Classifier

Snapshot wideband classification

go2MONITOR offers different tools for automatic tuning and decoding of signals, a big advantages compared to other decoders where you are fixed to one work flow.

The tools used are:

  • Continuous narrow-band classifier (provided in the production channel)
  • Snapshot classifier, provided in the spectrum (spectrogram/FFT) display
  • Continuous wideband classification provided in the spectrum (spectrogram/FFT) display in Automatic Monitoring and Tasking  (Option) mode
  • Recognition (provided in the production channel)

Classifier Operating Modes

Classifier Source Classification max. Span max. Signal Bandwidth Timeout
Narrowband Classifier Channel Continuous 300 kHz HF: 20 kHz
VUHF: 50 kHz
No
Snapshot Classifier RX-IQ stream
File
Snapshot 1 MHz HF: 20 kHz
VUHF: 50 kHz
No
Continuous Classifier
(requires AMT)
RX-IQ stream
File
Continuous 1 MHz HF: 20 kHz
VUHF: 50 kHz
3-5 sec
Wideband Classifier
(Option)
RX-IQ stream
File
Snapshot
Continuous (requires AMT)
Scanning
Stepping
HF: 2.4 MHz
VUFH: 20 MHz
HF: 20 kHz
VUHF: 50 kHz
3-5 sec

Modulation classification is defined as the process of deciding, based on analysis on the received spectrum, what modulations are being used at the different transmitters. It is an important component of non-cooperative communications monitoring in which a listener desires to intercept unknown signals.

  • The continuous classifier has a big advantage compared to some other classifiers as it tracks each emission from beginning to the end, measures continuously all emission parameters and delivers emission information updates in ~4s time intervals. Using the full signal history is essential to improve the quality of the results. Additionally you get also exact information about the start and end of the emission.
  • The narrowband classifier will only classify one signal in the production channel.
  • The snapshot classifier can classify the selected frequency range and presents you a filtered list of available stations in the selected spectrum. You can assign the signal to a production channel by using drag-and-drop or using the context menu. In the snapshot mode, only a 4s period from the continuous signal input is processed and emission info delivered.
  • The wideband classifier (option) can:
    • Continuously classify the selected frequency range
    • Steps thru a frequency range and stores the result using the option "Automatic Monitoring and Tasking"
    • Scans thru a frequency range and stores the result using the option "Automatic Monitoring and Tasking". This mode requires receivers that can do independent scanning and only stop if the find a signal (Advantage: faster than stepping)

Recognition and Decoding

In recognition mode, the production channel uses a configurable list of decoders and checks in parallel which one of these decoders is in accordance to the received signal. If a usable decoder is found, then the signal is demodulated, decoded and the results are displayed in the result view.

Multiple decoder lists can be configured and modified. Depending on the task, the list can be configured with the required decoders.

During recognition and decoding the production channel is running in a continuous loop:

    • Detection of the signal in range predefined around the center frequency.
    • Check of all decoders in the modem list
    • If a match exists, the decoder starts and delivers output
    • Start again from the beginning, if the end of transmission is detected or the decoder is no longer able to decode the signal
The advantages are:
  • No missing output if the protocol or modem will change during a transmission. Scenarios with ALE, then traffic in STANAG 4285 and later change to PACOR-III require no operator interaction
  • No missing output if the frequency is changed inside the predefined range

Why not put all decoders in one big modem list and just use this one? This is possible if you have to analyze signals, but is not recommended. If multiple signals have to be decoded at the same time, then this setup requires unnecessary processing power. Does it make sense to check for VHF/UHF protocols if you run in the HF range? Many decoders are outdated or not required in your area. Just disable this protocols in your list. This will speed up the recognition, lowers the CPU usage and also reduces the possibility of wrong detections.

Classification, Recognition and Decoding

Classification, recognition and decoding

Classification, recognition and decoding works similar as recognition and decoding.

During classification, recognition and decoding the production channel is running in a continuous loop:

  1. Classify the signal in the range predefined around the center frequency
  2. Detection of the signal.
  3. With the information (modulation, symbol-rate, shift etc,) of the classification, a dynamic modem list is prepared containing only the decoders that fulfill the criteria of the classifier result. Such a list is much shorter than a modem list containing all the decoders.
  4. Check of all decoders in the dynamic modem list
  5. If a usable decoder is found, then the signal is demodulated, decoded and the results are displayed in the result view. All this operations are buffered to avoid any loss of data
  6. Start again from the beginning, if the end of transmission is detected, the decoder is no longer able to decode the signal or if the classifier detects a new modulation.
The advantages are:
  • Sometimes faster than recognition and decoding
  • Requires less processing power, compared to recognition and decoding
  • No missing output if the protocol or modem will change during a transmission. Scenarios with ALE, then traffic in STANAG 4285 and later change to PACTOR-III require no operator interaction.
  • No missing output, if the frequency is changed inside the predefined range
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