3.1 Frequency synchronization (receiver) (matlab)

%% Frequency Synchronization (RECEIVER) % ------------------------------------------------------------------------% Description: This module attempts to correct the frequency/phase offset % in the recovered signal by estimating it as a static phase% offset. Though there may be a frequency offset or even a % frequency drift, for BPSK, estimating this as a fixed phase% offset is sufficient in recovering the bits. More often % than not this corrects the recovered bits when they're% inverted (estimated as a pi phase offset). This uses the % same metric as the timing recovery to find the phase.% % Inputs: train - Received training symbol% train_expected - Expected training symbol via a priori knowledge % Outputs: phi - Estimated phase offsetfunction phi = fsync(train, train_expected)%% L = size(train,2); % Size of window for algorithmP = 0; % Initialize the metricfor n=1:L P = P + conj(train(n))*train_expected(n);% Sample by sample multiplication of the complex conjugate of the % received training symbol with the expected training symbol. If% both of them are in phase, the imaginary components would % annhiliate each other. However, if there's a phase offset% between the two, it will be represented in the angle of the % resulting product.end phi = angle(P);end