ADAPTIVE POWER CONTROL IN A RADIO COMMUNICATIONS SYSTEMS

• US 20020077138A1
• Filed: 03/15/1999
• Published: 06/20/2002
• Est. Priority Date: 03/15/1999
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: MULLER, WALTER, BARK, GUNNAR, RIMHAGEN, THOMAS
• Granted Patent: US 6,628,956 B2
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/242 taking into account path loss
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 52/28 using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/36 with a discrete range or set of values, e.g. step size, ramping or offsets

Abstract

Delays on a common radio communications channel employed by plural mobile stations to communicate with a base station located in a corresponding geographical cell area are minimized by adapting transmission power based on traffic conditions. For lower traffic loads, a higher transmission power is permitted. For higher traffic loads, a lower power level is set. A transmit power level is determined using a desired signal ratio, such as a target CIR, a transmission path loss over the radio communications channel, and an interference value. One or more adaptive power parameters are also employed in that determination to adapt the open loop power control based on one or more current communications conditions and/or characteristics of the mobile station. For example, an adaptive power parameter may be a function of a current interference in a base station cell either alone or in combination with a current interference in one or more neighboring cells. The adaptive power parameter may also account for a type of data packet connection to be employed between the mobile station and the base station after random access, a mobile station'"'"'s subscription, a current temperature of the mobile station, a current base station used by the mobile station, a current estimated path loss between the mobile station and base station, and/or other factors.

Claims

1. In a mobile communications system having plural base stations corresponding to coverage cells and plural mobile stations, a method for improving communications between a mobile station and a base station over a radio communications channel, comprising:

establishing a predetermined relationship between a desired communications signal and an interference signal;

determining an interference value corresponding to interference in one of the cells;

determining a signal loss factor associated with a radio path in the cell;

determining a power parameter; and

calculating a transmission power at which to transmit over the radio communications channel based on the predetermined relationship, the interference value, the signal loss factor, and the power parameter.

2. The method in claim 1, wherein the power parameter is an adaptive power offset.

3. The method in claim 1, wherein the power parameter is a function of traffic load in the one cell.

4. The method in claim 3, wherein the power offset is a function of interference in the one cell.

5. The method in claim 4, wherein the interference is in an uplink direction from mobile station to base station.

6. The method in claim 4, wherein the interference is a function of interference in the one cell and at least one neighboring cell.

7. The method in claim 3, further comprising:

for lower traffic loads, setting a higher power for transmissions over the communications channel.

8. The method in claim 3, further comprising:

for higher traffic loads, setting a lower power for transmissions over the communications channel.

9. The method in claim 1, wherein the radio communications channel is an access channel.

10. The method in claim 9, wherein the access channel is an uplink random access channel (RACH) from the mobile station to a base station in the cell.

11. The method in claim 9, wherein the access channel is a downlink forward access channel (FACH) from the base station to the mobile station.

12. The method in claim 1, wherein the predetermined relationship is a carrier-to-interference ratio determined at a base station.

13. The method in claim 1, wherein the path loss factor is the path loss factor determined on a channel between the mobile station and a base station in the cell.

14. The method in claim 1, wherein the power parameter is determined based on one or more mobile user specific factors.

15. The method in claim 14, wherein the one or more user specific parameters include a type of data connection that will be employed between the mobile station and the base station.

16. The method in claim 15, wherein the power parameter is larger when the type of date packet mode includes a dedicated connection dedicated to the mobile station and the power parameter is lower when the type of data packet mode includes a common connection shared by plural mobile stations.

17. The method in claim 14, wherein the one or more user specific parameters include a subscription associated with the mobile station.

18. The method in claim 1, wherein the power parameter is determined based on one or more equipment related factors.

19. The method in claim 18, wherein the one or more equipment related factors includes an error in the determined path loss factor or in the determined cell interference.

20. The method in claim 18, wherein the one or more equipment related factors includes a transmit power level error.

21. The method in claim 18, wherein the one or more equipment related factors includes a mobile station temperature.

22. The method in claim 21, further comprising:

detecting a current temperature of the mobile station, and

determining the power parameter corresponding to the detected current temperature.

23. The method in claim 18, wherein the one or more equipment related factors includes a compensation value for equipment-related inaccuracies and physical limitations.

24. The method in claim 1, further comprising:

calculating the transmission power based on plural power parameters.

26. The method in claim 25, further comprising:

for lower traffic loads, setting a higher power for transmission over the common radio channel.

27. The method in claim 25, further comprising:

for higher traffic loads, setting a lower power for transmission over the common radio channel.

29. The method in claim 28, wherein the radio communications channel is an uplink access channel.

30. The method in claim 28, wherein the radio communications channel is an downlink access channel.

31. The method in claim 28, wherein the open loop power control is based on a desired signal ratio, a transmission path loss over the radio communications channel, and an interference value.

32. The method in claim 31, wherein the communications channel provides communications between a base station having a corresponding cell area and one or more mobile stations, and the adaptive power parameter is a function of one or more specific characteristics of the mobile stations active in the cell.

33. The method in claim 31, wherein the communications channel provides communications between a base station having a corresponding cell area and one or more mobile stations, and wherein the adaptive power parameter is a function of traffic load in the cell.

34. The method in claim 31, wherein the communications channel provides communications between a base station having a corresponding cell area and one or more mobile stations, and wherein the adaptive power parameter is a function of interference in the cell and in a neighboring cell.

35. The method in claim 31, wherein the communications channel provides communications between a base station having a corresponding cell area and one or more mobile stations, and wherein the adaptive power parameter is a function of user specific factors.

36. The method in claim 31, wherein the communications channel provides communications between a base station having a corresponding cell area and one or more mobile stations, and wherein the adaptive power parameter is a function of equipment-related factors.

38. The radio station in claim 37, wherein the controller includes a transmit power controller coupled to the transmitter and a station controller controlling the transmitter, receiver, and transmit power controller.

39. The radio station in claim 37, wherein the radio station uses code division multiple access (CDMA) and the receiver is a RAKE receiver.

40. The radio station in claim 37, wherein the controller estimates a transmit power value and then modifies the estimated transmit power value using an offset that is based on the traffic load in the cell to produce the transmit power level.

41. The radio station in claim 40, wherein the estimated transmit power ({circumflex over (P)}_tx) value is determined in accordance with the following:

{circumflex over (P)}_tx=γ

_t+Î

_UL+{circumflex over (L)},

where γ

_t is a target carrier-to-interference ratio, Î

_UL is an estimated uplink interference value, and {circumflex over (L)} is an estimated path loss associated with the radio channel.

42. The radio station in claim 41, wherein the transmit power level (P_level) is determined in accordance with the following:

P_level−

{circumflex over (P)}_tx+Δ

,

where Δ

is an offset value.

43. The radio station in claim 42, wherein the radio station is a mobile station and the cell is associated with a base station.

44. The radio station in claim 43, wherein Δ

is a function of the uplink interference in the cell in which the mobile station is located.

45. The radio station in claim 43, wherein Δ

is a function of a current packet data mode of the mobile station.

46. The radio station in claim 43, wherein Δ

is a function of a current subscription of the mobile station.

47. The radio station in claim 43, wherein Δ

is a function of a current temperature of the mobile station.

48. The radio station in claim 43, wherein Δ

is a function of the current base station used for random accesses by the mobile station.

49. The radio station in claim 43, wherein Δ

is a function of the mobile station equipment.

50. The radio station in claim 43, wherein Δ

is a function of the interference in other cells adjacent to the cell in which the mobile station is located.

51. The radio station in claim 43, wherein Δ

is a function of an error between a target signal strength level value at which the base station desires to receive signals from the mobile station and an actual signal strength level value.

25. A method for minimizing delay on a common radio communications channel employed by plural mobile stations to communicate with a base station located in a corresponding geographical cell area by adapting transmission power based on a traffic load in the cell area.

28. A method for controlling transmission power on a radio communications channel, comprising:

providing open loop power control on the radio communications common channel;

introducing into the open loop power control on the radio communications channel an additional adaptive power parameter; and

controlling transmission power on the radio communications channel using the open loop power control including the adaptive power parameter.

37. A radio station capable of communicating over a radio channel associated with a geographical cell, comprising:

a transmitter for transmitting data packets over the radio channel;

a receiver for receiving data packets over the radio channel; and

a controller controlling the transmit power level of the transmitter for transmissions over the common radio channel based on traffic load in the geographical cell so that at lower traffic loads the transmit power level is higher and at higher traffic loads the transmit power level is lower.