Demodulate DPSK data in a communication channel in which a phase shift is introduced.
Generate a 4-ary data vector and modulate it using DPSK.
M = 4; % Alphabet size
dataIn = randi([0 M-1],1000,1); % Random message
txSig = dpskmod(dataIn,M); % Modulate
Apply the random phase shift resulting from the transmission process.
rxSig = txSig*exp(2i*pi*rand());
Demodulate the received signal.
dataOut = dpskdemod(rxSig,M);
The modulator and demodulator have the same initial condition. However, only the received signal experiences a phase shift. As a result, the first demodulated symbol is likely to be in error. Therefore, you should always discard the first symbol when using DPSK.
Find the number of symbol errors.
errs = symerr(dataIn,dataOut)
errs =
1
One symbol is in error. Repeat the error calculation after discarding the first symbol.
DPSK-modulated input signal, specified as a real or complex
vector or matrix. If y is a matrix, the function
processes the columns independently.
Data Types: double Complex Number Support: Yes
Modulation order, specified as an integer power of two.
Example: 2 | 4 | 16
Data Types: double
Phase rotation of the DPSK modulation, specified in radians
as a real scalar. The total phase shift per symbol is the sum of phaserot and
the phase generated by the differential modulation.
If you specify phaserot as empty, then dspkdemod uses
a phase rotation of 0 degrees.
Example: pi/4
Data Types: double
Symbol order, specified as 'bin' or 'gray'.
This argument specifies how the function assigns binary vectors to
corresponding integers.
If symorder is 'bin',
the function uses a binary-coded ordering.
If symorder is 'gray',
the function uses a Gray-coded ordering.
DPSK-demodulated output signal, returned as a vector or matrix
having the same number of columns as input signal y.
Note
The differential algorithm used in this function compares two
successive elements of a modulated signal. To determine the first
element of vector z, or the first row of matrix z,
the function uses an initial phase rotation of 0.
