On transmitter side, information bits are mapped to symbols/waveforms (e.g. k bits mapped to M symbols), where M=2^k
Thus,
k=1 M=2^1=2
k=2 M=2^2=4
k=3 M=2^3=8
k=4 M=2^4=16
Information can be embedded in AMPLITUDE, PHASE, FREQUENCY, TIME-SLOT/PULSE POSITIONS or their combination
Memoryless modulation techniques:
PAM (Pulse Amplitude Modulation) : M-PAM means M possible amplitudes corresponding to M=2^k possible k-bit blocks of symbols
Signal Space diagram for digital PAM signals
PSK (Phase Shift Keying)
Signal Space diagram for digital PAM signals
QAM (Quadrature Amplitude Modulation) : Simultaneously impressing two separate k-bit symbols from the information sequence on two quadrature carrier (cosine and sine). This is also called as quadrature PAM.
Combined PAM-PSK signal space diagram(two constellations on left)
Rectangular QAM signal space diagram (one constellation on right)
Thus,k=1 M=2^1=2
k=2 M=2^2=4
k=3 M=2^3=8
k=4 M=2^4=16
Information can be embedded in AMPLITUDE, PHASE, FREQUENCY, TIME-SLOT/PULSE POSITIONS or their combination
Memoryless modulation techniques:
PAM (Pulse Amplitude Modulation) : M-PAM means M possible amplitudes corresponding to M=2^k possible k-bit blocks of symbols
Signal Space diagram for digital PAM signals
PSK (Phase Shift Keying)
Signal Space diagram for digital PAM signals
QAM (Quadrature Amplitude Modulation) : Simultaneously impressing two separate k-bit symbols from the information sequence on two quadrature carrier (cosine and sine). This is also called as quadrature PAM.
Combined PAM-PSK signal space diagram(two constellations on left)
Rectangular QAM signal space diagram (one constellation on right)
