ELET 331 Communication Systems

1. Examine Waveform A in the following figure. This waveform represents the output of a transmitter using PAM with raised cosine pulse shaping at a data rate of 50,000 bits/sec. The transmitter sends pulses of amplitude 1 volt to signify a "'1" and pulses of amplitude -1 volt to signify a "0".

a. What is the data pattern represented by Waveform A? Explain how you obtained your answer.

b. Now examine Waveforms Band C in Figure P3-14. Waveforms A, B, and C all represent the output of transmitters using PAM with raised cosine pulse shaping. All three waveforms represent the same data sequence, use pulses of the same amplitude, and operate at the same transmission speed. The only difference between the three waveforms is that they were produced using different rolloff factors. One of the three waveforms uses α = 0, another uses α = 0.5, and the remaining waveform uses α = 1. Identify which rolloff factor is used by each of the three waveforms. Explain how you obtained your answer.

c. What is the bandwidth of each ofthe three waveforms?

2. Example 4.6 transmits raised cosine pulses with amplitudes of+ 1 volt and -1 volt and achieves a probability of bit error of 0.2%, which is too high for most practical applications (see the comments at the end of Section 4.1.5 concerning probability of bit error values for typical systems). To what minimum value must the pulse amplitudes be increased to reduce the probability of bit error below 0.1 %?

3. Repeat Problem 2 if the channel attenuates power such that the average normalized power of the received signal is one third the average normalized power of the transmitted signal.

4. A PAM system is transmitting rectangular pulses at 10,000 bits/sec. A correlation receiver is employed. Noise power spectral density at the receiver is No/2=10-6 volts2, and the channel attenuates the transmitted signal by 70% (so that only 30% of the transmitted signal arrives at the receiver). Assuming perfect synchronization at the receiver, what is the minimum pulse amplitude needed at the transmitter to guarantee a probability of bit error less than or equal to 10-3?

Attachment:- Communication Systems.rar