Leakage detection for OFDM system with fixed pilot

1. A cable network test instrument comprising:

an antenna connected to an RF transceiver, and

a controller electrically connected to the RF transceiver and being configured to access data on a frequency range being scanned by the antenna,

wherein the controller includes circuitry configured to:

isolate a plurality of sets of subcarriers from the collected signal data, each of the plurality of sets including subcarriers associated with each one of frequency bins of the predefined frequency range,

add the subcarriers of the plurality of sets based on the frequency bin associated therewith, and

determine, based on a ratio of power of the added subcarriers of the frequency bins, whether a leakage of an orthogonal frequency-division multiplexing (OFDM)-based signal is present.

2. The cable network test instrument of claim 1 , wherein to isolate the plurality of sets of subcarriers from the collected signal data comprises to transform, using a fast Fourier transform (FFT) block, a first set of signal data samples to isolate a first batch of subcarriers therefrom and to transform a second set of signal data samples to isolate a second batch of subcarriers therefrom.

3. The cable network test instrument of claim 2 , wherein to add the subcarriers of the plurality of sets based on the frequency bin associated therewith comprises to accumulate, using a plurality of accumulators, values of the subcarriers of each of the frequency bins in the FFT block.

4. The cable network test instrument of claim 1 , wherein the ratio of power includes a ratio between power of signals of frequency bins associated with pilot subcarriers and power of signals of frequency bins associated with data subcarriers.

5. The cable network test instrument of claim 4 , wherein the frequency bins associated with the data subcarriers are disposed between the frequency bins associated with the pilot subcarriers.

6. The cable network test instrument of claim 1 , wherein the circuitry is further configured to determine that the leakage of the OFDM-based signal is present in response to the ratio of power being greater than a threshold.

7. A method for identifying a leakage of an orthogonal frequency-division multiplexing (OFDM)-based signal, the method comprising:

operating a test instrument to scan a predefined frequency range to collect signal data,

isolating, with the test instrument, a plurality of sets of subcarriers from the collected signal data, each of the plurality of sets including subcarriers associated with center frequencies of the predefined frequency range,

operating the test instrument to add the subcarriers of the plurality of sets based on the frequency bin associated therewith, and

determining, based on a ratio of power of the added subcarriers of the frequency bins, whether a leakage of the OFDM-based signal is present.

8. The method of claim 7 , wherein isolating the plurality of sets of subcarriers from the collected signal data includes transforming, using a fast Fourier transform (FFT) block, a first set of signal data samples to isolate a first batch of subcarriers therefrom and transforming a second set of signal data samples to isolate a second batch of subcarriers therefrom.

9. The method of claim 8 , wherein operating the test instrument to add the subcarriers of the plurality of sets based on the frequency bin associated therewith includes accumulating, using a plurality of accumulators, values of the subcarriers of frequency bins.

10. The method of claim 7 , wherein the ratio of power of the added subcarriers of the frequency bins includes a ratio between power of signals of frequency bins associated with pilot subcarriers and power of signals of frequency bins associated with data subcarriers.

11. The method of claim 10 , wherein the frequency bins associated with the data subcarriers are disposed between the frequency bins associated with the pilot subcarriers.

12. The method of claim 7 , further comprising determining that the leakage of the OFDM-based signal is present in response to the ratio of power being greater than a threshold.

13. The method of claim 12 , further comprising displaying a notification alert indicating that leakage of the OFDM-based signal is present in response to the ratio of power being greater than a threshold.

14. A cable network test instrument comprising:

an input unit configured to receive a command to begin scanning a predetermined frequency range, and

a controller electrically connected to the input unit, the controller being configured to detect signals present on the scanned frequency range,

wherein the controller includes circuitry configured to:

sample a first portion of the detected signal and store the samples as a first set,

skip a second portion of the signal data,

sample a third portion of the signal data and store the samples as a second set,

add the samples of the first set to the samples of the second set and store as a combined set, and

identify leakage of an orthogonal frequency-division multiplexing (OFDM)-based signal and generate a corresponding display notification in response to a power ratio between portions of the combined set being greater than a threshold.

15. The cable network test instrument of claim 14 , wherein the samples of the first set and the samples of the second set are subcarriers, and the portions of the combined set comprise a first portion including a plurality of samples associated with frequency bins of pilot subcarriers and a second portion including remaining samples that are associated with frequency bins of data subcarriers.

16. The cable network test instrument of claim 14 , wherein the first and second sets include a same number of samples and the samples of the first and second sets are ordered, such that adding the samples of the first set to the samples of the second set includes adding a sample of the first set having an nth position in the first set to a sample of the second set having an nth position in the second set.

17. The cable network test instrument of claim 14 , wherein the second portion of the detected signal immediately follows the first portion of the detected signal, and the third portion of the detected signal immediately follows the second portion of the detected signal.

18. The cable network test instrument of claim 14 , wherein the second portion of the detected signal immediately follows the first portion of the detected signal, and a combination of the first and second portions of the detected signal is indicative of a total number of samples of the detected signal.

19. The cable network test instrument of claim 14 , wherein the circuitry includes:

an analog-to-digital (A/D) converter arranged to, prior to the sampling, convert the detected signal to a digital signal, and

a fast Fourier transform (FFT) block configured to transform the digital signal output by the A/D converter from a time domain to a frequency domain.

20. The cable network test instrument of claim 19 , further comprising a plurality of accumulators, each accumulator configured to receive one sample of the first set and one sample of the second set.