Feb. 2, 2004 Prof. Paul Lin 1 CPET The Physical Layer - Signal Encoding & Modems Paul I-Hai Lin, Professor Electrical and Computer Engineering Technology Purdue University, Fort Wayne Campus

Feb. 2, 2004 Prof. Paul Lin 2 Baseband Transmission What is a baseband? What is a baseband? “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

Feb. 2, 2004 Prof. Paul Lin 3 Broadband Transmission What is a Broadband? What is a Broadband? “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

Feb. 2, 2004 Prof. Paul Lin 4 Signal Modulation Usable spectrum: Radio wave, Microwave, Infrared, and Visible light Usable spectrum: Radio wave, Microwave, Infrared, and Visible light Analog Modulating Methods: Analog Modulating Methods: Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM)Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM) Digital Modulation Methods: 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), etcFrequency Shift Keying (switching), Phase Shift Keying, QPSk (Quadrature Phase Shift Keying), QAM (Quadrature Amplitude Modulation - a combination of AM and PM), etc

Feb. 2, 2004 Prof. Paul Lin 5 Modems and Digital Modulation ASK (Amplitude Shift Keying) ASK (Amplitude Shift Keying) FSK (Frequency Shift Keying) – low speed 300 bps FSK (Frequency Shift Keying) – low speed 300 bps PSK (Phase Shift Keying) PSK (Phase Shift Keying) QPSk (Quadrature Phase Shift Keying) QPSk (Quadrature Phase Shift Keying) QAM (Quadrature Amplitude Modulation - a combination of AM and PM) QAM (Quadrature Amplitude Modulation - a combination of AM and PM)

Feb. 2, 2004 Prof. Paul Lin 6 Baseband Digital Encoding Digital Modulation Methods: Digital Modulation Methods: RS-232 encodingRS-232 encoding 1 (-3 to -25 volts) 1 (-3 to -25 volts) 0 (+3 to +25 volts) 0 (+3 to +25 volts) Unipolar Modulation (NRZ, non-return to zero)Unipolar Modulation (NRZ, non-return to zero) 1 -> A volts, T = 1/R; R = bit rate; 0 -> 0 volts 1 -> A volts, T = 1/R; R = bit rate; 0 -> 0 volts Polar Modulation(NRZ)Polar Modulation(NRZ) 1 -> A volts; 0 -> -A volts 1 -> A volts; 0 -> -A volts Inverted –NRZ (differential encoding)Inverted –NRZ (differential encoding) Bipolar EncodingBipolar Encoding Manchester EncodingManchester Encoding Differential Manchester EncodingDifferential Manchester Encoding

Feb. 2, 2004 Prof. Paul Lin 7 Modulation/Demodulation Modem Digital Modulation Methods: Digital Modulation Methods: Unipolar Modulation (NRZ, non-return to zero)Unipolar Modulation (NRZ, non-return to zero) 1 -> A volts, T = 1/R; R = bit rate 1 -> A volts, T = 1/R; R = bit rate 0 -> 0 volts 0 -> 0 volts Polar Modulation(NRZ)Polar Modulation(NRZ) 1 -> A volts 1 -> A volts 0 -> -A volts 0 -> -A volts Frequency Shift Keying (switching)Frequency Shift Keying (switching) Phase Shift KeyingPhase Shift Keying QPSk (Quadrature Phase Shift Keying)QPSk (Quadrature Phase Shift Keying) QAM (Quadrature Amplitude Modulation - a combination of AM and PM)QAM (Quadrature Amplitude Modulation - a combination of AM and PM)

Feb. 2, 2004 Prof. Paul Lin 8 Telephone Modems Standards Max Bandwidth 3400 Hz, max SNR 40 dB Max Bandwidth 3400 Hz, max SNR 40 dB Bit rate Bit rate 2400, 4800, 9600, 192,00, 28,800, 31,200, and 33,600 bps2400, 4800, 9600, 192,00, 28,800, 31,200, and 33,600 bps

Feb. 2, 2004 Prof. Paul Lin 9 ADSL (Asynchronous Digital Subscriber Line) Lowest 4 kHz for voice lines Lowest 4 kHz for voice lines Uses Discrete Multi-Tone Modulation (DMT) Uses Discrete Multi-Tone Modulation (DMT) Upstream speed < Downstream speed Upstream speed < Downstream speed Fast business users Mbps/512kbps Fast business users Mbps/512kbps Residential users – 512/64 Kbps Residential users – 512/64 Kbps UTP wires – support up to 1.1 MHzUTP wires – support up to 1.1 MHz Upstream 30 kHz to *Upstream 30 kHz to * Downstream * to 1.1 MHzDownstream * to 1.1 MHz Info: adsl.htm adsl.htm adsl.htm

Feb. 2, 2004 Prof. Paul Lin 10 Hybrid Fiber-Coaxial Systems Upstream Fiber Upstream Fiber Downstream Fiber Downstream Fiber Fiber Nodes Fiber Nodes Coaxial Distribution Coaxial Distribution

Feb. 2, 2004 Prof. Paul Lin 11 Cable TV Bandwidth Allocation Pay-per-view Bands Pay-per-view Bands 5 MHz to 42 MHz5 MHz to 42 MHz Analog TV Bands Analog TV Bands 54 MHz to 500 MHz54 MHz to 500 MHz Digital video and digital signals Digital video and digital signals 550 MHz to 750 MHz550 MHz to 750 MHz

Feb. 2, 2004 Prof. Paul Lin 12 CATV Digital Networks Upstream Upstream 5 MHz to 42 MHz5 MHz to 42 MHz Downstream Downstream 54 MHz to 500 MHz54 MHz to 500 MHz Proposed downstream Proposed downstream 550 to 750 MHz550 to 750 MHz

Feb. 2, 2004 Prof. Paul Lin 13 CATV Digital Networks Upstream Upstream 5 MHz to 42 MHz5 MHz to 42 MHz Downstream Downstream 54 MHz to 500 MHz54 MHz to 500 MHz Proposed downstream Proposed downstream 550 to 750 MHz550 to 750 MHz