Remote transmitter power control in a contention based multiple access system

• US 5,604,730 A
• Filed: 07/25/1994
• Issued: 02/18/1997
• Est. Priority Date: 07/25/1994
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr.
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): VU, HUY DUY
• Application Number:
  US08/280,095
• Time in Patent Office: 939 Days
• Field of Search: 370/18, 370/13, 370/17, 370/95.1, 370/95.2, 370/95.3, 370/110.1, 370/77, 455/38.3, 455/69, 455/70, 455/92, 455/68, 455/95, 375/200, 375/205, 375/206, 375/208, 340/825.08
• US Class Current: 370/252
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels

Abstract

The power control process of the present invention enables a base station communicating over a forward packet channel to a mobile radio to control the power of the mobile radio transmitting over a reverse packet channel to the base station. The base station maintains a maximum energy per bit to total interference spectral density ratio threshold for the reverse channel as well as a desired threshold that results in a low frame error rate. By comparing each radiotelephone'"'"'s estimated energy per bit to total interference spectral density ratio to the desired and maximum thresholds, power control commands to increase or decrease the radiotelephone'"'"'s transmit power are generated depending on the outcome of the comparison.

Claims

1. A method for controlling transmit power of a plurality of radios, the plurality of radios communicating with a base station, the method comprising the steps of:

the base station determining the transmit power required from each radio of the plurality of radios;

the base station instructing more than one of the plurality of radios to monitor a single power control bit stream; and

the base station transmitting said single power control bit stream to the more than one of the plurality of radios to instruct each of the more than one of the plurality of radios to alter its transmit power in response to the required transmit power.

2. The method of claim 1 wherein the step of determining the transmit power comprises the steps of:

determining a first signal quality threshold;

determining a second signal quality threshold;

determining a signal quality metric for each radio of the plurality of radios; and

comparing the signal quality metrics for the plurality of radios to the first and second signal quality thresholds.

3. The method of claim 2 wherein the signal quality metric is an energy per bit to total interference spectral density ratio.

4. The method of claim 2 and further including the steps of:

increasing the transmit power of a radio having a signal quality metric that is less than the first signal quality threshold; and

decreasing the transmit power of a radio having a signal quality metric that is greater than the second signal quality threshold.

5. The method of claim 2 wherein the first signal quality threshold is a minimum signal quality threshold and the second signal quality threshold is a maximum signal quality threshold.

6. A method for controlling a power output of a remote transmitter in a first mobile radio of a plurality of mobile radios, the first mobile radio receiving signals from a base station over a forward channel wherein said forward channel includes a first slot assigned to at least said first mobile radio and a second slot assigned to at least one other of said plurality of mobile radios, the base station receiving signals from the first mobile radio over a reverse channel, the method comprising the steps of:

determining a maximum reverse channel signal quality metric;

determining a desired reverse channel signal quality metric;

determining a reverse channel signal quality metric for each of the plurality of mobile radios, thus creating a plurality of reverse channel signal quality metrics;

determining a minimum reverse channel signal quality metric of the plurality of mobile radios;

summing the plurality of reverse channel signal quality metrics; and

the base station instructing the first mobile radio to monitor transmission of power control information in said first slot, said power control information instructing the remote transmitter to decrease the power output if the sum of the reverse channel signal quality metrics is greater than or equal to the maximum reverse channel signal quality metric or the minimum reverse channel signal quality metric is greater than the desired reverse channel signal quality metric.

7. The method of claim 6 and further including the step of the base station adjusting a minimum reverse channel energy per bit to total interference spectral density ratio depending on reverse channel conditions.

8. The method of claim 6 and further including the step of adjusting a maximum reverse channel energy per bit to total interference spectral density ratio in response to an increase or decrease in the quantity of said plurality of mobile radios.

9. The method of claim 6 wherein the mobile radio is a code division multiple access radiotelephone and the base station is a code division multiple access base station.

10. The method of claim 6 wherein the signal quality metric is an energy per bit to total interference spectral density ratio.

11. The method of claim 10 wherein the energy per bit to total interference spectral density ratio is ^Eb /_Io.

12. A method for controlling a power output of a remote transmitter in a first mobile radio of a plurality of mobile radios, the first mobile radio receiving signals from a base station over a forward channel, the base station receiving signals from the first mobile radio over a reverse channel, the method comprising the steps of:

determining a maximum reverse channel signal quality metric;

determining a desired reverse channel signal quality metric;

determining a reverse channel signal quality metric for each of the plurality of mobile radios, thus creating a plurality of reverse channel signal quality metrics;

determining a minimum reverse channel signal quality metric of the plurality of mobile radios;

summing the plurality of reverse channel signal quality metrics; and

the base station instructing the remote transmitter to monitor power control information associated with a predefined slot of said forward channel, said power control information instructing the remote transmitter to increase the power output if the sum of the reverse signal quality metrics is less than the maximum reverse channel signal quality metric.

13. The method of claim 12 and further including the step of the base station adjusting a minimum reverse channel energy per bit to total interference spectral density ratio depending on reverse channel conditions.

14. The method of claim 12 and further including the step of adjusting a maximum reverse channel energy per bit to total interference spectral density ratio in response to an increase or decrease in the quantity of the plurality of radiotelephones.

15. A method for controlling a power output of a remote transmitter in a first mobile radio of a plurality of mobile radios, the first mobile radio receiving signals from a base station over a forward channel, the base station receiving signals from the first mobile radio over a reverse channel, the method comprising the steps of:

determining a maximum reverse channel energy per bit to total interference spectral density ratio;

determining a desired reverse channel energy per bit to total interference spectral density ratio;

determining a reverse channel energy per bit to total interference spectral density ratio for each of the plurality of mobile radios, thus creating a plurality of reverse channel energy per bit to total interference spectral density ratios;

determining a minimum reverse channel energy per bit to total interference spectral density ratio of the plurality of mobile radios;

summing the plurality of reverse channel energy per bit to total interference spectral density ratios; and

the base station instructing the remote transmitter to monitor power control information associated with a predefined slot of said forward channel, said power control information instructing the remote transmitter to increase the power output if the minimum reverse energy per bit to total interference spectral density ratio is less than or equal to the desired reverse channel energy per bit to total interference spectral density ratio.

16. A method for controlling power output of a first remote transmitter of a plurality of remote transmitters, each remote transmitter being part of a mobile radiotelephone, the plurality of mobile radiotelephones receiving data packets from a cellular base station over a forward channel, the cellular base station receiving data packets from the plurality of mobile radiotelephones over a reverse channel, the reverse channel having a maximum energy per bit to total interference spectral density ratio, the data packets being comprised of frames, the method comprising the steps of:

determining a desired reverse channel energy per bit to total interference spectral density ratio;

determining a energy per bit to total interference spectral density ratio on the reverse channel for each of the remote transmitters, thereby creating a plurality of energy per bit to total interference spectral density ratios;

summing the plurality of energy per bit to total interference spectral density ratios to produce a summation value;

determining a minimum reverse channel energy per bit to total interference spectral density ratio for the plurality of mobile radiotelephones;

comparing the maximum reverse channel energy per bit to total interference spectral density ratio to the summation value;

comparing the minimum reverse channel energy per bit to total interference spectral density ratio to the desired energy per bit to total interference spectral density ratio; and

the base station instructing the first remote transmitter to decrease power if the summation value is greater than or equal to the maximum reverse channel energy per bit to total interference spectral density ratio or the minimum reverse channel energy per bit to total interference spectral density ratio is greater than the desired reverse channel energy per bit to total interference spectral density ratio.

17. The method of claim 16 wherein each of the energy per bit to total interference spectral density ratios is determined by an ^Eb /_Io of the reverse channel.

18. The method of claim 16 wherein each of the energy per bit to total interference spectral density ratios is determined by a ^Pr /_No of the reverse channel.

19. The method of claim 16 wherein each of the energy per bit to total interference spectral density ratios is determined by a scaled version of an ^Eb /_Io of the reverse channel.

20. A method for controlling power output of a first remote transmitter of a plurality of remote transmitters, each remote transmitter being part of a mobile radiotelephone, the plurality of mobile radiotelephones receiving data packets from a cellular base station over a forward channel, the cellular base station receiving data packets from the plurality of mobile radiotelephones over a reverse channel, the reverse channel having a maximum energy per bit to total interference spectral density ratio, the data packets being comprised of frames, the method comprising the steps of:

determining a desired reverse channel energy per bit to total interference spectral density ratio;

determining a energy per bit to total interference spectral density ratio on the reverse channel for each of the remote transmitters, thereby creating a plurality of energy per bit to total interference spectral density ratios;

summing the plurality of energy per bit to total interference spectral density ratios to produce a summation value;

determining a minimum reverse channel energy per bit to total interference spectral density ratio for the plurality of mobile radiotelephones;

comparing the maximum reverse channel energy per bit to total interference spectral density ratio to the summation value;

comparing the minimum reverse channel energy per bit to total interference spectral density ratio to the desired energy per bit to total interference spectral density ratio; and

the base station instructing the first remote transmitter to increase power if the summation value is less than the maximum reverse channel energy per bit to total interference spectral density ratio and the minimum reverse channel energy per bit to total interference spectral density ratio is less than or equal to the desired reverse channel energy per bit to total interference spectral density ratio.

21. The method of claim 20 and further including the step of the base station adjusting the minimum reverse channel energy per bit to total interference spectral density ratio depending on reverse channel conditions.

22. The method of claim 20 and further including the step of adjusting the maximum reverse channel energy per bit to total interference spectral density ratio in response to an increase or decrease in the quantity of the plurality of radiotelephones.

23. A method for controlling transmit power of a plurality of radios, the plurality of radios communicating with a base station, the method comprising the steps of:

the base station determining the transmit power required from each radio of the plurality of radios;

the base station transmitting a power control message multiplexed into a series of power control slots, each of said power control slots including power control information instructing each radio within an associated subset of said plurality of radios to alter its transmit power;

the base station instructing each radio within the same said associated subset to monitor said power control information in a same one of said power control slots.

24. A method for controlling transmit power of a plurality of radios using a power control message provided by a base station, the method comprising the steps of:

receiving, at more than one of said plurality of radios, instructions to monitor the same selected portion of said power control message; and

receiving, at said more than one of said plurality of radios, power control information within said same selected portion of said power control message, said power control information instructing each of said more than one of said plurality of radios to alter its transmit power in response to a required transmit power.

25. A method for controlling transmit power of a plurality of radios using a power control message provided by a base station, the method comprising the steps of:

transmitting, from said base station, instructions indicating that a subset said radios monitor the same selected portion of said power control message; and

transmitting, from said base station, power control information within said same selected portion of said power control message, said power control information indicating that transmission power of each of said more than one of said plurality of radios should be altered in response to a required transmit power.

26. A method for controlling transmit power of a plurality of radios, the plurality of radios communicating with a base station, the method comprising the steps of:

the base station determining the transmit power required from each radio of the plurality of radios;

the base station instructing a first subset of said plurality of radios to monitor a first power control bit stream, and a second subset of said plurality of radios to monitor a second power control bit stream; and

the base station transmitting said first and said second power control bit streams to instruct each of the plurality of radios in the first and second subsets of said plurality of radios to alter its transmit power in response to the required transmit power.

27. A method for controlling transmit power of a plurality of radios, the plurality of radios communicating with a base station, the method comprising the steps of:

the base station determining the transmit power required over a reverse channel from each radio of the plurality of radios; and

the base station transmitting a single power control bit stream to the more than one of said plurality of radios to instruct each of the more than one of said plurality of radios to alter its transmit power in response to the required transmit power and in response to a maximum total reverse channel signal quality metric;

wherein said maximum total reverse channel signal quality metric is set based upon a sum of reverse channel signal quality metrics associated with said plurality of radios.

28. A method for controlling a power output of a remote transmitter in a first mobile radio of a plurality of mobile radios, the first mobile radio receiving signals from a base station over a forward channel, the base station receiving signals from the first mobile radio over a reverse channel, the method comprising the steps of:

determining a reverse channel signal quality metric for each of the plurality of mobile radios, thus creating a plurality of reverse channel signal quality metrics;

summing the plurality of reverse channel signal quality metrics; and

the base station instructing the remote transmitter to decrease the power output at least if the sum of the reverse channel signal quality metrics is greater than or equal to a maximum reverse channel signal to noise ratio.

29. The method of claim 28 further including the steps of:

determining a minimum reverse channel signal quality metric of the first mobile radio; and

the base station instructing the remote transmitter to decrease the power output if the minimum reverse channel signal quality metric is greater than a desired reverse channel signal quality metric.