WO2021097589A1

WO2021097589A1 - Optimization of channel state feedback (csf) report

Info

Publication number: WO2021097589A1
Application number: PCT/CN2019/119080
Authority: WO
Inventors: Zhanyi Liu; Sharon Levy; Parisa CHERAGHI; Yicheng SHEN
Original assignee: Qualcomm Incorporated
Priority date: 2019-11-18
Filing date: 2019-11-18
Publication date: 2021-05-27

Abstract

Aspects of the disclosure relate to optimizing a channel state feedback (CSF) report to include a fixed rank indicator (RI) based on the network-assigned rank. In some examples, a user equipment (UE) may monitor the rank assigned to the UE by a base station over a period of time. When the rank remains unchanged over the period of time, the UE can select a fixed RI for inclusion in the CSF report. The fixed RI may correspond to the rank assigned to the UE over the period of time. In some examples, the UE may initiate monitoring of the rank when the base station has enabled a sounding reference signal (SRS) switch feature. The UE may further include a fixed precoding matrix indicator (PMI) in the CSF report. Other aspects, features, and embodiments are also claimed and described.

Description

OPTIMIZATION OF CHANNEL STATE FEEDBACK (CSF) REPORT

TECHNICAL FIELD

The technology discussed below relates generally to wireless communication networks, and more particularly, to optimizing of the channel state feedback (CSF) report. Some embodiments and techniques enable and provide communication devices, methods, and systems to include a fixed rank indicator (RI) in the CSF report when the rank assigned by the network remains unchanged over a period of time.

INTRODUCTION

In wireless communication systems, such as those specified under standards for 5G New Radio (NR) , an access point (e.g., a base station) may communicate with a user equipment (UE) (e.g., a smartphone) . The communication can utilize a modulation and coding scheme (MCS) , rank, and precoding matrix selected based on an estimate of the channel between the base station and the UE. To assist the UE in estimating the channel, the base station may transmit one or more reference signals, such as channel state information –reference signals (CSI-RS) , to the UE. After channel estimation, the UE may return a channel state feedback (CSF) report indicating the quality of the channel to the base station.

The CSF report may include, for example, a channel quality indicator (CQI) that indicates to the base station an MCS to use for transmissions to the UE. The CSF report may further include a rank indicator (RI) that indicates the rank (e.g., the number of data streams) for the base station to utilize for downlink communications to the UE and a precoding matrix indicator (PMI) that indicates the precoding matrix for the base station to utilize for downlink communications to the UE.

As the demand for mobile broadband access continues to increase, research and development continue to advance communication technologies, including technologies for optimizing the CSF report in particular, not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.

BRIEF SUMMARY OF SOME EXAMPLES

The following presents a summary of one or more aspects of the present disclosure, in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated features of the disclosure and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in a form as a prelude to the more detailed description that is presented later.

According to some aspects, techniques discussed below enable and provide for communication components (e.g., UEs, smartphones, etc. ) to optimize the CSF report based on network operations. For example, a UE may select a fixed RI for inclusion in the CSF report when the rank assigned to the UE by the network remains unchanged over a period of time. In some examples, the UE may further select a fixed PMI when the precoding matrix assigned to the UE by the network remains unchanged over the period of time.

Various aspects of the disclosure relate to optimizing the CSF report to include the fixed RI based on the network-assigned rank. In some examples, a scheduled entity (e.g., a UE) may monitor the rank assigned to the UE by a scheduling entity (e.g., a base station) over a period of time, which may include, for example, two or more slots. When the rank remains unchanged over the period of time, the UE can select a fixed RI for inclusion in the CSF report. The fixed RI may correspond to the rank assigned to the UE by the base station over the period of time. The UE may then estimate a downlink wireless channel between the base station and the UE and identify the CQI for inclusion in the CSF report based on the downlink channel estimate and the fixed RI.

The UE may further select a fixed or variable PMI for inclusion in the CSF report. In some examples, the UE may select a fixed PMI corresponding to the precoding matrix assigned to the UE by the base station over the period of time. In other examples, the UE may select the PMI based on the downlink channel estimate.

In some examples, the UE may initiate monitoring of the rank upon determining that a sounding reference signal (SRS) feature is enabled by the base station. In some examples, the UE may observe no change in the rank over the period of time when the SRS feature is enabled, and therefore, select the fixed RI that corresponds to the rank assigned by the base station for inclusion in the CSF report. Disclosed aspects include a variety of method, system, device, and apparatus embodiments.

These and other aspects will become more fully understood upon a review of the detailed description, which follows. 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 of 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. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments such exemplary embodiments can be implemented in various devices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a wireless communication system according to some aspects.

FIG. 2 is a conceptual illustration of an example of a radio access network according to some aspects.

FIG. 3 is a diagram illustrating an example of a frame structure for use in a radio access network according to some aspects.

FIG. 4 is a block diagram illustrating a wireless communication system supporting beamforming and/or multiple-input multiple-output (MIMO) communication according to some aspects.

FIG. 5 is a signaling diagram illustrating exemplary signaling between a scheduling entity and a scheduled entity to provide a channel state feedback (CSF) report according to some aspects.

FIG. 6 is a signaling diagram illustrating exemplary signaling between a scheduling and a scheduled entity for optimization of the CSF report according to some aspects.

FIG. 7 is a block diagram illustrating exemplary processing circuitry of a scheduled entity according to some aspects.

FIG. 8 is a block diagram illustrating an example of a hardware implementation for a scheduled entity employing a processing system according to some aspects.

FIG. 9 is a flow chart of an exemplary method for a scheduled entity to optimize the CSF report according to some aspects.

FIG. 10 is a flow chart of another exemplary method for a scheduled entity to optimize the CSF report according to some aspects.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

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.

The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. Referring now to FIG. 1, as an illustrative example without limitation, various aspects of the present disclosure are illustrated with reference to a wireless communication system 100. The wireless communication system 100 includes three interacting domains: a core network 102, a radio access network (RAN) 104, and a user equipment (UE) 106. By virtue of the wireless communication system 100, the UE 106 may be enabled to carry out data communication with an external data network 110, such as (but not limited to) the Internet.

The RAN 104 may implement any suitable wireless communication technology or technologies to provide radio access to the UE 106. As one example, the RAN 104 may operate according to 3rd Generation Partnership Project (3GPP) New Radio (NR) specifications, often referred to as 5G. As another example, the RAN 104 may operate under a hybrid of 5G NR and Evolved Universal Terrestrial Radio Access Network (eUTRAN) standards, often referred to as LTE. The 3GPP refers to this hybrid RAN as a next-generation RAN, or NG-RAN. Of course, many other examples may be utilized within the scope of the present disclosure.

As illustrated, the RAN 104 includes a plurality of base stations 108. Broadly, a base station is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. In different technologies, standards, or contexts, a base station may variously be referred to by those skilled in the art as a base transceiver station (BTS) , a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , an access point (AP) , a Node B (NB) , an eNode B (eNB) , a gNode B (gNB) , or some other suitable terminology.

The radio access network 104 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 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, i.e., 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.

Wireless communication between a RAN 104 and a UE 106 may be described as utilizing an air interface. Transmissions over the air interface from a base station (e.g., base station 108) to one or more UEs (e.g., UE 106) may be referred to as downlink (DL) transmission. In accordance with certain aspects of the present disclosure, the term downlink may refer to a point-to-multipoint transmission originating at a scheduling entity (described further below; e.g., base station 108) . Another way to describe this scheme may be to use the term broadcast channel multiplexing. Transmissions from a UE (e.g., UE 106) to a base station (e.g., base station 108) may be referred to as uplink (UL) transmissions. In accordance with further aspects of the present disclosure, the term uplink may refer to a point-to-point transmission originating at a scheduled entity (described further below; e.g., UE 106) .

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station 108) allocates resources for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more scheduled entities. That is, for scheduled communication, UEs 106, which may be scheduled entities, may utilize resources allocated by the scheduling entity 108.

Base stations 108 are not the only entities that may function as scheduling entities. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs) . And as discussed more below, UEs may communicate directly with other UEs in peer-to-peer fashion and/or in relay configuration.

As illustrated in FIG. 1, a scheduling entity 108 may broadcast downlink traffic 112 to one or more scheduled entities 106. Broadly, the scheduling entity 108 is a node or device responsible for scheduling traffic in a wireless communication network, including the downlink traffic 112 and, in some examples, uplink traffic 116 from one or more scheduled entities 106 to the scheduling entity 108. On the other hand, the scheduled entity 106 is a node or device that receives downlink control information 114, including but not limited to scheduling information (e.g., a grant) , synchronization or timing information, or other control information from another entity in the wireless communication network such as the scheduling entity 108.

In addition, the uplink and/or downlink control information and/or traffic information may be time-divided into frames, subframes, slots, and/or symbols. As used herein, a symbol may refer to a unit of time that, in an orthogonal frequency division multiplexed (OFDM) waveform, carries one resource element (RE) per sub-carrier. A slot may carry 7 or 14 OFDM symbols. A subframe may refer to a duration of 1ms. Multiple subframes or slots may be grouped together to form a single frame or radio frame. Of course, these definitions are not required, and any suitable scheme for organizing waveforms may be utilized, and various time divisions of the waveform may have any suitable duration.

In general, base stations 108 may include a backhaul interface for communication with a backhaul portion 120 of the wireless communication system. The backhaul 120 may provide a link between a base station 108 and the core network 102. Further, in some examples, a backhaul network may provide interconnection between the respective base stations 108. Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, or the like using any suitable transport network.

The core network 102 may be a part of the wireless communication system 100, and may be independent of the radio access technology used in the RAN 104. In some examples, the core network 102 may be configured according to 5G standards (e.g., 5GC) . In other examples, the core network 102 may be configured according to a 4G evolved packet core (EPC) , or any other suitable standard or configuration.

Referring now to FIG. 2, by way of example and without limitation, a schematic illustration of a RAN 200 is provided. In some examples, the RAN 200 may be the same as the RAN 104 described above and illustrated in FIG. 1. The geographic area covered by the RAN 200 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. 2 illustrates

macrocells

202, 204, and 206, and a small cell 208, 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.

Various base station arrangements can be utilized. For example, in FIG. 2, two

base stations

210 and 212 are shown in

cells

202 and 204; and a third base station 214 is shown controlling a remote radio head (RRH) 216 in cell 206. That is, a base station can have an integrated antenna or can be connected to an antenna or RRH by feeder cables. In the illustrated example, the

cells

202, 204, and 126 may be referred to as macrocells, as the

base stations

210, 212, and 214 support cells having a large size. Further, a base station 218 is shown in the small cell 208 (e.g., a microcell, picocell, femtocell, home base station, home Node B, home eNode B, etc. ) which may overlap with one or more macrocells. In this example, the cell 208 may be referred to as a small cell, as the base station 218 supports a cell having a relatively small size. Cell sizing can be done according to system design as well as component constraints.

It is to be understood that the radio access network 200 may include any number of wireless base stations and cells. Further, a relay node may be deployed to extend the size or coverage area of a given cell. The

base stations

210, 212, 214, 218 provide wireless access points to a core network for any number of mobile apparatuses. In some examples, the

base stations

210, 212, 214, and/or 218 may be the same as the base station/scheduling entity 108 described above and illustrated in FIG. 1.

Within the RAN 200, the cells may include UEs that may be in communication with one or more sectors of each cell. Further, each

base station

210, 212, 214, and 218 may be configured to provide an access point to a core network 102 (see FIG. 1) for all the UEs in the respective cells. For example,

UEs

222 and 224 may be in communication with base station 210;

UEs

226 and 228 may be in communication with base station 212;

UEs

230 and 232 may be in communication with base station 214 by way of RRH 216; and UE 234 may be in communication with base station 218. In some examples, the

UEs

222, 224, 226, 228, 230, 232, 234, 238, 240, and/or 242 may be the same as the UE/scheduled entity 106 described above and illustrated in FIG. 1.

In some examples, an unmanned aerial vehicle (UAV) 220, which may be a drone or quadcopter, can be a mobile network node and may be configured to function as a UE. For example, the UAV 220 may operate within cell 202 by communicating with base station 210.

In a further aspect of the RAN 200, 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 226 and 228) may communicate with each other using peer to peer (P2P) or sidelink signals 227 without relaying that communication through a base station (e.g., base station 212) . In a further example, UE 238 is illustrated communicating with

UEs

240 and 242. Here, the UE 238 may function as a scheduling entity or a primary sidelink device, and

UEs

240 and 242 may each 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 or scheduled entity in a device-to-device (D2D) , peer-to-peer (P2P) , vehicle-to-vehicle (V2V) network, vehicle-to-everything (V2X) and/or in a mesh network. In a mesh network example,

UEs

240 and 242 may optionally communicate directly with one another in addition to communicating with the scheduling entity 238. 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 some examples, the sidelink signals 227 include sidelink traffic and sidelink control.

The air interface in the radio access network 200 may utilize one or more multiplexing and multiple access algorithms to enable simultaneous communication of the various devices. For example, 5G NR specifications provide multiple access for UL transmissions from

UEs

222 and 224 to base station 210, and for multiplexing for DL transmissions from base station 210 to one or

more UEs

222 and 224, utilizing orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) . In addition, for UL transmissions, 5G 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 210 to UEs 222 and 224 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.

The air interface in the radio access network 200 may further utilize one or more duplexing algorithms. Duplex refers to a point-to-point communication link where both endpoints can communicate with one another in both directions. Full duplex means both endpoints can simultaneously communicate with one another. Half duplex means only one endpoint can send information to the other at a time. In a wireless link, a full duplex channel generally relies on physical isolation of a transmitter and receiver, and suitable interference cancellation technologies. Full duplex emulation is frequently implemented for wireless links by utilizing frequency division duplex (FDD) or time division duplex (TDD) . In FDD, transmissions in different directions operate at different carrier frequencies. In TDD, transmissions in different directions on a given channel are separated from one another using time division multiplexing. That is, at some times the channel is dedicated for transmissions in one direction, while at other times the channel is dedicated for transmissions in the other direction, where the direction may change very rapidly, e.g., several times per slot.

Various aspects of the present disclosure will be described with reference to an OFDM waveform, schematically illustrated in FIG. 3. It should be understood by those of ordinary skill in the art that the various aspects of the present disclosure may be applied to an SC-FDMA waveform in substantially the same way as described herein below. That is, while some examples of the present disclosure may focus on an OFDM link for clarity, it should be understood that the same principles may be applied as well to SC-FDMA waveforms.

Referring now to FIG. 3, an expanded view of an exemplary DL subframe 302 is illustrated, showing an OFDM resource grid. 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.

The resource grid 304 may be used to schematically represent time–frequency resources for a given antenna port. That is, in a multiple-input-multiple-output (MIMO) implementation with multiple antenna ports available, a corresponding multiple number of resource grids 304 may be available for communication. The resource grid 304 is divided into multiple resource elements (REs) 306. An RE, which is 1 subcarrier × 1 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 a resource block (RB) 308, which contains any suitable number of consecutive subcarriers in the frequency domain. In one example, an RB may include 12 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 308 entirely corresponds to a single direction of communication (either transmission or reception for a given device) .

Scheduling of UEs (e.g., scheduled entities) for downlink or uplink transmissions typically involves scheduling one or more resource elements 306 within one or more sub-bands. Thus, a UE generally utilizes only a subset of the resource grid 304. In some examples, 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.

In this illustration, the RB 308 is shown as occupying less than the entire bandwidth of the subframe 302, with some subcarriers illustrated above and below the RB 308. In a given implementation, the subframe 302 may have a bandwidth corresponding to any number of one or more RBs 308. Further, in this illustration, the RB 308 is shown as occupying less than the entire duration of the subframe 302, although this is merely one possible example.

Each 1 ms subframe 302 may consist of one or multiple adjacent slots. In the example shown in FIG. 3, one subframe 302 includes four slots 310, 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 7 or 14 OFDM symbols with a nominal CP. Additional examples may include mini-slots, sometimes referred to as shortened transmission time intervals (TTIs) , having a shorter duration (e.g., one to three OFDM symbols) . These mini-slots or shortened transmission time intervals (TTIs) may in some cases be transmitted occupying resources scheduled for ongoing slot transmissions for the same or for different UEs. Any number of resource blocks may be utilized within a subframe or slot.

An expanded view of one of the slots 310 illustrates the slot 310 including a control region 312 and a data region 314. In general, the control region 312 may carry control channels, and the data region 314 may carry data channels. Of course, a slot may contain all DL, all UL, or at least one DL portion and at least one UL portion. The structure illustrated in FIG. 3 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. 3, the various REs 306 within a RB 308 may be scheduled to carry one or more physical channels, including control channels, shared channels, data channels, etc. Other REs 306 within the RB 308 may also carry pilots or reference signals, including but not limited to a demodulation reference signal (DMRS) , a channel state information –reference signal (CSI-RS) , or a sounding reference signal (SRS) . 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 308.

In a DL transmission, the transmitting device (e.g., the scheduling entity 108) may allocate one or more REs 306 (e.g., within a control region 312) to carry DL control information including one or more DL control channels, such as a PBCH; a PSS; a SSS; a physical control format indicator channel (PCFICH) ; a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH) ; and/or a physical downlink control channel (PDCCH) , etc., to one or more scheduled entities. The PCFICH provides information to assist a receiving device in receiving and decoding the PDCCH. The PDCCH carries downlink control information (DCI) including but not limited to power control commands, scheduling information, a grant, and/or an assignment of REs for DL and UL transmissions. The PHICH carries HARQ feedback transmissions such as an acknowledgment (ACK) or negative acknowledgment (NACK) . 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, the scheduling entity may further utilize one or more REs 306 to carry various pilots and reference signals, such as a CSI-RS and/or DMRS.

In an UL transmission, the transmitting device (e.g., the scheduled entity 106) may utilize one or more REs 306 to carry UL control information including one or more UL control channels, such as a physical uplink control channel (PUCCH) , to the scheduling entity. UL control information may include a variety of packet types and categories, including pilots, reference signals (e.g., a SRS) , and information configured to enable or assist in decoding uplink data transmissions (e.g., a DMRS) . In some examples, the control information may include a scheduling request (SR) , i.e., request for the scheduling entity to schedule uplink transmissions. Here, in response to the SR transmitted on the control channel, the scheduling entity may transmit downlink control information that may schedule resources for uplink packet transmissions. UL control information may also include HARQ feedback, channel state feedback (CSF) , or any other suitable UL control information.

In addition to control information, one or more REs 306 (e.g., within the data region 314) may be allocated for user data traffic. 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 some examples, one or more REs 306 within the data region 314 may be configured to carry system information blocks (SIBs) , carrying information that may enable access to a given cell.

These physical channels described above are generally multiplexed and mapped to transport channels for handling at the medium access control (MAC) layer. Transport channels carry blocks of information called transport blocks (TB) . The transport block size (TBS) , which may correspond to a number of bits of information, may be a controlled parameter, based on the modulation and coding scheme (MCS) and the number of RBs in a given transmission.

The channels or carriers described above in connection with FIGs. 1–3 are not necessarily all of the channels or carriers that may be utilized between a scheduling entity and scheduled entities, 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.

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. 4 illustrates an example of a wireless communication system 400 supporting beamforming and/or MIMO. In a MIMO and/or beamforming system, a transmitter 402 includes multiple transmit antennas 404 (e.g., N transmit antennas) and a receiver 406 includes multiple receive antennas 408 (e.g., M receive antennas) . Thus, there are N × M signal paths 410 from the transmit antennas 404 to the receive antennas 408. Each of the transmitter 402 and the receiver 406 may be implemented, for example, within a scheduling entity, a scheduled entity, 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. Beamforming is a signal processing technique that may be used at the transmitter 402 or receiver 406 to shape or steer an antenna beam (e.g., a transmit beam or receive beam) along a spatial path between the transmitter 402 and the receiver 406. Beamforming may be achieved by combining the signals communicated via antennas 404 or 408 (e.g., antenna elements of an antenna array module) such that some of the signals experience constructive interference while others experience destructive interference. To create the desired constructive/destructive interference, the transmitter 402 or receiver 406 may apply amplitude and/or phase offsets to signals transmitted or received from each of the

antennas

404 or 408 associated with the transmitter 402 or receiver 406.

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 400 is limited by the number of transmit or receive

antennas

404 or 408, 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. In some examples, the RI may include an index ranging from 1 to 4, where a RI of one corresponds to a rank of one (or a single data stream) and a RI of four corresponds to a rank of four (or four data streams) . 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 one example, as shown in FIG. 4, a rank-2 spatial multiplexing transmission on a 2x2 MIMO antenna configuration will transmit one data stream from each transmit antenna 404. Each data stream reaches each receive antenna 408 along a different signal path 410. The receiver 406 may then reconstruct the data streams using the received signals from each receive antenna 408.

Based on the maximum rank supported by the scheduled entity, the scheduling entity may transmit the CSI-RS with separate C-RS sequences for each layer to provide for multi-layer channel estimation. From the CSI-RS, the scheduled entity may estimate the downlink wireless channel by measuring the channel quality (e.g., Signal to Interference Plus Noise Ratio (SINR) ) across layers and resource blocks and feed back the CQI and RI values, along with a precoding matrix indicator (PMI) , within a channel state feedback (CSF) report to the scheduling entity for use in updating the rank and assigning resource elements for future downlink transmissions.

In Time Division Duplex (TDD) systems, the uplink and downlink are reciprocal in that each uses different time slots of the same frequency bandwidth. As such, in TDD systems, the scheduling entity may enable a sounding reference signal (SRS) switch feature that enables the scheduling entity to estimate the downlink wireless channel based on both the CSF report and an SRS transmitted from the scheduled entity to the scheduling entity.

FIG. 5 is a signaling diagram illustrating exemplary signaling between a scheduling entity 502 and a scheduled entity 504 within a wireless network 500. In the illustrated scenario, the scheduled entity 504 can provide a CSF report to the scheduling entity 502. The wireless network 500 may correspond, for example, to the

RAN

104 or 200 shown in FIGs. 1 or 2. The scheduling entity 502 may correspond, for example, to a base station (e.g., gNB or eNB) or other scheduling entity as shown in FIGs. 1 and/2. The scheduled entity 504 may correspond, for example, to a UE or other scheduled node as shown in FIGs. 1 and/or 2.

At 506, the scheduling entity 502 may transmit a reference signal, such as a CSI-RS, to the scheduled entity 504. In some examples, the reference signal may include a plurality of reference signals. Reference signals may be transmitted via respective channel measurement resources. Channel measurement resources may include time–frequency resources, along with a beam direction, within which a particular reference signal can be transmitted. In addition, each reference signal may include a number of pilots allocated within the respective channel measurement resource.

At 508, the scheduled entity 504 can estimate the downlink wireless channel from the reference signal (s) . For example, the scheduled entity 504 may measure the SINR of one or more of the reference signals to obtain a downlink channel estimate of the downlink wireless channel.

At 510, for example, the scheduled entity 504 may determine a RI, PMI, and CQI from the downlink channel estimate. The CQI may include an index (e.g., a CQI index) ranging, for example, from 0 to 15. The CQI index may indicate, for example, the highest MCS at which the Block Error Rate (BLER) of the channel does not exceed 10%. Once selected, the RI, PMI, and CQI index can be fed back. For example, at 512, the scheduled entity 504 may transmit the CSF, including the selected CQI, along with the RI and PMI, to the scheduling entity 502.

Frequent changes in the CQI, RI, and/or PMI due to interference or channel fading may result in frequent changes in the base station downlink scheduling (e.g., MCS, number of layers, etc. ) . In some examples, the base station may be unable to timely modify the downlink scheduling in response to frequent CQI/RI/PMI changes. As a result, the UE downlink performance may be adversely impacted.

In accordance with aspects of the disclosure, the scheduled entity 504 may be configured for optimization of the CSF report when the rank assigned to the scheduled entity over a period of time remains unchanged irrespective of any time-varying RI transmitted to the scheduling entity 502. The period of time may include, for example, a number of slots (e.g., two or more slots) .

In some examples, the scheduling entity 502 may enable a SRS switch feature that allows the scheduling entity 502 to utilize an SRS transmitted by the scheduled entity 504 to the scheduling entity 502 in addition to the CSF report for downlink channel estimation and downlink scheduling (e.g., selection of the MCS, rank, and precoding matrix) . In some examples, when the SRS switch feature is enabled, the scheduling entity 502 may ignore the RI included in the CSF report and select a stable rank for the UE. For example, the scheduling entity 502 may maintain the same rank for the UE over a period of time. In this example, the scheduled entity 504 may observe no change in the rank over the period of time, and therefore, select a fixed RI that corresponds to the stable rank assigned by the base station for inclusion in the CSF report. By selecting a fixed RI, the downlink scheduling in the scheduling entity 502 is simplified, thus improving UE downlink performance. In addition, the CSF processing in the scheduled entity 504 is reduced.

FIG. 6 is a signaling diagram illustrating exemplary signaling between a scheduling entity 602 and a scheduled entity 604 within a wireless network 600. In the illustrated scenario, the scheduled entity 604 can optimize the CSF report provided to the scheduling entity 602. The wireless network 600 may correspond, for example, to the

RAN

104 or 200 shown in FIGs. 1 or 2. The scheduling entity 602 may correspond, for example, to a base station (e.g., gNB or eNB) or other scheduling entity as shown in FIGs. 1 and/2. The scheduled entity 604 may correspond, for example, to a UE or other scheduled node as shown in FIGs. 1 and/or 2.

At 606, the scheduling entity 602 may transmit an SRS switch feature enabled indicator to the scheduled entity 604. In some examples, the scheduling entity 602 may transmit a radio resource control (RRC) configuration message to the scheduled entity 604 including the SRS switch feature enabled indicator. Upon determining that the SRS switch feature is enabled, at 608, the scheduled entity 604 may initiate monitoring of the rank assigned to the scheduled entity 604 by the scheduling entity 602 over a period of time (e.g., within a rank monitoring time period 610) . In some examples, the rank monitoring time period 610 may correspond to a certain number (n) of slots (e.g., two or more slots) .

During the rank monitoring time period 610, the scheduled entity 604 may transmit one or more CSF reports to the scheduling entity 602 and receive one or more downlink assignments from the scheduling entity 606. Each of the CSF reports may include a RI, a PMI, and a CQI, each selected based on a downlink channel estimate obtained by the scheduled entity 604. For example, the scheduled entity 604 may measure the SINR of one or more downlink reference signals (e.g., CSI-RS) to obtain the downlink channel estimate and select the RI, PMI, and CQI based on the downlink channel estimate. Each of the downlink assignments may indicate an MCS, rank, and precoding matrix assigned to the scheduled entity 604 by the scheduling entity 602 based on one or more of the received CSF report and an SRS transmitted from the scheduled entity 604 to the scheduling entity 602.

For example, at 612, the scheduled entity 604 may transmit a CSF report to the scheduling entity 602 with a variable RI=1 and a variable CQI=13. The CSF report may further include a variable PMI (not illustrated) . Here, the RI, PMI, and CQI are variable in that each is selected based on an initial downlink channel estimate obtained during generation of the CSF report. At 614, the scheduling entity 602 may transmit scheduling information to the scheduled entity 604 including a downlink assignment with the MCS=15 (64 QAM) and the rank=2. The downlink assignment may further include a selected precoding matrix (not illustrated) . As shown, the rank assigned to the scheduled entity 604 with the downlink assignment at 614 (e.g., rank=2) differs from the RI provided by the scheduled entity at 612 (e.g., RI=1) . At 616, the scheduled entity 604 may transmit another CSF report to the scheduling entity 602 based on an additional downlink channel estimate obtained subsequent to the initial downlink channel estimate with the variable RI=3 and the variable CQI=6. Again, the CSF may further include the variable PMI, and each of the RI, PMI, and CQI may be considered variable in that each is selected based on the additional downlink channel estimate. At 618, the scheduling entity 602 may transmit scheduling information to the scheduled entity 604 including a downlink assignment with the MCS=20 (256 QAM) and the rank=2. As shown, the rank assigned to the scheduled entity 604 with the downlink assignment at 618 (e.g., rank=2) differs from the RI provided by the scheduled entity at 616 (e.g., RI=3) .

Therefore, as can be seen in the example shown in FIG. 6, each downlink assignment received by the scheduled entity 604 during the rank monitoring time period 610 includes the same rank, indicating that the scheduling entity 602 is implementing the SRS switch feature to provide a stable (unchanging) rank to the scheduled entity 604. Moreover, each CSF report transmitted to the scheduling entity 602 during the rank monitoring time period 610 includes a variable RI that differs from the subsequently assigned rank, indicating that the scheduling entity 602 is ignoring the variable RI included by the scheduled entity 604 in the CSF reports to set the rank while implementing the SRS switch feature.

Upon determining that the rank assigned to the scheduled entity 604 by the scheduling entity 606 remained unchanged over the rank monitoring time period 610, at 620, the scheduled entity 620 may begin optimization of the CSF report. For example, optimization can be achieved by including a fixed RI in each subsequent CSF report irrespective of the current downlink channel estimation obtained by the scheduled entity 604. In some examples, the fixed RI may correspond to the rank assigned to the scheduled entity 604 during the rank monitoring time period 610. In some examples, the scheduled entity 604 may further include a fixed PMI in each subsequent CSF report. For example, the scheduled entity 604 may further monitor the precoding matrix assigned to the scheduled entity 604 during the rank monitoring time period 610, and if the precoding matrix remains unchanged over the rank monitoring time period 610, select a fixed PMI corresponding to the unchanging precoding matrix.

For example, at 622, the scheduled entity 604 may transmit a CSF report to the scheduling entity 602 with the fixed RI=2, corresponding to the rank of 2 assigned to the scheduled entity 604 during the rank monitoring time period 610, and the CQI=10. The CSF report may further include the PMI (not illustrated) , which may be a variable PMI or a fixed PMI. At 624, the scheduling entity 602 may transmit scheduling information to the scheduled entity 604 including a downlink assignment with the MCS=20 (256 QAM) and the rank=2. As another example, at 626, the scheduled entity 604 may transmit a CSF report to the scheduling entity 602 with the fixed RI=2 and the CQI=6. Again, the CSF report may further include a variable or fixed PMI (not illustrated) . At 628, the scheduling entity 602 may transmit scheduling information to the scheduled entity 604 including a downlink assignment with the MCS=20 (256 QAM) and the rank=2.

Thus, upon commencing of CSF report optimization, the scheduled entity 604 may include a fixed RI having the same value in each subsequent CSF report. As a result, the scheduled entity 604 may reduce the processing involved in generating the CSF report by selecting the same (fixed) RI value regardless of the channel conditions of the downlink wireless channel. In addition, processing may be further reduced by including a fixed PMI in addition to a fixed RI in the CSF report. At the scheduling entity 602, utilizing a fixed rank, and optionally also a fixed precoding matrix, simplifies the downlink scheduling and may result in stabilization of the MCS based on channel conditions, as illustrated in the example of FIG. 6.

FIG. 7 is a block diagram illustrating exemplary processing circuitry 700 of a scheduled entity according to some aspects. The scheduled entity may correspond to a UE or other scheduled entity, as shown in FIGs. 1, 2, 5, and/or 6. The processing circuitry 700 includes channel estimation circuitry 702, RI selection circuitry 708, PMI selection circuitry 712, CQI identification circuitry 716, and CSF optimization circuitry 720.

The channel estimation circuitry 702 is configured to estimate conditions of a downlink wireless channel. It can do so based on receiving one or more reference signals 704 transmitted from a scheduling entity (e.g., a base station, such as a gNB or eNB, or other scheduling entity) . For example, the channel estimation circuitry 702 may be configured to utilize the one or more reference signals to estimate a downlink channel between the scheduled entity and the scheduling entity and produce a downlink channel estimate 706. For example, the downlink channel estimate 706 may be ascertained based on the measured SINR of one or more of the reference signals.

The RI selection circuitry 708 is configured to receive the downlink channel estimate 706 and select a RI 710 based on the antenna configuration of the scheduled entity and scheduling entity and the downlink channel estimate 706. The RI may indicate, for example, the number of layers that may be supported under the current channel conditions. The RI selection circuitry 708 may further output the selected RI 710 for inclusion in a CSF report to be transmitted to the scheduling entity.

The PMI selection circuitry 712 is configured to receive the RI 710 from the RI selection circuitry 708 and the downlink channel estimate 706 from the channel estimation circuitry 702 and select a PMI 714 based on the RI and the downlink channel estimate 706. The PMI selection circuitry 712 may further output the selected PMI 714 for inclusion in the CSF report.

The CQI identification circuitry 716 is configured to receive the RI 710 from the RI selection circuitry 708, the PMI 714 from the PMI selection circuitry 712, and the downlink channel estimate 706 from the channel estimation circuitry 702 and identify a CQI 718 based on the RI 710, PMI 714, and downlink channel estimate 706. The CQI identification circuitry 716 may further output the CQI 718 for inclusion within the CSF report fed back to the scheduling entity.

The CSF optimization circuitry 720 is configured to implement CSF report optimization. In some examples, the CSF optimization circuitry 720 may be configured to monitor a rank assigned to the scheduled entity by the scheduling entity over a period of time (e.g., two or more slots) and implement CSF report optimization when the rank remains unchanged over the period of time. For example, the CSF optimization circuitry 720 may be configured to initiate monitoring of the rank upon determining that an SRS switch feature has been enabled on the scheduling entity.

When the CSF optimization circuitry 720 commences CSF report optimization, the CSF optimization circuitry 720 may be configured to select a fixed RI 722 and input the fixed RI 722 to the RI selection circuitry 708. In some examples, the fixed RI 722 corresponds to the rank assigned to the scheduled entity over the period of time. In this example, the RI selection circuitry 708 may forgo utilizing the downlink channel estimate 706 in selecting the RI 710 and instead output the fixed RI 722 as the RI 710 to be included in the CSF report. The CSF optimization circuitry 720 may further be configured to select a fixed PMI 724 and input the fixed PMI 724 to the PMI selection circuitry 712. In some examples, the fixed PMI 724 corresponds to the PMI assigned to the scheduled entity over the period of time. In this example, the PMI selection circuitry 712 may forgo utilizing the RI 710 and/or downlink channel estimate 706 in selecting the PMI 714 and instead output the fixed PMI 724 as the PMI 714 to be included in the CSF report.

FIG. 8 is a conceptual diagram illustrating an example of a hardware implementation for an exemplary scheduled entity 800 employing a processing system 814. For example, the scheduled entity 800 may be a UE as illustrated in any one or more of FIGs. 1, 2, and/or 5–7.

The scheduled entity 800 may be implemented with a processing system 814 that includes one or more processors 804. Examples of processors 804 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 scheduled entity 800 may be configured to perform any one or more of the functions described herein. That is, the processor 804, as utilized in a scheduled entity 800, may be used to implement any one or more of the processes described below. The processor 804 may in some instances be implemented via a baseband or modem chip and in other implementations, the processor 804 may itself comprise a number of devices distinct and different from a baseband or modem chip (e.g., in such scenarios is may work in concert to achieve embodiments discussed herein) . And as mentioned above, various hardware arrangements and components outside of a baseband modem processor can be used in implementations, including RF-chains, power amplifiers, modulators, buffers, interleavers, adders/summers, etc.

In this example, the processing system 814 may be implemented with a bus architecture, represented generally by the bus 802. The bus 802 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 814 and the overall design constraints. The bus 802 communicatively couples together various circuits including one or more processors (represented generally by the processor 804) , a memory 805, and computer-readable media (represented generally by the computer-readable medium 806) . The bus 802 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 808 provides an interface between the bus 802 and a transceiver 810. The transceiver 810 provides a means for communicating with various other apparatus over a transmission medium (e.g., air interface) . A user interface 812 (e.g., keypad, display, speaker, microphone, joystick) may also be provided.

The processor 804 is responsible for managing the bus 802 and general processing, including the execution of software stored on the computer-readable medium 806. The software, when executed by the processor 804, causes the processing system 814 to perform the various functions described below for any particular apparatus. The computer-readable medium 806 and the memory 805 may also be used for storing data that is manipulated by the processor 804 when executing software.

One or more processors 804 in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium 806.

The computer-readable medium 806 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 may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. The computer-readable medium 806 may reside in the processing system 814, external to the processing system 814, or distributed across multiple entities including the processing system 814. The computer-readable medium 806 may be embodied in a computer program product. In some examples, the computer-readable medium 806 may be part of the memory 805. 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 some aspects of the disclosure, the processor 804 may include circuitry configured for various functions. For example, the processor 804 may include communication and processing circuitry 842, configured to communicate with a scheduling entity (e.g., a base station) . In some examples, the communication and processing circuitry 842 may include one or more hardware components that provide the physical structure that performs processes related to wireless communication (e.g., signal reception and/or signal transmission) and signal processing (e.g., processing a received signal and/or processing a signal for transmission) .

In some examples, the communication and processing circuitry 842 may be configured to receive one or more reference signals (e.g., CSI-RS) from the scheduling entity and to transmit a CSF report to the scheduling entity in response to the reference signal (s) . The CSF report may include, for example, the CQI, PMI, and RI. The communication and processing circuitry 842 may further be configured to receive scheduling information including a downlink assignment indicating a MCS, rank, and precoding matrix assigned to the scheduled entity for a downlink transmission (e.g., PDSCH) from the scheduling entity to the scheduled entity 800. The communication and processing circuitry 842 may further be configured to execute communication and processing software 852 stored in the computer-readable medium 806 to implement one or more of the functions described herein.

The processor 804 may further include channel estimation circuitry 844, configured to estimate a downlink wireless channel between the scheduled entity 800 and the scheduling entity to produce a downlink channel estimate. The channel estimation circuitry 844 may correspond, for example, to the channel estimation circuitry 702 shown in FIG. 7. In some examples, the channel estimation circuitry 844 may be configured to measure the SINR of the one or more reference signals to produce the downlink channel estimate 706. The channel estimation circuitry 844 may further be configured to execute channel measurement software 854 stored in the computer-readable medium 806 to implement one or more of the functions described herein.

The processor 804 may further include CSF optimization circuitry 846, configured to implement optimization of the CSF report. The CSF optimization circuitry 846 may, for example, correspond to the CSF optimization circuitry 720 shown in FIG. 7.In some examples, the CSF optimization circuitry 846 may be configured to monitor the rank assigned to the scheduled entity 800 by the scheduling entity over a period of time. For example, the CSF optimization circuitry 846 may be configured to monitor the rank assigned to the scheduled entity 800 in one or more downlink assignments received by the communication and processing circuitry 842 via the transceiver 810. In some examples, the CSF optimization circuitry 846 may initiate monitoring of the rank in response to receiving a SRS switch enabled indicator (e.g., via an RRC message) from the scheduling entity.

When the rank remains unchanged over the period of time, the CSF optimization circuitry 846 may begin implementing CSF report optimization to select at least a fixed RI 815 for inclusion in one or more subsequent CSF reports. In some examples, the CSF optimization circuitry 846 may further select a fixed PMI 818 for inclusion in the next CSF report. The selected fixed RI 815 may correspond to the rank assigned to the scheduled entity 800 over the period of time during which the CSF optimization circuitry 846 monitored the rank. Similarly, the selected fixed PMI 818 may correspond to the PMI assigned to the scheduled entity 800 over the period of time. The fixed RI 815 and fixed PMI 818 may be stored, for example, in memory 805 for inclusion in the subsequent CSF reports. The CSF optimization circuitry 846 may further be configured to execute CSF optimization software 856 stored in the computer-readable medium to implement one or more of the functions described herein.

The processor 804 may further include CSF generation circuitry 848, configured to generate a CSF report including the CQI, PMI, and RI for transmission to the scheduling entity. The CSF generation circuitry 848 may correspond, for example, to the RI selection circuitry 708, PMI selection circuitry 712, and CQI identification circuitry 716 shown in FIG. 7. In some examples, the CSF generation circuitry 848 may be configured to include the fixed RI selected by the CSF optimization circuitry 846 in the CSF report. In some examples, the CSF generation circuitry 848 may further be configured to select a PMI based on the selected (fixed) RI and the downlink channel estimate obtained by the channel estimation circuitry 844 for inclusion in the CSF report. In other examples, the CSF generation circuitry may further be configured to include the fixed PMI selected by the CSF optimization circuitry 846 in the CSF report. The CSF generation circuitry 88 may further be configured to identify a CQI for inclusion in the CSF report based on the fixed RI, selected PMI (or fixed PMI) , and the downlink channel estimate obtained by the channel estimation circuitry 844. The CSF generation circuitry 848 may further be configured to execute CSF generation software 858 stored in the computer-readable medium to implement one or more of the functions described herein.

FIG. 9 is a flow chart 900 of a method for a scheduled entity (e.g., a UE) to optimize the CSF report. 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 may be performed by the scheduled entity 800, as described above and illustrated in FIG. 8, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block 902, the scheduled entity may monitor a rank assigned to the scheduled entity by a scheduling entity (e.g., a base station) in wireless communication with the scheduled entity over a period of time (e.g., two or more slots) . In some examples, the scheduled entity may initiate monitoring of the rank upon determining that an SRS switch feature is enabled by the scheduling entity. For example, the CSF optimization circuitry 846, together with the communication and processing circuitry 842 and transceiver 810, shown and described above in connection with FIG. 8, may receive downlink assignments from the scheduling entity over the period of time and monitor the rank indicated in each of the downlink assignments.

At 904, the scheduled entity may estimate a downlink wireless channel between the scheduled entity and the scheduling entity to obtain a downlink channel estimate. In some examples, the scheduled entity may estimate the downlink wireless channel based on one or more reference signals (e.g., CSI-RS) . For example, the channel estimation circuitry 844, communication and processing circuitry 842, and transceiver 810 shown and described above in connection with FIG. 8 may receive the one or more reference signals and estimate the wireless channel based on the one or more reference signals.

At block 906, the scheduled entity may select a fixed rank indicator (RI) irrespective of the downlink channel estimate when the rank remains unchanged over the period of time. In some examples, the fixed RI may correspond to the rank assigned to the scheduled entity by the scheduling entity over the period of time. For example, the fixed RI may correspond to the rank selected by the scheduling entity during implementation of the SRS switch feature in which the scheduling entity utilizes both the CSF report and an SRS transmitted by the scheduled entity in estimating the downlink wireless channel and selecting the MCS, rank, and precoding matrix. For example, the CSF optimization circuitry 846, shown and described above in connection with FIG. 8, may select the fixed RI.

At block 908, the scheduled entity may identify a channel quality indicator (CQI) based on the downlink channel estimate and the fixed RI. For example, the CSF generation circuitry 848, shown and described above in connection with FIG. 8, may identify the CQI.

At block 910, the scheduled entity may transmit the fixed RI and the CQI to the scheduling entity. In some examples, the fixed RI and the CQI may be transmitted within a CSF report to the scheduling entity. The CSF report may further include a fixed or variable PMI. For example, the communication and processing circuitry 842, together with the transceiver 810, shown and described above in connection with FIG. 8 may transmit the CSF report to the scheduling entity.

FIG. 10 is a flow chart 1000 of another exemplary method for a scheduled entity (e.g., a UE) to optimize the CSF report. 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 may be performed by the scheduled entity 800, as described above and illustrated in FIG. 8, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block 1002, the scheduled entity may determine whether an SRS switch feature is enabled on a scheduling entity (e.g., a base station) in wireless communication with the scheduled entity. In some example, the scheduled entity may receive an RRC configuration message indicating that the SRS switch feature is enabled. For example, the communication and processing circuitry 842, together with the transceiver 810, shown and described above in connection with FIG. 8 may determine whether the SRS switch feature is enabled.

If the SRS switch feature is enabled (Y branch of block 1002) , at block 1004, the scheduled entity may monitor a rank assigned to the scheduled entity by the scheduling entity over a period of time (e.g., two or more slots) . For example, the CSF optimization circuitry 846, together with the communication and processing circuitry 842 and transceiver 810, shown and described above in connection with FIG. 8, may receive downlink assignments from the scheduling entity over the period of time and monitor the rank indicated in each of the downlink assignments.

At block 1006, the scheduled entity may determine whether the rank remains unchanged over the period of time. In some examples, if the rank remains unchanged regardless of any time-varying rank indicators (RIs) provided by the scheduled entity to the scheduling entity, the scheduled entity may determine that the scheduling entity is ignoring the RI provided by the scheduled entity to provide a stable rank to the scheduled entity while implementing the SRS switch feature. For example, the CSF optimization circuitry 846, shown and described above in connection with FIG. 8, may determine whether the rank remains unchanged.

If the rank varies over the period of time (N branch of block 1006) or if the SRS switch feature is not enabled on the scheduling entity (N branch of block 1002) , at block 1008, the scheduled entity may estimate a wireless channel between the scheduled entity and the scheduling entity to obtain a channel estimate. In some examples, the scheduled entity may estimate the wireless channel based on one or more reference signals (e.g., CSI-RS) . For example, the channel estimation circuitry 844, communication and processing circuitry 842, and transceiver 810 shown and described above in connection with FIG. 8 may receive the one or more reference signals and estimate the wireless channel based on the one or more reference signals. In addition, at block 1010, the scheduled entity may further select a variable RI based on the downlink channel estimate. For example, the CSF generation circuitry 848, shown and described above in connection with FIG. 8, may select the variable RI.

However, if the rank remains unchanged over the period of time (Y branch of block 1006) , at block 1012, the scheduled entity may estimate a wireless channel between the scheduled entity and the scheduling entity to obtain a channel estimate. In some examples, the scheduled entity may estimate the wireless channel based on one or more reference signals (e.g., CSI-RS) . For example, the channel estimation circuitry 844, communication and processing circuitry 842, and transceiver 810 shown and described above in connection with FIG. 8 may receive the one or more reference signals and estimate the wireless channel based on the one or more reference signals. In addition, at block 1014, the scheduled entity may select a fixed RI irrespective of the downlink channel estimate. In some examples, the fixed RI may correspond to the rank assigned to the scheduled entity by the scheduling entity over the period of time. For example, the CSF optimization circuitry 846, shown and described above in connection with FIG. 8, may select the fixed RI.

At block 1016, the scheduled entity may select a precoding matrix indicator (PMI) . In some examples, the PMI may be a variable PMI selected based on the RI (e.g., either the fixed RI from block 1014 or the variable RI from block 1010) and the downlink channel estimate. In other examples, the PMI may be a fixed PMI selected irrespective of the downlink channel estimate. For example, the fixed RI may correspond to the precoding matrix assigned to the scheduled entity by the scheduling entity over the period of time. For example, the CSF optimization circuitry 846 and/or the CSF generation circuitry 848, shown and described above in connection with FIG. 8, may select the PMI.

At block 1018, the scheduled entity may identify a channel quality indicator (CQI) based on the downlink channel estimate, the RI (e.g., the fixed or variable RI) , and the PMI (e.g., the fixed or variable PMI) . For example, the CSF generation circuitry 848, shown and described above in connection with FIG. 8, may identify the CQI.

At block 1020, the scheduled entity may transmit a CSF report including the RI (e.g., fixed or variable RI) , PMI (e.g., fixed or variable PMI) , and the CQI to the scheduling entity. For example, the communication and processing circuitry 842, together with the transceiver 810, shown and described above in connection with FIG. 8 may transmit the CSF report to the scheduling entity.

The processes shown in FIGs. 9–10 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In one configuration, a scheduled entity includes means for monitoring a rank assigned to the scheduled entity by a scheduling entity in wireless communication with the scheduled entity over a period of time, means for obtaining a downlink channel estimate of a downlink wireless channel between the scheduled entity and the scheduling entity, means for selecting a fixed rank indicator (RI) irrespective of the downlink channel estimate when the rank remains unchanged over the period of time, means for identifying a channel quality indicator (CQI) based on the downlink channel estimate and the fixed RI, and means for transmitting a channel state feedback (CSF) report including the fixed RI and the CQI to the scheduling entity.

In one aspect, the aforementioned means for monitoring the rank assigned to the scheduled entity, means for obtaining the downlink channel estimate, means for selecting the fixed RI, means for identifying the CQI, and means for transmitting the CSF report including the fixed RI and the CQI may be the processor (s) 804 shown in FIG. 8 configured to perform the functions recited by the aforementioned means.

For example, the aforementioned means for monitoring the rank assigned to the scheduled entity may include the CSF optimization circuitry 846, communication and processing circuitry 842, and transceiver 810 shown in FIG. 8. As another example, the aforementioned means for obtaining the downlink channel estimate may include the channel estimation circuitry 844, communication and processing circuitry 842, and transceiver 810 shown in FIG. 8. As another example, the aforementioned means for selecting the fixed RI may include the CSF optimization circuitry 846 shown in FIG. 8. As another example, the aforementioned means for identifying the CQI may include the CSF generation circuitry 848 shown in FIG. 8. In another example, the aforementioned means for transmitting the CSF report may include the communication and processing circuitry 842 and transceiver 810 shown in FIG. 8. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.

Several aspects of a wireless communication network have been presented with reference to an exemplary implementation. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards.

By way of example, various aspects may be implemented within other systems defined by 3GPP, such as Long-Term Evolution (LTE) , the Evolved Packet System (EPS) , the Universal Mobile Telecommunication System (UMTS) , and/or the Global System for Mobile (GSM) . Various aspects may also be extended to systems defined by the 3rd Generation Partnership Project 2 (3GPP2) , such as CDMA2000 and/or Evolution-Data Optimized (EV-DO) . Other examples may be implemented within systems employing IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Ultra-Wideband (UWB) , Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.

Within the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration. ” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B, and object B touches object C, then objects A and C may still be considered coupled to one another-even if they do not directly physically touch each other. For instance, a first object may be coupled to a second object even though the first object is never directly physically in contact with the second object. The terms “circuit” and “circuitry” are used broadly, and intended to include both hardware implementations of electrical devices and conductors that, when connected and configured, enable the performance of the functions described in the present disclosure, without limitation as to the type of electronic circuits, as well as software implementations of information and instructions that, when executed by a processor, enable the performance of the functions described in the present disclosure.

One or more of the components, steps, features and/or functions illustrated in FIGs. 1–10 may be rearranged and/or combined into a single component, step, feature or function or embodied in several components, steps, or functions. Additional elements, components, steps, and/or functions may also be added without departing from novel features disclosed herein. The apparatus, devices, and/or components illustrated in FIGs. 1, 2, and 4–8 may be configured to perform one or more of the methods, features, or steps described herein. The novel algorithms described herein may also be efficiently implemented in software and/or embedded in hardware.

It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, b, and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

Claims

A method for wireless communication at a scheduled entity in a wireless communication network, the method comprising:

monitoring a rank assigned to the scheduled entity by a scheduling entity in wireless communication with the scheduled entity over a period of time;

obtaining a downlink channel estimate of a downlink wireless channel between the scheduled entity and the scheduling entity;

selecting a fixed rank indicator (RI) irrespective of the downlink channel estimate when the rank remains unchanged over the period of time;

identifying a channel quality indicator (CQI) based on the downlink channel estimate and the fixed RI; and

transmitting a channel state feedback (CSF) report comprising the fixed RI and the CQI to the scheduling entity.
The method of claim 1, wherein the fixed RI corresponds to the rank assigned to the scheduled entity over the period of time.
The method of claim 1, further comprising:

determining that a sounding reference signal switch feature is enabled by the scheduling entity; and

initiating monitoring of the rank assigned to the scheduled entity over the period of time when the sounding reference signal switch feature is enabled.
The method of claim 3, further comprising:

selecting a variable RI over the period of time based on at least one additional downlink channel estimate obtained over the period of time; and

transmitting the variable RI to the scheduling entity over the period of time.
The method of claim 4, wherein the rank assigned to the scheduled entity over the period of time differs from the variable RI.
The method of claim 1, wherein transmitting the CSF report comprising the fixed RI and the CQI further comprises:

transmitting the CSF report comprising the fixed RI, the CQI, and a fixed precoding matrix indicator (PMI) .
The method of claim 6, further comprising:

monitoring a precoding matrix assigned to the scheduled entity by the scheduling entity over the period of time; and

selecting the fixed PMI corresponding to the precoding matrix assigned to the scheduled entity over the period of time when the precoding matrix remains unchanged over the period of time.
The method of claim 1, further comprising:

selecting a variable precoding matrix indicator (PMI) based on the downlink channel estimate; and

transmitting the variable PMI within the CSF report.
A scheduled entity in a wireless communication network, comprising:

a wireless transceiver;

a memory; and

a processor communicatively coupled to the wireless transceiver and the memory, wherein the processor is configured to:

monitor a rank assigned to the scheduled entity by a scheduling entity in wireless communication with the scheduled entity over a period of time;

obtain a downlink channel estimate of a downlink wireless channel between the scheduled entity and the scheduling entity;

select a fixed rank indicator (RI) irrespective of the downlink channel estimate when the rank remains unchanged over the period of time;

identify a channel quality indicator (CQI) based on the downlink channel estimate and the fixed RI; and

transmit a channel state feedback (CSF) report comprising the fixed RI and the CQI to the scheduling entity via the wireless transceiver.
The scheduled entity of claim 9, wherein the fixed RI corresponds to the rank assigned to the scheduled entity over the period of time.
The scheduled entity of claim 9, wherein the processor is further configured to:

determine that a sounding reference signal switch feature is enabled by the scheduling entity; and

initiate monitoring of the rank assigned to the scheduled entity over the period of time when the sounding reference signal switch feature is enabled.
The scheduled entity of claim 11, wherein the processor is further configured to:

select a variable RI over the period of time based on at least one additional downlink channel estimate obtained over the period of time; and

transmit the variable RI to the scheduling entity over the period of time.
The scheduled entity of claim 12, wherein the rank assigned to the scheduled entity over the period of time differs from the variable RI.
The scheduled entity of claim 9, wherein the processor is further configured to:

transmit the CSF report comprising the fixed RI, the CQI, and a fixed precoding matrix indicator (PMI) .
The scheduled entity of claim 14, wherein the processor is further configured to:

monitor a precoding matrix assigned to the scheduled entity by the scheduling entity over the period of time; and

select the fixed PMI corresponding to the precoding matrix assigned to the scheduled entity over the period of time when the precoding matrix remains unchanged over the period of time.
The scheduled entity of claim 9, wherein the processor is further configured to:

select a variable precoding matrix indicator (PMI) based on the downlink channel estimate; and

transmit the variable PMI within the CSF report.
A scheduled entity in a wireless communication network, comprising:

means for monitoring a rank assigned to the scheduled entity by a scheduling entity in wireless communication with the scheduled entity over a period of time;

means for obtaining a downlink channel estimate of a downlink wireless channel between the scheduled entity and the scheduling entity;

means for selecting a fixed rank indicator (RI) irrespective of the downlink channel estimate when the rank remains unchanged over the period of time;

means for identifying a channel quality indicator (CQI) based on the downlink channel estimate and the fixed RI; and

means for transmitting a channel state feedback (CSF) report comprising the fixed RI and the CQI to the scheduling entity.
The scheduled entity of claim 17, wherein the fixed RI corresponds to the rank assigned to the scheduled entity over the period of time.
The scheduled entity of claim 17, further comprising:

means for determining that a sounding reference signal switch feature is enabled by the scheduling entity; and

means for initiating monitoring of the rank assigned to the scheduled entity over the period of time when the sounding reference signal switch feature is enabled.
The scheduled entity of claim 19, further comprising:

means for selecting a variable RI over the period of time based on at least one additional downlink channel estimate obtained over the period of time; and

means for transmitting the variable RI to the scheduling entity over the period of time.
The scheduled entity of claim 20, wherein the rank assigned to the scheduled entity over the period of time differs from the variable RI.
The scheduled entity of claim 17, wherein the means for transmitting the CSF report comprising the fixed RI and the CQI further comprises:

means for transmitting the CSF report comprising the fixed RI, the CQI, and a fixed precoding matrix indicator (PMI) .
The scheduled entity of claim 22, further comprising:

means for monitoring a precoding matrix assigned to the scheduled entity by the scheduling entity over the period of time; and

means for selecting the fixed PMI corresponding to the precoding matrix assigned to the scheduled entity over the period of time when the precoding matrix remains unchanged over the period of time.
The scheduled entity of claim 17, further comprising:

means for selecting a variable precoding matrix indicator (PMI) based on the downlink channel estimate; and

means for transmitting the variable PMI within the CSF report.
A non-transitory computer-readable medium storing computer-executable code, comprising code for causing a scheduled entity to:

monitor a rank assigned to the scheduled entity by a scheduling entity in wireless communication with the scheduled entity over a period of time;

obtain a downlink channel estimate of a downlink wireless channel between the scheduled entity and the scheduling entity;

select a fixed rank indicator (RI) irrespective of the downlink channel estimate when the rank remains unchanged over the period of time;

identify a channel quality indicator (CQI) based on the downlink channel estimate and the fixed RI; and

transmit a channel state feedback (CSF) report comprising the fixed RI and the CQI to the scheduling entity via the wireless transceiver.
The non-transitory computer-readable medium of claim 25, wherein the fixed RI corresponds to the rank assigned to the scheduled entity over the period of time.
The non-transitory computer-readable medium of claim 25, further comprising code for causing the scheduled entity to:

determine that a sounding reference signal switch feature is enabled by the scheduling entity; and

initiate monitoring of the rank assigned to the scheduled entity over the period of time when the sounding reference signal switch feature is enabled.
The non-transitory computer-readable medium of claim 26, further comprising code for causing the scheduled entity to:

transmit the CSF report comprising the fixed RI, the CQI, and a fixed precoding matrix indicator (PMI) .
The non-transitory computer-readable medium of claim 28, further comprising code for causing the scheduled entity to:

monitor a precoding matrix assigned to the scheduled entity by the scheduling entity over the period of time; and

select the fixed PMI corresponding to the precoding matrix assigned to the scheduled entity over the period of time when the precoding matrix remains unchanged over the period of time.
The non-transitory computer-readable medium of claim 25, further comprising code for causing the scheduled entity to:

select a variable precoding matrix indicator (PMI) based on the downlink channel estimate; and

transmit the variable PMI within the CSF report.