Device-to-device (D2D) resource release

1. A method, comprising:

transmitting to a network node, by a user equipment, at least one proximity service buffer status report for device-to-device communication mode 1 , wherein resources for the user equipment are scheduled based on the at least one proximity service buffer status report; and

indicating, to the network node, an early release of the resources allocated to the user equipment based on the at least one proximity service buffer status report, when the resources allocated to the user equipment apply to delay tolerant data or low priority data; and

keeping the resources allocated at the user equipment when the resources are used for delay critical or high priority data.

2. The method as recited in claim 1 , wherein the early release is indicated using a physical uplink control channel format 1 resource with multiple occurrences during an allocation period.

3. The method as recited in claim 1 , wherein the early release is indicated by transmitting at least one proximity service buffer status report using physical uplink shared channel.

4. The method as recited in claim 1 , wherein the user equipment is configured with a periodic proximity service buffer status report expiry timer such that the proximity service buffer status report is triggered with constant intervals during an allocation period.

5. The method as recited in claim 1 , wherein the indication of the early release of resources is transmitted using a padding buffer status report to indicate last transmission during an allocation period.

6. The method as recited in claim 1 , wherein the proximity service buffer status report is triggered by a polling from the network node with an allocation of physical uplink shared channel resources.

7. An apparatus, comprising:

at least one processor; and

at least one memory including computer program instructions,

wherein the at least one memory and the computer program instructions are configured to, with the at least one processor, cause the apparatus at least to:

transmit to a network node, by the apparatus, at least one proximity service buffer status report for device-to-device communication mode, wherein resources for the apparatus are scheduled based on the at least one proximity service buffer status report; and

indicate, to the network node, an early release of the resources allocated to the apparatus based on the at least one proximity service buffer status report, when the resources allocated to the apparatus apply to delay tolerant data or low priority data; and

keep the resources allocated at the apparatus when the resources are used for delay critical or high priority data.

8. The apparatus as recited in claim 7 , wherein the early release is indicated using a physical uplink control channel format 1 resource with multiple occurrences during an allocation period.

9. The apparatus as recited in claim 7 , wherein the early release is indicated by transmitting at least one proximity service buffer status report using physical uplink shared channel.

10. The apparatus as recited in claim 7 , wherein the apparatus is configured with a periodic proximity service buffer status report expiry timer such that the proximity service buffer status report is triggered with constant intervals during an allocation period.

11. The apparatus as recited in claim 7 , wherein the indication of the early release of resources is transmitted using a padding buffer status report to indicate last transmission during an allocation period.

12. The apparatus as recited in claim 7 , wherein the proximity service buffer status report is triggered by a polling from the network node with an allocation of physical uplink shared channel resources.

13. An apparatus, comprising:

at least one processor; and

at least one memory including computer program instructions,

wherein the at least one memory and the computer program instructions are configured to, with the at least one processor, cause the apparatus at least to:

receive, from a user equipment, at least one proximity service buffer status report for device-to-device communication mode 1 , wherein resources for the user equipment are scheduled based on the at least one proximity service buffer status report;

receive an indication, from the user equipment, of an early release of the resources allocated to the user equipment based on the at least one proximity service buffer status report, wherein the early release of resources applies to delay tolerant data or low priority data, and wherein the user equipment keeps the resources allocated when they are used for delay critical or high priority data; and

allocate the released resources to another user equipment than the user equipment for physical uplink shared channel transmissions.

14. The apparatus as recited in claim 13 , wherein the early release is indicated using a physical uplink control channel format 1 resource with multiple occurrences during an allocation period.

15. The apparatus as recited in claim 13 , wherein the early release is indicated by receiving at least one proximity service buffer status report on physical uplink shared channel.

16. The apparatus as recited in claim 13 , wherein the user equipment is configured with a periodic proximity service buffer status report expiry timer such that the proximity service buffer status report is received with constant intervals during an allocation period.

17. The apparatus as recited in claim 13 , wherein the indication of the early release of resources is received by a padding buffer status report to indicate last transmission during an allocation period.

18. The apparatus as recited in claim 13 , wherein the proximity service buffer status report is received by a polling from the apparatus with an allocation of physical uplink shared channel resources.