BACKOFF PROCEDURE FOR POST DOWNLINK SDMA OPERATION

• US 20110141969A1
• Filed: 12/15/2009
• Published: 06/16/2011
• Est. Priority Date: 12/15/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chu, Josephine Pui Kwan, Sridhara, Vinay, Abraham, Santosh P.
• Granted Patent: US 8,477,801 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 74/085 collision avoidance

Abstract

Certain aspects of the present disclosure relate to a technique for decreasing a probability of post-backoff collisions that occur during uplink transmissions from multiple user stations (STAs) following completion of downlink transmission from an access point to the STAs.

Claims

1. A method for wireless communications, comprising:

determining a backoff value for each of a plurality of apparatuses to receive simultaneous transmissions, wherein the backoff values are determined, at least in part, based on a number of the apparatuses and wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before transmitting; and

transmitting the determined backoff values to the apparatuses.

2. The method of claim 1, wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before sending transport layer acknowledgements.

3. The method of claim 1, wherein determining the backoff value for each of the apparatuses comprises:

assigning, to each of the apparatuses, a unique value from a randomly sorted array of numbers between one and a defined value, if the number of the apparatuses is smaller than the defined value.

4. The method of claim 3, wherein the defined value comprises a minimum contention window size.

5. The method of claim 1, wherein determining the backoff value for each of the apparatuses comprises:

assigning, to each of the apparatuses, a unique value from a randomly sorted array of numbers between one and a first value greater than the number of the apparatuses, if the number of the apparatuses is greater than a second value.

6. The method of claim 5, wherein the second value comprises a minimum contention window size.

7. The method of claim 1, wherein the determined backoff values are transmitted in a message requesting access to the apparatuses.

8. The method of claim 1, wherein the determined backoff values are transmitted in one or more header fields of an Aggregate Physical Layer Protocol Data Unit (APPDU) frame.

9. An apparatus for wireless communications, comprising:

a processing system configured to determine a backoff value for each of a plurality of apparatuses to receive simultaneous transmissions, wherein the backoff values are determined, at least in part, based on a number of the apparatuses and wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before transmitting; and

a transmitter configured to transmit the determined backoff values to the apparatuses.

10. The apparatus of claim 9, wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before sending transport layer acknowledgements.

11. The apparatus of claim 9, wherein the processing system configured to determine the backoff value for each of the apparatuses comprises:

a circuit configured to assign, to each of the apparatuses, a unique value from a randomly sorted array of numbers between one and a defined value, if the number of the apparatuses is smaller than the defined value.

12. The apparatus of claim 11, wherein the defined value comprises a minimum contention window size.

13. The apparatus of claim 9, wherein the processing system configured to determine the backoff value for each of the apparatuses comprises:

a circuit configured to assign, to each of the apparatuses, a unique value from a randomly sorted array of numbers between one and a first value greater than the number of the apparatuses, if the number of the apparatuses is greater than a second value.

14. The apparatus of claim 13, wherein the second value comprises a minimum contention window size.

15. The apparatus of claim 9, wherein the determined backoff values are transmitted in a message requesting access to the apparatuses.

16. The apparatus of claim 9, wherein the determined backoff values are transmitted in one or more header fields of an Aggregate Physical Layer Protocol Data Unit (APPDU) frame.

17. An apparatus for wireless communications, comprising:

means for determining a backoff value for each of a plurality of apparatuses to receive simultaneous transmissions, wherein the backoff values are determined, at least in part, based on a number of the apparatuses and wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before transmitting; and

means for transmitting the determined backoff values to the apparatuses.

18. The apparatus of claim 17, wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before sending transport layer acknowledgements.

19. The apparatus of claim 17, wherein the means for determining the backoff value for each of the apparatuses comprises:

means for assigning, to each of the apparatuses, a unique value from a randomly sorted array of numbers between one and a defined value, if the number of the apparatuses is smaller than the defined value.

20. The apparatus of claim 19, wherein the defined value comprises a minimum contention window size.

21. The apparatus of claim 17, wherein the means for determining the backoff value for each of the apparatuses comprises:

means for assigning, to each of the apparatuses, a unique value from a randomly sorted array of numbers between one and a first value greater than the number of the apparatuses, if the number of the apparatuses is greater than a second value.

22. The apparatus of claim 21, wherein the second value comprises a minimum contention window size.

23. The apparatus of claim 17, wherein the determined backoff values are transmitted in a message requesting access to the apparatuses.

24. The apparatus of claim 17, wherein the determined backoff values are transmitted in one or more header fields of an Aggregate Physical Layer Protocol Data Unit (APPDU) frame.

25. A computer-program product for wireless communications, comprising a computer-readable medium comprising instructions executable to:

determine a backoff value for each of a plurality of apparatuses to receive simultaneous transmissions, wherein the backoff values are determined, at least in part, based on a number of the apparatuses and wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before transmitting; and

transmit the determined backoff values to the apparatuses.

26. An access point, comprising:

at least one antenna;

a processing system configured to determine a backoff value for each of a plurality of wireless nodes to receive simultaneous transmissions, wherein the backoff values are determined, at least in part, based on a number of the wireless nodes and wherein the backoff values indicate how long the wireless nodes should wait after receiving the simultaneous transmissions before transmitting; and

a transmitter configured to transmit via the at least one antenna the determined backoff values to the wireless nodes.

27. A method for wireless communications, comprising:

receiving, at an apparatus of a plurality of apparatuses, a message transmitted from another apparatus to the apparatuses, the message comprising backoff values, wherein each backoff value is assigned to one of the apparatuses; and

refraining from transmitting for a time period indicated by the backoff value assigned to the apparatus.

28. The method of claim 27, further comprising:

transmitting a transport layer acknowledgement to the other apparatus after the time period indicated by the assigned backoff value has been elapsed.

29. The method of claim 27, further comprising:

in response to the message, transmitting sounding information to the other apparatus;

receiving data from the other apparatus, wherein the data were transmitted in response to the sounding information received at the other apparatus; and

in response to the received data, transmitting a Media Access Control (MAC) level acknowledgement to the other apparatus.

30. The method of claim 29, wherein the refraining from transmitting comprises:

refraining from transmitting after the transmission of the MAC level acknowledgement.

31. The method of claim 29, wherein the MAC level acknowledgement comprises a block acknowledgement.

32. The method of claim 31, wherein the block acknowledgement comprises the assigned backoff value.

33. The method of claim 27, wherein the message comprises a Request Message (RM) for accessing the apparatuses.

34. The method of claim 27, wherein the message comprises an Aggregate Physical Layer Protocol Data Unit (APPDU) message.

35. The method of claim 34, wherein a header field of the APPDU message comprises the assigned backoff values.

36. The method of claim 27, wherein each assigned backoff value is unique.

37. An apparatus for wireless communications, comprising:

a receiver configured to receive, at the apparatus of a plurality of apparatuses, a message transmitted from another apparatus to the apparatuses, the message comprising backoff values, wherein each backoff value is assigned to one of the apparatuses; and

a transmitter configured to refrain from transmitting for a time period indicated by the backoff value assigned to the apparatus.

38. The apparatus of claim 37, wherein the transmitter is also configured to transmit a transport layer acknowledgement to the other apparatus after the time period indicated by the assigned backoff value has been elapsed.

39. The apparatus of claim 37, wherein:

the transmitter is also configured to transmit, in response to the message, sounding information to the other apparatus,

the receiver is also configured to receive data from the other apparatus, the data were transmitted in response to the sounding information received at the other apparatus, and

the transmitter is also configured to transmit, in response to the received data, a Media Access Control (MAC) level acknowledgement to the other apparatus.

40. The apparatus of claim 39, wherein the transmitter is also configured to refrain from transmitting after the transmission of the MAC level acknowledgement.

41. The apparatus of claim 39, wherein the MAC level acknowledgement comprises a block acknowledgement.

42. The apparatus of claim 41, wherein the block acknowledgement comprises the assigned backoff value.

43. The apparatus of claim 37, wherein the message comprises a Request Message (RM) for accessing the apparatuses.

44. The apparatus of claim 37, wherein the message comprises an Aggregate Physical Layer Protocol Data Unit (APPDU) message.

45. The apparatus of claim 44, wherein a header field of the APPDU message comprises the assigned backoff values.

46. The apparatus of claim 37, wherein each assigned backoff value is unique.

47. An apparatus for wireless communications, comprising:

means for receiving, at the apparatus of a plurality of apparatuses, a message transmitted from another apparatus to the apparatuses, the message comprising backoff values, wherein each backoff value is assigned to one of the apparatuses; and

means for refraining from transmitting for a time period indicated by the backoff value assigned to the apparatus.

48. The apparatus of claim 47, further comprising:

means for transmitting a transport layer acknowledgement to the other apparatus after the time period indicated by the assigned backoff value has been elapsed.

49. The apparatus of claim 47, further comprising:

means for transmitting, in response to the message, sounding information to the other apparatus, wherein

the means for receiving is further configured to receive data from the other apparatus, the data were transmitted in response to the sounding information received at the other apparatus, and

the means for transmitting is further configured to transmit, in response to the received data, a Media Access Control (MAC) level acknowledgement to the other apparatus.

50. The apparatus of claim 49, wherein the means for refraining from transmitting comprises:

means for refraining from transmitting after the transmission of the MAC level acknowledgement.

51. The apparatus of claim 49, wherein the MAC level acknowledgement comprises a block acknowledgement.

52. The apparatus of claim 51, wherein the block acknowledgement comprises the assigned backoff value.

53. The apparatus of claim 47, wherein the message comprises a Request Message (RM) for accessing the apparatuses.

54. The apparatus of claim 47, wherein the message comprises an Aggregate Physical Layer Protocol Data Unit (APPDU) message.

55. The apparatus of claim 54, wherein a header field of the APPDU message comprises the assigned backoff values.

56. The apparatus of claim 47, wherein each assigned backoff value is unique.

57. A computer-program product for wireless communications, comprising a computer-readable medium comprising instructions executable to:

receive, at an apparatus of a plurality of apparatuses, a message transmitted from another apparatus to the apparatuses, the message comprising backoff values, wherein each backoff value is assigned to one of the apparatuses; and

refrain from transmitting for a time period indicated by the backoff value assigned to the apparatus.

58. A wireless node, comprising:

at least one antenna;

a receiver configured to receive via the at least one antenna, at the wireless node of a plurality of wireless nodes, a message transmitted from an access point to the wireless nodes, the message comprising backoff values, wherein each backoff value is assigned to one of the wireless nodes; and

a transmitter configured to refrain from transmitting for a time period indicated by the backoff value assigned to the wireless node.

59. A method for wireless communications, comprising:

transmitting a control message to each of a plurality of apparatuses to receive simultaneous transmissions;

receiving an acknowledgement message from each of the apparatuses, wherein the acknowledgement messages were transmitted after receiving the control message at the apparatuses; and

in response to the acknowledgement messages, transmitting, to the apparatuses, a backoff timing message with backoff values, wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before transmitting.

60. The method of claim 59, wherein the backoff timing message is transmitted a Short Inter-Frame Space (SIFS) time duration after the reception of the acknowledgement messages.

61. The method of claim 59, wherein transmitting the control message comprises:

transmitting the control message in each of the simultaneous transmissions.

62. The method of claim 59, wherein the control message comprises an indication that the apparatuses should not contend for a communication medium.

63. The method of claim 59, wherein the control message is transmitted in a header field of an Aggregate Physical Layer Protocol Data Unit (APPDU).

64. The method of claim 59, wherein the acknowledgement messages comprise Media Access Control (MAC) level acknowledgements.

65. The method of claim 59, wherein all the backoff values are different.

66. An apparatus for wireless communications, comprising:

a transmitter configured to transmit a control message to each of a plurality of apparatuses to receive simultaneous transmissions; and

a receiver configured to receive an acknowledgement message from each of the apparatuses, wherein the acknowledgement messages were transmitted after receiving the control message at the apparatuses, wherein

the transmitter is also configured to transmit, to the apparatuses in response to the acknowledgement messages, a backoff timing message with backoff values, wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before transmitting.

67. The apparatus of claim 66, wherein the backoff timing message is transmitted a Short Inter-Frame Space (SIFS) time duration after the reception of the acknowledgement messages.

68. The apparatus of claim 66, wherein the transmitter is also configured to transmit the control message in each of the simultaneous transmissions.

69. The apparatus of claim 66, wherein the control message comprises an indication that the apparatuses should not contend for a communication medium.

70. The apparatus of claim 66, wherein the control message is transmitted in a header field of an Aggregate Physical Layer Protocol Data Unit (APPDU).

71. The apparatus of claim 66, wherein the acknowledgement messages comprise Media Access Control (MAC) level acknowledgements.

72. The apparatus of claim 66, wherein all the backoff values are different.

73. An apparatus for wireless communications, comprising:

means for transmitting a control message to each of a plurality of apparatuses to receive simultaneous transmissions; and

means for receiving an acknowledgement message from each of the apparatuses, wherein the acknowledgement messages were transmitted after receiving the control message at the apparatuses, wherein

the means for transmitting is further configured to transmit, to the apparatuses in response to the acknowledgement messages, a backoff timing message with backoff values, wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before transmitting.

74. The apparatus of claim 73, wherein the backoff timing message is transmitted a Short Inter-Frame Space (SIFS) time duration after the reception of the acknowledgement messages.

75. The apparatus of claim 73, wherein the means for transmitting is further configured to transmit the control message in each of the simultaneous transmissions.

76. The apparatus of claim 73, wherein the control message comprises an indication that the apparatuses should not contend for a communication medium.

77. The apparatus of claim 73, wherein the control message is transmitted in a header field of an Aggregate Physical Layer Protocol Data Unit (APPDU).

78. The apparatus of claim 73, wherein the acknowledgement messages comprise Media Access Control (MAC) level acknowledgements.

79. The apparatus of claim 73, wherein all the backoff values are different.

80. A computer-program product for wireless communications, comprising a computer-readable medium comprising instructions executable to:

transmit a control message to each of a plurality of apparatuses to receive simultaneous transmissions;

receive an acknowledgement message from each of the apparatuses, wherein the acknowledgement messages were transmitted after receiving the control message at the apparatuses; and

transmit, to the apparatuses in response to the acknowledgement messages, a backoff timing message with backoff values, wherein the backoff values indicate how long the apparatuses should wait after receiving the simultaneous transmissions before transmitting.

81. An access point, comprising:

at least one antenna;

a transmitter configured to transmit via the at least one antenna a control message to each of a plurality of wireless nodes to receive simultaneous transmissions; and

a receiver configured to receive via the at least one antenna an acknowledgement message from each of the wireless nodes, wherein the acknowledgement messages were transmitted after receiving the control message at the wireless nodes, wherein

the transmitter is also configured to transmit, to the wireless nodes in response to the acknowledgement messages, a backoff timing message with backoff values, wherein the backoff values indicate how long the wireless nodes should wait after receiving the simultaneous transmissions before transmitting.