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WO2025126695A1 - Système de détection d'interférences, équipement radio et procédé de détection d'interférences - Google Patents

Système de détection d'interférences, équipement radio et procédé de détection d'interférences Download PDF

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Publication number
WO2025126695A1
WO2025126695A1 PCT/JP2024/038278 JP2024038278W WO2025126695A1 WO 2025126695 A1 WO2025126695 A1 WO 2025126695A1 JP 2024038278 W JP2024038278 W JP 2024038278W WO 2025126695 A1 WO2025126695 A1 WO 2025126695A1
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Prior art keywords
wave
main
interference
main wave
frequency
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PCT/JP2024/038278
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English (en)
Japanese (ja)
Inventor
雅美 豊永
昌志 内藤
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Kokusai Denki Electric Inc
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Hitachi Kokusai Electric Inc
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Publication of WO2025126695A1 publication Critical patent/WO2025126695A1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/309—Measuring or estimating channel quality parameters
    • H04B17/345—Interference values

Definitions

  • the present invention relates to technology for detecting interference caused by multiple radio stations simultaneously transmitting radio waves at the same frequency.
  • Air traffic control radio communications there are concerns about problems caused by interference. Interference occurs at the receiving end when different radio stations simultaneously transmit radio waves at the same frequency. Traditionally, the presence or absence of interference has been determined by the human ear. Air traffic control radio communications use amplitude (AM) modulation, and in the event of interference, audio overlap or abnormal sounds occur at the receiving end. Based on this, humans have been able to determine the presence or absence of interference, preventing serious incidents from occurring.
  • AM amplitude
  • Patent Document 1 discloses a wireless system that converts a received signal into a frequency-level relationship using FFT processing, detects peak power from the result, and determines the interference state based on the number of peaks.
  • the present invention was made in consideration of the above-mentioned conventional circumstances, and aims to make it possible to more accurately detect interference that occurs when multiple wireless stations simultaneously transmit radio waves of the same frequency.
  • an interference detection system for detecting interference caused by multiple wireless stations simultaneously transmitting radio waves of the same frequency, and is characterized by comprising a main wave estimation unit that estimates a main wave AM modulated wave based on the frequency of the main wave in a received radio wave that includes at least a main wave and the AM component of the received radio wave, a filter unit that removes the main wave AM modulated wave from the received radio wave, and an interference detection unit that detects the occurrence of interference based on the output of the filter unit.
  • the main wave estimation unit includes an FFT unit that performs FFT processing on the received radio waves, a main wave frequency detection unit that detects the frequency of the main wave based on the result of the FFT processing, a main wave CW generation unit that generates a main wave CW based on the frequency of the main wave, an AM component extraction unit that extracts the AM component of the received radio waves, and a multiplier that multiplies the main wave CW by the AM component, and can operate to output the multiplication result by the multiplier as the main wave AM modulated wave.
  • the interference detection system described above can operate to detect the occurrence of interference if a peak exists at any frequency in the output of the filter section.
  • a radio has the following technical features. That is, the radio has a function for detecting interference caused by multiple radio stations simultaneously transmitting radio waves of the same frequency, and is characterized by having a main wave estimation unit that estimates a main wave AM modulated wave based on the frequency of the main wave in a received radio wave that includes at least a main wave and the AM component of the received radio wave, a filter unit that removes the main wave AM modulated wave from the received radio wave, and an interference detection unit that detects the occurrence of interference based on the output of the filter unit.
  • the interference detection method is for detecting interference caused by multiple wireless stations simultaneously transmitting radio waves of the same frequency, and is characterized by having a step of estimating a main wave AM modulated wave based on the frequency of the main wave in a received radio wave that includes at least the main wave and the AM component of the received radio wave, a step of removing the main wave AM modulated wave from the received radio wave, and a step of detecting the occurrence of interference based on the output of the filter unit.
  • the present invention makes it possible to more accurately detect interference that occurs when multiple radio stations simultaneously transmit radio waves at the same frequency.
  • FIG. 13 is a diagram showing an example waveform of a primary CW(t).
  • FIG. 13 is a diagram showing an example of convergence transition of the canceller output e(t) when the frequency estimation error of the main wave CW(t) is 0 Hz.
  • FIG. 13 is a diagram showing an example of convergence transition of the canceller output e(t) when the frequency estimation error of the main wave CW(t) is 4 Hz.
  • 11 is a diagram showing a comparative example of the spectrum of a received radio wave Rx(t) and a canceller output e(t).
  • FIG. 1 shows an overview of an air traffic control system to which the present invention is applied.
  • the illustrated air traffic control system has stations A and B, which are aircraft, and station C, which is a control station.
  • stations A and B simultaneously start transmitting radio waves at the same frequency F1 and station C receives these radio waves, it is assumed that the received power level of the signal from station B is 20 dB or more higher than that of the signal from station A.
  • the signal from station A is buried in the signal from station B, making it difficult to hear the received voice from station B by hearing.
  • the present invention provides a technology that makes it possible to detect the occurrence of interference without relying on hearing.
  • the received wave with the higher received power at the receiving side when interference occurs is described as the "main wave” and the received wave with the lower received power is described as the "interference wave”.
  • FIG. 2 shows an example of the configuration of an interference detection system according to one embodiment of the present invention.
  • the illustrated interference detection system comprises a main wave estimation unit 10, an adaptive filter unit 20, and an interference detection unit 30.
  • the main wave estimation unit 10 includes an FFT unit 11, a main wave frequency detection unit 12, a main wave CW generation unit 13, an AM component detection unit 14, and a multiplier 15.
  • the adaptive filter unit 20 includes a tap update unit 21, an FIR filter 22, and an adder 23.
  • the received radio wave signal Rx(t) (hereinafter referred to as received radio wave Rx(t)) input to the interference detection system is assumed to be a quadrature detection signal (I/Q) consisting of an in-phase component and a quadrature-phase component.
  • t is the sampling time.
  • a received radio wave Rx(t) including at least a main wave is input to the main wave estimation unit 10.
  • the main wave estimation unit 10 estimates the main wave AM modulated wave as follows. First, the received radio wave Rx(t) is subjected to FFT (Fast Fourier Transform) processing by the FFT unit 11, the main wave frequency detection unit 12 detects the main wave frequency, and the main wave CW (Constant Wave) is generated by the main wave CW generation unit 13.
  • FFT Fast Fourier Transform
  • the AM component extraction unit 14 extracts the AM (amplitude) component of the received radio wave Rx(t), and the main wave CW(t) is multiplied by the AM component (t) in the multiplier 15.
  • the main wave estimation unit 10 outputs the multiplication result by the multiplier 15 as an estimated main wave AM modulated wave (hereinafter referred to as the "temporary main wave AM modulated wave") AM_m(t).
  • the received radio wave Rx(t) actually contains interference wave components, but the interference waves can be assumed to be sufficiently small compared to the main wave (for example, a level difference of 20 dB or more), so the provisional AM modulated wave AM_m(t) can be regarded as approximately the AM modulated wave of the main wave.
  • a one-tap adaptive filter (adaptive filter section 20 shown in the figure) is configured with the provisional AM-modulated wave AM_m(t) obtained in this way as the desired wave.
  • the adaptive filter section 20 minimizes the error e(t) using an LMS (Least Mean Square) algorithm, so that the interference wave components from which the main AM-modulated wave contained in the received radio wave Rx(t) has been removed are output from the adaptive filter section 20 as a canceller output e(t).
  • the adaptive filter section 20 performs beat cancellation to cancel the beat (waveform fluctuation) of the received radio wave Rx(t), and the canceller output e(t) is monitored by the interference wave detection section 70, making it possible to detect the occurrence of interference with high accuracy.
  • each signal in the following description is a complex signal (A real + j ⁇ A image ).
  • FFT processing (windowing not required) is performed on the received radio wave Rx(t) including at least the main wave.
  • each subcarrier component (complex signal) resulting from the FFT processing is represented as FFT(n).
  • n indicates the subcarrier number and is an integer value ranging from 1 to 4096.
  • FFT processing is performed with a sampling frequency of 8.802 kHz and an FFT size of 4096. In this case, the frequency resolution (subcarrier interval) is about 2.15 Hz.
  • the main wave frequency detection section 12 finds the subcarrier number nmax with maximum power.
  • the main wave CW generation section 13 selects a predetermined number of subcarriers around the subcarrier number nmax with maximum power.
  • iFFT inverse Fast Fourier Transform
  • Figure 3 shows an example of the waveforms of the I and Q values of the primary CW(t).
  • the primary CW(t) is generated using only some selected subcarriers, select_SC, rather than all subcarriers, so as shown in Figure 3, the primary CW(t) does not have a constant envelope. Note that Figure 3 shows the case where the CW frequency is ⁇ 8.802 kHz/4096.
  • the main wave CW generating unit 13 performs delay detection on one sample using data from the generated primary CW(t) excluding both attenuated sides, and calculates the phase rotation amount delayed_phase per sample.
  • the main wave CW generating unit 13 performs an ATAN (arc tangent) transformation of the obtained phase rotation amount delayed_phase to obtain the angular velocity ⁇ per sample, and then performs an exp(j ⁇ t) transformation to generate CW(t).
  • ATAN arc tangent
  • (b) Extraction process of AM component of received radio wave Rx(t)
  • abs(Rx(t)) is a function that obtains the absolute value of Rx(t).
  • the adaptive filter unit 20 performs adaptive filter processing based on the received radio wave Rx(t) and the tentative main wave AM modulated wave AM_m(t). Specifically, the tap update unit 21 generates a tap coefficient h(t) of one tap based on the tentative main wave AM modulated wave AM_m(t) and the canceller output e(t-1) one time ago, and sets (updates) the tap coefficient of the FIR filter 22. Next, the FIR filter 22 multiplies the tentative main wave AM modulated wave AM_m(t) by the tap coefficient h(t) to calculate the equalization output C(t). After that, the adder 23 adds the received radio wave Rx(t) and the equalization output C(t), and outputs the result as the canceller output e(t).
  • the equalization output C(t), the canceller output e(t), and the tap coefficient h(t) are calculated by the following calculations.
  • * denotes a complex conjugate.
  • ⁇ step gain
  • ⁇ step gain
  • Figures 4A and 4B show examples of the convergence transition of the canceller output e(t).
  • the LMS algorithm causes the main wave level to become almost zero after about 50 samples are updated, and only the interference wave remains.
  • FIG. 5 shows a comparative example of the spectrum of the received radio wave Rx(t) before beat cancellation and the canceller output e(t) after beat cancellation.
  • the spectral waveforms before and after beat cancellation have been adjusted so that the zero frequency is at the center.
  • the D/U ratio of the interference wave peak is about 10 dB due to the bandwidth broadening caused by AM modulation.
  • the D/U ratio of the interference wave peak improves to about 40 dB (however, the absolute amount is attenuated by about 10 dB due to beat cancellation).
  • the spectrum waveform after beat cancellation clearly shows a peak of the interference wave at a different frequency (-200 Hz in the illustrated example) from the peak frequency of the main wave (100 Hz in the illustrated example). Therefore, the interference detection unit 30 monitors the canceller output e(t) and determines whether a peak exists at any frequency, making it possible to detect the occurrence of interference.
  • the interference detection unit 30 detects, for example, a frequency at which a level fluctuation of a predetermined threshold or more occurs as the peak frequency of the interference wave and determines that interference has occurred.
  • the canceller output e(t) is obtained by removing the main wave component from the received radio wave Rx(t), but it is possible that the main wave component remains. Therefore, the occurrence of interference may be detected by confirming that the peak frequency detected from the canceller output e(t) is different from the peak frequency of the main wave.
  • beat cancellation in the adaptive filter section 20 causes a peak that appears to be intermodulation to occur at a frequency position that is symmetrical to the peak frequency of the interference wave with respect to the peak frequency of the main wave.
  • the purpose of beat cancellation is to be able to check whether there are peaks other than the main wave (check for the presence of interference waves), the presence of intermodulation does not pose a problem (in other words, there is no problem even if intermodulation is detected).
  • the interference detection system of this example includes a main wave estimation unit 10 that estimates the main wave AM modulated wave AM_m(t) based on the main wave frequency in the received radio wave Rx(t) that includes at least the main wave and the AM component (t) of the received radio wave Rx(t), an adaptive filter unit 20 that removes the main wave AM modulated wave AM_m(t) from the received radio wave Rx(t), and an interference detection unit 30 that detects the occurrence of interference based on the canceller output e(t) of the adaptive filter unit 20.
  • the main wave estimation unit 10 includes an FFT unit 11 that performs FFT processing on the received radio wave Rx(t), a main wave frequency detection unit 12 that detects the main wave frequency based on the result of the FFT processing, a main wave CW generation unit 13 that generates a main wave CW(t) based on the main wave frequency, an AM component extraction unit 14 that extracts the AM component (t) of the received radio wave, and a multiplier 15 that multiplies the main wave CW(t) by the AM component (t), and is configured to output the multiplication result by the multiplier 15 as a main wave AM modulated wave AM_m(t).
  • the interference detection unit 20 is configured to detect the occurrence of interference when a peak exists at any frequency in the canceller output e(t) of the adaptive filter unit 20.
  • This configuration makes it possible to more accurately detect interference that occurs when multiple radio stations simultaneously transmit radio waves at the same frequency. As a result, it becomes possible to more reliably prevent problems caused by interference in air traffic control radio communications, etc.
  • the present invention can be provided not only as the devices described above or as systems composed of these devices, but also as methods executed by these devices, programs for implementing the functions of these devices using a processor, and storage media for storing such programs in a computer-readable format.
  • the present invention can be used in air traffic control systems, where it is important to detect interference caused by multiple radio stations simultaneously transmitting radio waves at the same frequency.

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  • Engineering & Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Noise Elimination (AREA)

Abstract

La présente invention permet de détecter plus précisément des interférences provoquées par la transmission simultanée d'ondes radio de même fréquence par une pluralité de stations sans fil.　Un système de détection d'interférences selon un mode de réalisation de la présente invention comprend : une unité d'estimation d'onde principale (10) pour estimer une onde AM modulée par une onde temporaire AM_m(t) sur la base d'une fréquence d'onde principale d'une onde radio de réception Rx(t) comprenant au moins une onde principale et une composante AM (t) de l'onde radio de réception Rx(t) ; une unité de filtre adaptatif (20) pour éliminer l'onde AM modulée par l'onde temporaire AM_m(t) de l'onde radio de réception Rx(t); et une unité de détection d'interférences (30) pour détecter l'apparition d'interférences sur la base d'une sortie d'annulation e(t) de l'unité de filtre adaptatif (20).
PCT/JP2024/038278 2023-12-15 2024-10-28 Système de détection d'interférences, équipement radio et procédé de détection d'interférences Pending WO2025126695A1 (fr)

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JP2023211939 2023-12-15

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0865184A (ja) * 1994-08-16 1996-03-08 Yuseisho Tsushin Sogo Kenkyusho 干渉波検出方法
JP2003008497A (ja) * 2001-06-26 2003-01-10 Hitachi Ltd 混信警告装置
JP2017108350A (ja) * 2015-12-11 2017-06-15 シャープ株式会社 通信装置、通信方法、及びプログラム
US20200007248A1 (en) * 2017-03-31 2020-01-02 Continental Automotive France Method and sensor for detecting the presence of co-channel jamming
WO2022180676A1 (fr) * 2021-02-24 2022-09-01 株式会社日立国際電気 Dispositif radio

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0865184A (ja) * 1994-08-16 1996-03-08 Yuseisho Tsushin Sogo Kenkyusho 干渉波検出方法
JP2003008497A (ja) * 2001-06-26 2003-01-10 Hitachi Ltd 混信警告装置
JP2017108350A (ja) * 2015-12-11 2017-06-15 シャープ株式会社 通信装置、通信方法、及びプログラム
US20200007248A1 (en) * 2017-03-31 2020-01-02 Continental Automotive France Method and sensor for detecting the presence of co-channel jamming
WO2022180676A1 (fr) * 2021-02-24 2022-09-01 株式会社日立国際電気 Dispositif radio

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