NATIONAL INSTITUTE OF TECHNOLOGY, Arunachal Pradesh

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1 NATIONAL INSTITUTE OF TECHNOLOGY, Arunachal Pradesh (Established by Ministry of Human Resources Development, Govt. Of India) Yupia, District-Papum Pare, Arunachal Pradesh M.Techl20I End-semester Examination (July-Dee 2015) 5IESIMCCIlIA Mobile and Wireless Communication (CSE - 900) Time: 3 Hours Max. Marks: 100 Instructions: 1. Answer as many questions as you can from each unit separately. 2. The question paper consists of 4(four) units of35 marks each, out of which the maximum score will be limited to 25 marks only. UNIT I Q 1. An urban area has a population of 2 million residents. Three competing trunked mobile networks (system A, B, C) provide cellular service in this area. System A has 394cells with 19 channels each, system B has 98 cells with 57 channels each, and system C has 49 cell each with 100 channels. Find the number of users that can be supported at 2% blocking if each user averages 2 calls per hour at average call duration of 3 minutes. [10] Q2. Fig. 1 shows the data collected for Delhi city for the year Propose solutions/methods/techniques to improve the call setup success rate, Rx Quality, Handover success rate and to reduce the blocked call rate and dropped call rate. [20]

2 Reliance,, i Tata _!I!!l!IAL % L8O'lb 91.%% 62.71% 99.10% ~re~~, J.729%! (184% ---' -----'--'--;;~;--;;;-"-~~t-;;;~ ~i-- Suctess 97.85%98.65%, '1415% S5.9<1% %.86% i 9412% Coutesy hnp:ilvrvrw.thcltindu..cominews.icitieslddbijcentre-telecos-m..blamegame..ovtt..can..drop farticle7s'4539.ect'?homcpag,e"'tnl( f.ij.. 1 Q3. Assume a cellular system wherein a car travels at 200 km/hour speed. Calculate how often (approximately) handoffs would occur if the radius of the cell is 8 Ian? [5] UNIT II Q4. [4 x 5 = 20] - a. Find the median path loss using okumura's model for d=50 lan, hte=iooill, hre=iomin a suburban environment? If thebase station transmitter radiates an EIRP of IkW at a carrier frequency of 900 MHz, find the power at the receiver (assume a unity gain receiving antenna)..b. If a transmitter produces a 60 W of power, express the transmit power in units of (a) dbm, (b) dbw. If 60W is applied to unity gain antenna with a 850 MHz carrier frequency, find the received power in dbm at a free space distance of 100 m from the antenna. What is Pr< 10 km)? Assume unity gain for the receive antenna. c. Explain Small-Scale Fading and Multipath. d. Consider a transmitter which radiates a sinusoidal carrier frequency of 950 MHz. For a vehicle moving 60 mph,

3 compute the received carrier frequency if the mobile is moving i. Directly toward the transmitter ii. Directly away from the transmitter iii. In a direction which is perpendicular to the direction of arrival of transmitted signal. Q5. If the received power at a reference distance do = lkm is equal to 1 microwatt, find the received powers at distances of 2 km, 5 km and 20 km from the same transmitter for the following path loss models: (a) Free space; (b) Log-distance Path Loss Model with n = 4; (c) 2-ray ground reflection; (d) Okumura model; (e) extended Hata model. Assume fc = 1800 MHz, h t =40 m, h, = 3m, G, = G r = 0 db. [3 x 5 = 15] UNIT III Q6. [7 x 5 = 35] a. How can you say that the spread spectrum system becomes spectrally efficient and in what sense? b. Explain GMSK Transmitter and Receiver. c. A PN sequence is generated using a 3-stage linear feedback shift register shown as below, with initial state (Q3Q2QJ)=(001). This sequence used is in a slow FHlBFSK system. o/p Modulo-2 Adder Illustrate the variation of the frequency offhlbfsk signal for one complete period of the PN sequence. Assume that

4 the Hopping Interval (TH)=2Tb, where Tb is bit duration. Assume the binary data to be {bd = { }. d. Compare TOMA, FOMA and COMA. e. Given a cellular system in which the one-way bandwidth of the system is 12.5 MHz, the channel spacing is 30 khz, and the guard band at each boundary of the spectrum is 10 khz. If i. The cell area is 6 km", 11. The frequency reuse factor is 7 and iii. 21 of the available channels are used to handle control signalling, calculate 1. The total number of available channels per cluster 2. The number of available data channels per cluster 3. The number of available data channels per cell 4. The system spectral efficiency in units CJf channelslmhzlkm 2 f. Compare Amplitude Modulation and Frequency Modulation for mobile communication. g. In a communication system, data is transmitted through sine wave signal. Express the signal in mathematical form in both time domain and frequency domain if Vm=peak voltage, f is the carrier frequency, t = time and cp = phase angle. If the signal travels with the speed of light, c, find the wavelength. UNIT IV Q7. Write a short note on evolution of mobile radio communication. [10]

5 Q8. Define the following term a. Trunking b. Handoff c. Mobile Communication d. Grade of Service e. Traffic Intensity f. Near-Far Effect g. Inter Symbol Interference h. Bandwidth Efficiency i. Null-to-null Bandwidth j. Absolute bandwidth k. Half-power bandwidth 1. Signal to Interference ratio m. Co-channel cells n. Erlang o. Fading p. Mobile station q. Doppler Shift r. Propagation Model s. Effective Aperture t. Path Loss u. Multipath Channel v. Multiple Access w. Multiplexing x. Duplexing y. Fraunhofer region [1 x 25 = 25]

6 Outdoor Propagation Models "7 70 Urban Asea ht~200m 60 hr ~ 3 m m 50 ":: 50 ~-III( 30 i ~ c 10 ~ 5 e i Freq.,.ncy t (MHz) Figure 3.23 Median attenuation relative to free space (AmJf.d), over a quasi-smooth terrain [From roku68] IEEE). factors can be added or subtracted as required. All these correction factors are

7 118 Ch. 3 Mobile Radio Propagation: Large-Scale Path Loss D 25!!.. :5 ~ e 20 3S..,,, " ,.. fili15. " " 10 5 o Frequency, fmhz) Figure 3.24 Correction factor, G ARU., for different types oft~~~o~m~i~o~k~u 688..L::~~J,;LL. -_~ -

8 Number of Trunked Channels (C) 0.1 'I...,.,... 1,', !..., O.OS j..,.,~..., I JS.".41»., , t. I II, I j J j»j i J" is ii' fi.' \.J '1 I. " I. \. 'L.,,' 0,02 J>. (0 IIii 0.01 't) ~ :3.0.a,t 0.005,.,. # ',.' "1'.' ;". i', i '.'...,.,.". 01.;.,.. ','.: '/" "..... '". I I.,1 ""0.' name Intenlity in Frlanp Figure 2.6 The Erlang B chart showing the probability of blocking as functions of the number of channels and traffic intensity in Erlangs.

9 1.0 L. ~.... ; :... o.s r :... ~... Number of Trunked Channels (C) : :7i '-, 4,,w 2 1III 15 '- I;"". i I,. j, i :..,~., J. t I,. I.,, 4. " " U'I o! 0.2 '0 l;- 0.1 s Io.os,.,.,1, "l :., 0".' ; t... I 'I. :..!.,...,!,.... ".. {!. 11-:..:..!.!t: ~.., f I ~ 1!.!I- t.: I L; ; ; { ; ; ; t;! I '; f ';';1 '; ;';; I I I,;,; I ; I ;', IE; I O.s Traffic InteDlity in Brian Figure 2.7 The Erlang C chart showing the probability of a call being delayed 8S a function ~fthp number of channels and traffic intensity in Brlongs