Apparatus to detect interference in wireless signals

• US 9,571,142 B2
• Filed: 10/24/2008
• Issued: 02/14/2017
• Est. Priority Date: 10/24/2008
• Status: Active Grant

• Current Assignee: Anritsu Co (Anritsu Corporation)
• Original Assignee: Anritsu Co (Anritsu Corporation)
• Inventors: Lundquist, Randy L, Huang, Kee-dyi, Thiagarajan, Bhaskar, Venugopal, Vaidyanathan
• Primary Examiner(s): Lu, Zhiyu
• Application Number:
  US12/258,172
• Publication Number:
  US 20100105347A1
• Time in Patent Office: 3,035 Days
• Field of Search: 455/63.1, 455/67.11, 455/67.13, 455/67.14, 455/67.16, 455/67.7, 455/154.2, 455/158.4, 455/158.5, 455/226.1, 455/226.2, 455/226.4, 455/227
• US Class Current: 1/1
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04J 11/0023 Interference mitigation or co-ordination direct sequence spread spectrum [DSSS] systems H04B1/7097; frequency hopping H04B1/713; allocation criteria for ingress interference avoidance H04L5/0062; frequency allocation criteria for requirements on out-of-channel emissions H04L5/0066; arrangements for removing intersymbol interference or baseband equalisers H04L25/03006; peak power aspects in multicarrier modulation H04L27/2614; power management H04W52/00; traffic scheduling H04W72/54, H04W72/541
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14

Abstract

An apparatus to detect interference in wireless signals, comprising an antenna for receiving a wireless signal; and wherein the apparatus is operable to identify a dominant waveform in the received signal; subtract the dominant waveform from the received signal to create a modified received signal; and repeat the above steps, recursively substituting the modified received signal for the received signal, until all adjusted reference waveforms have been subtracted.

Claims

1. An apparatus to identify interference in wireless signals, the apparatus comprising:

an antenna operable to receive a wireless signal;

an input means operable to receive input from a user; and

a computer readable storage medium and processor operating thereon, wherein the computer readable storage medium includes instructions that when executed in response to user input cause the apparatus to

(a) acquire a standard-defined set of reference sequences in discrete time format, wherein each of the reference sequences is a known sequence from which a signal source is identifiable;

(b) modulate the standard-defined set of reference sequences according to a signal type associated with each of the reference sequences to generate a set of ideal waveforms;

(c) store the set of ideal reference waveforms as a set of complex sequences representing in-phase and out-of-phase components of the ideal reference waveforms;

(d) sample the received signal over a length of time to obtain a sampled signal, wherein the sampled signal comprises a plurality of signals, wherein each signal from the plurality of signals comprises a modulated waveform;

(e) store the sampled signal as a complex sequence representing in-phase and out-of-phase components of the sampled signal;

(f) retrieve the stored set of ideal reference waveforms;

(g) cross-correlate discrete time periods of the sampled signal with the set of ideal reference waveforms to generate an array of complex values representing in-phase and out-of-phase components over the sampled length of time;

(h) identify a dominant waveform in the sampled signal based on magnitudes of the complex values above an estimated noise floor, wherein the dominant waveform is identified with a reference waveform from the set of ideal reference waveforms associated with the complex value having highest magnitude;

(i) remove the dominant waveform from the sampled signal to create a modified sampled signal wherein removing the dominant waveform comprises

measuring characteristics of the dominant waveform;

adjusting an ideal reference waveform corresponding to the dominant waveform according to the measured characteristics to create an adjusted waveform; and

subtracting the adjusted waveform from the sampled signal to create the modified sampled signal; and

(j) repeat steps (h) and (i), recursively substituting the modified sampled signal from step (i) for the sampled signal, until all dominant waveforms have been removed, leaving a remaining signal having no identifiable dominant component; and

(k) identify the remaining signal as interference in the signal.

2. The apparatus of claim 1 wherein measured characteristics include frequency, phase, and time offset and power for the dominant waveform.

3. The apparatus of claim 2 wherein the set of ideal reference waveforms is constructed according to the further steps of:

interpolating and over-sampling the reference waveforms.

4. The apparatus of claim 1 wherein the input means is further operable to receive input from the user selecting between spectral analysis and base station analysis and wherein in response to user input the apparatus performs the selected analysis.

5. An apparatus to identify interference in wireless signals comprising:

an antenna operable to receive a wireless signal; and

a computer readable storage medium and processor operating thereon, wherein the computer readable storage medium includes instructions that when executed cause the apparatus to

(a) acquire a standard-defined set of reference sequences in discrete time format, wherein each of the reference sequences is a known sequence from which a signal source is identifiable;

(b) modulate the standard-defined set of reference sequences according to a signal type associated with each of the reference sequences to generate a set of ideal waveforms;

(c) store the set of ideal reference waveforms as a set of complex sequences representing in-phase and out-of-phase components of the ideal reference waveforms;

(d) sample the received signal over a length of time to obtain a sampled signal, wherein the sampled signal comprises a plurality of signals, wherein each signal from the plurality of signals comprises a modulated waveform;

(e) store the sampled signal as a complex sequence representing in-phase and out-of-phase components of the sampled signal;

(f) retrieve the stored set of ideal reference waveforms;

(g) cross-correlate the sampled signal with the set of ideal reference waveforms;

(h) identify a dominant waveform in the sampled signal, wherein the dominant waveform is identified with a reference waveform from the set of ideal reference waveforms cross-correlated with the sampled signal;

(i) measure frequency, phase, and time offset and power for the dominant waveform;

(j) adjust an ideal reference waveform corresponding to the dominant waveform according to the measured frequency, phase, and time offset and power to create an adjusted reference waveform;

(k) subtract the adjusted reference waveform from the sampled signal to create a modified sampled signal; and

(l) repeat steps (h)-(k), recursively substituting the modified sampled signal from step (k) for the sampled signal, until all dominant waveforms have been subtracted, leaving a remaining signal having no identifiable dominant waveform; and

(m) identify the remaining signal as interference in the sampled signal.

6. The apparatus of claim 5 wherein the set of ideal reference waveforms is created by the steps of:

acquiring a standard-defined set of reference sequences in discrete time format.

7. The apparatus of claim 6 wherein the reference sequences are interpolated and oversampled to an Nx sampling rate, wherein the Nx sampling rate is greater than a rate associated with the standard-defined set of reference sequences.

8. The apparatus of claim 7 wherein the cross-correlation is performed at the Nx sampling rate.

9. The apparatus of claim 8 wherein modulating includes pulse shaping or equalization for reference waveforms as specified in the respective signal standards.

10. The apparatus of claim 8 wherein modulating includes performing a discrete inverse Fourier transform for reference waveforms corresponding to OFDM signals.

11. The apparatus of claim 5 further comprising:

a display;

wherein the apparatus is operable to perform a Fourier transform on the modified received signal; and

display the transformed modified received signal on the display.

12. The apparatus of claim 5 further comprising:

wherein the apparatus is operable to display each dominant waveform along with its measured power and time offset on a display coupled thereto.

13. The apparatus of claim 5 wherein identifying a dominant waveform includes determining which reference waveform generates a highest correlation value in the cross-correlation.

14. The apparatus of claim 5 wherein the received signal is filtered and pulse-shaped.

15. The apparatus of claim 5 wherein the received signal is a cellular or wireless area network signal.

16. A computer program product comprising at least one non-transitory computer-readable storage medium storing one or more sequences of instructions, wherein execution of the one or more sequences of instructions by one or more processors causes the one or more processors to isolate interference in wireless signals, the one or more sequences of instructions comprising:

(a) acquiring a standard-defined set of reference sequences, wherein each of the reference sequences is a known sequence from which a signal source is identifiable;

(b) modulating the standard-defined set of reference sequences according to a signal type associated with each of the reference sequences to generate a set of ideal waveforms;

(c) storing the set of ideal reference waveforms as a set of complex sequences representing in-phase and out-of-phase components of the ideal reference waveforms;

(d) receiving a signal;

(e) sampling the received signal over a length of time to obtain a sampled signal, wherein the sampled signal comprises a plurality of signals, wherein each signal from the plurality of signals comprises a modulated waveform;

(f) storing the sampled signal as a complex sequence representing in-phase and out-of-phase components of the sampled signal;

(g) retrieving the stored set of ideal reference waveforms;

(h) cross-correlating discrete time periods of the sampled signal with the set of ideal reference waveforms to generate an array of complex values representing in-phase and out-of-phase components over the sampled length of time;

(i) identifying a dominant waveform in the sampled signal based on magnitudes of the complex values above an estimated noise floor, wherein the dominant waveform is identified with a reference waveform from the set of ideal reference waveforms associated with the complex value having highest magnitude;

(j) removing the dominant waveform from the sampled signal to create a modified sampled signal wherein removing the dominant waveform comprises

measuring characteristics of the dominant waveform,

adjusting an ideal reference waveform corresponding to the dominant waveform according to the measured characteristics to create an adjusted waveform, and

subtracting the adjusted waveform from the sampled signal to create the modified sampled signal; and

(k) repeating steps (i) and (j), recursively substituting the modified sampled signal from step (j) for the sampled signal, until all dominant waveforms have been removed, leaving a remaining signal having no identifiable dominant waveform; and

(l) identifying the remaining signal as interference in the signal.

17. The apparatus of claim 16 wherein measured characteristics include frequency, phase, and time offset and power for the dominant waveform.

18. The apparatus of claim 17 wherein the set of ideal reference waveforms is constructed according to the steps of:

interpolating and over-sampling the reference waveforms.