Class: PWN::SDR::Decoder::GSM::DemodIQ

Inherits:
Object
  • Object
show all
Defined in:
lib/pwn/sdr/decoder/gsm.rb

Overview

Streaming I/Q energy/burst demod for Base.run_iq.

Instance Method Summary collapse

Constructor Details

#initialize(rate:, protocol:, modulation:, extra: {}) ⇒ DemodIQ

Returns a new instance of DemodIQ.



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# File 'lib/pwn/sdr/decoder/gsm.rb', line 10

def initialize(rate:, protocol:, modulation:, extra: {})
  @rate = rate.to_f
  @protocol = protocol
  @modulation = modulation
  @extra = extra
  @floor = nil
  @in_burst = false
  @burst_t0 = nil
  @peak = -200.0
  @burst_n = 0
  @threshold = (extra[:threshold] || 8.0).to_f
  @carry = []
end

Instance Method Details

#feed_iq(samples, rate: nil) ⇒ Object 



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# File 'lib/pwn/sdr/decoder/gsm.rb', line 24

def feed_iq(samples, rate: nil, &)
  @rate = rate.to_f if rate
  m2 = PWN::SDR::Decoder::DSP.mag_sq(iq: samples)
  # process in ~1 ms hops
  hop = [(@rate / 1000.0).round, 1].max
  i = 0
  while i < m2.length
    win = m2[i, hop]
    break if win.nil? || win.empty?

    ms = win.sum / win.length
    lvl = ms.positive? ? (10.0 * Math.log10(ms)) : -120.0
    @floor = @floor.nil? ? lvl : ((@floor * 0.98) + (lvl * 0.02))
    delta = lvl - @floor
    if delta >= @threshold
      unless @in_burst
        @in_burst = true
        @burst_t0 = Time.now
        @peak = lvl
      end
      @peak = lvl if lvl > @peak
    elsif @in_burst
      @in_burst = false
      @burst_n += 1
      dur_ms = ((Time.now - @burst_t0) * 1000).round
      msg = {
        protocol: @protocol, event: 'burst', source: 'iq',
        burst_no: @burst_n, peak_dbfs: @peak.round(1),
        floor_dbfs: @floor.round(1), delta_db: (@peak - @floor).round(1),
        duration_ms: dur_ms, modulation: @modulation,
        sample_rate: @rate.to_i
      }.merge(@extra)
      msg[:summary] = format(
        '%<p>s IQ-burst #%<n>d peak=%<pk>+.1f dBFS Δ=%<d>.1f dB dur=%<ms>d ms',
        p: @protocol, n: @burst_n, pk: @peak, d: @peak - @floor, ms: dur_ms
      )
      yield msg if block_given?
    end
    i += hop
  end
end