Gmsk modulation and demodulation

1. What is GMSK demodulation?
2. How does GMSK modulation work?
3. Where is GMSK modulation used?
4. Why is GMSK modulation preferred in GSM?

What is GMSK demodulation?

The GMSK Demodulator Baseband block uses a Viterbi algorithm to demodulate a signal that was modulated using the Gaussian minimum shift keying method. The input to this block is a baseband representation of the modulated signal.

How does GMSK modulation work?

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.

Where is GMSK modulation used?

GMSK – Gaussian minimum shift keying – is the original circuit switched GSM modulation system, allowing the GSM radio channel to be modulated at a data rate of 271kb/s whilst keeping the radio channel within a 200kHz bandwidth. This is the modulation system used for circuit switched and GPRS operations.

Why is GMSK modulation preferred in GSM?

GMSK is a special case of MSK modulation. The phase of the transmitted signal in GMSK scheme is continuous and smoothed by a Gaussian filter. This results in more compact spectrum than MSK and enables better utilization of the available frequency spectrum, at the expense of increased inter-symbol interference (ISI).