WO2025183968A1

WO2025183968A1 - Channel state information (csi) reporting management based on terminal location for multiple input multiple output (mimo) systems

Info

Publication number: WO2025183968A1
Application number: PCT/US2025/016560
Authority: WO
Inventors: Amit Kalhan; Ramon Khalona; Sairamesh Nammi
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2024-02-26
Filing date: 2025-02-20
Publication date: 2025-09-04
Anticipated expiration: 2026-08-26

Abstract

A network node sends codebook limiting information to a terminal where the codebook limiting information limits the number of antenna beams to be evaluated by the terminal based on a location of the terminal as perceived by the network node. The network node determines the perceived terminal location and determines a perceived terminal direction to the perceived terminal location. The network node generates the codebook limiting information based on the perceived terminal direction relative to the transmission antenna pattern including a plurality of antenna beams. The terminal applies the codebook limiting information to identify a subset of precoder matrix indexes (PM Is) of a codebook including a plurality of PM Is corresponding to the plurality of antenna beams. The terminal applies only the codebook information associated with the subset of PMIs to received reference signals to identify a preferred PMI and generate CSI that is transmitted to the network node.

Description

CHANNEL STATE INFORMATION (CSI) REPORTING MANAGEMENT BASED ON TERMINAL LOCATION FOR MULTIPLE INPUT MULTIPLE OUTPUT (MIMO) SYSTEMS

CLAIM OF PRIORITY

[0001] The present application claims priority to Provisional Application No. 63/557,939, entitled “Method to Reduce the Complexity for Computing Channel State Information in Extremely Large Massive MIMO Systems,” filed February 26, 2024, assigned to the assignee hereof and hereby expressly incorporated by reference in its entirety.

FIELD

[0002] This invention generally relates to wireless communications and more particularly to channel state information (CSI) reporting management based on terminal location for multiple input multiple output (MIMO) systems.

BACKGROUND

[0003] Many conventional wireless communication systems employ network nodes such as, base stations or gNBs, to transmit and receive wireless signal to and from terminals, such as user equipment (UE) devices. A network node may include an antenna array with multiple antenna elements. The antenna array is often part of an antenna system having a plurality of logical antenna ports that are mapped to the multiple antenna elements of the antenna array. Communication through the antenna array is often managed by precoding signals and adjusting parameters to manipulate the antenna pattern of the antenna array. In order to select the appropriate precoder and antenna parameters to maximize efficient communication with a terminal, a terminal measures reference signals transmitted by a network node and transmits a report to the network node. A technique employed in conventional systems includes sending Channel State Information Reference Signals (CSI-RSs) that are received and measured by the terminal where the network node sends a CSI-RS configuration message to the terminal. The CSI-RS configuration message includes Radio Resource Control (RRC) parameters that are applied to a standard-defined CSI-RS resource mapping scheme to determine the resources elements where the reference signals to be measured will be transmitted. In at least some conventional systems, the terminal receives and measures the CSI-RSs to evaluate antenna beams in order to identify at least one preferred beam. The terminal sends the CSI including identification of the at least one preferred beam to the network node where the CSI is used by the network node to select a precoder for transmission to the terminal.

SUMMARY

[0004] A network node sends codebook limiting information to a terminal where the codebook limiting information limits the number of antenna beams to be evaluated by the terminal based on a location of the terminal as perceived by the network node. The network node determines the perceived terminal location and determines a perceived terminal direction to the perceived terminal location. The network node generates the codebook limiting information based on the perceived terminal direction relative to the transmission antenna pattern including a plurality of antenna beams. The terminal applies the codebook limiting information to identify a subset of Precoding Matrix Indicators (PMIs) of a codebook including a plurality of PMIs corresponding to the plurality of antenna beams. The terminal applies only the codebook information associated with the subset of PMIs to received reference signals to identify a preferred PMI and generate channel state information (CSI) that is transmitted to the network node. The number of antenna beams evaluated by the terminal is less than the plurality of antenna beams supported by the network node.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 A is a block diagram of a communication system for an example of CSI reporting management based on a perceived terminal location of a terminal. [0006] FIG. 1 B is a block diagram for an example of CSI reporting with a limited codebook based on perceived terminal location.

[0007] FIG. 1 C is a block diagram for an example of CSI reporting with a limited codebook based on perceived terminal location where the codebook limiting information is provided as part of a CSI-RS configuration message.

[0008] FIG. 2 is a block diagram of an example of a base station suitable for use as the base station of FIG. 1 .

[0009] FIG. 3 is a block diagram of an example of a UE device suitable for use as each of the UE devices.

[0010] FIG. 4 is a message flow diagram for an example of CSI reporting with a limited codebook

[0011] FIG. 5 is a polar plot for an example of a peak beams for azimuth angles at a fixed elevation angle.

[0012] FIG. 6 is a polar plot for an example of a peak beams for elevation angles at a fixed azimuth angle.

[0013] FIG. 7 is a flow chart of an example of a method of managing CSI reporting based on a perceived location of a terminal.

[0014] FIG. 8 is a flow chart of an example of a method of CSI reporting based on a limited codebook established based on codebook limiting information received from the network where the limited codebook is based on the perceived location of the terminal as perceived by the network node.

DETAILED DESCRIPTION

[0015] As discussed above, the terminal may evaluate reference signals transmitted via various antenna beams to generate a Channel State Information (CSI) report that is transmitted to the network node. The terminal provides CSI in a CSI report transmitted in the uplink control channel where the CSI report typically includes at least a preferred Precoder Matrix Indicator (PMI), a CSI-RS Resource Indicator (CRI), a Channel Quality Indicator (CQI), a Rank Indicator (Rl), and a Layer Indicator (LI). Via RRC signaling, the network node configures the terminal for CSI reporting where the CSI can be divided into wideband and narrow band (sub-band) information. In many systems, the precoding at the network node is codebook-based where the CSI narrow band information is generated by the terminal using a codebook. Using the codebook, the terminal can explicitly identify a precoding matrix/vector with a precoding matrix indicator (PMI) based on the codebook that should be used for transmission by the network node. The codebook, therefore, includes a plurality of PMIs where the terminal applies the information associated with each PMI to received reference signals to identify at least one preferred PMI.

[0016] The precoding applied at the transmitter of the network node results in antenna beams directed in different directions including different azimuth and elevation directions. The terminal receives and measures reference signals transmitted using precoding to select the at least one preferred PMI that best identifies a preferred antenna beam. The size of the codebook and the amount of CSI depends at least partially on the number of transmit antennas. In accordance with a 3GPP NR communication specification, for example, separate codebooks are defined for various combinations of the number of transmit antennas and the number of transmission layers (also referred to as Rank Indicator (Rl)). Accordingly, the number of antenna beams that are measured and the uplink resources needed to report the CSI increases with the number of antennas (antenna elements).

[0017] Multiple-input multiple-output (MIMO) systems can significantly increase the throughput of wireless systems. As a result, MIMO is an integral part of 4th and 5th generation wireless systems. Some 5G systems employ MIMO systems with a large number of antennas which are often referred to as massive MIMO systems. Massive MIMO systems are likely to be deployed at higher frequencies where a larger number of smaller antenna elements in an array may be deployed due to the shorter wavelength of the signals. Frequencies in the range of 7-20 GHz are being considered for allocation to terrestrial communication systems, for example, and frequencies in the millimeter wave range (e g., 28/29 GHz) that are already deployed in some countries such as Japan and the USA. [0018] In conventional systems, therefore, uplink communication resources needed to provide the CSI feedback are increased to support the larger number of antenna elements. In addition, the terminal must expend additional power and time in evaluating the larger number of antenna beams to generate the CSI. In accordance with the techniques discussed herein, however, the size of the required codebook and the number of beams evaluated by the terminal are reduced compared to conventional systems. Based on the perceived location of the terminal, the network node provides codebook limiting information to the terminal resulting in a limited number of antenna beams that must be evaluated by the terminal. As discussed below, the codebook limiting information may define a limited codebook, include information that eliminates antenna beams from the codebook, or provides other information that otherwise allows the terminal to generate a subset codebook.

[0019] A network node is any apparatus, equipment, device, or combination of devices, on the network side of the communication system that is connected to the communication network or is part of communication network. Some examples of a network node include a base station, a node B, an E-UTRA Node B, Evolved Node B, eNodeB, eNB, a New Generation eNB (ng-eNB), a gNodeB (also known as a gNB) in new radio (NR) technology, a macro station, pico station, and a femto station. The network node may form, or be a part of, the radio access network (RAN) that provides a connection between the core network and terminal communication devices. A RAN may be organized into three functional blocks including a Radio Unit (RU), a Distributed Unit (DU) and a Centralized Unit (CU). The RU transmits, receives, amplifies, and digitizes radio frequency signals and typically located near, or integrated into, the antenna. The DU and CU perform computations and/or processing to send and receive digitalized radio signals to and from the core network. The DU is typically located at or near the RU and the CU may be closer to the core network. The infrastructure or connection between the RU and the DU is often referred to as fronthaul and the infrastructure or connection between the DU and the CU is often referred to as a midhaul. The communication node, therefore, may perform the functions of one or more of the RU, DU and/or CU depending on the particular implementation. [0020] A terminal communication device (terminal), such as a remote terminal and a relay terminal, is a communication device on the terminal side of the communication system and is sometimes referred to as user equipment (UE), a UE device, a terminal device, wireless mobile device, wireless communication device and other terms. Some examples of a terminal communication device include a mobile phone, a smart phone, a personal digital assistant (PDA), tablet, and laptop computer. In some situations, the terminal communication device is a machine type communication (MTC) communication device or Internet-of-Things (IOT) device. In addition, the terminal communication device may be, or may be a part of, a wearable device or a vehicle where the vehicle may be terrestrial vehicle, watercraft, or aircraft (including unmanned aerial vehicles). The terminal communication device, therefore, is any fixed, mobile, or portable equipment that performs the functions of the terminal device described herein.

[0021] FIG. 1 A is a block diagram of a communication system 100 for an example of CSI reporting management based on a perceived terminal location of a terminal 102. A network node 104 includes a transmitter 106 that is configured to transmit signals through a plurality of antennas 108. For the example, the plurality of antennas 108 are antenna elements of an antenna array that transmits transmission signals in a plurality of available antenna beams 110 based on precoding applied by a precoder 112. The precoder 112 processes signals by applying a precoding matrix or vector to a signal before transmission to direct the signal within one of the available antenna beams 110. For the example, the precoder 112 applies codebook-based precoding where a codebook includes the precoding matrix/vectors for forming the available antenna beams 110.

[0022] With conventional techniques, a terminal uses a codebook for all of the available antenna beams 110. The terminal uses the codebook to measure and evaluate the reference signals for all of the available beams 110 supported by the codebook in order to generate the CSI feedback that is transmitted to the network node 104. In accordance with the examples herein, however, the network node 104 sends codebook limiting information 114 based on the perceived location of the terminal 102 that limits the antenna beams to be measured and evaluated to a subset of antenna beams 116-118. Depending on the location determination technique and signal propagation between the network node 104 and the terminal 102, the perceived location may or may not be the same as the actual physical location of the terminal. For example, the perceived location and the physical location may be the same or nearly the same where the communication channel between the network node and the terminal is essentially line of sight with little or no scattering. Where signals transmitted from the terminal are used for determining the perceived location and the communication channel includes significant reflection, however, the perceived location may be much different from the physical location. Examples of techniques for determining the terminal location are discussed below. After determining the location or a geographical area 120 that contains the terminal location, the network node 104 determines a subset of antenna beams 116-118 that are directed to the geographical location of the terminal 102. For the examples, the network node 104 determines an azimuth angle to the terminal location (or geographical location) and an elevation angle to the terminal location (or geographical location). The angles 122 are the angles of the direction vector 123 to the terminal perceived location relative to a reference direction 124 that is consistent with a reference for the available beams 110. The direction 123 to the terminal, therefore, is a perceived direction 123 that is compared to the antenna pattern such that transmission using an antenna beam in the perceived direction is likely the best antenna beam for transmission. The single angle 122 and a single reference direction 124 shown in FIG. 1A may represent either the elevation or the azimuth. The subset of antenna beams that correspond to the angles are identified. In some situations, some antenna beams of the available antenna beams are eliminated to arrive at the subset of antenna beams 116-118 that are in the perceived direction 123 to the terminal location. For example, if the elevation angle to the perceived terminal location is determined to be 45 degrees, antenna beams with elevations angles of 90 to 180 degrees can be eliminated to arrive at subset of beams having an elevation angle within the range of 0 to 90 degrees. In some situations, the subset of beams 116-118 may be selected based on only the elevation or the azimuth.

[0023] For the example, the network node includes stored data defining the antenna pattern that indicates the directions of all the available beams. The antenna pattern is relative to reference that can be compared to the perceived direction to determine the subset of beams (candidate beams) that are most likely to provide the best communication path to the terminal.

[0024] After receiving the codebook limiting information based on the perceived terminal location 114, the terminal 102 generates, modifies an existing codebook, or otherwise establishes a limited codebook 126 at the terminal 102 that is limited to the subset of antenna beams 116-118. In some situations, the codebook information 114 may include a revised codebook. In other situations, the codebook information 114 may include information regarding which antenna beams should be excluded and/or which antenna beams should be included in the limited codebook 126 relative to the codebook for all available antenna beams 110. In FIG. 1A, the limited codebook 126 is shown as a block having numbered entries to represent the antenna beams that are supported by the limited codebook 126. For the example, the numbers represent the Precoder Matrix indexes (PMI) of a codebook. Full codebook entries 128 include the subset entries (subset PMIs) 130 and omitted entries. Therefore, the limited codebook entries 130 correspond to the subset of beams 116-118. The contents and size of a codebook generally depend on at least the Rank Indicator (Rl) and number of supported logical antenna ports. For example, in at least one revision of the 3GPP NR communication specification, separate codebooks are defined for various combinations of the number of transmit antennas and the number of transmission layers (i.e. , Rl). A total of 80 precoding vectors and matrices are defined in TS 38.214 for 4 transmit antennas (CSI- RS ports). Currently, 3GPP is discussing how the CSI-RS ports can be extended up to 128 ports. When the CSI-RS is extended to 128 port CSI-RS, the codebook needs to be extended to accommodate these many ports. Based on the principle of the initial 5G NR release (Release 15), the codebook can be extended to 128 ports. For 128 CSI-RS ports for rank of 4, for example, the full codebook 128 includes 4096 entries. In another example, the full codebook for 128 ports for Rank 2 is 8192 entries. Without limiting the codebook, the terminal 102 would need to search the parameters for 4096 precoding entries for the first example and 8192 for the second example to find the precoding matrix index (PMI). Such a requirement results in significant power consumption, memory use, and processing at the terminal 102. Therefore, with the currently available hardware/software resources with stringent delay constraints, finding rank information and the corresponding precoding matrix computation is highly complex for larger codebooks. By limiting the codebook to a subset of entries 130 based on terminal location, however, the burden at the terminal 102 is significantly reduced.

[0025] The network node 102 may determine the perceived terminal location using any of several of techniques and technique combinations. Some examples of suitable location determining techniques, include techniques based on Angle of Arrival (AoA) Estimation, Time Difference of Arrival (TDoA), techniques based on Received Signal Strength Indicator (RSSI), Machine Learning Techniques, Signal Reflection and Multipath Analysis, Reference Signal Analysis, and combinations thereof.

[0026] AoA estimation involves determining the direction from which a signal arrives at the antenna array of the network node 104. By analyzing the phase difference of the incoming signal across the elements of the antenna array, the base station can estimate the angle at which the signal is arriving. Such an approach allows positioning by receiving the reference signal at a single point and is particularly effective in environments where the signal has a clear path from the terminal to the network node. [0027] Various algorithms can be applied such as Capon’s Minimum Variance, MUSIC, ESPRIT and Matrix-Pencil method, and others to estimate the angle-of-arrival of the received signal, and the distance from the transmitting node (terminal).

[0028] TDoA techniques use the difference in arrival times of a signal at different network nodes or at different antennas of the same network node to estimate the terminal location. Such a method typically requires precise synchronization between network nodes or antennas and is useful for triangulating the position of the terminal. [0029] Although RSSI measurements do not provide directional information, variations in received signal strength as the terminal moves can be used in conjunction with signal propagation models to estimate the direction of terminal movement relative to the network node. Such methods may be less accurate than AoA or TDoA techniques but can be implemented with less complexity.

[0030] By applying machine learning models to a combination of techniques such as AoA, TDoA, RSSI, and others, the direction estimation can be continually trained to estimate the terminal’s direction. By analyzing historical data, such models can predict the terminal location and movement patterns with high accuracy. [0031] With signal reflection and multipath analysis, advanced signal processing techniques can analyze multipath components of received signals to estimate the direction to the terminal location. Such methods consider the signal reflections from various objects in the environment, which can be particularly useful in urban or indoor scenarios.

[0032] In some situations, the network node analyzes reference signals transmitted by the terminal to estimate the direction to the terminal. The phase and amplitude of a pilot signal received at different antenna elements are evaluated to estimate direction. [0033] In some situations, the network node may employ services provided by other network entities to assist in determining the perceived location of the terminal. The network node may interface with entities performing Location Management Function (LMF) and Location Services (LCS), for example. The LMF is a central entity within the 5G core network that oversees location services. LMF services may include coordinating collection of TDOA measurements and calculating a location of a terminal. The LCS entity manages the delivery of location-based services by processing positioning requests from other network entities and nodes as well as terminals. The LCS entity may coordinate with various network elements to determine the terminal’s location.

[0034] Combinations of any number of techniques discussed above may be used by the network node to determine the direction to the terminal. In addition, other techniques may also be used to estimate the terminal location and/ or the direction to the terminal location.

[0035] FIG. 1 B is a block diagram for an example of CSI reporting with a limited codebook 126 based on perceived terminal location. The example of FIG. 1 B is a continuation of the example of FIG. 1A. After receiving the codebook limiting information 114 and generating or establishing the limited codebook 126, the terminal 102 receives a CSI-RS configuration message 150 from the network node 104. For the example of FIG. 1 B, the codebook limiting information 114 is provided in a codebook limiting information message 152 separate from the CSI-RS configuration message 150. As discussed below with reference to FIG. 1 C, the codebook limiting information 114 may be provided as part of a CSI-RS configuration message is some situations. [0036] The codebook limiting information message 152 is transmitted using Radio Resource Control (RRC) signaling and messaging for the example. In other examples, the codebook limiting information message 152 is sent via Medium Access Control (MAC) layer signaling in a MAC Control Element (MAC-CE). In still other examples, the codebook limiting information message 152 may be provided by Downlink Control Information (DCI) messaging on a downlink control channel (PDCCH) or by other means.

[0037] The CSI-RS configuration message 150 includes Radio Resource Control (RRC) parameters that are applied to a standard-defined CSI-RS resource mapping scheme to determine the resources elements where the reference signals to be measured will be transmitted. The terminal 102 applies the parameters to the mapping scheme and measures the reference signals 156-158 for the limited codebook entries. In other words, the terminal 102 measures and evaluates the reference signals transmitted with precoding associated with the subset of PM Is acknowledged in the limited codebook 126. Although the example of FIG. 1 B includes three reference signals 156, 157, 158, any number of reference signals may be measured where the number of evaluated reference signals at least partially depends on the number of entries in the limited codebook 126.

[0038] The terminal 102 evaluates the reference signals 156-158 to identify at least one PMI that is associated with characteristics that best match the characteristics of an evaluated reference signal. Each reference signal that most closely matches one of the PMIs in the limited codebook is identified to select a preferred PMI. In some situations, the terminal 102 may identify more than one preferred PMI and may rank the preference. The terminal 102 sends, to the network node 104, a CSI report 160 that at least identifies one preferred PMI. For the example, the terminal 102 transmits a CSI report message 160 including the preferred PMI, a CSI-RS Resource Indicator (CRI), Channel Quality Indicator (CQI), Rank Indicator (Rl), and Layer Indicator (LI).

[0039] The Rl defines the number of possible layers for downlink transmission and corresponds to a maximum number of uncorrelated paths that the downlink transmission can use. The CRI can be used to indicate a preferred beam. The CQI conveys information about the channel quality and may be periodic or aperiodic. The LI is a parameter that conveys information about the number of spatial layers.

[0040] FIG. 1 C is a block diagram for an example of CSI reporting with a limited codebook 126 based on perceived terminal location where the codebook limiting information 114 is provided as part of a CSI-RS configuration message 170. The example of FIG. 10, therefore, is a continuation of the example of FIG. 1A and is similar to the example of FIG. 1 B except that the codebook limiting information 114 is received within the CSI-RS configuration message 170. For the example, a conventional CSI-RS configuration message is modified to include at least one field configured to convey the codebook limiting information 114.

[0041] After receiving the CSI-RS configuration message 170 with the codebook limiting information 114, the terminal 102 generates or establishes the limited codebook 126. The terminal 102 applies the RRC parameters to the standard-defined CSI-RS resource mapping scheme to determine the resources elements where the reference signals to be measured will be transmitted. The terminal 102 measures the reference signals 156-158 for the limited codebook entries and evaluates the reference signals 156-158 to identify at least one PMI that is associated with characteristics that best match the characteristics of an evaluated reference signal. Each reference signal that most closely matches one of the PMIs in the limited codebook is identified to select a preferred PMI. In some situations, the terminal 102 may identify more than one preferred PMI and may rank the preference. The terminal 102 sends, to the network node 104, a CSI report 160 that at least identifies one preferred PMI. For the example, the terminal 102 transmits a CSI report message 160 including the preferred PMI, a CSI-RS Resource Indicator (CRI), Channel Quality Indicator (CQI), Rank Indicator (Rl), and Layer Indicator (LI).

[0042] FIG. 2 is a block diagram of an example of a base station 200 suitable for use as the network node 104. The base station 200 includes electronics (controller) 204, transmitter 106, and receiver 208, and multiple antennas 108, as well as other electronics, hardware, and code. The base station 200 is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to the base station 200 and network node 104 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices. The base station 200 may be a fixed device or apparatus that is installed at a particular location at the time of system deployment. Examples of such equipment include fixed base stations or fixed transceiver stations. Although the base station may be referred to by different terms, the base station is typically referred to as a gNodeB or gNB when operating in accordance with one or more communication specifications of 3GPP. In some situations, the base station 200 may be mobile equipment that is temporarily installed at a particular location. Some examples of such equipment include mobile transceiver stations that may include power generating equipment such as electric generators, solar panels, and/or batteries. Larger and heavier versions of such equipment may be transported by trailer. During operation, however the base station remains fixed.

[0043] The electronics (controller) 204 includes any combination of hardware, software, and/or firmware for executing the functions described herein as well as facilitating the overall functionality of the base station 200. An example of suitable electronics 204 includes code running on a microprocessor or processor arrangement connected to memory. The transmitter 106 includes electronics configured to transmit wireless signals. In some situations, the transmitter 106 may include multiple transmitters. The receiver 208 includes electronics configured to receive wireless signals. In some situations, the receiver 208 may include multiple receivers. The receiver 208 may receive signals through multiple antennas or through a selected antenna of the plurality of antennas 108. The antennas 108 may include separate transmit and receive antennas. For the examples herein, the antennas 108 form an antenna array having an adjustable antenna pattern with beams that can be manipulated at least by precoding signals to be transmitted by the precoder 112.

[0044] The transmitter 106 and receiver 208 in the example of FIG. 2 perform radio frequency (RF) processing including modulation and demodulation. The receiver 208, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 106 may include filters and amplifiers as well as the precoder 112 and other antenna system components. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the base station functions. The required components may depend on the particular functionality required by the base station.

[0045] The transmitter 106 includes a modulator (not shown), and the receiver 208 includes a demodulator (not shown). The modulator modulates the signals to be transmitted as part of the downlink signals and can apply any one of a plurality of modulation orders. The demodulator demodulates any uplink signals received at the base station 200 in accordance with one of a plurality of modulation orders. The controller 204 in conjunction with the transmitter 106 apply the precoder matrix to signals transmitted through the multiple antennas 108.

[0046] The base station 200 includes a communication interface 212 for transmitting and receiving messages with other base stations and/or network entities. The communication interface 212 facilitates communication with position assistance entities such as LCS and LMF entities, for example. The communication interface 212 may be connected to a backhaul or network enabling communication with other base stations. In some situations, the link between base stations may include at least some wireless portions. The communication interface 212, therefore, may include wireless communication functionality and may utilize some of the components of the transmitter 106 and/or receiver 208.

[0047] FIG. 3 is a block diagram of an example of a use equipment (UE) device 300 suitable for use as the terminal 102. In some examples, the UE device 300 is any wireless communication device such as a mobile phone, a transceiver modem, a personal digital assistant (PDA), a tablet, or a smartphone. In other examples, the UE device 300 is a machine type communication (MTC) communication device or Internet- of-Things (IOT) device. The UE device 300, therefore is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to UE device 300 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices.

[0048] The UE device 300 includes at least electronics (controller) 302, a transmitter 304 and a receiver 306. The electronics (controller) 302 include any combination of hardware, software, and/or firmware for executing the functions described herein as well as facilitating the overall functionality of a communication device. An example of a suitable controller 302 includes code running on a microprocessor or processor arrangement connected to memory 310. The transmitter 304 includes electronics configured to transmit wireless signals. In some situations, the transmitter 304 may include multiple transmitters. The receiver 306 includes electronics configured to receive wireless signals. In some situations, the receiver 306 may include multiple receivers. The receiver 306 and transmitter 304 receive and transmit signals, respectively, through antenna 308. The antenna 308 may include separate transmit and receive antennas. In some circumstances, the antenna 308 may include multiple transmit and receive antennas.

[0049] The transmitter 304 and receiver 306 in the example of FIG. 3 perform radio frequency (RF) processing including modulation and demodulation. The receiver 306, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 304 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the communication device functions. The required components may depend on the particular functionality required by the communication device.

[0050] The transmitter 304 includes a modulator (not shown), and the receiver 306 includes a demodulator (not shown). The modulator can apply any one of a plurality of modulation orders to modulate the signals to be transmitted as part of the uplink signals. The demodulator demodulates the downlink signals in accordance with one of a plurality of modulation orders.

[0051] The UE device 300 is capable of transmitting and receiving sidelink signals to and from other UE devices as well as communicating with a base station (network node). The receiver 306 and controller 302 also measure signals transmitted by the network node to perform at least CSI reporting. In some situations, the receiver 306 and controller 302 perform measurements to determine the location of the UE device (terminal location) or assist the base station (network node) in determining the terminal location.

[0052] FIG. 4 is a message flow diagram 400 for an example of CSI reporting with a limited codebook.

[0053] At event 402, the network node 104 determines the perceived terminal location. As discussed above, the network node 104 uses a positioning technique or combination of techniques to determine the perceived location of the terminal 102 and the perceived direction from the network node to the terminal 102. For the example, the network node 104 determines the elevation and the azimuth angles of the perceived direction. In some situations, only one of the direction parameters (azimuth or elevation) is determined.

[0054] At event 404, the network node determines the candidate antenna beams based on the perceived direction to the terminal (or perceived terminal location). For the example, the network node compares the perceived direction to the directions of the available beams of the antenna pattern to select the beams that are most likely to be selected by the terminal as the beams providing the best communication path from the network node to the terminal. The selection may include dividing the available beams in groups or sectors and identifying a group or sector that includes the perceived direction to the terminal. Alternatively, or in addition, available beams not consistent with the perceived direction can be omitted from the available beams to identify the candidate beams.

[0055] At event 406, the network node 104 generates codebook limiting information that limits a codebook to a subset of beams, or a subset of indexes that identify the subset of beams, of the full codebook including indexes for all available beams. As discussed above the codebook limiting information may have any of several formats or may provide different types of information. The codebook limiting information may, for example, identify indexes that should be omitted from the full codebook or may identify the subset of indexes that should be included in the limited codebook.

[0056] At transmission 408, a codebook limiting information message including the codebook limiting information is transmitted to the terminal. The codebook limiting information message may be a CSI-RS configuration message with one or more additional fields for the codebook limiting information or may be separate message transmitted using RRC, MAC or DCI signaling. Other types of messages may be used in some circumstances.

[0057] At transmission 410, CSI-RS configuration message is transmitted to the terminal. A dashed line is used to represent the transmission 410 in FIG. 4 to indicate that the transmissions 408 and transmission 410 may be the same transmission in some examples. Accordingly, the separate CSI-RS configuration message of transmission 410 is transmitted when the codebook limiting information is not part of a CSI-RS configuration message.

[0058] At transmission 412, CSI reference signals (CSI-RSs) are transmitted. In accordance with known techniques, the network node transmits reference signals that have been precoded.

[0059] At event 414, the terminal applies the CSI-RS configuration information and the codebook limiting information to receive and evaluate the reference signals for the candidate beams. The terminal applies the CSI-RS information to receive reference signals transmitted over the resources identified in the CSI-RS configuration message to receive the reference signals. The received reference signals are compared only to the candidate beams identified in the limited codebook.

[0060] At transmission 416, a CSI report is transmitted to the network node. The terminal generates the CSI report in accordance with the CSI-RS configuration message where the CSI report identifies at least one preferred beam from the candidate beams of the limited codebook. For the example the one or more preferred beams are identified with one or more preferred PMIs. The CSI report includes other information such as Rl, CRI, CQI, and LI for the example. [0061] FIG. 5 is a polar plot 500 for an example of a peak beams for azimuth angles at a fixed elevation angle. FIG. 5 shows the beam index and the main direction for all the available beams 502 in the full codebook. The available beams 502 include the candidate beams 504 and the omitted beams 506 of the limited codebook. The candidate beams 504 are illustrated as circles with cross-hatching in FIG. 5. For the example, the available beams 502 cover azimuth angles from -180 degrees to 180 degrees and the candidate beams 504 are in the sector of angles between 0 degrees and 90 degrees. For the example of FIG. 5, the available beams 502 are divided into two groups where the candidate beams selected based on whether the perceived direction 123 of the terminal is within the section of angles between 0 and 90 degrees or with the sector of angles between 90 and 180 degrees. The number of candidate beams in the limited codebook can be reduced by increasing the number of groups or sectors. Each sector of angles can be limited to a 10-degree range instead of the 90-degree range shown in FIG. 5 to further limit the number of beams. In addition, a sector need not be fixed range with defined angles and may be a dynamically adjusted around the perceived direction 123. For example, the candidate beams may be limited to angles that are 10 degrees greater than the angle of the perceived direction to angles that are 10 degrees less than the angle of the perceived direction. Large fixed sectors may be advantageous where the network node can determine that the perceived direction of the terminal is to the left or to the right of a reference.

[0062] FIG. 6 is a polar plot 600 for an example of a peak beams for elevation angles at a fixed azimuth angle. FIG. 6 shows the beam index and the main direction for all the available beams 602 in the full codebook. The available beams 602 include the candidate beams 604 and the omitted beams 606 of the limited codebook. The candidate beams 604 are illustrated as circles with cross-hatching in FIG. 6. For the example, the available beams 602 cover elevation angles from 0 degrees to 90 degrees and the candidate beams 604 are in the sector of angles between 0 degrees and 30 degrees. The elevation angles are not necessarily relative to Earth. For example, the antenna array may be pointed down at angle of 10 degrees or more such that an elevation angle of zero degrees is actually pointing down from a tower supporting the antenna array. For the example of FIG. 6, the available beams 602 are divided into two groups where the candidate beams are selected based on whether the perceived direction 123 of the terminal is within the section of angles between 0 and 30 degrees or with the sector of angles between 30 and 90 degrees. As discussed above regarding the azimuth angles, the number of candidate beams in the limited codebook can be reduced by increasing the number of groups or sectors. Each sector of angles can be limited to a 10-degree range instead of the two ranges of 60 degrees and 30 degrees shown in FIG. 6 to further limit the number of beams. In addition, a sector need not be fixed range with defined angles and may be a dynamically adjusted around the perceived direction 123. For example, the candidate beams may be limited to angles that are 10 degrees greater than the angle of the perceived direction to angles that are 10 degrees less than the angle of the perceived direction. Large fixed sectors for elevation may be advantageous where the network node can determine that the perceived direction of the terminal is near ground level or is at a higher floor in a building.

[0063] FIG. 7 is a flow chart of an example of a method of managing CSI reporting based on a perceived location of a terminal 102. The method may be performed in a system such the system 100 discussed herein. For the example, the method is performed by a network node, such as the network node 104. The method may be performed using any of several techniques involving any combination of software, hardware, and firmware. For example, software code running on electronics including a processor, computer or other processor arrangement within the network node may facilitate the generation, formatting, reception, and transmission of signals and messages as well as facilitating measurements, evaluations and determinations. One or more of the steps may be omitted, combined, performed in parallel, or performed in a different order than that described herein or shown in FIG. 7. In still further examples, additional steps may be added that are not explicitly described in connection with the example discussed with reference to FIG. 7.

[0064] At step 702, the network node 104 determines the perceived terminal location. As discussed above, the network node 104 uses a positioning technique or combination of techniques to determine the perceived location of the terminal 102 and the perceived direction from the network node to the terminal 102. For the example, the network node 104 determines the elevation and the azimuth angles of the perceived direction. In some situations, only one of the direction parameters (azimuth or elevation) is determined.

[0065] At step 704, the network node determines the candidate antenna beams based on the perceived direction to the terminal (or perceived terminal location). For the example, the network node compares the perceived direction to the directions of the available beams of the antenna pattern to select the beams that are most likely to be selected by the terminal as the beams providing the best communication path from the network node to the terminal. The selection may include dividing the available beams in groups or sectors and identifying a group or sector that includes the perceived direction to the terminal. Alternatively, or in addition, available beams not consistent with the perceived direction can be omitted from the available beams to identify the candidate beams.

[0066] At step 706, the network node 104 generates codebook limiting information that limits a codebook to a subset of beams, or a subset of indexes that identify the subset of beams, of the full codebook including indexes for all available beams. As discussed above the codebook limiting information may have any of several formats or may provide different types of information. The codebook limiting information may, for example, identify indexes that should be omitted from the full codebook or may identify the subset of indexes that should be included in the limited codebook.

[0067] At step 708, a codebook limiting information message including the codebook limiting information is transmitted to the terminal. The codebook limiting information message may be a CSI-RS configuration message with one or more additional fields for the codebook limiting information or may be separate message transmitted using RRC, MAC or DCI signaling. Other types of messages may be used in some circumstances.

[0068] At step 710, a CSI-RS configuration message is transmitted to the terminal. In situations where the codebook limiting information is transmitted within the CSI-RS configuration message, step 708 and step 710 are performed in one step. [0069] At step 712, CSI reference signals (CSI-RSs) are transmitted. In accordance with known techniques, the network node transmits reference signals that have been precoded.

[0070] At step 714, the network node receives a CSI report from the terminal where the CSI report identifies at least one preferred beam selected from the limited codebook. For the example, the CSI report also includes Rl, CRI, CQI, and LI.

[0071] At step 716, the network node selects a precoder for data transmission to the terminal. Based on the information included in the CSI report, the network node determines the best beam for data transmission and applies the associated precoder to data transmissions to the terminal.

[0072] FIG. 8 is a flow chart of an example of a method of CSI reporting based on a limited codebook established based on codebook limiting information received from the network where the limited codebook is based on the perceived location of the terminal 102 as perceived by the network node. The method may be performed in a system such the system 100 discussed herein. For the example, the method is performed by a terminal, such as the terminal 102 or UE device 300. The method may be performed using any of several techniques involving any combination of software, hardware, and firmware. For example, software code running on electronics including a processor, computer or other processor arrangement within the network node may facilitate the generation, formatting, reception, and transmission of signals and messages as well as facilitating measurements, evaluations and determinations. One or more of the steps may be omitted, combined, performed in parallel, or performed in a different order than that described herein or shown in FIG. 8. In still further examples, additional steps may be added that are not explicitly described in connection with the example discussed with reference to FIG. 8.

[0073] At step 802, codebook limiting information is received from the network node. As discussed above, the codebook limiting information is any information that allows the terminal to establish or generate a limited codebook that supports a subset of antenna beams included in a full codebook supporting all of the available antenna beams of the antenna pattern of the network node. The codebook limiting information may be information that excludes some of the available antenna beams from the full codebook, for example. The codebook limiting information may be information that modifies the full codebook, therefore.

[0074] At step 804, the terminal receives a CSI-RS configuration message. The CSI- RS configuration information in the CSI-RS configuration message at least includes RRC parameters that can be applied to the codebook mapping scheme to determine the communication resources of reference signals. In some situations, the codebook limiting information is transmitted within the CSI-RS configuration message. As a result, step 802 and step 804 can be performed in a single step.

[0075] At step 806, the terminal applies the codebook limiting information to establish the limited codebook where the limited codebook includes a subset of beams (candidate beams) of the full codebook supporting all of the available beams.

[0076] At step 808, the CSI-RS configuration information is applied to the reference signal mapping scheme of the limited codebook to receive and evaluate the reference signals only for candidate beams. The terminal selects one or more preferred beams form the subset of beams (candidate beams) and measures other parameters to generate a CSI report which is transmitted to the network node at step 810. For the example the CSI report includes one or more PMIs, Rl, CRI, CQI, and LI. The terminal, therefore, applies the codebook limiting information and the CSI-RS information to receive and evaluate the reference signals for the candidate beams. The terminal applies the CSI-RS information to receive reference signals transmitted over the resources identified in the CSI-RS configuration message to receive the reference signals. The received reference signals are compared only to the candidate beams identified in the limited codebook.

[0077] To clearly illustrate this interchangeability of hardware, firmware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in various ways for each particular application, but such implementation decisions do not cause a departure from the scope of the present disclosure. In accordance with various embodiments, a processor, device, component, circuit, structure, machine, module, etc. can be configured to perform one or more of the functions described herein. The term "configured to" or "configured for" as used herein with respect to a specified operation or function refers to processors, devices, components, circuits, electronics, and equipment that are physically constructed, programmed, instructed and/or arranged to perform the specified operation or function. Furthermore, the various illustrative logical blocks, modules, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that can include a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), other electronics or combinations thereof. (ASIC), a field programmable gate array (FPGA) or other programmable logic device, or any combination thereof. The logical blocks, electronics, and circuits can further include antennas and/or transceivers to communicate with various components within the network or within the device. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration to perform the functions described herein.

[0078] When implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium. Thus, the steps of a method or algorithm disclosed herein can be implemented as software stored on a computer- readable medium. Computer readable media includes both computer storage media and communication media, including any medium that can be enabled to transfer a computer program or code from one place to another. A storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0079] Therefore, the methods and apparatus of this invention may take the form, at least partially, of program logic or program code (i.e., instructions) embodied in tangible media, such as a machine-readable storage medium. When the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. The methods and apparatus of the present invention may also be embodied in the form of program code that is transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission. When the program code is received and loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique apparatus that operates analogously to specific logic circuits.

[0080] Additionally, memory or other storage, as well as communication components, may be employed in embodiments of the present disclosure. It will be appreciated that, for clarity purposes, the above description has described embodiments of the present disclosure with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements or domains may be used without detracting from the present disclosure. For example, functionality illustrated to be performed by separate processing logic elements, or controllers, may be performed by the same processing logic element, or controller. Therefore, references to specific functional units are only references to a suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization. [0081] Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Claims

1 . A method comprising: receiving, from a network node at a terminal, codebook limiting information identifying a subset of antenna beams of a plurality of available antenna beams characterized by a full codebook, the codebook limiting information based on at least one of two direction parameters comprising an azimuth direction from the network node to a perceived terminal location of the terminal and an elevation direction from the network node to the perceived terminal location; measuring reference signals transmitted only over the subset of antenna beams to identify at least one preferred antenna beam; and transmitting precoder information identifying the at least one preferred antenna beam.

2. The method of claim 1 , wherein the codebook limiting information is a limited codebook identifying the subset of antenna beams.

3. The method of claim 2, wherein the precoder information comprises a Precoding Matrix Indicator (PM I) based on a codeword in the limited codebook.

4. The method of claim 1 , wherein the codebook limiting information indicates omitted antenna beams to be excluded from the plurality of antenna beams to identify the subset of antenna beams.

5. The method of claim 1 , wherein the codebook information is based on the azimuth direction and the elevation direction.

6. The method of claim 1 , wherein the perceived terminal location is a geographical location of the terminal.

7. The method of claim 1 , wherein transmitting the precoder information comprises transmitting a Channel State Information (CSI) report including the precoder information.

8. The method of claim 7, wherein the CSI report comprises a CSI-RS Resource Indicator (CRI), a Channel Quality Indicator (CQI), a Rank Indicator (Rl), and a Layer Indicator (LI).

9. The method of claim 1 , wherein receiving the codebook limiting information comprises receiving a Channel State Information Reference Signal (CSI-RS) configuration message comprising the codebook limiting information.

10. The method of claim 1 , wherein receiving the codebook limiting information comprises receiving the codebook limiting information via Radio Resource Control (RRC) signaling.

11 . The method of claim 1 , wherein receiving the codebook limiting information comprises receiving the codebook limiting information via Medium Access Control (MAC) layer signaling in a MAC Control Element (MAC-CE).

12. The method of claim 1 , wherein receiving the codebook limiting information comprises receiving the codebook limiting information via Downlink Control Information (DCI) messaging on a physical downlink control channel (PDCCH).

13. A method comprising: determining a perceived terminal location of a terminal; identifying a subset of antenna beams of a plurality of available antenna beams supported by a full codebook; transmitting, from a network node to the terminal, codebook limiting information identifying the subset of antenna beams, the codebook limiting information based on at least one of two direction parameters comprising an azimuth direction from the network node to the perceived terminal location and an elevation direction from the network node to the perceived terminal location.

14. The method of claim 13, further comprising receiving precoder information identifying at least one preferred beam of the subset of beams.

15. The method of claim 14, wherein the precoder information comprises a Precoding Matrix Indicator (PM I) based on a codeword in the limited codebook.

16. The method of claim 13, wherein the codebook limiting information is based on the azimuth direction and the elevation direction.

17. The method of claim 13, wherein the codebook limiting information is a limited codebook identifying the subset of antenna beams.

18. The method of claim 13, wherein the codebook limiting information indicates omitted antenna beams to be excluded from the plurality of antenna beams to identify the subset of antenna beams.

19. The method of claim 13, wherein the perceived terminal location is a geographical location of the terminal.

20. The method of claim 15, wherein transmitting the precoder information comprises transmitting a Channel State Information (CSI) report including the precoder information.

21 . The method of claim 20, wherein the CSI report comprises a CSI-RS Resource Indicator (CRI), a Channel Quality Indicator (CQI), a Rank Indicator (Rl), and a Layer Indicator (LI).

22. The method of claim 13, wherein transmitting the codebook limiting information comprises transmitting a Channel State Information Reference Signal (CSI-RS) configuration message comprising the codebook limiting information.

23. The method of claim 13, wherein transmitting the codebook limiting information comprises transmitting the codebook limiting information via Radio Resource Control (RRC) signaling.

24. The method of claim 13, wherein transmitting the codebook limiting information comprises transmitting the codebook limiting information via Medium Access Control (MAC) layer signaling in a MAC Control Element (MAC-CE).

25. The method of claim 13, wherein transmitting the codebook limiting information comprises transmitting the codebook limiting information via Downlink Control Information (DCI) messaging on a physical downlink control channel (PDCCH).

26. A terminal comprising: a receiver configured to receive, from a network node, codebook limiting information identifying a subset of antenna beams of a plurality of available antenna beams characterized by a full codebook, the codebook limiting information based on at least one of two direction parameters comprising an azimuth direction from the network node to a perceived terminal location of the terminal and an elevation direction from the network node to the perceived terminal location, the receiver configured to measure reference signals transmitted only over the subset of antenna beams to identify at least one preferred antenna beam; and a transmitter configured to transmit, to the network node, precoder information identifying the at least one preferred antenna beam.