Gaussian Minimum Shift Keying (GMSK)

Fundamentals
Title	Gaussian Minimum Shift Keying (GMSK)
Author(s)	J.A Ávila Rodríguez, University FAF Munich, Germany.
Level	Advanced
Year of Publication	2011

The Gaussian Minimum Shift Keying (GMSK) modulation is a modified version of the Minimum Shift Keying (MSK) modulation where the phase is further filtered through a Gaussian filter to smooth the transitions from one point to the next in the constellation. Next figure presents the GMSK generation scheme:

Figure 1: GMSK generation scheme.

where the Gaussian filter adopts the following form in the time domain:

Where [math]\displaystyle{ \lambda }[/math] is a normalization constant to maintain the power and the product [math]\displaystyle{ B T_c }[/math] is the -3 dB bandwidth-symbol time product. The higher this value, the cleaner will be the eye diagram of the signal but more power will be transmitted on the side lobes of the spectrum. A typical value in communication applications is [math]\displaystyle{ B T_c = 0.3 }[/math] which is a good compromise between spectral efficiency and Inter-Symbol interference

Credits

The information presented in this NAVIPEDIA’s article is an extract of the PhD work performed by Dr. Jose Ángel Ávila Rodríguez in the FAF University of Munich as part of his Doctoral Thesis “On Generalized Signal Waveforms for Satellite Navigation” presented in June 2008, Munich (Germany)