mirror of
https://github.com/hb9fxq/gr-digitalhf
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81 lines
3.1 KiB
Python
81 lines
3.1 KiB
Python
## -*- python -*-
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import numpy as np
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from gnuradio import digital
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class PhysicalLayer(object):
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"""Physical layer description for STANAG 4285"""
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def __init__(self, mode=0):
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"""For STANAG 4258 the mode has to be set manually: mode=0 -> BPSK, mode=1 -> QPSK, mode=2 -> 8PSK"""
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self._constellations = [PhysicalLayer.make_psk(2, [0,1]),
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PhysicalLayer.make_psk(4, [0,1,3,2]),
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PhysicalLayer.make_psk(8, [1,0,2,3,6,7,5,4])]
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self._preamble = [PhysicalLayer.get_preamble(), 0] ## BPSK
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self._data = [PhysicalLayer.get_data(), mode] ## according to the mode
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self._counter = 0
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def set_mode(self):
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"""For STANAG 4258 the mode has to be set manually: mode=0 -> BPSK, mode=1 -> QPSK, mode=2 -> 8PSK"""
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self._data[1] = mode
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def get_constellations(self):
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return self._constellations
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def get_frame(self):
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"""returns the known+unknown symbols and scrambling"""
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if self._counter == 0:
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return self._preamble
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else:
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return self._data
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def get_doppler(self): ## symbols
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"""used for doppler shift update, for determining which frame to provide next,
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and for stopping at end of data/when the signal quality is too low"""
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self._counter = (self._counter+1)&1
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## TODO: doppler calculations
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doppler = 0.1234
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return [True, doppler]
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@staticmethod
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def get_preamble():
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"""preamble symbols + scrambler(=1)"""
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state = np.array([1,1,0,1,0], dtype=np.bool)
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taps = np.array([0,0,1,0,1], dtype=np.bool)
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p = np.zeros(80, dtype=np.uint8)
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for i in range(80):
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p[i] = state[-1]
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state = np.concatenate(([np.sum(state&taps)&1], state[0:-1]))
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a = np.zeros(80, dtype=[('symb',np.complex64), ('scramble', np.complex64)])
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## BPSK modulation
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constellation = PhysicalLayer.make_psk(2,range(2))['points']
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a['symb'] = constellation[p,]
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a['scramble'] = 1
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return a
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@staticmethod
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def get_data():
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"""data symbols + scrambler; for unknown symbols 'symb'=0"""
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state = np.array([1,1,1,1,1,1,1,1,1], dtype=np.bool)
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taps = np.array([0,0,0,0,1,0,0,0,1], dtype=np.bool)
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p = np.zeros(176, dtype=np.uint8)
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for i in range(176):
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p[i] = np.sum(state[-3:]*[4,2,1])
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for j in range(3):
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state = np.concatenate(([np.sum(state&taps)&1], state[0:-1]))
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a=np.zeros(176, dtype=[('symb',np.complex64), ('scramble', np.complex64)])
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## PSK-8 modulation
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constellation = PhysicalLayer.make_psk(8,range(8))['points']
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a['scramble'] = constellation[p,]
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a['symb'][ 32: 48] = 1 ## mini-probe 1
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a['symb'][ 80: 96] = 1 ## mini-probe 2
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a['symb'][128:144] = 1 ## mini-probe 3
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return a
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@staticmethod
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def make_psk(n, gray_code):
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c = np.zeros(n, dtype=[('points', np.complex64), ('symbols', np.uint8)])
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c['points'] = np.exp(2*np.pi*1j*np.array(range(n))/n)
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c['symbols'] = gray_code
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return c
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