def receive_prefix(symbols):
S = common.take(symbols, len(train.prefix))[:, config.carrier_index]
sliced = np.round(S)
if pylab:
pylab.figure()
show.constellation(S, sliced, 'Prefix')
bits = np.array(np.abs(sliced), dtype=int)
if any(bits != train.prefix):
raise ValueError('Incorrect prefix')
log.info('Prefix OK')
nonzeros = np.array(train.prefix, dtype=bool)
pilot_tone = S[nonzeros]
phase = np.unwrap(np.angle(pilot_tone)) / (2 * np.pi)
indices = np.arange(len(phase))
a, b = sigproc.linear_regression(indices, phase)
freq_err = a / (config.Tsym * config.Fc)
last_phase = a * indices[-1] + b
log.debug('Current phase on carrier: %.3f', last_phase)
expected_phase, = set(np.angle(sliced[nonzeros]) / (2 * np.pi))
log.debug('Excepted phase on carrier: %.3f', expected_phase)
sampling_err = (last_phase - expected_phase) * config.Nsym
log.info('Frequency error: %.2f ppm', freq_err * 1e6)
log.info('Sampling error: %.2f samples', sampling_err)
return freq_err, sampling_err
def test_linreg():
x = np.array([1, 3, 2, 8, 4, 6, 9, 7, 0, 5])
a, b = 12.3, 4.56
y = a * x + b
a_, b_ = sigproc.linear_regression(x, y)
assert abs(a - a_) < 1e-10
assert abs(b - b_) < 1e-10
