computer networks

Question

A high quality speech signal has a bandwidth of 8khz.suppose that the speech signal is to quantized and then transmitted over a 28.8kbps modem. What is the signal to noise ratio(in DB) of the received signal? what modem sped is needed if we  require an SNR of 40 db?

Answer 1

AS we know that C=(B x SNR_dB)/3

Where C= Capacity of the channel

B=Bandwidth

SNR_dB=Signal to Noise Ratio in Decibels

Here B=8kHz

Speed of Modem=28.8kbps

(28800/8000)x3=SNR_dB =>10.8

if SNR_dB=40

then (Speed of Modem/8000)x3=40

=> Speed of Modem = (40*8000)/3=106.6kbps