CSE 123 Lecture Notes - Lecture 22: Demodulation, Background Noise, Error Detection And Correction

• School: UCSD
• Department: Computer Science and Engineering
• Course: CSE 123
• Professor: Alex Snoeren

Document Summary

Modem (modulator demodulator): communicating with computers over old phone lines! Take input stream of bits (digital data) Modulate some physical media to send data (analog) Each symbol is designed to look different to make it easy to differentiate. A signal is some form of energy (light, voltage, etc. ) A channel is a physical medium that conveys energy. Any real channel will distort the input signal as it does so. How it distorts the signal depends on the signal. Distortion impacts how the receiver will interpret the signal. Bandwidth really deals with the frequency range of the band that passes the channel. A channel is responsive if it can handle that frequency, and non-responsive otherwise. Any signal going through any real channel will be distorted! (not perfect) Means channel is slow to react to change in signal! Signal gets softer (harder to hear) the further it travels. Background noise or interference may add/subtract from original signal!