Methods, apparatus and systems for indicating transmission failures in a wireless communication

1. A method performed by a wireless communication device, the method comprising:

determining a type of a to-be-transmitted message;

obtaining, by a media access control (MAC) layer of the wireless communication device, an indication from a physical layer of the wireless communication device when the type of the message belongs to a message type group, wherein the indication indicates a transmission failure of the wireless communication device at the physical layer, the transmission failure being due to a listen-before-talk (LBT) failure in unlicensed spectrum;

starting, in response to the indication, a timer at the MAC layer;

incrementing, in response to the indication, a counter at the MAC layer by one;

determining that the counter has reached a predetermined threshold; and

indicating, after the timer is started, a MAC layer transmission failure to a radio resource control (RRC) layer of the wireless communication device.

2. The method of claim 1 , further comprising:

restarting, in response to another indication indicating a transmission failure of the wireless communication device at the physical layer due to an LBT failure in unlicensed spectrum, the timer at the MAC layer.

3. The method of claim 1 , further comprising:

resetting the counter at the MAC layer in response to an expiration of the timer.

4. The method of claim 1 , further comprising

determining a radio link failure (RLF) at the RRC layer based on the indicated MAC layer transmission failure.

5. A user equipment configured to carry out the method of claim 1 .

6. The user equipment of claim 5 , further configured to restart, in response to another indication indicating a transmission failure of the wireless communication device at the physical layer due to an LBT failure in unlicensed spectrum, the timer at the MAC layer.

7. The user equipment of claim 5 , further configured to reset the counter at the MAC layer in response to an expiration of the timer.

8. The user equipment of claim 5 , further configured to determine a radio link failure (RLF) at the RRC layer based on the indicated MAC layer transmission failure.

9. A wireless communication device, comprising:

a physical layer, configured to provide an indication when a type of the message is determined to belong to a message type group, which indicates a transmission failure of the wireless communication device at the physical layer, the transmission failure being due to a listen-before-talk (LBT) failure in unlicensed spectrum;

a media access control (MAC) layer, configured to obtain the indication and comprising:

a timer, configured to be started in response to the indication; and

a counter, configured to be incremented by one in response to the indication; and

the MAC layer is further configured to:

determine whether the counter has reached a predetermined threshold; and

in response to determining the counter has reached the predetermined threshold, indicate, after the timer is started, a MAC layer transmission failure to a radio resource control (RRC) layer of the wireless communication device.

10. The wireless communication device of claim 9 , wherein the timer is further configured to be restarted in response to another indication indicating a transmission failure of the wireless communication device at the physical layer due to an LBT failure in unlicensed spectrum.

11. The wireless communication device of claim 9 , wherein the counter is further configured to be reset in response to an expiration of the timer.

12. The wireless communication device of claim 9 , wherein the RRC layer is further configured to determine a radio link failure (RLF) based on the indication of the MAC layer transmission failure.

13. A non-transitory computer-readable medium having stored thereon computer executable instructions, the computer executable instructions, when being executed, configured to cause a wireless communication device to perform steps comprising:

determining a type of a to-be-transmitted message;

obtaining, by a media access control (MAC) layer of the wireless communication device, an indication from a physical layer of the wireless communication device when the type of the message belongs to a message type group, wherein the indication indicates a transmission failure of the wireless communication device at the physical layer, the transmission failure being due to a listen-before-talk (LBT) failure in unlicensed spectrum;

starting, in response to the indication, a timer at the MAC layer;

incrementing, in response to the indication, a counter at the MAC layer by one;

determining that the counter has reached a predetermined threshold; and

indicating, after the timer is started, a MAC layer transmission failure to a radio resource control (RRC) layer of the wireless communication device.

14. The non-transitory computer-readable medium of claim 13 , wherein the computer executable instructions, when being executed, is further configured to cause the wireless communication device to restart, in response to another indication indicating a transmission failure of the wireless communication device at the physical layer due to an LBT failure in unlicensed spectrum, the timer at the MAC layer.

15. The non-transitory computer-readable medium of claim 13 , wherein the computer executable instructions, when being executed, is further configured to cause the wireless communication device to reset the counter at the MAC layer in response to an expiration of the timer.

16. The non-transitory computer-readable medium of claim 13 , wherein the computer executable instructions, when being executed, is further configured to cause the wireless communication device to determine a radio link failure (RLF) at the RRC layer based on the indicated MAC layer transmission failure.