Apparatus and method for controlling reverse link interference among access terminals in wireless communications

• US 7,647,065 B2
• Filed: 10/10/2007
• Issued: 01/12/2010
• Est. Priority Date: 02/27/2004
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Bhushan, Naga, Attar, Rashid Ahmed Akbar, Lott, Christopher Gerard, Au, Jean Put Ling
• Primary Examiner(s): Maung; Nay A
• Assistant Examiner(s): NGUYEN, TUAN HOANG
• Application Number:
  US11/870,278
• Publication Number:
  US 20080032734A1
• Time in Patent Office: 825 Days
• Field of Search: 455/11.1, 455/68, 455/69, 455/517, 455/522
• US Class Current: 455/522
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/22 Negotiating communication rate
• CPC Class Codes: H04W 52/14 Separate analysis of uplink or downlink
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/243 taking into account interferences

Abstract

In a wireless communication system, an apparatus and a method are provided for controlling reverse link interference among access terminals that are power controlled by a sector of a base station. In an embodiment, the maximum effective noise power spectral density is used as a parameter for controlling the level of reverse link loading, by setting a reverse activity bit (RAB) to signal the access terminals to reduce their data rates in order to minimize interference between the access terminals if the maximum effective noise power spectral density is above a predetermined threshold.

Claims

1. A method of controlling reverse link interference in a sector of a base station of a CDMA communication system, the method comprising:

for each access terminal of a plurality of access terminals in communication with the base station, determining a noise power spectral density at the base station (i) due to a thermal noise power spectral density and (ii) due to a sum of chip energy of selected channels of access terminals that are power controlled by the sector, thereby obtaining a plurality of determined noise power spectral densities, one determined noise power spectral density per said each access terminal of the plurality of access terminals in communication with the base station;

determining a maximum noise power spectral density among the plurality of determined noise power spectral densities; and

controlling reverse link power of one or more of the access terminals that are power controlled by the sector based upon the maximum noise power spectral density.

2. The method of claim 1, wherein the step of determining a noise power spectral density for said each access terminal comprises:

determining total received power spectral density at the base station; and

subtracting from the total received power spectral density chip energy received from the selected channels of the access terminals that are power controlled by the sector except for said each access terminal.

3. The method of claim 1, further comprising:

for said each access terminal, computing a ratio of the determined noise power spectral density to the thermal noise power spectral density.

4. The method of claim 1, wherein said selected channels do not comprise any pilot channels.

5. The method of claim 1, wherein said selected channels comprise at least one access terminal pilot channel.

6. The method of claim 1, further comprising:

performing pilot interference cancellation for at least some access terminal pilot channels.

7. The method of claim 1, further comprising:

performing interference cancellation for at least one data channel of the access terminals that are power controlled by the sector.

8. The method of claim 1, further comprising:

selecting the one or more of the access terminals from among the access terminals that are power controlled by the sector.

9. The method of claim 8, wherein the step of selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a filtered ratio of pilot chip energy to effective noise power spectral density per antenna; and

comparing the filtered ratio of said each access terminal of the one or more access terminals that are power controlled by the sector to a predetermined threshold.

10. The method of claim 9, wherein the step of selecting further comprises:

including in the one or more of the access terminals only access terminals having a filtered ratio of pilot chip energy to effective noise power spectral density per antenna higher than the predetermined threshold.

11. The method of claim 8, wherein the step of selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a state of a data request channel lock corresponding to said each access terminal of the one or more access terminals that are power controlled by the sector.

12. The method of claim 11, wherein the step of selecting further comprises:

including in the one or more of the access terminals only access terminals with set data request channel lock.

13. The method of claim 8, wherein the step of selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a filtered reverse link path loss from said each access terminal of the one or more access terminals that are power controlled by the sector to the base station; and

comparing the filtered reverse link path loss of said each access terminal of the one or more access terminals that are power controlled by the sector to a predetermined threshold.

14. The method of claim 13, wherein the step of selecting further comprises:

including in the one or more of the access terminals only access terminals with filtered reverse link path loss not greater than the predetermined threshold.

15. The method of claim 1, further comprising:

selecting the one or more of the access terminals from among all the access terminals that are power controlled by the sector, wherein the step of selecting is based on filtered ratios of pilot chip energy to effective noise power spectral density per antenna of each access terminal of the one or more of the access terminals.

16. The method of claim 1, further comprising:

selecting the one or more of the access terminals from among the access terminals that are power controlled by the sector, wherein the step of selecting is based on state of data request channel lock of each access terminal of the one or more of the access terminals.

17. The method of claim 1, further comprising:

selecting the one or more of the access terminals from among the access terminals that are power controlled by the sector, wherein the step of selecting is based on filtered reverse link path loss from each access terminal of the one or more access terminals that are power controlled by the sector to the base station.

18. The method of claim 1, further comprising:

imposing an upper threshold of a rise-over-thermal ratio of the sector to avoid overloading neighboring sectors.

19. The method of claim 1, wherein the step of controlling comprises signaling the one or more access terminals that are power controlled by the sector to lower data rates when the maximum noise power spectral density exceeds a predetermined threshold.

20. The method of claim 1, wherein the step of controlling comprises setting a reverse activity bit when the maximum noise power spectral density exceeds a predetermined threshold.

21. A base station in a sector of a CDMA communication system, the base station comprising:

an antenna;

a transceiver connected to the antenna; and

a computing device connected to the transceiver, wherein the computing device is configured to cause the base station to perform steps comprising;

for each access terminal of a plurality of access terminals in communication with the base station, determining a noise power spectral density at the base station (i) due to a thermal noise power spectral density and (ii) due to a sum of chip energy of selected channels of access terminals that are power controlled by the sector, thereby obtaining a plurality of determined noise power spectral densities, one determined noise power spectral density per said each access terminal of the plurality of access terminals in communication with the base station;

determining a maximum noise power spectral density among the plurality of determined noise power spectral densities; and

controlling reverse link power of one or more of the access terminals that are power controlled by the sector based upon the maximum noise power spectral density.

22. The base station of claim 21, wherein the step of determining a noise power spectral density for said each access terminal comprises:

determining total received power spectral density at the base station; and

subtracting from the total received power spectral density chip energy received from the selected channels of the access terminals that are power controlled by the sector except for said each access terminal.

23. The base station of claim 21, wherein the steps further comprise:

for said each access terminal, computing a ratio of the determined noise power spectral density to the thermal noise power spectral density.

24. The base station of claim 21, wherein said selected channels do not comprise any pilot channels.

25. The base station of claim 21, wherein said selected channels comprise at least one access terminal pilot channel.

26. The base station of claim 21, wherein the steps further comprise:

performing pilot interference cancellation for at least some access terminal pilot channels.

27. The base station of claim 21, wherein the steps further comprise:

performing interference cancellation for at least one data channel of the access terminals that are power controlled by the sector.

28. The base station of claim 21, wherein the steps further comprise:

selecting the one or more of the access terminals from among all the access terminals that are power controlled by the sector.

29. The base station of claim 28, wherein the step of selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a filtered ratio of pilot chip energy to effective noise power spectral density per antenna; and

comparing the filtered ratio of said each access terminal of the one or more access terminals that are power controlled by the sector to a predetermined threshold.

30. The base station of claim 29, wherein the step of selecting further comprises:

including in the one or more of the access terminals only access terminals having a filtered ratio of pilot chip energy to effective noise power spectral density per antenna higher than the predetermined threshold.

31. The base station of claim 28, wherein the step of selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a state of a data request channel lock corresponding to said each access terminal of the one or more access terminals that are power controlled by the sector.

32. The base station of claim 31, wherein the step of selecting further comprises:

including in the one or more of the access terminals only access terminals with set data request channel lock.

33. The base station of claim 28, wherein the step of selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a filtered reverse link path loss from said each access terminal of the one or more access terminals that are power controlled by the sector to the base station; and

comparing the filtered reverse link path loss of said each access terminal of the one or more access terminals that are power controlled by the sector to a predetermined threshold.

34. The base station of claim 33, wherein the step of selecting further comprises:

including in the one or more of the access terminals only access terminals with filtered reverse link path loss not greater than the predetermined threshold.

35. The base station of claim 21, wherein the steps further comprise:

selecting the one or more of the access terminals from among all the access terminals that are power controlled by the sector, wherein the step of selecting is based on filtered ratios of pilot chip energy to effective noise power spectral density per antenna of each access terminal of the one or more of the access terminals.

36. The base station of claim 21, wherein the steps further comprise:

selecting the one or more of the access terminals from among the access terminals that are power controlled by the sector, wherein the step of selecting is based on state of data request channel lock of each access terminal of the one or more of the access terminals.

37. The base station of claim 21, wherein the steps further comprise:

selecting the one or more of the access terminals from among the access terminals that are power controlled by the sector, wherein the step of selecting is based on filtered reverse link path loss from each access terminal of the one or more access terminals that are power controlled by the sector to the base station.

38. The base station of claim 21, wherein the steps further comprise:

imposing an upper threshold of a rise-over-thermal ratio of the sector to avoid overloading neighboring sectors.

39. The base station of claim 21, wherein the step of controlling comprises signaling the one or more access terminals that are power controlled by the sector to lower data rates when the maximum noise power spectral density exceeds a predetermined threshold.

40. The base station of claim 21, further comprising an RAB setter connected to the computing device, wherein computing device is configured to cause the RAB setter to set a reverse activity bit when the maximum noise power spectral density exceeds a predetermined threshold.

41. A base station in a sector of a CDMA communication system, the base station comprising:

an antenna;

a means for transmitting and receiving connected to the antenna; and

a means for computing connected to the means for transmitting and receiving, wherein the means for computing is configured to cause the base station to perform steps comprising;

for each access terminal of a plurality of access terminals in communication with the base station, step for determining a noise power spectral density at the base station (i) due to a thermal noise power spectral density and (ii) due to a sum of chip energy of selected channels of access terminals that are power controlled by the sector, thereby obtaining a plurality of determined noise power spectral densities, one determined noise power spectral density per said each access terminal of the plurality of access terminals in communication with the base station;

step for determining a maximum noise power spectral density among the plurality of determined noise power spectral densities; and

step for controlling reverse link power of one or more of the access terminals that are power controlled by the sector based upon the maximum noise power spectral density.

42. The base station of claim 41, wherein the step for determining a noise power spectral density for said each access terminal comprises:

determining total received power spectral density at the base station; and

subtracting from the total received power spectral density chip energy received from the selected channels of the access terminals that are power controlled by the sector except for said each access terminal.

43. The base station of claim 41, wherein the steps further comprise:

for said each access terminal, computing a ratio of the determined noise power spectral density to the thermal noise power spectral density.

44. The base station of claim 41, wherein said selected channels do not comprise any pilot channels.

45. The base station of claim 41, wherein said selected channels comprise at least one access terminal pilot channel.

46. The base station of claim 41, wherein the steps further comprise:

step for performing pilot interference cancellation for at least some access terminal pilot channels.

47. The base station of claim 41, wherein the steps further comprise:

step for performing interference cancellation for at least one non-pilot channel of the access terminals that are power controlled by the sector.

48. The base station of claim 41, wherein the steps further comprise:

step for selecting the one or more of the access terminals from among the access terminals that are power controlled by the sector.

49. The base station of claim 48, wherein the step for selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a filtered ratio of pilot chip energy to effective noise power spectral density per antenna; and

comparing the filtered ratio of said each access terminal of the one or more access terminals that are power controlled by the sector to a predetermined threshold.

50. The base station of claim 49, wherein the step for selecting further comprises:

including in the one or more of the access terminals only access terminals having a filtered ratio of pilot chip energy to effective noise power spectral density per antenna higher than the predetermined threshold.

51. The base station of claim 48, wherein the step for selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a state of a data request channel lock corresponding to said each access terminal of the one or more access terminals that are power controlled by the sector.

52. The base station of claim 51, wherein the step for selecting further comprises:

including in the one or more of the access terminals only access terminals with set data request channel lock.

53. The base station of claim 48, wherein the step for selecting comprises:

for each access terminal of the one or more access terminals that are power controlled by the sector, determining a filtered reverse link path loss from said each access terminal of the one or more access terminals that are power controlled by the sector to the base station; and

comparing the filtered reverse link path loss of said each access terminal of the one or more access terminals that are power controlled by the sector to a predetermined threshold.

54. The base station of claim 53, wherein the step for selecting further comprises:

including in the one or more of the access terminals only access terminals with filtered reverse link path loss not greater than the predetermined threshold.

55. The base station of claim 41, wherein the steps further comprise:

step for selecting the one or more of the access terminals from among all the access terminals that are power controlled by the sector, wherein the step for selecting is based on filtered ratios of pilot chip energy to effective noise power spectral density per antenna of each access terminal of the one or more of the access terminals.

56. The base station of claim 41, wherein the steps further comprise:

step for selecting the one or more of the access terminals from among the access terminals that are power controlled by the sector, wherein the step for selecting is based on state of data request channel lock of each access terminal of the one or more of the access terminals.

57. The base station of claim 41, wherein the steps further comprise:

step for, selecting the one or more of the access terminals from among the access terminals that are power controlled by the sector, wherein the step for selecting is based on filtered reverse link path loss from each access terminal of the one or more access terminals that are power controlled by the sector to the base station.

58. The base station of claim 41, wherein the steps further comprise:

step for imposing an upper threshold of a rise-over-thermal ratio of the sector to avoid overloading neighboring sectors.

59. The base station of claim 41, wherein the step for controlling comprises signaling the one or more access terminals that are power controlled by the sector to lower reverse link data rates when the maximum noise power spectral density exceeds a predetermined threshold.

60. The base station of claim 41, further comprising a means for setting reverse activity bit (RAB) connected to the means for computing, wherein the means for computing is configured to cause the means for setting RAB to set a reverse activity bit when the maximum noise power spectral density exceeds a predetermined threshold.

61. A processor-readable media including processor-executable instructions encoded thereon for performing a method of controlling reverse link interference in a sector of a base station of a CDMA communication system, the method comprising steps for:

for each access terminal of a plurality of access terminals in communication with the base station, determining a noise power spectral density at the base station (i) due to a thermal noise power spectral density and (ii) due to a sum of chip energy of selected channels of access terminals that are power controlled by the sector, thereby obtaining a plurality of determined noise power spectral densities, one determined noise power spectral density per said each access terminal of the plurality of access terminals in communication with the base station;

determining a maximum noise power spectral density among the plurality of determined noise power spectral densities; and

controlling reverse link power of one or more of the access terminals that are power controlled by the sector based upon the maximum noise power spectral density.