Signal Encoding

Signal encoding is used to increase system robustness against noise

Examples:

FDDI uses 4b/5b NRZI (Non-Return to Zero Invert on ones) with 125 Mb/s baud rate to achieve 100 Mb/s data rate

Ethernet uses Manchester encoding with 20 Mb/s baud rate (20 MBd) to achieve 10 Mb/s data rate

time axis

Clock

NRZ - used by PC bus

Binary 1 = high

Binary 0 = low

NRZI - used in combination with

4b/5b by FDDI

Binary 1 = transition

Binary 0 = no transition

Manchester - used by Ethernet

Binary 1 = high-low transition

Binary 0 = low-high transition

High

Low

0

0

1

0

0

1

1

0

0

1

1

1

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