lecture12

# lecture12 - Lecture Outline Digital Transmission Reading...

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Lecture Outline Digital Transmission Reading: textbook sections 7.1, 7.2 Material covered: 1. Shannon Channel Capacity formula For a channel of bandwidth W , and a Signal to Noise (SNR) ratio of S/N, reliable (i.e. error free) transmission is possible for data rate R less than channel capacity C : ) 1 ( log 2 N S W C R + = ; Noise power W N N 0 = where 2 / 0 N is the amplitude of the spectral noise. Example: A phone line has a SNR ratio of 20dB and a bandwidth of 100 KHz. Its capacity is given by 5 2 5 2 10 66 . 6 ) 100 1 ( log 10 ) 1 ( log × = + = + = N S W C = .666 Mb/s If we increase SNR to 30 dB (10 times more power), we increase capacity to 1 Mb/s. Intuitive explanations: For a signal with bandwidth W (both sidebands), we can obtain W independent samples per second according to Nyquist sampling theorem. For each sample, we can effectively quantize the sample into (1+ S/N ) levels. Question: How can we achieve Shannon capacity?

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## This note was uploaded on 11/01/2009 for the course EEE 455 taught by Professor Hui during the Spring '09 term at ASU.

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lecture12 - Lecture Outline Digital Transmission Reading...

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