Wireless device and power control method

1. A power control method, in a cluster comprised of wireless devices including a first wireless device, a second wireless device and a third wireless device, the method comprising:

receiving, at the first wireless device, power control information including a second data channel transmission power of the second wireless device, from the second wireless device, wherein the second wireless device is a cluster head communicable with other wireless devices including the first and third wireless devices; and

determining, at the first wireless device, a first data channel transmission power of the first wireless device at which to perform communication between the first wireless device and the third wireless device, based on a transmission path loss between the first wireless device and the second wireless device.

2. The power control method according to claim 1 , wherein

the transmission path loss between the first wireless device and the second wireless device is determined based on a reference signal reception power measured at the first wireless device and the second data channel transmission power of the second wireless device, which is a reference signal transmission power of the second wireless device.

3. The power control method according to claim 1 , wherein power control of a control channel is independently performed from that of the first data channel.

4. The power control method according to claim 1 , wherein the second data channel transmission power is determined from a minimum value between a reference signal reception power measured at the first wireless device and a reference signal reception power measured at the third wireless device, a reference signal transmission power of the second wireless device, and a minimum signal reception power common to all the wireless devices in the cluster.

5. The power control method according to claim 1 , wherein the second data channel transmission power is determined from a reference signal reception power measured at the second wireless device, a reference signal transmission power of the first wireless device, and a minimum signal reception power common to all the wireless devices in the cluster.

6. The power control method according to claim 5 , wherein the second data channel transmission power is determined from a minimum value between the reference signal reception power measured at the second wireless device and a reference signal reception power measured at the third wireless device, the reference signal transmission power of the first wireless device, and the minimum signal reception power common to all the wireless devices in the cluster.

7. The power control method according to claim 1 , wherein the first and third wireless devices perform device-to-device (D2D) communication.

8. A first wireless device comprising:

a receiver which, in operation, receives power control information including a second data channel transmission power of a second wireless device, from the second wireless device, wherein the second wireless device is a cluster head communicable with other wireless devices including the first wireless device and a third wireless device; and

a controller which, in operation, determines a first data channel transmission power of the first wireless device at which to perform communication between the first wireless device and the third wireless device, based on a transmission path loss between the first wireless device and the second wireless device.

9. The first wireless device according to claim 8 , wherein

the controller, in operation, determines the transmission path loss between the first wireless device and the second wireless device based on a reference signal reception power measured at the first wireless device and the second data channel transmission power of the second wireless device, which is a reference signal transmission power of the second wireless device.

10. The first wireless device according to claim 8 , wherein

the controller performs power control of a control channel independently from that of the first data channel.

11. The first wireless device according to claim 8 , wherein the second data channel transmission power is determined from a minimum value between a reference signal reception power measured at the first wireless device and a reference signal reception power measured at the third wireless device, a reference signal transmission power of the second wireless device, and a minimum signal reception power common to all the wireless devices in the cluster.

12. The first wireless device according to claim 8 , wherein the second data channel transmission power is determined from a reference signal reception power measured at the second wireless device, a reference signal transmission power of the first wireless device, and a minimum signal reception power common to all the wireless devices in the cluster.

13. The first wireless device according to claim 12 , wherein the second data channel transmission power is determined from a minimum value between the reference signal reception power measured at the second wireless device and a reference signal reception power measured at the third wireless device, the reference signal transmission power of the first wireless device, and the minimum signal reception power common to all the wireless devices in the cluster.

14. The first wireless device according to claim 8 , which, in operation, performs device-to-device (D2D) communication with the third wireless device.