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UCBPHYSICAL LAYER
Jean WalrandU.C. Berkeley
www.eecs.berkeley.edu/~wlr
UCB Overview
Digital Link Optical Copper Wireless
UCB Digital Link
Structure:
UCB Digital Link (continued)
Examples
UCB Digital Link (continued)
Frequency and Propagation:
UCB Digital Link (continued)
Limitations:
UCB Digital Link (continued)
Baseband: Not self-clocking
UCB Digital Link (continued)
Baseband: Self-Clocking
UCB Digital Link (continued)
Optical: Self-Clocking
4B/5B or 8B/10B
Basic Idea:
Introduce enough transitions so that the signal contains the clock.
UCB Digital Link (continued)
Broadband: PSK and BPSK
UCB Digital Link (continued)
Spectrum of BPSK (150 bps, carrier 600 Hz) => 150Hz
Other modulation schemes: 2 to 7 bps per HzNote: Shannon Capacity is W log2(1 + S/N)
UCB Optical Link Components:
UCB Optical Link (continued)
Fibers:
UCB Optical Link (continued)
Attenuation
UCB
Key Ideas: • Synchronize Transmitters for easy ADM• Enable slipping between PATH and Line
Optical Link (continued)
SONET
UCB Optical Link (continued)
SONET Frame
UCB Copper Link Common Modulation: QPSK
UCB Copper Link (continued)
ADSL
DMT: • Divides bw into channels of 4kHz• Uses QAM in each channel, based on SNR