CN119631371A

CN119631371A - Beamforming scheme

Info

Publication number: CN119631371A
Application number: CN202280098704.XA
Authority: CN
Inventors: 刘皓; S·韦泽曼; R·阿梅德; 赵岩; 杨涛; 宋暖
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2022-07-28
Filing date: 2022-07-28
Publication date: 2025-03-14
Also published as: WO2024020951A1

Abstract

Embodiments of the present disclosure relate to beamforming schemes. A network device includes at least one processor; and at least one memory storing instructions. The instructions, when executed by the at least one processor, cause the network device to at least: divide a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices; determine beamforming weights associated with transmission of a downlink reference signal from the network device to the terminal device group for a terminal device group in the plurality of groups; and send a downlink reference signal precoded by the beamforming weights to the terminal devices in the terminal device group. In this way, the beamforming gain of the transmission of the downlink reference signal can be increased with controlled resource overhead.

Description

Beamforming scheme

Technical Field

Various example embodiments relate to the field of telecommunications and, in particular, to methods, apparatus, devices, and computer-readable storage media for beamforming schemes.

Background

A 5G massive multiple-input multiple-output (MIMO) system uses beamforming to maximize the antenna gain of a user. These schemes are critical to achieving high gain in massive MIMO systems. One of the beamforming schemes for massive MIMO refers to a scheme in which a UE-specific beam Grid (GOB) beam can be selected for different UEs. Alternatively, the common GoB beams may be weighted for UEs within the cell. There remains a need for efficient beamforming solutions in such deployments.

Disclosure of Invention

In general, example embodiments of the present disclosure provide a solution for performing beamforming on transmissions in a massive MIMO system.

In a first aspect, a network device is provided. The network device includes at least one processor and at least one memory storing instructions. The instructions, when executed by the at least one processor, cause the network device to at least divide a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices, determine beamforming weights associated with transmission of downlink reference signals from the network device to the terminal device groups for the terminal device groups in the plurality of groups, and transmit downlink reference signals precoded by the beamforming weights to the terminal devices in the terminal device groups.

In a second aspect, a terminal device is provided. The terminal device includes at least one processor and at least one memory storing instructions. The instructions, when executed by the at least one processor, cause the terminal device to at least receive configuration information from a network device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices including the terminal device, and receive downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices from the network device based on the group-specific resource configuration.

In a third aspect, a method is provided. The method includes dividing, at a network device, a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices, determining, for a group of terminal devices in the plurality of groups, beamforming weights associated with transmission of downlink reference signals from the network device to the group of terminal devices, and transmitting, to terminal devices in the group of terminal devices, downlink reference signals precoded by the beamforming weights.

In a fourth aspect, a method is provided. The method includes receiving, at a terminal device, configuration information from a network device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices including the terminal device, and receiving, from the network device, downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices based on the group-specific resource configuration.

In a fifth aspect, an apparatus is provided. The apparatus includes means for dividing, at a network device, a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices, means for determining, for a group of terminal devices in the plurality of groups, beamforming weights associated with transmission of downlink reference signals from the network device to the group of terminal devices, and means for transmitting, to terminal devices in the group of terminal devices, downlink reference signals precoded by the beamforming weights.

In a sixth aspect, an apparatus is provided. The apparatus includes means for receiving, at a terminal device, configuration information from a network device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices including the terminal device, and means for receiving, from the network device, downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices based on the group-specific resource configuration.

In a seventh aspect, a computer readable medium is provided. The computer readable medium comprises program instructions which, when executed by an apparatus, cause the apparatus to perform at least the method according to any of the third or fourth aspects described above.

In an eighth aspect, a computer program is provided. The computer program includes instructions. The instructions, when executed by the apparatus, cause the apparatus at least to divide a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices, determine beamforming weights associated with transmission of downlink reference signals from a network device to the group of terminal devices for the group of terminal devices in the plurality of groups, and transmit downlink reference signals precoded by the beamforming weights to the terminal devices in the group of terminal devices.

In a ninth aspect, a computer program is provided. The computer program includes instructions. The apparatus comprises means for receiving configuration information from a network device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices comprising the terminal device, and means for receiving downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices from the network device based on the group-specific resource configuration.

In a tenth aspect, a network device is provided. The network device includes grouping circuitry configured to divide a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices, determining circuitry configured to determine beamforming weights associated with transmission of downlink reference signals from the network device to the terminal device groups for the terminal device groups in the plurality of groups, and transmitting circuitry configured to transmit the downlink reference signals precoded by the beamforming weights to the terminal devices in the terminal device groups.

In an eleventh aspect, a terminal device is provided. The terminal device includes configuration receiving circuitry configured to receive configuration information from a network device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices including the terminal device, and signal receiving circuitry configured to receive downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices from the network device based on the group-specific resource configuration.

It should be understood that the 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 apparent from the following description.

Drawings

Some example embodiments will now be described with reference to 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 signaling flows for communication according to some embodiments of the present disclosure;

fig. 3 illustrates an example of a port arrangement in an antenna array to which some example embodiments of the present disclosure may be applied;

fig. 4 illustrates an example of CSI-RS resource configuration to which some example embodiments of the present disclosure may be applied;

FIG. 5 illustrates an example implementation of a process for communication according to an embodiment of the disclosure;

FIGS. 6A and 6B illustrate spectral efficiency comparisons of embodiments of the present disclosure and related schemes;

fig. 7 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

Fig. 8 illustrates a flow chart of a method implemented at a terminal device according to some embodiments of the present disclosure;

FIG. 9 illustrates a simplified block diagram of an apparatus suitable for practicing embodiments of the present disclosure, and

Fig. 10 illustrates a block diagram of an example computer-readable medium, according to some embodiments of the disclosure.

The same or similar reference numbers will be used throughout the drawings to refer to the same or like elements.

Detailed Description

Principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described for illustrative purposes only and to assist those skilled in the art in understanding and practicing the present disclosure, and are not meant to limit the scope of the present disclosure in any way. The disclosure described herein may be implemented in various other ways besides 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.

In this disclosure, references to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It will be understood that, although the terms "first" and "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term "and/or" includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. 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. It will be further understood that the terms "comprises," "comprising," "has," "including," "includes" and/or "including" when used herein, specify the presence of stated features, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. As used herein, "at least one of" < list of two or more elements > "and" < at least one of list of two or more elements > "and similar expressions (where the list of two or more elements is connected by" and "or") refer to at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

As used herein, the term "circuitry" may refer to one or more or all of the following:

(a) A pure hardware circuit implementation (such as an implementation using only analog and/or digital circuitry), and

(B) A combination of hardware circuitry and software, such as (as applicable):

(i) Combination of analog and/or digital hardware circuit(s) and software/firmware, and

(Ii) Any portion of the hardware processor(s) (including digital signal processor(s), software, and memory(s) with software that work together to cause a device (such as a mobile phone or server) to perform various functions), and

(C) Hardware circuit(s) and/or processor(s), such as microprocessor(s) or portion of microprocessor(s), that require software (e.g., firmware) to operate, but software may not exist when operation is not required.

The definition of circuitry is applicable to all uses of that term in the present application, including in any claims. As another example, as used in this disclosure, the term circuitry also encompasses hardware-only circuits or processors (or multiple processors) or an implementation of a hardware circuit or processor portion and its accompanying software and/or firmware. For example, if applicable to the particular claim elements, the term circuitry 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 term "communication network" refers to a network that conforms to any suitable communication standard, such as Long Term Evolution (LTE), LTE-advanced (LTE-a), wideband Code Division Multiplexing (WCDMA), high Speed Packet Access (HSPA), narrowband internet of things (NB-IoT), and the like. Furthermore, communication between the terminal device and the network device in the communication network may be performed according to any suitable generation communication protocol, including, but not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) communication protocols, and/or any other protocol now known or later developed. Embodiments of the present disclosure may be applied in various communication systems. In view of the rapid development of communications, there will of course also be future types of communication technologies and systems that can be used to embody the present disclosure. It should not be taken as limiting the scope of the present disclosure to only the above-described systems.

As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services from the network. Depending on the terminology and technology applied, a network device may refer to a Base Station (BS) or Access Point (AP), e.g., a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a Radio Header (RH), a Remote Radio Head (RRH), a relay, a low power node (such as femto, pico), etc.

The term "terminal device" refers to any terminal device capable of wireless communication. By way of example, and not limitation, a terminal device may also be referred to as a communication device, user Equipment (UE), subscriber Station (SS), portable subscriber station, mobile Station (MS), or Access Terminal (AT). The terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal Digital Assistants (PDAs), portable computers, desktop computers, image capture terminal devices (such as digital cameras), gaming terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, notebook computer embedded devices (LEEs), laptop computer mounted devices (LMEs), USB dongles, smart devices, wireless Customer Premises Equipment (CPE), internet of things (IoT) devices, watches or other wearable devices, head Mounted Displays (HMDs), vehicles, drones, medical devices and applications (e.g., tele-surgery), industrial devices and applications (e.g., robots and/or other wireless devices operating in an industrial and/or automated processing chain environment), consumer electronic devices, devices operating on commercial and/or industrial wireless networks, and the like. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

Massive MIMO (MIMO) and beamforming are widely used in the telecommunications industry. The terms "beamforming" and "mMIMO" are sometimes used interchangeably. In general, beamforming uses multiple antennas to control the direction of the wavefront by appropriately weighting the amplitude and phase of individual antenna signals in an array of multiple antennas. The most common definition is mMIMO is a system where the number of antennas exceeds the number of users. The coverage of 5G is beam-based, not cell-based. There are no cell-level reference channels in which the coverage of a cell can be measured. Instead, each cell has one or more synchronization signals and physical broadcast channel block (SSB) beams. SSB beams are static or semi-static, always pointing in the same direction. They form a beam grid covering the whole cell area. A User Equipment (UE) searches for and measures beams, maintaining a set of candidate beams. The candidate beam set may comprise beams from a plurality of cells. As 5G millimeter wave (mmWave) is able to directionally communicate with more antenna elements and provide additional beamforming gain, efficient beam management, where the UE and the gNB periodically identify the best beam at any given point in time, becomes critical.

As described above, massive MIMO technology is one of the important solutions for a 5G New Radio (NR) system to acquire high gain. Ideally, a beamforming scheme should be able to achieve high system performance (e.g., spectral efficiency) without excessive implementation complexity. The performance of the beamforming scheme depends on the algorithm used and the type and amount of information required by the algorithm. Typically, in 5G, downlink (DL) CSI-RS resources are configured for the terminal device, and CSI RSs may be transmitted to the terminal device using the CSI-RS resources to measure DL channel states and obtain corresponding CSI feedback (including RI/PMI/CQI). The appropriate GoB beams are weighted on the CSI-RS resources to achieve beamforming gain and reasonable CSI-RS coverage.

Conventionally, if the GoB beams are selected for different terminal apparatuses, CSI-RS resources can be specifically configured for the different terminal apparatuses by respectively weighting the selected GoB beams, so that UE-specific CSI-RS achieves better CSI measurement and feedback quality. However, as the number of active terminal devices increases, CSI-RS overhead may become large. On the other hand, if the cell-specific CSI-RS resources are configured to be common to different terminal devices within the cell, the common GoB beam is weighted on the cell-specific resources. Although the CSI-RS overhead is greatly reduced, the accuracy of CSI feedback may be affected due to the limited BF gain. How to effectively improve the accuracy of CSI measurement and reduce CSI-RS resource overhead can be a big challenge faced by massive MIMO systems.

According to an embodiment of the present disclosure, a solution for a beamforming scheme in transmission of a massive MIMO system is provided. The principles and embodiments of the present disclosure will be described in detail below with reference to the drawings. It should be noted, however, that these examples are given to enable one skilled in the art to practice the solutions presented herein and are not intended to limit the scope of the application in any way.

Reference is first made to fig. 1, which illustrates an example communication system 100 in which embodiments of the present disclosure may be implemented. The system 100 (which is part of a communication network) includes a plurality of terminal devices, such as terminal devices 110-1, 110-2, 110-3, and 110-8, which may be collectively referred to as "terminal devices 110". The number of terminal devices may be any suitable integer.

Communication system 100 also includes network device 120. In the communication system 100, the network device 120 and the terminal device 110 can transmit data and control information to each other as long as the terminal device is located in a corresponding cell. Network device 120 may have multiple beams, such as beams 130-1, 130-2, 130-3, and 130-4, and each terminal device may have at least one beam (not shown). An effective channel (or sub-channel in this case) may be formed between the antenna precoded by one of the beams 130-1, 130-2, 130-3, and 130-4 of the network device and the antenna of the terminal device. Network device 120 may send information to terminal device 110 or receive information from terminal device 110 via one or more of beams 130-1, 130-2, 130-3, and 130-4.

In a communication system, "UL" refers to a communication link in a direction from a terminal device to a network device, and "DL" refers to a communication link in a direction from a network device to a terminal device.

It should be understood that the number of beams, network devices and terminal devices are given for illustrative purposes only and are not meant to be limiting in any way. System 100 may include any suitable number of network devices and/or terminal devices and/or beams suitable for implementing embodiments of the present disclosure.

Communication in communication system 100 may be implemented in accordance with any suitable communication protocol(s), including but not limited to first generation (1G), second generation (2G), third generation (3G), fourth generation (4G), and fifth generation (5G) cellular communication protocols, wireless local area network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, and/or any other protocol currently known or to be developed in the future. In addition, the communication may utilize any suitable wireless communication technology including, but not limited to, code Division Multiple Access (CDMA), frequency Division Multiple Access (FDMA), time Division Multiple Access (TDMA), frequency Division Duplex (FDD), time Division Duplex (TDD), multiple Input Multiple Output (MIMO), orthogonal Frequency Division Multiplexing (OFDM), discrete Fourier transform spread OFDM (DFT-s-OFDM), and/or any other technology currently known or to be developed in the future.

Embodiments of the present disclosure will be described in detail below. Referring now to fig. 2, a signaling diagram of a process 200 between a terminal device and a network device according to some example embodiments of the present disclosure is shown. For discussion purposes only, the process 200 will be described with reference to fig. 1. Process 200 may relate to terminal device 110-1 and network device 120 in fig. 1.

In process 200, network device 120 divides 210 a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices. The plurality of terminal devices may include terminal devices 110-1, 110-2, 110-3, a.the., and 110-8 that have established a connection with network device 120 and are thus located within corresponding cells of network device 120. In some embodiments, the number of divided groups may be preconfigured or determined by the network device 120 and may be equal to or less than the number of CSI-RS resources configured for the cell. For example, four CSI-RS resources may be configured for a cell, and a plurality of terminal devices may be divided into four groups. Group a may include terminal devices 110-1, 110-2, and 110-3, group B may include terminal device 110-4, group C may include terminal devices 110-5 and 110-6, and group D may include terminal devices 110-7 and 110-8.

The network device 120 determines 212 beamforming weights associated with transmission of downlink reference signals from the network device to the group of terminal devices in the plurality of groups for the group of terminal devices. For example, network device 120 may determine beamforming weights associated with transmission of downlink reference signals from network device 120 to group A including terminal devices 110-1, 110-2, and 110-3. The network device 120 sends 220 to the terminal device 110-1 a downlink reference signal 222 precoded by the determined beamforming weights. Terminal device 110-1 receives 224 downlink reference signals 222 precoded by the determined beamforming weights. In this way, the beamforming gain of the transmission of the downlink reference signal may be increased without increasing the resource overhead.

In some embodiments, network device 120 may send 214 configuration information 216 to terminal device 110-1. Configuration information 216 indicates a group-specific resource configuration for downlink reference signals to be transmitted from network device 120 to a group of terminal devices. Terminal device 110-1 may receive 218 configuration information 216. In this way, the terminal device may only measure a specific reference signal, instead of multiple reference signals, which reduces the implementation complexity of the terminal device.

In some embodiments, the network device 120 may transmit the downlink reference signal 222 precoded by the determined beamforming weights based on the group-specific resource configuration. Terminal device 110-1 may receive 224 the downlink reference signal based on the group-specific resource configuration. In this way, DL channel measurement accuracy may be improved.

In some embodiments, the network device 120 may transmit the configuration information 216 via at least one of Radio Resource Control (RRC) signaling, a Medium Access Control (MAC) Control Element (CE), or Downlink Control Information (DCI). In this way, control of implementation complexity of the terminal device and improvement of DL channel measurement accuracy can be well adapted based on actual needs.

In some embodiments, to divide the plurality of terminal devices into a plurality of groups, the network device 120 may first determine respective base terminal devices for the plurality of groups based on channel characteristics associated with the plurality of terminal devices. For example, network device 120 may determine terminal devices 110-1, 110-4, 110-5, and 110-8 as the base terminal devices of the four groups, respectively. In general, the allocation of the remaining terminal devices may be performed in various ways. For example, the network device 120 may assign terminal devices other than the base terminal device among the plurality of terminal devices to one of the plurality of groups based on a similarity between channel characteristics associated with the terminal devices and channel characteristics associated with each of the base terminal devices. For example, network device 120 may assign each of the remaining terminal devices 110-2, 110-3, 110-6, and 110-7 to one of the plurality of groups based on a similarity between channel characteristics associated with the remaining terminal devices and channel characteristics associated with each of the base terminal devices 110-1, 110-4, 110-5, and 110-8. As another example, the network device 120 may assign the remaining terminal devices of the plurality of terminal devices other than the base terminal device to one of the plurality of groups based on an average similarity between channel characteristics associated with the remaining terminal devices and channel characteristics associated with the terminal devices assigned in each group. In this manner, terminal devices may be grouped based on similarity of channel characteristics, facilitating determination of particular beamforming weights for each group.

In some embodiments, to determine the base terminal device, network device 120 may determine respective channel representations of channel characteristics associated with the plurality of terminal devices for the plurality of terminal devices. The network device 120 may determine a channel similarity between any two terminal devices of the plurality of terminal devices based on the channel representation, and determine a first terminal device and a second terminal device of the plurality of terminal devices having a smallest channel similarity of the channel similarities. The network device 120 may determine the first terminal device and the second terminal device as a base terminal device of a first group and a base terminal device of a second group of the plurality of groups, respectively. For example, network device 120 may determine terminal device 110-1 and terminal device 110-8 as base terminal devices for group A and group D, respectively. In this way, terminal device grouping can be achieved based on channel characteristic similarity.

In some embodiments, it may be desirable to divide the plurality of terminal devices into more than two groups. The network device 120 may have various ways to determine the remaining groups of base terminal devices. For example, the network device 120 may determine a third terminal device and a fourth terminal device having the smallest channel similarity among the channel similarities among the plurality of terminal devices other than the first terminal device and the second terminal device, and then determine the third terminal device and the fourth terminal device as the base terminal device of the third group and the base terminal device of the fourth group among the plurality of groups, respectively. In other words, the network device 120 may determine the remaining groups of base terminal devices in a similar manner as the first and second groups of base terminal devices. In this way, the base terminal device can be easily determined with a low computational complexity.

As another example, the network device 120 may determine respective maximum channel similarities for terminal devices of the plurality of terminal devices other than the first terminal device and the second terminal device based on the channel representation. The maximum channel similarity of the respective terminal device is the larger of the first channel similarity between the respective terminal device and the first terminal device and the second channel similarity between the respective terminal device and the second terminal device. For example, network device 120 may determine that the channel similarity of remaining terminal device 110-2 to the determined base terminal device 110-1 is greater than the channel similarity to the determined base terminal device 110-8, and thus determine the maximum channel similarity of terminal device 110-2 as its channel similarity to the determined terminal device 110-1. Then, the network device 120 may determine a third terminal device having the smallest maximum channel similarity among the maximum channel similarities among the terminal devices other than the first terminal device and the second terminal device, and determine the third terminal device as the base terminal device of the third group among the plurality of groups. In this way, the base terminal device with less similarity in channel characteristics can be well determined.

In some embodiments, to assign the remaining terminal devices to one of the groups, the network device 120 may determine a base terminal device having the greatest channel similarity with the terminal device among the base terminal devices, and assign the terminal device to a group including the determined base terminal device among the groups. For example, network device 120 may determine that the channel characteristics associated with terminal device 110-2 have the greatest similarity to the channel characteristics associated with base terminal device 110-1. Thus, terminal device 110-2 may be assigned to group A. The same allocation operation may be performed for the remaining terminal devices 110-3, 110-6 and 110-7. In this way, grouping of terminal devices can be well achieved.

The network device 120 may have various ways to determine a channel representation of the channel characteristics associated with each of the plurality of terminal devices. For example, the network device 120 may receive uplink reference signals from terminal devices of the plurality of terminal devices and determine uplink channel characteristics associated with the terminal devices based on the received uplink reference signals. Network device 120 may determine a channel representation associated with the terminal device based on the uplink channel characteristics. In this way, UL channel characteristics can be used to group terminal devices based on (partial) channel reciprocity.

As another example, the network device 120 may receive a respective channel state information report from the terminal device and determine a respective channel representation based on the channel state information report. In this way, relatively accurate downlink channel characteristics may be determined, particularly for Frequency Division Duplex (FDD) based systems.

The network device 120 may have various ways to determine beamforming weights associated with transmissions from the network device to the group of terminal devices. For example, network device 120 may receive a plurality of respective uplink reference signals from a plurality of terminal devices and determine a plurality of uplink channel characteristics associated with the plurality of terminal devices based on the received uplink reference signals. Network device 120 may determine a total uplink channel characteristic based on the plurality of uplink channel characteristics associated with the group of terminal devices and determine the beamforming weights based on the total uplink channel characteristic. In this way, the downlink channel characteristics can be easily determined based on the uplink channel characteristics using channel reciprocity.

Network device 120 may have various ways to determine the beamforming weights based on the overall uplink channel characteristics of the group. For example, network device 120 may determine the dominant eigenvector of the total uplink channel characteristic as the beamforming weight. In this way, the optimal beamforming weights for each group may be determined.

As another example, network device 120 may determine the GoB beam weights as beamforming weights based on the total uplink channel characteristics and predefined candidate GoB beams of the antenna array. In this way, the beamforming weights for each group can be easily acquired.

In some embodiments, the uplink channel characteristics associated with a terminal device of the plurality of terminal devices may be a covariance matrix of the terminal device averaged over a polarization and a sub-panel of an antenna array of the network device. In some embodiments, the uplink channel characteristics associated with a terminal device of the plurality of terminal devices may be a covariance matrix of the terminal device averaged over polarizations of an antenna array of the network device. In this way, in a massive MIMO system, uplink channel characteristics associated with a terminal device can be acquired.

For a better understanding of CSI-RS configurations of massive MIMO systems to which some example embodiments of the present disclosure may be applied, reference is now made to fig. 3-5. Fig. 3 illustrates an example of a port arrangement in an antenna array 300 to which some example embodiments of the present disclosure may be applied. Fig. 4 illustrates an example of a CSI-RS resource configuration 400 to which some example embodiments of the present disclosure may be applied. For discussion purposes only, fig. 3 and 4 will be described with reference to fig. 1. Antenna array 300 may be part of network device 120.

As shown in fig. 3, the antenna array 300 is split into four sub-panels 310, 320, 330 and 340. Thus, each CSI-RS resource has 8 ports, each corresponding to one of four sub-panels and one of two polarization directions. Only four beams from the first sub-panel 310 in one polarization direction are shown in fig. 3. As shown in fig. 4, four CSI-RS resources 410, 412, 414, and 416 may be configured for transmission of CSI-RS from network device 120 to terminal devices 110-1 through 110-8. The four CSI-RS resources may each use a different GoB beam to ensure specific sector coverage. For example, four beams from the first sub-panel 310 may be associated with four CSI-RS resources 410, 412, 414, and 416, respectively. Hereinafter, an example implementation of the solution will be described with reference to the antenna array 300 and the CSI-RS resource configuration 400, but it should be noted that this is an example scenario only, and the present disclosure is not limited thereto. For example, the concepts of the present disclosure may be applied to antenna arrays with different port arrangements and any number of CSI-RS resources.

Fig. 5 illustrates an example implementation of a process 500 for communication according to an embodiment of this disclosure. It should be noted that process 500 may be considered as a more specific example of process 200 of fig. 2 applied in a massive MIMO system. For discussion purposes only, fig. 5 will be described with reference to fig. 1 and 3-4.

At block 520, each of the plurality of terminal devices 110-1 through 110-8 may transmit a UL Sounding Reference Signal (SRS) signal to the network device 120 for a corresponding UL channel measurement. Network device 120 may measure UL SRS signals from different active terminal devices within its service coverage and obtain corresponding UL channel characteristics (e.g., channel matrix or channel covariance matrix) for the terminal devices.

At block 540, the network device 120 may construct an appropriate set based on the similarity of measured UL channel characteristics from different terminal devices. In some embodiments, the network device 120 may set up N _gr groups and divide the active terminal devices into N _gr groups according to the measured UL channels. N _gr is equal to or less than the number of configured CSI-RS resources. As shown in fig. 4, the number of configured CSI-RS resources is four. In this embodiment, N _gr may be set to 4. Each group contains one or more terminal devices with similar channel characteristics. Channel similarity may be represented by various metrics, such as channel correlation. Terminal apparatuses having high channel correlation properties are assigned to the same group, and terminal apparatuses having low channel correlation values are divided into different groups. It should be noted that this packet standard is very different from the packet standard used for data (PDSCH/PUSCH) transmissions in which highly relevant terminal devices are typically allocated to different scheduling groups in the same time and frequency resources. In the following description, the terms "channel correlation" and "channel similarity" may be used interchangeably.

To calculate channel correlation between terminal devices for terminal device grouping, the network device first determines an appropriate channel representation for each active terminal device, such as a primary eigenvector derived from the UL channel covariance matrix, or the best GoB beam selected based on UL channel measurements, or even UL CSI reports (e.g., class I CSI or class II CSI) from the UE. For example, in example implementations according to some example embodiments of the present disclosure, the selected GoB beam may be used as a channel representation of a packet for a terminal device. The candidate GoB beams may be generated based on split panel geometry for each polarization or a full panel array configuration without any divisions in polarization as shown in fig. 3. As an example, a split panel geometry as shown in fig. 3 is taken as an example to demonstrate channel similarity calculation according to some example embodiments of the present disclosure.

As shown in fig. 3, the antenna array has N _t＝2N₁N₂ Transceiver (TRX) units, where N ₁ and N ₂ are the number of TRX units polarized in the horizontal and vertical dimensions, respectively. The antenna array is split into N _sp sub-panels, each with N _t/2N_sp TRX units for each polarization, including N _sp,1 horizontal TRX units and N _sp,2 vertical TRX units. Thus, N _t＝2N_spN_sp,1N_sp,2, for the geometry shown in fig. 3, N _sp = 4. The GoB beam may be generated as an oversampled DFT vector based on the split panel geometry in fig. 3. It should be noted that the oversampled DFT vectors are provided as examples for illustration purposes and other vector types are not excluded. For example, the horizontal oversampling DFT vector w _h,i(i＝1、……、O₁N_sp,1) is of size N _sp,1 x1, where O ₁ is the horizontal dimension oversampling rate. Vertical oversampling DFT vector w _v,j(j＝1、……、O₂N_sp,2) is N _sp,2 x 1, where O ₂ is the vertical dimension oversampling rate. Then, goB beam w _k is generated using the Kronecker product of the horizontal and vertical vectors, such asThe size of the material is N _sp,1N_sp,2 multiplied by 1. The optimal GoB beam weights w _o,u for terminal device u may be determined from the UL channel variation for terminal device u according to predefined GoB beams w _k, as shown in equation (1) below:

Wherein the method comprises the steps of All N _sp split panels and the GoB beams of both polarizations are weighted the same, R _u is the covariance matrix of terminal device u (e.g., the covariance matrix averaged over both polarizations, or the full covariance matrix). When R _u is the variance matrix averaged over two polarizations, its dimension isW _k has dimensions ofWhen R _u is a full covariance matrix, its dimension N _t×N_t,W_k is N _t×2N_sp. It should be noted that the uplink channel characteristics R _u of the terminal device u may be represented in other ways than by a covariance matrix.

Network device 120 may perform grouping of terminal devices by calculating and comparing channel similarities of optimal GoB beam weights for all terminal devices. The network device 120 may first select a single terminal device (also referred to as a base terminal device) for each group such that each group contains at least the base terminal device. The network device 120 may then assign the remaining terminal devices to different groups.

The grouping process may be described in detail below as an example, but other grouping algorithms are not excluded. First, the network device 120 may select two base terminal devices having the smallest channel similarity between any two terminal devices, and assign the selected two base terminal devices to different groups (e.g., group a and group D). For example, it may be based on argmin _(i,j)abs(w_o,i ^Hw_o,j), two base terminal devices are selected as terminal devices 110-1 and 110-8 of the plurality of terminal devices 110-1 to 110-8, where i and j are index numbers of terminal devices 110-1 to 110-8 to be grouped, and w _0,i is the best golb beam weight of terminal device i determined by network device 120 from UL channel measurements. Network device 120 may then select base terminal devices for the remaining groups B and C in various ways.

In a first alternative embodiment of UE grouping, the network device 120 may select the other two base terminal devices with the smallest channel similarity among the remaining terminal devices other than the previously selected base terminal devices 110-1 and 110-8 based on argmin _(i,j)abs(w_o,i ^Hw_o,j), where i and j are index numbers of the remaining terminal devices 110-2 to 110-7. The network device 120 may assign two newly selected base terminal devices to the remaining groups B and C.

In a second alternative embodiment of UE grouping, the network device 120 may be based on rgmin _i(max_jabs(w_o,i ^Hw_o,j)) selects a corresponding base terminal device for the remaining group, where i is the index number of any remaining terminal device and j is the index number of any previously selected base terminal device. When the base terminal apparatuses for group B are selected after the base terminal apparatuses for group a and group D are determined, j may be selected from the base terminal apparatuses 110-1 and 110-8, and the base terminal apparatus for group B may be selected as, for example, terminal apparatus 110-4. When the base terminal apparatuses for group C are selected after the base terminal apparatuses for group a, group B, and group D are determined, j may be selected from the base terminal apparatuses 110-1, 110-4, and 110-8, and the base terminal apparatus for group C may be selected as, for example, terminal apparatus 110-6.

The network device 120 may then search for the best group index for each of the remaining terminal devices based on its channel similarity to the selected four base terminal devices. For example, network device 120 may assign each of the remaining terminal devices into four groups based on argmax _jabs(w_o,i ^Hw_o,j), where i is the index number of any of the remaining terminal devices 110-2, 110-3, 110-5, and 110-7, and j is the index number of any of the selected base terminal devices 110-1, 110-4, 110-6, and 110-8. Each group may contain one or more terminal devices.

At block 560, for each group, network device 120 may create CSI-RS resources precoded by group-specific beamforming weights calculated based on UL channel measurements from terminal devices within the group. The network device 120 may have various ways to determine the beamforming weights for each group. For example, the beamforming weights may be eigenvectors derived from the UL channel covariance matrix, or the selected GoB beams based on UL channel measurements, or any other beamforming pattern.

In some embodiments, for each group, the network device 120 may determine an average channel covariance matrix on all sub-panels, polarizations, and terminal devices selected in the group, and then calculate a principal eigenvector of the average covariance matrix as a beamforming weight. The network device 120 may apply beamforming weights to all sub-panels and polarizations in transmissions from the network device to the terminal devices in the group.

In some embodiments, candidate GoB beams w _k(k＝1、……、O₁O₂N_sp,1N_sp,2) are predefined based on the split panel geometry shown in fig. 3. For each group g, network device 120 may determine the best GoB beam weight w _o,g from the predefined GoB beams w _k based on UL channel variations for all terminal devices within the group, as shown in equation (2) below:

Wherein the method comprises the steps of All N _sp split panels and the two polarized GoB beams are weighted the same,R _g,k is the covariance matrix of terminal device k within group g (e.g., the covariance matrix averaged over both polarizations, or the full covariance matrix). As another example, R _g＝∑_kR_g,k. When R _g is the covariance matrix averaged over two polarizations, its dimension isW _k has dimensions ofWhen R _g is a full covariance matrix, its dimension N _t×N_t,w_k is N _t×2N_sp. It should be noted that the uplink channel characteristics R _g,k of terminal device k may be represented in other ways than by a covariance matrix.

For each group g, its associated CSI-RS resources utilize a common GoB beam w _o,g in different sub-panels and different polarizations. Each group has 2N _sp CSI-RS ports weighted by common GoB beam weights w _o,g. The GoB beam weights can be dynamically or semi-statically determined based on channel variations of the terminal devices within the group. Each CSI-RS resource may employ a corresponding GoB beam weight. For example, CSI-RS resource 410 may employ corresponding GoB beam weights that are well adapted to channel variations of terminal devices within group a. CSI-RS resource 412 may employ corresponding GoB beam weights that are well adapted to channel variations of terminal devices within group B. CSI-RS resource 414 may employ corresponding GoB beam weights that are well adapted to channel variations of terminal devices within group C. CSI-RS resource 416 may employ corresponding GoB beam weights that are well adapted to channel variations of terminal devices within group D.

At block 580, the network device 120 may indicate the CSI-RS resource configuration message to the terminal devices in the group through RRC, MAC-CE, or DCI signaling, and transmit the CSI-RS precoded based on the corresponding beam weights to the terminal devices for DL channel measurements.

In a first alternative embodiment of the resource configuration, CSI-RS resources of the group to which the terminal device belongs may be indicated to the terminal device via DCI signaling. In some scenarios, the packets may be updated frequently. The terminal devices in each group may change over time and thus the beamforming weights for each group may be determined dynamically. The terminal device may change from the first group to the second group. Based on DCI signaling, the terminal device may only need to measure a single CSI-RS resource corresponding to the newly allocated group and report RI/PMI/CQI feedback of the indicated CSI-RS resource. In this way, spectral efficiency and beamforming gain may be improved.

In a second alternative embodiment of the resource configuration, CSI-RS resources of the group to which the terminal device belongs may be indicated to the terminal device via RRC or MAC-CE signaling. In some scenarios, the packets may be static or semi-static. The frequency of the terminal devices in each group over time may be lower. For example, the terminal device may be assigned to the first group and not change for a long period of time. In some scenarios, the beamforming weights for each group may be determined dynamically. The terminal device may only need to measure a single CSI-RS resource corresponding to the allocated group and report RI/PMI/CQI feedback of the indicated CSI-RS resource. In this way, spectral efficiency may be improved with low signaling overhead.

In a third alternative embodiment of resource configuration, all CSI-RS resources (e.g., four CSI-RS resources 410, 412, 414, and 416 in fig. 4) may be configured for transmission of CSI-RS from network device 120 to each of terminal devices 110-1 through 110-8 via RRC signaling. Terminal devices 110-1 to 110-8 may measure all CSI-RS resources, select the best CSI-RS resource with, for example, the maximum received power, and report their CSI-RS resource indicator (CRI). Meanwhile, the UE also reports RI/PMI/CQI feedback of the selected CSI-RS resource. In this way, spectral efficiency and beamforming gain may be improved with low signaling overhead.

Fig. 6A and 6B illustrate spectral efficiency comparisons of embodiments of the present disclosure and related schemes. Specifically, fig. 6A illustrates a cell spectrum efficiency comparison of different CSI-RS schemes, and fig. 6B illustrates an edge UE spectrum efficiency comparison of different CSI-RS schemes. To evaluate the performance of UE group-specific CSI-RS schemes, full buffer system level evaluation is performed in NR city mini (UMi) scenario with FDD deployment. Results for 64 TRX units are provided, where (N ₁,N₂) = (8, 4) are in the horizontal and vertical dimensions, respectively. As shown in fig. 3, the antenna array is split into N _sp = 4 sub-panels with a2 x 2 deployment. The relevant simulation parameters are listed in table 1.

TABLE 1 assumption of System level simulation

A cell specific CSI-RS scheme is used as a performance reference. The cell-specific CSI-RS is configured with 4 CSI-RS resources common to all UEs within the cell. The GoB beams in the cell specific CSI-RS scheme are generated based on the split panel geometry in fig. 3. For example, in the vertical dimension, a DFT vector v _v is generated from the downtilt angle, which has dimensions N ₂/2X 1. In the horizontal dimension, N ₁/2 orthogonal DFT vectors w _h,i(i＝1、……、N₁/2 are generated, which are N ₁/2X 1 in size. Generating a GoB beam v _i using the Kronecker product of horizontal and vertical vectors, such asThe size of the material is N ₁N₂/4 multiplied by 1. The CSI-RS resource utilizes a common GoB beam v _i in different sub-panels and different polarizations, and it has 8 CSI-RS ports weighted by the common GoB beam.

The UE-specific CSI-RS may be considered an upper bound on system performance for different CSI-RS designs of embodiments of the present disclosure. The UE-specific CSI-RS uses an oversampled GoB beam pattern that is implemented in a similar manner in embodiments of the present disclosure, with only one terminal device in each group.

For UE group-specific CSI-RS, two alternatives of the UE grouping algorithm in block 540 are compared, wherein frequent CSI-RS resource reconfiguration by DCI is assumed (first alternative embodiment of resource configuration in block 580). The UE-group specific CSI-RS uses the oversampled GoB beam patterns described in embodiments of the present disclosure. The UE group-specific CSI-RS has the same number of CSI-RS resources as the cell-specific CSI-RS scheme with N _gr =4. Based on the measurement of the beamformed CSI-RS resources, using a 2 x2 mode configured to report type I PMI. Simulation results are shown in table 2 and fig. 6A and 6B.

TABLE 2 System level simulation results for different CSI-RS schemes

As shown in table 2 and fig. 6A and 6B, the UE group-specific CSI-RS scheme using dynamically split panel beams has a performance gain of up to 21% -28% without additional CSI-RS overhead, is superior to the baseline cell-specific scheme, and can be considered as an enhancement to the cell-specific scheme. Group-specific dynamic beamforming is supported with low CSI-RS resource overhead by UE group-specific CSI-RS schemes.

Fig. 7 illustrates a flowchart of an example method 700 implemented at a network device according to some embodiments of the present disclosure. For discussion purposes, the method 700 will be described with reference to fig. 1 from the perspective of the network device 120. With the method 700, beamforming gain for transmission of downlink reference signals may be increased with a controlled resource overhead.

At block 720, the network device 120 divides the plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices. At block 740, the network device 120 determines beamforming weights associated with transmission of downlink reference signals from the network device to the group of terminal devices for the group of terminal devices in the plurality of groups. At block 760, the network device 120 transmits downlink reference signals precoded by beamforming weights to terminal devices in a group of terminal devices.

In some embodiments, network device 120 may determine respective base terminal devices for the plurality of groups based on channel characteristics associated with the plurality of terminal devices. The network device 120 may assign terminal devices other than the base terminal device among the plurality of terminal devices to one of the plurality of groups based on a similarity between channel characteristics associated with the terminal devices and channel characteristics associated with each of the base terminal devices.

In some embodiments, network device 120 may determine respective channel representations of channel characteristics associated with a plurality of terminal devices for the plurality of terminal devices. The network device 120 may determine a channel similarity between any two of the plurality of terminal devices based on the channel representation. The network device 120 may determine a first terminal device and a second terminal device having the smallest channel similarity among the channel similarities among the plurality of terminal devices. The network device 120 may determine the first terminal device and the second terminal device as a base terminal device of a first group and a base terminal device of a second group of the plurality of groups, respectively.

In some embodiments, the network device 120 may determine the third terminal device and the fourth terminal device having the smallest channel similarity among the channel similarities among the plurality of terminal devices other than the first terminal device and the second terminal device. The network device 120 may determine the third terminal device and the fourth terminal device as a base terminal device of the third group and a base terminal device of the fourth group, respectively, of the plurality of groups.

In some embodiments, the network device 120 may determine respective maximum channel similarities for terminal devices of the plurality of terminal devices other than the first terminal device and the second terminal device based on the channel representation. Each of the maximum channel similarities may be a greater one of a first channel similarity between the respective terminal device and the first terminal device and a second channel similarity between the respective terminal device and the second terminal device. The network device 120 may determine a third terminal device having the smallest maximum channel similarity among the maximum channel similarities among the terminal devices other than the first terminal device and the second terminal device. The network device 120 may determine the third terminal device as a base terminal device of a third group of the plurality of groups.

In some embodiments, the network device 120 may determine a base terminal device having the greatest channel similarity with the terminal device among the base terminal devices. The network device 120 may assign the terminal device to a group including the determined base terminal device among the plurality of groups.

In some embodiments, the network device 120 may receive an uplink reference signal from a terminal device of the plurality of terminal devices. The network device 120 may determine uplink channel characteristics associated with the terminal device based on the received uplink reference signal. Network device 120 may determine a channel representation associated with the terminal device based on the uplink channel characteristics.

In some embodiments, network device 120 may receive a plurality of respective channel state information reports from a plurality of terminal devices. Network device 120 may determine the channel representation based on a plurality of channel state information reports.

In some embodiments, network device 120 may receive a plurality of respective uplink reference signals from a plurality of terminal devices and determine a plurality of uplink channel characteristics associated with the plurality of terminal devices based on the plurality of uplink reference signals.

In some embodiments, network device 120 may determine the total uplink channel characteristics based on a plurality of uplink channel characteristics associated with the group of terminal devices. Network device 120 may determine beamforming weights based on the total uplink channel characteristics.

In some embodiments, network device 120 may determine the primary eigenvector of the total uplink channel characteristic as a beamforming weight.

In some embodiments, network device 120 may determine the GoB beam weights as beam forming weights based on the total uplink channel characteristics and predefined candidate GoB beams of the antenna array.

In some embodiments, the uplink channel characteristics associated with a terminal device of the plurality of terminal devices may be a covariance matrix of the terminal device averaged over a polarization and a sub-panel of an antenna array of the network device.

In some embodiments, the uplink channel characteristics associated with a terminal device of the plurality of terminal devices may be a covariance matrix of the terminal device averaged over polarizations of an antenna array of the network device.

In some embodiments, the network device 120 may send configuration information to the terminal devices in the group of terminal devices, the configuration information indicating a group-specific resource configuration for the downlink reference signal.

In some embodiments, the network device 120 may transmit downlink reference signals precoded by the beamforming weights based on the group-specific resource configuration.

In some embodiments, the network device 120 may transmit the configuration information via at least one of Radio Resource Control (RRC) signaling, a Medium Access Control (MAC) Control Element (CE), or Downlink Control Information (DCI).

In some embodiments, the network device 120 may send configuration information to the terminal devices in the group of terminal devices, the configuration information indicating at least the group-specific resource configuration and the further group-specific resource configuration.

In some embodiments, network device 120 may transmit downlink reference signals precoded by beamforming weights based on a group-specific resource configuration and transmit downlink reference signals precoded by additional beamforming weights based on additional group-specific resource configurations. Additional beamforming weights may be associated with transmission of the downlink reference signal from the network device to additional groups of terminal devices in the plurality of groups. The further group of terminal devices may be different from the group of terminal devices.

In some embodiments, the network device 120 may send the configuration information via RRC signaling.

Fig. 8 illustrates a flowchart of an example method 800 implemented at a terminal device according to some embodiments of the present disclosure. For discussion purposes, the method 800 will be described with reference to FIG. 1 from the perspective of the terminal device 110-1. With the method 800, DL channel measurement accuracy can be improved with controlled resource overhead.

At block 820, terminal device 110-1 receives configuration information from network device 120 indicating a group-specific resource configuration for a downlink reference signal to be transmitted from the network device to a group of terminal devices including the terminal device. At block 840, terminal device 110-1 receives downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices from the network device based on the group-specific resource configuration.

In some embodiments, the terminal device 110-1 may receive the configuration information via at least one of Radio Resource Control (RRC) signaling, a Medium Access Control (MAC) Control Element (CE), or Downlink Control Information (DCI).

In some embodiments, terminal device 110-1 may receive configuration information indicating at least a group-specific resource configuration and a further group-specific resource configuration different from the group-specific resource configuration.

In some embodiments, terminal device 110-1 may receive downlink reference signals precoded by additional beamforming weights associated with transmission of the downlink reference signals to additional groups of terminal devices different from the group of terminal devices from the network device based on the additional group-specific resource configuration.

In some embodiments, the terminal device 110-1 may receive the configuration information via RRC signaling.

In some embodiments, an apparatus (e.g., network device 120) capable of performing any of the methods 700 may include means for performing the respective steps of the methods 700. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some embodiments, the apparatus includes means for dividing the plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices, means for determining beamforming weights associated with transmission of downlink reference signals from the network device to the group of terminal devices for the group of terminal devices in the plurality of groups, and means for transmitting the downlink reference signals precoded by the beamforming weights to the terminal devices in the group of terminal devices.

In some embodiments, the means for dividing the plurality of terminal devices into a plurality of groups may include means for determining respective base terminal devices for the plurality of groups based on channel characteristics associated with the plurality of terminal devices, and means for assigning terminal devices of the plurality of terminal devices other than the base terminal device to one of the plurality of groups based on a similarity between the channel characteristics associated with the terminal device and the channel characteristics associated with each of the base terminal devices.

In some embodiments, the means for determining the base terminal device may include means for determining respective channel representations of channel characteristics associated with the plurality of terminal devices for the plurality of terminal devices, means for determining a channel similarity between any two of the plurality of terminal devices based on the channel representations, means for determining a first terminal device and a second terminal device of the plurality of terminal devices having a minimum channel similarity of the channel similarities, and means for determining the first terminal device and the second terminal device as a base terminal device of a first group and a base terminal device of a second group of the plurality of groups, respectively.

In some embodiments, the means for determining the base terminal device may further comprise means for determining a third terminal device and a fourth terminal device having a smallest channel similarity among the channel similarities among the plurality of terminal devices other than the first terminal device and the second terminal device, and means for determining the third terminal device and the fourth terminal device as a base terminal device of a third group and a base terminal device of a fourth group among the plurality of groups, respectively.

In some embodiments, the means for determining the base terminal device may further comprise means for determining respective maximum channel similarities for terminal devices of the plurality of terminal devices other than the first terminal device and the second terminal device based on the channel representation, each of the maximum channel similarities being a greater one of a first channel similarity between the respective terminal device and the first terminal device and a second channel similarity between the respective terminal device and the second terminal device, means for determining a third terminal device of the plurality of terminal devices other than the first terminal device and the second terminal device having a smallest maximum channel similarity of the maximum channel similarities, and means for determining the third terminal device as the base terminal device of the third group of the plurality of groups.

In some embodiments, the means for assigning the terminal device to one of the plurality of groups may comprise means for determining, among the base terminal devices, the base terminal device having the greatest channel similarity with the terminal device, and means for assigning the terminal device to the group of the plurality of groups comprising the determined base terminal device.

In some embodiments, the means for determining the channel representation may include means for receiving an uplink reference signal from a terminal device of the plurality of terminal devices, means for determining uplink channel characteristics associated with the terminal device based on the received uplink reference signal, and means for determining the channel representation associated with the terminal device based on the uplink channel characteristics.

In some embodiments, the means for determining a channel representation may include means for receiving a plurality of respective channel state information reports from a plurality of terminal devices, and means for determining a channel representation based on the plurality of channel state information reports.

In some embodiments, the apparatus may further include means for receiving a plurality of respective uplink reference signals from a plurality of terminal devices, and means for determining a plurality of uplink channel characteristics associated with the plurality of terminal devices based on the plurality of uplink reference signals.

In some embodiments, the means for determining the beamforming weights may include means for determining a total uplink channel characteristic based on a plurality of uplink channel characteristics associated with the group of terminal devices, and means for determining the beamforming weights based on the total uplink channel characteristic.

In some embodiments, the means for determining the beamforming weights based on the total uplink channel characteristics may include means for determining a dominant eigenvector of the total uplink channel characteristics as the beamforming weights.

In some embodiments, the means for determining the beamforming weights based on the total uplink channel characteristics may include means for determining the GoB beamforming weights as the beamforming weights based on the total uplink channel characteristics and predefined candidate GoB beams of the antenna array.

In some embodiments, the apparatus may further comprise means for transmitting configuration information to terminal devices in the group of terminal devices, the configuration information indicating a group-specific resource configuration for the downlink reference signal.

In some embodiments, the means for transmitting the downlink reference signal may include means for transmitting the downlink reference signal precoded by the beamforming weights based on the group-specific resource configuration.

In some embodiments, the means for transmitting the configuration information may include means for transmitting the configuration information via at least one of Radio Resource Control (RRC) signaling, a Medium Access Control (MAC) Control Element (CE), or Downlink Control Information (DCI).

In some embodiments, the means for transmitting configuration information may comprise means for transmitting configuration information to terminal devices in a group of terminal devices, the configuration information indicating at least a group specific resource configuration and a further group specific resource configuration.

In some embodiments, the means for transmitting downlink reference signals may include means for transmitting downlink reference signals precoded by beamforming weights based on a group-specific resource configuration, and means for transmitting downlink reference signals precoded by further beamforming weights based on a further group-specific resource configuration. Additional beamforming weights may be associated with transmission of the downlink reference signal from the network device to additional groups of terminal devices in the plurality of groups. The further group of terminal devices may be different from the group of terminal devices.

In some embodiments, the means for transmitting the configuration information may include means for transmitting the configuration information via RRC signaling.

In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 700. In some embodiments, the component includes at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the above-described operation of the apparatus.

In some embodiments, an apparatus (e.g., terminal device 110-1) capable of performing any one of the methods 800 may include means for performing the respective steps of the method 800. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some embodiments, the apparatus includes means for receiving, at a terminal device, configuration information from a network device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices including the terminal device, and means for receiving, from the network device, downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices based on the group-specific resource configuration.

In some embodiments, the means for receiving configuration information may include means for receiving configuration information via at least one of Radio Resource Control (RRC) signaling, a Medium Access Control (MAC) Control Element (CE), or Downlink Control Information (DCI).

In some embodiments, the means for receiving configuration information may include means for receiving configuration information indicating at least a group-specific resource configuration and a further group-specific resource configuration different from the group-specific resource configuration.

In some embodiments, the apparatus may further include means for receiving, from the network device, a downlink reference signal precoded by a further beamforming weight associated with transmission of the downlink reference signal to a further group of terminal devices different from the group of terminal devices based on the further group-specific resource configuration.

In some embodiments, the means for receiving configuration information may include means for receiving configuration information via RRC signaling.

In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 800. In some embodiments, the component includes at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the above-described operation of the apparatus.

Fig. 9 is a simplified block diagram of a device 900 suitable for implementing embodiments of the present disclosure. Device 900 may be provided to implement a communication device such as terminal device 110-1 or network device 120 shown in fig. 1. As shown, device 900 includes one or more processors 910, one or more memories 920 coupled to processors 910, and one or more transmitters and/or receivers (TX/RX) 940 coupled to processors 910.

TX/RX 940 is used for two-way communication. TX/RX 940 has at least one antenna to facilitate communications. The communication interface may represent any interface required for communication with other network elements.

The processor 910 may be of any type suitable to a local technical network and may include, by way of non-limiting example, one or more of general purpose computers, special purpose computers, microprocessors, digital Signal Processors (DSPs), and processors based on a multi-core processor architecture. The device 900 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock that is synchronized to the master processor.

Memory 920 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, read-only memory (ROM) 924, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact Disks (CD), digital Video Disks (DVD), and other magnetic and/or optical storage devices. Examples of volatile memory include, but are not limited to, random Access Memory (RAM) 922 and other volatile memory that does not persist during power outages.

The computer program 930 includes computer-executable instructions that are executed by the associated processor 910. Program 930 may be stored in ROM 1020. Processor 910 may perform any suitable actions and processes by loading program 930 into RAM 1020.

Embodiments of the present disclosure may be implemented by the program 930 such that the device 900 may perform any of the processes of the present disclosure discussed with reference to fig. 2-8. Embodiments of the present disclosure may also be implemented in hardware or by a combination of software and hardware.

In some embodiments, the program 930 may be tangibly embodied in a computer-readable medium that may be included in the device 900 (such as in the memory 920) or other storage device that the device 900 may access. Device 900 may load program 930 from a computer-readable medium into RAM 922 for execution. The computer readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig. 10 shows an example of a computer readable medium 1000 in the form of a CD or DVD. The computer-readable medium has stored thereon the program 930.

In general, the various embodiments of the disclosure may be implemented using hardware or special purpose circuits, software, logic or any combination thereof. Some 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 various aspects of the embodiments of the disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these 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 comprises computer executable instructions, such as instructions included in program modules, that are executed in a device on a target real or virtual processor to perform the method 900 described above with reference to fig. 2-8. 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 local or distributed devices. In a distributed device, program modules may be located in both local and remote memory storage media.

Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program code 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 code, when executed by the processor or controller, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this disclosure, computer program code or related data may be carried by any suitable carrier to enable an apparatus, device, or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer 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 specific examples of a computer-readable storage medium would 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. The term "non-transitory" as used herein is a limitation on the medium itself (i.e., tangible, rather than signals), and not on the durability of data storage (e.g., RAM and ROM).

Further, while operations are described in a particular order, this should not be construed 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 advantageous. Also, while several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions 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

1. A network device, comprising:

at least one processor, and

At least one memory storing instructions that, when executed by the at least one processor, cause the network device to at least:

dividing a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices;

Determining beamforming weights associated with transmission of downlink reference signals from the network device to a group of terminal devices of the plurality of groups, and

And transmitting the downlink reference signals precoded by the beamforming weights to terminal devices in the terminal device group.

2. The network device of claim 1, wherein the network device is caused to divide the plurality of terminal devices into the plurality of groups by:

Determining respective base terminal devices for the plurality of groups based on the channel characteristics associated with the plurality of terminal devices, and

Terminal devices other than the base terminal device of the plurality of terminal devices are assigned to one of the plurality of groups based on a similarity between the channel characteristics associated with the terminal device and the channel characteristics associated with each of the base terminal devices.

3. A network device according to claim 2, wherein the network device is caused to determine the base terminal device by:

Determining respective channel representations of the channel characteristics associated with the plurality of terminal devices for the plurality of terminal devices;

Determining a channel similarity between any two of the plurality of terminal devices based on the channel representation;

determining a first terminal device and a second terminal device having the smallest channel similarity among the channel similarities among the plurality of terminal devices, and

And determining the first terminal device and the second terminal device as a base terminal device of a first group and a base terminal device of a second group in the plurality of groups, respectively.

4. A network device according to claim 3, wherein the network device is further caused to determine the base terminal device by:

determining a third terminal device and a fourth terminal device having the smallest channel similarity among the channel similarities among the plurality of terminal devices except the first terminal device and the second terminal device, and

And determining the third terminal device and the fourth terminal device as a base terminal device of a third group and a base terminal device of a fourth group in the plurality of groups respectively.

5. A network device according to claim 3, wherein the network device is further caused to determine the base terminal device by:

Determining respective maximum channel similarities for terminal devices of the plurality of terminal devices other than the first terminal device and the second terminal device based on the channel representation, each of the maximum channel similarities being a greater one of a first channel similarity between the respective terminal device and the first terminal device and a second channel similarity between the respective terminal device and the second terminal device;

Determining a third terminal device having the smallest maximum channel similarity among the maximum channel similarities among the terminal devices other than the first terminal device and the second terminal device, and

And determining the third terminal device as a base terminal device of a third group of the plurality of groups.

6. A network device according to claim 2, wherein the network device is caused to assign the terminal device into one of the plurality of groups by:

determining a basic terminal device with the maximum channel similarity with the terminal device in the basic terminal devices, and

The terminal device is assigned to a group of the plurality of groups comprising the determined base terminal device.

7. A network device according to claim 3, wherein the network device is caused to determine the channel representation by:

Receiving an uplink reference signal from a terminal device of the plurality of terminal devices;

determining uplink channel characteristics associated with the terminal device based on the received uplink reference signal, and

The channel representation associated with the terminal device is determined based on the uplink channel characteristics.

8. A network device according to claim 3, wherein the network device is caused to determine the channel representation by:

Receiving a plurality of corresponding channel state information reports from the plurality of terminal devices, and

The channel representation is determined based on the plurality of channel state information reports.

9. The network device of claim 1, wherein the network device is further caused to:

receiving a plurality of corresponding uplink reference signals from the plurality of terminal devices, and

A plurality of uplink channel characteristics associated with the plurality of terminal devices are determined based on the plurality of uplink reference signals.

10. The network device of claim 9, wherein the network device is caused to determine the beamforming weights by:

determining a total uplink channel characteristic based on the plurality of uplink channel characteristics associated with the group of terminal devices, and

The beamforming weights are determined based on the total uplink channel characteristics.

11. The network device of claim 10, wherein the network device is caused to determine the beamforming weights based on the total uplink channel characteristics by:

A principal eigenvector of the total uplink channel characteristic is determined as the beamforming weight.

12. The network device of claim 10, wherein the network device is caused to determine the beamforming weights based on the total uplink channel characteristics by:

The GoB beam weights are determined to be the beamforming weights based on the total uplink channel characteristics and predefined candidate GoB beams of the antenna array.

13. The network device of any of claims 7 and 9-11, wherein the uplink channel characteristics associated with a terminal device of the plurality of terminal devices are covariance matrices of the terminal device averaged over sub-panels and polarizations of an antenna array of the network device.

14. The network device of any of claims 7 and 9-12, wherein the uplink channel characteristics associated with a terminal device of the plurality of terminal devices is a covariance matrix of the terminal device averaged over polarizations of an antenna array of the network device.

15. The network device of any of claims 1 to 14, wherein the network device is further caused to:

Transmitting configuration information to the terminal devices in the terminal device group, the configuration information indicating a group-specific resource configuration for the downlink reference signal.

16. The network device of claim 15, wherein the network device is caused to transmit the downlink reference signal by:

the downlink reference signals precoded by the beamforming weights are sent based on the set of specific resource configurations.

17. The network device of claim 15 or 16, wherein the network device is caused to transmit the configuration information via at least one of:

Radio Resource Control (RRC) signaling,

Media Access Control (MAC) Control Element (CE), or

Downlink Control Information (DCI).

18. The network device of claim 15, wherein the network device is caused to transmit the configuration information by:

And transmitting the configuration information to the terminal equipment in the terminal equipment group, wherein the configuration information at least indicates the group-specific resource configuration and the additional group-specific resource configuration.

19. The network device of claim 18, wherein the network device is caused to transmit the downlink reference signal by:

transmitting the downlink reference signals precoded by the beamforming weights based on the set of specific resource configurations, and

The downlink reference signals precoded by further beamforming weights associated with transmission of downlink reference signals from the network device to a further group of terminal devices of the plurality of groups, the further group of terminal devices being different from the group of terminal devices, are transmitted based on the further group-specific resource configuration.

20. The network device of claim 18 or 19, wherein the network device is caused to send the configuration information via RRC signaling.

21. A terminal device, comprising:

at least one processor, and

At least one memory storing instructions that, when executed by the at least one processor, cause the terminal device to at least:

Receiving configuration information from a network device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices including the terminal device, and

The downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices are received from the network device based on the group-specific resource configuration.

22. A terminal device according to claim 21, wherein the terminal device is caused to receive the configuration information via at least one of:

Radio Resource Control (RRC) signaling,

Media Access Control (MAC) Control Element (CE), or

Downlink Control Information (DCI).

23. A terminal device according to claim 21, wherein the terminal device is caused to receive the configuration information by:

the configuration information is received, the configuration information indicating at least the group-specific resource configuration and a further group-specific resource configuration different from the group-specific resource configuration.

24. A terminal device according to claim 23, wherein the terminal device is further caused to:

The downlink reference signals precoded by further beamforming weights associated with transmission of the downlink reference signals to a further group of terminal devices different from the group of terminal devices are received from the network device based on the further group-specific resource configuration.

25. A terminal device according to claim 23 or 24, wherein the terminal device is caused to receive the configuration information via RRC signalling.

26. A method, comprising:

Dividing, at a network device, a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices;

27. A method, comprising:

Receiving, at a terminal device, configuration information from a network device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices including the terminal device, and

28. An apparatus, comprising:

means for dividing, at a network device, a plurality of terminal devices into a plurality of groups based at least on channel characteristics associated with the plurality of terminal devices;

Means for determining beamforming weights associated with transmission of downlink reference signals from the network device to a group of terminal devices of the plurality of groups, and

Means for transmitting the downlink reference signal precoded by the beamforming weights to a terminal device in the group of terminal devices.

29. An apparatus, comprising:

means for receiving configuration information from a network device at a terminal device, the configuration information indicating a group-specific resource configuration for downlink reference signals to be transmitted from the network device to a group of terminal devices comprising the terminal device, and

Means for receiving the downlink reference signals precoded by beamforming weights associated with transmission of the downlink reference signals to the group of terminal devices from the network device based on the group-specific resource configuration.

30. A computer readable medium comprising program instructions which, when executed by an apparatus, cause the apparatus to perform at least the method of claim 26 or 27.