Method and apparatus for control information transmission

1. A method for control information transmission at a first communications device configured to utilize both a licensed spectrum and an unlicensed spectrum, the control information for controlling data transmission, comprising:

checking whether there is a granted resource on a licensed carrier of the licensed spectrum to transmit the control information to a second communications device that is also configured to utilize both the licensed spectrum and the unlicensed spectrum;

if there is a granted resource on the licensed carrier, then transmitting the control information via the granted resource on the licensed carrier to the second communications device;

checking whether there is a granted resource on an unlicensed carrier of the unlicensed spectrum to transmit the control information, if there is no granted resource on the licensed carrier to transmit the control information; and

if there is a granted resource on the unlicensed carrier, then transmitting the control information via the granted resource on the unlicensed carrier to the second communications device, instead of on the licensed carrier.

2. The method according to claim 1 , wherein the transmitting of the control information via the granted resource on the unlicensed carrier further comprises:

maintaining a copy of the control information;

checking whether the granted resource on the unlicensed carrier is exclusively occupied by the first communications device; and

if the granted resource is exclusively occupied by the first communications device, then transmitting the control information via the granted resource on the unlicensed carrier to the second communications device.

3. The method according to claim 2 , wherein the copy of the control information is maintained at a Media Access Control (MAC) layer.

4. The method according to claim 2 , further comprising:

checking whether an acknowledgement is received from the second communications device in response to the control information that is transmitted via the granted resource on the unlicensed carrier; and

when the acknowledgement is not received from the second communications device:

if there is a granted resource on the licensed carrier, then retransmitting the control information via the granted resource on the licensed carrier to the second communications device using the copy of the control information; otherwise

checking whether there is a granted resource on another unlicensed carrier of the unlicensed spectrum; and

if there is a granted resource on the other unlicensed carrier, then retransmitting the control information via the granted resource on the other unlicensed carrier to the second communications device using the copy of the control information.

5. The method according to claim 4 , wherein

the maintaining the copy of the control information further comprises updating the copy of the control information, and

the retransmitting of the copy of the control information comprises transmission of the updated copy of the control information.

6. The method according to claim 4 , wherein the retransmitting of the copy of the control information is performed after a predetermined time period elapses since a previous transmission of the control information.

7. The method according to claim 2 , further comprising discarding the copy of the control information in response that an acknowledgement is received from the second communications device or in response that the copy has been maintained over a predetermined time period.

8. The method according to claim 1 , wherein

the first communications device is a terminal device and the second communications device is a base station; and

the granted resource is indicated by an uplink grant transmitted from the second communications device to the first communications device.

9. The method according to claim 1 , wherein the first communications device is a base station and the second communications device is a terminal device.

10. An apparatus for control information transmission at a first communications device configured to utilize both a licensed spectrum and an unlicensed spectrum, the control information for controlling data transmission comprising:

a processor and a non-transitory computer readable storage medium, the non-transitory computer readable storage medium containing instructions, which when executed by the processor, cause the apparatus to:

check whether there is a granted resource on a licensed carrier of the licensed spectrum to transmit the control information to a second communications device that is also configured to utilize both the licensed spectrum and the unlicensed spectrum;

transmit the control information, if there is a granted resource on the licensed carrier, via the granted resource on the licensed carrier to the second communications device;

check whether there is a granted resource on an unlicensed carrier of the unlicensed spectrum to transmit the control information, if there is no granted resource on the licensed carrier to transmit the control information; and

transmit the control information, if there is a granted resource on the unlicensed carrier, via the granted resource on the unlicensed carrier to the second communications device, instead of on the licensed carrier.

11. The apparatus according to claim 10 , wherein the instructions, which when executed by the processor, further cause the apparatus to:

maintain a copy of the control information;

check whether the granted resource on the unlicensed carrier is exclusively occupied by the first communications device; and

transmit the control information, if the granted resource is exclusively occupied by the first communications device, via the granted resource on the unlicensed carrier to the second communications device.

12. The apparatus according to claim 11 , wherein the copy of the control information is maintained at a Media Access Control (MAC) layer.

13. The apparatus according to claim 11 , wherein the instructions, which when executed by the processor, further cause the apparatus to:

check whether an acknowledgement is received from the second communications device in response to the control information that is transmitted via the granted resource on the unlicensed carrier; and

when the acknowledgement is not received from the second communication device:

retransmit the control information, if there is a granted resource on the licensed carrier, via the granted resource on the licensed carrier to the second communications device using the copy of the control information; otherwise

check whether there is a granted resource on another unlicensed carrier of the unlicensed spectrum, if there is no granted resource on the licensed carrier; and

retransmit the control information, if there is a granted resource on the other unlicensed carrier, via the granted resource on the other unlicensed carrier to the second communications device using the copy of the control information.

14. The apparatus according to claim 13 , wherein the instructions, which when executed by the processor, further cause the apparatus to:

update the copy of the control information, and

retransmit the copy of the control information by transmission of the updated copy of the control information.

15. The apparatus according to claim 13 , wherein the retransmit of the copy of the control information is performed after a predetermined time period elapses since a previous transmission of the control information.

16. The apparatus according to claim 11 , wherein the instructions, which when executed by the processor, further cause the apparatus to:

discard the copy of the control information in response that an acknowledgement is received from the second communications device or in response that the copy has been maintained over a predetermined time period.

17. The apparatus according to claim 10 , wherein

the first communications device is a terminal device and the second communications device is a base station; and

the granted resource is indicated by an uplink grant transmitted from the second communications device to the first communications device.

18. The apparatus according to claim 10 , wherein the first communications device is a base station and the second communications device is a terminal device.

19. A non-transitory computer readable storage medium containing instructions which, when executed by a processor in a first communication device configured to utilize both a licensed spectrum and an unlicensed spectrum, cause control information transmission, wherein the control information is for controlling data transmission, by performing operations comprising:

checking whether there is a granted resource on a licensed carrier of the licensed spectrum to transmit the control information to a second communications device that is also configured to utilize both the licensed spectrum and the unlicensed spectrum;

if there is a granted resource on the licensed carrier, then transmitting the control information via the granted resource on the licensed carrier to the second communications device;

checking whether there is a granted resource on an unlicensed carrier of the unlicensed spectrum to transmit the control information, if there is no granted resource on the licensed carrier to transmit the control information; and

if there is a granted resource on the unlicensed carrier, then transmitting the control information via the granted resource on the unlicensed carrier to the second communications device, instead of on the licensed carrier.

20. The non-transitory computer readable storage medium according to claim 19 , wherein the transmitting of the control information via the granted resource on the unlicensed carrier further comprises:

maintaining a copy of the control information;

checking whether the granted resource on the unlicensed carrier is exclusively occupied by the first communications device; and

if the granted resource is exclusively occupied by the first communications device, then transmitting the control information via the granted resource on the unlicensed carrier to the second communications device.

21. The non-transitory computer readable storage medium according to claim 20 , wherein the copy of the control information is maintained at a Media Access Control (MAC) layer.

22. The non-transitory computer readable storage medium according to claim 20 , wherein the instructions further cause the performing of operations comprising:

checking whether an acknowledgement is received from the second communications device in response to the control information that is transmitted via the granted resource on the unlicensed carrier; and

when the acknowledgement is not received from the second communications device:

if there is a granted resource on the licensed carrier, then retransmitting the control information via the granted resource on the licensed carrier to the second communications device using the copy of the control information; otherwise

checking whether there is a granted resource on another unlicensed carrier of the unlicensed spectrum; and

if there is a granted resource on the other unlicensed carrier, then retransmitting the control information via the granted resource on the other unlicensed carrier to the second communications device using the copy of the control information.

23. The non-transitory computer readable storage medium according to claim 22 , wherein

the maintaining the copy of the control information further comprises updating the copy of the control information, and

the retransmitting of the copy of the control information comprises transmission of the updated copy of the control information.

24. The non-transitory computer readable storage medium according to claim 22 , wherein the retransmitting of the copy of the control information is performed after a predetermined time period elapses since a previous transmission of the control information.

25. The non-transitory computer readable storage medium according to claim 20 , further comprising discarding the copy of the control information in response that an acknowledgement is received from the communications device or in response that the copy has been maintained over a second predetermined time period.

26. The non-transitory computer readable storage medium according to claim 19 , wherein

the first communications device is a terminal device and the second communications device is a base station; and

the granted resource is indicated by an uplink grant transmitted from the second communications device to the first communications device.

27. The non-transitory computer readable storage medium according to claim 19 , wherein the first communications device is a base station and the second communications device is a terminal device.