MFSK vs FSK Why BER decreases increasing the symbols

1. What is the difference between FSK and MFSK?
2. What is the maximum allowable bit rate in kbps if noncoherent FSK is used?
3. Is the FSK spectrum a combination of two ask spectra centered around two frequencies?

What is the difference between FSK and MFSK?

Multiple frequency-shift keying (MFSK) is a variation of frequency-shift keying (FSK) that uses more than two frequencies.

What is the maximum allowable bit rate in kbps if noncoherent FSK is used?

If noncoherent FSK is used, then the maximum allowable bit rate is: 8.5 kbps.

Is the FSK spectrum a combination of two ask spectra centered around two frequencies?

The FSK spectrum is the consolidation of two ASK spectra centred around The bandwidth needed for FSK transmission is similar to the band rate of the signal plus the frequency change (the difference between the two carrier frequencies) − BW=(fc1−fc0)+Nband .