What is GMSK?

GMSK stands for Gaussian Minimum Shift Keying and it refers to a modulation scheme commonly used in radio communications and the GSM technology used by mobile phones. GMSK works similarly to MSK or the generic minimum-shift keying but the main difference is on the Gaussian filter setup from which the digital data stream passes through before it is taken to the frequency modulator. Because of this additional filtering of digital data, sideband power will be greatly reduced and interferences will also be minimized especially those involving signals coming from adjacent or nearby channels.

Interferences are common when using standard MSK modulation schemes. Under these standard phase shift keying, sidebands will tend to over-extend in an outward direction and away from the main carrier. This scenario will then result to more interference especially if signals from nearby channels are present. With the addition of the Gaussian filter setup, the whole spectrum will be efficiently used along with the modulation of the digital signal.

As for the GSM technology in cellular phones and mobile devices, GMSK’s continuous phase shift keying capabilities is widely used for less interference and better use of the whole spectrum. GMSK also produces less noise when compared with other phase shift-keying modulation schemes. This feature helps to produce better signal quality which is essential in mobile phone communications. Another great advantage of GMSK modulation is its ability to be amplified even by amplifiers with non-linear specifications. This means that GMSK will not be distorted resulting to better digital data modulation efficiency. The mobile phone industry widely uses portable transmitters and it benefits from GMSK’s basic features on noise reduction and immunity to variations in amplitude. And since GMSK amplification is through non linear amplifiers, less power is consumed for a given output. And again, this benefits the cellular phone industry in terms of battery consumption levels.