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Add AWGN channel models and route IMDD simulation through them

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This commit is contained in:
Silas Oettinghaus
2026-03-26 11:23:07 +01:00
parent d3235a5c9c
commit c135cb76b1
7 changed files with 167 additions and 68 deletions
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32
Functions/Channel_structures/awgn_alpha_d_channel.m Normal file
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@@ -0,0 +1,32 @@
function signal_out = awgn_alpha_d_channel(signal_in, options)
%AWGN_ALPHA_D_CHANNEL Apply a 1 + alpha*D FIR channel followed by AWGN.
arguments
signal_in
options.alpha (1,1) double = 0
options.delay_samples (1,1) double {mustBeInteger, mustBePositive} = 1
options.snr_dB (1,1) double = 20
options.randkey = []
end
signal_out = signal_in;
taps = zeros(1, options.delay_samples + 1);
taps(1) = 1;
taps(end) = options.alpha;
signal_out.signal = filter(taps, 1, signal_in.signal, [], 1);
if isa(signal_out, 'Signal')
desc = sprintf('1 + alpha*D channel with alpha %.4f and delay %d samples', ...
options.alpha, options.delay_samples);
meta = struct( ...
'alpha', options.alpha, ...
'delay_samples', options.delay_samples);
signal_out = signal_out.logbookentry(desc, meta);
end
signal_out = awgn_channel(signal_out, ...
"snr_dB", options.snr_dB, ...
"randkey", options.randkey);
end

46
Functions/Channel_structures/awgn_channel.m
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@@ -1,5 +1,43 @@
function signal_out = awgn_channel(signal_in)
function signal_out = awgn_channel(signal_in, options)
%AWGN_CHANNEL Apply additive white Gaussian noise to a signal object.
arguments
signal_in
options.snr_dB (1,1) double = 20
options.randkey = []
end
signal_out = signal_in;
end
x = signal_in.signal;
signalPower = mean(abs(x).^2, 'all'); %or use signal_in.power
if signalPower == 0
return
end
snrLinear = 10^(options.snr_dB/10);
noisePower = signalPower / snrLinear;
if isempty(options.randkey)
if isreal(x)
noise = sqrt(noisePower) * randn(size(x));
else
noise = sqrt(noisePower / 2) * (randn(size(x)) + 1i * randn(size(x)));
end
else
rs = RandStream('mt19937ar', 'Seed', options.randkey);
if isreal(x)
noise = sqrt(noisePower) * randn(rs, size(x));
else
noise = sqrt(noisePower / 2) * (randn(rs, size(x)) + 1i * randn(rs, size(x)));
end
end
signal_out.signal = x + noise;
if isa(signal_out, 'Signal')
desc = sprintf('AWGN channel with SNR %.2f dB', options.snr_dB);
meta = struct('snr_dB', options.snr_dB, 'randkey', options.randkey);
signal_out = signal_out.logbookentry(desc, meta);
end
end

6
Functions/EQ_structures/dsp_scope_signal.m
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@@ -47,12 +47,12 @@ function output = dsp_scope_signal(Scpe_sig_raw, Symbols, Tx_bits, options)
use_dd_mode = 1;
use_ffe = 1;
use_dfe = 1;
use_dfe = 0;
use_vnle_mlse = 0;
use_dbtgt = 0;
use_dbenc = 0;
use_ml_mlse = 0;
showAnalysis = 0;
showAnalysis = 1;
decoding_mode = [];
addProcessingResultToDatabase = 0; %#ok<NASGU>
@@ -102,7 +102,7 @@ function output = dsp_scope_signal(Scpe_sig_raw, Symbols, Tx_bits, options)
"eth_style_symbol_mapping", 0);
ffe_results.config.equalizer_structure = "ffe";
ffe_results.metrics.print;
ffe_results.metrics.print("description",'FFE');
output.ffe_package = ffe_results;
end