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Lecture 2

# Nyquist limit 1924 shannon capacity 1948 prac8cal

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Unformatted text preview: ter Science & Engineering Topic •  We’ve talked about signals represen8ng bits. How, exactly? –  This is the topic of modula8on Signal 10110… …10110 32 16 10/6/13 A Simple Modula8on •  Let a high voltage (+V) represent a 1, and low voltage (- V) represent a 0 –  This is called NRZ (Non- Return to Zero) Bits 0 0 1 0 1 1 1 1 0 1 0 0 0 0 1 0 +V NRZ - V 33 A Simple Modula8on (2) •  Let a high voltage (+V) represent a 1, and low voltage (- V) represent a 0 –  This is called NRZ (Non- Return to Zero) Bits 0 0 1 0 1 1 1 1 0 1 0 0 0 0 1 0 +V NRZ - V 34 17 10/6/13 Many Other Schemes •  Can use more signal levels, e.g., 4 levels is 2 bits per symbol •  Prac8cal schemes are driven by engineering considera8ons –  E.g., clock recovery » 35 Clock Recovery •  Um, how many zeros was that? –  Receiver needs frequent signal transi8ons to decode bits 1 0 0 0 0 0 0 0 0 0 … 0 •  How do we address this problem? 36 18 10/6/13 Clock Recovery – 4B/5B •  Map every 4 data bits into 5 code bits with a transi8on that are sent –  0000 à༎...
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