Apparatus and method for channel access for long term evolution nodes in unlicensed band

1. A method, comprising:

sensing, by an apparatus, a shared channel;

determining whether the shared channel is free;

determining whether a synchronization signal has been received; and

based on whether the shared channel is determined free and whether the synchronization signal is determined received, beginning to access the shared channel, wherein the synchronization signal indicates to terminate a backoff mechanism and access the shared channel, and wherein the sensing the shared channel is performed separately from determining whether the synchronization signal has been received, the sensing is performable before or after the determining whether the synchronization signal has been received.

2. The method of claim 1 , further comprising:

selecting a number of slots for a backoff time period; and

initializing a slot counter.

3. The method of claim 2 , wherein a number of slots for the backoff time period is selected when the shared channel has been determined not free.

4. The method of claim 2 , further comprising:

when the shared channel is determined not free, repeating the steps of sensing the shared channel, determining whether the shared channel is free, and determining whether the synchronization signal has been received.

5. The method of claim 2 , further comprising:

when the shared channel is determined free and the synchronization signal is determined not received, decrementing the slot counter; and

if the slot counter is not equal to zero, repeating the steps of sensing the shared channel, determining whether the shared channel is free, and determining whether the synchronization signal has been received; and

if the slot counter is equal to zero, transmitting a synchronization signal.

6. The method of claim 1 , wherein beginning to access the shared channel is after a predefined period from the determination that the synchronization signal has been received.

7. An apparatus, comprising:

at least one processor;

and at least one memory including computer program code,

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

sense a shared channel;

determine whether the shared channel is free;

determine whether a synchronization signal has been received; and

based on whether the shared channel is determined free and whether the synchronization signal is determined received, begin to access the shared channel, wherein the synchronization signal indicates to terminate a backoff mechanism and access the shared channel, and wherein the sensing the shared channel is performed separately from determining whether the synchronization signal has been received, the sensing is performable before or after the determining whether the synchronization signal has been received.

8. The apparatus according to claim 7 , wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least further to:

select a number of slots for a backoff time period; and

initialize a slot counter.

9. The apparatus of claim 8 , wherein a number of slots for the backoff time period is selected when the shared channel has been determined not free.

10. The apparatus according to claim 8 , wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least further to:

when the shared channel is determined not free, repeat the steps of sensing the shared channel, determining whether the shared channel is free, and determining whether the synchronization signal has been received.

11. The apparatus according to claim 8 , wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least further to:

when the shared channel is determined free and the synchronization signal is determined not received, decrement the slot counter; and

if the slot counter is not equal to zero, repeat the steps of sensing the shared channel, determining whether the shared channel is free, and determining whether the synchronization signal has been received; and

if the slot counter is equal to zero, transmit a synchronization signal.

12. The apparatus of claim 7 , wherein the apparatus begins to access the shared channel after a predefined period from the determination that the synchronization signal has been received.

13. A computer program product comprising a non-transitory computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program product configured to control a processor of the computer to perform a method, comprising:

sensing a shared channel;

determining whether the shared channel is free;

determining whether a synchronization signal has been received; and

beginning to access the shared channel, based on whether the shared channel is determined free and whether the synchronization signal is determined received, wherein the synchronization signal indicates to terminate a backoff mechanism and access the shared channel, and wherein the sensing the shared channel is performed separately from determining whether the synchronization signal has been received, the sensing is performable before or after the determining whether the synchronization signal has been received.

14. The computer program product according to claim 13 , the method further comprising:

selecting a number of slots for a backoff time period; and

initializing a slot counter.

15. The computer program product according to claim 14 , wherein a number of slots for the backoff time period is selected when the shared channel has been determined not free.

16. The computer program product according to claim 14 , the method further comprising:

when the shared channel is determined not free, repeating the steps of sensing the shared channel, determining whether the shared channel is free, and determining whether the synchronization signal has been received.

17. The computer program product according to claim 14 , the method further comprising:

when the shared channel is determined free and the synchronization signal is determined not received,

decrementing the slot counter; and

if the slot counter is not equal to zero, repeating the steps of sensing the shared channel, determining whether the shared channel is free, and determining whether the synchronization signal has been received; and

if the slot counter is equal to zero, transmitting a synchronization signal.

18. The computer program product according to claim 13 , wherein beginning to access the shared channel is after a predefined period from the determination that the synchronization signal has been received.