Power control of a multi-subchannel mobile station in a mobile communication system

• US 6,690,944 B1
• Filed: 04/12/1999
• Issued: 02/10/2004
• Est. Priority Date: 04/12/1999
• Status: Expired due to Term

• Current Assignee: Blackberry Limited
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Lee, Wookwon, Secord, Norman P.
• Primary Examiner(s): APPIAH, CHARLES NANA
• Application Number:
  US09/289,584
• Time in Patent Office: 1,765 Days
• Field of Search: 455/522, 455/69, 455/70, 455/127, 455/132-137, 455/101-103, 455/422, 370/318, 370/337, 370/355
• US Class Current: 455/522
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/228 using past power values or information
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment

Abstract

A closed loop power control apparatus is implemented within a basestation that receives a series of physical channels from a mobile station simultaneously in a DS-CDMA communication system such as those based on the cdma2000 specifications. This power control apparatus includes a series of Rakes that separate the code-subchannels, a series of SINR estimation devices that estimate the SINR for each of the code-subchannels, and a series of comparators thaw generate a multiple of power control bits that correspond to comparison results between the SINR estimates and a set of power threshold levels. These power control bits are transmitted to the mobile station and subsequently allow the mobile station to control the transmit powers for the physical channels individually.

Claims

1. A method of controlling a transmit power of a mobile station with a base station operable to receive a plurality of physical channels from the mobile station simultaneously, the method comprising for each power control period:

estimating a power characteristic of at least two of said physical channels, for each of at least two physical channels, the power characteristic being determined as a function of a signal power, a noise power and an interference power with the noise power and interference power being determined from a plurality of power samples from previous power control periods; and

controlling the transmit power of each of the plurality of physical channels at the mobile station by sending at least one power control command to the mobile station determined with use of the power characteristic estimates with an objective that at least a respective minimum quality of service of each physical channel is maintained.

2. A method according to claim 1, wherein the controlling the transmit power at the mobile station comprises generating a power control bit corresponding to each of the power characteristic estimates.

3. A method according to claim 1, wherein the estimating a power characteristic of at least two of said physical channels comprises estimating a power characteristic for each of said physical channels.

4. A method according to claim 3, wherein the power control commands comprise a power control bit corresponding to each of the power characteristic estimates.

5. A method according to claim 1, wherein the power characteristic that is estimated is a signal-to-interference-plus-noise ratio (SINR).

6. A method according to claim 1, wherein each of said physical channels is a code-multiplexed subchannel.

7. A method according to claim 1 further comprising establishing initial settings at the mobile station using open loop power control commands.

8. A method according to claim 7 further comprising determining power ratios which define desired transmit power ratios between various physical channels, and sending the power ratios to the mobile station.

9. A method according to claim 5 wherein the estimating a power characteristic comprises:

determining an interference-noise power, σ

_n², that depends on the determined noise power and interference power;

determining a signal energy, E_b, that depends on an overall signal power minus the interference-noise power; and

estimating the SINR by dividing the signal energy, E_b, by the interference-noise power.

10. A method of controlling the transit power of a mobile station that is operable to transmit a plurality of physical channels to a basestation simultaneously, the method comprising the steps of for a current power control period:

receiving power information from the basestation, the power information being based on a power characteristic of at least two of the plurality of physical channels estimated at the base station with the power characteristic being a function of a signal power, a noise power and an interference power, the noise power and interference power being determined from a plurality of power samples from previous power control periods; and

independently setting transmit powers corresponding to said physical channels in response to said power information with an objective that at least a respective minimum quality of service of each physical channel is maintained.

11. A method according to claim 10, wherein the power information is at least two power control bits and the independently setting transmit powers is in response to the power control bits.

12. A method according to claim 10, wherein the receiving power information from the basestation comprises receiving power control bits that correspond to each of said physical channels and the independently setting transmit powers comprises adjusting the transit powers corresponding to each of said physical channels in response to the received power control bits.

13. A method according to claim 10, wherein each of said physical channels is a code-multiplexed subchannel.

14. A method according to claim 10, wherein the plurality of physical channels comprise a plurality of periods of physical channels, each period comprising one or more physical channels of the same data rate.

15. A method according to claim 14, wherein the power information comprises a plurality of power control bits, each power control bit corresponding to a respective one of the periods of physical channels.

16. A method according to claim 10 wherein the power characteristic is a signal-to-interference-plus-noise ratio (SINR).

17. A method according to claim 16 wherein the SINR is determined according to $\frac{E_b}{{\sigma }_{}^{}}$

n2

wherein E_b is the desired signal energy and σ

_n² is an average interference-noise power.

18. A method of controlling a transmit power of a mobile station with a base station operable to receive simultaneously a plurality of physical channels with a data signal from a mobile station, the method comprising for a current power control period:

receiving the data signal from the mobile station and separating the respective physical channels within the data signal;

for each physical channel generating a power characteristic estimate for the physical channel, the power characteristic estimate being a function of a signal power, a noise power and an interference power with the noise power and interference power being determined from a plurality of power samples from previous power control periods;

generating at least one power control bit on the basis of the power characteristic estimates and with an objective that at least a respective minimum quality of service of each physical channel is maintained; and

controlling the transmit power at the mobile station of each physical channel by transmitting the at least one power control bit to the mobile station.

19. A method according to claim 18, wherein the power characteristic that is estimated is a signal-to-interference-plus-noise ratio (SINR).

20. A method according to claim 18, wherein each of said physical channels is a code-multiplexed subchannel.

21. A method according to claim 18, wherein transmitting the at least one power control bit comprises:

replacing normal data bits with the at least one power control bit at predetermined locations within a frame.

22. A method according to claim 18, wherein generating the at least one power control bit comprises:

for each physical channel comparing the power characteristic estimate to a respective power threshold level, generating a comparison.

23. A method according to claim 22, wherein the at least one power control bit is a single power bit;

and

wherein generating the single power control comprises combining all of the comparisons and generating a single power control bit.

24. A method according to claim 23 further comprising:

generating power ratios that indicate relative power levels for the physical channels using the physical channel power threshold levels; and

transmitting these power ratios to the mobile station.

25. A method according to claim 18, wherein generating the at least one power control bit comprises:

for each physical channel comparing the power characteristic estimate to respective dynamically adjustable power threshold level and generating a respective power control bit.

26. A method according to claim 25, wherein the at least one power control bit is a plurality of power control bits;

and

wherein the comparison for each physical channel is a respective one of the power control bits.

27. A method according to claim 25, further comprising dynamically updating the threshold levels.

28. A method according to claim 25 farther comprising:

for each physical channel demodulating the physical channel to produce a respective demodulated physical channel

for each demodulated physical channel, determining a frame quality corresponding to the demodulated physical channel; and

generating and updating a respective power threshold level determined with use of the frame quality.

29. A method according to claim 18, wherein generating the at least one power control bit comprises:

generating a combined power characteristic estimate using the power characteristic estimates; and

comparing the combined power characteristic estimate to a power threshold level to generate a single power control bit.

30. A method according to claim 29 further comprising:

separating a pilot channel from the data signal;

estimating the power characteristic of the separated pilot channel; and

generating the combined power characteristic estimate with use of the power characteristic estimate corresponding to the pilot channel.

31. A method according to claim 29 further comprising:

for each physical channel demodulating the physical channel to produce a demodulated physical channel;

for each demodulated physical channel determining a frame quality corresponding to the demodulated physical channel;

for each frame quality generating a physical channel power threshold level using the frame quality; and

generating a combined power threshold level that corresponds to the power threshold level using the physical channel power threshold levels.

32. A method according to claim 29 further comprising:

for each physical channel comprising the power characteristic estimate with one of a plurality of physical channel power threshold levels generating a comparison; and

transmitting the comparison as a physical channel power control bit to the mobile station.

33. A method according to claim 32 further comprising:

for each physical channel demodulating the physical channel to produce a demodulated physical channel;

determining a frame quality corresponding to the demodulated physical channel;

generating a physical channel power threshold level using the frame quality; and

generating a combined power threshold level that corresponds to the power threshold level using the physical channel power threshold levels.

34. A method according to claim 33 further comprising:

generating power ratios that indicate relative power levels for the physical channels using the physical channel power threshold levels; and

transmitting these power ratios to the mobile station.

35. A method according to claim 19 wherein the SINR is determined according to $\frac{E_b}{{\sigma }_{}^{}}$

n2

wherein E_b is the desired signal energy and σ

_n² is an average interference-noise power.