电信系统所有题20112012题目b

1、Complete the information below about yourself very carefully.QMnumberBUPTnumberClass numberMake and type of any electronic calculator youare usingJoint Programme Examinations 2012/13EBU 5302 Telecommunications SystemsPaper BAnswer ALL questions Time allowed: 2 hoursExaminersProf Laurie Cuthbert, Dr

2、Michael Chai, Dr Frank GaoCopyright ©University of Posts and Telecommunications & © Queen Mary, University of London 2012Filename: 1213_EBU5302_BNo answerbook requiredINSTRUCTIONS1. You must not take answer books, used or unused, from the examination room.2. Write on both sides of the

3、paper.3. Write only in black or blue pen and in English.4. Do all rough work in the answer book do not tear out any pages.5. If you use Supplementary Answer Books, tie them to the end of this book.6. Write clearly and legibly.7. the instructions on the inside cover.InstructionsBefore the start of th

4、e examination1) Place your BUPT and QMcards on the corner of your desk so that your picture is visible.2) Put all bags, coats and other belongings at the back/front of the room. All small items in yourpockets, including wallets, mobile phones and other electronic devices must be placed under your de

5、sk. Possession of mobile phones, electronic devices and unauthorised materials is an offence.3) Please ensure your mobile phone is switched off and that no alarm will sound during the exam. Amobile phone causing a disruption is also an assessment offence.4) Do not turn over your question paper or be

6、gin writing until told to do.During the examination1) You must not communicate with or copy from another.2) If you require any assistance or wish to leave the examination room for any reason, please raise yourhand to attract the attention of the invigilator.3) If you finish the examination early you

7、 may leave, but not in the first 30 minutes or the last 10minutes.4) For 2 hour examinations you may not leave temporarily.5) For examinations longer than 2 hours you may leave temporarily but not in the first 2 hours or thelast 30 minutes.At the end of thee examination1) You must stop writing immed

8、iately if you continue writing after being told to stop, that is anassessment offence.EBU5302 Paper B (2012-13)Question 1a)State and briefly explain THREE features of ATM.6 marksb)Calculate the cell assembly delay to fill a cell with samples of PCM-encoded speech.3 marksc)ATM cells are to be used to

9、 transport data packets of length 1000 bytes. Assuthat 2 bytes ofprotocol control information (header and trailer) are required at the segmentation and reassembly sublayer, determine the number of ATM cells that would be needed to transport that data.4 marksd)Explain why the minimum protocol control

10、 information to allow reliable segmentation and reassembly is at least 1 bit to mark the first or last ATM cell.4 markse)A quser covering the range ±8V is used to convert a signal with peak-peak voltage of ±4V toan 8-bit digital signal. Calculate the signal to distortion ratio (in dB) for

11、(i) a sine wave and (ii) a square wave.8 marksWrite your answer belowPage 3 of 16Do not write in this columnEBU5302 Paper B (2012-13)Page 4 of 16Do not write in this columnEBU5302 Paper B (2012-13)Question 2a) With the aid of suitable diagrams explain how the sliding window protocol works showing (i

12、) the case where acknowledgements are received in time and (ii) when an acknowledgement is missed. (Hint: use a separate diagram for each case).7 marksb) A sliding window protocol is used over a channel with a bit-error probability p. Assuthatpackets are not lost for any other reason and there is si

13、ngle-bit error correction in use, show thatrthe effective bitrate is r¢ =where r is the bit rate on the channel, W is theeffN (N -1) p2(1+W)2window size and N is the packet length in bits.8 marksc) The figure below shows the probability state diagram for a 2-state Markov source.Calculate the pr

14、obability of the symbol sequence AAB occurring.6 marksd) For the following services state whether FEC or ARQ is more suitable as an error correction approach and why:i) Satellite TV broadcast;ii)conferencing.4 marksWrite your answer belowPage 5 of 16Do not write in this columnEBU5302 Paper B (2012-1

15、3)Page 6 of 16Do not write in this columnEBU5302 Paper B (2012-13)Page 7 of 16Do not write in this columnEBU5302 Paper B (2012-13)Question 3a)Use equations and a block diagram to show how an OFDM demodulator works.12 marksb)AssuPN=00fast FHSS Using MFSK (M=4, k=2, input binary data = 010), draw a ta

16、ble with proper notations1, andshowing how the data is transmitted.9 marksc)Show that doubling the transmission frequency or doubling the distance between transmitting antenna and receiving antenna attenuates the power received by 6dB.4 marksWrite your answer belowPage 8 of 16Do not write in this co

17、lumnEBU5302 Paper B (2012-13)Page 9 of 16Do not write in this columnEBU5302 Paper B (2012-13)Question 4a)Thesystem sends oage 500 requests to the server per second, and each request is 150bytes. The server takes 0.5 µs to deal with a single request. Calculate the utilisation of the server.2 mar

18、ksb)In a M/M/1 queue, the probability of a given queue size, k, in equilibrium is given byP(k ) = r k (1- r ) for k ³ 0where P(k) is the probability of a queue size equals to k and is the utilisation of the system.i)Plot P(k)(k) for part i) for 0 k 10. Hints: Use log-linear scaleii)Evaluate and

19、 discuss, with the aid of the plot obtained in part i), the effect on the systems queue size distribution if the utilisation of the system is to be increased to 0.8.10 marksc)Briefly explain the differences between preset equalisation and adaptive equalisation. In your answer also describe how these two equalisations can be used in the same system.8 marksd)Explain how three-tap zero forcing equaliser can reduce intersymbol interference (ISI) to a