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