Restricting access point transmissions

• US 8,938,238 B2
• Filed: 11/02/2010
• Issued: 01/20/2015
• Est. Priority Date: 11/06/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Yavuz, Mehmet, Grokop, Leonard Henry, Patel, Chirag Sureshbhai, Nanda, Sanjiv
• Primary Examiner(s): Arevalo, Joseph
• Application Number:
  US12/917,627
• Publication Number:
  US 20110275361A1
• Time in Patent Office: 1,540 Days
• Field of Search: 455/502, 455/68, 455/522, 455/122.1, 455/552.1, 455/501, 455/517, 455/436, 455/75, 455/555, 455/456, 455/456.1, 455/161.3, 455/410, 455/411, 370/329, 370/229, 370/330, 370/331, 370/311, 370/338, 370/336, 370/356
• US Class Current: 455/436
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 48/04 based on user or terminal location or mobility data, e.g. moving direction, speed
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/244 Interferences in heterogeneous networks, e.g. among macro and femto or pico cells or other sector / system interference [OSI]
• CPC Class Codes: H04W 52/245 taking into account received signal strength
• CPC Class Codes: H04W 52/246 where the output power of a terminal is based on a path parameter calculated in said terminal
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

Transmissions by a first access point (e.g., a femto cell) are restricted upon detecting an access terminal in the vicinity of the first access point in the event the access terminal is communicating with a second access point (e.g., a macro cell). Upon detection of such an access terminal, the access terminal restricts transmission (e.g., beacon transmission) on a downlink carrier frequency on which the access terminal is actively receiving information from the second access point. This restriction of transmission by the access point may involve, for example, temporarily reducing transmit power, reducing the periodicity of transmission, or ceasing transmission.

Claims

1. A method of communication, comprising:

detecting, by a first access point, an access terminal located near the first access point, wherein the access terminal is communicating with a second access point, and wherein the first access point comprises a small coverage access point;

identifying, by the first access point, a downlink carrier frequency associated with at least the second access point on which the access terminal is communicating with the second access point, wherein the second access point comprises a macro coverage access point and measurements on the downlink carrier frequency are utilized to identify a corresponding uplink carrier frequency; and

restricting, by the first access point, transmission of first access point information on the identified downlink carrier frequency associated with at least the second access point as a result of the detection of the access terminal for reducing potential interference at the access terminal, wherein restricting the transmission comprises temporarily reducing transmit power used by the first access point on the identified downlink carrier frequency, and wherein a maximum transmit power value for the reduced transmit power is specified based on a measurement of received signal strength on an uplink carrier frequency.

2. The method of claim 1, wherein the detection of the access terminal comprises determining that the access terminal is subject to interference from beacons transmitted by the first access point on the downlink carrier frequency.

3. The method of claim 1, wherein the detection of the access terminal comprises determining that the access terminal is being or has been handed-over from the first access point.

4. The method of claim 1, wherein the detection of the access terminal comprises:

measuring received signal strength on the uplink carrier frequency; and

comparing the measured received signal strength with a threshold.

5. The method of claim 4, wherein, if the measured received signal strength is greater than or equal to the threshold, the identification of the downlink carrier frequency comprises identifying a downlink carrier frequency that is paired with the uplink carrier frequency.

6. The method of claim 4, further comprising synchronizing timing of the measurement of received signal strength with beacon transmission timing.

7. The method of claim 4, further comprising determining the threshold based on:

allowed path loss between the first access point and the access terminal; and

estimated transmit power used by the access terminal to communicate with the second access point.

8. The method of claim 4, further comprising determining the threshold by:

measuring received signal strength on the uplink carrier frequency over a period of time;

calculating a nominal received signal strength based on the measurement of received signal strength over the period of time; and

determining the threshold based on the nominal received signal strength.

9. The method of claim 4, further comprising determining the threshold by:

determining that the access terminal has been handed-over from the first access point;

measuring received signal strength on the uplink carrier frequency as a result of the determination that the access terminal has been handed-over; and

determining the threshold based on the measurement of received signal strength as a result of the determination that the access terminal has been handed-over.

10. The method of claim 1, wherein the detection of the access terminal comprises using a spreading code to detect a pilot signal from the access terminal.

11. The method of claim 1, further comprising determining that the first access point provides service for access terminals on the identified downlink carrier frequency, wherein the detection of the access terminal comprises:

measuring out-of-cell interference on the uplink carrier frequency associated with the downlink carrier frequency; and

comparing the out-of-cell interference with a threshold.

12. The method of claim 1, wherein the restriction of transmission comprises temporarily restricting beacon transmissions by the first access point on the identified downlink carrier frequency.

13. The method of claim 1, wherein the restriction of transmission comprises reducing a periodicity at which the first access point transmits signals on the identified downlink carrier frequency.

14. The method of claim 1, wherein the restriction of transmission comprises reducing how frequently the first access point transmits beacon signals on the identified downlink carrier frequency.

15. The method of claim 1, wherein the restriction of transmission comprises temporarily ceasing transmissions by the first access point on the identified downlink carrier frequency.

16. The method of claim 1, wherein the restriction of transmission is invoked for a defined period of time.

17. The method of claim 1, further comprising:

measuring received signal strength on the uplink carrier frequency associated with the downlink carrier frequency;

determining that the measured received signal strength is less than or equal to a threshold; and

terminating the restriction of transmission as a result of the determination that the measured received signal strength is less than or equal to the threshold.

18. An apparatus for communication, comprising:

a detection controller operable to detect an access terminal located near the apparatus, wherein the access terminal is communicating with an access point, and further operable to identify a downlink carrier frequency associated with at least the second access point on which the access terminal is communicating with the access point, wherein the second access point comprises a macro coverage access point and measurements on the downlink carrier frequency are utilized to identify a corresponding uplink carrier frequency; and

a transmission controller operable to restrict transmission of first access point information by the apparatus on the identified downlink carrier frequency associated with at least the second access point as a result of the detection of the access terminal for reducing potential interference at the access terminal, wherein to restrict the transmission, the transmission controller is further operable to temporarily reducing transmit power used by the first access point on the identified downlink carrier frequency, and wherein a maximum transmit power value for the reduced transmit power is specified based on a measurement of received signal strength on an uplink carrier frequency.

19. The apparatus of claim 18, wherein the detection of the access terminal comprises determining that the access terminal is subject to interference from beacons transmitted by the first access point on the downlink carrier frequency.

20. The apparatus of claim 18, wherein the detection of the access terminal comprises determining that the access terminal is being or has been handed-over from the first access point.

21. The apparatus of claim 18, wherein the detection of the access terminal comprises:

measuring received signal strength on the uplink carrier frequency; and

comparing the measured received signal strength with a threshold.

22. The apparatus of claim 21, wherein, if the measured received signal strength is greater than or equal to the threshold, the identification of the downlink carrier frequency comprises identifying a downlink carrier frequency that is paired with the uplink carrier frequency.

23. The apparatus of claim 21, wherein the detection controller is further operable to synchronize timing of the measurement of received signal strength with beacon transmission timing.

24. The apparatus of claim 21, wherein the detection controller is further operable to determine the threshold based on:

allowed path loss between the first access point and the access terminal; and

estimated transmit power used by the access terminal to communicate with the second access point.

25. The apparatus of claim 21, wherein the detection controller is further operable to determine the threshold by:

measuring received signal strength on the uplink carrier frequency over a period of time;

calculating a nominal received signal strength based on the measurement of received signal strength over the period of time; and

determining the threshold based on the nominal received signal strength.

26. The apparatus of claim 21, wherein the detection controller is further operable to determine the threshold by:

determining that the access terminal has been handed-over from the first access point;

measuring received signal strength on the uplink carrier frequency as a result of the determination that the access terminal has been handed-over; and

determining the threshold based on the measurement of received signal strength as a result of the determination that the access terminal has been handed-over.

27. The apparatus of claim 18, wherein the detection of the access terminal comprises using a spreading code to detect a pilot signal from the access terminal.

28. The apparatus of claim 18, wherein:

the detection controller is further operable to determine that the first access point provides service for access terminals on the identified downlink carrier frequency; and

the detection of the access terminal comprises;

measuring out-of-cell interference on the uplink carrier frequency associated with the downlink carrier frequency, and comparing the out-of-cell interference with a threshold.

29. The apparatus of claim 18, wherein the restriction of transmission comprises temporarily restricting beacon transmissions by the first access point on the identified downlink carrier frequency.

30. The apparatus of claim 18, wherein the restriction of transmission comprises reducing a periodicity at which the first access point transmits signals on the identified downlink carrier frequency.

31. The apparatus of claim 18, wherein the restriction of transmission comprises reducing how frequently the first access point transmits beacon signals on the identified downlink carrier frequency.

32. The apparatus of claim 18, wherein the restriction of transmission comprises temporarily ceasing transmissions by the first access point on the identified downlink carrier frequency.

33. The apparatus of claim 18, wherein the restriction of transmission is invoked for a defined period of time.

34. The apparatus of claim 18, wherein:

the detection controller is further operable to measure received signal strength on the uplink carrier frequency associated with the downlink carrier frequency;

the detection controller is further operable to determine that the measured received signal strength is less than or equal to a threshold; and

the transmission controller is further operable to terminate the restriction of transmission as a result of the determination that the measured received signal strength is less than or equal to the threshold.

35. An apparatus for communication, comprising:

means for detecting an access terminal located near the apparatus, wherein the access terminal is communicating with an access point, and wherein the first access point comprises a small coverage access point;

means for identifying a downlink carrier frequency associated with at least the second access point on which the access terminal is communicating with the access point, wherein the second access point comprises a macro coverage access point and measurements on the downlink carrier frequency are utilized to identify a corresponding uplink carrier frequency; and

means for restricting transmission of first access point information on the identified downlink carrier frequency associated with at least the second access point as a result of the detection of the access terminal for reducing potential interference at the access terminal, wherein the means for restricting the transmission comprises means for temporarily reducing transmit power used by the first access point on the identified downlink carrier frequency, and wherein a maximum transmit power value for the reduced transmit power is specified based on a measurement of received signal strength on an uplink carrier frequency.

36. The apparatus of claim 35, wherein the detection of the access terminal comprises determining that the access terminal is being or has been handed-over from the first access point.

37. The apparatus of claim 35, wherein the detection of the access terminal comprises:

measuring received signal strength on the uplink carrier frequency; and

comparing the measured received signal strength with a threshold.

38. The apparatus of claim 37, wherein, if the measured received signal strength is greater than or equal to the threshold, the identification of the downlink carrier frequency comprises identifying a downlink carrier frequency that is paired with the uplink carrier frequency.

39. The apparatus of claim 35, wherein the restriction of transmission comprises temporarily restricting beacon transmissions by the first access point on the identified downlink carrier frequency.

40. The apparatus of claim 35, wherein the restriction of transmission comprises reducing how frequently the first access point transmits beacon signals on the identified downlink carrier frequency.

41. The apparatus of claim 35, wherein the restriction of transmission comprises temporarily ceasing transmissions by the first access point on the identified downlink carrier frequency.

42. The apparatus of claim 35, wherein the restriction of transmission is invoked for a defined period of time.

43. The apparatus of claim 35, further comprising:

means for measuring received signal strength on the uplink carrier frequency associated with the downlink carrier frequency;

means for determining that the measured received signal strength is less than or equal to a threshold; and

means for terminating the restriction of transmission as a result of the determination that the measured received signal strength is less than or equal to the threshold.

44. A computer-program product, comprising:

a non-transitory computer-readable medium comprising code for causing a computer to;

detect, at a first access point, an access terminal located near the first access point, wherein the access terminal is communicating with a second access point, and wherein the first access point comprises a small coverage access point;

identify, at the first access point, a downlink carrier frequency associated with at least the second access point on which the access terminal is communicating with the second access point, wherein the second access point comprises a macro coverage access point and measurements on the downlink carrier frequency are utilized to identify a corresponding uplink carrier frequency; and

restrict, at the first access point, transmission of first access point information on the identified downlink carrier frequency associated with at least the second access point as a result of the detection of the access terminal for reducing potential interference at the access terminal, wherein restricting the transmission comprises temporarily reducing transmit power used by the first access point on the identified downlink carrier frequency, and wherein a maximum transmit power value for the reduced transmit power is specified based on a measurement of received signal strength on an uplink carrier frequency.

45. The computer-program product of claim 44, wherein the detection of the access terminal comprises determining that the access terminal is being or has been handed-over from the first access point.

46. The computer-program product of claim 44, wherein the detection of the access terminal comprises:

measuring received signal strength on the uplink carrier frequency; and

comparing the measured received signal strength with a threshold.

47. The computer-program product of claim 46, wherein, if the measured received signal strength is greater than or equal to the threshold, the identification of the downlink carrier frequency comprises identifying a downlink carrier frequency that is paired with the uplink carrier frequency.

48. The computer-program product of claim 44, wherein the restriction of transmission comprises temporarily restricting beacon transmissions by the first access point on the identified downlink carrier frequency.

49. The computer-program product of claim 44, wherein the restriction of transmission comprises reducing how frequently the first access point transmits beacon signals on the identified downlink carrier frequency.

50. The computer-program product of claim 44, wherein the restriction of transmission comprises temporarily ceasing transmissions by the first access point on the identified downlink carrier frequency.

51. The computer-program product of claim 44, wherein the restriction of transmission is invoked for a defined period of time.

52. The computer-program product of claim 44, wherein the computer-readable medium further comprises code for causing the computer to:

measure received signal strength on the uplink carrier frequency associated with the downlink carrier frequency;

determine that the measured received signal strength is less than or equal to a threshold; and

terminate the restriction of transmission as a result of the determination that the measured received signal strength is less than or equal to the threshold.

53. A method of communication, comprising:

detecting an access terminal at a first access point, wherein the detection of the access terminal comprises;

measuring received signal strength on an uplink carrier frequency; and

comparing the measured received signal strength with a threshold, wherein the threshold is determined by;

measuring received signal strength on the uplink carrier frequency over a period of time;

calculating a nominal received signal strength based on the measurement of received signal strength over the period of time; and

determining the threshold based on the nominal received signal strength;

identifying a downlink carrier frequency on which the access terminal is actively receiving information from a second access point; and

restricting transmission by the first access point on the identified downlink carrier frequency as a result of the detection of the access terminal.