mskmod

Minimum shift keying modulation

Syntax

y = mskmod(x,nsamp)
y = mskmod(x,nsamp,dataenc)
y = mskmod(x,nsamp,dataenc,ini_phase)
[y,phaseout] = mskmod(...)


Description

y = mskmod(x,nsamp) outputs the complex envelope y of the modulation of the message signal x using differentially encoded minimum shift keying (MSK) modulation. The elements of x must be 0 or 1. nsamp denotes the number of samples per symbol in y and must be a positive integer. The initial phase of the MSK modulator is 0. If x is a matrix with multiple rows and columns, the function treats the columns as independent channels and processes them independently.

y = mskmod(x,nsamp,dataenc) specifies the method of encoding data for MSK. dataenc can be either 'diff' for differentially encoded MSK or 'nondiff' for nondifferentially encoded MSK.

y = mskmod(x,nsamp,dataenc,ini_phase) specifies the initial phase of the MSK modulator. ini_phase is a row vector whose length is the number of channels in y and whose values are integer multiples of pi/2. To avoid overriding the default value of dataenc, set dataenc to [].

[y,phaseout] = mskmod(...) returns the final phase of y. This is useful for maintaining phase continuity when you are modulating a future bit stream with differentially encoded MSK. phaseout has the same dimensions as the ini_phase input, and assumes the values 0, pi/2, pi, and 3*pi/2.

Examples

Eye Diagram of MSK Signal

Generate a random binary signal.

x = randi([0 1],100,1);

MSK modulate the data.

y = mskmod(x,8,[],pi/2);

Pass the signal through an AWGN channel. Display the eye diagram.

z = awgn(y,30,'measured');
eyediagram(z,16);

References

[1] Pasupathy, Subbarayan, “Minimum Shift Keying: A Spectrally Efficient Modulation,” IEEE Communications Magazine, July, 1979, pp. 14–22.