Method and apparatus for energy detection in a modem

• US 6,289,057 B1
• Filed: 04/30/1998
• Issued: 09/11/2001
• Est. Priority Date: 04/30/1998
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Yirga, Sisay, Noel, Peter, Velez, Edgar
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US09/069,741
• Time in Patent Office: 1,230 Days
• Field of Search: 375/222, 375/219, 375/317, 375/316, 375/345, 375/329, 375/377, 375/287, 375/318, 375/224, 375/227, 375/228, 375/340, 375/343, 375/143, 375/152, 329/304, 455/234.1, 455/226.2, 455/557, 379/399, 327/50
• US Class Current: 375/317
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation

Abstract

A system of energy detection for detecting a valid signal in a modem to enable power savings in receiver and transmitter circuits. The method of energy detection includes the steps of: (a) processing a prescribed number of signal samples (e.g. typically between 512 and 2048); (b) determining an average energy level for the prescribed number of signal samples; (c) determining a gain of an amplifier based on the processed signal samples; (d) comparing the average energy level with a prescribed energy level threshold; and (e) comparing the gain of the amplifier with a prescribed amplifier gain threshold. If the average energy level is greater than the prescribed energy level threshold and if the gain of the amplifier is less than the prescribed amplifier gain threshold then a valid signal is declared and the transmitter of the modem is activated.

Claims

1. An energy detection apparatus for detecting a valid incoming signal at a receiver in a modem comprising:

(a) an integrator for averaging an energy level of a signal from which most out-of-band interference and noise has been rejected, the energy level being averaged in a prescribed number of signal samples to produce an average energy level;

(b) a first comparator for comparing the average energy level with a predetermined threshold level is graeter than the predetermined threshold then the valid signal has been detected;

(c) an amplifier having a maximum gain and an amplifier gain in response to the incoming signal; and

(d) a second comparator for comparing the amplifier gain with a predetermined amplifier gain threshold, whereby if the average energy level is greater than a predetermined threshold, and if the amplifier gain is less then the predetermined amplifier gain threshold, then the valid signal has been detected.

2. The apparatus of claim 1, wherein the predetermined amplifier gain threshold is equal to the maximum gain of the amplifier.

3. The apparatus of claim 1, further including a digital matched filter for separating a digital representation of the signal samples into an in-phase component and a quadrature component.

4. The apparatus of claim 3, wherein the digital matched filter is a Nyquist filter.

5. The apparatus of claim 4, further including an adder for adding an absolute value of the in-phase component with an absolute value of the quadrature component.

6. The apparatus of claim 1, wherein the amplifier is an automatic gain control amplifier for conditioning the signal samples for loss and attenuation to ensure an output signal from the amplifier is of a constant strength.

7. The apparatus of claim 1, wherein the integratear includes a low pass filter having a filter pole.

8. The apparatus of claim 7, wherein the filter pole is defined as 1/π

, where π

=2^k divided by a modulation rate of the modem and k presents a detection accuracy parameter, wherein the prescribed number of signal samples is equal to 2^k×

N, where N is a number of time constants required for the low pass filter to settle.

9. The apparatus of claim 8, wherein k depends on the modulation rate of the modem, signal detection accuracy, and signal detection speed.

10. The apparatus of claim 9, wherein k is between 6 and 12.

11. The apparatus of claim 10, wherein N is equal to 4 and k is equal to 7, whereby the prescribed number of signal samples is equal to 512.

12. The apparatus of claim 10, wherein N is equal to 4 and k is equal to 9, whereby the prescribed number of signal samples is equal to 2048.

13. A method of energy detection for detecting a valid incoming signal in a modern, comprising the steps of:

(a) processing a prescribed number of signal samples of a signal from which most out-of-band interference and noise has been rejected;

(b) determining an average energy level for the prescribed number of signal samples;

(c) determining a gain of an amplifier based on the incoming signal; and

(d) declaring the valid signal when the average energy level is greater than a prescribed energy level threshold and when the gain of the amplifier is less than a prescribed amplifier gain threshold.

14. The method of claim 13, further including separating a digital representation of the signal samples into an in-phase component and a quadrature component.

15. The method of claim 14, wherein step (b) includes the following steps:

adding an absolute value of the in-phase component of the signal samples to an absolute value of the quadrature component of the signal samples to obtain a sum of signal sample components; and

integrating the sum of signal sample components for the prescribed number of signal samples.

16. The method of claim 13, wherein the predetermined amplifier gain threshold is equal to a maximum gain of the amplifier.

17. The method of claim 13, wherein the prescribed number of signal samples is equal to 2^k×

N, where N represents a time constant and k represents a detection accuracy parameter.

18. The method of claim 17, wherein k is between 6 and 12.

19. The method of claim 18, wherein N is equal to 4 and k is equal to 7, whereby the prescribed number of signal samples is equal to 512.

20. The method of claim 18, wherein N is equal to 4 and k is equal to 9, whereby the prescribed number of signal samples is equal to 2048.

21. A method of energy detection for detecting a valid incoming signal in a receiver of a modem, comprising steps of:

(a) processing 2^k×

N signal samples, where N represents a time constant and k represents a detection accuracy parameter;

(b) determining an average energy level for the signal samples;

(c) determining a gain of an amplifier based on the incoming signal;

(d) coming the average energy level with a prescribed energy level threshold; and

(e) comparing the gain of the amplifier with a prescribed amplifier gain threshold, wherein if the average energy level is greater than the prescribed energy level threshold and if the gain of the amplifier is less than the prescribed amplifier gain threshold, detection of the valid signal is declared.

22. The method of claim 21, further including a step of separating a digital representation of the signal samples into an in-phase component and a quadrature component.

23. The method of claim 22, wherein step (b) includes the following steps:

adding an absolute value of the in-phase component of the signal samples to an absolute value of the quadrature component of the signal samples to obtain a sum of signal sample components; and

integrating the sum of signal sample components for the prescribed number of signal samples.

24. The method of claim 22, wherein the predetermined amplifier gain threshold is equal to a maximum gain of the amplifier.

25. The method of claim 21, wherein k is between 6 and 12.

26. The method of claim 25, wherein N is equal to 4 and k is equal to 7, and a number of signal samples is equal to 512.

27. The method of claim 25, wherein N is equal to 4 and k is equal to 9, and a number of signal samples is equal to 2048.