Methods and apparatus of power control in wireless communication systems

• US 7,420,939 B2
• Filed: 08/13/2003
• Issued: 09/02/2008
• Est. Priority Date: 08/13/2003
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Rangan, Sundeep, Hande, Prashanth, Fan, John L.
• Primary Examiner(s): Pham; Chi H.
• Assistant Examiner(s): Mills; Donald L
• Application Number:
  US10/641,308
• Publication Number:
  US 20050036441A1
• Time in Patent Office: 1,847 Days
• Field of Search: 370/315, 370/318, 370/328, 370/338, 370/436, 370/478, 455/13.4, 455/23, 455/42, 455/60, 455/127.1, 455/522
• US Class Current: 370/318
• CPC Class Codes: H04L 27/362 Modulation using more than one carrier, e.g. with quadrature carriers, separately amplitude modulated H04L27/366 takes precedence
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/56 Detection of errors of TPC bits
• CPC Class Codes: H04W 52/60 using different transmission rates for TPC commands

Abstract

The present invention involves apparatus and methods to perform wireless terminal transmission power control. The invention uses novel and highly efficient methods to: convey power control information, specify power control level adjustments, recognize power control information, limit interference in the power control signaling, and recognize corrupted power control signaling, thus conserving wireless terminal energy and minimizing power control signaling and associated bandwidth. Base stations send analog power control command signals, with a continuous range of control levels, to wireless terminals for transmission power adjustments. Power control signals include two components which can be used to convey information, e.g., power control commands, signal quality, device identity information. For zero power adjustment, the control component signal is not transmitted. For a non-zero adjustment, power control signals are sent using control ranges and limits, known to the base station and wireless terminal, with the scaling adjusted or synchronized based upon feedback information.

Claims

1. A communications method for use in an orthogonal frequency division multiplexed system, the method comprising:

modulating, using phase modulation, first control information on a first component of a single tone to generate a first single tone control signal, said first single tone control signal including the first component and a second component, said first and second components having a phase difference of 90 degrees, said second component communicating information which is separate from said first control information or being null; and

transmitting said first single tone control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period.

2. The method of claim 1, wherein said first control information is transmission power control information corresponding to a first wireless terminal.

3. The method of claim 1, wherein said first control information is transmission frequency control information corresponding to a first wireless terminal.

4. The method of claim 1, wherein said first control information is transmission timing control information corresponding to a first wireless terminal.

5. The method of claim 2, wherein said first single tone control signal indicates one of an increase and a decrease, said step of modulating including setting the phase of the first single tone control signal to a first value if said first single tone control signal indicates an increase and to a second value if said first single tone control signal indicates a decrease, said second value having a 180 degree difference from the first value.

6. The method of claim 1, wherein said first component is an In-phase component and said second component is a Quadrature component, said first control information being modulated on a first single one of said In-phase and Quadrature components, the method further comprising:

modulating second control information corresponding to a second wireless terminal on said single tone, said second control information being said separate information, said second control information being modulated on the second single one of said In-phase and Quadrature components, said second single one of said In-phase and Quadrature components being different from said first single one of said In-phase and Quadrature components.

7. The method of claim 5, further comprising operating said first wireless terminal to receive said first single tone control signal and adjusting a transmission power level as a function of the first control information modulated on said first single tone control signal.

8. The method of claim 6, wherein the second single one of said In-phase and Quadrature phase components is transmitted with no more than 10% of the power that is used to transmit said first single one of said In-phase and Quadrature components.

9. The method of claim 1, wherein the power transmitted on the second signal one of said In-phase and Quadrature components is zero.

10. The method of claim 6, wherein said step of modulating second control information includes performing an amplitude modulation operation to modulate said second control information on said second single one of said In-phase and Quadrature components, said modulation for said second single one of said In-phase and Quadrature components including assigning, as a function of said first control information, a single value from a set of at least 3 possible values.

11. The method of claim 10, wherein at least one of the 3 possible values is zero indicating no change in transmission power is to be made by said first wireless terminal.

12. The method of claim 10, wherein said set of possible values includes a predetermined interval of possible values.

13. The method of claim 1, further comprising:

modulating control information on a single tone indicating no change during a second period of time which is different from a first period of time corresponding to said first control information, said modulating generating a second single tone control signal, said second single tone control signal having an amplitude of zero; and

transmitting said second single tone control signal during a single orthogonal frequency division multiplexed symbol transmission time period.

14. The method of claim 6, wherein modulating said second control information includes performing amplitude modulation.

15. The method of claim 14, further comprising:

multiplying the amplitude modulated one of the In-phase and Quadrature components by a first scaling factor, said first scaling factor being a function of downlink quality report information received from the wireless terminal to which the modulated one of the In-phase and Quadrature components corresponds.

19. The method of claim 2, further comprising:

periodically transmitting a first set of said modulated power control signals corresponding to a first wireless terminal, at least some of said first set of modulated power control signals being modulated on different tones during different orthogonal frequency division multiplexed symbol transmission time periods.

20. The method of claim 19, wherein the tones used to modulate said first set of modulated power control signals is determined by a first predetermined hopping sequence.

21. The method of claim 20, wherein the first predetermined hopping sequence corresponds to a terminal identifier associated with the first wireless terminal.

24. The method of claim 1,

wherein the first component is a Quadrature signal component and the second component is an In-phase signal component;

wherein one of the In-phase and Quadrature signal components are not used, the method further comprising;

operating the wireless terminal to ignore the received power control information when the unused one of the In-phase and Quadrature components includes power above a preselected threshold.

25. The method of claim 6, further comprising:

transmitting a plurality of power control signals to said first wireless terminal, over a period of time; and

transmitting a periodic device identifier signal on the second single one of the In-phase and Quadrature signal components of at least 50% less frequently than the power control signals transmitted to said first wireless terminal.

28. The method of claim 6,

wherein one of the possible modulated signal values corresponds to a control command indicating no change in power;

and

wherein transmitting said first control information includes transmitting said single tone with zero power when said first control information indicates no change in power.

29. The method of claim 1, wherein said single tone control signal is transmitted in a first sector corresponding to a base station, the method comprising:

operating the base station to control a second sector adjacent to said first base station to leave the tone used by said first single tone control signal unused in said second sector when said first single tone control signal is transmitted.

16. A communications method for use in an orthogonal frequency division multiplexed system, the method comprising:

modulating first control information on a single tone to generate a first control signal; and

transmitting said first control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period;

wherein said first control information is transmission power control information corresponding to a first wireless terminal;

wherein said first control signal includes an In-phase component and a Quadrature component, said first control information being modulated on a first single one of said In-phase and Quadrature components;

wherein said modulating includes performing amplitude modulation, the method further comprising;

multiplying the amplitude modulated one of the In-phase and Quadrature components by a first scaling factor, said first scaling factor being a function of downlink quality report information so far received from the wireless terminal to which the modulated one of the In-phase and Quadrature components corresponds; and

increasing said first scaling factor in response to receiving downlink quality information indicative of a decrease in downlink channel quality and decreasing said first scaling factor in response to receiving downlink quality information indicative of a increase in downlink channel quality.

17. The method of claim 16, further comprising:

operating the wireless terminal to receive the scaled amplitude modulated signal; and

operating the wireless terminal to multiply the received signal by a second scaling factor that is a function of the downlink quality information previously sent by said wireless terminal.

18. The method of claim 17, decreasing the second scaling factor in response to an increase in downlink channel quality and increasing the second scaling factor in response to a decrease in downlink channel quality.

22. A communications method for use in an orthogonal frequency division multiplexed system, the method comprising:

modulating first control information on a single tone to generate a first control signal;

transmitting said first control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period;

wherein said first control information is transmission power control information corresponding to a first wireless terminal,

the method further comprising;

periodically transmitting a first set of said modulated power control signals corresponding to a first wireless terminal, at least some of said first set of modulated power control signals being modulated on different tones during different orthogonal frequency division multiplexed symbol transmission time periods;

wherein the tones used to modulate said first set of modulated power control signals is determined by a first predetermined hopping sequence; and

wherein said first wireless terminal uses a second predetermined hopping sequence to select tones for data communication purposes, the periodicity of the second predetermined hopping sequence being shorter than the periodicity of the first predetermined hopping sequence.

23. The method of claim 22, wherein the periodicity of the second predetermined hopping sequence is at most half of the periodicity of the first predetermined hopping sequence.

26. A communications method for use in an orthogonal frequency division multiplexed system, the method comprising:

modulating first control information on a single tone to generate a first control signal; and

transmitting said first control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period;

wherein said first control information is transmission power control information corresponding to a first wireless terminal;

wherein said first control signal includes an In-phase component and a Quadrature component, said first control information being modulated on a first single one of said In-phase and Quadrature components, the method further comprising;

transmitting a plurality of power control signals to said first wireless terminal over a period of time; and

transmitting a periodic device identifier signal on the second single one of the In-phase and Quadrature signal components of at least 50% less frequently than the power control signals transmitted to said first wireless terminal; and

wherein said single orthogonal frequency division multiplexed symbol transmission time period during which said periodic device identifier is transmitted is a function of a wireless device identifier unique to said first wireless terminal.

27. The method of claim 26, wherein the value of the periodic device identifier at any given time is a function of a wireless device identifier unique to said first wireless terminal.

30. A communications apparatus for use in an orthogonal frequency division multiplexed communications system including a wireless terminal, the communications apparatus comprising:

a modulator for modulating, using phase modulation, first control information on a first component of a single tone to generate a first single tone control signal, said first single tone control signal including the first component and a second component, said first and second components having a phase difference of 90 degrees, said second component communicating information which is separate from said first control information or being null; and

a transmitter coupled to said modulator for transmitting said first single tone control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period.

31. The communications apparatus of claim 30, wherein said first control information is one of transmission power control information, transmission frequency control information, and transmission timing control information corresponding to said wireless terminal.

32. The communications apparatus of claim 31,

wherein said first single tone control signal includes an In-phase component and a Quadrature component;

and

wherein said modulator is an amplitude modulator for amplitude modulating first control information on a first single one of said In-phase and Quadrature components.

33. The communications apparatus of claim 32, wherein said modulator further modulates second control information corresponding to a second wireless terminal on said single tone, on a second single one of said In-phase and Quadrature components, said second single one of said In-phase and Quadrature components being different from said first single one of said In-phase and Quadrature components.

34. The communications apparatus of claim 32, wherein the power transmitted on the second single one of said In-phase and Quadrature components is zero.

35. The communications apparatus of claim 32, wherein said modulator includes

means for mapping said first control information to a single value from a set of at least 3 possible values which may be amplitude modulated on said first one of said In-phase and Quadrature phase signal components;

and

wherein at least one of the 3 possible values is zero indicating no change in transmission power is to be made by said wireless terminal.

36. The communications apparatus of claim 32, further comprising:

a scaling device for multiplying the amplitude modulated one of the In-phase and Quadrature components by a first scaling factor, said first scaling factor being a function of downlink quality report information so far received from the wireless terminal to which the modulated one of the In-phase and Quadrature components corresponds.

38. The communications apparatus of claim 32, further comprising:

means for allocating tones used to transmit power control signals according to a first predetermined frequency hopping pattern said tones assigned according to the first frequency hopping pattern including a first set of modulated power control signals, at least some of said first set of modulated power control signals being modulated on different tones during different orthogonal frequency division multiplexed symbol transmission time periods.

39. The communications apparatus of claim 38, wherein the first predetermined hopping sequence corresponds to a terminal identifier associated with the wireless terminal.

41. The communications apparatus of claim 32, wherein said transmitter transmits a plurality of power control signals to said first wireless terminal over a period of time;

and

includes means for transmitting a periodic device identifier signal on the second single one of the In-phase and Quadrature signal components on less than 50% of the power control signals transmitted to said wireless terminal.

44. The communications apparatus of claim 32,

wherein one of the possible modulated signal values corresponds to a control command indicating no change in power;

and

wherein transmitting said first control information includes transmitting said signal tone with zero power when said first control information indicates no change in power.

45. The communications apparatus of claim 32, wherein said apparatus is a sectorized base station and wherein said transmitter is a transmitter in a sector of the sectorized base station, said apparatus including:

a control module for controlling a second sector adjacent to said first base station to leave the tone used by said first power control signal unused in said second sector when said first single tone control signal is transmitted.

37. A communications apparatus for use in an orthogonal frequency division multiplexed communications system including a wireless terminal, the communications apparatus comprising:

a modulator for modulating first control information on a single tone to generate a first control signal; and

a transmitter coupled to said modulator for transmitting said first control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period;

wherein said first control information is one of transmission power control information, transmission frequency control information, and transmission timing control information corresponding to said wireless terminal;

wherein said first control signal includes an In-phase component and a Quadrature component;

wherein said modulator is an amplitude modulator for amplitude modulating first control information on a first single one of said In-phase and Quadrature components, the apparatus further comprising;

a scaling device for multiplying the amplitude modulated one of the In-phase and Quadrature components by a first scaling factor, said first scaling factor being a function of downlink quality report information so far received from the wireless terminal to which the modulated one of the In-phase and Quadrature components corresponds;

means for increasing said first scaling factor in response to receiving downlink quality information indicative of a decrease in downlink channel quality and decreasing said first scaling factor in response to receiving downlink quality information indicative of a increase in downlink channel quality.

40. A communications apparatus for use in an orthogonal frequency division multiplexed communications system including a wireless terminal, the apparatus comprising:

a modulator for modulating first control information on a single tone to generate a first control signal; and

a transmitter coupled to said modulator for transmitting said first control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period;

wherein said first control information is one of transmission power control information, transmission frequency control information, and transmission timing control information corresponding to said wireless terminal;

a tone allocation module for allocating tones used to transmit power control signals according to a first predetermined frequency hopping pattern said tones assigned according to the first frequency hopping pattern including a first set of modulated power control signals, at least some of said first set of modulated power control signals being modulated on different tones during different orthogonal frequency division multiplexed symbol transmission time periods;

wherein said first control signal includes an In-phase component and a Quadrature component;

wherein said modulator is an amplitude modulator for amplitude modulating first control information on a first single one of said In-phase and Quadrature components; and

wherein tones are allocated for transmitting data to said wireless terminal according to a second predetermined hopping sequence, the periodicity of the second predetermined hopping sequence being shorter than the periodicity of the first predetermined hopping sequence.

42. A communications apparatus for use in an orthogonal frequency division multiplexed communications system including a wireless terminal, the apparatus comprising:

a modulator for modulating first control information on a single tone to generate a first control signal; and

a transmitter coupled to said modulator for transmitting said first control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period;

wherein said first control information is one of transmission power control information, transmission frequency control information, and transmission timing control information corresponding to said wireless terminal;

wherein said first control signal includes an In-phase component and a Quadrature component;

wherein said modulator is an amplitude modulator for amplitude modulating first control information on a first single one of said In-phase and Quadrature components;

wherein said transmitter transmits a plurality of power control signals to said first wireless terminal over a period of time; and

includes means for transmitting a periodic device identifier signal on the second single one of the In-phase and Quadrature signal components on less than 50% of the power control signals transmitted to said wireless terminal; and

wherein said single orthogonal frequency division multiplexed symbol transmission time period during which said periodic device identifier is transmitted is a function of a wireless device identifier unique to said wireless terminal.

43. A communications apparatus for use in an orthogonal frequency division multiplexed communications system including a wireless terminal, the apparatus comprising:

a modulator for modulating first control information a single tone to generate a first control signal; and

a transmitter coupled to said modulator for transmitting said first control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period;

wherein said first control information is one of transmission power control information, transmission frequency control information, and transmission timing control information corresponding to said wireless terminal;

wherein said first control signal includes an In-phase component and a Quadrature component;

wherein said modulator is an amplitude modulator for amplitude modulating first control information on a first single one of said In-phase and Quadrature components;

wherein said transmitter transmits a plurality of power control signals to said first wireless terminal over a period of time; and

includes means for transmitting a periodic device identifier signal on the second single one of the In-phase and Quadrature signal components on less than 50% of the power control signals transmitted to said wireless terminal; and

wherein the value of the periodic device identifier at any given time is a function of a wireless device identifier unique to said first wireless terminal.

46. A method of operating a wireless terminal in an orthogonal frequency division multiplexed communications system, the method comprising:

periodically receiving control signals corresponding to said wireless terminal, each control signal having control information of a first type, corresponding to one of three different values, first and third ones of said three different values being communicated using phase, a second one of said three different values being communicated as a null value; and

determining an adjustment to be made based on whether a received control signal communicates a first, second or third value, said adjustment corresponding to the control information type.

47. The method of claim 46, wherein said first type of information is one of power control information, timing control information and frequency control information.

48. The method of claim 46, wherein said first type of control information is power control information, the method further comprising:

operating the wireless terminal to perform a transmission power adjustment operation in response to the determined adjustment.

49. The method of claim 47, wherein a magnitude of approximately zero of a received control signal indicates no transmission power adjustment is to be made.

52. The method of claim 47, wherein each received control signal includes an In-phase component and a Quadrature phase component, the method further comprising:

ignoring a received control signal when the power of the second one of the In-phase and Quadrature phase components of said received control signal is above a preselected threshold.

53. The method of claim 52, wherein said threshold is a power level threshold corresponding to a preselected level of signal noise.

79. The method of claim 46, wherein the first and third ones of said three different values are communicated using first and third symbol values, said first and third symbol values differing in phase by 180 degrees, the second one of said three different values being communicated by a symbol value occurring on an axis extending between said first and third values, each of said first, second, and third values being on said axis.

50. A method of operating a wireless terminal in an orthogonal frequency division multiplexed communications system, the method comprising:

periodically receiving control signals corresponding to said wireless terminal, each control signal having control information of a first type, corresponding to one of at least three different values, said control signal being received on a first single one of an In-phase component and a Quadrature phase component of a single tone during a single orthogonal frequency division multiplexed symbol transmission time period;

determining from said first single one of said In-phase and Quadrature phase signal components of each received control signal an adjustment to be made, said adjustment corresponding to the control information type;

checking a signal transmitted on a second single one of the In-phase and Quadrature phase components to determine if said single orthogonal frequency division multiplexed symbol transmission time period during which said signal is transmitted and the value of said signal are a function of a wireless device identifier unique to said wireless terminal; and

wherein said first type of information is one of power control information, timing control information and frequency control information.

51. The method of claim 50, further comprising:

disregarding the received power control information when said checking indicates said signal on the second one of the In-phase and Quadrature components is not for said wireless terminal.

54. A wireless terminal for use in an orthogonal frequency division multiplexed communications system, the wireless terminal comprising:

means for receiving control signals corresponding to said wireless terminal, each control signal having control information of a first type, corresponding to one of at least three different values, first and third ones of said three different values being communicated using phase, a second one of said three different values being communicated as a null value; and

means for determining from the communicated value an adjustment to be made, said adjustment corresponding to the control information type.

55. The wireless terminal of claim 54, wherein said first type of information is one of power control information, timing control information and frequency control information.

56. The wireless terminal of claim 55, wherein said first type of control information is timing control information, the wireless terminal comprising:

means for performing a transmission power adjustment operation in response to receiving one of the first and third ones of said three different values.

57. The wireless terminal of claim 56, wherein a received null value indicates no transmission power adjustment is to be made.

60. The wireless terminal of claim 55, wherein one of the control signals is a power control signal and wherein the control information of the power control signal is communicated using a single one of an In-phase signal component and a Quadrature phase signal component of the power control signal, said wireless terminal further comprising:

means for disregarding a received power control signal when the power of the second one of the In-phase and Quadrature phase components of said signal is above a preselected threshold.

58. A wireless terminal for use in an orthogonal frequency division multiplexed communications system, the wireless terminal comprising:

means for receiving control signals corresponding to said wireless terminal, each control signal having control information of a first type, corresponding to one of at least three different values, amplitude modulated on a first single one of an In-phase component and a Quadrature phase component of a single tone during a single orthogonal frequency division multiplexed symbol transmission time period; and

means for determining from the magnitude of said first single one of said In-phase and Quadrature phase signal components of each received control signal an amount of an adjustment to be made, said adjustment corresponding to the control information type;

means for checking a signal transmitted on a second single one of the In-phase and Quadrature phase components to determine if said single orthogonal frequency division multiplexed symbol transmission time period during which said signal is transmitted and the value of said signal are a function of a wireless device identifier unique to said wireless terminal; and

wherein said first type of information is one of power control information, timing control information and frequency control information.

59. The wireless terminal 58, further comprising:

disregarding the received power control information when said checking indicates said signal on the second one of the In-phase and Quadrature components is not for said wireless terminal.

61. A device for use in an orthogonal frequency division multiplexed system, said device including a processor configured to control said device to implement a method, the method comprising:

modulating, using phase modulation, first control information on a first component of a single tone to generate a first single tone control signal, said first single tone control signal including the first component and a second component, said first and second components having a phase difference of 90 degrees, said second component communicating information which is separate from said first control information or being null; and

transmitting said first single tone control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period.

62. The device of claim 61, wherein said first control information is transmission power control information corresponding to a first wireless terminal.

63. The device of claim 61, wherein said first control information is transmission frequency control information corresponding to a first wireless terminal.

64. A computer readable medium embodying machine executable instructions for controlling a device for use in an orthogonal frequency division multiplexed system, wherein executing the machine executable instructions implements a process, the process comprising:

modulating, using phase modulation, first control information on a first component of a single tone to generate a first single tone control signal, said first single tone control signal including the first component and a second component, said first and second components having a phase difference of 90 degrees, said second component communicating information which is separate from said first control information or being null; and

transmitting said first single tone control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period.

65. The computer readable medium of claim 64, wherein said first control information is transmission power control information corresponding to a first wireless terminal.

66. The computer readable medium of claim 64, wherein said first control information is transmission frequency control information corresponding to a first wireless terminal.

67. A communications apparatus for use in an orthogonal frequency division multiplexed communications system including a wireless terminal, the communications apparatus comprising:

means for modulating, using phase modulation, first control information on a first component of a single tone to generate a first single tone control signal, said first single tone control signal including the first component and a second component, said first and second components having a phase difference of 90 degrees, said second component communicating information which is separate from said first control information or being null; and

means for transmitting said first single tone control signal using said single tone during a single orthogonal frequency division multiplexed symbol transmission time period.

68. The communications apparatus of claim 67, wherein said first control information is one of transmission power control information, transmission frequency control information, and transmission timing control information corresponding to said wireless terminal.

69. The communications apparatus of claim 68, wherein said first single tone control signal indicates one of an increase and a decrease, said step of modulating including setting the phase of the first single tone control signal to a first value if said first single tone control signal indicates an increase and to a second value if said first single tone control signal indicates a decrease, said second value having a 180 degree difference from the first value.

70. A wireless terminal for use in an orthogonal frequency division multiplexed communications system, said wireless terminal including a processor configured to control said wireless terminal to implement a method, the method comprising;

periodically receiving control signals corresponding to said wireless terminal, each control signal having control information of a first type, corresponding to one of three different values, first and third ones of said three different values being communicated using phase, a second one of said three different values being communicated as a null value; and

determining an adjustment to be made based on whether a received control signal communicates a first, second or third value, said adjustment corresponding to the control information type.

71. The wireless terminal of claim 70, wherein said first type of information is one of power control information, timing control information and frequency control information.

72. The wireless terminal of claim 70, wherein said first type of control information is power control information, and wherein the method further comprises:

performing a transmission power adjustment operation in response to the determined adjustment.

73. A computer readable medium embodying machine executable instructions for controlling a wireless terminal for use in an orthogonal frequency division multiplexed communications system, wherein executing the machine executable instructions implements a process, the process comprising:

periodically receiving control signals corresponding to said wireless terminal, each control signal having control information of a first type, corresponding to one of three different values, first and third ones of said three different values being communicated using phase, a second one of said three different values being communicated as a null value; and

determining an adjustment to be made based on whether a received control signal communicates a first, second or third value, said adjustment corresponding to the control information type.

74. The computer readable medium of claim 73, wherein said first type of information is one of power control information, timing control information and frequency control information.

75. The computer readable medium of claim 73, wherein said first type of control information is power control information, and wherein the method further comprises:

performing a transmission power adjustment operation in response to the determined adjustment.

76. A wireless terminal for use in an orthogonal frequency division multiplexed communications system, the wireless terminal comprising:

a receiver for receiving control signals corresponding to said wireless terminal, each control signal having control information of a first type, corresponding to one of at least three different values, first and third ones of said three different values being communicated using phase, a second one of said three different values being communicated as a null value; and

a determination module for determining from the communicated value, an adjustment to be made, said adjustment corresponding to the control information type.

77. The wireless terminal of claim 76, wherein said first type of information is one of power control information, timing control information and frequency control information.

78. The wireless terminal of claim 77, wherein said first type of control information is timing control information, the wireless terminal further comprising:

a power adjustment module for performing a transmission power adjustment operation in response to receiving one of the first and third ones of said three different values.