Signal, interference and noise power measurement

• US 20030219069A1
• Filed: 09/06/2002
• Published: 11/27/2003
• Est. Priority Date: 04/27/2001
• Status: Active Grant

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Chen, Ernest C., Tran, Chinh
• Granted Patent: US 7,822,154 B2
• Time in Patent Office: Days
• US Class Current: 375/227
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 7/1851 Systems using a satellite or space-based relay H04B7/18508, H04B7/18521 take precedence; providing specific services H04B7/18523 - H04B7/18576
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays
• CPC Class Codes: H04B 7/18526 Arrangements for data linking, networking or transporting, or for controlling an end to end session data switching networks H04L12/00
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 1/206 for modulated signals
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 2027/0061 remodulation
• CPC Class Codes: H04L 27/183 Multiresolution systems
• CPC Class Codes: H04L 27/227 using coherent demodulation
• CPC Class Codes: H04L 27/366 Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator

Abstract

Systems and methods are presented for measuring power levels of primary and interfering signals as well as noise, particularly for satellite transmitted signals. A typical method comprises the steps of receiving a signal comprising a primary signal, an interference signal and noise, demodulating the primary signal to remove a carrier frequency, decoding the primary signal to obtain symbols, estimating a power level of the primary signal based upon the demodulated and decoded primary signal. Additionally, an ideal primary signal can be generated from the carrier power and frequency and the symbols and subtracted from the received signal to produce the noise and interference signal. The noise and interference power is then estimated from the noise and interference signal.

Claims

1. A method of measuring signal properties, comprising the steps of:

receiving a signal comprising a primary signal, an interference signal and noise, the primary signal including a carrier frequency and symbols;

demodulating the primary signal to remove the carrier frequency;

decoding the primary signal to obtain the symbols;

estimating a power level of the primary signal based upon the demodulated and decoded primary signal;

generating an ideal primary signal from the carrier power and frequency and the symbols;

subtracting the ideal primary signal from the received signal to produce the noise and interference signal; and

estimating the noise and interference power from the noise and interference signal.

2. The method of claim 1, further comprising removing a symbol phase from the demodulated primary signal and wherein the step of estimating a power level of the primary signal comprises measuring a DC level of the demodulated primary signal with the symbol phase removed.

3. The method of claim 1, wherein estimating the noise and interference power comprises estimating a combined noise and interference power.

4. The method of claim 1, wherein the interference signal includes an interference carrier and interference symbols and estimating the noise and interference power comprises demodulating and decoding the interference signal to remove the interference carrier and interference symbols and produce a signal having an interference signal DC level and a noise level.

5. The method of claim 4, further comprising estimating the interference power from the interference signal DC level.

6. The method of claim 5, further comprising estimating the noise power by subtracting the interference DC level from the signal having an interference signal DC level and noise level.

7. The method of claim 1, wherein the received signal further includes at least one additional interference signal and each additional interference signal is demodulated and decoded to remove a carrier and symbols of the respective additional interference signal after subtracting all higher power signals.

8. The method of claim 7, wherein a power level of each additional interference signal is calculated from a DC level of the respective additional interference signal.

9. The method of claim 1, wherein the method is performed integral to a receiver.

10. The method of claim 9, wherein the receiver is an integrated receiver decoder (IRD) or a dedicated receiver.

11. The method of claim 9, wherein the primary signal power and the noise and interference power are communicated to a power control system to optimize primary and interference signal power over a coverage area.

12. The method of claim 9, wherein the primary signal power and the noise and interference power are communicated to a central system through a phone dialup.

13. An apparatus for measuring signal properties, comprising:

a demodulator, receiving a signal including a primary signal, an interference signal and noise, for demodulating the primary signal to remove a carrier frequency from the primary signal;

a decoder for decoding the primary signal to obtain symbols from the primary signal;

a processor for estimating a power of the primary signal from the demodulated and decoded primary signal;

a signal generator for generating an ideal primary signal from the carrier power and frequency and the symbols;

a subtractor for subtracting the ideal primary signal from the received signal to yield the noise and interference signal; and

a processor for determining the noise and interference power from the noise and interference signal.

14. The apparatus of claim 13, further comprising a processor for removing a symbol phase from the demodulated primary signal and wherein the step of estimating a power level of the primary signal comprises measuring a DC level of the demodulated primary signal with the symbol phase removed.

15. The apparatus of claim 13, wherein the processor for determining the noise and interference power determines the noise and interference power by calculating a combined noise and interference power.

16. The apparatus of claim 13, wherein the interference signal includes an interference carrier and interference symbols and the processor for determining the noise and interference power comprises a second demodulator and decoder for determining the noise and interference power by demodulating and decoding the interference signal to remove the interference carrier and interference symbols and produce a signal having an interference signal DC level and a noise level.

17. The apparatus of claim 16, wherein the processor for determining the noise and interference power further comprises a processor for calculating the interference power from the interference signal DC level.

18. The apparatus of claim 17, wherein the processor for determining the noise and interference power further comprises a subtractor for subtracting the interference DC level from the signal having an interference signal DC level and a noise level to calculate the noise power.

19. The apparatus of claim 13, wherein the received signal further includes at least one additional interference signal and each additional interference signal is demodulated and decoded to remove a carrier and symbols of the respective additional interference signal after subtracting all higher power signals.

20. The apparatus of claim 19, wherein a power level of each additional interference signal is calculated from a DC level of the respective additional interference signal.

21. The apparatus of claim 13, wherein the apparatus is integral to a receiver.

22. The apparatus of claim 21, wherein the receiver is an integrated receiver decoder (IRD) or a dedicated receiver.

23. The apparatus of claim 21, wherein the primary signal power and the noise and interference power are communicated to a central system to optimize primary and interference signal power over a coverage area.

24. The apparatus of claim 21, wherein the primary signal power and the noise and interference power are communicated to a central system through a phone dialup.