GMSK modulation in MATLAB
This page of MATLAB source code covers GMSK modulation.
GMSK is the short form of Gaussian Minimum Shift Keying. It is modulation technique used in wireless systems. With GMSK modulation continuous or zero phase shift can be achieved between the consecutive two data symbols. GMSK has been devised to overcome problem of QPSK, OQPSK techniques which will have 180 degree to 90 degree of phase shifts between two symbols. This abrupt phase shift will make it necessary to use linear power amplifier in the wireless transmitter chain at the later stage. Refer our page on MSK GMSK modulation for complete step by step guide on MSK and GMSK modulation types.
Following is the basic GMSK modulation matlab code.
GMSK MATLAB CODE
nrz_data = [1 1 1 1 1 1 1 1]; %sample data
Tb = 1; % bit duration
BT = 0.3; % BT product of filter
sps = 32; % samples per symbol
Ts = Tb/sps; % sample period
alpha = 2*pi*BT/(sqrt(log(2)));
gauss = Q(alpha*(2*t-0.5)) - Q(alpha*(2*t+0.5));
gauss = K*gauss;
nrz = upsample(nrz_data,sps);
nrz_gauss = conv(gauss,nrz);
subplot(2,1,2);plot(nrz_gauss);title('NRZ bits, after Gaussian Filtering');xlabel('Time');ylabel('Amplitude');
nrz_gauss1 = cumsum(nrz_gauss);
nrz_gauss2 = exp(1i*nrz_gauss1);
noisy_real1 = real(nrz_gauss2);
noisy_imag1 = imag(nrz_gauss2);
filter_noisy_real1 = matched_filter(noisy_real1,Tb,sps);
filter_noisy_imag1 = matched_filter(noisy_imag1,Tb,sps);
Deconvolution is performed in GMSK demodulation with the same gaussian filter coefficients generated in the GMSK modulation.
Useful Links to MATLAB codes
Refer following as well as links mentioned on left side panel for useful MATLAB codes.
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