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5117fc58 AIL |
1 | function demodData = deqpskdemod(modData) |
2 | %% Input: Rx samples from a DE-QPSK constellation. | |
3 | %% Output: Data as integers between 0 to 3 inclusive. | |
4 | %% Parameter formats are the same as MATLAB's "pskdemod" function. | |
5 | ||
6 | %% MATLAB has no easy way to perform just the decision stage, | |
7 | % so here we demodulate and then remodulate to get the closest symbols. | |
8 | demod1 = pskdemod(modData, 4, 0, 'gray'); | |
9 | remod = pskmod(demod1, 4, 0, 'gray'); | |
10 | ||
11 | clear demod1; % save some memory | |
12 | ||
13 | [~, wavelength_channels] = size(modData); | |
14 | %% Instead of looping through the symbols, it will be faster | |
15 | % to vectorize the operation. So we create an array that is | |
16 | % delayed by 1 sample. | |
17 | delayed = [ones(1, wavelength_channels); remod(1:end-1, :)]; | |
18 | demodData = uint8(pskdemod(remod .* conj(delayed), 4, 0, 'gray')); | |
19 | end |