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Lecture 6: Signal encoding techniques

Lecture 6: Signal encoding techniques. Anders Västberg vastberg@kth.se 08-790 44 55. Digital Communication System. Source of Information. Source Encoder. Channel Encoder. Digital Modulator. Modulator. RF-Stage. Channel. Information Sink. Source Decoder. Demodulator.

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Lecture 6: Signal encoding techniques

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  1. Lecture 6: Signal encodingtechniques Anders Västberg vastberg@kth.se 08-790 44 55

  2. Digital Communication System Source of Information Source Encoder Channel Encoder Digital Modulator Modulator RF-Stage Channel Information Sink Source Decoder Demodulator RF-Stage Channel Decoder Digital Demodulator [Slimane]

  3. Analog and Digital Signals

  4. Digital/Analog signal [Stallings, 2005]

  5. Signal Encoding • Digital to analog • Digital data to an analog channel (radio) • Analog to analog • Baseband analog signal to a radio channel • Analog to digital • Digitize an analog signal

  6. Concepts • Data rate (bit/s) • Modulation rate (baud  symbols/s) • Bit Error Rate (BER) • All otherthingconstant: • Increased data rate => increase BER • Increase in SNR => decrease BER • IncreaseBandwidth => increase Data rate

  7. Digital to Analog Encoding • Digital to Analog Encoding • Digital ModulationASK, FSK, PSK, QPSK • Analog to Analog • Analog ModulationAM, FM • Analog to Digital • Sampling and encoding

  8. Modulation of Analog Signals for Digital Data [Stallings, 2005]

  9. Full Duplex FSK [Stallings, 2005]

  10. MFSK Frequency use [Stallings, 2005]

  11. DPSK [Stallings, 2005]

  12. QPSK [Stallings, 2005]

  13. Performance: Bandwidth • ASK • MPSK • MFSK • Bandwidth efficiency Digital to analog

  14. BER for different modulation methods [Stallings, 2005]

  15. Other modulation methods • Minimum shift keying • Continuous phase • Better bandwidth efficiency than BFSK • Almost the same BER • QAM [Stallings, 2005]

  16. QAM [Stallings, 2005]

  17. Analog Data/Analog Signals [Stallings, 2005]

  18. Digitizing Analog Data [Stallings, 2005]

  19. Sampled Signals and Spectrum Nyquist’s Sampling Theorem statesi.e. the sampling frequency must be at least twice the bandwidth of the signal

  20. Pulse Code Modulation [Stallings, 2005]

  21. Quantization [Stallings, 2005]

  22. Delta modulation [Stallings, 2005]

  23. Homework before F7 • I en brusfri kanal med bandbredden 200 kHz vill man ha en kanalkapacitet på 800 kbit/s. Hur många signaleringsnivåer måste man minst ha? • Vad är maximal överföringskapacitet på en kanal med bandbredden 200 kHz och ett signal-brus förhållande på 20 dB?

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