Fast forward link power control for CDMA system

• US 6,768,727 B1
• Filed: 11/09/2000
• Issued: 07/27/2004
• Est. Priority Date: 11/09/2000
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Khayrallah, Ali, Atarius, Roozbeh, Sourour, Essam
• Primary Examiner(s): Olms, Douglas
• Assistant Examiner(s): Pizarro, Ricardo M.
• Application Number:
  US09/711,219
• Time in Patent Office: 1,356 Days
• Field of Search: 370/335, 370/342, 370/336, 370/337, 370/338, 370/363, 370/344, 370/345, 370/252, 370/206, 370/208, 455/522
• US Class Current: 370/335
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/20 using error rate
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity
• CPC Class Codes: H04W 52/58 Format of the TPC bits

Abstract

A method of forward link power control in a CDMA mobile communication system is adapted for diversity transmission. First and second diversity signals are transmitted from a base station to a mobile terminal. The mobile terminal derives first and second channel quality estimates associated with the first and second diversity signals respectively. The mobile terminal uses the channel quality estimates to derive first and second power control codes which it transmits to said base station. The base station adjusts the transmit power of first and second antennas associated with the base station based on the first and second power control codes, respectively.

Claims

1. A method of forward link power control implemented in a mobile terminal, said method comprising:

receiving first and second diversity signals transmitted by a base station;

deriving a first channel quality estimate based on said first diversity signal;

deriving a second channel quality estimate based on said second diversity signal;

determining a first power control code based on said first channel quality estimate;

determining a second power control code based on said second channel quality estimate; and

transmitting said first power control code from said mobile terminal to said base station;

transmitting said second power control code from said mobile terminal to said base station.

2. The method of claim 1 wherein deriving said first channel quality estimate based on said first diversity signal comprises determining a frame error rate associated with said first diversity signal.

3. The method of claim 1 wherein deriving said first channel quality estimate based on said first diversity signal comprises determining a signal-to-interference ratio associated with said first diversity signal.

4. The method of claim 1 wherein deriving said first channel quality estimate based on said first diversity signal comprises determining a channel gain associated with said first diversity signal.

5. The method of claim 1 wherein deriving said second channel quality estimate based on said second diversity signal comprises determining a frame error rate associated with said second diversity channel.

6. The method of claim 1 wherein deriving said second channel quality estimate based on said second diversity signal comprises determining a signal-to-interference ratio associated with said second diversity signal.

7. The method of claim 1 wherein deriving said second channel quality estimate based on said second diversity signal comprises determining a channel gain associated with said second diversity signal.

8. The method of claim 1 wherein determining said first power control code based on said first channel quality estimate comprises determining said first power control code based on a comparison of said first channel quality estimate with said second channel quality estimate.

9. The method of claim 1 wherein determining said second power control code based on said first channel quality estimate comprises determining said second power control code based on a comparison of said second channel quality estimate with said first channel quality estimate.

10. A method of forward link power control implemented by a mobile terminal in a wireless communication system, said method comprising:

determining a first power control bit based on a first diversity signal received at said mobile terminal from a base station;

determining a second power control bit based on a second diversity signal received at said mobile terminal from said base station;

dividing a power control channel into first and second power control sub-channels;

time-multiplexing said first and second power control bits on said power control channel by transmitting said first power control bit to said base station in said first power control sub-channel and transmitting said second power control bit to said base station in said second power control sub-channel.

11. The method of claim 10 wherein dividing a power control channel into first and second power control sub-channels comprises:

dividing said power control channel into a plurality of frames, each frame of said power control channel comprising a plurality of power control groups;

assigning a first set of said power control groups in each frame to said first power control sub-channel; and

assigning a second set of said power control groups in each frame to said second power control sub-channel.

12. The method of claim 11 wherein assigning said first set of power control groups to said first power control sub-channel comprises assigning odd or even power control groups to said first power control sub-channel, and wherein assigning said second set of power control groups to said second power control sub-channel comprises assigning even or odd power control groups to said second power control sub-channel.

13. A method of forward link power control implemented in a wireless communication system comprising a base station and a mobile terminal, said method comprising:

transmitting a first diversity signal from said base station to said mobile terminal;

receiving said first diversity signal at said mobile terminal;

deriving a first channel quality estimate based on said first diversity signal at said mobile terminal;

transmitting a second diversity signal from said base station to said mobile terminal;

deriving a second channel quality estimate by said mobile terminal based on said second diversity signal;

determining a second power control code by said mobile terminal based on said second channel quality estimate;

combining said first and second diversity signals to obtain a combined signal;

deriving a combined channel quality estimate from said combined signal;

determining a first power control code by said mobile terminal based on said first channel quality estimate, said second channel quality estimate, and said combined channel quality estimate;

determining a second power control code based on said first channel quality estimate, said second channel quality estimate, and said combined channel quality estimate;

transmitting said first power control code from said mobile terminal to said base station;

transmitting said second power control code from said mobile terminal to said base station;

adjusting the transmit power of said first diversity signal at said base station based on said first power control code; and

adjusting the transmit power of said second diversity signal at said base station based on said second power control code.

14. The method of claim 13 wherein deriving said first channel quality estimate based on said first diversity signal comprises determining a frame error rate associated with said first diversity signal.

15. The method of claim 13 wherein deriving said first channel quality estimate based on said first diversity signal comprises determining a signal-to-interference ratio associated with said first diversity signal.

16. The method of claim 13 wherein deriving said first channel quality estimate based on said first diversity signal comprises determining a channel gain associated with said first diversity signal.

17. The method of claim 13 wherein determining said first power control code by said mobile terminal based on said first channel quality estimate, said second channel quality estimate, and said combined channel quality estimate comprises:

comparing said combined channel quality estimate with a predetermined channel quality standard to determine a power correction factor; and

determining said first power control code based on said power control factor and a comparison of said first channel quality estimate with said second channel quality estimate.

18. The method of claim 13 wherein deriving said second channel quality estimate based on said second diversity signal comprises determining a frame error rate associated with said second diversity channel.

19. The method of claim 13 wherein deriving said second channel quality estimate based on said second diversity signal comprises determining a signal-to-interference ratio associated with said second diversity signal.

20. The method of claim 13 wherein deriving said second channel quality estimate based on said second diversity signal comprises determining a channel gain associated with said second diversity signal.

21. The method of claim 13 wherein determining said second power control code based on said first channel quality estimate, said second channel quality estimate, and said combined channel quality estimate comprises:

comparing said combined channel quality estimate with a predetermined channel quality standard to determine a power correction factor; and

determining said second power control code based on said power control factor and a comparison of said second channel quality estimate with said first channel quality estimate.

22. A mobile terminal for implementing a forward link power control algorithm, said mobile terminal comprising:

first and second receivers to receive first and second diversity signals respectively from a base station; and

power control logic to;

derive a first channel quality estimate based on said first diversity signal, said first channel quality estimate comprising at least one of a frame error rate, a signal to interference ratio, and a channel gain;

derive a second channel quality estimate based on said second diversity signal, said second channel quality estimate comprising at least one of a frame error rate, a signal to interference ratio, and a channel gain;

determine first and second power control codes based on said first and second channel quality estimates respectively; and

a transmitter to transmit said first and second power control codes from said mobile terminal to said base station.

23. A mobile communications system comprising:

a base station having first and second antennas to transmit first and second diversity signals respectively;

a mobile terminal to receive said first and second diversity signals transmitted by said base station;

said mobile terminal being operative to;

derive a first channel quality estimate based on said first diversity signal, said first channel quality estimate comprising at least one of a frame error rate, a signal to interference ratio, and a channel gain;

derive a second channel quality estimate based on said second diversity signal, said second channel quality estimate comprising at least one of a frame error rate, a signal to interference ratio, and a channel gain;

determine first and second power control codes based on said first and second channel quality estimates respectively; and

transmit said first and second power control codes to said base station; and

wherein said base station is responsive to said first and second power control codes to adjust the transmit power of said first and second antennas based on said first and second power control codes respectively.