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Digital Communications 0909.402.03/0909.504.01 Fall 2002

Digital Communications 0909.402.03/0909.504.01 Fall 2002. Lecture 8 October 28, 2002. Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/fall02/digcomm/. Plan. Bandpass Data Transmission Recall: QPSK p /4 QPSK or 4-QAM Basic QAM Structure M-QAM

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Digital Communications 0909.402.03/0909.504.01 Fall 2002

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  1. Digital Communications0909.402.03/0909.504.01Fall 2002 Lecture 8October 28, 2002 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/fall02/digcomm/

  2. Plan • Bandpass Data Transmission • Recall: QPSK • p/4 QPSK or 4-QAM • Basic QAM Structure • M-QAM • QAM Simulation • BER for QAM and QPSK

  3. Digital Communications Transceiver Anti- aliasing Filter Error Control Encoder Data Encryption Encoder Channel/ Line Encoder Source Encoder Sampling Quantization Modulator MUX ADC Analog i/p CODEC MODEM Multiple access channel Analog o/p Error Control Decoder Data Encryption Decoder Source Decoder Audio Amp Reconstruction/ DAC Equalization / Decision Circuits Demod-ulator DEMUX

  4. Q f I Quadrature Phase Shift Keying(QPSK) IQ Diagram

  5. M-ary Phase Shift Keying(M-PSK) Q I Octophase I-Q Constellation

  6. p/4 QPSK or 4-QAM IQ Diagram s(t) = Ac cos(2pfct + f(t)) Q 3p/4 01 11 10 f(t) p/4 00 p/4 t I 10 -p/4 11 01 00 -3p/4

  7. Transmitting Filter Transmitting Filter Balanced Modulator Balanced Modulator Basic QAM Structure Oscillator fc QAM Signal S Binary Data Serial- Parallel -p/2 Phase Shift Matlab script: qpsk.m

  8. M-QAM Q I 16-QAM I-Q Constellation

  9. Symbol Error in M-ary PSK Systems Matlab script: dignoise.m

  10. Symbol Error in M-ary QAM Systems Matlab script: dignoise.m

  11. Summary

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