10/11/40 page 1 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Data Encoding

10/11/40 page 2 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Encoding scheme voice Telephone analog digital Modem analog CODEC digital Digital transmitter digital Analog data, Analog signal Digital data, Analog signal Digital data, Digital signal Analog data, Digital signal

10/11/40 page 3 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Encoding and Modulation EncoderDecoder Modulator Demodulator digitaloranalog digitaloranalog digital analog g(t) m(t) fcfcfcfc s(f) x(t) t f fc g(t) m(t) x(t) s(t)

10/11/40 page 4 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Why encoding? Three factors determine successfulness of receiving signal S/N data rate bandwidth More factor can be used to improve encoding scheme

10/11/40 page 5 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Encoding evaluation factors Signal spectrum Clocking Error detection Signal interference& noise immunity Cost and complexity

10/11/40 page 6 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Digital data, Digital signal NRZ NRZI Bipolar -AMI Pseudoternary Manchester DifferentialManchester

10/11/40 page 7 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Scrambling techniques VB0VB VB00VB00V Bit value B8ZS Bipolar-AMI HDB3

10/11/40 page 8 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Spectral density NRZ- L, NRZI B8ZS,HDB3 AMI, Pseudoternary Manchester, Differential Manchester Mean square voltage per unit bandwidth Normalized frequency (f/r)

10/11/40 page 9 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Digital data, Analog signal Tranmitting digital data through PSTN Modem is used to convert digital data to analog signal and vice versa

10/11/40 page 10 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Modultion techniques ASK FSK PSK

10/11/40 page 11 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL ASK V d (t) V c (t) V ASK (t) fcfcfcfc f c -f 0 f c -3f 0 f c +f 0 f c +3f 0 Signalpower Frequency frequency spectrum

10/11/40 page 12 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL FSK Carrier 2 Datasignal Carrier 1 v d (t) v 1 (t) v 2 (t) v FSK (t) f1f1f1f1 Signalpower Frequency frequency spectrum f2f2f2f2

10/11/40 page 13 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL FSK in modem (1070) 1850 (2225) 1180 (1270) 1650 (2025) 3400 Amplitude Frequency(Hz) PSTN bandwidth frequency spectrum

10/11/40 page 14 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL PSK DataSignal Carrier Phasecoherent Differential v c (t) v PSK (t) 180=00=1 phase diagram bit rate = signaling rate

10/11/40 page 15 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Multilevel modulation method bit rate = n x signaling rate

10/11/40 page 16 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Multilevel modulation method +90?01 0? ? ?11 4-PSK phase diagram 16-QAM phase diagram 1

10/11/40 page 17 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Analog data, Digital signal Two principle techniques used PCM DM Analog voice signal Sampling clock PAM signal PCM signal Sampling Circuit Sampling Circuit Quantizer and compander Quantizer and compander Digitized voice signal

10/11/40 page 18 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL PCM Sampling signal based on nyquist theorem Original signal Original signal PAM pulse PAM pulse PCM pulse PCM pulse with quantized error with quantized error PCM output PCM output

10/11/40 page 19 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL PCM Conversion process B A C D A B C D Analog voice signal Sampling clock PAM signal PCM signal Sampling Circuit Sampling Circuit Quantizer and compander Quantizer and compander Digitized voice signal

10/11/40 page 20 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Nonlinear encoding Strong signal Weak signal Quantizing level Without nonlinear encoding With nonlinear encoding

10/11/40 page 21 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Companding process Implement nonlinear encoding via companding process Companding = Compressing Expanding linear quantization interval segmentcodes(+) segmentcodes(-) Network Compressor circuit Compressor circuit Linear ADC Linear ADC Linear DAC Linear DAC Expander circuit Expander circuit vivi vivi vovo vovo

10/11/40 page 22 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Analog Data, Analog signal Use Modultion techniques Need a high frequency for effective tranmission Modulation permits frequency division multiplex

10/11/40 page 23 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Analog Modulation Carrier Modulating sine-wave signal Amplitude-modulated wave Frequency-modulated wave Phase-modulated wave

10/11/40 page 24 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL AM Spectrum carrier lower sideband upper sideband each sideband contains the complete spectrum of s(t) ! M(f) f 0 f c - B Discrete carrier term Lower sideband Upper sideband f c + B fcfcfcfc

10/11/40 page 25 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL AM power saving SSB (Single ideband) DSBSC (Double sideband supresses carrier) VSB (Vestigial sideband)

10/11/40 page 26 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL FM and PM Carrier Modulating sine-wave signal Amplitude-modulated (DSBTC) wave Frequency-modulated wave Phase-modulated wave