Assignment Spring 2017
Module: Digital Communication (ELEC 20004) ID NUMBER
Level: 2 Max. Marks: 100
Session: All
Assignment Outcomes
Differentiate the types of pulse modulation techniques implemented in communication systems;
Critically evaluate the baseband demodulation and detection techniques;
Critically evaluate digital modulation techniques including multi-level digital modulation.
Guidelines:
Please add front title page with your answers uploaded on Moodle.
Each question carries 20 marks.
Assignment answers must be computer typed. Please do not write question statement. Just mention the question number.
Font - Times New Roman
Font – Style - Regular
Font - Size - 12
Soft copy of the assignment is to be submitted online in Moodle through turnitin.
Each student has to do the assignment individually.
Explain with suitable diagrams wherever required.
The final assignment must have a Title Page, table of contents, references/ bibliography and page number.
Heading should be with Font Size 14, Bold, and Underline.
You can refer books in Library or use internet resource. But you should not cut and paste material from internet nor provide photocopied material from books. The assignment answers should be in your own words after understanding the matter from the above resources.
Rules & Regulations
If any coursework assessment is found to be copied from other candidates using unacceptable means, then it shall be cancelled and the total marks awarded will be zero. No chance of resubmission or appeal will be given*.
Your source of information should be mentioned in the reference page clearly. (For example: If it’s from book, you have to mention the full details of the book with title, author name, edition and publisher’s name. If it is from the internet you have to mention the correct URL). Otherwise the assignment will be considered as plagiarized*.
The students may be asked to appear for a viva voce to validate the assignment solutions submitted. The viva voce does not carry any marks.
Title Page must have Assignment Name, Module name, your name, ID, Section and the name of the faculty.
For late submission, 5% of the awarded marks will be deducted for each working day.
For plagiarism, please refer to student guide and clarification uploaded on Moodle.
Refer MIG for feedback dates on assignment.
No assignment will be accepted after one week from the date of submission*.
Date of submission 23/5/2017
Feedback will be provided in the answer script within 2 weeks of submission deadline.
* Refer to the MIG for MEC policy on academic integrity and late submission.
QUESTIONS:
1 Consider a impulse sampling system whose sampling frequency is 500 Hz.
i. Draw the output waveform for a duration 0 to 0.03 Sec., when a sinusoidal signal of frequency f1=50 Hz and peak amplitude 10 volt is given as input signal. (7 Marks)
ii.
Draw the output waveform for a duration 0 to 0.03 Sec., when a sinusoidal signal of frequency f2= 550 Hz and peak amplitude 10 volt is given as input signal. (7 Marks)
iii. Compare the outputs and critically analyse reconstruction of original signal from the output samples. (6 Marks)
2 a. Baseband demodulation system in digital communication largely depends on the Eb/N0 ratio. Whether it is possible to have two digital communication systems with same Eb/N0 but with different S/N ratio? Justify your answer with suitable explanations. (4 Marks)
b. A channel is providing a S/N ratio of 30dB. When the bandwidth of signal is 10 KHz, the value of Eb/N0 is found to be 16.99 dB. If same channel is used with same signal bandwidth but with a different data rate. It is observed that the new Eb/N0 is reduced by 75%. Calculate the new value of Eb/N0 and data rate. (16 Marks)
3 A designer is asked to design a digital transmission system where the quantization distortion error of any audio source does not exceed ±1% of the peak-to-peak audio source.
a. If the audio signal bandwidth and the allowable transmission bandwidth are each 8000 Hz, and the sampling takes place at the Nyquist rate, what value of bandwidth efficiency (bits/s/Hz) is required? (9 Marks)
b. Repeat part (a) except that the audio signal bandwidth is now 20 kHz (the available transmission band width is still 8000 Hz). (6 Marks)
c. Find symbol rate in part (a) if 16-level (M=16) M-ary PAM transmission system is used.
(5 Marks)
4 a. Compare Quadrature Amplitude Modulation (QAM) and Amplitude Shift Keying (ASK) in terms of its error performance and data rate. (6 Marks)
b. binary data is transmitted over a channel at a rate of f0 bits/sec. To reduce the transmission bandwidth, it is decided to transmit this data using 16-ary symbol.
By what factor is the bandwidth reduced? (4 Mark)
What will be the increase in the transmitted power when the separation between pulse amplitude is same in both cases. Calculate the difference in maximum power level between ASK and 16-ary symbol in this case.
(10 Marks)
5 a. In a broadcasting system an analog signal is sampled at a rate of 100KHz. The sampled signal is passed through a spectrum analyzer which gives the amplitude of the sampled signal for various frequency values. What will be the signal bandwidth for the following cases:
The gap between the sample spectrum is 100Hz. (3 Marks)
The gap between the sampled spectrum is 5KHz. (3 Marks)
If the sampled spectrum is passed through a low pass filter for reconstruction, which case mentioned in part(i) and (ii) requires less stringent requirement for the low pass filter? Justify your answer. (4 Marks)
b. The data rate of binary Amplitude Shift Keying (ASK) system is 4.8Mbps. Assuming Additive White Gaussian Noise (AWGN) channel having a bandwidth of 10MHz, the noise present in the channel has zero mean with power spectral density of 10-15W/Hz. If the received signal amplitude is 1mV, determine the average probability of error for the coherent ASK detector.
(10 Marks)