Gaussian Frequency Shift Keying (GFSK) is a modified frequencyshift keying(FSK) technique that uses a Gaussianfilter.
In this modulation method, the narrowband filtering reduces the proportion of harmonics and reduces crosstalk. The GSFK method is used in the GSM standard, Bluetooth, Bluetooth Low Energy( BLE) and ANT+.
GFSK keying is available with two or four levels as 2GFSK or 4GFSK. In these versions, it is used in frequency hopping in 802.11.