Modulation and Encoding: Transmitting Digital Signals, Slides of Computer Networks

Download Modulation and Encoding: Transmitting Digital Signals and more Slides Computer Networks in PDF only on Docsity! Modulation and Encoding • Modulation – Amplitude • Two amplitudes to represent a 0 and 1 – phase • Two phases to represent a 0 and 1 – Frequency • Two frequencies to represent a 0 and 1 Docsity.com amplitude modulation frequency modulation phase modulation 1 0 1 1 Docsity.com 0 0 1 0 1 1 1 0 0 0 middle high to low low to high NRZ 00 1 0 1 1 1 1 0 1 NRZI Docsity.com Manchester coding: Used in Ethernet EXOR of clock and NRZ 0 0 1 0 1 1 1 0 0 0 clock clock Manchester Docsity.com Physical Layer • Xmitter/Rcvr – Trasmitter/receiver • Amp/rep – amplifier/repeater Xmitter/ Revr Medium Amp/ rep Medium Xmitter/ Revr Docsity.com Data Rate • Example: Signal takes one of 0, 1, …, 15 volts – BaudRate – b/s – Each signal value represents 4bits – Data Rate = b*4 bits/s – Greater the baudrate, greater the bandwidth required to transmit the signal • Shannon’s theorem Docsity.com Data Rate • Nyquist rate: – signal passed through a low pass filter of bandwidth H recover from 2H samples. • Clean Channel: – Maximum Data Rate = 2H log2V bits/s • V – number of discrete lines • Noisy channel: – Maximum Data Rate = H log2 (1+S/N) bits/s • S/N – signal to noise ratio Docsity.com