Listen-before-talk reservation scheme for wireless communications over unlicensed spectrum

Patent metadata

Field	Value
Publication number	US-9730105-B2
Application number	US-201414281617-A
Country	US
Kind code	B2
Filing date	May 19, 2014
Priority date	May 20, 2013
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

Methods and apparatuses are described in which an unlicensed spectrum is used for Long Term Evolution (LTE) communications. A first method includes synchronizing clear channel assessment (CCA) slots across a plurality of base stations to determine availability of an unlicensed spectrum for transmissions in a next transmission interval. A second method includes performing a CCA during one of a plurality of CCA slots synchronized across a plurality of evolved Node Bs (eNBs) to determine availability of unlicensed spectrum for transmissions in a next transmission interval.

First claim

What is claimed is:

1. A method for wireless communications, comprising:
synchronizing, in an aligned clear channel assessment (CCA) period comprising a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbol positions, CCA slots across a plurality of base stations to determine availability of an unlicensed spectrum for transmissions in a next transmission interval, wherein a first CCA slot of the CCA slots is aligned with a first OFDM symbol position of the plurality of OFDM symbol positions and a second CCA slot of the CCA slots is aligned with a second OFDM symbol position of the OFDM symbol positions.

2. The method of claim 1 , wherein the transmissions comprise downlink transmissions.

3. The method of claim 1 , wherein the CCA slots are located in a last subframe of a current gating interval.

4. The method of claim 1 , wherein the CCA slots are located in a first subframe of a current gating interval.

5. The method of claim 1 , wherein an interval between commencement of adjacent CCA slots is approximately a duration of an OFDM symbol.

6. The method of claim 1 , further comprising:
identifying one of the CCA slots in which to determine the availability of the unlicensed spectrum, wherein the one CCA slot is identified based at least in part on a pseudo-random selection sequence driven by a randomization seed.

7. The method of claim 6 , wherein a subset of the plurality of base stations use the same randomization seed for their pseudo-random selection sequence generation, the subset being associated with a deployment of base stations by a single operator.

8. The method of claim 1 , wherein the first OFDM symbol position and the second OFDM symbol position are nonadjacent.

9. An apparatus for wireless communications, comprising:
means for synchronizing, in an aligned clear channel assessment (CCA) period comprising a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbol positions, CCA slots across a plurality of base stations to determine availability of an unlicensed spectrum for transmissions in a next transmission interval, wherein a first CCA slot of the CCA slots is aligned with a first OFDM symbol position of the plurality of OFDM symbol positions and a second CCA slot of the CCA slots is aligned with a second OFDM symbol position of the OFDM symbol positions.

10. The apparatus of claim 9 , wherein the transmissions comprise downlink transmissions.

11. The apparatus of claim 9 , wherein the CCA slots are located in a last subframe of a current gating interval.

12. The apparatus of claim 9 , wherein the CCA slots are located in a first subframe of a current gating interval.

13. The apparatus of claim 9 , wherein an interval between commencement of adjacent CCA slots is approximately a duration of an OFDM symbol.

14. The apparatus of claim 9 , further comprising:
means for identifying one of the CCA slots in which to determine the availability of unlicensed spectrum, wherein the one CCA slot is identified based at least in part on a pseudo-random selection sequence driven by a randomization seed.

15. The apparatus of claim 14 , wherein a subset of the plurality of base stations use the same randomization seed for their pseudo-random selection sequence generation, the subset being associated with a deployment of base stations by a single operator.

16. The apparatus of claim 9 , wherein the first OFDM symbol position and the second OFDM symbol position are nonadjacent.

17. An apparatus for wireless communications, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory, the instructions being executable by the processor to:
synchronize, in an aligned clear channel assessment (CCA) period comprising a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbol positions, CCA slots across a plurality of base stations to determine availability of an unlicensed spectrum for transmissions in a next transmission interval, wherein a first CCA slot of the CCA slots is aligned with a first OFDM symbol position of the plurality of OFDM symbol positions and a second CCA slot of the CCA slots is aligned with a second OFDM symbol position of the OFDM symbol positions.

18. The apparatus of claim 17 , wherein the transmissions comprise downlink transmissions.

19. The apparatus of claim 17 , wherein the CCA slots are located in a last subframe of a current gating interval.

20. The apparatus of claim 17 , wherein the CCA slots are located in a first subframe of a current gating interval.

21. The apparatus of claim 17 , wherein an interval between commencement of adjacent CCA slots is approximately a duration of an OFDM symbol.

22. The apparatus of claim 17 , wherein the instructions are executable by the processor to:
identify one of the CCA slots in which to determine the availability of unlicensed spectrum, wherein the one CCA slot is identified based at least in part on a pseudo-random selection sequence driven by a randomization seed.

23. The apparatus of claim 22 , wherein a subset of the plurality of base stations use the same randomization seed for their pseudo-random selection sequence generation, the subset being associated with a deployment of base stations by a single operator.

24. The apparatus of claim 17 , wherein the first OFDM symbol position and the second OFDM symbol position are nonadjacent.

25. A computer program product for communications by a wireless communications apparatus in a wireless communications system, the computer program product comprising a non-transitory computer-readable medium storing instructions executable by a processor to cause the wireless communications apparatus to:
synchronize, in an aligned clear channel assessment (CCA) period comprising a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbol positions, CCA slots across a plurality of base stations to determine availability of an unlicensed spectrum for transmissions in a next transmission interval, wherein a first CCA slot of the CCA slots is aligned with a first OFDM symbol position of the plurality of OFDM symbol positions and a second CCA slot of the CCA slots is aligned with a second OFDM symbol position of the OFDM symbol positions.

26. The computer program product of claim 25 , wherein the transmissions comprise downlink transmissions.

27. The computer program product of claim 17 , wherein the CCA slots are located in a last subframe of a current gating interval.

28. The computer program product of claim 17 , wherein the CCA slots are located in a first subframe of a current gating interval.

29. The computer program product of claim 17 , wherein an interval between commencement of adjacent CCA slots is approximately a duration of an OFDM symbol.

30. The computer program product of claim 17 , wherein the instructions are executable by the processor to cause the wireless communications apparatus to:
identify one of the CCA slots in which to determine the availability of unlicensed spectrum, wherein the one CCA slot is identified based at least in part on a pseudo-random selection sequence driven by a randomization seed.

31. The computer program product of claim 22 , wherein a subset of the plurality of base stations use the same randomization seed for their pseudo-random selection se

Assignees

• Qualcomm Inc
• Qualcomm Inc

Inventors

• Bhushan Naga
• Malladi Durga Prasad
• Wei Yongbin
• Gaal Peter
• Luo Tao
• Ji Tingfang
• Horn Gavin Bernard
• Chen Wanshi
• Damnjanovic Aleksandar

Classifications

• H04L5/001 Primary

  the frequencies being arranged in component carriers · CPC title

• H04W72/21

  in the uplink direction of a wireless link, i.e. towards the network · CPC title

• H04W72/541

  using the level of interference · CPC title

• H04W74/0808

  using carrier sensing, e.g. carrier sense multiple access [CSMA] · CPC title

• H04W74/0816 Primary

  with collision avoidance · CPC title