Wireless device, radio network node, methods performed therein

1. A method performed by a wireless device for transmitting an uplink reference signal to a radio network node in a wireless communication network, the method comprising:

determining whether or not a condition for using beamforming for transmission of the uplink reference signal is fulfilled, wherein the determining comprises deeming the condition to be fulfilled responsive to determining that a received signal strength or quality of a received signal from the radio network node is below a defined threshold; and

triggering the use of beamforming by the wireless device, for transmitting the uplink reference signal to the radio network node in a beamformed manner, in response to determining that the condition is fulfilled.

2. The method according to claim 1 , wherein the received signal is at least one of: a synchronisation signal, a common reference signal, and a downlink payload.

3. The method according to claim 1 , further comprising transmitting an indication to the radio network node indicating that the wireless device will beamform the uplink reference signal.

4. The method according to claim 1 , further comprising:

transmitting the uplink reference signal a number of times using different precoders;

receiving a response from the radio network node indicating a preferred precoder out of the different precoders; and

wherein transmitting the uplink reference signal to the radio network node in a beamformed manner comprises transmitting the uplink reference signal to the radio network node using the preferred precoder.

5. The method according to claim 1 , further comprising:

transmitting the uplink reference signal without using a precoder;

receiving a response from the radio network node indicating a preferred precoder; and

wherein transmitting the uplink reference signal to the radio network node in a beamformed manner comprises using the preferred precoder to beamform the transmission.

6. The method according to claim 1 , further comprising

transmitting the uplink reference signal a number of times using different precoders over different parts of a frequency spectrum;

receiving a response from the radio network node indicating a preferred precoder out of the different precoders; and

wherein transmitting the uplink reference signal to the radio network node in a beamformed manner comprises using the preferred precoder to beamform the transmission.

7. The method according to claim 1 , further comprising:

selecting a precoder to beamform the uplink reference signal; and

wherein transmitting the uplink reference signal to the radio network node in a beamformed manner comprises using the selected precoder.

8. The method according to claim 7 , wherein the selecting of the precoder includes selecting the precoder to use from among a number of possible precoders in consideration of at least one of: a previous precoder selection by the wireless device, an angle of arrival of a signal received from the radio network node, and, at least in cases where the wireless device has an active uplink session, which precoder is used for Demodulation Reference Signal (DMRS) transmission.

9. A wireless device configured for operation in a wireless communication network and comprising:

a radio receiver and transmitter for receiving signals from the wireless communication network and transmitting signals to the wireless communication network; and

processing circuitry operatively associated with the radio receiver and transmitter and configured to:

determine whether or not a condition to use beamforming for transmitting an uplink reference signal to a radio network node is fulfilled, wherein the radio network node uses the uplink reference signal for estimating a channel from the wireless device; and

trigger the use of beamforming by the wireless device, for transmitting the uplink reference signal to the radio network node in a beamformed manner, in response to determining that the condition is fulfilled;

wherein the processing circuitry is configured to deem the condition to be fulfilled in response to determining that a received signal strength or quality of a received signal from the radio network node is below a defined threshold.

10. The wireless device according to claim 9 , wherein the received signal is at least one of: a synchronisation signal, a common reference signal, and a downlink payload.

11. The wireless device according to claim 9 , wherein the processing circuitry is configured to transmit an indication to the radio network node, indicating that the wireless device will beamform the uplink reference signal.

12. The wireless device according to claim 9 , wherein the processing circuitry is configured to:

transmit the uplink reference signal a number of times using different precoders;

receive a response from the radio network node indicating a preferred precoder out of the different precoders; and

use the preferred precoder for transmitting the uplink reference signal to the radio network node in a beamformed manner.

13. The wireless device according to claim 9 , wherein the processing circuitry is configured to:

transmit the uplink reference signal without using a precoder;

receive a response from the radio network node indicating a preferred precoder; and

use the preferred precoder for transmitting the uplink reference signal to the radio network node in a beamformed manner.

14. The wireless device according to claim 9 , wherein the processing circuitry is configured to:

transmit the uplink reference signal a number of times using different precoders over different parts of a frequency spectrum;

receive a response from the radio network node indicating a preferred precoder out of the different precoders; and

use the preferred precoder for transmitting the uplink reference signal to the radio network node in a beamformed manner.

15. The wireless device according to claim 9 , wherein the processing circuitry is configured to:

select a precoder to beamform the uplink reference signal; and

use the selected precoder for transmitting the uplink reference signal to the radio network node in a beamformed manner.

16. The wireless device according to claim 15 , wherein the processing circuitry is configured to select the precoder to use from among a number of possible precoders in consideration of at least one of: a previous precoder selection by the wireless device, an angle of arrival of a signal received from the radio network node, and, at least in cases where the wireless device has an active uplink session, which precoder is used for Demodulation Reference Signal (DMRS) transmission.