INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous) Dundigal, Hyderabad

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1 Hll Ticket No Question Pper Code: AEC009 INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous) Dundigl, Hyderd MODEL QUESTION PAPER Four Yer B.Tech V Semester End Exmintions, Novemer Regultions: R16 DIGITAL COMMUNICATOINS (ECE) Time: 3 hours Mx. Mrks: 70 Answer ONE Question from ech Unit All Questions Crry Equl Mrks All prts of the question must e nswered in one plce only UNIT - I 1 ) Explin the process of Smpling nd Quntiztion in digitl Communiction. Wht is lising effect in smpled signl? How lising cn e eliminted? Explin with net digrm. ) Discuss quntiztion error? How does it depend upon the step size? Suggest some methods to overcome the difficulties encountered depending on the modulting Amplitude swing? 2 ) (i) Explin the sic principle of DPCM nd working of DPCM trnsmitter nd receiver with the help of digrm. (ii) Derive n expression for chnnel noise in delt modultion. ) A signl m(t)=4 Cos (60 πt) +2 Cos (160πt) +Cos (280 πt) is smpled t150 Hz,75 Hz,300 Hz. Estimte the frequency components of the signl tht pper t the output of n idel LPF with cutoff t 290 Hz. in ech cse. Wht is the Nyquist rte of smpling nd Nyquist intervl form (t)? UNIT - II 3 ) Explin correltion receiver with lock digrm. Also explin why the correltion receiver is lso clled n integrted nd dump filter. ) The it strem is to e trnsmitted using DPSK. Determine the encoded Sequence nd trnsmitted phse sequence. 4 ) Write the comprison mong inry modulted nd pss signling scheme Amplitude Shift Keying (ASK), Phse Shift Keying (PSK) nd Frequency Shift Keying (FSK). ) A voice signl is smpled t the rte of 5000smples/sec nd ech smple is encoded into 5- its using PCM system. The inry dt is trnsmitted into free spce fter modultion. Determine the ndwidth of the modulted signl, if the modultion used is ) ASK ) PSK c) FSK where f1=8mhz nd f2=6mhz UNIT III 5 ) Wht is the need of pulse shping for optimum trnsmission in send trnsmission? Explin in detil.

2 ) The Fourier trnsform P(f) of the sis pulse p(t) employed in certin inry communiction system is given y P(f) = {10 6 (1 ( f / 10 6 )) if 10 6 f(hz) 10 6 ; =0 other wise. From the shpe of P(f), explin whether this pulse stisfies the Nyquist criterion for ISI free trnsmission. () Determine p(t) nd verify your result in prt. (c) If the pulse does stisfy the nyquist criterion. Wht is the trnsmission rte (in its/sec.) nd wht is the roll-off fctor? 6 ) Explin the requirements for line encoding formt nd discuss Vrious line encoding formts with net sketches. ) Wht is the result of scrmling the sequence using B8ZS AND HDB3 scrmling techniques? Assume tht the lst on-zero signl level hs een positive. UNIT IV 7 ) A source is trnsmitting Four symols A, B, C nd D with proilities 1/2, 1/4, 1/8 nd 1/8 respectively. Find the entropy of the source nd find informtion rte if r=1 messges/sec. ) Descrie with net sketch the direct sequence Spred spectrum Wht is ment y Synchroniztion? Why we require synchroniztion in spred spectrum? Explin in detil. 8 ) Define entropy nd explin out the importnt properties of entropy. A source is trnsmitting the symols A nd B with proilities 1/16 nd 15/16 respectively. Clculte the Entropy of the source nd the required chnnel cpcity using the simplest code nd lso coding efficiency. ) One of five possile messge Q1 to Q5 hving proilities 1/4, 1/2, 1/8, 1/16, 1/16 respectively re trnsmitted. Generte Huffmn code nd Clculte the coding efficiency UNIT V 9 ) Wht is the structurl representtion of Liner Block codes nd give the Mtrix description of Liner Block codes. ) Write short notes on following with exmples: ) Convolutionl codes ) Viteri Decoding. 10 ) For liner lock code, prove with exmple tht: i) The Syndrome depends only on error pttern nd not on trnsmitted code word? ii) All error ptterns tht differ y codeword hve the sme syndrome? ) Drw the trellis digrm of Convolutionl code of code rte r=1/2 nd Constrint length of K=3 strting from the stte tle nd stte digrm for n encoder which is commonly used.

3 INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous) COURSE OBJECTIVES S.No I II III IV the different digitl modultion techniques. Description Discuss the importnce of error detection nd correction codes nd use them in the presence of the chnnel. Descrie nd nlyze the methods of trnsmission of digitl dt using send nd crrier modultion techniques. Decompose codes seprtely into source codes nd chnnel codes nd develop competency in modeling nd nlyzing communiction system elements. COURSE OUTCOMES S.No CAEC CAEC CAEC CAEC CAEC CAEC CAEC CAEC CAEC CAEC CAEC CAEC CAEC CAEC Description the sic concepts of pulse mplitude modultion (PAM), pulse position modultion (PPM) nd pulse width modultion (PWM). Descrie the dvntges nd disdvntges of digitl communiction systems nd rememer the concept of pulse code modultion the concept of smpling, quntiztion nd coding. nd rememer the concept of mplitude shift keying modultion nd demodultion. Anlyze the frequency shift keying modultor, coherent nd non-coherent frequency shift keying detectors. Descrie the difference etween inry phse shift keying d qudrture phse shift keying techniques. the concept of send trnsmission nd vrious line coding formts used in digitl communiction systems. Descrie the significnce of pulse shping to reduce inter-symol interference in digitl communictions. the opertion of rised cosine filter nd eye ptterns of vrious ASK, PSK nd FSK digitl modultion techniques.. nd the concept of mutul informtion nd entropy in informtion theory. Design vrious mthemticl modeling schemes for communiction chnnel nd determine their chnnel cpcity. Anlyze vrious spred spectrum modultion schemes such s direct sequence spred spectrum nd frequency hopping spred spectrum. Anlyze the significnce of liner lock codes nd convolution codes in digitl communictions. Interpret the difference etween hmming codes nd inry cyclic codes. Blooms Txonomy Level

4 CAEC CAEC CAEC CAEC vrious types pproches such s time domin pproch nd trnsform domin pproch for implementtion of convolution codes. Design different types of error detection nd correction techniques for liner lock codes nd convolution codes. Acquire experience in uilding nd trouleshooting simple digitl communiction system using digitl modultion nd demodultion techniques. Acquire the knowledge nd develop cpility to succeed ntionl nd interntionl level competitive exmintions. MAPPING OF SEE - COURSE OUTCOMES SEE Question No Course Outcomes Blooms Txonomy Level CAEC009.03: the concept of smpling, quntiztion nd coding. CAEC009.02: Descrie the dvntges nd disdvntges of digitl communiction systems nd rememer the concept of pulse code modultion CAEC009.02: Descrie the dvntges nd disdvntges of digitl communiction systems nd rememer the concept of pulse code modultion CAEC009.02: Descrie the dvntges nd disdvntges of digitl communiction systems nd rememer the concept of pulse code modultion CAEC009.04: nd rememer the concept of mplitude shift keying modultion nd demodultion. CAEC009.06: Descrie the difference etween inry phse shift keying d qudrture phse shift keying techniques. CAEC009.06: Descrie the difference etween inry phse shift keying d qudrture phse shift keying techniques. CAEC009.06: Descrie the difference etween inry phse shift keying d qudrture phse shift keying techniques. CAEC009.08: Descrie the significnce of pulse shping to reduce intersymol interference in digitl communictions. CAEC009.07: the concept of send trnsmission nd vrious line coding formts used in digitl communiction systems 6 CAEC009.07: the concept of send trnsmission nd vrious line coding formts used in digitl communiction systems. 7 CAEC009.09: the opertion of rised cosine filter nd eye ptterns of vrious ASK, PSK nd FSK digitl modultion techniques. CAEC009.10: nd the concept of mutul informtion nd entropy in informtion theory. CAEC009.12: Anlyze vrious spred spectrum modultion schemes such s direct sequence spred spectrum nd frequency hopping spred spectrum. 8 CAEC009.10: nd the concept of mutul informtion nd entropy in informtion theory. CAEC009.11: Design vrious mthemticl modeling schemes for communiction chnnel nd determine their chnnel cpcity. 9 CAEC009.13: Anlyze the significnce of liner lock codes nd convolution codes in digitl communictions.

5 CAEC009.15: vrious types pproches such s time domin pproch nd trnsform domin pproch for implementtion of convolution codes. 10 CAEC009.13: Anlyze the significnce of liner lock codes nd convolution codes in digitl communictions. CAEC009.14: Interpret the difference etween hmming codes nd inry cyclic codes. Signture of Course Coordintor HOD

To provide data transmission in indoor

To provide data transmission in indoor Hittite Journl of Science nd Engineering, 2018, 5 (1) 25-29 ISSN NUMBER: 2148-4171 DOI: 10.17350/HJSE19030000074 A New Demodultor For Inverse Pulse Position Modultion Technique Mehmet Sönmez Osmniye Korkut