Methods and devices for communications in device-to-device networks

1. A wireless device comprising:

a selection processor configured to process selection information to set a duration of a selection period and to start the selection period;

a receiver configured to receive a synchronization initiation signal; and

a transmitter configured to transmit a synchronization initiation signal after the selection period has expired if the receiver has not received a synchronization initiation signal during the selection period;

wherein the selection information corresponds to at least one selection factor for the wireless device and/or to at least one selection factor weighted for the wireless device; and

wherein the at least one selection factor relates to a type of a source for time synchronization that the wireless device is capable of using; or wherein the at least one selection factor is indicative of a quality of a source for time synchronization that the wireless device is capable of using; or wherein the at least one selection factor is indicative of a distance between the wireless device and

a master wireless device from which the wireless device has received synchronization signals and wherein a value is employed for the at least one selection factor depending on a magnitude of the relative distance; or wherein the at least one selection factor is indicative of a transmission power capability of the wireless device for transmitting periodic synchronization signals; or wherein the at least one selection factor is indicative of a battery level of the wireless device.

2. The wireless device according to claim 1 , wherein the type of the source for time synchronization indicates the source to be either a satellite-based synchronization source or an internal clock of the wireless device, and wherein the at least one selection factor is weighted for the wireless device depending on the type of the source.

3. The wireless device of claim 1 , wherein the source for time synchronization is a satellite-based synchronization source and the quality of the source for time synchronization corresponds to reception quality of a signal from the satellite-based synchronization source at the wireless device.

4. The wireless device of claim 1 , wherein the source for time synchronization is an internal clock of the wireless device and the quality of the source for time synchronization corresponds to an accuracy of the internal clock.

5. The wireless device of claim 1 , wherein a weight value is assigned to the at least one selection factor to yield a weighted selection factor, the weight value being indicative of a relative importance between the at least one selection factor compared to at least one further selection factor.

6. The wireless device of claim 1 , wherein the selection period is a selection period for selecting one of a group of candidate wireless devices including the wireless device to become a synchronization master device for broadcasting periodic synchronization signals.

7. The wireless device of claim 1 , wherein the receiver is configured to receive a synchronization initiation signal from a further wireless device during the selection period.

8. The wireless device of claim 7 , wherein the selection processor is configured to adjust to the further wireless device as source of periodic synchronization signals if the receiver receives a synchronization initiation signal during the selection period.

9. The wireless device of claim 1 , wherein the transmitter is configured not to transmit a synchronization initiation signal if the receiver receives a synchronization initiation signal during the selection period.

10. The wireless device of claim 1 , wherein the selection processor is configured to end the selection period when the receiver receives a synchronization initiation signal during the selection period.

11. The wireless device of claim 1 , wherein the selection processor is configured to start the selection period after the receiver has received a message from a further wireless device for starting the selection period.

12. The wireless device of claim 1 , wherein the receiver is configured to receive a periodic synchronization signal and wherein the transmitter is configured to broadcast a message for starting the selection period if a received strength of the periodic synchronization signal is below a predefined threshold.

13. The wireless device of claim 12 , wherein the selection processor is configured to start the selection period after the transmitter has broadcasted the message for initiating the selection period.

14. A wireless device comprising:

a selection processor configured to set a duration of a selection period based on process selection information and to start the selection period;

a receiver configured to receive a synchronization initiation signal; and

a transmitter configured to transmit a synchronization initiation signal after the selection period has expired if the receiver has not received a synchronization initiation signal during the selection period;

wherein the synchronization initiation signal is an indication that wireless device is a synchronization master and that one or more other devices should synchronize to the wireless device for device to device communications;

wherein the selection information corresponds to at least one selection factor for the wireless device and/or to at least one selection factor weighted for the wireless device; and

wherein the at least one selection factor relates to a type of a source for time synchronization that the wireless device is capable of using or wherein the at least one selection factor is indicative of a distance between the wireless device and a master wireless device from which the wireless device has received synchronization signals and wherein a value is employed for the at least one selection factor depending on a magnitude of the relative distance.