CN111886913B

CN111886913B - Communication method and communication device

Info

Publication number: CN111886913B
Application number: CN201880091445.1A
Authority: CN
Inventors: 宋暖
Original assignee: Nokia Shanghai Bell Co Ltd
Current assignee: Nokia Shanghai Bell Co Ltd
Priority date: 2018-04-19
Filing date: 2018-04-19
Publication date: 2023-07-21
Anticipated expiration: 2038-04-19
Also published as: CN111886913A; WO2019200595A1

Abstract

Embodiments of the present disclosure relate to a communication method and a communication apparatus. There is provided a communication method implemented at a terminal device, comprising: determining a candidate antenna set from a plurality of antennas at the terminal device based on the pre-measured channel quality, the candidate antenna set including antennas available for non-linear precoding by the network device; and transmitting information about the candidate antenna set to the network device using the reference signal resource indicator, such that the network device determines a target antenna set for non-linear precoding from the candidate antenna set.

Description

Communication method and communication device

Technical Field

Embodiments of the present disclosure relate generally to communication technology, and more particularly, to a method for performing nonlinear precoding and a corresponding communication device.

Background

Transmitter-side interference cancellation techniques for co-scheduled terminal devices (e.g., UEs) have been studied to improve communication quality. These interference cancellation techniques include, for example, nonlinear precoding, linear and nonlinear hybrid precoding techniques, and the like. Nonlinear precoding techniques may include Dirty Paper Coding (DPC) based precoding techniques such as Tomlinson Harashima Precoding (THP), QL based DPC, zero forcing THP (ZF-THP), vector perturbation, and the like.

Nonlinear precoding technology has been applied to some extent in wireless communication systems, particularly in next generation New Radio (NR) systems, and further research will be conducted. Non-linear precoding (e.g., THP) can provide significantly enhanced system performance compared to linear precoding, especially for correlated channels where the subspaces of the UEs overlap.

However, existing nonlinear precoding techniques also have some problems. For example, since a UE is typically equipped with multiple antennas, and acquires full downlink Channel State Information (CSI) with high accuracy in order to obtain better performance of nonlinear precoding, a large amount of CSI feedback may cause very large overhead and CSI delay. Furthermore, nonlinear precoding is generally more sensitive to CSI errors than linear precoding based on signal subspace computation, and thus requires more explicit and high resolution CSI, thereby disadvantageously increasing CSI overhead and requiring improved CSI accuracy. These are all the problems to be solved in the prior art.

Disclosure of Invention

In general, embodiments of the present disclosure propose a communication method implemented at a communication device and a corresponding communication device to increase implementation overhead and complexity of nonlinear precoding, thereby further improving performance of a communication system.

In a first aspect, embodiments of the present disclosure provide a communication method implemented at a terminal device. The method comprises the following steps: determining a candidate antenna set from a plurality of antennas at the terminal device based on the pre-measured channel quality, the candidate antenna set including antennas available for non-linear precoding by the network device; and transmitting information about the candidate antenna set to the network device using the reference signal resource indicator, such that the network device determines a target antenna set for non-linear precoding from the candidate antenna set.

In this aspect, embodiments of the present disclosure also provide a terminal device for performing communication, including: a control unit configured to determine a candidate antenna set from a plurality of antennas at the terminal device, the candidate antenna set including antennas available for non-linear precoding by the network device, based on the pre-measured channel quality; and a transmitting unit configured to transmit information about the candidate antenna set to the network device using the reference signal resource indicator, so that the network device determines a target antenna set for non-linear precoding from among the candidate antenna sets.

Embodiments of the present disclosure also include a terminal device for communication. The terminal device includes: a processor and a memory storing instructions that, when executed by the processor, cause the terminal device to perform a method according to the first aspect.

In a second aspect, embodiments of the present disclosure provide a communication method implemented at a network device. The method comprises the following steps: obtaining information about a candidate antenna set from a reference signal resource indicator received from the terminal device, the candidate antenna set being selected by the terminal device from a plurality of antennas at the terminal device based on a pre-measured channel quality, the candidate antenna set comprising antennas available for non-linear precoding by the network device; determining a target antenna set for nonlinear precoding from the candidate antenna sets; and transmitting information about the set of target antennas to the terminal device.

In this regard, embodiments of the present disclosure also provide a network device for communication. The apparatus includes: a control unit configured to: obtaining information about a candidate antenna set from a reference signal resource indicator received from the terminal device, the candidate antenna set being selected by the terminal device from a plurality of antennas at the terminal device based on a pre-measured channel quality, the candidate antenna set including antennas available for non-linear precoding by the network device, and determining a target antenna set for non-linear precoding from the candidate antenna set; and a transmitting unit configured to transmit information on the target antenna set to the terminal device.

Embodiments of the present disclosure also include a network device for communication. The network device includes: a processor and a memory storing instructions that, when executed by the processor, cause the network device to perform a method according to the second aspect.

It should be understood that the description in this summary is not intended to limit key or critical features of the disclosed embodiments, nor is it intended to limit the scope of the disclosure. Other features of the present disclosure will become apparent from the following description.

Drawings

The above and other features, advantages and aspects of embodiments of the present disclosure will become more apparent by reference to the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, wherein like or similar reference numerals denote like or similar elements, in which:

FIG. 1 illustrates an example communication network in which embodiments of the present disclosure may be implemented;

fig. 2 illustrates a flow chart of a method implemented at a terminal device side according to some embodiments of the present disclosure;

fig. 3 illustrates a flow chart of a method implemented at a network device side according to some embodiments of the present disclosure;

fig. 4 illustrates an interaction diagram of a network device and a terminal device according to some embodiments of the present disclosure;

Fig. 5 illustrates an interaction diagram of a network device and a terminal device according to some embodiments of the present disclosure;

fig. 6 illustrates a schematic diagram of frame structure and transmission in accordance with certain embodiments of the present disclosure;

FIGS. 7 and 8 illustrate system performance schematic diagrams, respectively, according to certain embodiments of the present disclosure;

fig. 9 illustrates a block diagram of an apparatus at a terminal device, in accordance with certain embodiments of the present disclosure;

fig. 10 illustrates a block diagram of an apparatus at a network device, according to some embodiments of the present disclosure; and

fig. 11 illustrates a block diagram of a device in accordance with certain embodiments of the present disclosure.

Detailed Description

Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present disclosure have been shown in the accompanying drawings, it is to be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are for illustration purposes only and are not intended to limit the scope of the present disclosure.

According to embodiments of the present disclosure, a "network device" refers to other entities or nodes having a particular function in a base station or communication network. A "base station" (BS) may refer to a node B (NodeB or NB), an evolved node B (eNodeB or eNB), a new radio base station gNB, a Remote Radio Unit (RRU), a Radio Head (RH), a Remote Radio Head (RRH), a repeater, or a low power node such as a pico base station, femto base station, etc. In the context of the present disclosure, for ease of discussion, the terms "network device" and "base station" may be used interchangeably and may be used primarily as an example of a network device.

The term "terminal device" as used herein refers to any terminal device capable of wireless communication with a base station or with each other. As examples, the terminal device may include a User Equipment (UE), a terminal device (MT), a Subscriber Station (SS), a Portable Subscriber Station (PSS), a Mobile Station (MS), or an Access Terminal (AT), as well as the above devices on-board. In the context of the present disclosure, for ease of discussion, the terms "terminal device" and "UE" may be used interchangeably.

The terms "including" or "comprising," and variations thereof, as used herein, are intended to be inclusive and open-ended, i.e., including, but not limited to. The term "based on" is based at least in part on. The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment". Related definitions of other terms will be given in the description below.

As described above, in the nonlinear precoding system, in order to perform reception combining at the UE side, it is necessary to acquire beamformed CSI or all downlink CSI, and the UE must perform a specific demodulation process. However, this makes the UE's reception implementation and CSI acquisition more complex, increasing implementation difficulty.

In addition, the antenna selection process of the gNB requires the gNB to acquire all CSI and determine the selected antennas and/or ports (for ease of discussion, antennas and ports are collectively referred to as "antennas" hereinafter), which increases overhead and increases the difficulty of timing issues. The current indication of the selected antenna is explicit, e.g. the antenna index. If the antenna selection case requires the use of improved CSI, e.g., obtained via aperiodic CSI reporting or aperiodic Sounding Reference Signal (SRS) transmission, these CSI needs to be combined with an indication of the selected antenna index, which greatly increases the occupancy of the control channel, which is undesirable.

To address these and other potential problems, embodiments of the present disclosure provide a communication method. According to the method of the embodiment of the disclosure, the terminal device determines a candidate antenna set from a plurality of antennas at the terminal device based on a pre-measured channel quality, the candidate antenna set including antennas available for non-linear precoding by the network device. The terminal device sends information about the candidate antenna set to the network device by using the reference signal resource indicator in the uplink control information, so that the network device determines a target antenna set for nonlinear precoding from the candidate antenna set. In this way, nonlinear precoding is designed only for CSI from antennas of the target antenna set, thereby simplifying the CSI acquisition process and reducing the number of CSI that need to be acquired. Meanwhile, the information of the candidate antenna set is indicated by the reference signal resource indicator, and no additional field of control information or other control signaling is added, so that the occupancy rate of a control channel is reduced, and the system performance is improved.

Fig. 1 illustrates an example communication network 100 in which embodiments of the present disclosure may be implemented. The communication network 100 includes a network device (e.g., gNB) 110 and terminal devices (e.g., UE) 120-1, … … 120-K (hereinafter collectively referred to as terminal devices 120 or UE 120) in communication therewith.

The communications in the communication network 100 shown in fig. 1 may be implemented in accordance with any suitable communication protocol, 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 protocols now known or later developed. Moreover, the communication may employ 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 multiple access (OFDM), and/or any other technology now known or later developed.

It should be understood that the number of network devices and the number of terminal devices shown in fig. 1 are for illustration purposes only and are not intended to be limiting. Communication network 100 may include any suitable type and number of network devices, each network device may provide a suitable range and a suitable number of coverage, and communication network 100 may also include any suitable type and number of terminal devices.

It should also be appreciated that while fig. 1 illustrates a multi-user, e.g., multiple-input multiple-output (MIMO), system, embodiments of the present disclosure are not so limited, but may be applied to other suitable systems, e.g., single-user multiple-antenna systems.

As shown in fig. 1, assuming THP-based nonlinear precoding at the gNB 110, each UE 120 of the K UEs hasAn antenna. M at gNB 110 _T There are r data streams in total, where +.>gNB 110 will r _k The data stream is sent to the kth UE. In the embodiment of fig. 1, the precoding at the gNB 110 side comprises a linear precoder +.>112 and a nonlinear THP precoder 111 to suppress inter-data stream and inter-user interference.

On the terminal device side, UE 120 can select an antenna for reception. In some embodiments, the selected antennas may be represented as an antenna selection matrixIncluding index vectorsIs a matrix of units of rows. In addition, the method also comprises a weighting process before demodulation and decodingAnd a modulo operation Mod (. Channel->Is obtained from complete CSI, wherein ∈>Is the total number of receive antennas from all UEs.

Traditional nonlinear precoding schemes rely on beamformed CSI or full downlink CSI, where the UE needs to perform different reception procedures for linear combining. Embodiments of the present disclosure propose another mode, namely UE-centric antenna selection, which can effectively solve the problem when the required CSI cannot be obtained.

Embodiments of the present disclosure employ a non-linear precoding scheme for terminal device centric antenna selection, wherein SRS Resource Indicators (SRIs) in an uplink/downlink signaling format are utilized. Unlike using explicit indications (i.e., antenna indexes) regarding antenna selection, embodiments of the present disclosure utilize SRIs of specific DCI formats to effectively inform each other of selected or down/further selected antennas.

Specifically, UE 120 periodically reports to the gNB the N selected antennas that it wishes to use using SRI, which in the context of the present disclosure are also referred to as a candidate antenna set. SRI also implicitly represents the Rank (RI) of the transmission channel and may be considered as an integral part of CSI reporting. In this case, SRS-based antenna switching is always in an enabled state.

At gNB 110, an SRI reference indication format is formed in Downlink Control Information (DCI) to inform UE 120 to receive on r antennas (r.ltoreq.N) of the N antennas that are suitable for data transmission, thereby implementing a reception procedure based on antenna selection.

UE 120 receives downlink data according to the antenna selection implicitly indicated by the SRI from the gNB, in this way, the reception combining design on the UE 120 side can be bypassed.

SRIs have been designed in conventional schemes to assist in beam management, e.g., SRIs may be applied in the downlink from the gNB to the UE to indicate the corresponding beam at the UE side. In the embodiments of the present disclosure, such an SRI capable of beam indication is utilized for antenna selection, thereby providing a simple and efficient non-linear precoding solution.

Embodiments of the present disclosure simplify the CSI acquisition process compared to conventional schemes, because only CSI from selected antennas/ports requires the design of nonlinear precoding. Furthermore, in embodiments of the present disclosure, using SRI to implicitly indicate antenna selection and aperiodic SRS with antenna selection may simplify the procedure and save signaling. Typically antenna selection is indicated by higher layer signaling. If it needs to be enabled and determined by the gNB, the gNB must know the antenna indexes reported by the UE through some signaling, and then request which antenna or antennas the UE applies by indicating these indexes. If it is applied with aperiodic SRS transmission for CSI acquisition, the resources of the aperiodic SRS should also be notified to the UE. The demodulation-related indication and the aperiodic SRS-related indication should be included in the DCI, for example, an antenna index and/or SRS resource for each selected antenna, which increases DCI utilization. Since different antennas/groups are allocated different SRS resources during an antenna switching period, the gNB can simply use the SRI to implicitly indicate to the UE the selected antennas for demodulating the data streams. In the case of aperiodic SRS transmission, a specific DCI format including an SRI and aperiodic SRS trigger is preferable because the SRI includes not only information of a selected antenna but also SRS resources. In the embodiment of the disclosure, the explicit index of the antenna and the indication of the aperiodic SRS resource in the DCI are replaced by SRI, thereby effectively saving signaling overhead. In this way, the impact of CSI errors can be effectively reduced, making the system more robust. Meanwhile, the receiving and combining stage is replaced by antenna selection, so that the complexity of the UE is effectively reduced.

In some embodiments, to update the precoder, aperiodic SRS transmission and antenna selection may also be jointly triggered by utilizing SRI, where m.ltoreq.n may be used for m antennas out of N selected antennas (hereinafter also referred to as "update antenna set"). In this case, the UE need only transmit aperiodic SRS on a selected antenna implicitly indicated by, for example, m SRIs. In this way, the joint triggering of the aperiodic SRS and the SRI can be performed in the DCI format, so that the system performance is effectively improved.

The principles and specific embodiments of the present disclosure will be described in detail below with reference to fig. 2 through 9 from the perspective of a terminal device and a network device, respectively. Referring first to fig. 3, a flow chart of a method 200 implemented at the terminal device side according to some embodiments of the present disclosure is shown. It is to be appreciated that the method 200 can be implemented, for example, at the terminal device 120 as shown in fig. 1.

At 210, the terminal device 120 determines a set of candidate antennas from among a plurality of antennas at the terminal device 120 based on the pre-measured channel quality. The candidate antenna set includes antennas that are available for non-linear precoding by the network device.

In some embodiments, the terminal device 120 may obtain a pre-measured channel quality for each of a plurality of antennas at the terminal device and then select an antenna from the plurality of antennas with a channel quality above a threshold quality as an antenna in the candidate antenna set.

At 220, the terminal device 120 transmits information about the candidate antenna set to the network device using the reference signal resource indicator to cause the network device 110 to determine a target antenna set for non-linear precoding from the candidate antenna set.

In some embodiments, information about the candidate antenna set may be included in a reference signal resource indicator of uplink control information and the uplink control information sent to network device 110.

Additionally or alternatively, in some embodiments, terminal device 120 may receive information about the set of target antennas from network device 110. For example, downlink Control Information (DCI) from network device 110 may be received and information about the set of target antennas may be obtained from a reference signal resource indicator included in the downlink control information.

On the other hand, the network device 110 may measure channel information corresponding to the target antenna set based on a periodic reference signal (e.g., SRS) received from the terminal device 120. The network device 110 may then non-linearly precode data based on the measured channel information and transmit the non-linearly precoded data to the terminal device 120. Thus in some embodiments, terminal device 120 may additionally or alternatively receive non-linearly precoded data from network device 110 using antennas in the target antenna set. The terminal device 120 may then demodulate the received data based on the demodulation reference signal for the nonlinear precoding.

In some cases, CSI for non-linear precoding may not be accurate enough, especially for cell-edge UEs. When enhanced performance is required, the precoder needs to be updated. Thus, network device 110 may need to obtain updated CSI through aperiodic SRS to improve performance of nonlinear precoding. In some embodiments, terminal device 120 transmits a reference signal to network device 110 with antennas in the updated antenna set in response to receiving information from the network device regarding the updated antenna set. In this case, the reference signal transmitted by the terminal device 120 to the network device 110 is a reference signal transmitted due to a trigger, and thus is aperiodic. The network device 110 may then measure channel information corresponding to the updated antenna set based on the received reference signal and non-linearly precode data based on the measured channel information and transmit to the terminal device 120. At the terminal device 120, the non-linearly precoded data may be received from the network device 110.

The updated antenna set may be determined by network device 110 from the candidate antenna set. The terminal device 120 may obtain information for updating the antenna set from a reference signal resource indicator included in the downlink control information received by the network device.

Embodiments according to the present disclosure can simplify the CSI acquisition process because only CSI from selected antennas/ports is needed to design the nonlinear precoding. Furthermore, using SRI to implicitly indicate antenna selection and aperiodic SRS with antenna selection may simplify the nonlinear precoding process and save signaling. Antenna selection schemes according to embodiments of the present disclosure also mitigate the effects of CSI errors and are more robust. In addition, the complexity of the UE is reduced since the receive combining stage is replaced by antenna selection.

Referring next to fig. 3, a flow chart of a method 300 implemented at a terminal device side according to some embodiments of the present disclosure is shown. It is to be appreciated that the method 300 can be implemented, for example, at the network device 110 as shown in fig. 1.

At 310, network device 110 obtains information about the candidate antenna set from the reference signal resource indicator received from terminal device 120.

The candidate antenna set may be selected by the terminal device from a plurality of antennas at the terminal device based on a pre-measured channel quality. The candidate antenna set includes antennas that are available for non-linear precoding by the network device.

In some embodiments, network device 110 may receive uplink control information including a reference signal resource indicator from terminal device 120 and obtain information about the candidate antenna set from the reference signal resource indicator.

At 320, network device 110 determines a set of target antennas from the set of candidate antennas for non-linear precoding. The network device 110 may select an antenna with better channel information from the candidate antenna set according to the measured channel information, and use the antenna as an antenna in the target antenna set. In the alternative, the network device 110 may also determine the target antenna set from the candidate antenna set according to a preset rule or system requirement, or the like.

At 330, the network device 110 sends information about the set of target antennas to the terminal device. In some embodiments, network device 110 may include information about the set of target antennas in a reference signal resource indicator of downlink control information and send the downlink control information to terminal device 120.

In some embodiments, terminal device 120 may periodically send a reference signal, such as an SRS, to network device 110. The network device 110 may measure channel information corresponding to the target antenna set based on the periodic reference signal received from the terminal device, and may perform nonlinear precoding on the data based on the measured channel information. Network device 110 may then transmit the non-linearly precoded data to terminal device 120.

Additionally or alternatively, in some embodiments, the network device 110 may determine an updated antenna set from the candidate antenna set in response to triggering transmission of the aperiodic reference signal. The network device 110 may also transmit information about the updated antenna set to the terminal device 120 such that the terminal device 120 utilizes the antennas in the updated antenna set to transmit non-periodic reference signals to the network device 110.

Information about the updated antenna set may be transmitted in a variety of ways. For example, network device 110 may include information regarding the updated antenna set in a reference signal resource indicator of the downlink control information and transmit the downlink control information to terminal device 120.

Additionally or alternatively, in some embodiments, network device 110 may receive a reference signal, e.g., SRS, transmitted by terminal device 120 with an antenna in the updated antenna set. Since such reference signals are transmitted by the terminal device 120 according to a trigger from the network device 110, they are aperiodic reference signals. The network device 110 may measure channel information corresponding to the updated antenna set based on the aperiodic reference signal received from the terminal device, and may perform nonlinear precoding on the data based on the measured channel information. Network device 110 may then transmit the non-linearly precoded data to terminal device 120.

The interaction of network device 110 and terminal device 120 will be further described in connection with the embodiments of fig. 4 and 5. In the following embodiments, the network device 110 and the terminal device 120 are described taking the gNB and the UE as examples. It should be understood that this is exemplary and is not intended to limit any of the embodiments of the present disclosure.

Fig. 4 illustrates an interaction diagram of a network device and a terminal device according to some embodiments of the present disclosure. In the embodiment of fig. 4, the UE determines a candidate antenna set and sends information about the candidate antenna set to the gNB. The gNB then performs antenna selection based on the candidate antenna set to determine a target antenna set for non-linear precoding. For ease of discussion, this process will be referred to below simply as the "Regular Phase".

In the embodiment of fig. 4, UE 120 continuously transmits 411 reference signals (e.g., SRS) through antenna switching to obtain CSI for all antennas at the UE. The UE selects 412N antennas from all antennas of the UE as a candidate antenna set based on the channel quality measured in advance on each antenna/port. The gNB 110 does not have to use all downlink CSI, thereby avoiding the delay problem that exists between CSI obtained on different antennas in different time slots. Thus, UE 120 periodically reports 413 implicit CSI using the SRI in the uplink control information to indicate to the gNB 110 the N antennas in the candidate antenna set that it wishes to use. For example, the UE may periodically feed back N SRIs in PUCCH to indicate the N antennas to the gNB 110.

Then, at 414, the gNB 110 acquires the CSI, performs scheduling, designs a linear encoder, selects r antennas of the N preferred antennas of the candidate antenna set as a target antenna set, and designs a nonlinear precoding. In designing the linear encoder, the gNB 110 calculates the linear precoder F and constructs an antenna selection matrix T. In designing the nonlinear encoder, the gNB 110 designs the nonlinear precoder based on an effective channel for the feedback filter B and the feedforward filter P, where the effective channel H _eff The calculation can be as follows:

H _eff ＝THF (1)

wherein the method comprises the steps ofRepresenting the channel obtained from the full CSI, T representing the antenna selection matrix, F representing the linear precoder, +.>

The gNB 110 forms an antenna selection pattern in the DCI format with r SRIs, implicitly indicating to the UE 120 which antenna/port or antennas/ports should be selected based on the SRIs. Such a format is represented by antenna selection and SRI. The gNB 110 sends 415 such SRI to the UE 120. In this way, the gNB 110 does not have to know the antenna index of the UE 120 and explicit indication of the antenna index by additional signaling is avoided. Thus, signaling overhead may be saved. This approach also provides more flexibility for UE 120 to apply antenna selection, e.g., UE 120 may define its own antenna index rules for SRS transmission.

UE 120 determines 416g nb 110 selected r antennas, i.e., the target antenna set, from the SRI transmitted on the PDCCH. Thus, when the gNB 110 transmits 417 data to the UE 120, the UE 120 receives 418 the data using r antennas in the target antenna set indicated by the SRI and demodulates the data after weighting by the nonlinear precoding DMRS.

Fig. 5 illustrates an interaction diagram of a network device and a terminal device according to some embodiments of the present disclosure. In the embodiment of fig. 5, the gNB initiates an aperiodic SRS trigger including information of the updated antenna set selected by the gNB. The UE transmits an aperiodic SRS with the updated antenna set according to the trigger so that the gNB updates channel state information according to the aperiodic SRS. For ease of discussion, this process will be referred to below simply as the "update Phase".

Similar to the conventional phase, CSI for precoding design is obtained from conventional procedures, which may not be accurate enough for nonlinear precoding, especially for cell-edge UEs. When enhanced performance is required, the precoder needs to be updated. Thus, the gNB may need to obtain updated CSI through aperiodic SRS to improve performance of nonlinear precoding.

In the embodiment shown in fig. 5, the gNB 110 may perform aperiodic SRS transmission at the UE 120 with a selected m antennas (m+.n) only through the SRI trigger 511, i.e., the DCI format includes an SRI field for indicating the aperiodic SRS trigger and includes antenna selection (updating the antenna set, which includes the above-mentioned selected m antennas). Such SRIs have the same mapping as the antenna index in the case of the conventional SRS, but the m antennas selected may be different, partially identical or completely identical to the r antennas selected in the conventional stage. Once UE 120 is triggered, UE 120 determines 512 an update antenna set from the SRI and sends 513 a corresponding aperiodic SRS to gNB 110 for updating CSI. The gNB 110 then updates 514 the nonlinear precoder (possibly additionally if the SRI is different from the regular SRI, m+.r) and sends 515 the data to the UE 120.UE 120 applies the updated antenna set (i.e., the r antennas described above) for data reception 516 and calculates weights for the data streams and demodulates the data through the non-linear precoding DMRS.

Examples of DCI formats proposed in the above-described conventional and update phases are shown in tables 1 and 2 below.

Table 1: DCI format supporting UE antenna selection procedure

Antenna Selection (AS)	Reference to
		0	[]
1	SRI1 (for antenna selection based reception)

Table 2: DCI format supporting aperiodic SRS transmission and UE antenna selection procedure

Table 1 corresponds to the normal phase, where DCI has an Antenna Selection (AS) of 1"1" and SRI is SRI1, indicating that gNB is applied to trigger UE on the antenna based on the selected reception. Table 2 corresponds to an update phase, in which DCI having an SRS type of "a" and SRI1 or SRI2 is used not only to trigger aperiodic SRS transmission with antenna selection, but also to indicate antenna selection based on a corresponding UE-based reception procedure. When the SRI of the DCI is "NULL" (denoted as "NULL" or "[ ]"), no change is made to the determined selected antenna. In this case, it is actually to reuse SRI1, as in the case of table 1. When the SRI in the DCI is SRI2, the antennas used for aperiodic SRS transmission and reception are changed, i.e., the antennas in the updated antenna set are not exactly the same as the previously selected antennas.

Fig. 6 illustrates a frame structure and transmission schematic in accordance with certain embodiments of the present disclosure. It is assumed that the UE has 4 transmit (Tx)/receive (Rx) antennas supporting a correlation function, i.e., tx antennas 0 to 3 (abbreviated as "Tx0 to Tx 3") correspond to Rx antennas 0 to 3 (abbreviated as "Rx0 to Rx 3"), and both are mapped to 0 to 3 SRIs. Subsequently, the UE transmits SRS using antenna switching (from Tx0 to Tx 3) so that the gNB can acquire CSI related to each UE antenna. The gNB does not use the full downlink CSI due to delay problems with CSI obtained at different antennas in different time slots. Thus, the UE periodically reports CSI using SRI to indicate to the gNB the antennas that the UE prefers to get better CSI, i.e., the candidate antenna set.

The gNB performs scheduling, determines the antennas to be used for reception by the UE, i.e., the target antenna set, and precodes data through a concatenation of linear and nonlinear precoding. In the downlink subframe, the gNB informs the UE of the target antenna set in the DCI using SRI, e.g., using table 1, to ensure that the UE receives correctly. In this example, the DCI is AS1& SRI1, where SRI1 corresponds to the selected Rx0.

In case an improved performance is required, aperiodic SRS is triggered together with antenna selection. If the DCI format (see table 2) is a-SRS and null ([ ]), the selected antenna is unchanged and the indicated SRI is still SRI1, i.e. it points to the SRI1 field, which is shared by the indication AS1 and SRI 1. In this example, the aperiodic SRS is transmitted on Tx0, while the reception by the UE still uses Rx0. When the DCI format (see table 2) is a-SRS & SRI2, this means that CSI update should be performed on different selected antennas, in this example Tx0& Tx1. Thus, the DCI format indicating the selected antenna of the UE should be AS1& SRI2, where SRI2 indicates Rx0 and Rx1.

Embodiments according to the present disclosure are also applicable to NR systems using hybrid antenna arrays. In some embodiments, for large antenna arrays in NR systems, then the "antenna" selection is the "port" selection, where a port refers to a level at a Radio Frequency (RF) chain and is not directly linked to an antenna element. If it is all digital, the port corresponds to an antenna. If it is one of the other hybrid array configurations, the ports correspond to RF chains connected to multiple antenna elements). In an embodiment of the present disclosure, the data stream is transmitted to a desired "port", where several "ports"/antennas are available at the UE. In the case of a hybrid array configuration, a plurality of antenna elements are connected to one RF chain and the number of antennas is greater than the number of RF chains. For this procedure, since the gNB can acquire CSI at the reception port level, it can select ports with good CSI (beamformed CSI). Thus, in embodiments of the present disclosure, an "antenna" selection may also be referred to as a "port" selection.

Fig. 7 and 8 illustrate system performance schematic diagrams, respectively, according to certain embodiments of the present disclosure. The cell throughput and UE throughput performance of the scheme according to embodiments of the present disclosure are evaluated with CSI errors as follows. The scheme of the embodiments of the present disclosure is simply referred to as "THP w/antenna selection", compared to two existing schemes, one of which is simply referred to as "THP w/receive combination", and the other of which is simply referred to as "full THP". In this example, the linear combination is designed with THP nonlinear precoding. The full THP scheme at gNB (without linear precoding phase) is considered as optimal. The local small office scenario defined in the WINNER II channel model is applied, with detailed simulation parameters see table 3.

TABLE 3 Table 3

Fig. 7 and 8 show Cumulative Distribution Functions (CDFs) of cell throughput obtained by different schemes for different UE configurations, respectively. In the example of fig. 7, the number of UEs is 8, and in the example of fig. 8, the number of UEs is 16. As can be observed from fig. 7 and 8, in the case of higher level transmission, i.e. 2 streams, the scheme according to embodiments of the present disclosure is superior to the scheme with reception combining and very close to the full THP case. Thus, the scheme according to the embodiments of the present disclosure can obtain similar or even better performance with simple antenna selection than the scheme requiring full downlink CSI, which is very promising for NR MIMO.

Fig. 9 illustrates a block diagram of an apparatus 900 at a terminal device according to some embodiments of the present disclosure. It is to be appreciated that apparatus 900 may be implemented in terminal device 120 shown in fig. 1. As shown in fig. 9, the apparatus 900 includes: a control unit 910 configured to determine a set of candidate antennas from a plurality of antennas at the terminal device based on a pre-measured channel quality, the set of candidate antennas including antennas available for non-linear precoding by a network device; and a transmitting unit 920 configured to transmit information about the candidate antenna set to the network device using the reference signal resource indicator, so that the network device determines a target antenna set for non-linear precoding from the candidate antenna sets.

In some embodiments, the control unit 910 is further configured to: acquiring a pre-measured channel quality for each of the plurality of antennas at the terminal device; and selecting an antenna with channel quality higher than a threshold quality from the plurality of antennas as an antenna in the candidate antenna set.

In some embodiments, the sending unit 920 is further configured to: including information about the set of candidate antennas in a reference signal resource indicator of uplink control information; and transmitting the uplink control information to the network device.

In some embodiments, the apparatus 900 further comprises a receiving unit configured to: information about a set of target antennas is received from the network device.

In some embodiments, the receiving unit is further configured to: receiving downlink control information from the network device; and obtaining information about the set of target antennas from a reference signal resource indicator included in the downlink control information.

In some embodiments, the receiving unit is further configured to: receiving the data non-linearly precoded by the network device using the antennas in the target antenna set; and demodulating the received data based on a demodulation reference signal for nonlinear precoding.

In some embodiments, the sending unit 920 is further configured to: in response to receiving information from the network device regarding an updated set of antennas, transmitting, with antennas in the updated set of antennas, a reference signal to the network device to cause the network device to measure channel information corresponding to the updated set of antennas based on the received reference signal and to non-linearly precode data based on the measured channel information, the updated set of antennas determined by the network device from the candidate set of antennas. The receiving unit is further configured to receive non-linearly precoded data from the network device.

In some embodiments, the information for updating the antenna set is obtained from a reference signal resource indicator included in downlink control information received by the network device.

Fig. 10 illustrates a block diagram of an apparatus 1000 at a network device, according to some embodiments of the disclosure. It will be appreciated that the network device 110 shown in fig. 1 may be implemented. As shown in fig. 10, the apparatus 1000 includes: a control unit 1010 configured to: obtaining information about a candidate antenna set from a reference signal resource indicator received from a terminal device, the candidate antenna set being selected by the terminal device from a plurality of antennas at the terminal device based on a pre-measured channel quality, the candidate antenna set comprising antennas available for non-linear precoding by a network device, and determining a target antenna set for non-linear precoding from the candidate antenna set; and a transmitting unit 1020 configured to transmit information about a set of target antennas to the terminal device.

In some embodiments, the apparatus 1000 further comprises a receiving unit configured to receive uplink control information comprising the reference signal resource indicator from the terminal device; and obtaining information about the set of candidate antennas from the reference signal resource indicator.

In some embodiments, the transmitting unit 1020 is further configured to include information about the set of target antennas in a reference signal resource indicator of downlink control information; and transmitting the downlink control information to the terminal device.

In some embodiments, the control unit 1010 is further configured to: measuring channel information corresponding to the set of target antennas based on a periodic reference signal received from the terminal device; and non-linear precoding data based on the measured channel information. The transmitting unit 1020 is further configured to transmit the non-linearly precoded data to the terminal device.

In some embodiments, the control unit 1010 is further configured to: an updated set of antennas is determined from the set of candidate antennas in response to triggering transmission of the aperiodic reference signal. The transmitting unit 1020 is further configured to transmit information about the updated antenna set to the terminal device, such that the terminal device transmits the aperiodic reference signal to the network device with the antennas in the updated antenna set.

In some embodiments, the transmitting unit 1020 is further configured to: including information about the updated antenna set in a reference signal resource indicator of downlink control information; and transmitting the downlink control information to the terminal device.

In some embodiments, the receiving unit is further configured to receive a reference signal transmitted by the terminal device with an antenna in the updated antenna set. The control unit 1010 is further configured to measure channel information corresponding to the updated antenna set based on the received reference signal; and non-linear precoding data based on the measured channel information. The transmitting unit 1020 is further configured to transmit the non-linearly precoded data to the terminal device.

It should be understood that each of the units recited in apparatus 900 and apparatus 1000 correspond to the steps in methods 200 and 300, respectively, described with reference to fig. 2 and 3. Accordingly, the operations and features described above in connection with fig. 2 and 3 are equally applicable to, and have the same effect as, the apparatus 900 and the apparatus 1000 and the units contained therein, and the specific details are not repeated.

The elements included in apparatus 900 and apparatus 1000 may be implemented in various ways, including software, hardware, firmware, or any combination thereof. In one embodiment, one or more of the units may be implemented using software and/or firmware, such as machine executable instructions stored on a storage medium. In addition to or in lieu of machine-executable instructions, some or all of the elements of apparatus 900 and apparatus 1000 may be implemented at least in part by one or more hardware logic components. By way of example and not limitation, exemplary types of hardware logic components that can be used include Field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), application Specific Standards (ASSPs), systems On Chip (SOCs), complex Programmable Logic Devices (CPLDs), and the like.

The units shown in fig. 9 and 10 may be partly or wholly implemented as hardware modules, software modules, firmware modules or any combination thereof. In particular, in certain embodiments, the above-described flows, methods or processes may be implemented by hardware in a base station or terminal device. For example, a base station or terminal device may implement methods 200 and 300 using its transmitter, receiver, transceiver, and/or processor or controller.

Fig. 11 illustrates a block diagram of a device 1100 suitable for implementing embodiments of the present disclosure. Device 1100 may be used to implement a network device or a terminal device, such as network device 110 and terminal device 120 shown in fig. 1.

As shown, the device 1100 includes a controller 1110. The controller 1110 controls the operation and functions of the device 1100. For example, in some embodiments, the controller 1110 may perform various operations by means of instructions 1130 stored in a memory 1120 coupled thereto. Memory 1120 may be of any suitable type suitable to the local technical environment and may be implemented using any suitable data storage technology including, but not limited to, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems. Although only one memory unit is shown in fig. 11, there may be multiple physically distinct memory units in device 1100.

The controller 1110 may be of any suitable type suitable to the local technical environment and may include, but is not limited to, one or more of a general purpose computer, a special purpose computer, a microcontroller, a digital signal controller (DSP), and a controller-based multi-core controller architecture. The device 1100 may also include a plurality of controllers 1110. The controller 1110 is coupled to a transceiver 1140, which transceiver 1140 may enable the reception and transmission of information by means of one or more antennas 1150 and/or other components.

When device 1100 is functioning as terminal device 120, controller 1110 and transceiver 1140 may operate cooperatively to implement method 200 described above with reference to fig. 2. Wherein the controller 1110 is configured to determine a set of candidate antennas from a plurality of antennas at the terminal device based on a pre-measured channel quality, the set of candidate antennas comprising antennas available for non-linear precoding by a network device. The transceiver 1140 is configured to transmit information about the set of candidate antennas to the network device using a reference signal resource indicator to cause the network device to determine a set of target antennas from the set of candidate antennas for non-linear precoding.

In some embodiments, the controller 1110 is further configured to: acquiring a pre-measured channel quality for each of the plurality of antennas at the terminal device; and selecting an antenna with channel quality higher than a threshold quality from the plurality of antennas as an antenna in the candidate antenna set.

In some embodiments, transceiver 1140 is further configured to: including information about the set of candidate antennas in a reference signal resource indicator of uplink control information; and transmitting the uplink control information to the network device.

In some embodiments, transceiver 1140 is further configured to: information about a set of target antennas is received from the network device.

In some embodiments, transceiver 1140 is further configured to: receiving downlink control information from the network device; and obtaining information about the set of target antennas from a reference signal resource indicator included in the downlink control information.

In some embodiments, transceiver 1140 is further configured to: receiving the data non-linearly precoded by the network device using the antennas in the target antenna set; and demodulating the received data based on a demodulation reference signal for nonlinear precoding.

In some embodiments, transceiver 1140 is further configured to: in response to receiving information from the network device regarding an updated set of antennas, transmitting, with antennas in the updated set of antennas, a reference signal to the network device to cause the network device to measure channel information corresponding to the updated set of antennas based on the received reference signal and to non-linearly precode data based on the measured channel information, the updated set of antennas determined by the network device from the candidate set of antennas. The receiving unit is further configured to receive non-linearly precoded data from the network device.

When device 1100 is acting as network device 120, controller 1110 and transceiver 1140 may operate cooperatively to implement method 300 described above with reference to fig. 3. Wherein the controller 1110 is configured to obtain information from a reference signal resource indicator received from a terminal device regarding a set of candidate antennas selected by the terminal device from a plurality of antennas at the terminal device based on a pre-measured channel quality, the set of candidate antennas comprising antennas available for non-linear precoding by a network device; and determining a target antenna set for nonlinear precoding from the candidate antenna sets. The transceiver 1140 is configured to transmit information about a set of target antennas to the terminal device.

In some embodiments, the transceiver 1140 is further configured to receive uplink control information including the reference signal resource indicator from the terminal device; and obtaining information about the set of candidate antennas from the reference signal resource indicator.

In some embodiments, the transceiver 1140 is further configured to include information about the set of target antennas in a reference signal resource indicator of downlink control information; and transmitting the downlink control information to the terminal device.

In some embodiments, the controller 1110 is further configured to: measuring channel information corresponding to the set of target antennas based on a periodic reference signal received from the terminal device; and non-linear precoding data based on the measured channel information. The transceiver 1140 is further configured to transmit the non-linearly precoded data to the terminal device.

In some embodiments, the controller 1110 is further configured to: an updated set of antennas is determined from the set of candidate antennas in response to triggering transmission of the aperiodic reference signal. The transceiver 1140 is further configured to transmit information about the updated set of antennas to the terminal device, such that the terminal device transmits the aperiodic reference signal to the network device with the antennas in the updated set of antennas.

In some embodiments, transceiver 1140 is further configured to: including information about the updated antenna set in a reference signal resource indicator of downlink control information; and transmitting the downlink control information to the terminal device.

In some embodiments, the transceiver 1140 is further configured to receive a reference signal transmitted by the terminal device using an antenna in the updated antenna set. The controller 1110 is further configured to measure channel information corresponding to the updated set of antennas based on the received reference signal; and non-linear precoding data based on the measured channel information. The transceiver 1140 is further configured to transmit the non-linearly precoded data to the terminal device.

All of the features described above with reference to fig. 2 and 3 apply to the device 1100 and are not described in detail herein.

In general, the various example embodiments of the disclosure may be implemented in 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 aspects of the embodiments of the present disclosure are illustrated or described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

By way of example, embodiments of the present disclosure may be described in the context of machine-executable instructions, such as program modules, being included in devices on a real or virtual processor of a target. 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 described program modules. Machine-executable instructions for 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.

Computer program code for carrying out methods of the present disclosure may be written in one or more programming languages. These computer program code may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus such that the program code, when executed by the computer or other programmable data processing apparatus, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the computer, partly on the computer, as a stand-alone software package, partly on the computer and partly on a remote computer or entirely on the remote computer or server.

In the context of this disclosure, a machine-readable medium may be any tangible medium that can contain, or store a program for or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof. More detailed examples of a machine-readable storage medium include an electrical connection with 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 storage device, a magnetic storage device, or any suitable combination thereof.

In addition, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking or parallel processing may be beneficial. Likewise, although the foregoing discussion contains certain specific implementation details, this should not be construed as limiting the scope of any invention or claims, but rather as describing particular embodiments that may be directed to particular inventions. Certain features that are described in this specification 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 subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not 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 communication method implemented at a terminal device, comprising:

determining a set of candidate antennas from a plurality of antennas at the terminal device based on a pre-measured channel quality, the set of candidate antennas comprising antennas available for non-linear precoding by a network device;

transmitting information about the candidate antenna set to the network device using a reference signal resource indicator, such that the network device determines a target antenna set for non-linear precoding from the candidate antenna set;

receiving information about a set of target antennas from the network device;

in response to receiving information from the network device regarding an updated set of antennas, transmitting, with antennas in the updated set of antennas, a reference signal to the network device to cause the network device to measure channel information corresponding to the updated set of antennas based on the received reference signal and to non-linearly precode data based on the measured channel information, the updated set of antennas determined by the network device from the candidate set of antennas; and

The non-linearly precoded data is received from the network device.

2. The method of claim 1, wherein selecting a set of determined candidate antennas from a plurality of antennas at the terminal device comprises:

acquiring a pre-measured channel quality for each of the plurality of antennas at the terminal device; and

and selecting an antenna with channel quality higher than a threshold quality from the plurality of antennas as an antenna in the candidate antenna set.

3. The method of claim 1, wherein transmitting information about the set of candidate antennas to the network device using a reference signal resource indicator comprises:

including information about the set of candidate antennas in a reference signal resource indicator of uplink control information; and

and sending the uplink control information to the network equipment.

4. The method of claim 1, wherein receiving information about a set of target antennas from the network device comprises:

receiving downlink control information from the network device; and

information about the set of target antennas is obtained from a reference signal resource indicator included in the downlink control information.

5. The method of claim 1, further comprising:

receiving the data non-linearly precoded by the network device using the antennas in the target antenna set; and

demodulating the received data based on a demodulation reference signal for nonlinear precoding.

6. The method of claim 1, wherein the information to update the antenna set is obtained from a reference signal resource indicator included in downlink control information received by the network device.

7. A method of communication implemented at a network device, comprising:

obtaining information about a set of candidate antennas from a reference signal resource indicator received from a terminal device, the set of candidate antennas being selected by the terminal device from a plurality of antennas at the terminal device based on a pre-measured channel quality, the set of candidate antennas including antennas available for non-linear precoding by a network device;

determining a target antenna set for nonlinear precoding from the candidate antenna sets;

transmitting information about a set of target antennas to the terminal device;

determining an updated set of antennas from the set of candidate antennas in response to triggering transmission of the aperiodic reference signal; and

And transmitting information about the updated antenna set to the terminal equipment so that the terminal equipment transmits the aperiodic reference signal to the network equipment by utilizing the antennas in the updated antenna set.

8. The method of claim 7, wherein obtaining information about the candidate antenna set from a reference signal resource indicator received from a terminal device comprises:

receiving uplink control information including the reference signal resource indicator from the terminal device; and

information about the set of candidate antennas is obtained from the reference signal resource indicator.

9. The method of claim 7, wherein transmitting information about a set of target antennas to the terminal device comprises:

including information about the set of target antennas in a reference signal resource indicator of downlink control information; and

and sending the downlink control information to the terminal equipment.

10. The method of claim 7, further comprising:

measuring channel information corresponding to the set of target antennas based on a periodic reference signal received from the terminal device;

performing nonlinear precoding on data based on the measured channel information; and

And sending the data subjected to nonlinear precoding to the terminal equipment.

11. The method of claim 7, wherein transmitting information about updating an antenna set to the terminal device comprises:

including information about the updated antenna set in a reference signal resource indicator of downlink control information; and

and sending the downlink control information to the terminal equipment.

12. The method of claim 7, further comprising:

receiving a reference signal sent by the terminal equipment by using an antenna in the updated antenna set;

measuring channel information corresponding to the updated antenna set based on the received reference signal;

13. A terminal device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory containing instructions stored therein, which when executed by the at least one processor, cause the terminal device to perform the method of any of claims 1 to 6.

14. A network device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory containing instructions stored therein, which when executed by the at least one processor, cause the network device to perform the method of any of claims 7 to 12.

15. A terminal device, comprising:

a control unit configured to determine a set of candidate antennas from a plurality of antennas at the terminal device based on a pre-measured channel quality, the set of candidate antennas including antennas available for non-linear precoding by a network device;

a transmitting unit configured to transmit information about the candidate antenna set to the network device using a reference signal resource indicator, so that the network device determines a target antenna set for non-linear precoding from the candidate antenna sets;

a first receiving unit configured to receive information on a set of target antennas from the network device;

a transmitting unit configured to transmit, in response to receiving information on an updated antenna set from the network device, a reference signal to the network device with antennas in the updated antenna set, such that the network device measures channel information corresponding to the updated antenna set based on the received reference signal and non-linearly precodes data based on the measured channel information, the updated antenna set being determined by the network device from the candidate antenna set; and

A second receiving unit configured to receive the nonlinear precoded data from the network device.

16. A network device, comprising:

a control unit configured to:

obtaining information about a set of candidate antennas from a reference signal resource indicator received from a terminal device, the set of candidate antennas being selected by the terminal device from a plurality of antennas at the terminal device based on a pre-measured channel quality, the set of candidate antennas including antennas available for non-linear precoding by a network device, and

a first transmitting unit configured to transmit information on a set of target antennas to the terminal device;

a determining unit configured to determine an updated antenna set from the candidate antenna sets in response to a transmission of an aperiodic reference signal to be triggered; and

a second transmitting unit configured to transmit information about an updated antenna set to the terminal device, so that the terminal device transmits the aperiodic reference signal to the network device using the antennas in the updated antenna set.

17. A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method according to any of claims 1-6.

18. A computer readable storage medium having stored thereon a computer program which when executed by a processor implements the method according to any of claims 7-12.