Method for detecting an oscillation in an on-frequency repeater

• US 20050118949A1
• Filed: 09/16/2004
• Published: 06/02/2005
• Est. Priority Date: 09/16/2003
• Status: Active Grant

• Current Assignee: Spotwave Wireless, Inc. (Kavveri Telecom Products Limited)
• Original Assignee: Spotwave Wireless, Inc. (Kavveri Telecom Products Limited)
• Inventors: Colledan, Marc, Allen, Steve
• Granted Patent: US 7,593,689 B2
• Time in Patent Office: Days
• US Class Current: 455/13.400
• CPC Class Codes: H04B 7/15578 by gain adjustment

Abstract

A method of detecting oscillation in an on-frequency repeater having an RF signal path coupled between an input antenna and an output antenna. In accordance with the present invention, a first RF signal power level within the RF signal path is detected during an un-muted period in which transmission of an output RF signal through the output antenna is enabled. A second RF signal power level within the RF signal path is detected during a mute period in which transmission of an RF signal through the output antenna is disabled. The first and second detected RF signal power levels are then compared, which provides an indication of signal leakage, and thus oscillation.

Claims

1. A method of detecting oscillation in an on-frequency repeater having an RF signal path coupled between an input antenna and an output antenna, the method comprising steps of:

detecting a first RF signal power level within the RF signal path during an un-muted period in which transmission of an output RF signal through the output antenna is enabled;

detecting a second RF signal power level within the RF signal path during a mute period in which transmission of an RF signal through the output antenna is disabled; and

comparing the first and second detected RF signal power levels.

2. A method as claimed in claim 1, wherein at least the step of detecting the second RF signal power level is repeated at a predetermined frequency, and wherein the duration of each mute period is selected to limit disruption of subscriber traffic.

3. A method as claimed in claim 2, wherein the frequency and duration are selected to yield a mute period duty cycle of 1% or less.

4. A method as claimed in claim 2, wherein the frequency is approximately 10 Hz and the duration is 1 mSec.

5. A method of controlling oscillation in an on-frequency repeater having an RF signal path coupled between an input antenna and an output antenna, the method comprising steps of:

detecting a first RF signal power level within the RF signal path during an un-muted period in which transmission of an output RF signal through the output antenna is enabled;

detecting a second RF signal power level within the RF signal path during a mute period in which transmission of an RF signal through the output antenna is disabled;

comparing the first and second detected RF signal power levels; and

adjusting a gain of the RF signal path based on the comparison result.

6. A method as claimed in claim 5, wherein at least the step of detecting the second RF signal power level is repeated at a predetermined frequency, and wherein the duration of each mute period is selected to limit disruption of subscriber traffic.

7. A method as claimed in claim 6, wherein the frequency and duration are selected to yield a mute period duty cycle of 1% or less.

8. A method as claimed in claim 6, wherein the frequency is 10 Hz and the duration is 1 mSec.

9. A method as claimed in claim 5, wherein the step of comparing the first and second detected RF signal power levels comprises a step of calculating a difference between the first and second detected RF signal power levels.

10. A method as claimed in claim 9, wherein the step of adjusting a gain of the RF signal path comprises a step of reducing gain of the RF signal path if the calculated difference is greater than a first predetermined threshold value.

11. A method as claimed in claim 10, wherein the first predetermined threshold value is selected based on any one or more of:

a likelihood of oscillation;

a desired stability margin; and

convergence of the gain to an optimum value.

12. A method as claimed in claim 10, wherein the step of adjusting the gain of the RF signal path further comprises a step of increasing the gain of the RF signal path if the gain is less than a maximum gain of the RF signal path and the calculated difference is less than a second predetermined threshold value.

13. A method as claimed in claim 12, wherein the second threshold value is selected based on any one or more of:

a desired stability margin;

an estimated variability of an RF environment in which the repeater is located; and

convergence of the gain to an optimum value.

14. A method as claimed in claim 12, wherein the first and second threshold values are equal.

15. In a wireless network having a base station and one or more mobile stations within a coverage area of a repeater adapted to receive and amplify uplink RF signals from each mobile station and to transmit the amplified uplink RF signals to the base station, a method of reducing interference at the base station, the method comprising steps of:

detecting an absence of uplink RF signals from the mobile stations; and

muting transmission of RF signals to the base station in response to the detected absence.

16. A method as claimed in claim 15, wherein the step of detecting an absence of uplink RF signals from the mobile station comprises steps of:

detecting an RF signal power level within an RF signal path of the repeater during a mute period in which transmission of RF signals to the base station is disabled; and

comparing the detected RF signal power to a predetermined threshold value.

17. A method as claimed in claim 16, wherein the step of detecting the RF signal power level is repeated at a predetermined frequency, and wherein the duration of each mute period is selected to limit disruption of subscriber traffic.

18. A method as claimed in claim 17, wherein the frequency and duration are selected to yield a mute period duty cycle of 1% or less.

19. A method as claimed in claim 17, wherein the frequency is 10 Hz and the duration is 1 mSec.

20. A method as claimed in claim 16, wherein the predetermined threshold value is selected based on one or more of:

an estimated amplifier noise of the RF signal path; and

an estimated ambient Radio Frequency Interference (RFI) in a coverage area of the repeater.

21. A method as claimed in claim 15, further comprising steps of:

detecting transmission of uplink RF signals from the mobile station; and

un-muting transmission of the amplified uplink RF signals by the repeater in response to the detected transmission.

22. A method as claimed in claim 21, wherein the step of detecting transmission of uplink RF signals from the mobile station comprises steps of:

detecting an RF signal power level within the RF signal path of the repeater; and

comparing the detected RF signal power to a predetermined threshold value.

23. A method as claimed in claim 22, wherein the step of detecting the RF signal power level is repeated at a predetermined frequency selected to limit disruption of subscriber traffic.

24. A method as claimed in claim 23, wherein the frequency is at least 10 Hz.

25. A method as claimed in claim 22, wherein the predetermined threshold value is selected based on one or more of:

an estimated amplifier noise of the RF signal path; and

an estimated ambient RF noise in a coverage area of the repeater.

26. In a wireless network having a base station and one or more mobile stations within a coverage area of a repeater adapted to receive and amplify uplink RF signals from each mobile station and to transmit the amplified uplink RF signals to the base station, a method of detecting a presence of uplink RF signals transmitted by any one or more of the mobile stations, the method comprising steps of:

detecting an RF signal power level within the RF signal path during a mute period in which transmission of the amplified uplink RF signals to the base station is disabled; and

comparing the detected RF signal power level to a predetermined threshold.

27. A method as claimed in claim 26, wherein at least the step of detecting the RF signal power level is repeated at a predetermined frequency, and wherein the duration of each mute period is selected to limit disruption of subscriber traffic.

28. A method as claimed in claim 27, wherein the frequency and duration are selected to yield a mute period duty cycle of 1% or less.

29. A method as claimed in claim 27, wherein the frequency is approximately 10 Hz and the duration is 1 mSec.

30. A method as claimed in claim 26, wherein the predetermined threshold value is selected based on one or more of:

an estimated amplifier noise of the RF signal path; and

an estimated ambient RF noise in a coverage area of the repeater.