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

• US 9,730,105 B2
• Filed: 05/19/2014
• Issued: 08/08/2017
• Est. Priority Date: 05/20/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Damnjanovic, Aleksandar, Bhushan, Naga, Gaal, Peter, Luo, Tao, Ji, Tingfang, Horn, Gavin Bernard, Chen, Wanshi, Malladi, Durga Prasad, Wei, Yongbin
• Primary Examiner(s): Hailu, Kibrom T
• Application Number:
  US14/281,617
• Publication Number:
  US 20140341207A1
• Time in Patent Office: 1,177 Days
• Field of Search: None
• CPC Class Codes: H04J 11/00 Orthogonal multiplex systems, e.g. using WALSH codesH04J13/00 takes precedence
• CPC Class Codes: H04L 1/00 Arrangements for detecting or preventing errors in the information received correcting synchronisation H04L7/00
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/003 Adaptive formatting arrangements particular to signalling, e.g. variable amount of bits
• CPC Class Codes: H04L 1/009 arrangements specific to transmitters
• CPC Class Codes: H04L 1/0612 Space-time modulation
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2603 Signal structure ensuring backward compatibility with legacy system
• CPC Class Codes: H04L 5/001 the frequencies being arranged in component carriers
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04L 5/1469 using time-sharing
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 28/0252 per individual bearer or channel dynamic wireless traffic scheduling H04W72/12
• CPC Class Codes: H04W 28/0289 : Congestion control load shedding arrangements in network planning H04W16/08; performing reselection for handling the traffic H04W36/22; wireless traffic scheduling H04W72/12
• CPC Class Codes: H04W 28/08 : Load balancing or load distribution transferring a connection for handling the traffic H04W36/22; wireless traffic scheduling H04W72/12
• CPC Class Codes: H04W 28/16 : Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
• CPC Class Codes: H04W 48/10 : using broadcasted information
• CPC Class Codes: H04W 56/001 : Synchronization between nodes
• CPC Class Codes: H04W 56/0015 : one node acting as a reference for the others
• CPC Class Codes: H04W 56/002 : Mutual synchronization
• CPC Class Codes: H04W 72/04 : Wireless resource allocation
• CPC Class Codes: H04W 72/12 : Wireless traffic scheduling
• CPC Class Codes: H04W 72/21 : in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 72/541 : using the level of interference
• CPC Class Codes: H04W 74/006 : in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 74/04 : Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 74/0808 : using carrier sensing, e.g. carrier sense multiple access [CSMA]
• CPC Class Codes: H04W 74/0816 : with collision avoidance
• CPC Class Codes: H04W 74/0833 : Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 76/15 : Setup of multiple wireless link connections
• CPC Class Codes: H04W 84/12 : WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/02 : Terminal devices
• CPC Class Codes: H04W 88/06 : adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: H04W 88/08 : Access point devices

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.

Claims

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.

68. The computer program product of claim 6, wherein two or more of the eNBs use the same CCA slot to perform CCA during a gating interval.

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.

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 sequence generation, the subset being associated with a deployment of base stations by a single operator.

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.

32. The computer program product of claim 25, wherein the first OFDM symbol position and the second OFDM symbol position are nonadjacent.

33. A method for wireless communications, comprising:

performing, in an aligned clear channel assessment (CCA) period comprising a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbol positions, 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, 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.

34. The method of claim 33, wherein the transmissions comprise downlink transmissions.

35. The method of claim 33, wherein two or more of the eNBs use the same CCA slot to perform CCA during a gating interval.

36. The method of claim 33, further comprising:

identifying the one CCA slot based at least in part on a pseudo-random selection sequence generated from a randomization seed.

37. The method of claim 33, further comprising:

identifying the one CCA slot based at least in part on coordination information exchanged between at least a subset of the plurality of eNBs over a backhaul.

38. The method of claim 33, further comprising:

transmitting, when the unlicensed spectrum is determined to be available, one or more signals before the next transmission interval to reserve the unlicensed spectrum during the next transmission interval.

39. The method of claim 38, wherein each of the one or more signals starts at a boundary of one of the plurality of CCA slots.

40. The method of claim 38, wherein the one or more signals comprise at least one pilot signal for one or both of time-frequency synchronization and channel quality estimation over the unlicensed spectrum.

41. The method of claim 40, wherein the at least one pilot signal is used by a user equipment (UE) to make channel quality measurements on different resource elements to report a channel quality to the respective one of the plurality of eNBs.

42. The method of claim 40, further comprising:

receiving at one of the plurality of eNBs a report of a channel quality from a respective UE in response to the one or more signals, the report being based at least on channel quality measurements made by the UE on different resource elements using the at least one pilot signal; and

allocating resource elements for transmissions from the one eNB to the respective UE to provide fractional resource reuse among multiple UEs to avoid interference.

43. The method of claim 33, wherein the first OFDM symbol position and the second OFDM symbol position are nonadjacent.

44. An apparatus for wireless communications, comprising:

means for performing, in an aligned clear channel assessment (CCA) period comprising a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbol positions, 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, 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.

45. The apparatus of claim 44, wherein the transmissions comprise downlink transmissions.

46. The apparatus of claim 44, wherein two or more of the eNBs use the same CCA slot to perform CCA during a gating interval.

47. The apparatus of claim 44, further comprising:

means for identifying the one CCA slot based at least in part on a pseudo-random selection sequence generated from a randomization seed.

48. The apparatus of claim 44, further comprising:

means for identifying the one CCA slot based at least in part on coordination information exchanged between at least a subset of the plurality of eNBs over a backhaul.

49. The apparatus of claim 44, further comprising:

means for transmitting, when the unlicensed spectrum is determined to be available, one or more signals before the next transmission interval to reserve the unlicensed spectrum during the next transmission interval.

50. The apparatus of claim 49, wherein each of the one or more signals starts at a boundary of one of the plurality of CCA slots.

51. The apparatus of claim 49, wherein the one or more signals comprise at least one pilot signal for one or both of time-frequency synchronization and channel quality estimation over the unlicensed spectrum.

52. The apparatus of claim 51, wherein the at least one pilot signal is used by a user equipment (UE) to make channel quality measurements on different resource elements to report a channel quality to the respective one of the plurality of eNBs.

53. The apparatus of claim 51, further comprising:

means for receiving at one of the plurality of eNBs a report of a channel quality from a respective UE in response to the one or more signals, the report being based at least on channel quality measurements made by the UE on different resource elements using the at least one pilot signal; and

means for allocating resource elements for transmissions from the one eNB to the respective UE to provide fractional resource reuse among multiple UEs to avoid interference.

54. The apparatus of claim 44, wherein the first OFDM symbol position and the second OFDM symbol position are nonadjacent.

55. 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;

perform, in an aligned clear channel assessment (CCA) period comprising a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbol positions, 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, 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.

56. The apparatus of claim 55, wherein the transmissions comprise downlink transmissions.

57. The apparatus of claim 55, wherein two or more of the eNBs use the same CCA slot to perform CCA during a gating interval.

58. The apparatus of claim 55, wherein the instructions are further executable by the processor to:

identify the one CCA slot based at least in part on a pseudo-random selection sequence generated from a randomization seed.

59. The apparatus of claim 55, wherein the instructions are further executable by the processor to:

identify the one CCA slot based at least in part on coordination information exchanged between at least a subset of the plurality of eNBs over a backhaul.

60. The apparatus of claim 55, wherein the instructions are further executable by the processor to:

transmit, when the unlicensed spectrum is determined to be available, one or more signals before the next transmission interval to reserve the unlicensed spectrum during the next transmission interval.

61. The apparatus of claim 60, wherein each of the one or more signals starts at a boundary of one of the plurality of CCA slots.

62. The apparatus of claim 60, wherein the one or more signals comprise at least one pilot signal for one or both of time-frequency synchronization and channel quality estimation over the unlicensed spectrum.

63. The apparatus of claim 62, wherein the at least one pilot signal is used by a user equipment (UE) to make channel quality measurements on different resource elements to report a channel quality to the respective one of the plurality of eNBs.

64. The apparatus of claim 62, wherein the instructions are further executable by the processor to:

receive at one of the plurality of eNBs a report of a channel quality from a respective UE in response to the one or more signals, the report being based at least on channel quality measurements made by the UE on different resource elements using the at least one pilot signal; and

allocate resource elements for transmissions from the one eNB to the respective UE to provide fractional resource reuse among multiple UEs to avoid interference.

65. The apparatus of claim 55, wherein the first OFDM symbol position and the second OFDM symbol position are nonadjacent.

66. 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:

perform, in an aligned clear channel assessment (CCA) period comprising a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbol positions, 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, 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.

67. The computer program product of claim 66, wherein the transmissions comprise downlink transmissions.

69. The computer program product of claim 66, wherein the instructions are executable by the processor to cause the wireless communications apparatus to:

identify the one CCA slot based at least in part on a pseudo-random selection sequence generated from a randomization seed.

70. The computer program product of claim 66, wherein the instructions are executable by the processor to cause the wireless communications apparatus to:

identify the one CCA slot based at least in part on coordination information exchanged between at least a subset of the plurality of eNBs over a backhaul.

71. The computer program product of claim 66, wherein the instructions are executable by the processor to cause the wireless communications apparatus to:

transmit, when the unlicensed spectrum is determined to be available, one or more signals before the next transmission interval to reserve the unlicensed spectrum during the next transmission interval.

72. The computer program product of claim 71, wherein each of the one or more signals starts at a boundary of one of the plurality of CCA slots.

73. The computer program product of claim 71, wherein the one or more signals comprise at least one pilot signal for one or both of time-frequency synchronization and channel quality estimation over the unlicensed spectrum.

74. The computer program product of claim 73, wherein the at least one pilot signal is used by a user equipment (UE) to make channel quality measurements on different resource elements to report a channel quality to the respective one of the plurality of eNB s.

75. The computer program product of claim 73, wherein the instructions are executable by the processor to cause the wireless communications apparatus to:

receive at one of the plurality of eNBs a report of a channel quality from a respective UE in response to the one or more signals, the report being based at least on channel quality measurements made by the UE on different resource elements using the at least one pilot signal; and

allocate resource elements for transmissions from the one eNB to the respective UE to provide fractional resource reuse among multiple UEs to avoid interference.

76. The computer program product of claim 66, wherein the first OFDM symbol position and the second OFDM symbol position are nonadjacent.