Calibrating received signal measurements in a communication device

1. A method of calibrating received signal measurements in a first communication device, the method comprising: measuring a received signal level for each of one or more subcarriers of a transmitted signal received from a second communication device; converting the measured received signal level for each of the one or more subcarriers into a corresponding measured power level; estimating a terminal-to-terminal impedance between the first and second communication devices; and calculating a corrected power level for each of the one or more subcarriers as a function of the measured power level for the subcarrier, a known reference input impedance for the first communication device and the estimated terminal-to-terminal impedance.

2. The method of claim 1 , wherein the terminal-to-terminal impedance is estimated as a function of a mismatch between the terminal-to-terminal impedance and an input impedance of the first communication device.

3. The method of claim 2 , wherein the terminal-to-terminal impedance is estimated based on the input impedance of the first communication device and one or more correction factors.

4. The method of claim 3 , wherein one of the one or more correction factors corresponds to echo cancelling settings of a hybrid circuit included in the first communication device.

5. The method of claim 3 , wherein one of the one or more correction factors corresponds to coefficients of a filter included in the first communication device.

6. The method of claim 3 , wherein the one or more correction factors are retrieved from a look-up table stored in memory included in the first communication device.

7. The method of claim 1 , wherein the measured received signal level for each of the one or more subcarriers is converted into a corresponding measured power level as a function of the known reference input impedance.

8. The method of claim 1 , wherein the measured received signal levels represent actual received power levels.

9. The method of claim 1 , wherein the corrected power levels are calculated by normalizing the measured power levels to the known reference input impedance.

10. The method of claim 9 , wherein the measured power levels are normalized to the known reference input impedance level based on the estimated terminal-to-terminal impedance and one or more scaling factors.

11. The method of claim 9 , wherein the measured power levels are normalized to the known reference input impedance level using a look-up table formulated with pre-calculated normalized power levels for each of a range of quantized measured power levels.

12. The method of claim 1 , wherein the estimated terminal-to-terminal impedance represents a nominal loop impedance between the first communication devices.

13. A first communication device comprising one or more circuits operable to: measure a received signal level for each of one or more subcarriers of a transmitted signal generated by a second communication device; convert the measured received signal level for each of the one or more subcarriers into a corresponding measured power level; estimate a terminal-to-terminal impedance between the first and second communication devices; and calculate a corrected power level for each of the one or more subcarriers as a function of the measured power level, a known reference input impedance for the first communication device and the estimated terminal-to-terminal impedance.

14. The first communication device of claim 13 , wherein the one or more circuits are operable to estimate the terminal-to-terminal impedance as a function of a mismatch between the terminal-to-terminal impedance and an input impedance of the first communication device.

15. The first communication device of claim 14 , wherein the one or more circuits are operable to estimate the terminal-to-terminal impedance based on the input impedance of the first communication device and one or more correction factors.

16. The first communication device of claim 13 , wherein the one or more circuits are operable to convert the measured received signal level for each of the one or more subcarriers into a corresponding measured power level as a function of the known reference input impedance.

17. The first communication device of claim 13 , wherein the measured received signal levels represent actual received power levels.

18. The first communication device of claim 13 , wherein the one or more circuits are operable to calculate the corrected power levels by normalizing the measured power levels to the known reference input impedance.

19. The first communication device of claim 18 , wherein the one or more circuits are operable to normalize the measured power levels to the known reference input impedance level based on the estimated terminal-to-terminal impedance and one or more scaling factors.

20. The first communication device of claim 19 , wherein the one or more circuits are operable to normalize the measured power levels to the known reference input impedance level using a look-up table formulated with pre-calculated normalized power levels for each of a range of quantized measured power levels.

21. A first Digital Subscriber Line (DSL) communication device comprising one or more circuits operable to: measure a received signal level for each of one or more subcarriers of a transmitted DSL signal generated by a second DSL communication device; convert the measured received signal level for each of the one or more subcarriers into a corresponding measured power level; estimate a loop impedance between the first and second DSL communication devices; and calculate a corrected power level for each of the one or more subcarriers as a function of the measured power level, a known reference input impedance for the first DSL communication device and the estimated loop impedance.