Method and apparatus for automatic gain control compensation in a wireless communication system

• US 6,799,024 B2
• Filed: 12/18/2001
• Issued: 09/28/2004
• Est. Priority Date: 12/18/2001
• Status: Expired due to Fees

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Brown, Tyler, Wang, Michael M.
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): Le, Duy K
• Application Number:
  US10/025,075
• Publication Number:
  US 20030114126A1
• Time in Patent Office: 1,015 Days
• Field of Search: 455/234.1, 455/234.2, 455/239.1, 455/250.1, 455/254, 455/70, 455/517, 455/550.1, 375/345, 375/140, 375/144, 375/346, 375/349
• US Class Current: 455/234.1
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

In a code division multiple access wireless communication system having at least one base transceiver station and at least one mobile station having a mobile station receiver assembly configured to receive a coded signal having an information-bearing signal portion and an associated interfering signal portion from the base transceiver station, a method and apparatus for automatic gain control compensation in the mobile station receiver assembly, is disclosed. The method includes causing a gain adjustment to the coded signal by an AGC circuit in the mobile station receiver assembly to produce a post-AGC signal having a post-AGC interfering signal portion with an associated post-AGC interfering signal power level, and an associated gain error value. The method further includes compensating for the gain adjustment to the coded signal if the number of receiver fingers assigned to demodulate the coded signal is less than or equal to a predetermined number.

Claims

1. In a wireless communication system, the wireless communication system including at least one base transceiver station and at least one mobile station having a receiver assembly, the base transceiver station capable of transmitting a coded signal having an information-bearing signal portion, the mobile station capable of receiving the coded signal having the information-bearing signal portion and an associated interfering signal portion, the receiver assembly including an automatic gain control circuit for adjusting a gain of the coded signal and a receiver having a number of receiver fingers for demodulating the coded signal and a finger manager for assigning the receiver fingers to demodulate the coded signal, an apparatus for automatic gain control compensation in the receiver assembly of the mobile station, the apparatus comprising:

(a) an automatic gain control circuit configured to cause a gain adjustment to the coded signal by multiplying the coded signal by an AGC gain value to produce a post-AGC signal and an associated gain error value, the post-AGC signal having a post-AGC interfering signal portion with an associated post-AGC interfering signal power level; and

(b) an automatic gain control compensator configured to compensate for the gain adjustment to the coded signal if the number of receiver fingers assigned to demodulate the coded signal is less than or equal to a predetermined number.

2. The apparatus for automatic gain control compensation according to claim 1, wherein the automatic gain control compensator comprises:

a first compensator multiplier configured to multiply the post-AGC signal by an AGC compensation metric to form a compensated post-AGC signal;

a finger controller configured to generate a selector signal based on the number of receiver fingers assigned to demodulate the coded signal; and

a selector for selecting the compensated post-AGC signal to be forwarded to a decoder of the receiver if the selector signal indicates that the number of receiver fingers assigned to demodulate the coded signal is less than or equal to the predetermined number or selecting the post-AGC signal to be forwarded to the decoder if the selector signal indicates that the number of receiver fingers assigned to demodulate the coded signal is not less than or equal to the predetermined number.

3. The apparatus for automatic gain control compensation according to claim 2, wherein the automatic gain control compensator further comprises:

a second compensator multiplier configured to multiply the AGC compensation metric with the gain error value to form an inverse gain squared value;

a compensator register configured to forward the inverse gain squared value after a discrete time interval has elapsed to yield the AGC compensation metric, wherein the AGC compensation metric is substantially equally to an inverse of the AGC gain value squared; and

wherein the AGC compensation metric at a discrete time n is equivalent to the inverse gain squared value at a discrete time n−

1.

4. The apparatus for automatic gain control compensation according to claim 2, further comprising:

an analog to digital converter configured to convert the post-AGC signal to a digital stream, wherein the digital stream represents the post-AGC interfering signal and a post-AGC information signal;

a demodulator configured to generate a demodulated sequence from the digital stream;

a decoder configured to convert the demodulated sequence to an estimate of information bits representative of information used to encode the coded signal; and

wherein the first compensator multiplier is configured to multiply the demodulated sequence by the AGC compensation metric to form the compensated post-AGC signal.

5. The apparatus for automatic gain control compensation according to claim 4, wherein the demodulated sequence is a sequence of SIR values representative of a series of power ratios of the information-bearing signal portion to the interfering signal portion of the coded signal.

6. The apparatus for automatic gain control compensation according to claim 1, wherein the post-AGC interfering signal power level is a varying post-AGC interfering signal power level.

7. The apparatus for automatic gain control compensation according to claim 1, wherein the predetermined number is one.

8. The apparatus for automatic gain control compensation according to claim 1, wherein automatic gain control circuit comprises a gain error generator configured to calculate the gain error value from a comparison between an analog-to-digital converter input variance and an analog-to-digital converter input target variance, and wherein the analog-to-digital converter input target variance is pre-selected based on an analog-to-digital converter utilized in the receiver assembly, and wherein the analog-to-digital converter input variance value is based on the post-AGC signal at a discrete time n−

1.

9. In a wireless communication system, the wireless communication system including at least one base transceiver station and at least one mobile station having a receiver assembly, the base transceiver station capable of transmitting a coded signal having an information-bearing signal portion, the mobile station capable of receiving the coded signal having the information-bearing signal portion and an associated interfering signal portion, the receiver assembly including an automatic gain control circuit for adjusting a gain of the coded signal and a receiver having a number of receiver fingers for demodulating the coded signal and a finger manager for assigning the receiver fingers to demodulate the coded signal, method for automatic gain control compensation in the receiver assembly of the mobile station, the method comprising:

(a) causing a gain adjustment to the coded signal by multiplying the coded signal by an AGC gain value to produce a post-AGC signal and an associated gain error value, the post-AGC signal having a post-AGC interfering signal portion with an associated post-AGC interfering signal power level; and

(b) compensating for the gain adjustment to the coded signal if the number of receiver fingers assigned to demodulate the coded signal is less than or equal to a predetermined number.

10. The method for automatic gain control compensation according to claim 9, wherein the step of compensating for the gain adjustment comprises the steps of:

multiplying the post-AGC signal by an AGC compensation metric to form a compensated post-AGC signal;

generating a selector signal based on the number of receiver fingers assigned by the finger manager to demodulate the coded signal; and

selecting the compensated post-AGC signal to be forwarded to a decoder of the receiver assembly if the selector signal indicates that the number of receiver fingers assigned to demodulate the coded signal is less than or equal to the predetermined number or selecting the post-AGC signal to be forwarded to the decoder if the selector signal indicates that the number of receiver fingers assigned to demodulate the coded signal is not less than or equal to the predetermined number.

11. The method for automatic gain control compensation according to claim 9, wherein the step of compensating for the gain adjustment further comprises the steps of:

multiplying the AGC compensation metric with the gain error value to form an inverse gain squared value; and

generating the AGC compensation metric from the inverse gain squared value after a discrete time interval has elapsed, wherein the AGC compensation metric is substantially equal to an inverse of the AGC gain value squared, and wherein the AGC compensation metric at a discrete time n is equivalent to the inverse gain squared value at a discrete time n−

1.

12. The method for automatic gain control compensation according to claim 9, further comprising the steps of:

converting the post-AGC signal into a digital stream, wherein the digital stream represents the post-AGC interfering signal and a post-AGC information signal;

generating a demodulated sequence from the digital stream;

converting the demodulated sequence to an estimate of information bits representative of information used to encode the coded signal; and

wherein the compensated post-AGC signal is formed by multiplying the demodulated sequence by the AGC compensation metric.

13. The method for automatic gain control compensation according to claim 12, wherein the demodulated sequence is a sequence of SIR values representative of a series of power ratios of the information-bearing signal portion to the interfering signal portion of the coded signal, and wherein the compensated post-AGC signal is a compensated demodulated signal.

14. The method for automatic gain control compensation according to claim 9, wherein the post-AGC interfering signal power level is a varying post-AGC interfering signal power level.

15. The method for automatic gain control compensation according to claim 9, wherein the predetermined number is one.

16. The method for automatic gain control compensation according to claim 15, wherein the step of multiplying the post-AGC signal by an AGC compensation metric comprises the steps of:

multiplying the AGC compensation metric with the gain error value to form an inverse gain squared value; and

generating the AGC compensation metric from the inverse gain squared value after a discrete time interval has elapsed, wherein the AGC compensation metric is substantially equal to an inverse of the AGC gain value squared, and wherein the AGC compensation metric at a discrete time n is equivalent to the inverse gain squared value at a discrete time n−

1.

17. The method for automatic gain control compensation according to claim 9, wherein the step of causing the gain adjustment comprises the steps of:

determining an ADC input variance based on a previous post-AGC signal at a discrete time n−

1, wherein the ADC input variance value is representative of a previous AGC gain value applied to the coded signal at the discrete time n−

1;

calculating the gain error value based on a comparison of the ADC input variance to an ADC input target variance, wherein the ADC input target variance is pre-selected based on the type of ADC used in the mobile station receiver assembly;

multiplying the gain error value with a previous AGC gain value inverse squared to form an AGC gain value inverse squared, wherein a previous gain adjustment to the coded signal at the discrete time n−

1 was caused by multiplying the previous AGC gain value with the coded signal;

calculating an inverse square root of the AGC gain value inverse squared to form the AGC gain value; and

multiplying the AGC gain value with the coded signal to cause the gain adjustment.

18. In a code division multiple access wireless communication system, the wireless communication system including at least one base transceiver station and at least one mobile station having a receiver assembly, the mobile station capable of receiving a coded signal from the base transceiver station, the receiver assembly including an automatic gain control circuit for adjusting a gain of the coded signal to produce a gain error value and a post-AGC signal formed by multiplying the coded signal by an AGC gain value, the post-AGC signal having a post-AGC interfering signal portion with an associated variable post-AGC interfering signal power level, the receiver assembly further including a receiver having a number of receiver fingers for demodulating the coded signal and a finger manager for assigning the receiver fingers to demodulate the coded signal, a method for automatic gain control compensation in the receiver assembly of the mobile station, the method comprising:

(a) multiplying the post-AGC signal by an AGC compensation metric to form a compensated post-AGC signal; and

(b) selecting the compensated post-AGC signal to be forwarded to a decoder of the receiver assembly if the number of receiver fingers assigned to demodulate the coded signal is less than or equal to a predetermined number or selecting the post-AGC signal to be forwarded to the decoder if the number of receiver fingers assigned to demodulate the coded signal is not less than or equal to the predetermined number.

19. The method for automatic gain control compensation according to claim 18, wherein the predetermined number is one.