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					Digital Signaling
                  Digital
• Early Systems
  – Morse code, telex
• Digital Signal Processing
  – Compatibility with computers
  – Coding and post processing
• Nature
  – Increased bandwidth demand
  – Less susceptible to noise
  – Compatible with multiple sources
           Pulse Code Modulation
• Pulse Amplitude Modulation
   – Periodic pulses of fixed duration
   – Amplitude coded
   – Waveform
       • http://cnyack.homestead.com/files/modulation/modpam.htm
• Pulse Width Modulation
   – Periodic pulses of constant amplitude
   – Pulse width coded
   – Waveform
       • http://cnyack.homestead.com/files/modulation/modpwm.htm
• Pulse Position Modulation
   – Pulse timing coded
   – Waveform
       • http://cnyack.homestead.com/files/modulation/modppm.htm
                  PAM Circuits
• Modulation




• Detection
  – Peak detection, AM


  – http://www.tpub.com/content/neets/14184/css/14184_175.htm
 Analog and Digital Conversion
• A/D
  – Sampling
    • Rate
    • Aliasing
    • Nyquist
  – Quantization
    • Step size or error
  – Binary encoding
  – Line coding
• D/A
Sampling
Aliasing and DSP
Nyquist Rate
                 Quantization
• Resolution
• Error (Noise)
  – (Vmax - Vmin) / 2B
• S/N




  – http://cnx.rice.edu/content/m0051/latest/
  – http://www.analog.com/en/content/0,2886,761%255F795%255F88
    014,00.html
            Companding
• Finer Step for Small Signal

  – -law
            A/D Circuit
• Ramp
• Successive Approximation
• Flash
         Delta Modulation
• Transmit the Difference
• Single Bit A/D
• Over Sampling
Delta Modulation
        Sigma Delta Modulation
• Delta
   – Difference
• Sigma
   – Sum of previous difference




• http://www.numerix-dsp.com/appsnotes/APR8-sigma-delta.pdf
• http://www.mwrf.com/Articles/Print.cfm?ArticleID=10586
           D/A Circuit
• R-2R




• Weighted Sum
                     CODEC
• Audio CODEC
  – Phone
     • http://products.zarlink.com/product_profiles/MT9160B.htm
  – AC’97
     • Sound card and soft modem
  – CD player
• Video CODEC
  – http://www.lsi.com/consumer_home/products_home/broadcas
    t_infrastructure/video_broadcasting_solutions/index.html
  – MPEG
         Digital Modulation
• Amplitude Shift Keying
  – Binary
        Digital Modulation
• Frequency Shift Keying
             Simple FSK Circuit




          http://www.edn.com/contents/images/101101di.pdf

• Transceivers
   – http://jap.hu/electronic/rf.html
         Digital Modulation
• Phase Shift Keying
  – Binary




  – Quadrature
  – M-ary
         Multi-Level Modulation
•   Symbol and Data Rate
•   Amplitude
•   Frequency
•   Phase
    – QPSK
• Combination
    – QAM
    – M-ary
    – From modem to fiber optics
       • http://www.hitachi.com/New/cnews/041008_041008.pdf
                                 QPSK
• Constellation
• Modulation




       A D A B A A D C C A


• Detection
• Resources
   – Mini Circuits
       • http://www.minicircuits.com/p
         ages/app_notes.html
   – Intel
       • http://www.intel.com/netcom
         ms/technologies/wimax/3037
         88.pdf
• 8-PSK, 16-PSK
                                         QAM
                                         16 QAM Constellation

• Constellations                                 1




         64 QAM Constellation
                 1


                                    -1                          1




 -1                             1               -1




                                                                    256 Point Constellation

                                                                            1

                -1




• Euclidean Distance
• Constellation Display                                                     0
                                                           -1                    0            1


      – http://www.lecroy.com/tm/librar
        y/LABs/PDF/LAB303B.pdf

                                                                            -1
                           QAM
• 16-QAM Signaling
   – http://www.inue.uni-
     stuttgart.de/german/lehre/lesungen/uet2/applet/QAM16e.html
   – http://www.educatorscorner.com/index.cgi?CONTENT_ID=2478
• Matlab
   – http://www.mathworks.com/access/helpdesk/help/toolbox/comm/u
     g/a1067963807.html
   – Waveform
   – Spectrum
   – Noise
   – S/N
   – Eye diagram
   – Bit error rate
• Signal Generation by Hardware
   – Phase, amplitude combinations
   – TI DSP kit
     More Digital Modulation
• Offset QPSK
• Minimum SK
• Gaussian Minimum SK

• http://www.emc.york.ac.uk/reports/linkpcp/appD.pdf
• http://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-
  Computer-Science/6-976High-Speed-Communication-Circuits-
  and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-
  78BD8CBEF42E/0/proj2.pdf
• http://www.ictp.trieste.it/~radionet/2001_school/lectures/fitton/di
  gital_mod.pdf
• http://www.plextek.com/papers/schmsv6.pdf
    Generic Digital Modulators
• ASK
  – AM
• FSK
  – VCO
  – V1 and V2
• BPSK
  – Mixer
  – -V and +V
• M-ary
  – DSP

                   Source: Tomasi – Electronic Comm
                    Detection
• Coherent Detection
  – Local oscillator
  – Synchronization
     • RF carrier
  – Mixer, LPF; PLL
• Incoherent Detection
  – No local oscillator
  – Envelope detector; Discriminator
  – Differential PSK
• Comparison
  – Receiver Circuits
  – S/N
• Timing
        Coherent Detection
• ASK
• FSK
• PSK




                 Source: Tomasi – Electronic Comm
         Coherent Detection
• Carrier Recovery
  – No carrier pilot
  – Square loop
  – Costas loop
  – Remodulator
  – Reference
     • http://www.mwrf.co
       m/Articles/Print.cfm
       ?Ad=1&ArticleID=93
       66
        Incoherent Detection
• ASK
• FSK
                           DPSK
• Differential PSK
  – Simplicity
  – Transmitter
  – Receiver




• Application in Optical Communications
  – www.leuthold.info/papers/0308_DPSK_IntegratedBalancedRx.pdf
                   Timing
• Clock Recovery




• Reference
  – http://www.omnisterra.com/walker/pdfs.talks/ISSC
    C2002.pdf
        System Performance
• Eye Diagram
 – Superposition of sampled pulses




• Eye Opening
 – Contrast between “0” and “1”
 – http://www.complextoreal.com/chapters/eye.pdf
Noise Analysis in Digital Systems
• Noise Model
  – Additive White Gaussian Noise
• Probability of Error
• S/N
 Noise Analysis in Digital Systems
• Bit Error Rate
  – Function of S/N
  – Introduction
     • http://www.highfrequencyelectr
       onics.com/Archives/Jan03/HFE
       0103_Tutorial.pdf
  – Examples
     • http://www.ant.uni-
       bremen.de/whomes/rinas/dfsim/
       linearmodreference.html
  – Residual BER
     • http://www.home.agilent.com/u
       pload/cmc_upload/All/06-26-02-
       PredictingResidualBER-II-
       Johnson_657-NOTES.pdf
    Performance Comparison
• Hierarchy
  – Transmitter
    • PSK
    • FSK
    • ASK
  – Receiver
    • Coherent
    • Non-coherent
      Trellis-Coded Modulation
• Gottfried Ungerboeck
   – IBM Zurich
   – 1997 Australia Prize
   – Convolution coding
       • http://pweb.netcom.com/~chip.f/Viterbi.html
• Andrew J. Viterbi
   – Co-founder of Qualcom
       • http://www.ieee.org/organizations/history_center/comsoc/viterb
         i.html
   – Viterbi Algorithm
       • Maximum likelihood detection
       • Demo using Java Applet
           – http://lcmwww.epfl.ch/APPLETS/VITERBI/Viterbi.html
• Application in Modem
• Reference
   – http://db.s2.chalmers.se/download/masters/master_EX043_
     2002.pdf
TCM Schemes
TCM Schemes Conti.
          TCM Schemes Conti.
• Error-event probability
  – Pr(e)=Nfree*Q[dfree/(2*N0)]
  – dfree_QPSK=sqrt(2), Nfree=2
  – dfree_8PSK=2, Nfree=1
    Applications of Digital Systems
•   Modem
•   xDSL
•   Ethernet, Cable Modem
•   Multimedia
    – HDTV, digital video, digital audio, digital radio
• Computer Peripherals
• Digital Telephone Services and Switching
  Systems
    – Repeater: regeneration, reshaping, retiming
                         Modem
• Standard
  – http://www.fujitsu-
    siemens.co.uk/rl/servicesupport/techsupport/Boards/Modem
    s/modemdiags/General-Info/Modem-Standards.htm
  – Modulation (v.34)
      •   FSK: Bell 103, 1070-1270 Hz, 2025-2225 Hz
      •   PSK, QPSK, D8-PSK: Bell 201-v.27
      •   QAM: v.29-v.32bis (FEC)
      •   Trellis: v.34
  – Error correction (v.42bis)
  – 56k (v.90, v.92)
      • ISP end: digital through phone switching
• Chips
  – Rockwell, Conexant, Agere, PCTel
  – AC’97 codec with modem riser
                                   ADSL
• Spectrum

• Modulation
   – Discrete multi-tone or FDM, x256
   – Framing, scrambling (EC)
• Details
   – http://www.cs.tut.fi/tlt/stuff/
     adsl/pt_adsl.html

• Chips
   – Broadcom, Agere, STMicro
• http://www.commsdesign.com/csdmag/sections/featu
  re_article/OEG20010221S0082
                 Chapter Review
• Digitization
   – Nyquist rate
   – Quantization error
   – Compander
• Modulation
   – ASK, FSK, PSK, QAM
• Detection
   – Coherent
   – Incoherent
      • DPSK
• Trellis Code Modulation
   – Convolution coding
   – State
• Modem
• ADSL