WO2024033310A1

WO2024033310A1 - A method for assisting a wireless device with determining a precoder for srs transmission, a related radio network node and a related wireless device

Info

Publication number: WO2024033310A1
Application number: PCT/EP2023/071833
Authority: WO
Inventors: Erik Lennart Bengtsson; Fredrik RUSEK
Original assignee: Sony Group Corporation; Sony Europe B.V.
Priority date: 2022-08-12
Filing date: 2023-08-07
Publication date: 2024-02-15

Abstract

A method is disclosed, performed by a radio network node, for assisting a wireless device with determining a precoder for sounding reference signal transmission. The method comprises sending, to the WD, a signal indicative of a precoder scheme for at least one uplink transmission.

Description

A METHOD FOR ASSISTING A WIRELESS DEVICE WITH DETERMINING A PRECODER FOR SRS TRANSMISSION, A RELATED RADIO NETWORK NODE AND A RELATED WIRELESS DEVICE

The present disclosure pertains to the field of wireless communications. The present disclosure relates to a method for assisting a wireless device (WD) with determining a precoder for sounding reference signal (SRS) transmission, a method for determining a precoder for SRS transmission, a related radio network node and a related wireless device.

BACKGROUND

Increasing use of mobile voice and data communications may require a more efficient utilization of the available radio frequency resources. For increasing data transmission performance and reliability, the so-called multiple input and multiple output (MIMO) technology may be used in wireless radio telecommunication systems for transmitting information between devices, for example between a radio network node and a wireless device. In systems using MIMO technologies the devices may use multiple transmit and receive antennas. For example, the radio network node as well as the wireless device may each comprise multiple send and receive antennas. The MIMO technology forms the basis for coding techniques which use the temporal, spectral, as well as the spatial dimension for transmitting information. The enhanced coding provided in MIMO systems may increase the spectral and energy efficiency of the wireless communication.

The spatial dimension may be used by spatial multiplexing. The spatial multiplexing is a transmission technique in MIMO communications to transmit data signals, so-called streams, from each of the multiple transmit antennas or a combination thereof. Therefore, the spatial dimension is reused or multiplexed more than one time. These streams may further be independent and separately encoded.

Beamforming refers to a technology that arranges the signals transmitted to antennas in the form of beams that are able to power multiple receivers in three dimensions. For example, a base station may comprise a large number of active antenna elements in a two-dimensional grid and may use beamforming to support many spatially separated users on the same time/frequency resource blocks simultaneously. The beams may form virtual sectors which may be static or dynamic in view of the base station. The large number of antennas of the base station allows radio energy to be spatially focused in transmissions as well as a directional sensitive reception which improves spectral efficiency and radiated energy efficiency. In order to adapt the transmit signal at each individual antenna of the radio network node in accordance with the currently active receiving wireless device, a radio network node logic may need information about radio channel properties between the wireless device and the antennas of the radio network node. Vice versa, in order to adapt the transmit signal at each individual antenna of the wireless device, a wireless device logic may need information about the radio channel properties between the radio network node and the antennas of the wireless device. For this purpose, a so-called channel sounding may be performed to determine the radio channel properties between the wireless device and the radio network node. The channel sounding may comprise transmitting predefined pilot signals which may allow the radio network node and the wireless device to set their configuration antenna parameters for transmitting signals so as to focus radio energy or for receiving radio signals from a certain direction.

The radio network node may broadcast beam shaped synchronization signals (so-called SS-bursts). Different SS-bursts targeting different directions or polarizations are distributed both in time and frequency domain such that each beam is occurring at each sub-band over time. The wireless device may listen for the SS-bursts and may use the received signal to calibrate frequency and timing. The wireless device may scan or adjust its receive beam in order to find the direction that is associated with the strongest SS- burst. The radio network node may repeatedly perform beam sweeps in dedicated resources. Each transmitted beam may comprise a Channel State Information - Reference Signal (CSI-RS) (pilot), synchronization information, and a beam identifier (beam ID).

The aggregated congestion of all connected wireless devices, particularly in urban areas, is problematic. The solution in MIMO of dividing the cells in smaller sectors, for example, using multiple transmission and reception points (TRPs) can increase the resolution of the base station and enable it to separate users in the spatial domain by the use of beamforming. In principle, by using TRPs, the cell can be divided into sub-cells where different wireless devices can be served simultaneously using the same time/frequency resources.

A problem associated with the concept of beamforming is leakage between the different beams transmitted from the radio network node and/or the wireless devices. Specifically, at lower frequencies when the size of each antenna element, in both the wireless device and the radio network node, is big, the antennas in the wireless device may have limited capability to direct the power toward the radio network node, and the beam width from the radio network node also gets wider due to limited physical size of the antennas. Also, at least at certain frequencies, a wireless device may cause and/or be exposed to interference from neighboring beams.

A further problem is the scheduling complexity at the radio network node due to many signals being received at the multiple TRPs of the radio network node.

A further problem is that after the radio network node has transmitted downlink reference signaling, the network node does not possess channel state information and can therefore not control the wireless device’s transmission. A legacy solution is to let the wireless device feedback the channel state information to the radio network node. However, this introduces overhead.

SUMMARY

Accordingly, there is a need for devices and methods for enabling a WD to determine a precoder for sounding reference signal, SRS, transmission, which may mitigate, alleviate or address the shortcomings existing and may provide a more efficient handling of uplink transmissions, such as SRS transmissions, in a wireless communications network.

Further, a radio network node is provided, the radio network node comprising memory circuitry, processor circuitry, and a wireless interface, wherein the radio network node is configured to perform any of the methods according to this disclosure and relating to the radio network node.

It is an advantage of the present disclosure that a spectral efficiency and power efficiency of the wireless communications network can be increased. By the radio network node sending the signal indicative of a precoder scheme to be used for the at least one uplink transmission, such as for SRS transmission, the radio network node may configure the wireless device to use a precoder that improves an overall network efficiency, such as an overall spectral and/or power efficiency, rather than a precoder that is optimal for the respective WD. For a specific wireless device, the optimal precoder is usually a dominant eigenmode precoder based on the channel conditions between the wireless device and one or more TRPs of the radio network node. However, to improve an overall network efficiency based on network conditions each wireless device using a suboptimal precoder, from the wireless device’s perspective, may be beneficial. Since the radio network node has the overview of the network and other wireless devices communicating with the radio network node, the radio network node can configure one or more wireless devices with the most suitable precoder for the current network conditions. Further, by the radio network node sending an indication of the precoder scheme to the WD, the radio network node can inform the WD about what the objective with the precoding should be and then let the WD determine the actual precoder based on the channel conditions. Thereby, no feedback of channel state information from the WD to the radio network node is needed, which can reduce the overhead in the system. Further, a computational complexity at the radio network node may be reduced, since some of the computation, such as determining the precoder, can be pushed onto the WD. Even in situations where there is only one WD in a cell (or sub-cell) and the aim is to maximize the performance of that WD, the radio network node may push some computation onto the WD so that the WD can use the same rules that the radio network node would have used if it were to perform the calculations/computations itself.

The present invention may be further advantageous in future cell-free systems. In such a system, a number of TRPs co-operate like a distributed antenna system to provide constant coverage without requiring handover of WD handling between cells. In such a case, the CSI-RS may be either individually or jointly broadcasted from the TRPs. The present invention may enable a WD to communicate efficiently with a selected set of the available TRPs (using joint coherent transmissions) and also aim to minimize interference directed at other TRPs.

A method is disclosed, performed by a WD, for determining a precoder for SRS transmission. The method comprises receiving, from a radio network node, a signal indicative of a precoder scheme for at least one uplink transmission. The method comprises transmitting, to the radio network node, SRS based on the received precoder scheme, such as the precoder scheme indicated in the signal received from the radio network node.

Further, a wireless device is provided, the wireless device comprising memory circuitry, processor circuitry, and a wireless interface, wherein the wireless device is configured to perform any of the methods according to this disclosure and relating to the wireless device.

It is an advantage of the present disclosure that a spectral efficiency and power efficiency of the wireless communications network can be increased. By the radio network node sending the signal indicative of a precoder scheme to be used for the at least one uplink transmission, such as for SRS transmission, the wireless device may be configured to use a precoder that improves an overall network efficiency, such as an overall spectral and/or power efficiency, rather than a precoder that is optimal for the respective wireless device. For a specific wireless device, the optimal precoder is usually a dominant eigenmode precoder based on the channel conditions between the wireless device and one or more TRPs of the radio network node. However, to improve an overall network efficiency based on network conditions each wireless device using a suboptimal precoder, from the wireless device’s perspective, may be beneficial. Since the radio network node has the overview of the network and other wireless devices communicating with the radio network node, the wireless device can be configured with the most suitable precoder for the current network conditions by the radio network node. Further, by the radio network node sending an indication of the precoder scheme to the WD, the WD can be informed about what the objective with the precoding should be and can then determine the actual precoder based on the channel conditions. Thereby, no feedback of channel state information from the WD to the radio network node is needed, which can reduce the overhead in the system. Further, a computational complexity at the radio network node may be reduced, since some of the computation, such as determining the precoder, can be done by the WD. Even in situations where there is only one WD in a cell (or sub-cell) and the aim is to maximise the performance of that WD, the radio network node may push some computation onto the WD so that the WD can use the same rules that the radio network node would have used if it were to perform the calculations/computations itself, the performance of that WD, the radio network node may push some computation onto the WD so that the WD can use the same rules that the radio network node would have used if it were to perform the calculations/computations itself.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present disclosure will become readily apparent to those skilled in the art by the following detailed description of examples thereof with reference to the attached drawings, in which:

Fig. 1 is a diagram illustrating an example wireless communication system comprising an example network node and an example wireless device according to this disclosure,

Fig. 2A-2B are diagrams illustrating an example method for a WD to obtain channel information for a plurality of channels according to this disclosure,

Fig. 3A-3C are diagrams illustrating different precoder schemes for different network scenarios according to this disclosure,

Fig. 4 is a flow-chart illustrating an example method, performed in a radio network node, for assisting a wireless device with determining a precoder for sounding reference signal transmission according to this disclosure,

Fig. 5 is a flow-chart illustrating an example method, performed in a wireless device of a wireless communication system, for determining a precoder for sounding reference signal transmission according to this disclosure, Fig. 6 is a block diagram illustrating an example radio network node according to this disclosure, and

Fig. 7 is a block diagram illustrating an example wireless device according to this disclosure.

DETAILED DESCRIPTION

Various examples and details are described hereinafter, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the examples. They are not intended as an exhaustive description of the disclosure or as a limitation on the scope of the disclosure. In addition, an illustrated example needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular example is not necessarily limited to that example and can be practiced in any other examples even if not so illustrated, or if not so explicitly described.

The figures are schematic and simplified for clarity, and they merely show details which aid understanding the disclosure, while other details have been left out. Throughout, the same reference numerals are used for identical or corresponding parts.

Fig. 1 is a diagram illustrating an example wireless communication system 1 comprising an example radio network node 400 and an example wireless device 300 according to this disclosure.

As discussed in detail herein, the present disclosure relates to a wireless communication system 1 comprising a cellular system, for example, a 3GPP wireless communication system. The wireless communication system 1 comprises a wireless device 300 and/or a radio network node 400.

A radio network node disclosed herein refers to a radio access network node operating in the radio access network, such as a base station, an evolved Node B, eNB, gNB in NR. In one or more examples, the RAN node is a functional unit which may be distributed in several physical units. In one or more examples, the RAN node is a functional unit which may be distributed in several physical units. In one or more examples, the radio network node may have, such as may be associated with, one or more transmission and reception points (TRPs) 401 A, 401 B. A TRP 401 A, 401 B can herein be seen as an antenna array, such as one or more antenna elements, available to the network, such as to the radio network node for transmission and/or reception of signals to and/or from a WD 300 via a respective channel set up via a wireless link 10. A TRP 401 A, 401 B may be located at a specific geographical location.

The wireless communication system 1 described herein may comprise one or more wireless devices 300, 300A, and/or one or more network nodes 400, such as one or more of: a base station, an eNB, a gNB and/or an access point.

A wireless device may refer to a mobile device and/or a user equipment, UE.

The wireless device 300, 300A may be configured to communicate with the network node 400 and/or with the TRPs 401 A, 401 B via a wireless link (or radio access link) 10, 10A.

Fig. 2A and 2B illustrate an example method for a WD 300 to obtain channel information for a plurality of channels between the WD 300 and a radio network node 400, such as between the WD 300 and a plurality of TRPs, illustrated in Fig. 2A-2B as TRP 1 and TRP 2, associated with the radio network node 400. In one or more example scenarios, for a system with a limited set of TRP antennas and TRP nodes the WD 300 may obtain, such as acquire, channel information based on downlink channel state information reference signals (CSI-RS), such as broadcasted CSI-RS. As can be seen in Fig. 2A, the WD 300 may receive CSI-RS from a first TRP, such as TRP1 , via a plurality of antennas. In the example shown in Fig. 2A and 2B the WD 300 comprises two antennas. The WD 300 may thus receive the CSI-RS from TRP1 via a first antenna and a second antenna. The WD may create a matrix representation 11 , such as a covariance matrix representation, of the channels between the radio network node and the WD, such as between the TRPs associated with the radio network node and the antennas of the WD. The matrix representation 11 of the channels may herein be referred to as a channel matrix. The columns in the channel matrix 11 correspond to a CSI-RS received from a specific TRP. The rows in the channel matrix 11 correspond to respective antennas, such as receiver (Rx) antennas, at the WD. As can be seen in Fig. 2A, the WD receives CSI-RS from TRP1 via the first antenna and via the second antenna and may estimate the respective channels. The channel between TRP1 and the first antenna of the WD 300 is indicated as Ai 1 in the channel matrix 11 in Fig. 2A. The channel between TRP1 and the second antenna of the WD 300 is indicated as A12 in the channel matrix 11 in Fig. 2A. Each CSI- RS received from a TRP allows one column of the matrix representation to be estimated by the WD. Correspondingly, upon a second TRP, such as TRP2 in Fig. 2B, transmitting CSI-RS to the WD 300, the WD 300 may determine the second column of the channel matrix 11 , such as the channels between TRP2 and the respective antennas at the WD 300. The channel between TRP2 and the first antenna of the WD 300 is indicated as A21 in the channel matrix 11 in Fig. 2B. The channel between TRP2 and the second antenna of the WD 300 is indicated as A22 in the channel matrix 11 in Fig. 2B.

Figs. 3A-3C illustrate different precoder schemes for different network scenarios, such as for different precoding objectives. In one or more example methods, such as shown in Fig. 3A, an objective may be to maximize a gain of the transmission channels in DL. The objective may be signaled from the radio network node 400 to the WD 300, for example by sending a signal indicative of a precoder scheme for at least one uplink transmission to the WD 300. This may be the case for coherent joint transmission (CJT). Coherent joint transmission can be seen as a kind of beamforming for which the antennas taking part in the beamforming are not co-located but correspond to different transmission points. The WD 300 can be configured to determine eigenmodes of the channels, for example based on the CSI-RS, and to transmit precoded uplink sounding reference signals (SRS) to address the eigenmodes of each channel. The WD 300 may be configured to maximize the gain by applying a precoder scheme to the SRS, such that the precoded uplink SRS (PM, P2A) maximizes the sum of powers of the signal ( M, r₂A) received at the TRPs via the channels A11-A22. In other words, the precoded SRS signal pi_A, P2A may be selected such that \r_1A |² + |r₂ |² is maximized. In one or more example methods, this precoder scheme may be indicated as a third mode, or third operational mode, precoder scheme.

The solution according to this disclosure may be advantageous in future cell-free systems. In such a system, a number of TRPs co-operate like a distributed antenna system to provide constant coverage without requiring handover of WD handling between cells. In such a case, the CSI-RS may be either individually or jointly broadcasted from the TRPs. The present invention may enable a WD to communicate efficiently with a selected set of the available TRPs (such as using joint coherent transmissions) and also aim to minimize interference directed at other TRPs. Possible interference between the channels, or to other TRPs, may need to be handled by the network, such as by the radio network node. The network, such as the radio network node may, based on SRS received from multiple WDs, reduce transmissions in directions not intended, e.g., by configuring a zero-forcing precoder scheme. Zero-forcing precoding can be seen as a method of spatial signal processing by which a multiple antenna transmitter, such as the WD for uplink transmissions, can null multiuser interference in a MIMO wireless communication system. When the channel state information is perfectly known at the transmitter, such as at the WD in uplink, the zero-forcing precoder may be given by a pseudo-inverse of a channel matrix.

In one or more example methods, the objective for the scenario described above may be for the WD 300 to aid an interference reduction, such as to minimize interference from neighboring TRPs in DL (such as originating from pilot signal contamination). In this case the WD 300 may be configured to derive, such as select, a precoder addressing a subspace with minimum interference toward neighboring TRPs based on CSI-RSs. This is not intended for the case where CJT is applied between the same set of TRPs.

In one or more example methods, such as shown in Fig. 3B, the WD 300 can be configured to select a precoder such that the transmitted precoded SRS maximizes the power of the signal received at the best TRP, such as at the TRP having the best channel conditions. The best TRP may for example be a TRP having Line of Sight (LOS) conditions with the WD or having good Signal-to-Noise-ratio (SNR) on the channel, such as having SNR above an SNR threshold. The WD 300 may be configured to apply a precoder scheme to the SRS, such that the precoded uplink SRS pi_B, P2B of Fig. 3B maximizes the power of the signal r-iB received at the first TRP, such as TRP1 in Fig. 3B, via the channels A11-A12. In other words, the precoded SRS signal pi_A, P2A may be selected such that max (|r_1B |², \r_2B |²) is maximized. This may be referred to as a dominant eigenmode precoder. In one or more example methods, this precoder scheme may be indicated as a first mode, or first operational mode, precoder scheme. By maximizing the power at the best TRP the power at the second TRP, such as TRP2 in Fig. 3B, is neglected. Thereby, the interference towards TRP2 neighboring TRP1 is handled by other means. In one or more example methods, such as shown in Fig. 3C, the WD 300 can be configured to select a precoder such that the WD transmits precoded SRS such that power at a first TRP, such as at a less good TRP (for example having a weaker signal than a second TRP), such as TRP1 in the example shown in Fig. 3C, is zero (or at least minimized) and the power is maximized towards a second TRP, such as a best TRP, such as TRP2 in the example shown in Fig. 3C. The WD 300 may be configured to apply a precoder scheme to the SRS, such that the precoded uplink SRS pic, P2C of Fig. 3C eliminates the power of the signal ric received at the first TRP, such as TRP1 in Fig. 3C, via the channels A11-A12, while maximizing the power of the signal r?c received at the second TRP, such as TRP2 in Fig. 3C. In the example shown in Fig. 3C, the signal ric is eliminated since it is the weakest signal, however in one or more example methods r₂c can be the weakest signal and may thus be eliminated. Eliminating the power can herein be seen as reducing the power toward zero. In other words, the precoded SRS signal pic, P2C may be selected such that the strongest signal, such as max (|r_1B |², |r_2B |²), is maximized subject to the weakest signal being min(\r_1B , |r_2B|²) =

This may be referred to as a zero-forcing mode. In one or more example methods, this precoder scheme may be indicated as a second mode, or second operational mode, precoder scheme. By eliminating the power at one of the TRPs, such as TRP1 in Fig. 3C, the interference experienced by this TRP

In one or more example methods, the TRP may have a massive set of antennas, such as when the TRP is configured for massive MIMO, it may not be feasible to acquire CSI based on broadcasted CSI-RS at the WD (as there are infinite options for the TRP to find a precoder). At least initially, a codebook-based precoding scheme may be preferable. However, if the WD can receive CSI-RS which are associated with the SRS (e.g., SRS based DL CSI acquisition), the WD can get a good estimate of the covariance matrix and further derive the eigenmodes of the channels based on hardening, such as channel hardening. Channel hardening means that, when increasing the number of TRPs in a massive MIMO system the channel variations, such as the variations of the channel gain in time and frequency, decrease and a so-called channel hardening effect appears. In one or more example methods, SRS for interference may be introduced where associated CSI-RS from interfered nodes may be detected and avoided by the WD by means of a corresponding precoder selection. Fig. 4 shows a flow diagram of an example method 100, performed by a radio network node according to the disclosure, for assisting a WD with determining a precoder for SRS transmission. The radio network node is the radio network node disclosed herein, such as network node 400 of Fig. 1 , Fig. 2A-2B, Fig. 3A-3C, and Fig. 6. The radio network node may be a serving radio network node, such as a radio network node serving the WD.

In one or more example methods, the method comprises obtaining S101 an indication indicative of a channel condition between the WD and one or more transmission points of the radio network node.

In one or more example methods, the obtaining S101 comprises receiving S101A a pilot signal from the WD. In one or more example methods, the pilot signal is one or more nonprecoded SRS. A non-precoded SRS can herein be seen as an SRS being transmitted by the WD and/or received by the radio network node without applying a precoder to the SRS, such as a raw SRS. The raw SRS can also be considered an SRS with a preconfigured precoder possibly associated with an antenna port. The simplest example is transmission of an SRS from each antenna independently.

In one or more example methods, the method comprises transmitting S103 CSI-RS based on the indicated channel condition. In one or more example methods, the radio network node may derive the CSI-RS to transmit from the pilot signal, such as the non-precoded SRS, received from the WD. Each CSI-RS may for example be associated with a nonprecoded SRS. The CSI-RS may be transmitted via one or more TRPs associated with, such as controlled by, the radio network node. By transmitting the CSI-RS via the one or more TRPs associated with the radio network node, the radio network node can enable the WD to determine channel conditions for a respective channel between the WD and the one or more TRPs. However, in one or more example methods, the CSI-RS may be transmitted without any SRS, such as non-precoded SRS, being sent.

In one or more example methods, the method comprises determining S104, based on network conditions, the precoder scheme for at least one uplink transmission. A network condition can herein be seen as a state of the network, such as the wireless communications network, affecting the performance of the communication, such as transmissions and/or receptions, in the network. In one or more examples, the network conditions may affect one or more performance parameters of a communication channel of the network, such as jitter, and/or throughput, and/or latency of the communications channel. The network conditions may comprise one or more of radio channel conditions, network load, interference conditions, power consumption conditions, backhaul conditions and a number of WDs in the wireless communications network.

The method 100 comprises sending S105, to the WD, a signal indicative of a precoder scheme for at least one uplink transmission. The at least one uplink transmission may in one or more example methods be an SRS transmission. Sending S105 the signal may comprise one or more of broadcasting the signal and or sending the signal via unicast, such as using Single Input Single Output (SISO) transmission.

In one or more example methods, the precoder scheme is indicated by an operational mode for the at least one uplink transmission. In one or more example methods, a plurality of precoder schemes may be preconfigured and/or may be stored in a database. Each of the preconfigured and/or stored precoder schemes may be referred to as a mode, such as an operational mode, of the precoder.

In one or more example methods, the precoder scheme is indicative of one or more of a power threshold, an interference threshold, and an operational threshold to be applied to an uplink channel. The operational threshold may in one or more example methods be indicative of a number of transmission and reception points (TRPs) to transmit to. All TRPs may be assumed to transmit CSI-RS which can be used by the WD when it computes a precoder and determines the power ratios and or channel conditions. The operational threshold may in one or more example methods be indicative of a directional threshold, such as a certain direction to transmit to. The directional threshold may comprise an upper and a lower threshold. The directional threshold may be selected such that only TRPs in a certain direction are transmitted to by the WD, for example when the WD is moving. The directional threshold may for example be indicated as a transmission angle. The directional threshold may for example be indicated as a transmission angle, such as a set of allowed spherical angles. The directional threshold may, in one or more example methods, comprise an upper and a lower threshold, and/or thresholds, such as upper and/or lower thresholds, on both azimuth and elevation.

The power threshold may, in one or more example methods, be indicative of a certain power, such as a minimum power to maintain or to provide towards at least one TRP. The interference threshold may, in one or more example methods, be indicative of a certain interference, such as a maximum interference, that is allowable towards at least one TRP. In one or more example methods, the interference threshold may be indicated as a maximum power threshold, such as a maximum power, that is allowable towards at least one TRP, to maintain the interference at the at least one WD below the maximum allowable interference. In one or more example methods, the power threshold and/or the interference threshold can be associated with an operational threshold, such as a directional threshold. By associating the power threshold and/or the interference threshold with the operational threshold, the precoder scheme may indicate in which direction, such as towards which TRPs, the power threshold and/or the interference threshold is to be applied.

In one or more example methods, the precoder scheme is indicative of an activation/deactivation (on/off) of interference mitigation, such as interference minimization, to TRPs not belonging to the serving radio network node, such as the radio network node serving the WD.

In one or more example methods, the precoder scheme is indicative of one or more of a power to be maximized, a power to be minimized, a signal to be minimized, a signal to be maximized, a sum of power to be maximized, and an interference to be minimized. In one or more example methods, the precoder scheme may indicate to the WD that the WD is to maximize a signal towards a first TRP, such as a TRP1 , and once the WD has done so, the WD is enabled to, or is to, maximize a signal toward a second TRP, such as a TRP2, on the basis that this does not affect the maximized signal to the first TRP, such as TRP1 . This may for example be indicated as maximizing “Power to TRP 2” subject to “power to TRP 1= P” or power to TRP 1> P, for some value of P. In other words, the power to TRP2 can be maximized as long as the power to TRP1 remains equal to or above a power threshold for TRP1 .

This may also apply, vice versa, for minimization of a signal toward one TRP. In one or more example methods, the precoder scheme may indicate that a power is to be maximized for a certain TRP and/or that a power is to be minimized for a certain TRP. In one or more example methods, the precoder scheme may indicate that the SRS transmission is to be precoded such that the transmit power towards a best TRP, such as the TRP having the best channel conditions, is maximized. Correspondingly, in one or more example methods, the precoder scheme may indicate that the SRS transmission is to be precoded such that the transmit power towards a TRP having the less good channel conditions, is minimized. Best channel conditions and less good channel conditions can herein be seen as the channel condition of a first channel compared to a second channel, such as respective channels between the WD and a first TRP and a second TRP. In this example precoder scheme, a signal may be transmitted to both the first TRP and the second TRP but with different transmission power. In one or more example methods, this precoder scheme may be indicated as a first mode, such as a first operational mode, precoder scheme.

In some cases, the WD may be configured to derive a precoder that equalizes the power received at two or more TRPs.

In one or more example methods, the precoder scheme may indicate that a signal is to be minimized for a certain TRP and/or that a signal is to be maximized for a certain TRP. Maximizing the signal for a certain TRP can be seen as maximizing the transmit power towards that TRP, such as towards the TRP having the best channel conditions. Minimizing the signal for a certain TRP can be seen as minimizing the transmit power, such as setting the transmit power to zero, towards that TRP, such as towards the TRP having less good channel conditions or towards a TRP not being associated with a serving radio network node of the WD. Minimizing the signal for a certain TRP, such as minimizing the transmit power towards the TRP, can in one or more example methods be seen as not transmitting the signal towards the TRP. Not transmitting the signal towards the TRP can herein be seen as minimizing an interference for the TRP. In one or more example methods, the precoder scheme may indicate that only a signal to a certain TRP is to be minimized without affecting the signal to the other TRP. In one or more example methods, the precoder scheme may indicate that the signal is to be maximized for a first TRP, such as the TRP having the best channel conditions, and is to be minimized for a second TRP, such as the TRP having less good channel conditions or a TRP not being associated with the serving radio network node of the WD. The same precoder scheme may thus be indicated by one or more of indicating that a signal is to be maximized for a first TRP and/or a signal is to be minimized for a second TRP, by indicating that an interference is to be minimized for the second TRP, and by indicating that the power is to be maximized for the first TRP and/or the power is to be minimized for the second TRP. In one or more example methods, this precoder scheme may be referred to as a zero-forcing precoder scheme. In one or more example methods, this precoder scheme may be indicated as a second mode, or second operational mode, precoder scheme. In one or more example methods, such as when there are only two antenna ports at both the WD and the radio network node, such as the radio network node having two TRPs, then zero forcing, such as minimizing the power of the signal, to one TRP implies a unique solution where all the transmit power is going to the other TRP, hence there is nothing to maximize for the second TRP. However, the WD and the radio network node have more than two antenna ports, and the radio network node or the WD can choose to which TRPs zeroforcing is to be applied to, a signal to one or more remaining TRPs may be maximized. Whether to maximize the signal and which TRPs to maximize the signal to, may be indicated in the precoder scheme, for example via an index of the TRP.

In one or more example methods, such as when there are more antenna ports at the radio network node than at the WD, there may be no zero-forcing applied since the WD does not have enough antenna ports to cancel out all of the antenna ports except one at the radio network node, however, an energy-minimizing precoder may be unique, such as leaving only one remaining antenna port at the WD for transmitting the signal to the radio network node. Hence, there may be nothing to maximize.

In one or more example methods, such as when the WD has more antenna ports than the radio network node, one antenna port, such as one TRP, can be zero-forced while the WD is still having a plurality of antenna ports to provide a maximization of the signal towards a remaining antenna port at the radio network node. Remaining antenna port can herein be seen as the antenna ports that have not been zero-forced. The energy, such as the power to these remaining antenna ports can thus be optimized, while still achieving zero-forcing at one of the antenna ports.

In one or more example methods, the precoder scheme may indicate that a sum of power, such as a sum of the transmit powers at a plurality of TRPs, such as at the first TRP and at the second TRP, is to be maximized. This example precoder scheme may indicate to the WD that the WD is to select a precoder scheme which maximizes the sum of the power of the received signals at the plurality of TRPs, such as at the TRPs combined. In one or more example methods, this precoder scheme may be indicated as a third mode, or third operational mode, precoder scheme. In one or more example methods, the precoder scheme is indicative of an index of one or more TRPs for which associated signals are to have the precoder scheme applied. The precoder scheme may comprise an index of the one or more TRPs, such as an identifier of the one or more TRPs, to which the precoder scheme is to be applied, such as to which TRP a signal and/or a power, such as transmit power, is to be maximized or minimized.

In one or more example methods, the sending S105 is performed upon transmitting Channel State Information-Reference Signals, Signals, CSI-RS, to the WD. Since the WD may transmit the SRS in real time in response to receiving the CSI-RS, the WD has to know what to do with the received CSI-RS at their arrival at the WD. The radio network node may thus send the precoder scheme upon transmitting the CSI-RS to inform the WD how the WD is to transmit SRS in response to the CSI-RS, such as which precoder scheme the WD is to apply.

In one or more example methods, interference signal properties (such as properties relating to TRPs not belonging to the serving radio network node) may not be based on CSI-RS but left to the WD to estimate based on other signaling.

In one or more example methods, the method comprises transmitting S107, to the WD, one or more of a Physical Downlink Control Channel, PDCCH, and a Physical Downlink Shared Channel, PDSCH, based on the indicated precoder scheme. In one or more example methods, the radio network node may use the same precoder scheme as used for precoding the SRS for transmitting in downlink to the WD, such as on the PDSCH and/or the PDCCH.

In one or more example methods, the method comprises receiving S109, from the WD, SRS based on the indicated precoder scheme.

Fig. 5 shows a flow diagram of an example method 200, performed by a wireless device according to the disclosure, for determining a precoder for SRS transmission. The wireless device is the wireless device disclosed herein, such as wireless device 300 of Fig. 1 , Fig. 2A-2B, Fig. 3A-3C and Fig. 7.

In one or more example methods, the method comprises providing S201 , to the radio network node, an indication indicative of a channel condition between the WD and one or more TRPs of the radio network node. In one or more example methods, providing S201 comprises transmitting S201 A a pilot signal to the radio network node. In one or more example methods, the pilot signal is a non-precoded SRS. A non-precoded SRS can herein be seen as an SRS being transmitted by the WD and/or received by the radio network node without applying a precoder to the SRS. The indication indicative of the channel condition, such as the pilot signal, such as the non-precoded SRS, may be used by the radio network node to derive the CSI-RS to transmit.

The method 200 comprises receiving S203, from the radio network node, a signal indicative of a precoder scheme for at least one uplink transmission. The radio network node may be a radio network node serving the WD.

In one or more example methods, the precoder scheme is indicated by an operational mode for the at least one uplink transmission. In one or more example methods, a plurality of precoder schemes may be preconfigured and/or may be stored in a database. Each of the preconfigured and/or stored precoder schemes may be referred to as a mode, such as an operational mode, of the precoder. The precoding scheme indicated in the signal can herein be seen as a precoder scheme received by the wireless device from the radio network node.

In one or more example methods, the precoder scheme is indicative of one or more of a power threshold, an interference threshold, and an operational threshold to be applied to an uplink channel. The operational threshold may in one or more example methods be indicative of a number of TRPs to transmit to. The operational threshold may in one or more example methods be indicative of a directional threshold, such as a certain direction to transmit to. The directional threshold may comprise an upper and a lower threshold. The directional threshold may be selected such that only TRPs in a certain direction are transmitted to by the WD, for example when the WD is moving. The directional threshold may for example be indicated as a transmission angle. In one or more example methods, the precoder scheme is indicative of an activation/deactivation (on/off) of interference mitigation, such as interference minimization, to TRPs not belonging to the serving radio network node, such as the radio network node serving the WD. The activation/deactivation, such as the on/off indication, may be signaled using a dedicated signal. In one or more example methods, the precoder scheme is indicative of one or more of a power to be maximized, a power to be minimized, a signal to be minimized, a signal to be maximized, a sum of power to be maximized, and an interference to be minimized. In one or more example methods, the precoder scheme may indicate that a power is to be maximized for a certain TRP and/or that a power is to be minimized for a certain TRP. In one or more example methods, the precoder scheme may indicate that the SRS transmission is to be precoded such that the transmit power towards a best TRP, such as the TRP having the best channel conditions, is maximized. Correspondingly, in one or more example methods, the precoder scheme may indicate that the SRS transmission is to be precoded such that the transmit power towards a TRP having the less good channel conditions is neglected. Best channel conditions and less good channel conditions can herein be seen as the channel condition of a first channel compared to a second channel, such as respective channels between the WD and a first TRP and a second TRP. In this example precoder scheme, a signal may be transmitted to both the first TRP and the second TRP but with different transmission power. In one or more example methods, this precoder scheme may be referred to as a Mode 3 precoder scheme. In other words, this precoder scheme may be indicated as an operational mode 3.

In one or more example methods, the precoder scheme may indicate that a signal is to be maximized for a certain TRP and/or that a signal is to be minimized for a certain TRP. Maximizing the signal for a certain TRP can be seen as maximizing the transmit power towards that TRP, such as towards the TRP having the best channel conditions. Minimizing the signal for a certain TRP can be seen as minimizing the transmit power, such as setting the transmit power to zero, towards that TRP, such as towards the TRP having less good channel conditions or towards a TRP not being associated with a serving radio network node of the WD. Minimizing the signal for a certain TRP, such as minimizing the transmit power towards the TRP, can in one or more example methods be seen as not transmitting the signal towards the TRP. Not transmitting the signal towards the TRP can herein be seen as minimizing an interference for the TRP. In one or more example methods, the precoder scheme may indicate that the signal is to be maximized for a first TRP, such as the TRP having the best channel conditions, and is to be minimized for a second TRP, such as the TRP having less good channel conditions or a TRP not being associated with the serving radio network node of the WD. The same precoder scheme may thus be indicated by one or more of indicating that a signal is to be maximized for a first TRP and/or a signal is to be minimized for a second TRP, by indicating that an interference is to be minimized for the second TRP, and by indicating that the power is to be maximized for the first TRP and/or the power is to be minimized for the second TRP. In one or more example methods, this precoder scheme may be referred to as a zero-forcing precoder scheme. In other words, this precoder scheme may be indicated as an zero-forcing mode or a zero-forcing operational mode. In one or more example methods, this precoder scheme may be indicated as a second mode, or second operational mode, precoder scheme.

In one or more example methods, the precoder scheme may indicate that a sum of power, such as a sum of the transmit powers at a plurality of TRPs, such as at the first TRP and at the second TRP, is to be maximized. This example precoder scheme may indicate to the WD that the WD is to select a precoder scheme which maximizes the sum of the power of the received signals at the plurality of TRPs, such as at the TRPs combined. In one or more example methods, this precoder scheme may be indicated as a third mode, or third operational mode, precoder scheme. In one or more example methods, the precoder scheme is indicative of an index of one or more transmission and reception points, TRPs, for which associated signals are to have the precoder scheme applied. The precoder scheme may for example comprise an index of the one or more TRPs, such as an identifier of the one or more TRPs, to which the precoder scheme is to be applied, such as to which TRP a signal and/or a power, such as transmit power, is to be maximized or minimized.

In one or more example methods, the method comprises receiving S205, from the radio network node, CSI-RS based on the indicated channel conditions. In one or more example methods, receiving S205 is performed upon receiving CSI-RS from the radio network node. The CSI-RS may be received from one or more TRPs associated with, such as controlled by, the radio network node. The WD may determine channel conditions of a respective channel between the WD and the one or more TRPs based on the received CSI-RS. By receiving the CSI-RS via the one or more TRPs associated with the radio network node, the WD can determine channel conditions for a respective channel between the WD and the one or more TRPs, for example to determine the channel having the best channel condition. The method 200 comprises transmitting S207, to the radio network node, SRS based on the received precoder scheme. The received precoder scheme herein refers to the precoder scheme indicated in the signal received from the radio network node. Transmitting SRS based on the received precoder scheme can herein be seen as applying a respective precoder to the SRS transmission on one or more of the channels between the WD and the radio network node, such as to one or more TRPs of the radio network node. In other words, transmitting SRS based on the received precoder scheme can be seen as transmitting precoded SRS, the SRS being precoded using the received precoder scheme. The SRS may be transmitted in response to receiving the CSI-RS.

In one or more example methods, the method comprises receiving S209, from the network node, one or more of a PDCCH and a PDSCH, based on the received precoder scheme. In one or more example methods, the radio network node may use the same precoder scheme as used for precoding the SRS for transmitting in downlink to the WD, such as on the PDSCH and/or the PDCCH.

Fig. 6 shows a block diagram of an example radio network node 400 according to the disclosure. The radio network node 400 comprises memory circuitry 401 , processor circuitry 402, and a wireless interface 403. The radio network node 400 may be configured to perform any of the methods disclosed in Fig. 4. In other words, the radio network node 400 may be configured assisting a wireless device, WD, with determining a precoder for sounding reference signal, SRS, transmission.

The radio network node 400 is configured to communicate with a user equipment, such as the user equipment node disclosed herein, using a wireless communication system.

The wireless interface 403 is configured for wireless communications via a wireless communication system, such as a 3GPP system, such as a 3GPP system supporting one or more of: New Radio, NR, Narrow-band loT, NB-loT, and Long Term Evolution - enhanced Machine Type Communication, LTE-M, millimeter-wave communications, such as millimeter-wave communications in licensed bands, such as device-to-device millimeter-wave communications in licensed bands. The radio network node 400 is configured to send, for example, via the wireless interface

403, to the WD, a signal indicative of a precoder scheme for at least one uplink transmission.

Processor circuitry 402 is optionally configured to perform any of the operations disclosed in Fig. 4 (such as any one or more of S101 , S101 A, S103, S104, S105, S107). The operations of the radio network node 400 may be embodied in the form of executable logic routines (for example, lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (for example, memory circuitry 401 ) and are executed by processor circuitry 402).

Furthermore, the operations of the radio network node 400 may be considered a method that the radio network node 400 is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may also be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and/or software.

Memory circuitry 401 may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable device. In a typical arrangement, memory circuitry 401 may include a non-volatile memory for long term data storage and a volatile memory that functions as system memory for processor circuitry 402. Memory circuitry 401 may exchange data with processor circuitry 402 over a data bus. Control lines and an address bus between memory circuitry 401 and processor circuitry 402 also may be present (not shown in Fig. 6). Memory circuitry 401 is considered a non-transitory computer readable medium.

Memory circuitry 401 may be configured to store information, such as information indicative of one or more of the precoder scheme, channel conditions and network conditions, in a part of the memory.

Fig. 7 shows a block diagram of an example wireless device 300 according to the disclosure. The wireless device 300 comprises memory circuitry 301 , processor circuitry 302, and a wireless interface 303. The wireless device 300 may be configured to perform any of the methods disclosed in Fig. 5. In other words, the wireless device 300 may be configured for determining a precoder for sounding reference signal, SRS, transmission.

The wireless device 300 is configured to communicate with a network node, such as the radio network node 400 disclosed herein, using a wireless communication system.

The wireless device 300 is configured to receive (such as via the wireless interface 303), from a radio network node, a signal indicative of a precoder scheme for at least one uplink transmission.

The wireless device 300 is configured to transmit (such as via the wireless interface 303), to the radio network node, SRS based on the received precoder scheme.

The wireless interface 303 is configured for wireless communications via a wireless communication system, such as a 3GPP system, such as a 3GPP system supporting one or more of: New Radio, NR, Narrow-band loT, NB-loT, and Long Term Evolution - enhanced Machine Type Communication, LTE-M, millimeter-wave communications, such as millimeter-wave communications in licensed bands, such as device-to-device millimeter-wave communications in licensed bands.

The wireless device 300 is optionally configured to perform any of the operations disclosed in Fig. 5 (such as any one or more of S201 , S201 A, S203, S205, S207, S209). The operations of the wireless device 300 may be embodied in the form of executable logic routines (for example, lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (for example, memory circuitry 301 ) and are executed by processor circuitry 302).

Furthermore, the operations of the wireless device 300 may be considered a method that the wireless device 300 is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may also be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and/or software.

Memory circuitry 301 may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable device. In a typical arrangement, memory circuitry 301 may include a non-volatile memory for long term data storage and a volatile memory that functions as system memory for processor circuitry 302. Memory circuitry 301 may exchange data with processor circuitry 302 over a data bus. Control lines and an address bus between memory circuitry 301 and processor circuitry 302 also may be present (not shown in Fig. 7). Memory circuitry 301 is considered a non-transitory computer readable medium.

Memory circuitry 301 may be configured to store information, such as information indicative of one or more of the precoder scheme, channel conditions and network conditions, in a part of the memory.

Examples of methods and products (radio network node and wireless device) according to the disclosure are set out in the following items:

Item 1 . A method performed by a radio network node, for assisting a wireless device, WD, with determining a precoder for sounding reference signal, SRS, transmission, the method comprising:

- sending (S105), to the WD, a signal indicative of a precoder scheme for at least one uplink transmission.

Item 2. The method according to Item 1 , wherein the precoder scheme is indicated by an operational mode for the at least one uplink transmission.

Item 3. The method according to any one of the previous Items, wherein the precoder scheme is indicative of one or more of a power threshold, an interference threshold, and an operational threshold to be applied to an uplink channel.

Item 4. The method according to any one of the previous Items, wherein the precoder scheme is indicative of one or more of a power to be maximized, a power to be minimized, a signal to be minimized, a signal to be maximized, a sum of power to be maximized, and an interference to be minimized.

Item 5. The method according to any one of the previous Items, wherein the precoder scheme is indicative of an index of one or more transmission and reception points, TRPs, for which associated signals are to have the precoder scheme applied.

Item 6. The method according to any of the previous Items, wherein the sending (S105) is performed upon transmitting Channel State Information-Reference Signals, CSI-RS, to the WD.

Item 7. The method according to any one of the previous Items, wherein the method comprises:

- obtaining (S101 ) an indication indicative of a channel condition between the WD and one or more transmission points of the radio network node.

Item 8. The method according to Item 7, wherein the obtaining (S101) comprises receiving (S101 A) a pilot signal from the WD.

Item 9. The method according to Item 8, wherein the pilot signal is a non-precoded SRS.

Item 10. The method according to any one of the Items 7 to 9, wherein the method comprises:

- transmitting (S103) CSI-RS based on the indicated channel condition.

Item 11 . The method according to any one of the previous Items, wherein the method comprises: determining (S104), based on network conditions, the precoder scheme for at least one uplink transmission.

Item 12. The method according to any one of the Items 1 -11 , wherein the method comprises transmitting (S107), to the WD, one or more of a Physical Downlink Control Channel, PDCCH, and a Physical Downlink Shared Channel, PDSCH, based on the indicated precoder scheme.

Item 13. The method according to any one of the previous claims, wherein the method comprises: receiving (S109), from the WD, SRS based on the indicated precoder scheme.

Item 14. A method performed by a wireless device, WD, for determining a precoder for sounding reference signal, SRS, transmission, the method comprising:

- receiving (S203), from a radio network node, a signal indicative of a precoder scheme for at least one uplink transmission, and

- transmitting (S207), to the radio network node, SRS based on the received precoder scheme.

Item 15. The method according to Item 14, wherein the precoder scheme is indicated by an operational mode for the at least one uplink transmission.

Item 16. The method according to any one of the Items 14 to 15, wherein the precoder scheme is indicative of one or more of a power threshold, an interference threshold, and an operational threshold to be applied to an uplink channel.

Item 17. The method according to any one of the Items 14 to 16, wherein the precoder scheme is indicative of one or more of a power to be maximized, a power to be minimized, a signal to be minimized, a signal to be maximized, a sum of power to be maximized, and an interference to be minimized.

Item 18. The method according to any one of the Items 14 to 17, wherein the precoder scheme is indicative of an index of one or more transmission and reception points, TRPs, for which associated signals are to have the precoder scheme applied.

Item 19. The method according to any of the Items 14 to 18, wherein receiving (S205) is performed in response to receiving Channel State Information-Reference Signals, CSI-RS, from the radio network node.

Item 20. The method according to any one of the Items 14 to 19, wherein the method comprises: providing (S201 ), to the radio network node, an indication indicative of a channel condition between the WD and one or more transmission and reception points, TRPs, of the radio network node.

Item 21 . The method according to Item 20, wherein providing (S201) comprises transmitting (S201 A) a pilot signal to the radio network node.

Item 22. The method according to Item 21 , wherein the pilot signal is a non-precoded SRS.

Item 23. The method according to any one of the Items 20 to 22, wherein the method comprises: receiving (S205), from the radio network node, Channel State Information- Reference Signals, CSI-RS, based on the indicated channel conditions.

Item 24. The method according to any one of the Items 14 to 23, wherein the method comprises: receiving (S209), from the network node, one or more of a Physical Downlink Control Channel, PDCCH, and a Physical Downlink Shared Channel, PDSCH, based on the received precoder scheme.

Item 25. A radio network node comprising memory circuitry, processor circuitry, and a wireless interface, wherein the radio network node is configured to perform any of the methods according to any of Items 1 -13.

Item 26. A wireless device comprising memory circuitry, processor circuitry, and a wireless interface, wherein the wireless device is configured to perform any of the methods according to any of Items 14-24.

The use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. does not imply any particular order, but are included to identify individual elements. Moreover, the use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. does not denote any order or importance, but rather the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. are used to distinguish one element from another. Note that the words “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. are used here and elsewhere for labelling purposes only and are not intended to denote any specific spatial or temporal ordering. Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

It may be appreciated that Figures 1 to 7 comprise some circuitries or operations which are illustrated with a solid line and some circuitries, components, features, or operations which are illustrated with a dashed line. Circuitries or operations which are comprised in a solid line are circuitries, components, features or operations which are comprised in the broadest example. Circuitries, components, features, or operations which are comprised in a dashed line are examples which may be comprised in, or a part of, or are further circuitries, components, features, or operations which may be taken in addition to circuitries, components, features, or operations of the solid line examples. It should be appreciated that these operations need not be performed in order presented. Furthermore, it should be appreciated that not all of the operations need to be performed. The example operations may be performed in any order and in any combination. It should be appreciated that these operations need not be performed in order presented. Circuitries, components, features, or operations which are comprised in a dashed line may be considered optional.

Other operations that are not described herein can be incorporated in the example operations. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the described operations.

Certain features discussed above as separate implementations can also be implemented in combination as a single implementation. Conversely, features described as a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can, in some cases, be excised from the combination, and the combination may be claimed as any subcombination or variation of any sub-combination

It is to be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed. It is to be noted that the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements.

It should further be noted that any reference signs do not limit the scope of the claims, that the examples may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware.

Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than or equal to 10% of, within less than or equal to 5% of, within less than or equal to 1% of, within less than or equal to 0.1% of, and within less than or equal to 0.01% of the stated amount. If the stated amount is 0 (e.g., none, having no), the above recited ranges can be specific ranges, and not within a particular % of the value. For example, within less than or equal to 10 wt./vol. % of, within less than or equal to 5 wt./vol. % of, within less than or equal to 1 wt./vol. % of, within less than or equal to 0.1 wt./vol. % of, and within less than or equal to 0.01 wt./vol. % of the stated amount.

The various example methods, devices, nodes and systems described herein are described in the general context of method steps or processes, which may be implemented in one aspect by a computer program product, embodied in a computer- readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program circuitries may include routines, programs, objects, components, data structures, etc. that perform specified tasks or implement specific abstract data types. Computer-executable instructions, associated data structures, and program circuitries represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes. Although features have been shown and described, it will be understood that they are not intended to limit the claimed disclosure, and it will be made obvious to those skilled in the art that various changes and modifications may be made without departing from the scope of the claimed disclosure. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed disclosure is intended to cover all alternatives, modifications, and equivalents.

Claims

1 . A method performed by a radio network node, for assisting a wireless device, WD, with determining a precoder for sounding reference signal, SRS, transmission, the method comprising:

2. The method according to claim 1 , wherein the precoder scheme is indicated by an operational mode for the at least one uplink transmission.

3. The method according to any one of the previous claims, wherein the precoder scheme is indicative of one or more of a power threshold, an interference threshold, and an operational threshold to be applied to an uplink channel.

4. The method according to any one of the previous claims, wherein the precoder scheme is indicative of one or more of a power to be maximized, a power to be minimized, a signal to be minimized, a signal to be maximized, a sum of power to be maximized, and an interference to be minimized.

5. The method according to any one of the previous claims, wherein the precoder scheme is indicative of an index of one or more transmission and reception points, TRPs, for which associated signals are to have the precoder scheme applied.

6. The method according to any one of the previous claims, wherein the sending (S105) is performed upon transmitting Channel State Information-Reference Signals, CSI-RS, to the WD.

7. The method according to any one of the previous claims, wherein the method comprises:

8. The method according to claim 7, wherein the obtaining (S101 ) comprises receiving (S101 A) a pilot signal from the WD.

9. The method according to claim 8, wherein the pilot signal is a non-precoded SRS.

10. The method according to any one of claims 7 to 9, wherein the method comprises:

- transmitting (S103) Channel State Information-Reference Signals, CSI-RS, based on the indicated channel condition.

11 . The method according to any one of the previous claims, wherein the method comprises: determining (S104), based on network conditions, the precoder scheme for at least one uplink transmission.

12. The method according to any one of the previous claims, wherein the method comprises transmitting (S107), to the WD, one or more of a Physical Downlink Control Channel, PDCCH, and a Physical Downlink Shared Channel, PDSCH, based on the received precoder scheme.

13. The method according to any one of the previous claims, wherein the method comprises:

- receiving (S109), from the WD, SRS based on the indicated precoder scheme.

14. A method performed by a wireless device, WD, for determining a precoder for sounding reference signal, SRS, transmission, the method comprising:

- transmitting (S207), to the radio network node, SRS based on the indicated precoder scheme.

15. The method according to claim 14, wherein the precoder scheme is indicated by an operational mode for the at least one uplink transmission. The method according to any one of the claims 14 to 15, wherein the precoder scheme is indicative of one or more of a power threshold, an interference threshold, and an operational threshold to be applied to an uplink channel. The method according to any one of the claims 14 to 16, wherein the precoder scheme is indicative of one or more of a power to be maximized, a power to be minimized, a signal to be minimized, a signal to be maximized, a sum of power to be maximized, and an interference to be minimized. The method according to any one of the claims 14 to 17, wherein the precoder scheme is indicative of an index of one or more transmission and reception points, TRPs, for which associated signals are to have the precoder scheme applied. The method according to any of the claims 14 to 18, wherein receiving (S205) is performed in response to receiving Channel State Information -Reference Signals, CSI-RS, from the radio network node. The method according to any one of the claims 14 to 19, wherein the method comprises:

- providing (S201 ), to the radio network node, an indication indicative of a channel condition between the WD and one or more transmission and reception points, TRPs, of the radio network node. The method according to claim 20, wherein providing (S201 ) comprises transmitting (S201 A) a pilot signal to the radio network node. The method according to claim 21 , wherein the pilot signal is a non-precoded SRS. The method according to any one of the claims 20 to 22, wherein the method comprises: receiving (S205), from the radio network node, Channel State Information- Reference Signals, CSI-RS, based on the indicated channel conditions. The method according to any one of the claims 14 to 23, wherein the method comprises: receiving (S209), from the network node, one or more of a Physical Downlink Control Channel, PDCCH, and a Physical Downlink Shared Channel, PDSCH, based on the received precoder scheme. A radio network node comprising memory circuitry, processor circuitry, and a wireless interface, wherein the radio network node is configured to perform any of the methods according to any of claims 1-13. A wireless device comprising memory circuitry, processor circuitry, and a wireless interface, wherein the wireless device is configured to perform any of the methods according to any of claims 14-24.