The two objects gmksmod and gmskdem implement the Gauss minimum-shift keying (GMSK) modem in liquid. Notice that unlike the linear modem objects, the GMSK modulator and demodulator are split into separate objects.

http://liquidsdr.org/doc/gmskmodem/

Shown in the figure below is a compaarison of the transmitted spectrum for various combinations of parameters. Here is a basic example of the cpfksmod and cpfskdem objects.

http://liquidsdr.org/doc/cpfskmodem/

Frequency-shift keying (fsk) modem... Listed below is the full interface to... Here is a basic example of...

http://liquidsdr.org/doc/fskmodem/