Wireless devices and methods therein for handling transmissions between the devices over a direct device-to-device (D2D) communication link

1. A method performed by a first wireless device for handling beamformed transmissions between the first wireless device and at least one second wireless device over a direct device-to-device, D2D, communication link, the method comprising

transmitting a radio signal towards the at least one second wireless device indicating that the first wireless device is, or that the at least one second wireless device has an option to be, responsible for beamforming of transmissions over the direct D2D communication link;

receiving information from the at least one second wireless device indicating which of the first wireless device or the at least one second wireless device is to be responsible for beamforming of transmissions over the direct D2D communication link; and

configuring, based on the received information, which of the first wireless device or the at least one second wireless device is to be responsible for beamforming of transmissions over the direct D2D communication link.

2. The method according to claim 1 , further comprising

performing beamformed transmissions towards the at least one second wireless device over the direct D2D communication link based on the configuration.

3. The method according to claim 1 , wherein transmitting the radio signal in an initial set of wide beams over the direct D2D communication link indicates to the at least one second wireless device that the first wireless device is to be responsible for the beamforming of transmissions over the direct D2D communication link.

4. The method according to claim 3 , wherein the received information from the at least one second wireless device comprises a measurement report on the received signal strength on the initial set of wide beams transmitted from the first wireless device, said measurement report indicating to the first wireless device that the first wireless device is to be responsible for the beamforming of transmissions over the direct D2D communication link, and wherein the configuring comprises configuring the initial set of wide beams for the direct D2D communication link based on the received measurement report from the at least one second wireless device.

5. The method according to claim 1 , wherein the transmitted radio signal comprises a request for the at least one second wireless device to be responsible for the beamforming of transmissions over the direct D2D communication link.

6. The method according to claim 5 , wherein the request further comprises wide-beam characteristics or narrow-beam characteristics indicating absolute or relative directions of one or more antennas of the first wireless device in respect of the current movement direction of at least one second wireless device.

7. The method according to claim 5 , wherein the received information from the at least one second wireless device comprises an acknowledgement (ACK) or non-acknowledgement (NACK) of the request for the at least one second wireless device to be responsible for beamforming of transmissions over the direct D2D communication link.

8. The method according to claim 1 , wherein the transmitted radio signal comprises an indication that no subsequent narrow beam refinement is required in the beamforming of transmissions between the first wireless device and the at least one second wireless device over the direct D2D communication.

9. A first wireless device for handling beamformed transmissions between the first wireless device and at least one second wireless device over a direct device-to-device, D2D, communication link, the first wireless device comprising a processor and a memory, wherein the memory is containing instructions executable by the processor, causing the first wireless device to:

transmit a radio signal towards the at least one second wireless device indicating that the first wireless device is, or that the at least one second wireless device has an option to be, responsible for beamforming of transmissions over the direct D2D communication link,

receive information from the at least one second wireless device indicating which of the first wireless device or the at least one second wireless device is to be responsible for beamforming of transmissions over the direct D2D communication link, and

configure, based on the received information, which of the first wireless device or the at least one second wireless device is to be responsible for beamforming of transmissions over the direct D2D communication link.

10. The first wireless device according to claim 9 , further configured to perform beamformed transmissions towards the at least one second wireless device over the direct D2D communication link based on the configuration.

11. A method performed by a second wireless device for handling beamformed transmissions between the second wireless device and a first wireless device over a direct device-to-device, D2D, communication link, the method comprising

receiving a radio signal from the first wireless device indicating that the first wireless device is, or that the second wireless device has an option to be, responsible for beamforming of transmissions over the direct D2D communication link;

determining which of the first wireless device or the second wireless device is to be responsible for beamforming of transmissions over the direct D2D communication link; and

transmitting information to the first wireless device indicating which of the first wireless device or the second wireless device is to be responsible for beamforming of transmissions over the direct D2D communication link.

12. The method according to claim 11 , further comprising

performing beamformed transmissions towards the first wireless device over the direct D2D communication link.

13. The method according to claim 11 , wherein receiving the radio signal in an initial set of wide beams over the direct D2D communication link indicates to the second wireless device that the first wireless device is to be responsible for the beamforming of transmissions over the direct D2D communication link.

14. The method according to claim 12 , wherein the determining further comprises measuring the received signal strengths on the initial set of wide beams, and the transmitting further comprises transmitting information comprising a measurement report on the received signal strengths of the radio signal on the initial set of wide beams, wherein the measurement report indicates to the first wireless device that the first wireless device ( 121 ) is to be responsible for the beamforming of transmissions over the direct D2D communication link.

15. The method according to claim 11 , wherein the received radio signal comprises a request for the second wireless device to be responsible for the beamforming of transmissions over the direct D2D communication link.

16. The method according to claim 15 , wherein the request further comprises wide-beam characteristics or narrow-beam characteristics indicating absolute or relative directions of one or more antennas of the first wireless device in respect of the current movement direction of the second wireless device.

17. The method according to claim 15 , wherein the transmitted information comprise an acknowledgement (ACK) of the request if the second wireless device has determined that it is to be responsible for beamforming of transmissions over the direct D2D communication link, or a non-acknowledgement (NACK) of the request if the second wireless device has determined that it is not to be responsible for beamforming of transmissions over the direct D2D communication link.

18. The method according to claim 11 , wherein the received radio signal comprises an indication that no subsequent narrow beam refinement is required in the beamforming of transmissions between the second wireless device and the first wireless device over the direct D2D communication.

19. A second wireless device for handling beamformed transmissions between the second wireless device and a first wireless device over a direct device-to-device, D2D, communication link, the second wireless device comprising a processor and a memory, wherein the memory is containing instructions executable by the processor, causing the second wireless device to

receive a radio signal from the first wireless device indicating that the first wireless device is, or that the second wireless device has an option to be, responsible for beamforming of transmissions over the direct D2D communication link,

determine which of the first wireless device or the second wireless device is to be responsible for beamforming of transmissions over the direct D2D communication link, and

transmit information to the first wireless device indicating which of the first wireless device or the second wireless device is to be responsible for beamforming of transmissions over the direct D2D communication link.

20. The second wireless device according to claim 19 , further configured to perform beamformed transmissions towards the first wireless device over the direct D2D communication link.