CN111886913A

CN111886913A - Communication method and communication device

Info

Publication number: CN111886913A
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: 2020-11-03
Anticipated expiration: 2038-04-19
Also published as: CN111886913B; 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 comprising 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 to cause the network device to determine 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 non-linear precoding and a corresponding communication device.

Background

To improve communication quality, transmitter-side interference cancellation techniques for co-scheduled terminal devices (e.g., UEs) have been studied. These interference cancellation techniques include, for example, non-linear precoding, linear and non-linear hybrid precoding techniques, and the like. The non-linear 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.

Non-linear precoding techniques have been applied and will be further studied in wireless communication systems, particularly in next generation New Radio (NR) systems. 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 UE overlap.

However, there are some problems with the existing non-linear precoding techniques. For example, since a UE is usually installed with multiple antennas, and high-precision full downlink Channel State Information (CSI) is obtained to obtain better performance of non-linear precoding, a large amount of CSI feedback may cause very large overhead and CSI delay. Furthermore, non-linear precoding is generally more sensitive to CSI errors than linear precoding based on signal subspace computation, and therefore non-linear precoding requires explicit and high resolution CSI more, thereby disadvantageously increasing CSI overhead and requiring improved CSI accuracy. These are all 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 improve implementation overhead and complexity of non-linear 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 comprising 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 to cause the network device to determine a target antenna set for non-linear precoding from the candidate antenna set.

In this regard, an embodiment of the present disclosure also provides 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 based on the pre-measured channel quality, the candidate antenna set comprising antennas available for non-linear precoding by the network device; and a transmitting unit configured to transmit information on 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 set.

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 the 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 set; and transmitting information about the target antenna set to the terminal device.

In this regard, embodiments of the present disclosure also provide a network device for communication. The apparatus comprises: a control unit 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 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 the method according to the second aspect.

It should be understood that the statements herein reciting aspects are not intended to limit the critical or essential features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become apparent from the following description.

Drawings

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

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

fig. 2 illustrates a flow diagram of a method implemented at a terminal device side, in accordance with certain embodiments of the present disclosure;

fig. 3 illustrates a flow diagram of a method implemented at the network device side, in accordance with certain embodiments of the present disclosure;

FIG. 4 illustrates an interaction diagram of a network device and a terminal device, in accordance with certain embodiments of the present disclosure;

FIG. 5 illustrates an interaction diagram of a network device and a terminal device, in accordance with certain embodiments of the present disclosure;

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

FIGS. 7 and 8 respectively illustrate system performance diagrams in accordance with 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, in accordance with certain embodiments of the present disclosure; and

fig. 11 illustrates a block diagram of an apparatus 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 are shown in the 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 rather are provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the disclosure are for illustration purposes only and are not intended to limit the scope of the disclosure.

According to embodiments of the present disclosure, a "network device" refers to a base station or other entity or node having a particular function in a communication network. A "base station" (BS) may denote 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 relay, or a low power node such as a pico base station, a femto base station, etc., or the like. In the context of the present disclosure, for ease of discussion, the terms "network device" and "base station" may be used interchangeably, and perhaps primarily with the gNB 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 an example, 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), and the above-described devices in a vehicle. In the context of the present disclosure, the terms "terminal device" and "UE" may be used interchangeably for purposes of discussion convenience.

The terms "include" or "comprise," and variations thereof, as used herein, are inclusive, 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". Relevant definitions for other terms will be given in the following description.

As described above, in the nonlinear precoding system, in order to perform reception combining on 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 both UE reception implementation and CSI acquisition more complicated, increasing implementation difficulty.

Furthermore, the antenna selection process for 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 hereinafter as "antennas"), which increases overhead and increases the difficulty of timing issues. The current indication of the selected antenna is explicit, e.g., 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, then these CSI need 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 method of communication. According to the method of the embodiment of the present disclosure, a terminal device determines a candidate antenna set from a plurality of antennas at the terminal device based on a channel quality measured in advance, the candidate antenna set including antennas available for non-linear precoding by a 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 non-linear precoding from the candidate antenna set. In this way, the non-linear precoding is designed only for the CSI from the antennas of the target antenna set, thereby simplifying the CSI acquisition process and reducing the number of CSI required to be acquired. Meanwhile, the information of the candidate antenna set is indicated by using the reference signal resource indicator, and no field of control information or other control signaling is additionally 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. Communication network 100 includes network device (e.g., gNB)110 and terminal device (e.g., UE)120-1, a.

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 protocol now known or later developed. Moreover, the communication may utilize any suitable wireless communication technique 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 technique 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 of which may provide suitable range and suitable number of coverage, and communication network 100 may also include any suitable type and number of terminal devices.

It should also be understood 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, each UE 120 of the K UEs is assumed to have THP-based non-linear precoding at the gNB110

An antenna. There is M in gNB110_TOne antenna, and r data streams are total, wherein

gNB110 converts r_kAnd transmitting the data stream to the kth UE. In the embodiment of fig. 1, precoding at the side of the gbb 110 includes a linear precoder

112 and a non-linear THP precoder 111 to suppress inter-data stream and inter-user interference.

On the terminal device side, the UE 120 can select an antenna for reception. In some embodiments, the selected antennas may be represented as an antenna selection matrix

Including an index vector

The rows of the identity matrix. In addition, a weighting process is included before demodulation and decoding

And modulo operation Mod (·). Channel with a plurality of channels

Is obtained from the complete CSI, wherein

Is the total number of receive antennas from all UEs.

Conventional non-linear precoding schemes rely on beamformed CSI or full downlink CSI, which the UE needs to perform different reception processes for linear combining. Embodiments of the present disclosure then propose another mode, UE-centric antenna selection, which can effectively solve the problem when the required CSI is not available.

Embodiments of the present disclosure employ a terminal device centric antenna selection non-linear precoding scheme that utilizes SRS Resource Indicator (SRI) in the uplink/downlink signaling format. Rather than using explicit indications about antenna selection (i.e., antenna index), embodiments of the present disclosure utilize the SRI of a particular DCI format to effectively inform each other of selected or down/further selected antennas.

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

At the gNB110, an SRI reference indication format is formed in the Downlink Control Information (DCI) to inform the UE 120 to receive on r of the N antennas (r ≦ N) suitable for data transmission, thereby enabling an antenna selection-based reception procedure.

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

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

Compared to conventional schemes, embodiments of the present disclosure simplify the CSI acquisition process, since only CSI from selected antennas/ports needs to be designed for non-linear 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 enabled and determined by the gNB is required, the gNB must know the antenna indices reported by the UE through some signaling and then request which antenna or antennas the UE applies by indicating these indices. If it is applied together with aperiodic SRS transmission for CSI acquisition, the resources of the aperiodic SRS should also be informed to the UE. The demodulation related indication and the aperiodic SRS related indication should be included in the DCI, e.g., the antenna index and/or SRS resources for each selected antenna, which increases DCI utilization. Since different antennas/groups are allocated with different SRS resources within an antenna switching period, the gNB may simply use the SRI to implicitly indicate to the UE the selected antenna to demodulate the data stream. In case of aperiodic SRS transmission, a specific DCI format including SRI and aperiodic SRS triggering is preferable because SRI includes not only information of the selected antenna but also SRS resources. In the embodiments of the present disclosure, the explicit index of the antenna and the indication of the aperiodic SRS resource in the DCI are replaced by the SRI, thereby effectively saving signaling overhead. In this way, the influence of the CSI error 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, in order to update the precoder, aperiodic SRS transmission and antenna selection can also be jointly triggered by utilizing SRI, where m antennas (also referred to below as an "updated antenna set") of the N selected antennas can be used, where m ≦ N. In this case, the UE need only transmit the aperiodic SRS on the selected antenna, e.g., implicitly indicated by the m SRIs. By the method, the aperiodic SRS and the SRI can be jointly triggered 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 diagram of a method 200 implemented at a terminal device side is shown, in accordance with certain embodiments of the present disclosure. It is to be appreciated that method 200 may be implemented, for example, at terminal device 120 as shown in fig. 1.

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

In some embodiments, 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 sends 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 regarding the candidate antenna set may be included in a reference signal resource indicator of the uplink control information and the uplink control information is transmitted to the 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 target set of antennas may be obtained from a reference signal resource indicator included in the downlink control information.

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

In some cases, the 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. Therefore, the network device 110 may need to obtain updated CSI through aperiodic SRS to improve the performance of non-linear precoding. In some embodiments, terminal device 120 transmits a reference signal to network device 110 using the antennas in the updated antenna set in response to receiving information about the updated antenna set from the network device. 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 is thus aperiodic. Network device 110 may then measure channel information corresponding to the updated antenna set based on the received reference signals and non-linearly precode and transmit data to terminal device 120 based on the measured channel information. At terminal device 120, the non-linearly precoded data may be received from 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, since only CSI from selected antennas/ports is needed to design the non-linear precoding. Furthermore, using SRI to implicitly indicate antenna selection and aperiodic SRS with antenna selection may simplify the non-linear precoding process and save signaling. The antenna selection scheme according to embodiments of the present disclosure can also mitigate the effects of CSI errors and be 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 diagram of a method 300 implemented at a terminal device side is shown, in accordance with certain embodiments of the present disclosure. It is to be appreciated that method 300 may be implemented, for example, at network device 110 as shown in fig. 1.

At 310, network device 110 obtains information about the set of candidate antennas 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 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 target set of antennas for non-linear precoding from the candidate set of antennas. The network device 110 may select an antenna with better channel information from the candidate antenna set as an antenna in the target antenna set according to the measured channel information. In the alternative, the network device 110 may also determine the target antenna set from the candidate antenna set according to preset rules or system requirements, etc.

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

In some embodiments, terminal device 120 may periodically transmit a reference signal, e.g., an SRS, to network device 110. Network device 110 may measure channel information corresponding to the target set of antennas based on periodic reference signals received from the terminal device and may non-linearly precode 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 set of antennas from the set of candidate antennas in response to the transmission of the aperiodic reference signal being to be triggered. The network device 110 may also send information about the updated antenna set to the terminal device 120, such that the terminal device 120 sends aperiodic reference signals to the network device 110 with the antennas in the updated antenna set.

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

Additionally or alternatively, in some embodiments, network device 110 may receive a reference signal, e.g., an SRS, transmitted by terminal device 120 with an antenna in the updated set of antennas. Such a reference signal is an aperiodic reference signal since it is transmitted by the terminal device 120 according to a trigger from the network device 110. 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 non-linearly precode 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 the network device 110 and the terminal device 120 will be further explained 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 by taking a gNB and a UE as examples. It should be understood that this is exemplary and is not intended to limit the embodiments of the present disclosure in any way.

Fig. 4 illustrates an interaction diagram of a network device and a terminal device, in accordance with certain 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, thereby determining a target antenna set for non-linear precoding. For ease of discussion, this process will be referred to hereinafter as the "conventional Phase".

In the embodiment of fig. 4, the UE 120 continuously transmits 411 the reference signal (e.g., SRS) through antenna switching in order to get 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 pre-measured on each antenna/port. The gNB110 does not have to use all downlink CSI, thereby avoiding delay issues between CSI obtained on different antennas in different time slots. Therefore, UE 120 periodically reports 413 implicit CSI with SRI in the uplink control information to indicate to the gNB110 the N antennas in the candidate antenna set that it wishes to use. For example, the UE may periodically feed back N SRIs in the PUCCH to indicate the N antennas to the gNB 110.

Then, at414, the gNB110 obtains CSI, performs scheduling, designs a linear encoder, selects r antennas of N preferred antennas in the candidate antenna set as a target antenna set, and designs nonlinear precoding. In designing a linear encoder, the gNB110 calculates a linear precoder F and constructs an antenna selection matrix T. In designing a nonlinear encoder, the gNB110 designs a nonlinear precoder based on an effective channel for the feedback filter B and the feedforward filter P, where the effective channel H is_effIt can be calculated as follows:

H_eff＝THF (1)

wherein

Denotes a channel obtained from the full CSI, T denotes an antenna selection matrix, F denotes a linear precoder,

the gNB110 forms an antenna selection pattern in the DCI format with r SRIs, implicitly indicating which antenna/port or antennas/ports the UE 120 should determine from the SRIs. Such a format is represented by antenna selection and SRI. The gNB110 sends 415 such SRI to the UE 120. In this way, the gNB110 does not have to know the antenna index of the UE 120 and avoids explicit indication of the antenna index by additional signaling. Thereby, signaling overhead may be saved. This approach also provides more flexibility for the UE 120 to apply antenna selection, e.g., the UE 120 may define its own antenna index rule for SRS transmissions.

The UE 120 determines 416 the r antennas selected by the gNB110, i.e., the target antenna set, from the SRI transmitted on the PDCCH. Thus, when the gNB110 transmits 417 data to the UE 120, at 418, the UE 120 receives the data with r antennas in the target antenna set indicated by the SRI, weights the data with the non-linear precoding DMRS, and demodulates the data.

Fig. 5 illustrates an interaction diagram of a network device and a terminal device, in accordance with certain 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 the aperiodic SRS with the updated set of antennas according to the trigger such that the gNB updates the channel state information according to the aperiodic SRS. For ease of discussion, this process will be referred to hereinafter as the "update Phase".

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

In the embodiment shown in fig. 5, the gNB110 may perform aperiodic SRS transmission with selected m antennas (m ≦ N) at the UE 120 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 selected m antennas described above). Such SRIs have the same mapping as the antenna indices in the case of a conventional SRS, but the m antennas selected may be different, partially identical or completely identical to the r antennas selected in the conventional phase. Once the UE 120 is triggered, the UE 120 determines 512 an updated antenna set from the SRI and sends 513 a corresponding aperiodic SRS to the gNB110 for updating the CSI. The gNB110 then updates 514 the non-linear precoder (and possibly additionally the linear precoder if the SRI is different from the regular SRI, m ≠ r), and sends 515 the data to the UE 120. The UE 120 applies the updated antenna set (i.e., the r antennas described above) for data reception 516 and calculates the weights and demodulation data for the data streams through the non-linear precoding DMRS.

Examples of DCI formats proposed in the above-described two stages, the normal stage and the update stage, 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 reception based on antenna selection)

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

Table 1 corresponds to the conventional phase where DCI with an Antenna Selection (AS) of 1 "1" and SRI of SRI1 indicates that the gNB applies to triggering UE reception on the antenna based on the selection. Table 2 corresponds to an update phase, where DCI with 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 the corresponding UE-based reception procedure. When the SRI of the DCI is "NULL" (denoted as "NULL" or "[ ]"), no changes are made to the determined selected antenna. In this case, the SRI1 is actually reused, 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 diagram according to some embodiments of the present disclosure. Assume that the UE has 4 transmit (Tx)/receive (Rx) antennas supporting the relevant functions, i.e., Tx antennas 0-3 (abbreviated as "Tx 0-Tx 3") correspond to Rx antennas 0-3 (abbreviated as "Rx 0-Rx 3"), and both are mapped to 0-3 SRIs. Subsequently, the UE transmits SRS using antenna switching (from Tx0 to Tx3) so that the gNB can acquire CSI on each UE antenna. Due to delay issues with CSI obtained at different antennas in different time slots, the gbb does not use all downlink CSI. Therefore, the UE periodically reports CSI using SRI to indicate to the gNB the antennas preferred by the UE 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 set of antennas, and precodes the data through a concatenation of linear and nonlinear precoding. In the downlink subframe, the gNB informs the UE of the target antenna set using SRI in DCI, for example, using table 1, to ensure correct reception by the UE. In this example, the DCI is AS1& SRI1, where SRI1 corresponds to the selected Rx 0.

In case of a need for improved performance, aperiodic SRS is triggered together with antenna selection. If the DCI format (see table 2) is a-SRS and null ([ ]), the selected antenna is not changed and the indicated SRI is still SRI1, i.e., it points to the SRI1 field, which is shared by the indications AS1 and SRI 1. In this example, the aperiodic SRS is transmitted on Tx0 while the reception by the UE still uses Rx 0. When the DCI format (see table 2) is a-SRS & SRI2, this means that CSI updates should be performed on different selected antennas, in this example, for example Tx0& Tx 1. Therefore, the DCI format indicating the selected antenna of the UE should be AS1& SRI2, where SRI2 indicates Rx0 and Rx 1.

Embodiments in accordance with 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 a "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. A port corresponds to an RF chain connected to multiple antenna elements if it is one of the other hybrid array configurations). In an embodiment of the present disclosure, the data stream is transmitted to the desired "port", where several "ports"/antennas are available at the UE. In 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 of the receive port level, it can select a port 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 respectively illustrate system performance schematics according to certain embodiments of the present disclosure. Cell throughput and UE throughput performance of the scheme according to embodiments of the present disclosure is evaluated below with CSI errors. The scheme of the embodiment of the present disclosure is simply referred to as "THP w./antenna selection", and compared with two existing schemes, one existing scheme is simply referred to as "THP w./reception combination", and the other existing scheme is simply referred to as "full THP". In this example, linear combinations are designed with THP nonlinear precoding. Consider the full THP scheme (without the linear precoding phase) at the gbb as the best case. The local mini-office scenario defined in the WINNER II channel model is applied, with detailed simulation parameters see table 3.

TABLE 3

Fig. 7 and 8 show Cumulative Distribution Functions (CDFs) of cell throughputs 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. It can be observed from fig. 7 and 8 that in the case of higher level transmission, i.e. 2 streams, the scheme according to embodiments of the present disclosure outperforms the scheme with receive combining and is very close to the full THP case. Therefore, the scheme according to embodiments of the present disclosure may obtain similar or even better performance with simple antenna selection as 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 in accordance with certain embodiments of the present disclosure. It is to be appreciated that apparatus 900 may be embodied 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 candidate antenna set 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 a transmitting unit 920 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 set.

In some embodiments, the control unit 910 is further configured to: obtaining 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 regarding 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 acquiring information on the target antenna set from a reference signal resource indicator included in the downlink control information.

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

In some embodiments, the sending unit 920 is further configured to: in response to receiving information about an updated set of antennas from the network device, transmitting reference signals to the network device with antennas in the updated set of antennas to cause the network device to measure channel information corresponding to the updated set of antennas based on the received reference signals 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, in accordance with certain embodiments of the present disclosure. It is to be appreciated that the implementation can be in the network device 110 shown in fig. 1. As shown in fig. 10, the apparatus 1000 includes: a control unit 1010 configured to: obtaining information on 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 on the target antenna set 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 candidate antenna set from the reference signal resource indicator.

In some embodiments, the transmitting unit 1020 is further configured to include information about the target set of 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 target set of antennas based on periodic reference signals received from the terminal device; and non-linearly 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: determining an updated set of antennas from the set of candidate antennas in response to a transmission of an aperiodic reference signal to be triggered. The transmitting unit 1020 is further configured to transmit information about the updated antenna set to the terminal device, so that the terminal device transmits the aperiodic reference signal to the network device by using the antennas in the updated antenna set.

In some embodiments, the transmitting unit 1020 is further configured to: including information regarding 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 using 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-linearly 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 the apparatus 900 and the apparatus 1000 correspond to respective steps in the

methods

200 and 300 described with reference to fig. 2 and 3, respectively. Thus, the operations and features described above in connection with fig. 2 and 3 are equally applicable to the apparatus 900 and the apparatus 1000 and the units included therein, and have the same effects, and detailed details are not repeated.

The units included in the apparatus 900 and the 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 the alternative to, 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 may be used include Field Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), Application Specific Standards (ASSPs), systems on a chip (SOCs), Complex Programmable Logic Devices (CPLDs), and so forth.

The elements shown in fig. 9 and 10 may be implemented partially or wholly as hardware modules, software modules, firmware modules, or any combination thereof. In particular, in some embodiments, the procedures, methods or processes described above may be implemented by hardware in a base station or a terminal device. For example, a base station or terminal device may implement

methods

200 and 300 with 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 can be used to implement network devices or terminal devices, such as network device 110 and terminal device 120 shown in fig. 1.

As shown, the device 1100 includes a controller 1110. A controller 1110 controls the operation and functions of the device 1100. For example, in certain embodiments, the controller 1110 may perform various operations by way of instructions 1130 stored in memory 1120 coupled thereto. The 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 within 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 general purpose computers, special purpose computers, microcontrollers, digital signal controllers (DSPs), and controller-based multi-core controller architectures. 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 via one or more antennas 1150 and/or other components.

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

In some embodiments, the controller 1110 is further configured to: obtaining 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 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, the transceiver 1140 is further configured to: information regarding a set of target antennas is received from the network device.

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

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

In some embodiments, the transceiver 1140 is further configured to: in response to receiving information about an updated set of antennas from the network device, transmitting reference signals to the network device with antennas in the updated set of antennas to cause the network device to measure channel information corresponding to the updated set of antennas based on the received reference signals 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 in conjunction to implement method 300 described above with reference to fig. 3. Wherein the controller 1110 is configured to obtain information on 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. The transceiver 1140 is configured to transmit information regarding the target set of antennas to the terminal device.

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

In some embodiments, the transceiver 1140 is further configured to include information regarding the target set of 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 target set of antennas based on periodic reference signals received from the terminal device; and non-linearly 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: determining an updated set of antennas from the set of candidate antennas in response to a transmission of an aperiodic reference signal to be triggered. The transceiver 1140 is further configured to transmit information about the 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.

In some embodiments, the transceiver 1140 is further configured to: including information regarding 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 set of antennas. The controller 1110 is further configured to measure channel information corresponding to the updated antenna set based on the received reference signal; and non-linearly 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 apparatus 1100 and are not described in detail herein.

In general, the various example embodiments of this disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Certain aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While aspects of embodiments of the disclosure have been 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 disclosure may be described in the context of machine-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor. 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 divided between program modules as described. Machine-executable instructions for program modules may be executed within local or distributed devices. In a distributed facility, program modules may be located in both local and remote memory storage media.

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

In the context of this disclosure, a machine-readable medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof. More detailed examples of a machine-readable storage medium include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical storage device, a magnetic storage device, or any suitable combination thereof.

Additionally, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking or parallel processing may be beneficial. Likewise, while the above discussion contains certain specific implementation details, this should not be construed as limiting the scope of any 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

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 pre-measured channel quality, the candidate antenna set comprising antennas available for non-linear precoding by a network device; and

transmitting information about the candidate antenna set to the network device with a reference signal resource indicator to cause the network device to determine a target antenna set for non-linear precoding from the candidate antenna set.
The method of claim 1, wherein selecting a determined set of candidate antennas from a plurality of antennas at the terminal device comprises:

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

selecting an antenna from the plurality of antennas having a channel quality above a threshold quality as an antenna in the candidate antenna set.
The method of claim 1, wherein sending information regarding the set of candidate antennas to the network device utilizing 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

transmitting the uplink control information to the network device.
The method of claim 1, further comprising:

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

receiving downlink control information from the network device; and

obtaining information about the target antenna set from a reference signal resource indicator included in the downlink control information.
The method of claim 4, further comprising:

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

demodulating the received data based on a demodulation reference signal for non-linear precoding.
The method of claim 4, further comprising:

in response to receiving information about an updated set of antennas from the network device, transmitting reference signals to the network device with antennas in the updated set of antennas to cause the network device to measure channel information corresponding to the updated set of antennas based on the received reference signals 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

receiving the non-linearly precoded data from the network device.
The method of claim 7, wherein the information updating the antenna set is obtained from a reference signal resource indicator included in downlink control information received by the network device.
A communication method implemented at a network device, comprising:

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;

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

and sending information about the target antenna set to the terminal equipment.
The method of claim 9, wherein obtaining information about a set of candidate antennas 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

obtaining information about the set of candidate antennas from the reference signal resource indicator.
The method of claim 9, wherein sending information about a target set of antennas to the terminal device comprises:

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

transmitting the downlink control information to the terminal device.
The method of claim 9, further comprising:

measuring channel information corresponding to the target set of antennas based on periodic reference signals 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.
The method of claim 9, further comprising:

determining an updated set of antennas from the set of candidate antennas in response to a transmission of a non-periodic reference signal to be triggered;

transmitting information about an updated antenna set to the terminal device to cause the terminal device to transmit the aperiodic reference signal to the network device using the antennas in the updated antenna set.
The method of claim 13, wherein sending information to the terminal device regarding updating the antenna set comprises:

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

transmitting the downlink control information to the terminal device.
The method of claim 13, further comprising:

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

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

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

and sending the data subjected to nonlinear precoding to the terminal equipment.
A terminal device, comprising:

at least one processor; and

a memory coupled with the at least one processor, the memory containing instructions stored therein, which when executed by the at least one processing unit, cause the terminal device to perform the method of any of claims 1-8.
A network device, comprising:

at least one processor; and

a memory coupled with the at least one processor, the memory containing instructions stored therein that, when executed by the at least one processing unit, cause the network device to perform the method of any of claims 9-15.
A terminal device, comprising:

a control unit configured to determine a candidate antenna set 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

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 set.
A network device, comprising:

a control unit configured to:

obtaining information on 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 nonlinear precoding from the candidate antenna set; and

a transmitting unit configured to transmit information about a target antenna set to the terminal device.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the method according to any one of claims 1-8.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the method according to any one of claims 9-15.