Berkeley ELENG 121 - Final Exam (7 pages)

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Final Exam



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Final Exam

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Pages:
7
School:
University of California, Berkeley
Course:
Eleng 121 - Introduction to Digital Communication Systems
Introduction to Digital Communication Systems Documents

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EE 121 Introduction to Digital Communication Systems Final Exam Spring 2003 Please put your name on the front page Answer all the questions on the blank pages provided Explain clearly the steps in your answers Yes no answers with no explanations get no marks Waterfall error probability curves are provided at the back for your use throughout the exam Please reference the appropriate plots when you use them You may want to take a look at them now 10 1 6 a Explain briefly what these concepts mean i entropy ii uniquely decodable codes iii Nyquist sampling theorem iv Nyquist criterion v bi orthogonal modulation vi ISI 4 b Is there any relationship between the delay spread and coherence bandwidth in a wireless channel How about between delay spread and coherence time For each case if there is a relationship explain If not give an example of a wireless channel in which the two parameters can be specified separately 2 10 2 Suppose you have calculated the transmit power link budget for a wireless system assuming uncoded binary pulse amplitude modulation binary PAM also known as BPSK an error probability of 10 4 transmission over an AWGN channel 5 a Suppose now there is flat Rayleigh fading and coherent detection is performed How much extra transmit power is needed This is called the fade margin State clearly how you come up with your answer 5 b Suppose now each symbol is repeated twice and interleaved over different coherence time periods Compared to a how much is the fade margin reduced by 3 15 3 A passband communication system uses ideal sinc pulses and signal at Nyquist rate 3 a What is the difference in terms of symbols transmitted in the in phase and quadrature phase between BPSK binary phase shift keying also known as binary PAM and QPSK in such a system Draw a system diagram for each 4 b Compare the spectral efficiency in bits s Hz and Eb N0 performance of BPSK and QPSK over an AWGN channel for the same symbol error probability pe You can assume that pe is small in



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