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CPET 355

CPET 355. 2. The Physical Layer - Signal Encoding & Modems Paul I-Hai Lin, Professor Electrical and Computer Engineering Technology Purdue University, Fort Wayne Campus. Baseband Transmission. What is a baseband? www.rvcomp.com/wiring/EIA/glossary.htm

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CPET 355

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  1. CPET 355 2. The Physical Layer - Signal Encoding & Modems Paul I-Hai Lin, Professor Electrical and Computer Engineering Technology Purdue University, Fort Wayne Campus Prof. Paul Lin

  2. Baseband Transmission • What is a baseband? www.rvcomp.com/wiring/EIA/glossary.htm “A transmission method in which the entire bandwidth of the transmission medium is used to transmit a single digital signal. The signal is ascribed directly onto the transmission medium without modulation of any kind. Simultaneous transmissions can be achieved through time division multiplexing. Baseband is simpler, cheaper and less sophisticated than Broadband.” Examples: 10BaseT, 100BaseT Prof. Paul Lin

  3. Broadband Transmission • What is a Broadband? www.rvcomp.com/wiring/EIA/glossary.htm “A transmission facility having a bandwidth sufficient to carry multiple voice, video or data channels simultaneously. Each channel occupies (is modulated to) a different frequency bandwidth on the transmission medium and is demodulated to its original frequency at the receiving end. Channels are separated by ìguardbandsî (empty spaces) to ensure that each channel wonít interfere with its neighboring channels. This technique is used to provide 50 CATV channels on one coaxial cable.” High-bandwidth Internet connection Prof. Paul Lin

  4. Signal Modulation • Usable spectrum: Radio wave, Microwave, Infrared, and Visible light • Analog Modulating Methods: • Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM) • Digital Modulation Methods: • Frequency Shift Keying (switching), Phase Shift Keying, QPSk (Quadrature Phase Shift Keying), QAM (Quadrature Amplitude Modulation - a combination of AM and PM), etc Prof. Paul Lin

  5. Modems and Digital Modulation • ASK (Amplitude Shift Keying) • FSK (Frequency Shift Keying) – low speed 300 bps • PSK (Phase Shift Keying) • QPSk (Quadrature Phase Shift Keying) • QAM (Quadrature Amplitude Modulation - a combination of AM and PM) Prof. Paul Lin

  6. Baseband Digital Encoding • Digital Modulation Methods: • RS-232 encoding • 1 (-3 to -25 volts) • 0 (+3 to +25 volts) • Unipolar Modulation (NRZ, non-return to zero) • 1 -> A volts, T = 1/R; R = bit rate; 0 -> 0 volts • Polar Modulation(NRZ) • 1 -> A volts; 0 -> -A volts • Inverted –NRZ (differential encoding) • Bipolar Encoding • Manchester Encoding • Differential Manchester Encoding Prof. Paul Lin

  7. Modulation/Demodulation Modem • Digital Modulation Methods: • Unipolar Modulation (NRZ, non-return to zero) • 1 -> A volts, T = 1/R; R = bit rate • 0 -> 0 volts • Polar Modulation(NRZ) • 1 -> A volts • 0 -> -A volts • Frequency Shift Keying (switching) • Phase Shift Keying • QPSk (Quadrature Phase Shift Keying) • QAM (Quadrature Amplitude Modulation - a combination of AM and PM) Prof. Paul Lin

  8. Telephone Modems Standards • Max Bandwidth 3400 Hz, max SNR 40 dB • Bit rate • 2400, 4800, 9600, 192,00, 28,800, 31,200, and 33,600 bps Prof. Paul Lin

  9. ADSL (Asynchronous Digital Subscriber Line) • Lowest 4 kHz for voice lines • Uses Discrete Multi-Tone Modulation (DMT) • Upstream speed < Downstream speed • Fast business users - 1.5 Mbps/512kbps • Residential users – 512/64 Kbps • UTP wires – support up to 1.1 MHz • Upstream 30 kHz to * • Downstream * to 1.1 MHz Info: http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/adsl.htm Prof. Paul Lin

  10. Hybrid Fiber-Coaxial Systems • Upstream Fiber • Downstream Fiber • Fiber Nodes • Coaxial Distribution Prof. Paul Lin

  11. Cable TV Bandwidth Allocation • Pay-per-view Bands • 5 MHz to 42 MHz • Analog TV Bands • 54 MHz to 500 MHz • Digital video and digital signals • 550 MHz to 750 MHz Prof. Paul Lin

  12. CATV Digital Networks • Upstream • 5 MHz to 42 MHz • Downstream • 54 MHz to 500 MHz • Proposed downstream • 550 to 750 MHz Prof. Paul Lin

  13. CATV Digital Networks • Upstream • 5 MHz to 42 MHz • Downstream • 54 MHz to 500 MHz • Proposed downstream • 550 to 750 MHz Prof. Paul Lin

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