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Ph.D./M.Se.Engg.(E), { D7 Date: 13 July, 2011 (Afternoon) ISLAMIC UNIVERSITY OF TECHNOLOGY (IUT) ORGANIZATION OF ISLAMIC COOPERATION t DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING Mid-Semester Examination Summer Semester, A.Y. 2010-2011 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. 1. (a) Show that the sampling rate, fs needs to be at least twice the bandwidth of the 19 information signal in order to avoid Aliasing. (b) Draw the protocol stack for UMTS. Which channel in physical layer does carry paging 6 message? (c) Determine a 16 bits long OVSF code 7 2. (a) Derive the following expression for mean square quantization error. 12 ee 12 (b) What is the spreading factor to support 48 kbps data in UMTS? How many users can use. a this data rate in a cell? (c) How many Secondary Scrambling Codes (SSCs) do exist in UMTS? How many chips 6 do exist in a slot? 3. (a) Show how cumulative error is prevented by applying feedback for Differential Pulse 12 Code Modulation (DPCM)+ _ (b) How the users are differentiated in different cells in uplink and downlink in UMTS? 6 What are the possible values of Transmission Time Interval (TTI)? (c) Draw the diagram with shift registers to generate Gold sequence of 2° ~ 1 length. What Th is the code length used in downlink and uplink in UMTS. 4. (a) Draw the network diagram for UMTS and mention the purpose of its components. 7. (b) What is the purpose of companding? Explain the drawbacks of delta modulation. i 8 (c) Determine autocorrelation properties of the sequence 0110101 by rotating its whole 10 length. 
