Fast flow control methods for communication networks

• US 7,221,653 B2
• Filed: 07/30/2001
• Issued: 05/22/2007
• Est. Priority Date: 07/30/2001
• Status: Expired due to Fees

• Current Assignee: Optis Wireless Technology, LLC (Brevet Capital)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Vanghi, Vieri
• Primary Examiner(s): Nguyen; Chau
• Assistant Examiner(s): PARK, JUNG H
• Application Number:
  US09/918,020
• Publication Number:
  US 20030031130A1
• Time in Patent Office: 2,122 Days
• Field of Search: 370/252, 370/329, 370/468, 455/452.2, 455/452.1, 455/453, 455/454, 455/63.1, 455/67.11, 455/67.13
• US Class Current: 370/252
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 28/0236 radio quality, e.g. interference, losses or delay
• CPC Class Codes: H04W 28/0284 detecting congestion or overload during communication monitoring arrangements H04L43/00
• CPC Class Codes: H04W 28/10 Flow control between communication endpoints
• CPC Class Codes: H04W 28/22 Negotiating communication rate
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]

Abstract

Reverse link flow control in a high data rate network determines current reverse link data channel rates for access terminals served by a network sector to identify corresponding defined channel gains, which are used to rapidly and reliably estimate total sector interference on the reverse link. Total sector interference indicates reverse link capacity utilization, and when remaining capacity approaches a defined threshold, the sector sets an activity indicator to a busy state indicating reverse link congestion. This action causes at least some access terminals to reduce their reverse link data channel rate. Interference calculation techniques preferably involve baseband digital processing using defined channel gains, permitting rapid evaluation of reverse link capacity and quick, reliable activity indicator updating, which increases reverse link capacity utilization. These techniques may be applied to inter-sector control, wherein the reverse activity indicator status for one sector depends on interference in one or more other sectors.

Claims

1. A method of reverse link flow control for a sector in a high rate packet data network serving a plurality of access terminals, said method comprising:

determining an individual interference contribution of each access terminal served by said sector based on a reverse data channel rate of said access terminal by;

determining channel gains for selected reverse link channels from said access terminal; and

weighting said channel gains by a pilot signal-to-noise ratio (pilot SNR) for said access terminal;

estimating total sector interference for said sector based on said individual interference contributions of said access terminals; and

setting a reverse link flow control indicator regulating the reverse data channel rates used by said access terminals based on said total sector interference.

2. The method of claim 1 further comprising determining said pilot SNR by estimating a nominal pilot SNR value.

3. The method of claim 2 further comprising weighting said individual interference contribution by a scaling factor based on a packet error rate of said access terminal.

4. The method of claim 1 further comprising determining said pilot SNR by measuring pilot SNR for said access terminal.

5. The method of claim 1 wherein determining channel gains for selected reverse channels from said access terminal comprises determining a reverse data channel gain and a reverse data rate control channel gain.

6. The method of claim 5 wherein determining a reverse data channel gain and a reverse data rate control channel gain comprises accessing pre-defined channel gain value information.

7. The method of claim 6 wherein accessing pre-defined channel gain value information comprises accessing stored channel gain value information comprising predefined gain values corresponding to said reverse data channel gain and said reverse data rate control channel gain.

8. The method of claim 7 further comprising selecting one of a number of defined gain values stored for said reverse data channel gain in said stored channel gain value information based on said reverse data channel rate of said access terminal.

9. The method of claim 6 wherein an air interface standard used by said network specifies said channel gains for said selected reverse channels, and further comprising configuring said stored channel gain values based on said air interface.

10. The method of claim 1 wherein weighting said channel gains by a pilot signal-to-noise ratio (pilot SNR) for said access terminal comprises multiplying a sum of said channel gains for said selected reverse channels by said pilot SNR.

11. The method of claim 1 wherein estimating total sector interference for said sector based on said individual interference contributions of said access terminals comprises summing said individual contributions for all said access terminals served by said sector.

12. The method of claim 1 further comprising compensating said estimate of total interference for soft handoff, wherein one or more of said access terminals served by said sector may be in soft handoff with one or more other sectors in said network.

13. The method of claim 12 wherein compensating said estimate of total interference for soft handoff comprises scaling said individual contributions by a weighting factor based on packet error rates of said access terminals.

14. The method of claim 13 wherein scaling said individual contributions by a weighting factor based on packet error rates of said access terminals comprises:

determining a packet error rate of each access terminal;

setting said weighting factor based on said packet error rate; and

scaling said individual contribution of said access terminal by said weighting factor.

15. The method of claim 14 wherein setting said weighting factor based on said packet error rate comprises setting said weighting factor to a first value if said packet error rate is below an error threshold and to a second value if said packet error rate is said error threshold.

16. The method of claim 1 wherein setting a reverse link flow control indicator regulating the reverse data channel rates used by said access terminals based on said total sector interference comprises:

determining a remaining reverse capacity based on said total sector interference; and

setting said reverse flow control indicator to indicate a busy condition when said reverse capacity falls below a reserve capacity threshold.

17. The method of claim 1 wherein setting a reverse link flow control indicator regulating the reverse data channel rates used by said access terminals based on said total sector interference comprises setting said reverse flow indicator to indicate a busy condition when said estimate of total interference is above a first threshold, and setting said reverse flow indicator to indicate a not busy condition when said estimate of total interference returns below a second threshold lower than said first threshold.

18. The method of claim 1 further comprising sending said estimate of total interference to a central controller operative to perform inter-sector reverse link flow control based on said estimate of total interference from said sector and one or more other estimates of total interference from one or more other sectors in said network.

19. The method of claim 18 further comprising sending estimated frequency reuse efficiency to said central controller for use in inter-sector reverse link flow control.

20. The method of claim 19 further comprising determining said estimated frequency reuse efficiency for said sector by estimating a first number of access terminals contributing to outer-cell interference in said sector, and a second number of access terminals contributing to in-cell interference in said sector.

21. The method of claim 20 wherein estimating a first number of access terminals contributing to outer-cell interference in said sector, and a second number of access terminals contributing to in-cell interference in said sector comprises evaluating a pilot channel signal-to-noise ratio for each said access terminal to determine whether said access terminal belongs to said first number or said second number.

22. The method of claim 20 wherein estimating a first number of access terminals contributing to outer-cell interference in said sector, and a second number of access terminals contributing to in-cell interference in said sector comprises evaluating a packet error rate (PER) for each said access terminal to determine whether said access terminal belongs to said first number or said second number.

23. The method of claim 20 wherein determining said estimated frequency reuse efficiency for said sector by estimating a first number of access terminals contributing to outer-cell interference in said sector, and a second number of access terminals contributing to in-cell interference in said sector comprises computing a ratio of total interference to in-cell interference, wherein said total interference comprises total outer-cell interference and total in-cell interference, and further comprising computing said total outer-cell and total in-cell interference based on said first and second numbers.

24. The method of claim 23 wherein computing said outer-cell and in-cell interference based on said first and second numbers comprises summing individual interference contributions for said access terminals belonging to said first number as said total outer-cell interference.

25. The method of claim 23 wherein computing said outer-cell and in-cell interference based on said first and second numbers comprises summing individual interference contributions for said access terminals belonging to said second number as said total in-cell interference.

26. A method of reverse link flow control in a wireless communication network comprising a plurality of sectors, the method comprising:

regulating reverse link data rates for access terminals in a first sector in dependence on a measured reverse link loading of a second sector to reduce reverse link interference in said second sector caused at least in part by said access terminals controlled by said first sector; and

cooperatively regulating reverse link data rates for a plurality of access terminals served by a plurality of sectors in said network, including said first and second sectors, to improve reverse link capacity utilization for at least one of said plurality of sectors.

27. The method of claim 26 wherein regulating reverse link data rates for access terminals in a first sector in dependence on the reverse link loading of the second sector to reduce reverse link interference in said second sector caused at least in part by said access terminals controlled by said first sector comprises:

estimating total sector interference in said second sector; and

causing said first sector to reduce reverse link data rates for at least some of said access terminals controlled by said first sector if said sector interference in said second sector exceeds a defined threshold, thereby reducing said total sector interference in said second sector.

28. The method of claim 27 wherein estimating said total sector interference in said second sector comprises:

determining an individual interference contribution of each access terminal served by said sector based on a reverse data channel rate of said access terminal; and

estimating said total sector interference for said sector based on said individual interference contributions of said access terminals.

29. The method of claim 28 wherein determining an individual interference contribution of each access terminal served by said sector based on said reverse data channel rate of said access terminal comprises:

determining channel gains for selected reverse link channels from said access terminal; and

weighting said channel gains by a pilot signal-to-noise ratio (pilot SNR) for said access terminal.

30. The method of claim 29 wherein determining channel gains for selected reverse channels from said access terminal comprises determining a reverse data channel gain and a reverse data rate control channel gain.

31. The method of claim 30 wherein determining a reverse data channel gain and a reverse data rate control channel gain comprises accessing pre-defined channel gain value information.

32. The method of claim 27 wherein causing said first sector to reduce reverse link data rates for at least some of said access terminals controlled by said first sector comprises adjusting a defined threshold for total sector interference used by said first sector to regulate reverse link data rates of said access terminals served by said sector.

33. A method of reverse link flow control in a wireless communication network comprising a plurality of sectors, the method comprising:

receiving total sector interference estimates indicative of sector loading from a plurality of sectors within said network at a central processor;

controlling reverse link throughput in at least a first sector in dependence on said interference estimates of at least a second sector to reduce interference in at least said second sector; and

inter-dependently controlling reverse link throughputs in one or more of said plurality of sectors, including said first and second sectors, to reduce inter-sector interference.

34. The method of claim 33 wherein controlling reverse link throughput in at least a first sector in dependence on said interference estimates of at least a second sector to reduce interference in at least said second sector comprises adjusting one or more flow control parameters used by said first sector in regulating reverse link data rates of access terminals controlled by said first sector.

35. The method of claim 34 wherein adjusting one or more flow control parameters used by said first sector in regulating reverse link data rates of access terminals controlled by said first sector comprises adjusting one or more interference thresholds used by said first sector in determining whether a current level of estimated total sector interference for said first sector necessitates indicating a busy condition to said access terminals controlled by said first sector, which indication causes at least some of said access terminals to reduce their reverse link data rates.

36. The method of claim 35 wherein adjusting one or more interference thresholds used by said first sector comprises transferring one or more updated interference threshold values to said first sector.

37. The method of claim 33 wherein controlling reverse link throughput in at least a first sector in dependence on said interference estimates of at least a second sector to reduce interference in at least said second sector comprises causing a radio base station in said first sector to reduce reverse link data rates for at least some of said access terminals controlled by said first sector to reduce interference in said second sector.

38. The method of claim 33 further comprising inter-dependently controlling reverse link throughputs of said plurality of sectors to increase a total network reverse link throughput.

39. The method of claim 33 wherein controlling reverse link throughput in at least a first sector in dependence on said interference estimates of at least a second sector to reduce interference in at least said second sector comprises:

evaluating said total interference estimates from said plurality of sectors;

adjusting interference threshold values used by one or more of said plurality of sectors in regulating reverse link data rates of pluralities of access terminals respectively served by said one or more of said sectors to minimize inter-sector interference; and

sending said adjusted interference thresholds to respective ones of said one or more of

said sectors.

40. The method of claim 33 further comprising receiving frequency reuse efficiency estimates from said plurality of sectors.

41. The method of claim 40 further comprising controlling reverse link throughput in one or more sectors, including said first sector, in dependence on said interference estimates and said efficiency estimates from one or more other sectors, including said second sector.

42. The method of claim 40 further comprising:

identifying a sector in said plurality of sectors having a reserve reverse link capacity below a defined threshold, as indicated by said interference estimate for said sector, and having a high frequency reuse efficiency, as indicated by said efficiency estimate for said sector; and

causing one or more other sectors in said plurality of sectors that are adjacent to said identified sector to reduce their reverse link throughput, thereby reducing interference in said identified sector.

43. The method of claim 40 wherein receiving frequency reuse efficiency estimates from said plurality of sectors comprises receiving one of said efficiency estimates from a radio base station in each one of said plurality of sectors at a central processor in a base station controller controlling said radio base stations in said plurality of sectors.

44. The method of claim 43 wherein receiving said interference estimates from said plurality of sectors comprises receiving said interference estimates from said radio base stations.

45. The method of claim 44 wherein each one of said radio base stations regulates reverse link throughput for the corresponding sector based on setting a reverse activity indicator, and further comprising controlling reverse link throughput in one or more of said sectors in inter-dependent fashion based on said interference estimates and said efficiency estimates.

46. The method of claim 45 wherein controlling reverse link throughput in one or more of said sectors in inter-dependent fashion based on said interference estimates and said efficiency estimates comprises transmitting adjusted interference threshold values used by said radio base stations in setting said reverse activity indicator.

47. A radio base station regulating reverse link data rates for a plurality of access terminals, said radio base station comprising:

a plurality of radio interfaces to support a plurality of connections with said access terminals;

a processing system to estimate total sector interference by determining individual interference contributions for said plurality of access terminals using defined channel gain information;

a threshold detector to generate a control signal by evaluating said estimated total sector interference with respect to a capacity threshold; and

a reverse activity modulator to set a reverse activity indicator to a busy or not busy state responsive to said control signal.

48. The radio base station of claim 47 further comprising a demodulation circuit in each one of said radio interferences to provide pilot channel signal to noise ratio information to said processing system for the connection corresponding to said radio interference, and wherein said processing system uses said pilot channel signal to noise ratio information in determining said individual interference contributions for said connections.

49. The radio base station of claim 47 further comprising a storage element operative to be hold said defined channel gain information, thus permitting said processing system to access said defined channel gain information for estimating said individual interference contributions.

50. A base station controller for use in a wireless communication network employing reverse link flow control, said base station controller comprising a central processor programmed to:

receive estimates of reverse link loading for a sector from a plurality of radio base stations;

process said estimates of reverse link loading from said plurality of radio base stations to compute a flow control parameter for one or more of said radio base stations;

wherein said flow control parameter computed for each radio base station is dependent on an estimate of reverse link loading for a sector associated with at least one other radio base station;

receive frequency reuse efficiency estimates from said radio base stations;

identify one or more first radio base stations having high estimates of reverse link loading and high efficiency estimates; and

compute flow control parameters for one or more second radio base stations adjacent to said one or more first radio base stations, such that interference at said first radio base stations caused by access terminals controlled by said second radio base stations is reduced.

51. The base station controller of claim 50 wherein said central controller is further programmed to send said flow control parameters to said radio base stations.