Method of power control for a wireless communication system having multiple information rates

• US 6,535,723 B1
• Filed: 03/15/1999
• Issued: 03/18/2003
• Est. Priority Date: 03/15/1999
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Weaver, Carl Francis, Salvarani, Alexandro Federico, Li, Quinn, Kamel, Raafat Edward, Jiang, Frances
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): CRAVER, CHARLES R
• Application Number:
  US09/267,998
• Time in Patent Office: 1,464 Days
• Field of Search: 455/422, 455/423, 455/424, 455/13.4, 455/38.3, 455/501, 455/504, 455/517, 455/522, 455/63, 455/67.3, 455/69, 455/67-- 6, 455/226--22, 455/232--24, 370/465-468
• US Class Current: 455/245.1
• CPC Class Codes: H04W 52/12 Outer and inner loops
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/265 taking into account the quality of service QoS
• CPC Class Codes: H04W 52/267 taking into account the information rate
• CPC Class Codes: H04W 52/36 with a discrete range or set of values, e.g. step size, ramping or offsets
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

A method of controlling the power in a wireless communication system. In one embodiment of the invention, a base station determines the information rate of a signal to be transmitted to a mobile station, and obtains the variable power control scaling factor based on this information rate. The base station then transmits the variable power control scaling factor to the mobile station. The mobile station determines a target signal quality measurement for a received signal from the base station, such as a target E_b/N₀, and scales the target E_b/N₀ by the variable power control scaling factor. The mobile station also obtains an information rate scaling factor based on the information rate of the received signal, and further scales the target E_b/N₀ by this information rate scaling factor. The mobile station then compares the target E_b/N₀ to a measured E_b/N₀ of the received signal. An increase in power of the received signal is requested when the measured E_b/N₀ of the received signal is smaller than the scaled E_b/N₀. A decrease in power of the received signal is requested when the measured E_b/N₀ of the received signal is larger than the scaled E_b/N₀. Providing the variable power control scaling factor to the mobile station allows frames having an information rate lower than the full rate to be transmitted at a power even lower than the power of a frame having an information rate equal to the full rate times the information scaling factor.

Claims

1. A method for controlling the power in a wireless communication system, the method comprising the steps of:

determining a target value of a signal quality parameter to achieve a required signal quality for a full information rate frame of data of a received signal;

determining a target value of the signal quality parameter for a fractional information rate frame of the received signal as a proportional adjustment to the full-rate target value, the proportional adjustment being a function of a fraction the fractional information rate frame bears to the full information rate;

adjusting the fractional-rate target value by a variable power control scaling factor, wherein the variable power control scaling factor represents a fraction by which the fractional-rate target value can be reduced while maintaining the required signal quality for the frame; and

evaluating a received value of the signal quality parameter for ones of power control groups in frames transmitted at the fractional information rate against the adjusted fractional-rate target value.

2. The method of claim 1, wherein the signal quality value is a signal to noise ratio.

3. The method of claim 1, wherein the signal quality value is an E_b/N_o.

4. The method of claim 1, wherein the evaluating step further comprises the steps of:

measuring a signal quality value of the received signal;

comparing the measured signal quality value of the received signal to the scaled target signal quality value;

requesting an increase in power of the received signal responsive to the measured signal quality value of the received signal being smaller than the scaled target signal quality value; and

requesting a decrease in power of the received signal responsive to the measured signal quality value of the received signal being larger than the scaled target signal quality value.

5. The method of claim 1, wherein the variable power control scaling factor is received in a message of the paging channel.

6. The method of claim 1, wherein the variable power control scaling factor is received in a message of the traffic channel.

7. The method of claim 1, wherein the scaling step operates on ones of power control group intervals in the frame.

8. A method for controlling transmitter power in a wireless system, the method comprising the steps of:

determining a target value of a signal quality parameter to achieve a required signal quality for a full information rate frame of data of a received signal;

determining a target value of the signal quality parameter for a fractional information rate frame of the received signal as a proportional adjustment to the full-rate target value, the fractional-rate target value being proportional to the full-rate target value in the proportion that the fractional information rate bears to the full information rate;

determining a variable power control scaling factor representing a factor by which the fractional-rate target value can be reduced while maintaining a required signal quality at the fractional information frame rate;

scaling the target signal quality parameter value for the fractional information rate by the variable power control scaling factor;

adjusting transmitter power for a power control interval in a fractional information rate frame as a function of a difference between a service quality parameter value measured for that interval and the scaled target signal quality parameter value.

9. The method of claim 8, wherein the variable power control scaling factor is transmitted in a message of the forward control channel.

10. The method of claim 8, (wherein the variable power control scaling factor is transmitted in a message of the paging channel.

11. The method of claim 8, wherein the variable power control scaling factor is transmitted in a message of the forward traffic channel.

12. The method of claim 11, wherein the forward traffic channel is a handoff direction message.

13. The method of claim 8, further comprising the step of scaling the transmitter power by the variable power control factor.

14. In a wireless communication system wherein information signals are transmitted at a full and one or more fractional information rates, and wherein target values of a signal quality parameter needed to achieve a specified signal quality are provided for a full-rate information frame and for at least one fractional-rate information frame, the fractional-rate target value being proportional to the full-rate target value in the proportion that the fractional information rate bears to the full information rate, a method for controlling transmission power in the wireless communication system comprising the steps of:

adjusting the fractional-rate target value by a variable power control scaling factor, wherein the variable power control scaling factor represents a fraction by which the fractional-rate target value can be reduced while maintaining a required signal quality for the frame; and

evaluating a received value of the signal quality parameter for ones of power control groups in frames transmitted at the fractional information rate against the adjusted fractional-rate target value.

15. The method of claim 14, wherein the signal quality value is a signal to noise ratio.

16. The method of claim 14, wherein the signal quality value is an E_b/N_o.

17. The method of claim 14, wherein the evaluating step further comprises the steps of:

requesting an increase in power of the received signal responsive to the received value of the signal quality parameter being smaller than the adjusted fractional-rate target value; and

requesting a decrease in power of the received signal responsive to the received value of the signal quality parameter being larger than the adjusted fractional-rate target value.

18. The method of claim 14, wherein the variable power control scaling factor is received in a message of the reverse pilot channel.

19. The method of claim 14, wherein the scaling step operates on ones of power control group intervals in the frame.