The serial ports on two computers which use binary signallin

The serial ports on two computers which use binary signalling are connected by a twisted pair of cable. The cable has a flat frequency response up to 12Khz, with negligible group delay distortion. A)what is the max information transfer rate that can be accommodated by the cable, assuming a noise-free environment. B)If the noise introduced by the cable is -40dB with respect to the signal power, what is the resultng max information transfer rate?

Solution

a)Symbol rate = 1/(1/12000) = 12000 symbols/second

The information transfer rate for this however, is 24000 bps, as each symbol conveys two bits i.e,2*12000symbols/second

b) giiven   10logN/S = -40db

               N/S= 10^-4

             max info tranfer rate= C= [Blog(S/N +1)]/log2

                                                 = [12000*log(1+10^4)]/log2

                                               C = 159.45kbps