency domain basis matrix, wherein a UE calculates and reports the coefficient matrix W̃<NUM> for each TRP and each transmission hypothesis. In particular, dependent on the CSI report configuration, a UE may be configured to report a list of per-layer coefficient matrixes for each referred transmission hypothesis that is configured in the CSI report configuration. Of note here, it is not necessary to differentiate between wideband and subband for Type-<NUM> codebook with frequency compression.

As an example of the calculation of the coefficient matrix W̃<NUM> a UE reports a list of matrixes <MAT>, where j is in the range of <NUM> ≤ j ≤ Nlayer, for TRP <NUM> and transmission hypothesis <NUM>. The resultant matrix is quantized so that the payload is reduced.

In some other examples for reducing the CSI payload, the coefficient matrixes of two transmission hypotheses for one TRP having some relationship, similarity, equivalency, or commonality may be utilized to reduce payload by either only reporting one or placing shared matrix columns or rows in a same matrix. For example if <MAT>, then only one coefficient matrix need be reported. In another example, the coefficient matrix <MAT> may be composed of a plurality of columns of <MAT>, or <MAT> may be composed of a plurality of rows of <MAT>, or <MAT> may be composed of both a plurality of columns and a plurality of rows of <MAT>.

<FIG> is a block diagram illustrating an example of a hardware implementation for a base station <NUM> employing a processing system <NUM>. For example, the base station <NUM> may be a gNB or a TRP as illustrated in any one or more of <FIG>, <FIG>, <FIG>, and/or <NUM>. In other aspects, the base station <NUM> may represent an amalgamation or composite of two or more TRPs and shown simply as one implemented gNB for sake of convenience.

The base station <NUM> may be implemented with a processing system <NUM> that includes one or more processors <NUM>. Examples of processors <NUM> include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, the base station <NUM> may be configured to perform any one or more of the functions described herein. That is, the processor <NUM>, as utilized in a base station <NUM>, may be used to implement any one or more of the processes and procedures described below and illustrated in <FIG>.

In this example, the processing system <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> communicatively couples together various circuits including one or more processors (represented generally by the processor <NUM>), a memory <NUM>, and computer-readable media (represented generally by the computer-readable medium <NUM>). The bus <NUM> may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface <NUM> provides an interface between the bus <NUM> and a transceiver <NUM>. The transceiver <NUM> provides a communication interface or means for communicating with various other apparatus over a transmission medium. Depending upon the nature of the apparatus, a user interface <NUM> (e.g., keypad, touch screen, display, speaker, microphone, joystick) may also be provided. Of course, such a user interface <NUM> is optional, and may be omitted in some examples, such as in the present case of a base station <NUM>.

In some aspects of the disclosure, the processor <NUM> may include UE configuration circuitry <NUM> that is configured for various functions, including, for example, configuring a UE for CSI reporting in accordance with the methodologies disclosed herein. For example, the UE configuration circuitry <NUM> may be configured to implement one or more of the functions described below in relation to <FIG>, including, e.g., block <NUM>. Additionally, the UE configuration circuitry <NUM> may configure a UE to report for a Type-<NUM> codebook based PMI feed for a number of multi-TRP hypotheses as was discussed earlier, and further for either frequency compression or non-frequency compression codebooks. In still further aspects, the UE configuration circuitry <NUM> may interface with radio resource control (RRC) layers and cause the CSI configuration to be communicated via RRC messaging to the UE.

In some other aspects of the disclosure, the processor <NUM> may also include CSI reporting parameter regulation circuitry <NUM> that is configured for various functions, including, for example, regulating one or more parameters for CSI reporting in accordance with the methodologies disclosed herein. In particular, circuitry <NUM> may be configured to limit the CSI payload size by setting parameters affecting the various sizes of the PMI matrixes, such as the parameters Lindividual , Lall , Lmax,individual, Lmax,all, L'individual, L'all, Lmax,individual, and L'max,all, discussed before.

One or more processors <NUM> in the processing system may execute software. The software may reside on a computer-readable medium <NUM>. The computer-readable medium <NUM> may be a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a card, a stick, or a key drive), a random access memory (RAM), a read only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium <NUM> may reside in the processing system <NUM>, external to the processing system <NUM>, or distributed across multiple entities including the processing system <NUM>. The computer-readable medium <NUM> may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

In one or more examples, the computer-readable storage medium <NUM> may include UE configuration instructions or software <NUM> configured for various functions, including, for example, affording the gNB to configure a UE for CSI reporting in accordance with the various methods disclosed herein. For example, the instructions or software <NUM> may be configured to implement one or more of the functions described below in relation to <FIG>, including, e.g., block <NUM>. Additionally, the UE configuration instructions or software <NUM>, when executed by processor <NUM>, for example, may configure a UE to report for a Type-<NUM> codebook based PMI feed for a number of multi-TRP hypotheses as was discussed earlier, and further for either frequency compression or non-frequency compression codebooks. In still further aspects, the UE configuration circuitry <NUM> may interface with radio resource control (RRC) layers and cause the CSI configuration to be communicated via RRC messaging to the UE.

In one or more examples, the computer-readable storage medium <NUM> may further include CSI reporting parameter regulation instructions or software <NUM> configured for various functions, including, regulating one or more parameters for CSI reporting in accordance with the methodologies disclosed herein. In particular, instructions or software <NUM>, when executed by a processor such as processor <NUM>, may be configured to limit the CSI payload size by setting parameters affecting the various sizes of the PMI matrixes, such as the parameters Lindividual , Lall , Lmax,individual, Lmax,all, L'individual, L'all, L'max,individual, and L'max,all, discussed earlier.

<FIG> is a conceptual diagram illustrating an example of a hardware implementation for an exemplary UE <NUM> employing a processing system <NUM>. In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system <NUM> that includes one or more processors <NUM>. For example, the UE <NUM> may be a user equipment (UE) as illustrated in any one or more of <FIG>, <FIG>, <FIG>, and/or <NUM>.

The processing system <NUM> may be substantially the same as the processing system <NUM> illustrated in <FIG>, including a bus interface <NUM>, a bus <NUM>, memory <NUM>, a processor <NUM>, and a computer-readable medium <NUM>. Furthermore, the UE <NUM> may include a user interface <NUM> and a transceiver <NUM> substantially similar to those described above in connection with <FIG>. That is, the processor <NUM>, as utilized in a UE <NUM>, may be used to implement any one or more of the processes described below and illustrated in <FIG>.

In some aspects of the disclosure, the processor <NUM> may include CSI/PMI reporting circuitry <NUM> configured for various functions, including, for example, determining the PMI parts for reporting/transmission to the gNB (e.g., base station <NUM> in <FIG>), and determining the particular CSI reporting based on whether the codebook being used in a Type-<NUM> codebook with or without frequency compression. Additionally, the CSI/PMI reporting circuit <NUM> may include measuring the DL channels from two or more TRPs in a multi-TRP system, wherein the measurements are used to determine/calculate the various spatial domain basis, frequency domain basis, and coefficient matrixes. For example, the CSI/PMI reporting circuitry <NUM> may be configured to implement one or more of the functions described below in relation to <FIG>, including, e.g., block <NUM> or <NUM>.

In some other aspects of the disclosure, the processor <NUM> may include matrix calculation circuitry <NUM> configured for various functions, including, for example, determining and/or calculating the various matrixes that are reported in the CSI, including Part <NUM> and Part <NUM> information as discussed earlier. Additionally, the matrix calculation circuit may account for the various parameter regulations determined by the network, such those set by circuitry <NUM> or instructions <NUM> as discussed above. Additionally, the CSI/PMI reporting circuit <NUM> may assist in determining or calculating the various spatial domain basis, frequency domain basis, and coefficient matrixes.

In one or more examples, the computer-readable storage medium <NUM> may include CSI/PMI reporting instructions or software <NUM> configured for various functions, including, for example, determining the PMI parts for reporting/transmission to the gNB (e.g., base station <NUM> in <FIG>), and determining the particular CSI reporting based on whether the codebook being used in a Type-<NUM> codebook with or without frequency compression. Additionally, the CSI/PMI reporting circuit <NUM> may include measuring the DL channels from two or more TRPs in a multi-TRP system, wherein the measurements are used to determine/calculate the various spatial domain basis, frequency domain basis, and coefficient matrixes. For example, the CSI/PMI reporting circuitry <NUM> may be configured to implement one or more of the functions described below in relation to <FIG>, including, e.g., block <NUM> or <NUM>.

In one or more examples, the computer-readable storage medium <NUM> may further include matrix calculation instructions or software <NUM> configured for various functions, including, determining and/or calculating the various matrixes that are reported in the CSI, including Part <NUM> and Part <NUM> information as discussed earlier. Additionally, the matrix calculation circuit may account for the various parameter regulations determined by the network, such those set by circuitry <NUM> or instructions <NUM> as discussed above.

<FIG> is a flow chart illustrating an exemplary method <NUM> for reporting CSI in a UE for a plurality of TRPs in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the method <NUM> may be carried out by the UE <NUM> illustrated in <FIG>. In some examples, the method <NUM> may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block <NUM>, method <NUM> includes measuring downlink (DL) channels received from a plurality of TRPs. After measurement in block <NUM>, method <NUM> includes determining a plurality of transmission hypotheses based on the measured DL channels from the plurality of TRPs as shown at block <NUM>.

Next, method <NUM> includes transmitting a CSI to a network in the communication system, where the CSI includes a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least once coefficient matrix based on the spatial domain basis matrix as shown in block <NUM>. It is noted that the processes of method <NUM> may be utilized for both Type-<NUM> codebooks, whether the codebook is using frequency compression or not.

According to further aspects, the PMI of method <NUM> may further include at least one of a wideband or a list of per subband coefficient matrixes for each respective transmission hypothesis of the plurality of hypotheses. Further, the PMI may include at least one frequency domain basis matrix that is common to all of the plurality of transmission hypotheses as was discussed earlier with respect to <FIG>.

According to further aspects, it is noted that method <NUM> may include receiving one or more further transmission hypotheses concerning the TRPs from one or more of the TRPs (or gNB) in the communication system. Thus, the UE may receive the one or more further transmission hypotheses concerning the TRPs from one or more of the plurality of TRPs. In turn, the UE may then determine the plurality of transmission hypotheses based, in part, on the one or more further transmission hypotheses received from at least one TRP (or gNB).

Moreover, method <NUM> may further include matching the common spatial-domain basis matrix with a plurality of coefficient matrixes corresponding to all transmission hypotheses. In a particular aspect, matching may include matching the common spatial domain basis matrix and the common frequency domain basis matrix with the plurality of coefficient matrixes corresponding to all transmission hypotheses including the common spatial domain basis matrix and the common frequency domain basis matrix respectively comprising a list of spatial domain basis matrixes and a list of frequency domain basis matrixes corresponding to the plurality of TRPs.

In yet further aspects, method <NUM> may include restricting the size of the spatial domain basis matrix based on CSI parameter restrictions received from at least one gNB or base station, as was discussed earlier. The CSI parameter restrictions may include one or more of: (<NUM>) limiting a number of columns in the spatial domain basis matrix to a set number; (<NUM>) limiting the number of columns in the spatial domain basis matrix to be equal to or less than a maximum number; (<NUM>) limiting a sum of the columns in the spatial domain basis matrix to a set value; and (<NUM>) limiting the sum of columns in the spatial domain basis matrix to be equal to or less than a maximum value.

Also, method <NUM> may include restricting the size of the at least one frequency domain basis matrix based on CSI parameter restrictions received from at least one gNB or base station. These CSI parameter restrictions may include at least one of: (<NUM>) limiting a number of columns in the at least one frequency domain basis matrix to a set number; (<NUM>) limiting the number of columns in the at least one frequency domain basis matrix to be equal to or less than a maximum number; (<NUM>) limiting a sum of the columns in the at least one frequency domain basis matrix to a set value; and (<NUM>) limiting the sum of columns in the at least one frequency domain basis matrix to be equal to or less than a maximum value.

In yet further aspects, method <NUM> may include determining if two or more transmission hypotheses for one TRP have a commonality between respective coefficient matrixes, and reducing a size of the CSI when determining that the two or more transmission hypotheses for one TRP have a commonality between respective coefficient matrixes.

<FIG> is a flow chart illustrating an exemplary method <NUM> for configuring CSI in a UE in a communication system having a plurality of TRPs in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the method <NUM> may be carried out by the base station <NUM> illustrated in <FIG>. In some examples, the method <NUM> may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block <NUM>, method <NUM> includes configuring a UE to determine a plurality of transmission hypotheses based on the measured DL channels from a plurality of TRPs. This CSI configuration may further include setting restrictions on the size of the various matrixes as was discussed earlier.

Further, method <NUM> includes receiving the CSI from the UE, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain matrix as shown in block <NUM>.

In one configuration, the apparatus <NUM> or <NUM> for wireless communication includes means for measuring downlink (DL) channels received in a user equipment (UE) from a plurality of transmission and reception points (TRPs) in a communication system, means for determining a plurality of transmission hypotheses based on the measured DL channels from the plurality of TRPs; and means for transmitting channel state information (CSI) to a network in the communication system, the CSI including a precoding matrix indicator (PMI) having at least a spatial domain basis matrix that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix that is based on the spatial domain basis matrix. In one aspect, the aforementioned means may be the processor(s) <NUM> or <NUM> shown in <FIG> and <FIG> configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.

Of course, in the above examples, the circuitry included in the processors <NUM> or <NUM> is merely provided as an example, and other means for carrying out the described functions may be included within various aspects of the present disclosure, including but not limited to the instructions stored in the computer-readable storage medium <NUM> or <NUM>, or any other suitable apparatus or means described in any one of the <FIG>, <FIG>, <FIG>, and/or <NUM>, and utilizing, for example, the processes and/or algorithms described herein in relation to <FIG> and/or <NUM>.

The apparatus, devices, and/or components illustrated in <FIG>, <FIG>, and <FIG> may be configured to perform one or more of the methods, features, or steps described herein.

Claim 1:
A method for a user equipment, UE (<NUM>, <NUM>), to report channel state information, CSI, for a plurality of transmission and reception points, TRPs, in a communication system, the method comprising:
measuring (<NUM>) downlink, DL, channels received from a plurality of TRPs; determining (<NUM>) a plurality of transmission hypotheses based on the measured DL channels from the plurality of TRPs; and
transmitting (<NUM>) channel state information, CSI, to a network in the communication system, the CSI including a precoding matrix indicator, PMI, characterized by the PMI having at least a spatial domain basis matrix (<NUM>) that is common to all of the plurality of transmission hypotheses and at least one coefficient matrix (<NUM>) that is based on the spatial domain basis matrix (<NUM>).