Wireless receiver with anti-jamming

• US 20030054755A1
• Filed: 03/08/2002
• Published: 03/20/2003
• Est. Priority Date: 03/09/2001
• Status: Abandoned Application

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Zehavi, Ephraim, Bettesh, Ido
• Application Number:
  US10/094,028
• Publication Number:
  US 20030054755A1
• Time in Patent Office: Days
• US Class Current: 455/1
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

A method and apparatus for processing a received signal carrying data via multiple subcarriers at respective subcarrier frequencies is disclosed herein. The method includes assessing jamming interference on the subcarrier frequencies. In response to the assessed interference, respective reliability metrics are assigned to the subcarriers. The signal is then demodulated using the reliability metrics so as to recover the data.

Claims

1. A receiver capable of receiving a signal carrying data via multiple subcarriers at respective subcarrier frequencies, the receiver comprising:

an anti-jamming (AJ) processor, adapted to assess jamming interference on the subcarrier frequencies and, responsive thereto, to assign respective reliability metrics to the subcarriers; and

a demodulator, adapted to demodulate the signal using the reliability metrics so as to recover the data.

2. A receiver according to claim 1, wherein the demodulator comprises a Viterbi decoder, which is adapted to apply the reliability metrics in decoding the data.

3. A receiver according to claim 1, wherein when the AJ processor detects that the jamming interference on a given one of the subcarrier frequencies is strong, it assigns the respective reliability metrics such that the demodulator will ignore the given one of the subcarrier frequencies in demodulating the signal.

4. A receiver according to claim 1, wherein the AJ processor is further adapted to reconstruct the jamming interference and to remove the reconstructed interference from the signal before assigning the reliability metrics.

5. A receiver according to claim 4, wherein the AJ processor is adapted to reconstruct a phase and amplitude of the jamming interference in preparation for removing the reconstructed interference from the signal.

6. A receiver according to claim 5, wherein the AJ processor is configured to reconstruct the interference and remove the reconstructed interference from the signal when it assesses that the interference is of sufficient strength to allow it to reconstruct the phase and the amplitude, and to assign the reliability metrics without reconstructing the interference when the interference is not of the sufficient strength.

7. A receiver according to claim 1, and comprising a frequency domain transformation circuit, which is adapted to separate the signal into the subcarrier frequencies for demodulation by the demodulator, wherein the AJ processor is coupled to assess the jamming interference on the subcarrier frequencies separated by the frequency domain transformation circuit.

8. A receiver according to claim 7, wherein the frequency domain transformation circuit is adapted to apply a Fast Fourier Transform to the signal.

9. A receiver according to claim 1, wherein the signal is modulated by Orthogonal FDM (COFDM) over a wide band of subcarrier frequencies, and wherein the jamming interference is due to transmission of a Frequency Shift Keyed (FSK) signal which hops among different frequencies within a narrow frequency band encompassed by the wide band.

10. A receiver capable of receiving a signal carrying data in the presence of jamming interference, the receiver comprising:

an anti-jamming (AJ) processor, adapted to process the received signal so as to determine a frequency, phase and amplitude of the jamming interference;

a jamming cancellation circuit, coupled to the AJ processor, removes the jamming interference from the received signal responsive to the frequency, phase and amplitude determined by the AJ processor; and

a demodulator, adapted to demodulate the signal after removal of the jamming interference therefrom so as to recover the data.

11. A receiver according to claim 10, wherein the AJ processor comprises a phase estimator, which is coupled to determine the phase of the jamming interference, and a parameter estimator, which is adapted to estimate the amplitude of the jamming interference responsive to the phase.

12. A receiver according to claim 11, wherein the phase estimator comprises a phase-locked loop (PLL).

13. A receiver according to claim 11, wherein when the jamming interference comprises a modulated jamming signal, the parameter estimator is adapted to demodulate the jamming signal so as to estimate the amplitude thereof.

14. A receiver according to claim 13, wherein the modulated jamming signal is due to transmission of a Frequency Shift Keyed (FSK) signal in a narrow band, which hops among different frequencies within a wide band of the signal carrying the data, and wherein the parameter is adapted to demodulate the FSK signal.

15. A receiver according to claim 10, wherein the jamming interference is caused by a modulated jamming signal generated by a transmitter in proximity to the receiver, and wherein the AJ processor is coupled to receive the modulated jamming signal from the transmitter, and to process the received signal together with the modulated jamming signal so as to determine the phase and amplitude of the jamming interference.

16. A receiver according to claim 10, and comprising a sampler, which is coupled to sample the received signal so as to generate a stream of samples, and a buffer, coupled to the sampler so as to receive and hold a block of the samples, wherein the AJ processor is adapted to process the samples in the block so as to determine the phase and amplitude of the jamming interference affecting the block.

17. A receiver according to claim 16, wherein the AJ processor is adapted to process the samples in the block in both forward and reverse temporal directions.

18. A receiver according to claim 16, wherein the AJ processor is adapted to find at least one of a start time and a stop time of the jamming interference that occurred during an interval of time corresponding to the samples in the block.

19. A receiver according to claim 16, wherein the signal carries the data in the form of data symbols, each comprising one or more bits of the data, and wherein the block of the samples comprises at least a number of the samples that corresponds to one of the symbols.

20. A receiver according to claim 10, and comprising a frequency domain transformation circuit, which is adapted to separate the signal into multiple frequency components for demodulation by the demodulator, wherein the AJ processor is coupled to process the frequency components so as to determine the frequency of the jamming interference.

21. A receiver according to claim 20, wherein the frequency domain transformation circuit is adapted to apply a Fast Fourier Transform to the signal.

22. A receiver according to claim 10, wherein the signal carrying the data is modulated by Frequency Division Modulation (FDM) over a wide band of frequencies, and wherein the jamming interference is due to transmission of a narrowband jamming signal at the frequency within the wide band of the FDM signal.

23. A method for communicating data in the presence of jamming interference, comprising:

transmitting a first signal carrying the data from a transmitter to a receiver at a data transmission rate;

determining at the receiver that the first signal has been corrupted by the jamming interference;

sending a reply from the receiver to the transmitter, indicating that the first signal was corrupted;

responsive to the reply, transmitting a second signal carrying the data from the transmitter to the receiver substantially without back-off of the transmission rate; and

processing the first and second signals at the receiver to recover the data therefrom.

24. A method according to claim 23, wherein transmitting the first and second signals comprises transmitting data packets.

25. A method according to claim 23, wherein sending the reply comprises processing the corrupted first signal at the receiver so as to identify the transmitter, and sending a non-acknowledge reply to the identified transmitter.

36. A method according to claim 25, wherein processing the received signal comprises estimating the phase of the jamming interference, and estimating the amplitude of the jamming interference responsive to the phase.

37. A method according to claim 36, wherein estimating the phase comprises feeding the received signal through a phase-locked loop (PLL).

38. A method according to claim 36, wherein when the jamming interference comprises a modulated jamming signal, and wherein processing the received signal comprises demodulating the jamming signal so as to estimate the amplitude thereof.

39. A method according to claim 38, wherein the modulated jamming signal is due to transmission of a Frequency Shift Keyed (FSK) signal in a narrow band, which hops among different frequencies within a wide band of the signal carrying the data, and wherein demodulating the jamming signal comprises demodulating the FSK signal.

26. A method for processing a received signal carrying data via multiple subcarriers at respective subcarrier frequencies, the method comprising:

assessing jamming interference on the subcarrier frequencies;

responsive to the assessed interference, assigning respective reliability metrics to the subcarriers; and

demodulating the signal using the reliability metrics so as to recover the data.

27. A method according to claim 26, wherein demodulating the signal comprises applying Viterbi decoding using the reliability metrics to decode the data.

28. A method according to claim 26, wherein assigning the metrics comprises, when the interference assessed on a given one of the subcarrier frequencies is strong, assigning the respective reliability metrics such that the given one of the subcarrier frequencies will be substantially ignored in demodulating the signal.

29. A method according to claim 26, and comprising reconstructing the jamming interference and removing the reconstructed interference from the signal before assigning the reliability metrics.

30. A method according to claim 29, wherein reconstructing the jamming interference comprises reconstructing a phase and amplitude of the jamming interference in preparation for removing the reconstructed interference from the signal.

31. A method according to claim 30, wherein assessing the jamming interference comprises determining whether the interference is of sufficient strength to allow reconstructing the phase and the amplitude, and wherein assigning the reliability metrics comprises assigning the metrics without reconstructing the interference when the interference is not of the sufficient strength.

32. A method according to claim 26, and comprising transforming the signal to a frequency domain so as to separate the signal into the subcarrier frequencies for demodulating the signal, and wherein assessing the jamming interference comprises assessing the interference on the subcarrier frequencies separated by the frequency domain transformation circuit.

33. A method according to claim 32, wherein transforming the signal comprises applying a Fast Fourier Transform to the signal.

34. A method according to claim 26, wherein the signal is modulated by Orthogonal FDM (COFDM) over a wide band of the frequencies, and wherein assessing the jamming interference comprises assessing the interference due to transmission of a Frequency Shift Keyed (FSK) signal in a narrow band, which hops among different frequencies within the wide band of the COFDM signal.

35. A method for recovering data from a signal received in the presence of jamming interference, the method comprising:

processing the received signal so as to determine a frequency, phase and amplitude of the jamming interference;

removing the jamming interference from the received signal responsive to the determined frequency, phase and amplitude; and

demodulating the signal after removal of the jamming interference therefrom so as to recover the data.

40. A method according to claim 35, wherein the jamming interference is caused by a modulated jamming signal generated by a known transmitter, and wherein removing the jamming interference comprises receiving the modulated jamming signal from the known transmitter, and processing the received signal together with the modulated jamming signal so as to determine the phase and amplitude of the jamming interference.

41. A method according to claim 35, wherein processing the received signal comprises sampling the received signal so as to generate a stream of samples, and holding a block of the samples in a buffer while processing the samples in the block so as to determine the phase and amplitude of the jamming interference affecting the block.

42. A method according to claim 41, wherein processing the samples in the block comprises processing the samples in both forward and reverse temporal directions.

43. A method according to claim 41, wherein processing the received signal comprises finding at least one of a start time and a stop time of the jamming interference that occurred during an interval of time corresponding to the samples in the block.

44. A method according to claim 41, wherein the signal carries the data in the form of data symbols, each comprising one or more bits of the data, and wherein holding the block of the samples comprises holding at least a number of the samples that corresponds to one of the symbols.

45. A method according to claim 35, wherein processing the received signal comprises transforming the signal to a frequency domain, and processing the frequency components so as to determine the frequency of the jamming interference, and wherein demodulating the signal comprises demodulating the signal responsive to the multiple frequency components.

46. A method according to claim 45, wherein transforming the signal comprises applying a Fast Fourier Transform to the signal.

47. A method according to claim 35, wherein the signal is modulated by Frequency Division Modulation (FDM) over a wide band of frequencies, and wherein removing the jamming interference comprises removing the interference that is due to transmission of a narrowband jamming signal at the frequency within the wide band of the FDM signal.