CN112673580A - Determination of downlink channel state information in massive MIMO systems - Google Patents

Determination of downlink channel state information in massive MIMO systems Download PDF

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CN112673580A
CN112673580A CN201880097007.6A CN201880097007A CN112673580A CN 112673580 A CN112673580 A CN 112673580A CN 201880097007 A CN201880097007 A CN 201880097007A CN 112673580 A CN112673580 A CN 112673580A
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csi
terminal device
determining
codebook
downlink
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CN112673580B (en
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孙欢
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Nokia Shanghai Bell Co Ltd
Nokia Oyj
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Nokia Shanghai Bell Co Ltd
Nokia Networks Oy
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0026—Transmission of channel quality indication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0621—Feedback content

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

Embodiments of the present disclosure provide methods, apparatuses, and computer-readable media for determining downlink CSI in massive MIMO systems. In an example embodiment, methods implemented at a terminal device and a network device, respectively, are provided. The method implemented at the terminal device comprises: determining first CSI and second CSI based on downlink reference signals received from a network device through a first antenna and a second antenna of a terminal device, respectively; determining an update codebook specific to the terminal device based on the first CSI; quantizing the second CSI based on the update codebook; and transmitting, by the first antenna, the uplink SRS and the quantized CSI to a network device. The method implemented at a network device includes: receiving an uplink SRS and quantized CSI from a terminal device; determining, based on the SRS, first downlink CSI associated with a first antenna of the terminal device; determining an update codebook specific to the terminal device based on the first downlink CSI; and determining second downlink CSI associated with a second antenna of the terminal device based on the updated codebook and the quantized CSI.

Description

Determination of downlink channel state information in massive MIMO systems
Technical Field
Embodiments of the present disclosure relate generally to the field of communications, and more particularly, to a method, apparatus, and computer-readable storage medium for determining downlink Channel State Information (CSI) in a massive multiple-input multiple-output (MIMO) system.
Background
In order to serve more users and provide high capacity for each user, MIMO antenna arrays or "massive MIMO" techniques have been introduced in fourth generation (4G) and fifth generation (5G) mobile communication systems. Massive MIMO schemes require high accuracy of downlink CSI for each user at the network device for multi-user scheduling and transmit precoder design for downlink data transmission.
As is known, Time Division Duplex (TDD) techniques are more suitable for implementation of massive MIMO schemes, since in this case the network device can easily obtain accurate downlink CSI for each user with less overhead. In a TDD massive MIMO system, both the network equipment and the user's terminal equipment are equipped with multiple antennas. The network device obtains the downlink CSI by measuring an uplink Sounding Reference Signal (SRS) of the user and using channel reciprocity characteristics between a downlink channel and an uplink channel.
However, since only a subset of all antennas on the terminal device side can be used for transmission of uplink signals in a certain time slot, the terminal device should switch its antenna group to transmit SRS in a plurality of consecutive predetermined time slots, thereby helping the network device to get the complete downlink CSI. For different SRS configuration periods, the network device may take a longer period of time to get the full CSI for the user, and thus the CSI may be outdated compared to the actual channel used for downlink data transmission. Thus, multi-user scheduling and transmit precoder design may suffer from outdated CSI, such that multi-user interference is not well pre-compressed and system performance may be degraded.
Disclosure of Invention
In general, embodiments of the present disclosure provide methods, devices, and computer-readable storage media for determining downlink CSI.
In a first aspect, a method implemented at a terminal device is provided. The method comprises the following steps: determining first CSI and second CSI based on downlink reference signals received from a network device through a first antenna and a second antenna of a terminal device, respectively; determining an update codebook specific to the terminal device based on the first CSI; quantizing the second CSI based on the update codebook; and transmitting, by the first antenna, the uplink SRS and the quantized CSI to the network device.
In a second aspect, a method implemented at a network device is provided. The method comprises the following steps: receiving an uplink SRS and quantized CSI from a terminal device; determining, based on the SRS, first downlink CSI associated with a first antenna of the terminal device; determining an update codebook specific to the terminal device based on the first downlink CSI; and determining second downlink CSI associated with a second antenna of the terminal device based on the updated codebook and the quantized CSI.
In a third aspect, a terminal device is provided. The terminal device includes a processor and a memory coupled to the processor. The memory stores instructions that, when executed by the processor, cause the terminal device to perform actions. The actions include: determining first and second CSI based on downlink reference signals received from a network device through first and second antennas of a terminal device, respectively; determining an update codebook specific to the terminal device based on the first CSI; quantizing the second CSI based on the update codebook; and transmitting, by the first antenna, the uplink SRS and the quantized CSI to the network device.
In a fourth aspect, a network device is provided. The network device includes a processor and a memory coupled to the processor. The memory stores instructions that, when executed by the processor, cause the terminal device to perform actions. The actions include: receiving an uplink SRS and quantized CSI from a terminal device; determining, based on the SRS, first downlink CSI associated with a first antenna of the terminal device; determining an update codebook specific to the terminal device based on the first downlink CSI; and determining second downlink CSI associated with a second antenna of the terminal device based on the updated codebook and the quantized CSI.
In a fifth aspect, a computer-readable storage medium having instructions stored thereon is provided. The instructions, when executed on at least one processor, cause the at least one processor to perform a method according to the first aspect of the present disclosure.
In a sixth aspect, a computer-readable storage medium having instructions stored thereon is provided. The instructions, when executed on at least one processor, cause the at least one processor to perform a method according to the second aspect of the present disclosure.
It should be understood that this summary is not intended to identify key or essential features of the embodiments of the disclosure, nor is it intended to be used to limit the scope of the disclosure. Other features of the present disclosure will become readily apparent from the following description.
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The above and other objects, features and advantages of the present disclosure will become more apparent from the following more detailed description of some embodiments of the present disclosure, as illustrated in the accompanying drawings, in which:
FIG. 1 illustrates an example communication network in which embodiments of the present disclosure may be implemented;
fig. 2 illustrates an example scenario of antenna switching based uplink SRS transmission in which embodiments of the present disclosure may be implemented;
FIG. 3 illustrates exemplary interactions between a network device and a terminal device, according to some embodiments of the present disclosure;
fig. 4 illustrates a flowchart of an example method implemented at a terminal device for determining downlink CSI in accordance with some embodiments of the present disclosure;
FIG. 5 illustrates a flow diagram of an example method for determining an updated codebook, in accordance with some embodiments of the present disclosure;
fig. 6 illustrates a flow diagram of an example method implemented at a network device for determining downlink CSI in accordance with some embodiments of the present disclosure;
FIG. 7 shows a comparison of link-level simulations between the present scheme and the conventional scheme; and
fig. 8 is a simplified block diagram of an apparatus suitable for practicing embodiments of the present disclosure.
Throughout the drawings, the same or similar reference numbers refer to the same or similar elements.
Detailed Description
The principles of the present disclosure will now be described with reference to a few exemplary embodiments. It is understood that these examples are described solely to illustrate and assist those skilled in the art in understanding and practicing the disclosure, and are not meant to imply any limitations on the scope of the disclosure. The disclosure described herein may be implemented in various ways other than those described below.
In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard or protocol, such as Long Term Evolution (LTE), LTE-advanced (LTE-a), and 5G NR, and employs any suitable communication technology, including, for example, multiple-input multiple-output (MIMO), OFDM, Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), Code Division Multiplexing (CDM), bluetooth, ZigBee, Machine Type Communication (MTC), eMBB, MTC, and urrllc technologies. For purposes of discussion, in some embodiments, an LTE network, an LTE-a network, a 5G NR network, or any combination thereof are taken as examples of communication networks.
As used herein, the term "network device" refers to any suitable device on the network side of a communication network. The network device may comprise any suitable device in an access network of a communication network, including, for example, a Base Station (BS), a transmission point (TRP), a relay, an Access Point (AP), a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a gigabit NodeB (gnb), a remote radio module (RRU), a Radio Head (RH), a Remote Radio Head (RRH), a low power node such as a pico node (femto), a pico node (pico), and the like. For discussion purposes, in some embodiments, an eNB is taken as an example of a network device.
The network equipment may also include any suitable equipment in the core network, including, for example, multi-standard radio (MSR) radios such as MSR BSs, network controllers such as Radio Network Controllers (RNCs) or Base Station Controllers (BSCs), multi-cell/Multicast Coordination Entities (MCEs), Mobile Switching Centers (MSCs) and MMEs, operations and management (O & M) nodes, Operations Support Systems (OSS) nodes, self-organizing network (SON) nodes, positioning nodes such as enhanced serving mobile positioning centers (E-SMLCs), and/or Mobile Data Terminals (MDTs).
As used herein, the term "terminal device" refers to a device that can be configured, arranged, and/or operated for communication with a network device or another terminal device in a communication network. Communication may involve the transmission and/or reception of wireless signals using electromagnetic signals, radio waves, infrared signals, and/or other types of signals suitable for the communication of information in the air. In some embodiments, the terminal device may be configured to send and/or receive information without direct human interaction. For example, the terminal device may transmit information to the network device on a predetermined schedule when triggered by an internal or external event or in response to a request from the network side.
Examples of end devices include, but are not limited to, User Equipment (UE), such as a smart phone, a wireless-enabled tablet, a laptop embedded device (LEE), a laptop installed device (LME), and/or a wireless Customer Premises Equipment (CPE). For purposes of discussion, some embodiments will be described below with reference to a UE as an example of a terminal device, and the terms "terminal device" and "user equipment" (UE) may be used interchangeably within the context of this disclosure.
As used herein, the term "cell" refers to an area covered by radio signals transmitted by a network device. Terminal devices within a cell may be served by a network device and access a communication network through the network device.
As used herein, the term "circuitry" may refer to one or more or all of the following: (a) hardware-only circuit implementations (e.g., implementation in only analog and/or digital circuitry), and (b) combinations of hardware circuitry and software, e.g., (as applicable): (i) a combination of analog and/or digital hardware circuitry and software/firmware and (ii) any portion of a hardware processor with software (including digital signal processors, software, and memory that work together to cause a device such as a mobile phone or server to perform various functions), and (c) hardware circuitry and/or a processor, such as a microprocessor or a portion of a microprocessor, that requires software (e.g., firmware) for operation, but may not be present when software is not required for operation.
This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also encompasses implementations in which only a hardware circuit or processor (or multiple processors), or portion thereof, and its (or their) accompanying software and/or firmware. For example, the term circuitry, if applicable to a particular claim element, also encompasses a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, a cellular network device, or other computing or network device.
As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "including" and variations thereof is to be understood as meaning open-ended terms that include, but are not limited to. The term "based on" is to be understood as "based at least in part on". The terms "one embodiment" and "an embodiment" should be understood as "at least one embodiment". The term "another embodiment" should be understood as "at least one other embodiment". The terms "first," "second," and the like may refer to different or the same object. Other definitions, whether explicit or implicit, may be included below.
In some examples, a value, process, or device is referred to as "best," "lowest," "highest," "minimum," "maximum," or the like. It will be appreciated that such descriptions are intended to indicate that a selection may be made among many of the functional choices used, and that such choices need not be better, smaller, higher, or otherwise preferred over other choices.
As described above, since only a subset of all antennas at the terminal device can be used for transmission of uplink signals in a certain time slot, the terminal device should switch its antenna group to transmit SRS in a plurality of consecutive predetermined time slots, thereby helping the network device to get the complete downlink CSI. However, for different SRS configuration periods, it may take a longer period of time for the network device to get the full CSI of the user, and thus the CSI may be outdated compared to the actual channel used for downlink data transmission. In view of this, a conventional scheme based on joint uplink SRS transmission and uplink CSI feedback has been proposed.
In this scheme, in a given slot, the terminal device transmits an uplink SRS through a subset of its antennas, quantizes CSI of subchannels between the network device and unused antennas (not used for SRS transmission) through a common codebook, and feeds back the quantized CSI to the network device. The network device then combines the CSI of the sub-channels measured by the uplink SRS with the CSI of the other sub-channels restored by the same codebook feedback to derive the complete downlink CSI for the terminal device.
However, this approach may face more challenges for massive MIMO. Given the codebook size to control the uplink overhead, the quantization error will increase as the number of transmit antennas increases in a massive MIMO system. The reason is that quantizing a larger space using a codebook of a given size will reduce the quantization resolution. This conventional scheme should be further studied and optimized if the codebook size does not increase with the number of transmit antennas.
Embodiments of the present disclosure provide an improvement for employing adaptive codebook techniques to determine downlink CSI, thereby addressing the above-referenced problems and one or more other potential problems. The scheme for determining downlink CSI according to embodiments of the present disclosure enables higher quantization resolution, lower uplink overhead, and more accurate downlink CSI determination compared to conventional schemes. The principles and implementations of the present disclosure will be described in detail below with reference to fig. 1-8.
Fig. 1 illustrates an example communication network 100 in which embodiments of the present disclosure may be implemented. As shown in fig. 1, network 100 includes network device 110 and terminal device 120 serviced by network device 110. It should be understood that the number of network devices and terminal devices shown in fig. 1 is for illustrative purposes only and does not imply any limitation. Network 100 may include any suitable number of devices suitable for implementing embodiments of the present disclosure. It is to be appreciated that network device 110 can simultaneously schedule multiple users (e.g., terminal devices 120) for downlink transmission.
As shown in fig. 1, network device 110 and terminal device 120 may communicate with each other. Terminal device 120 may have multiple antennas for communicating with network device 110. For example, terminal device 120 may include four antennas 121, 122, 123, and 124. It should be understood that the number of antennas shown in fig. 1 is for illustrative purposes only and does not imply any limitation. Terminal device 120 may provide any suitable number of antennas suitable for implementing embodiments of the present disclosure. Further, it is to be understood that network device 110 may also have multiple antennas for communicating with terminal device 120, and that all antennas of network device 110 may be used for downlink signal transmission and uplink signal reception. Not shown here to avoid obscuring the invention.
Communications in network 100 may conform to any suitable standard including, but not limited to, Long Term Evolution (LTE), LTE evolution, LTE-advanced (LTE-a), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), global system for mobile communications (GSM), and the like. Further, the communication may be performed in accordance with any generation of communication protocols now known or later developed. Examples of communication protocols include, but are not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, and fifth generation (5G) communication protocols.
In some embodiments, all antennas at terminal device 120 may be used for reception of downlink signals to achieve receive combining gain, while in some particular time instance, only a subset of antennas may be used for transmission of uplink signals. To help network device 110 get the full downlink CSI, terminal device 120 will switch its antenna set to transmit uplink reference signals, such as SRS, in a plurality of consecutive predetermined time slots. Fig. 2 illustrates an example scenario 200 of antenna switching based uplink SRS transmission in which embodiments of the present disclosure may be implemented. Scenario 200 may be implemented at terminal device 120 shown in fig. 1. For purposes of discussion, this scenario 200 will be described with reference to FIG. 1.
As shown in FIG. 2, TSFDenotes the duration of a subframe, TSRSRepresenting the period of SRS transmission, TFRRepresenting the duration of a frame. E.g. t1、t6、t11、t16And t21Is an uplink time slot for terminal device 120. It is assumed in embodiments of the present disclosure that in each uplink slot, only one antenna is used for uplink SRS transmission. It can be appreciated that in alternative embodiments, more antennas may be used in each uplink slot for uplink SRS transmission.
E.g. in time slot t1In (3), the uplink SRS is transmitted only through the antenna 121. By antenna switching, at time slot t6Only the uplink SRS will be transmitted through the antenna 122. In time slot t11Only the uplink SRS will be transmitted through the antenna 123. In time slot t16Only the uplink SRS will be transmitted through the antenna 124. In time slot t21Again, only the uplink SRS will be transmitted through antenna 121. And so on for each subsequent uplink slot. In some embodiments, if TSRSTime slot t is 55(n-1)+iIs to be used for SRS transmission for the ith antenna, where n denotes the index of the current frame and i denotes the index of the antenna of the terminal device.
Hereinafter, a subset of antennas that are transmitting the uplink SRS in one uplink slot may also be collectively referred to as first antennas, and other antennas that are not transmitting the uplink SRS in the same uplink slot may also be collectively referred to as second antennas.
According to the concept of the present disclosure, for a subchannel between network device 110 and the first antenna of terminal device 120, network device 110 measures the uplink SRS and then derives the downlink CSI corresponding to the subchannel by exploiting the channel reciprocity between the downlink channel and the uplink channel. Meanwhile, for a subchannel between network device 110 and the second antenna of terminal device 120, network device 110 will restore the downlink CSI corresponding to the subchannel through feedback from terminal device 120 using a codebook that is adaptively updated based on the antenna switching described in connection with fig. 2.
Fig. 3 illustrates an exemplary interaction 300 between a network device and a terminal device according to some embodiments of the present disclosure. Interaction 300 may be implemented at network device 110 and terminal device 120 shown in fig. 1. For purposes of discussion, the interaction 300 will be described with reference to fig. 1 and 2. In this example, it will be for time slot t as shown in FIG. 21The interaction 300 is described. It should be understood that interaction 300 may include additional acts not shown and/or may omit some of the acts shown, and the scope of the present disclosure is not limited in this respect.
As shown in fig. 3, network device 110 transmits 301 a downlink reference signal to terminal devices in its serving cell, such as terminal device 120. For example, referring to FIG. 2, at time slot t1In the previous downlink time slot, network device 110 may transmit 301 a downlink reference signal. In some embodiments, network device 110 may periodically transmit a channel state information reference signal (CSI-RS). The transmission manner and form of the downlink reference signal are not limited thereto, and any suitable manner may be adopted.
Terminal device 120, upon receiving the downlink reference signal from network device 110, determines 302 a corresponding CSI for each subchannel between network device 110 and each antenna 121, 122, 123, and 124, e.g., by measuring the downlink reference signal for the corresponding subchannel. It will be appreciated that the measurement may be made in any suitable manner.
After determining the CSI for each subchannel, terminal device 120 determines 303 an updated codebook that is specific to terminal device 120 based on the CSI (also referred to as first CSI) for the subchannels between network device 110 and antenna 121. In some embodiments, the updated codebook is determined based on the first CSI and the historical CSI (also referred to as the historical second CSI) for each subchannel between network device 110 and the respective antennas 122, 123, and 124. In some embodiments, terminal device 120 may replace the historical CSI for the sub-channels between network device 110 and antennas 121 (also referred to as historical first CSI) with the first CSI and derive an updated codebook based on the first CSI and the historical second CSI. As used herein, historical CSI refers to CSI of subchannels between a network device and any one of the antennas of a terminal device, which CSI is obtained by the terminal device from downlink reference signals in one or more previous downlink time slots. The implementation of the determination 303 will be described in detail later with reference to fig. 5.
Based on the updated codebook, terminal device 120 quantizes 304 the CSI (also referred to as second CSI) for each subchannel between network device 110 and each antenna 122, 123, and 124. For example, quantization 304 may be performed by matching the CSI to a codeword in an update codebook. It should be understood that quantization may be performed by any suitable technique. In time slot t1In this case, terminal device 120 transmits 305 uplink SRS and quantized CSI to network device 110 via antenna 121.
Network device 110, upon receiving the uplink SRS and the quantized CSI, determines 306 a partial downlink CSI (also referred to as a first downlink CSI) corresponding to a subchannel between network device 110 and antenna 121 based on the uplink SRS, e.g., by measuring the uplink SRS for the subchannel. It will be appreciated that the measurement may be made in any suitable manner.
Based on the determined 306 partial downlink CSI, the network device 110 determines 307 an updated codebook that is specific to the terminal device 120. In some embodiments, the updated codebook is determined based on the first downlink CSI and historical downlink CSI (also referred to as historical second downlink CSI) for each subchannel between network device 110 and the respective antennas 122, 123, and 124. In some embodiments, network device 110 may replace the historical downlink CSI for the subchannel between network device 110 and antenna 121 (also referred to as historical first downlink CSI) with the first downlink CSI and derive the updated codebook based on the first downlink CSI and the historical second downlink CSI. As used herein, historical downlink CSI refers to downlink CSI of subchannels between the network device and any one of the antennas of the terminal device, the downlink CSI obtained by the network device from uplink SRS in one or more previous uplink slots. The process of determining 307 is similar to the process of determining 303, except that it is implemented by the network device based on the first downlink CSI, rather than by the terminal device based on the first CSI. For details, see the description below in detail with reference to fig. 5.
Based on the updated codebook determined at 307 and the quantized CSI received at 305, network device 110 determines 308 a remaining portion of downlink CSI (also referred to as second downlink CSI) corresponding to subchannels between network device 110 and each of antennas 122, 123, and 124. For example, the determination 308 may be made by matching the quantized CSI to a codeword in an update codebook. It should be understood that quantization may be performed by any suitable technique. Thus, network device 110 obtains the full downlink CSI associated with terminal device 120.
As used herein, the first downlink CSI refers to CSI of a subchannel between the network device and the first antenna, and the second downlink CSI refers to CSI of a subchannel between the network device and the second antenna.
Corresponding to the concepts described above with reference to fig. 1-3, the present disclosure provides methods implemented at a terminal device and a network device, respectively. Fig. 4 illustrates a flowchart of an example method 400 implemented at a terminal device for determining downlink CSI in accordance with some embodiments of the present disclosure. The method 400 may be implemented at the terminal device 120 shown in fig. 1. For discussion purposes, the method 400 will be described with reference to fig. 1. It should be understood that method 400 may include additional acts not shown and/or may omit some of the acts shown, and the scope of the present disclosure is not limited in this respect.
At block 410, terminal device 120 determines first CSI and second CSI based on downlink reference signals received from network device 110 through the first antenna and the second antenna of the terminal device, respectively. In this example, the first antenna is included in the time slot t1The second antenna is included in the time slot t1The remaining antennas 122, 123, and 124 that are not used for uplink SRS transmission. The process in block 410 is similar to operations 301 and 302 described in FIG. 3 and is therefore omitted here.
At block 420, terminal device 120 determines a terminal device specific update codebook based on the first CSI. In some embodiments, terminal device 120 may determine the updated codebook in response to receiving an indication from network device 110 to use the updated codebook. For example, network device 110 may choose to use the adaptive codebook and inform terminal device 120 of the adaptive codebook, depending on changes in network conditions, antenna configuration, or other factors. In some embodiments, an additional 1-bit signal may be designed to indicate the use of the updated codebook. It will be appreciated that other indications may be employed to indicate the use of an updated codebook. In this way, adaptive codebook-based operations may be aligned at the network device and the terminal device, including CSI quantization at the terminal device side and recovery at the network device side.
The process in block 420 is similar to operation 303 described in FIG. 3, which is now described in detail below with reference to FIG. 5. Fig. 5 illustrates a flow diagram of an example method 500 for determining an updated codebook, in accordance with some embodiments of the present disclosure. The method 500 may be implemented at the network device 110 or the terminal device 120 shown in fig. 1. For discussion purposes, the method 500 will be described with reference to fig. 1. It is to be understood that method 500 may include additional acts not shown and/or may omit some of the acts shown, and the scope of the present disclosure is not limited in this respect.
At block 510, the terminal device 120 may update corresponding portions of the downlink channel matrix associated with the first antenna and the second antenna based on the first CSI. In some embodiments, the first CSI and the second CSI may be maintained in a matrix form (which is also referred to as a downlink channel matrix). For example, assuming that the terminal device has N antennas (N is an integer greater than 1), the downlink channel matrix Hiter(t) can be written as:
Hiter(t)＝[h1(t),h2(t),…,hi(t),…,hN(t)] (1)
wherein h isi(t) represents the measured or quantized CSI for the subchannel between the network device and the ith antenna of the terminal device in time slot t.
In some embodiments, after determining the first CSI and the second CSI at block 410, terminal device 120 may update matrix H with the first CSIiterElement h of (t)1(t) while maintaining the matrix HiterThe other elements of (t) are unchanged. In some embodiments, the downlink channel matrix may be initialized to a null matrix. Antenna switching through uplink time slots, matrix HiterThe elements of (t) are iteratively updated so that the resulting CSI is more and more accurate.
At block 520, the terminal device 120 may determine a covariance matrix from the updated downlink channel matrix. In accordance with the concepts of the present disclosure, an iterative channel matrix H is studiediter(t) second order statistical properties. In some embodiments, the covariance matrix RiterCan be written as:
Figure BDA0002953605720000121
wherein the parameter T is a sliding window for downlink channel covariance matrix calculation.
Since wireless channels typically satisfy the generalized stationary uncorrelated scattering (WSSUS) model and characteristics, RiterApproximate the ideal downlink channel covariance matrix R over a large averaging period Ttheoretical. Ideal covarianceMatrix RtheoreticalIs calculated based on the ideal downlink channel. In general, a terminal device may derive R through downlink CSI-RS measurementstheoreticalAnd the network device cannot obtain R due to the uplink SRS transmission in multiple slotstheoreticalThus, the network device can utilize RiterThe user-specific adaptive codebook is designed.
By switching antennas and taking advantage of channel reciprocity between TDD downlink and uplink channels, terminal device 120 can derive a covariance matrix Riter. In each uplink time slot, a corresponding covariance matrix R may be determinediter。
At block 530, terminal device 120 may obtain an updated codebook based on the covariance matrix and the common codebook. In some embodiments, for example, assume that there is a common codebook C and codeword C of size Si(1. ltoreq. i. ltoreq.S), may be determined by concatenating each codeword C of the codebook CiAnd covariance matrix RiterThe codewords are multiplied and then normalized to obtain an updated codebook. Then, an adaptive codebook specific to the terminal device is generated.
For a given slot, if one antenna or a subset of antennas is selected for uplink SRS transmission, the subchannels between the TRP and the antennas in the given slot that did not transmit SRS will be quantized and fed back by the terminal device to the network device. The quantized downlink channel is recovered by the network device through the corresponding adaptive codebook, thereby expediting the update of the downlink CSI.
Traditionally, the codebook design in NR or LTE is for all users, covering a large space and limited codewords to reduce uplink overhead. Therefore, the conventional codebook has a lower spatial resolution for a massive MIMO system. In contrast, adaptive codebook designs according to the present disclosure may track the characteristics of the subchannels associated with the various antennas of the terminal device and improve the quantization resolution of the subspace.
In addition, the covariance matrix is known at both the network device and the terminal device, and no feedback is needed in the uplink channel, resulting in lower uplink overhead. In addition, since the adaptive codebook design is based on a common codebook, the codebook size is unchanged, and thus the uplink overhead is unchanged compared to the conventional scheme.
In addition to the embodiment shown in fig. 5, in alternative embodiments, the first CSI and the second CSI may be maintained in any other suitable matrix form, either existing or developed in the future. The manner of determining the updated codebook is not intended to be limited to the listed examples.
Referring to fig. 4, at block 430, terminal device 120 quantizes the second CSI based on the updated codebook. The process in block 430 is similar to operation 304 described in FIG. 3 and is therefore omitted here. In block 440, terminal device 120 transmits the uplink SRS and the quantized CSI to network device 110 through the first antenna. The process in block 440 is similar to operation 305 described in fig. 3 and is therefore omitted here.
Based on the joint adaptive codebook and antenna switching SRS transmission, accurate downlink CSI associated with a particular terminal device may be obtained, and thus multi-user parsing and transmit precoder design may be significantly improved.
Fig. 6 illustrates a flowchart of an example method 600 implemented at a network device for determining downlink CSI in accordance with some embodiments of the present disclosure. The method 600 may be implemented at the network device 110 shown in fig. 1. For discussion purposes, the method 600 will be described with reference to fig. 1. It should be understood that method 600 may include additional acts not shown and/or may omit some of the acts shown, and the scope of the present disclosure is not limited in this respect.
At block 610, network device 110 receives the uplink SRS and quantized CSI from terminal device 120. In this example, the uplink SRS and the quantized CSI may be transmitted through the antenna 121. The process in block 610 is similar to operation 305 described in FIG. 3 and is therefore omitted here.
At block 620, network device 110 determines first downlink CSI associated with the first antenna of terminal device 120 based on the SRS. The process in block 620 is similar to operation 306 described in FIG. 3. In some embodiments, network device 110 may obtain the first downlink CSI by measuring SRS and determine an association of the first downlink CSI with the first antenna. In this case, network device 110 may determine which antenna is the first antenna in the current slot, i.e., through which SRS is transmitted.
In some embodiments, network device 110 may determine which antenna is the first antenna in the current time slot as follows. Let L be NXTSRSN is the number of antennas of the terminal device, TSRSRepresenting the period of SRS transmission. At time slot t, the index μ of the last antenna transmitting the uplink SRS may be determined as:
Figure BDA0002953605720000141
wherein,
Figure BDA0002953605720000142
is the function that finds the smallest maximum integer compared to the input parameters, mod (□) is the modulus function.
In some embodiments, the subchannel between the network device and the ith antenna (whose index is not greater than μ) of the terminal device is in time slot tiIs updated and can be represented as
ti＝t-(μ-1)TSRS-mod(t,TSRS),i≤μ (4)
Meanwhile, a subchannel between the network equipment and the jth antenna (the index of which is more than mu) of the terminal equipment is in a time slot tjIs updated and can be represented as
tj＝t-mod(t,TSRS)+(i-μ)TSRS-L (5)
In this way, subsequent determinations of updated codebooks may be facilitated. In other words, this determines the CSI associated with the antenna to be updated in the current time slot. It will be appreciated that any other suitable manner of determining which antenna to update may be employed. For example, the network device may record the antenna switching associated with each terminal device so that the source of the received SRS is known.
At block 630, network device 110 determines a terminal device-specific updated codebook based on the first downlink CSI. In some embodiments, network device 110 may determine to update the codebook in response to receiving an indication from terminal device 120 to use the updated codebook. For example, terminal device 120 may choose to use the adaptive codebook and inform network device 110 of the adaptive codebook, depending on changes in network conditions, antenna configuration, or other factors. In some embodiments, an additional 1-bit signal may be designed to indicate the use of the updated codebook. It will be appreciated that other indications may be employed to indicate the use of the updated codebook. In this way, adaptive codebook-based operations may be aligned at the network device and the terminal device, including CSI quantization at the terminal device side and recovery at the network device side.
The process in block 630 is similar to operation 307 described in fig. 3. The process in operation 307 is similar to the process in operation 303, except that it is implemented by the network device based on the first downlink CSI instead of being implemented by the terminal device based on the first CSI. The details thereof are as described in connection with fig. 5 and are therefore omitted here for the sake of brevity.
At block 640, the network device 110 determines second downlink CSI associated with the second antenna of the terminal device based on the updated codebook and the quantized CSI. The process in block 640 is similar to the process in operation 308 and is therefore omitted here for the sake of brevity. In this way, network device 110 can quickly and accurately obtain the full downlink CSI associated with terminal device 120 with low uplink overhead.
Compared with the traditional scheme, the scheme adopts the self-adaptive codebook technology to improve the quantization resolution of the given codebook. This helps the network device to get more accurate and complete user downlink CSI in time for improved multi-user scheduling and multi-user interference pre-cancellation. More importantly, the present scheme can significantly improve the performance of massive MIMO systems without any additional overhead in the uplink channel.
Fig. 7 shows a comparison of a link level simulation of the present scheme with a conventional scheme, showing the Spectral Efficiency (SE) versus the signal-to-noise ratio (SNR). The key parameters of the simulation are shown in table 1 below.
TABLE 1
Figure BDA0002953605720000161
In fig. 7, 6 schemes are evaluated and compared in order to fully illustrate the performance of each scheme.
Scheme 1, as shown at 710 in fig. 7, involves a "perfect full CSI upper bound". In this case, it is assumed that the network device can obtain perfect downlink information at each subframe, and achieve optimal multiuser scheduling and transmission precoder design. Its performance is an upper limit of massive MIMO systems.
Scheme 2 as shown at 720 in fig. 7 relates to an "ideal channel based adaptive codebook, where SRS period is 4 ms". In this scheme, an adaptive codebook is implemented based on an ideal downlink channel covariance matrix for both the network device and the terminal device. The purpose of this scheme is to verify RiterImpact on multi-user performance. The SRS transmission period is 4 ms.
Scheme 3, as shown at 730 in fig. 7, relates to an "iterative channel based adaptive codebook, where the SRS period is 4 ms". In this scheme, the adaptive codebook is implemented based on the iterative downlink channel covariance as shown in equation (2) for both the network device and the terminal device. The SRS period is also configured to be 4ms for comparison with an ideal adaptive codebook based on downlink channel covariance.
Scheme 4, as shown at 740 in fig. 7, involves "full CSI, where SRS period is 4 ms". In this scheme, H for downlink CSI associated with a particular terminal device is used at the network deviceiterTo perform multi-user scheduling and transmission precoder design.
Scheme 5, as shown at 750 in fig. 7, relates to the "SRS + R13 codebook". This is a conventional scheme that employs partial SRS transmission and channel quantization and feedback based on a common codebook.
Scheme 6 as shown by 760 in figure 7 relates to the "FDD R13 codebook". In this scheme, the downlink CSI associated with a particular terminal device is quantized only by the existing codebook. This scheme is used to check FDD massive MIMO performance.
In case 5 and case 6, it is assumed that there is a time delay between uplink SRS transmission, codebook feedback, and downlink transmission, which is the upper limit performance of the conventional scheme and FDD massive MIMO system.
From the simulation results shown in fig. 7, the following conclusions can be drawn:
this scheme (scheme 3) outperforms the conventional scheme (scheme 4/scheme 5) in all SNR regions without introducing additional uplink overhead, which can be used for both the use of the cell center with high SNR and the use of the cell edge with low SNR.
This scheme (scheme 3) can achieve the same performance as the adaptive coding scheme based on the ideal channel (scheme 2). This means that if more accurate CSI is needed, the size of the common codebook needs to be enlarged as the SNR increases. The trade-off between performance and overhead should be further optimized.
The conventional scheme can be used only for a low SNR region or only for cell edge users, which limits its application range.
For a codebook of limited size, the performance of a non-ideal TDD massive MIMO system is better than that of an FDD massive MIMO system. The performance gap increases significantly as the SNR increases.
In some embodiments, an apparatus (e.g., terminal device 120) capable of performing method 400 may include means for performing the respective steps of method 400. The components may be implemented in any suitable form. For example, the components may be implemented in circuits or software modules.
In some embodiments, the apparatus comprises: means for determining first CSI and second CSI based on downlink reference signals received from a network device through first and second antennas of a terminal device, respectively; means for determining a terminal device-specific update codebook based on the first CSI; means for quantizing the second CSI based on the update codebook; and means for transmitting the uplink SRS and the quantized CSI to the network device through the first antenna.
In some embodiments, the means for determining an updated codebook comprises: means for updating corresponding portions of the downlink channel matrix associated with the first antenna and the second antenna based on the first CSI; means for determining a covariance matrix from the updated downlink channel matrix; and means for obtaining an updated codebook based on the covariance matrix and the common codebook.
In some embodiments, the downlink channel matrix is initialized to a null matrix.
In some embodiments, the means for determining an updated codebook comprises: means for receiving an indication from a network device of use of an updated codebook; and means for determining to update the codebook in response to receiving the indication.
In some embodiments, an apparatus (e.g., network device 110) capable of performing the method 600 may include means for performing the respective steps of the method 600. The component may be embodied in any suitable form. For example, the components may be implemented in circuits or software modules.
In some embodiments, the apparatus comprises: means for receiving an uplink SRS and quantized CSI from a terminal device; means for determining first downlink CSI associated with a first antenna of a terminal device based on the SRS; means for determining a terminal device-specific update codebook based on the first downlink CSI; and means for determining second downlink CSI associated with a second antenna of the terminal device based on the updated codebook and the quantized CSI.
In some embodiments, the means for determining an updated codebook comprises: means for updating corresponding portions of the downlink channel matrix associated with the first antenna and the second antenna based on the first downlink CSI; means for determining a covariance matrix from the updated downlink channel matrix; and means for obtaining an updated codebook based on the covariance matrix and the common codebook.
In some embodiments, the downlink channel matrix is initialized to a null matrix.
In some embodiments, the means for determining the first downlink CSI comprises: means for obtaining first downlink CSI by measuring SRS; and means for determining an association of the first downlink CSI with the first antenna.
In some embodiments, the means for determining an updated codebook comprises: means for receiving an indication from a terminal device of use of an updated codebook; and means for determining to update the codebook in response to receiving the indication.
Fig. 8 is a simplified block diagram of a device 800 suitable for implementing embodiments of the present disclosure. Device 800 may be considered another example implementation of network device 110 or terminal device 120 as shown in fig. 1. Accordingly, device 800 may be implemented at network device 110 or terminal device 120 or as at least a portion of network device 110 or terminal device 120.
As shown, device 800 includes a processor 810, a memory 820 coupled to processor 810, a suitable Transmitter (TX) and Receiver (RX)840 coupled to a processing component 850 configured with processor 810 and memory 820, and a communication interface coupled to TX/RX 840. Memory 820 stores at least a portion of program 830. TX/RX 840 is used for bi-directional communication. TX/RX 840 has at least one antenna to facilitate communication, although in practical applications several antennas are possible for the access node mentioned in this application. The communication interface may represent any interface required for communication with other network elements, such as an X2 interface for bidirectional communication between enbs, an S1 interface for communication between a Mobile Management Entity (MME)/serving gateway (S-GW) and an eNB, a Un interface for communication between an eNB and a Relay Node (RN), or a Uu interface for communication between an eNB and a terminal device.
The program 830 is considered to include program instructions that, when executed by the associated processor 810, cause the device 800 to operate in accordance with embodiments of the present disclosure, as discussed herein with reference to fig. 4 or 6. The embodiments herein may be implemented by computer software executable by the processor 810 of the device 800, or by hardware, or by a combination of software and hardware. The processor 810 may be configured to implement various embodiments of the present disclosure. Further, the combination of processor 810 and memory 820 may form a processing component 850 suitable for implementing various embodiments of the present disclosure.
The memory 820 may be of any type suitable to the local technology network and may be implemented using any suitable data storage technology, such as non-transitory computer-readable storage media, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. Although only one memory 820 is shown in device 800, there may be several physically distinct memory modules in device 800. The processor 810 may be of any type suitable for a local technology network, and may include, as non-limiting examples, one or more of the following: general purpose computers, special purpose computers, microprocessors, Digital Signal Processors (DSPs) and processors based on a multi-core processor architecture. Device 800 may have multiple processors, such as application specific integrated circuit chips that are time-dependent from a clock synchronized to the main processor.
In general, the various example embodiments of this disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Certain aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While aspects of embodiments of the disclosure are illustrated or described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, that are executed in a device on a target real or virtual processor to perform the methods or processes described above with reference to fig. 4 or 6. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions of program modules may be executed within a local device or within a distributed device. In a distributed facility, program modules may be located in both local and remote memory storage media.
Computer program code for implementing the methods of the present disclosure may be written in one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/acts specified in the flowchart and/or block diagram to be performed. The program code may execute entirely on the computer, partly on the computer, as a stand-alone software package, partly on the computer and partly on a remote computer or entirely on the remote computer or server.
In the context of the present disclosure, computer program code or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations described above. Examples of the carrier include a signal, computer readable medium.
The program code described above may be embodied on a machine-readable medium, which may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More detailed examples of a machine-readable storage medium include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
Additionally, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be beneficial. Likewise, while the above discussion contains certain specific implementation details, this should not be construed as limiting the scope of any present disclosure, but rather as a description of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.
Although the disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims (22)

1. A terminal device, comprising:
a processor; and
a memory coupled to the processor and having instructions stored thereon that, when executed by the processor, cause the terminal device to perform acts comprising:
determining first Channel State Information (CSI) and second Channel State Information (CSI) based on downlink reference signals received from a network device through a first antenna and a second antenna of the terminal device, respectively;
determining an update codebook specific to the terminal device based on the first CSI;
quantizing the second CSI based on the update codebook; and
transmitting, by the first antenna, an uplink Sounding Reference Signal (SRS) and the quantized CSI to a network device.
2. The terminal device of claim 1, wherein determining the updated codebook comprises:
updating, based on the first CSI, corresponding portions of a downlink channel matrix associated with the first antenna and the second antenna;
determining a covariance matrix from the updated downlink channel matrix; and
obtaining the updated codebook based on the covariance matrix and a common codebook.
3. The terminal device of claim 2, wherein the downlink channel matrix is initialized to a null matrix.
4. The terminal device of claim 1, wherein determining the updated codebook comprises:
receiving an indication from the network device to use the updated codebook; and
determining the updated codebook in response to the receiving of the indication.
5. A network device, comprising:
a processor; and
a memory coupled to the processor and having instructions stored thereon that, when executed by the processor, cause the network device to perform acts comprising:
receiving an uplink Sounding Reference Signal (SRS) and quantized Channel State Information (CSI) from a terminal device;
determining, based on the SRS, first downlink CSI associated with a first antenna of the terminal device;
determining an update codebook specific to the terminal device based on the first downlink CSI; and
determining second downlink CSI associated with a second antenna of the terminal device based on the updated codebook and the quantized CSI.
6. The network device of claim 5, wherein determining the updated codebook comprises:
updating, based on the first downlink CSI, corresponding portions of a downlink channel matrix associated with the first antenna and the second antenna;
determining a covariance matrix from the updated downlink channel matrix; and
and obtaining the updated codebook based on the covariance matrix and the public codebook.
7. The network device of claim 6, wherein the downlink channel matrix is initialized to a null matrix.
8. The network device of claim 5, wherein determining the first downlink CSI comprises:
obtaining the first downlink CSI by measuring the SRS; and
determining the association of the first downlink CSI with the first antenna.
9. The network device of claim 5, wherein determining the updated codebook comprises:
receiving an indication from the terminal device to use the updated codebook; and
determining the updated codebook in response to the receiving of the indication.
10. A method implemented at a terminal device, comprising:
determining first Channel State Information (CSI) and second Channel State Information (CSI) based on downlink reference signals received from a network device through a first antenna and a second antenna of the terminal device, respectively;
determining an update codebook specific to the terminal device based on the first CSI;
quantizing the second CSI based on the update codebook; and
transmitting, by the first antenna, an uplink Sounding Reference Signal (SRS) and the quantized CSI to a network device.
11. The method of claim 10, wherein determining the updated codebook comprises:
updating, based on the first CSI, corresponding portions of a downlink channel matrix associated with the first antenna and the second antenna;
determining a covariance matrix from the updated downlink channel matrix; and
and obtaining the updated codebook based on the covariance matrix and the public codebook.
12. The method of claim 11, wherein the downlink channel matrix is initialized to a null matrix.
13. The method of claim 10, wherein determining the updated codebook comprises:
receiving an indication from the terminal device to use the updated codebook; and
determining the updated codebook in response to the receiving of the indication.
14. A method implemented at a network device, comprising:
receiving an uplink Sounding Reference Signal (SRS) and quantized Channel State Information (CSI) from a terminal device;
determining, based on the SRS, first downlink CSI associated with a first antenna of the terminal device;
determining an update codebook specific to the terminal device based on the first downlink CSI; and
determining second downlink CSI associated with a second antenna of the terminal device based on the updated codebook and the quantized CSI.
15. The method of claim 14, wherein determining the updated codebook comprises:
updating, based on the first downlink CSI, corresponding portions of a downlink channel matrix associated with the first antenna and the second antenna;
determining a covariance matrix from the updated downlink channel matrix; and
and obtaining the updated codebook based on the covariance matrix and the public codebook.
16. The method of claim 15, wherein the downlink channel matrix is initialized to a null matrix.
17. The method of claim 14, wherein determining the first downlink CSI comprises:
obtaining the first downlink CSI by measuring the SRS; and
determining the association of the first downlink CSI with the first antenna.
18. The method of claim 14, wherein determining the updated codebook comprises:
receiving an indication from the terminal device to use the updated codebook; and
determining the updated codebook in response to the receiving of the indication.
19. An apparatus implemented at a terminal device, comprising:
means for determining first Channel State Information (CSI) and second Channel State Information (CSI) based on downlink reference signals received from a network device through first and second antennas of the terminal device, respectively;
means for determining an update codebook that is specific to the terminal device based on the first CSI;
means for quantizing the second CSI based on the update codebook; and
means for transmitting an uplink Sounding Reference Signal (SRS) and the quantized CSI to a network device through the first antenna.
20. An apparatus implemented at a network device, comprising:
means for receiving an uplink Sounding Reference Signal (SRS) and quantized Channel State Information (CSI) from a terminal device;
means for determining first downlink CSI associated with a first antenna of the terminal device based on the SRS;
means for determining an updated codebook that is specific to the terminal device based on the first downlink CSI; and
means for determining second downlink CSI associated with a second antenna of a terminal device based on the updated codebook and the quantized CSI.
21. A computer-readable storage medium having stored thereon instructions that, when executed on at least one processor, cause the at least one processor to perform the method of any one of claims 10 to 13.
22. A computer-readable storage medium having stored thereon instructions that, when executed on at least one processor, cause the at least one processor to perform the method of any one of claims 14 to 18.
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Publication number Priority date Publication date Assignee Title
CN114268390A (en) * 2021-12-27 2022-04-01 中国电信股份有限公司 RSRP switching point determining method, device, medium and electronic equipment
CN114268390B (en) * 2021-12-27 2024-08-27 中国电信股份有限公司 RSRP switching point determining method, device, medium and electronic equipment

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