5.6.10 Comparison of modulations 1)Efficiency,Rb 2)Reliability,Pb In the physical channel,Electrical waveforms,such as pulses and carriers, are used to transmit info in the physic media. {,an} 人，an,} s.() r(t)= Recv W s (t)+n(t) Specifically, Baseband(BB):pulses of diff amps(PAM),or orthogonal pulses(PPM); 。 Passband(PB):Carriers with amp/phs/freq mod.(ASK/PSK/FSK),QAM The essential physical features of the waveform is the 1)The BW:denoted by W; 2)The energy:denoted by Es (if unequal,Eav),or Eb=Es/k; UESTC-Digital transmission through the AWGN channel Prof李晓峰 5