Qassim University
College of Engineering
Department of Electrical Engineering
Electronics and Communications
Course EE322: Digital Communications
HW #3
14/2/2016
1) The binary data 101000l11 are applied to the input of a duobinary system without a
precoder.
(a) Find the duobinary coder output signal and the corresponding receiver binary output.
(b) Suppose that due to error during transmission, the third digit at the receiver input is in
error. Find the new receiver binary output.
2) Repeat Problem (1) above, assuming the use of a precoder in the transmitter.
3) The binary data 110010l00 are applied to the input of a modified duobinary system
without a precoder.
(a) Find the modified duobinary coder output signal and the corresponding receiver binary
output.
(b) Suppose that due to error during transmission, the third digit at the receiver input is in
error. Find the new receiver binary output.
4) [HW1] Repeat problem (3) above, assuming the use of a precoder in the transmitter.
5) An analog signal is sampled, quantized, and encoded into a binary PCM wave. The
specifications of the PCM system include the following:
Sampling rate = 8 kHz and the number of quantizer representation levels = 64.
Assuming that the binary stream of the PCM wave is transmitted using M-ary PAM
system designed to have the following number of amplitude levels M:
(a) M = 4
(b) M = 8
Determine the Nyquest transmission channel bandwidth required.
6) Consider 8-ary PAM system signaling at 50 kbaud. Calculate the system bit rate?
Determine the smallest pulse amplitude A0 in volt that must be received for the
average symbol error rate not to exceed 4x10-5 , if the channel noise power spectral
density No/2 = 6.25x10-8 volts2/Hz at the input of the decision device at the receiver,
Find the gray code for the eight levels of the system. Sketch the output waveform
for such system for the following input bit stream:
1 0 1 0 1 1 0 1 0 1 0 0 0 10
7) A computer outputs binary data at the rate of 56 kilobits per second. The computer
output is transmitted where each set of three successive binary digits in the computer
output are coded into one of eight possible amplitude levels, and the resulting signal is
transmitted by using an 8-level PAM system designed to have a raised cosine spectrum.
Determine the transmission bandwidth required for each of the following rolloff factors:
(a) α = 0.25
(b) α = 0.5
(c) α = 0.75
(d) α = 1.0
8) [HW2] A 15 KHz-analog signal is sampled at Nyquist rate, quantized using 256-level
quantizer and encoded. If the PCM output binary stream is transmitted using either:
1. Polar NRZ signaling with a raised cosine spectrum whose rolloff factor α = 0.75,
a) Calculate SNR (Eb/No) in dB if there is one bit in error every 10 kbits.
b) Calculate the minimum transmission channel BW.
2. 16-ary PAM system, designed to have a raised cosine spectrum of α = 0.75,
a) Calculate the minimum transmission channel BW. Compare & Comment
b) Calculate the symbol probability of error (Assume Eo= Eb log2M).