1. 10/11/40 page 1 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Data Encoding

2. 10/11/40 page 2 Department of Computer Engineering, Kasetsart University 204325 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

3. 10/11/40 page 3 Department of Computer Engineering, Kasetsart University 204325 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)

4. 10/11/40 page 4 Department of Computer Engineering, Kasetsart University 204325 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

5. 10/11/40 page 5 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Encoding evaluation factors Signal spectrum Clocking Error detection Signal interference& noise immunity Cost and complexity

6. 10/11/40 page 6 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Digital data, Digital signal 01001100011 NRZ NRZI Bipolar -AMI Pseudoternary Manchester DifferentialManchester

7. 10/11/40 page 7 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Scrambling techniques 1100000000110000010 000 000 VB0VB VB00VB00V Bit value B8ZS Bipolar-AMI HDB3

8. 10/11/40 page 8 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Spectral density -0.5 0 0.5 1 1.5 0 0.5 1 1.5 NRZ- L, NRZI B8ZS,HDB3 AMI, Pseudoternary Manchester, Differential Manchester Mean square voltage per unit bandwidth Normalized frequency (f/r)

9. 10/11/40 page 9 Department of Computer Engineering, Kasetsart University 204325 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. 10/11/40 page 10 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Modultion techniques 00110100010 ASK FSK PSK

11. 10/11/40 page 11 Department of Computer Engineering, Kasetsart University 204325 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

12. 10/11/40 page 12 Department of Computer Engineering, Kasetsart University 204325 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

13. 10/11/40 page 13 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL FSK in modem 400 980 (1070) 1850 (2225) 1180 (1270) 1650 (2025) 3400 Amplitude Frequency(Hz) PSTN bandwidth frequency spectrum

14. 10/11/40 page 14 Department of Computer Engineering, Kasetsart University 204325 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

15. 10/11/40 page 15 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Multilevel modulation method 01010101 10 00000000 0+90+180+270 11 bit rate = n x signaling rate

16. 10/11/40 page 16 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Multilevel modulation method +90?01 0?00 +270?11 +180?11 4-PSK phase diagram 16-QAM phase diagram 1

17. 10/11/40 page 17 Department of Computer Engineering, Kasetsart University 204325 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

18. 10/11/40 page 18 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL PCM Sampling signal based on nyquist theorem 3.2 3.9 2.8 3.4 1.2 4.2 3 4 3 3 1 4 011100011011001100 Original signal Original signal PAM pulse PAM pulse PCM pulse PCM pulse with quantized error with quantized error 011100011011001100 PCM output PCM output

19. 10/11/40 page 19 Department of Computer Engineering, Kasetsart University 204325 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

20. 10/11/40 page 20 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Nonlinear encoding 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Strong signal Weak signal 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Quantizing level Without nonlinear encoding With nonlinear encoding

21. 10/11/40 page 21 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Companding process Implement nonlinear encoding via companding process Companding = Compressing Expanding 11 10 01 00 11 10 01 00 11 10 01 00 11 10 01 00 11 10 01 00 11 10 01 00 11 10 01 00 11 10 01 00 linear quantization interval 1110 01 00 11 10 0100segmentcodes(+) segmentcodes(-) Network Compressor circuit Compressor circuit Linear ADC Linear ADC Linear DAC Linear DAC Expander circuit Expander circuit vivi vivi vovo vovo

22. 10/11/40 page 22 Department of Computer Engineering, Kasetsart University 204325 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

23. 10/11/40 page 23 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Analog Modulation Carrier Modulating sine-wave signal Amplitude-modulated wave Frequency-modulated wave Phase-modulated wave

24. 10/11/40 page 24 Department of Computer Engineering, Kasetsart University 204325 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

25. 10/11/40 page 25 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL AM power saving SSB (Single ideband) DSBSC (Double sideband supresses carrier) VSB (Vestigial sideband)

26. 10/11/40 page 26 Department of Computer Engineering, Kasetsart University 204325 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