COUPLING UPLINK AND DOWNLINK CCA IN LTE-U

• US 20150071060A1
• Filed: 09/08/2014
• Published: 03/12/2015
• Est. Priority Date: 09/11/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Bhushan, Naga, Damnjanovic, Aleksandar, Ji, Tingfang, Gaal, Peter, Malladi, Durga Prasad
• Granted Patent: US 9,949,292 B2
• Time in Patent Office: Days
• US Class Current: 370/230
• CPC Class Codes: H04L 5/0091 Signaling for the administration of the divided path
• CPC Class Codes: H04W 36/22 for handling the traffic
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]

Abstract

Methods, systems, and devices are described contention-based channel access procedures that may enhance efficiency in communications using unlicensed spectrum. A time period may be identified during which base stations perform contention-based downlink channel access procedures for access to a channel in an unlicensed spectrum. The base stations may be coordinated such that different base stations may seek channel access during different time intervals during the time period. Contention-based uplink channel access procedures for UEs may then be modified to favor one or more UEs that are associated with a base station that has won channel access.

Claims

1. A method for wireless communication, comprising:

identifying a time period during which at least a first base station and a second base station perform contention-based downlink channel access procedures for access to a channel in an unlicensed spectrum;

determining that the first base station has won or is more likely to win the downlink channel access; and

modifying a contention-based uplink channel access procedure for a first user equipment (UE) associated with the first base station to favor the first UE gaining access to the channel in the unlicensed spectrum.

2. The method of claim 1, wherein the modifying comprises:

adjusting a time for performing a clear channel assessment (CCA) at the first UE responsive to the determining.

3. The method of claim 2, wherein the determining that the first base station has won channel access comprises:

monitoring a channel usage beacon signal (CUBS) of the base stations to determine that the first base station has won channel access.

4. The method of claim 2, wherein the adjusting comprises:

changing a CCA interval of the first UE to be an earliest available CCA interval for performing the uplink channel access procedure.

5. The method of claim 4, further comprising:

modifying the uplink channel access procedure for a second UE associated with the second base station to favor the first UE gaining access to the channel in the unlicensed spectrum responsive to determining that the first base station has won channel access.

6. The method of claim 5, wherein:

modifying the uplink channel access procedure for the second UE comprises assigning a scheduled CCA interval for the first UE to the second UE when the second UE is scheduled to perform the uplink channel access procedure during the earliest available CCA interval.

7. The method of claim 6, wherein the modifying comprises modifying a mapping function F_U(groupID, t) for determining a CCA interval for the first UE based on groupIDs of the base stations as follows:

8. The method of claim 5, wherein modifying the uplink channel access procedure for the second UE comprises:

determining a number of CCA intervals between a scheduled CCA interval for the first UE and the earliest available CCA interval; and

shifting a scheduled CCA interval for the second UE by the determined number of CCA intervals.

9. The method of claim 8, wherein the modifying comprises modifying a mapping function F_U(groupID, t) for determining a CCA interval for the first UE based on groupIDs of the base stations as follows:

F_U^mod(groupID,t)=1+mod(F_U(groupID,t)−

F_U(g_A(t),t),7)

where g_A(t)=the groupID of the first base station.

10. The method of claim 5, wherein modifying the uplink channel access procedure for the second UE comprises:

deferring uplink channel access to a subsequent channel access period.

11. The method of claim 1, wherein the modifying comprises:

determining a scheduled clear channel assessment (CCA) interval of the first base station from a plurality of available CCA intervals; and

setting a CCA interval for the first UE based on the scheduled CCA interval of the first base station.

12. The method of claim 1, wherein the time period during which the first base station and the second base station perform the downlink channel access procedures comprises clear channel assessment (CCA) intervals, and wherein the CCA intervals of the first base station and the second base station are non-overlapping, and wherein the CCA intervals of the first base station and at least one other base station are overlapping.

13. The method of claim 12, wherein the CCA intervals are determined based on a pseudo-random selection from available CCA intervals, and wherein a group of base stations comprising the first base station and the at least one other base station have a same CCA interval.

14. The method of claim 13, wherein modifying the uplink channel access procedure comprises:

determining that one of the base stations of the group of base stations has won channel access to the channel; and

adjusting a time for performing a CCA at the first UE and at least one other UE associated with the at least one other base station responsive to the determining.

15. The method of claim 14, wherein the adjusting comprises:

selecting a CCA interval for UEs associated with the group of base stations from a set of CCA intervals, the set of CCA intervals comprising CCA intervals that are earlier than CCA intervals of one or more UEs associated with one or more base stations outside of the group of base stations.

16. An apparatus for wireless communication, comprising:

means for identifying a time period during which at least a first base station and a second base station perform contention-based downlink channel access procedures for access to a channel in an unlicensed spectrum;

means for determining that the first base station has won or is more likely to win the downlink channel access; and

means for modifying a contention-based uplink channel access procedure for a first user equipment (UE) associated with the first base station to favor the first UE gaining access to the channel in the unlicensed spectrum.

17. The apparatus of claim 16, wherein the means for modifying adjusts a time for performing a clear channel assessment (CCA) at the first UE responsive to the determining.

18. The apparatus of claim 17, wherein the means for modifying changes a CCA interval of the first UE to be an earliest available CCA interval for performing the uplink channel access procedure.

19. The apparatus of claim 16, wherein the means for modifying determines a scheduled clear channel assessment (CCA) interval of the first base station from a plurality of available CCA intervals, and sets a CCA interval for the first UE based on the scheduled CCA interval of the first base station.

20. The apparatus of claim 16, wherein the time period during which the first base station and the second base station perform the downlink channel access procedures comprises clear channel assessment (CCA) intervals, and wherein the CCA intervals of the first base station and the second base station are non-overlapping, and wherein the CCA intervals of the first base station and at least one other base station are overlapping.

21. The apparatus of claim 20, wherein the CCA intervals are determined based on a pseudo-random selection from available CCA intervals, and wherein a group of base stations comprising the first base station and the at least one other base station have a same CCA interval.

22. The apparatus of claim 21, wherein the means for modifying the uplink channel access procedure determines that one of the base stations of the group of base stations has won channel access to the channel, and adjusts a time for performing a CCA at the first UE and at least one other UE associated with the at least one other base station responsive to the determining.

23. An apparatus for wireless communications, comprising:

a processor;

memory coupled to the processor;

wherein the processor is configured to;

identify a time period during which at least a first base station and a second base station perform contention-based downlink channel access procedures for access to a channel in an unlicensed spectrum;

determine that the first base station has won or is more likely to win the downlink channel access; and

modify a contention-based uplink channel access procedure for a first user equipment (UE) associated with the first base station to favor the first UE gaining access to the channel in the unlicensed spectrum.

24. The apparatus of claim 23, wherein the processor is further configured to adjust a time for performing a clear channel assessment (CCA) at the first UE responsive to the determining.

25. The apparatus of claim 24, wherein the processor is further configured to change a CCA interval of the first UE to be an earliest available CCA interval for performing the uplink channel access procedure.

26. The apparatus of claim 23, wherein the processor is further configured to determine a scheduled clear channel assessment (CCA) interval of the first base station from a plurality of available CCA intervals, and set a CCA interval for the first UE based on the scheduled CCA interval of the first base station.

27. The apparatus of claim 23, wherein the time period during which the first base station and the second base station perform the downlink channel access procedures comprises clear channel assessment (CCA) intervals, and wherein the CCA intervals of the first base station and the second base station are non-overlapping, and wherein the CCA intervals of the first base station and at least one other base station are overlapping.

28. The apparatus of claim 27, wherein the CCA intervals are determined based on a pseudo-random selection from available CCA intervals, and wherein a group of base stations comprising the first base station and the at least one other base station have a same CCA interval.

29. The apparatus of claim 28, wherein the processor is further configured to determine that one of the base stations of the group of base stations has won channel access to the channel, and adjust a time for performing a CCA at the first UE and at least one other UE associated with the at least one other base station responsive to the determining.

30. A non-transitory computer-readable medium for storing instructions executable by a processor, comprising:

instructions to identify a time period during which at least a first base station and a second base station perform contention-based downlink channel access procedures for access to a channel in an unlicensed spectrum;

instructions to determine that the first base station has won or is more likely to win the downlink channel access; and

instructions to modify a contention-based uplink channel access procedure for a first user equipment (UE) associated with the first base station to favor the first UE gaining access to the channel in the unlicensed spectrum.