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(BI M.Sc. Engg. (EE) Date: July 18, 2010 (Afternoon) Mid-Semester Examination ISLAMIC UNIVERSITY OF TECHNOLOGY (IUT) THE ORGANISATION OF THE ISLAMIC CONFERENCE (OIC) DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING Summer Semester, A. Y. 2009-2010 Course No.: EEE 6407 Time: 90 Minutes Course Title: Digital Communication Full Marks: 75 There are 4 (four) questions. Answer any 3 (three) questions. All questions carry equal marks. Marks in the margin indicate full marks. Programmable calculators are not allowed. Do not write on this question paper. Ned a) b) c) a) b) c) a) b) a) The term matched filter is often used synonymously with correlator. How is that possible when their mathematical operations are different? Describe the basic steps in the demodulation/detection of digital signals. Determine whether or not s;(t) and s(t) are orthogonal over the interval 1.51, << 1.5T,, where s;(¢) = cos(2mf,t + 1), so(t) = cos(2mfgt + gz), and fo = 1/T for the following cases i, fi = fp and py = 2 n ii. fi = fr and p, = 92 a Explain the coherent detection of multiple phase shift keying. Why is it different from coherent detection of MFSK? If a system’s main performance criterion is bit error probability, which of the following two modulation schemes would be selected for an AWGN channel? Show computations, is Binary non coherent orthogonal FSK with = = 13dB 0 ii. Binary coherent PSK with ie =8dB 0 A differentially coherent MPSK system operates over an AWGN channel with an a = 10 dB. What is the symbol error probability for M = 8 and equally likely symbols? 0 Is a detection of differential PSK a coherent or noncoherent one? Give reasons and example to support your answer. Find the optimum (minimum probability of error) threshold Yo, for detecting the equally likely signals s,(t) = [Boos Wot and s2(t) = Cos(Wot + 7) in AWGN, usinga . . 2 correlator receiver. Assume a reference signal of w(t) = feos Wot What is ARQ? Explain three most popular types of ARQ procedures. 10 06 10 09 06 ll 
