david/python-ofdm
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added error

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This commit is contained in:
David Lenfesty 2019-08-25 19:00:49 -06:00
parent f701c204c6
commit 71a6045885
2 changed files with 14 additions and 4 deletions
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12
channel.py
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@ -2,12 +2,22 @@ import numpy as np
channel_response = np.array([0, 0, 0, 1, 0, 0, 0]) channel_response = np.array([0, 0, 0, 1, 0, 0, 0])
# 15dB seems to be around the minimum for error-free transmission
snr_db = 15
def sim(in_data): def sim(in_data):
out_data = np.ndarray((len(in_data), len(in_data[0])), dtype=np.csingle) out_data = np.ndarray((len(in_data), len(in_data[0])), dtype=np.csingle)
# noise stuff is straight copied from the DSP illustrations article
for i in range(len(in_data)): for i in range(len(in_data)):
convolved = np.convolve(channel_response, in_data[i], mode='same') convolved = np.convolve(channel_response, in_data[i], mode='same')
out_data[i] = convolved
signal_power = np.mean(abs(convolved**2))
noise_power = signal_power * 10**(-snr_db/10)
noise = np.sqrt(noise_power / 2) * (np.random.randn(*convolved.shape) + 1j*np.random.randn(*convolved.shape))
out_data[i] = convolved + noise
return out_data return out_data

6
main.py
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@ -7,7 +7,7 @@ Hopefully eventually this modem design makes it onto an fpga.
TODO: TODO:
Add comments for functions Add comments for functions
Explain what the main function is doing Explain what the main function is doing
Finish doing the channel simulation stuff (add noise, and verify channel response) Add more errors, like a shifted signal
Add support for 16-QAM, 64-QAM, etc... Add support for 16-QAM, 64-QAM, etc...
Add channel estimation via pilot carriers Add channel estimation via pilot carriers
Add some sort of payload support, i.e. be able to drop the padding at the end Add some sort of payload support, i.e. be able to drop the padding at the end
@ -48,7 +48,7 @@ if __name__ == '__main__':
bytes = bytearray(data, 'utf8') bytes = bytearray(data, 'utf8')
parallel = parallelise(16, bytes) parallel = parallelise(64, bytes)
modulated = qam.modulate(parallel) modulated = qam.modulate(parallel)
@ -66,6 +66,6 @@ if __name__ == '__main__':
to_serialise = qam.demodulate(to_decode) to_serialise = qam.demodulate(to_decode)
data = serialise(16, to_serialise) data = serialise(64, to_serialise)
print(data) print(data)