22-05-2012, 05:17 PM
Gaussian Minimum Shift Keying GMSK
[attachment=22781]
GMSK
Gaussian Minimum Shift Keying
Modulation scheme used in GSM
Bandwidth-time product
Describes the amount the symbols overlap
BT = 0.3 for GSM networks
Good spectral efficiency
At the expense of some inter-symbol interference (ISI)
Data rate: 270.8 kbps
MSK
GMSK is based on MSK
Minimum Shift Keying
Linear phase changes
Spectrally efficient
At baseband, bit transitions are represented by ½ cycle sinusoid
Summing and Integration
The pulses are summed together (left)
The signal is integrated over time to obtain a continuous waveform which captures the bit transition information (right)
I&Q Signals
The resulting waveform is divided into In-Phase and Quadrature components
In-phase: Left
Quadrature: Right
The two signal components are then up-converted to the carrier frequency
[attachment=22781]
GMSK
Gaussian Minimum Shift Keying
Modulation scheme used in GSM
Bandwidth-time product
Describes the amount the symbols overlap
BT = 0.3 for GSM networks
Good spectral efficiency
At the expense of some inter-symbol interference (ISI)
Data rate: 270.8 kbps
MSK
GMSK is based on MSK
Minimum Shift Keying
Linear phase changes
Spectrally efficient
At baseband, bit transitions are represented by ½ cycle sinusoid
Summing and Integration
The pulses are summed together (left)
The signal is integrated over time to obtain a continuous waveform which captures the bit transition information (right)
I&Q Signals
The resulting waveform is divided into In-Phase and Quadrature components
In-phase: Left
Quadrature: Right
The two signal components are then up-converted to the carrier frequency