UNIT-I INTRODUCTION TO WIRELESS COMMUNICATIONS

AND CELLULAR CONCEPT OBJECTIVE QUESTIONS

1. 3G W-CDMA is also known as [ ]

a. UMTS b. DECT c. DCS-1800 d. ETACS 2. Commonly used mode for 3G networks is [ ]

a. TDMA b. FDMA c. TDD d. FDD 3. The minimum spectrum allocation required for W-CDMA is [ ]

a. 5MHz b. 2MHz c. 500 KHz d. 100 KHz 4. CDMA2000 1xEV provides high speed data access with channel allocation of [ ]

a. 5MHz b. 50 MHz c. 1.25 MHz d. 4MHz 5. In TD-SDMA, there is a frame of __milliseconds and the frame is divided into ___ time slots. [ ]

a. 5, 7 b. 7, 5 c. 2, 5 d. 5, 2 6. The interference between the neighboring base stations is avoided by [ ]

a. Assigning different group of channels b. using transmitters with different power level c. Using different antennas d. All of the above

7. Radio capacity may be increased in cellular concept by [ ] a. Increase in radio spectrum b. increasing the number of base stations & reusing the channels c. Both a and b d. None of the above

8. The shape for the cellular region for maximum radio coverage is [ ] a. Circular b. Square c. Oval d. Hexagon

9. Hexagon shape is used for radio coverage for a cell because [ ] a. It uses the maximum area for coverage b. Fewer number of cells is required c) It approximates circular radiation pattern d). All of the above

10. Centre excited hexagonal cells use [ ] a. Sectored directional antennas b. Omni directional antennas c. Yagiuda antennas d. None of the above

11. Spectrum Efficiency of a cellular network is [ ] a. The traffic carried by whole network b. The traffic carried per cell divided by the bandwidth of the system and the area of a cell. c. Expressed in Erlang /MHz /km2 d. Both b) and c)

12. The advantage of using frequency reuse is [ ] a. Increased capacity b. same spectrum may be allocated to other network c. Limited spectrum is required d. All of the above

13. The strategies acquired for channel assignment are [ ] a. Fixed b. Regular c. Dynamic d. Both a) and b)

14. In a fixed channel assignment strategy, if all the assigned channels are occupied, the call [ ] a. Gets transferred to another cell b. Is kept on waiting c. Gets blocked d. All of the above

15. In a fixed channel assignment strategy [ ] a. Each cell is assigned a predetermined set of frequencies b. The call is served by unused channels of the cell c. The call gets blocked if all the channels of the cell are occupied d. All of the above.

16. In a dynamic channel assignment strategy, [ ]

a. Voice channels are not permanently assigned b. The serving base station requests for a channel from MSC c. MSC allocates the channel according to the predetermined algorithm d. All of the above

17. Advantage of using Dynamic channel assignment is [ ] a. Blocking is reduced b. Capacity of the system is increased

c. Both a) and b) d. None of the above 18. Disadvantage of using Dynamic channel assignment is [ ]

a. More storage required b. Calculations and analysis is increased c. Both a) and b) d. None of the above

19. The total number of duplex channels C, can be used as a measure of capacity and is given by [ ] a.C = M/N b) C= MN c) C = M k N d) C = Mk/ N

20. In Handoff [ ] a. Process of transferring the call to the new base station b. transfers the call c. New channel allocation is done d. All of the above

21. Delay in handoffs is caused due to [ ] a. Week signal conditions b. Unavailability of the channel c. High traffic conditions d. All of the above

22. Inter system Handoffs are done [ ] a. When mobile station moves in two cellular systems with different MSC b. When mobile station moves between two cellular systems c. When mobile station receives more power from other base station than the serving BS d. All of the above.

23. When a fraction of assigned channel is reserved for handoffs, it is [ ] a. Guard channel concept b. Dynamic channel assignment c. Fixed channel assignment d. None of the above

24. While handoffs, the termination of call may be avoided by [ ] a. Providing Guard channel b. Both a) and b) c. Queuing of handoffs d. None of the above

25. Dwell time is the time for [ ] a. A call within the cell b. waiting for channel allocation c. Hand off d. None of the above

26. Dwell time depends upon [ ] a. Interference b. Distance between the subscriber and the base station c. Propagation of call d. All of the above

27. In Mobile Assisted Handoff (MAHO), the handoff takes place when [ ] a. The power received by the mobile station from other base station > the serving base station b. The channel allocated is not available c. The mobile station has no signal d. All of the above

28. Mobile Assisted Handoff (MAHO) provides [ ] a. Faster handoffs b. MSC need not monitor the signal strength c. Suitability for frequent handoffs d. All of the above.

29. Trunking in a cellular network refers to [ ] a. Termination of a call b. Spectrum unavailability c. Accommodating large number of users in limited spectrum d. All of the above

30. When all of the radio channels are in use in a trunking system [ ] a. The user is blocked b. The queue may be provided c. The access to the system is denied d. All of the above

31. Umbrella cell approach [ ] a. Uses large and small cells b. Uses different antenna heights c. used for high speed users with large coverage area & low speed users with small coverage area d. All of the above.

32. Interference in cellular systems is caused by [ ] a. Two base stations operating in same frequency band b. Two calls in progress in nearby mobile stations c. Leakage of energy signals by non-cellular systems into cellular frequency band d. All of the above

33. Interference in frequency bands may lead to [ ] a. Cross talk b. Blocked calls c. Missed calls d. All of the above

34. Co- channel reuse ratio depends upon [ ] a. Radius of the cell b. Distance between the centers of the co channel cells c. Frequency allocation of nearest cells d. Both a) and b)

35. Increase in Co- channel reuse ratio indicates [ ] a. Better transmission quality b. larger capacity c. Low co-channel interference d. Both a) and c)

36. Grade of service refers to [ ] a. Accommodating large number of users in limited spectrum b. Ability of a user to access trunked system during busy hour c. Two calls in progress in nearby mobile stations d. high speed users with large coverage area

37. Traffic intensity is expressed in [ ] a. Erlangs /MHz /km2 b. λ/ sec. c. Erlangs d. dB/sec

38. The techniques used to improve the capacity of cellular systems are [ ] a. Splitting b. Coverage zone approach c. Sectoring d. All of the above

39. What is intersystem handoff? [ ] a) During a course of a call b) Soft & hard handoff c) Hard handoff d) none of the above

40. Which type of handoff used in CDMA? [ ] a) Soft handoff b) Soft & hard handoff c) Hard handoff d) none of the above

2 MARKS QUESTIONS

1) Write some examples for wireless communication system.

2) What is base station?

3) What is MSC?

4) What do you mean by forward and reverse channel?

5) What is the function of control channel? What are the types?

6) Define Cell.

7) What is foot print?

8) What is Channel assignment? What are the types?

9) What is fixed channel assignment?

10) What is dynamic channel assignment?

11) What is hand off?

12) Define Dwell time.

13) What is soft handoff?

14) What is co channel Interference?

15) Define co-channel reuse ratio.

16) Define adjacent channel interference.

17) Define Grade of Service.

18) What is blocked call clear system (BCC)?

19) What is blocked call delay system?

20) Define cell splitting?

UNIT-I

INTRODUCTION TO WIRELESS COMMUNICATIONS AND CELLULAR CONCEPT

10 Mark questions

1) Write about Evolution of a Mobile Radio Communication Systems in detail. 2) Discuss the following Examples of Wireless Communication Systems in detail.

a) Paging Systems b) Cordless telephone Systems c) Cellular Telephone Systems. 3) What is 1G mobile Communications? Discuss the following briefly.

a) AMPS b) FDMA 4) Give the details about the following types of 2G and 2.5G mobile communications in detail.

a) GSM b) TDMA c) CDMA d) GPRS 5) What is 3G mobile communications? Give the details about the following types of 3G mobiles.

a) UMTS b) TD-SCDMA c) cdma 2000 1x EV 6) a) What is frequency reuse concept? Take the following ‘N’ values and discuss about the concept.

a) N = 4 b) N = 7

b) If a signal to interference ratio of 15 dB is required for satisfactory forward channel performance

of a cellular system, what is the frequency reuse factor and cluster size that should be use for

maximum capacity if the path loss exponent is a) n = 4 b) n= 3? Assume that there are 6 co-

channels cells in the first tier and all of them are at the same distance from the mobile, use suitable

approximations.

7) Discuss different techniques used for improving coverage and capacity in cellular systems. 8) Write about various types of Handoff processes available briefly. 9) Compare Between FDMA, TDMA, CDMA, and SDMA. 10) a) What is Trunking and Grade of Service? Explain it in detail.

b) How many users can be supported for 0.5 % blocking probability for the Following number of

trunked channels in a blocked calls cleared systems? a) 1, b) 5, c) 10, d) 20, e) 100. Assume each

user generates 0.1 Erlangs of traffic.

UNIT-II

MOBILE RADIO PROPAGATION

OBJECTIVE QUESTIONS

1. What is the source for performance degradation? [ ] a) Thermal noise b) Man-made noise c) Natural noise d) All

2. The received power is attenuated by a factor called [ ] a) Path loss b) Free space loss c) Both a) and b) d) Kinetic loss

3. Scintillation describes the fading caused by [ ] a) Atmospheric changes b) Physical changes c) Thermal noise d) Propagating effects

4. Large scale fading refers to the attenuation in [ ] a) Amplitude b) Phase c) Signal power d) None of the above

5. Small scale refers to changes in [ ] a) Amplitude b) Phase c) frequency d) Both a) and b)

6. Small scale fading manifests due to [ ] a) Signal dispersion b) Time variant behavior c) Both a) and b) d) None

7. The parameters used to describe large scale fading are [ ] a) Reference distance b) Path loss exponent c) Standard deviation of random variable d) All of the above

8. Small scale fading occurs due to [ ] a) Doppler spread b) Time delay c) Doppler shift d) Both b) and c)

9. What are the types of small scale fading that occurs due to Doppler shift? [ ] a) Slow fading b) Fast fading c) Rayleigh fading d) Both a) and b)

10. The effective isotropic radiated power is defined as [ ] a) PtGt b) PtGr c) PtPr d) PrGt

11. Fading is caused due to [ ] a) Multi path propagation b) Obstacles c) Frequency variations at the source d) Variation in amplitude and phase at receiver

12 Coherence time refers to [ ] a) Time required attaining a call with the busy base station b) Time required for synchronization between the transmitter and the receiver c) Minimum time for change in magnitude and phase of the channel d) None of the above.

13. Fading is due to shadowing is [ ] a) Fading due to large obstructions b) Large coherence time of the channel as compared to the delay constraints c) Small coherence time of the channel as compared to the delay constraints d) Both a) and b)

14. Deep fade is [ ] a) Strong destructive interference b) Drop in signal to noise ratio c) Temporary failure of message transfer d) Signal fading due to Doppler shift in the channel

15. Doppler spread refers to [ ] a) Signal fading due to Doppler shift in the channel b) Temporary failure of message transfer c)Large coherence time of the channel as compared to the delay constraints d) All of the above

16. Coherence time is [ ] a) Directly proportional to Doppler spread b) Indirectly proportional to Doppler spread c) Directly proportional to square of Doppler spread d) Directly proportional to twice of Doppler spread

17. Small scale multipath propagation is caused due to waves with [ ] a) Different propagation delays b) Different amplitudes c) Different phase d) None of the above

18. The effects of small scale propagation are [ ] a) Changes in signal strength b) Random frequency modulation c) Time dispersion d) All of the above

19. Impulse response of a multipath channel is determined by the fact that [ ] a) Mobile radio channel may be modeled as linear filter b) Impulse response is time varying c) Both a) and b) d) None of the above

20. The received signal from a multipath channel is expressed as [ ] a) convolution of transmitted signal and impulse response b) Addition of transmitted signal and impulse response c) Subtraction of transmitted signal and impulse response d) None of the above

21. Direct RF pulse system helps in calculating [ ] a) Impulse response in frequency domain b) impulse response in phase domain c) Power delay of the channel d) all of the above

22. The techniques used for small scale multipath measurements are [ ] a) Direct RF pulse system b) Spread spectrum sliding correlator channel sounding c) Frequency domain channel sounding d) All

23. The power delay profile helps in determining [ ] a) Excess delay b) rms delay spread c) excess delay spread d) all of the above

24. Coherence Bandwidth is [ ] a) channel that passes all spectral components with equal gain b) The bandwidth of modulated signal c) Channel that passes all spectral components with linear phase d) Both a) and c)

25. Types of small scaling based on Doppler spread are [ ] a) Fast fading b) Frequency non selective fading c) Flat fading d) Frequency selective fading

26. Flat fading or frequency non selective fading is a type of [ ] a) Multipath delay spread small scale fading b) Doppler spread small scale fading c) Both a) and b) d) None of the above

27. In frequency selective fading, the [ ] a) Coherence Bandwidth of the channel is less than bandwidth of transmitted channel b) Coherence Bandwidth of the channel is more than bandwidth of transmitted channel c) Coherence Bandwidth of the channel is equal to bandwidth of transmitted channel d) None of these

28. If coherence time of the channel is smaller than the symbol period of the transmitted signal, it [ ] a) Fast fading b) Slow fading c) Frequency selective fading d) Frequency non selective fading

29. The purpose of a Repeater is [ ] a) To amplify b) to attenuate c) to reradiate d) to store

30. The natural phenomenon caused by reflected and scattered propagation paths is [ ] a) Fading b) scattering c) delay spread d) reflection

31. The parameters that describe the time varying nature of the channel in the small scale region [ ] a) Doppler spread, Coherence time b) Doppler spread, mean excess delay c) Coherence time & mean excess delay d) Doppler spread & Bandwidth

32. The angle at which no reflection occurs in the medium of origin is called [ ] a) Acute angle b) Brewster angle c) Triangle d) None

33. The multipath channel parameters that can be determined from a power delay profile are [ ] a) Mean excess delay b) rms delay spread c) excess delay spread d) All

34. The phenomenon of Diffraction is explained by _____________ [ ] a) Huygens principle b) Albert’s principle c) Friis space equation d) None

35. The small scale variations of a mobile radio signal can be directly related to the ______ of the mobile radio channel. [ ]

a) Step response b) Impulse response c) Rayleigh distribution d) None 36. Processing Gain, PG is given by [ ]

a) 2Rc/Rbb b) 2Tbb/Tc c) 2Rc/2Tbb d) Both a and b 37. Doppler spread, BD is given by [ ]

a) Vfc/C b) VC/fc c) VTc/2 d) None 38. _____________ is used to characterize the channel in the frequency domain [ ]

a) Bandwidth b) Delay spread c) Coherence Bandwidth d) None 39. A signal undergoes Slow fading if [ ]

a) Ts<<Tc & Bs>> Bd b) Ts==Tc & Bs>> Bd c) Ts<<Tc & Bs== Bd d) Ts>>Tc & Bs<< Bd

40. A signal undergoes frequency selective fading if [ ] a) Bs>Bc & Ts<στ b) Bs=Bc & Ts<στ c) Bs>Bc & Ts=στ d) Bs<Bc & Ts<στ

UNIT-II

MOBILE RADIO PROPAGATION

2-MARKS QUESTIONS

1. What is propagation model? 2. Define large scale propagation model? 3. What is small scale model? 4. What is free space propagation model? 5. Define EIRP. 6. Explain path loss? 7. What is intrinsic impedance& Brewster angle? 8. Define scattering and Diffraction? 9. Define radar cross section? 10. Name some of the outdoor propagation models? 11. Write the equations of Link power budget? 12. Define indoor propagation models? 13. Mention some indoor propagation models? 14. Explain small scale fading? 15. What are the factors influencing small scale fading? 16. Define Doppler shift? 17. What flat fading? 18. What is frequency selective fading? 19. Define fast fading channel? 20. Define slow fading channel?

UNIT-II

MOBILE RADIO PROPAGATION

10-MARK QUESTIONS

1) a) Explain the free space propagation model?

b) Explain three different propagation mechanisms.

2) a) What is reflection? Explain in detail the reflection from dielectric and conductors.

b) Write short notes on diffraction and scattering.

3) a) Explain in detail the indoor & outdoor propagation model.

b) Write short notes on small scale fading.

4) a) Explain in detail the small scale multipath propagation and its different Measurements.

b) Explain Rayleigh & Ricean distributions.

5) a) Explain the terms

i) Fresnel Zone geometry ii) Knife edge diffraction model

b) Explain Radar cross section model.

6). Give the basic classification of Small Scale fading and explain the types of small scale fading based on multipath time delay spread.

7).a) Explain fading effects due to Doppler spread.

b) Explain Flat fading and frequency selective fading.

8). a) Explain statistical models of radio propagation.

b) Give the simulation methods of these models.

9). If a transmitter produces 50W of power, express the transmit power in units of (a) dBm and

dBW. If 50W is applied to a unity gain antenna with a 900MHz carrier frequency, find the

received power in dBm at a free space distance of 100m from the antenna. What is Pr (10Km)?

Assume unity gain for the receiver antenna.

10. a) Find the far-field distance for an antenna with maximum dimension of 1m and operating

frequency of 900MHz.

b) Explain the Two ray reflection model and derive the expression for free space received power.

UNIT-III EQUALIZERS AND DIVERSITY TECHNIQUES

MULTIPLE CHOICE QUESTIONS 1) ISI Refers [ ]

a) Intermodal System Interference b)Intramodal System Interference

c) Inter symbol Interference d) Inter System Interference

2) Channel coding improves the small-scale link performance by adding [ ]

a) Result data bits b) Input data bits c) Output data bits d) redundant data bits

3) How many types of channel Codes [ ]

a) 2 b) 3 c) 4 d) 5 4) In equalization f* (t) denotes [ ]

a) Conjugate of f(t) b)Fourier transform of f(t)

c) Laplace Transform of f(t) d) Complex Conjugate of f(t)

5) The output of the equalizer d^ (t) is [ ]

a)X(n) + nb(n) heq (n) b) X(n) g(n) + nb(n) heq (n)

c) X(n) + nb(n) d) X(n) + nb(n) heq (n)

6) In a communication Receiver equalizers have prediction error as [ ]

a) e(n) = d(n) – [ x(n) + nb(n) heq (n) ] b) e(n) = d(n) – [ x(n) g(n) + heq (n) ]

c) e(n) = d(n) – [x(n) g(n)+ nb(n) heq (n) ] d) e(n) = d(n) – [ g(n) + heq (n) ]

7) In survey of Equalization LTE denotes [ ]

a) Linear time Equalizer b) Linear transversal Equalizer

c) Life time Equalizer d) Linear tapped Equalizer

8) The mean squared Error in a Communication Receiver denotes as [ ]

a) E [ │e(n)│2] b) E [ │e(n)│] c) E [ │e(n)│4] d) √ (e(n)).

9) In a linear Equalizer C n* denotes [ ]

a) Coefficient of filter b) Constant

c) Complex filter coefficient d) Complex conjugate coefficient

10) In a linear Equalizer F ( ejωT) denotes [ ]

a) Frequency of input b) Channel response frequency

c) Complex frequency d) Instantaneous frequency.

11) How many nonlinear methods used in 2G and 3G systems? [ ]

a) 4 b) 3 c) 2 d) 5.

12) What is rate of Convergence in Algorithm of Adaptive Equalization [ ]

a) Number of Constants required for the algorithm

b) Number of Redundant required for the algorithm

c) Number of iterations required for the algorithm

d) Number of Calculations required for the algorithm.

13) In LMS Algorithm ‘ α ‘ denotes [ ]

a) Constant b) Input value c) output value d) Step size

14) In DFE what denotes ‘FFF’ [ ]

a) Fast forward filter b) finite forward filter c) feed forward filter d) frequency forward filter. 15) In LMS Gradient DFE the number of multiply operations is [ ]

a)N+1 b) 2N+1 c) N – 1 d) 2N-1

16) In Kalman RLS the number of multiply operations is [ ]

a) 2 N2 + 4N b) 4N2 + 4N c) 2 N2 + 4.5 N d) 2.5 N2 + 4.5N

17) In RLS the Wn* denotes [ ]

a) Gain vector b) Constant c) optimal vector d) Optimal tap gain vector.

18) A Fractionally spaced equalizer is based on [ ] a) Sampling of incoming signal by Nyquist rate b)Sampling of incoming signal by bit rate

c) Incoming signal with rate d) output rate.

19) What is ‘Г ‘in the Diversity Techniques [ ]

a)Constant b) Vector c) mean SNR of each branch d) output rate

20) In diversity techniques the ‘ γM’ is given by [ ]

a)γM = rM / 2 NT b) γM = rM 2 / 2 NT c) γM = rM 2 / NT d) γM = rM 4 / 2 NT .

21) In polarization Diversity the average value of signal loss ‘L’ [ ]

a)L = ( a/ x +b) b) L = ( a2/ x +b) c) L = ( a/ x2 +b) d) L = ( a2/ x +b2)

22) In a RAKE receiver the range of delays that a particular correlator can search is called [ ]

a)Output window b) Input window c) Search window d) opening window

23) In a RAKE receiver the overall gain Z1 is given by [ ]

a) Z1 = m=1ΣM αm b) Z1 = m=1Σ

M αm Zm c) Z1 = m=1ΣM Zm d) Z1 = m=1Σ

M αm / Zm.

24) In Maximal Ratio Combining the signals from all of the M branches are weighted according to[ ]

a)Combined Signal voltage to noise power ratio b)Individual signal voltage to noise power

c) Partial Signal voltage to noise power ratio d) none of the above.

25) Maximal Ratio Combining produces [ ]

a)Output SNR = Sum of combining SNR’s b)Input SNR = Sum of Individual SNR’s

c) Output SNR = Sum of individual SNR’s d) Input SNR = Sum of combining SNR’s

26) In Maximal Ratio Combiner the detector having input as [ ]

a) Zm b) αm c) γM d) Gm

27) Maximal Ratio Combiner gives [ ]

a) Best statically reduction of fading any known linear diversity Combiner

b) Best statically reduction of fading any unknown linear diversity Combiner

c) Best statically reduction of fading any known nonlinear diversity Combiner

d) Best statically reduction of fading any unknown nonlinear diversity Combiner

28) The equal Gain Combining [ ]

a) The signals are one by one received on each branch.

b) The signals are simultaneously received on each branch.

c) The signals are combined received on each branch.

d) The signals are individually received on each branch.

29) In equal Gain Combining the branch weights are all set to [ ]

a) α b) 0 c) ½ d) unity.

30) In a RAKE receiver the αm denotes [ ]

a) αm = Zm2 / m=1ΣM Zm2 b) αm = Zm / m=1Σ

M Zm2 c) αm = Zm d) αm = Zm2

31) The total noise power NT is given by [ ]

a)NT = N i=1ΣM Gi2 b) NT = i=1Σ

M Gi2 c) NT = N Gi2 d) NT = i=1ΣM Gi

32) In RLS the ‘λ’ denotes [ ]

a)Coefficient b) constant c) wavelength of signal d) coefficient of weighting

33) In Switching Diversity Method it is applicable in to [ ]

a)DPSK b) BPSK c) PSK d) QPSK

34) Which type of Oscillator in Switching Diversity Method? [ ]

a) Colpitt’s Oscillator b) Bridge Oscillator c) Hartely Oscillator d) free-running Oscillator

35) By Switching Diversity Method it is applicable in to [ ]

a)DPSK b) BPSK c) PSK d) QPSK

36) For VHF, UHF and microwave/mobile radio applications which diversity is not suitable? [ ]

a)Maximal-ratio b) Equal-gain c) both a and b d) Switching Method.

37) In low-speed, large-deviation digital FM which method is used. [ ]

a)Switching Diversity b) Maximal-ratio c) Equal-gain d) both a and b

38) Most frequently used diversity technique in wireless communication systems. [ ]

a)Maximal-ratio b) Switching or Selection c) Equal-gain d) Polarization diversity

39) Which diversity is simple and economically implemented in cheap? [ ]

a)Polarization-diversity b) Maximal-ratio c) Space diversity d) Equal-gain

40) Space- diversity reception methods can be classified in to how many categories? [ ]

a)2 b) 3 c) 4 d) 5

UNIT-III EQUALIZERS AND DIVERSITY TECHNIQUES

2 marks Questions 1) Define adaptive equalization

2) Define training mode in an adaptive equalizer

3) What is tracking mode in an adaptive equalizer

4) Write short notes on linear equalizers and non- linear equalizers

5) Why non-linear equalizers are preferred

6) What are the non-linear equalization methods are used.

7) What are the factors used in adaptive algorithms.

8) Define MSE in equalizers.

9) Write the advantages of LMS algorithm.

10) What are the advantages of RLS algorithm?

11) Define Diversity concept?

12) Define Spatial Diversity?

13) What is diversity?

14) What is the need of equalization?

15) What are the techniques used to improve received signal quality?

16) Give some examples of linear modulation.

17) What is zero forcing algorithm?

18) What is Recursive Least Squares Algorithm?

19) Write about disadvantages of Fast Kalman DFE.

20) Define Rate of convergence.

UNIT-III EQUALIZERS AND DIVERSITY TECHNIQUES

10 Mark Questions

1) Explain in detail about Linear Equalizers of the following with neat diagram.

a) Linear Transversal Equalizer b) Lattice Equalizer

2) What is Non – Linear Equalizer? Explain in detail of the following.

a) Decision Feedback Equalization (DFE) b) Maximum Likelihood Symbol Detection

3) Draw and explain about Maximum Likelihood Sequence Estimation (MLSE) in detail.

4) Write about Survey of Equalization Techniques in detail.

5) What is Algorithm for Adaptive Equalization? Explain of the Following in detail.

a) Least Mean Square Algorithm (LMS) b) Recursive Least Squares Algorithm (RLS).

6) What is RAKE Receiver explain it with diagram in detail.

7) Explain about the following diversity techniques in detail.

a) Maximal ratio Combiner b) Scanning Diversity

8) Find the Derivation of Maximal Ratio Combining Improvement.

9) Consider the design of the U.S Digital Cellular Equalizer. If the carrier frequency is 900 MHz and the

maximum Doppler shift is 66.67 Hz.

a) Calculate the maximum mobile velocity for the given Doppler Shift.

b) Calculate the coherence time of the channel.

c) Find the Doppler Spread.

d) Assume that the symbol rate is 24.3 k symbols/sec; calculate the maximum number of symbols that

can be transmitted without updating the equalizer.

e) Assume that there are 5 delay elements in an equalizer and there are 10 μs delay in each; calculate

the maximum number of taps.

f) Calculate the maximum multipath delay spread that could be equalized.

10) Find the Derivation of Selection Diversity Improvement.

UNIT-IV MULTIPLE ACCESS TECHNIQUES AND NETWORKING

OBJECTIVE QUESTIONS

1. The type of access used in GSM technology is [ ] a) TDMA b) CDMA c) FDMA/TDMA d) OFDMA

2. The accessing technique that shares the bandwidth in Time is [ ] a) TDMA b) CDMA c) FDMA/TDMA d) OFDMA

3. ATM is a ______________ technique [ ] (a) Synchronous (b) multiplexing (c) demultiplexing (d) none

4. ATM stands for [ ] a) Asynchronous transfer mode b) Asynchronous timing mode c) Automated transfer mode d) none

5. An example of shared mobile data network is [ ] a) ARDIS b) CDPD c) SS7 d) none

6. Radio LAN operates in [ ] a)8.89Ghz b) 5.89Ghz c) 6.7Ghz d) 9.1Ghz

7. LAN that operates at ISM band is [ ] a) SSLAN b) CSLAN c) SILAN d) ISLAN

8. FCS stands for [ ] a) Frame cyclic sequence b) frame check series c) Frame check sequence d) frame cyclic series

9. SSAP contains ___________ number of bits [ ] a) 7 b) 3 c) 4 d) 8

10. STA services consist of ______________ [ ] a) Privacy b) authentication c) deauthentication d) all

11. Typical coverage area of wireless LAN has a diameter of [ ] a) 30-40m b) 60-70m c) 100-300m d) 100-150m

12. IR data transmission uses ________ modulation [ ] a) Intensity b) amplitude c) frequency d) phase

13. Direct sequence spread spectrum (DSSS) is allocated as_____ [ ] a)FDMA b) TDMA c) CDMA (d) SDMA

14. SDP stands for [ ] a) Source discovery protocol b) source data protocol c) Service data protocol d) service discovery protocol

15. The lowest defined layer of Bluetooth specification is [ ] a)Base band b) Bluetooth radio c) RF COMM d) none

16. Wireless LAN operates at [ ] a) Physical layer b) network layer c) Data link layer d) Physical layer & Data link layer

17. Wireless LAN uses which protocol….. [ ] a)IEEE 802.11 b) IEEE 802.1.1 c) IEEE 802 d) IEEE 802.1.1.3

18 .LAN protocol architecture consists of how many layers [ ] a) 3 b) 4 c) 5 d) 6

19. If I/G= 0 [ ] a) Individual b) group c) interfacing d) gateway

20. The combination of both DSAP & SSAP values forms [ ] a) LLC field b) MAC control c) I/G d) CRC 21. The sequences are generated using orthogonal codes such as Walsh tables are [ ] a)TDMA b) CDMA c) FDMA d) TDMA . 22. The duplexing that provides two distinct bands of frequencies is [ ]

a) FDD b) SDMA c) FDMA d) TDMA 23. TDMA is a multiple access technique that has [ ]

a) Different users in different time slots b) Each user is assigned unique frequency slots c) Each user is assigned a unique code sequence d) Each signal is modulated with frequency modulation technique

24. In TDMA, the user occupies the __________ bandwidth during transmission. [ ] a) Whole b) half c) 3/4 d) none

25. TDMA allows the user to have [ ] a) Use of same frequency channel for same time slot b) Use of same frequency channel for different time slot c) Use of same time slot for different frequency channel d) Use of different time slot for different frequency channels

26. GSM is an example of [ ] a) TDMA cellular systems b) FDMA cellular systems c) CDMA cellular systems d) SDMA cellular systems

27. TDMA is employed with a TDMA frame that has preamble. The preamble contains Address of base station and subscribers [ ] a) Synchronization information b) Frequency allotted c) Coded sequence d) ESN

28. CDMA is [ ] a) Spread spectrum technology b) Using same communication medium c) Every user stays at a certain narrowband channel at a specific time period d) Each user has unique PN code

29. Global Positioning System uses [ ] a) CDMA b) TDMA c) SDMA d) FDMA

30. CDMA is advantageous over other Spread Spectrum techniques for [ ] a) The privacy due to unique codes b) It rejects narrows band interference c) Resistance to multi path fading d) Its ability to frequency reuse

31. The wide band usage in CDMA helps in [ ] a) Increased immunity to interference b) Increased immunity to jamming c) Multiple user access d) Different spectrum allocation in different time slots

32. The advantages of using a CDMA technique over other spread spectrum techniques are [ ] a) Increased capacity b) Easier handoff c) Better measure of security d) multiple users occupy different spectrum at a time

33. FHMA is [ ] a) Spread spectrum technology b) Using same communication medium c) Every user has assigned unique frequency slot d) each user has unique PN code

34. Packet radio refers to [ ] a) Multiple users on single channel b) Single user on multiple channels as per demand c) Multiple users on multiple channels at different time slots d) Multiple users with coding techniques

35. Disadvantages of packet radio are [ ] a) Induced delays b) Low spectral efficiency c) Large spectrum required d) Both a) and b)

36. Pure ALOHA is a [ ] a) Random access protocol b) Scheduled access protocol c) Hybrid access protocol d) Demand access protocol

37. The increase in number of users in PURE ALOHA causes [ ] a) Increase in delay b) Increase in probability of collision c) Increase in spectrum d) Both a) and b)

38. SDMA technique employs [ ] a) Smart antenna technology b) Use of spatial locations of mobile units within the cell c) More battery consumption d) both a) and b) are correct

39. The advantage of using SDMA over other spread spectrum technique is [ ] a) Mobile station battery consumption is low b) Reduced spectral efficiency c) Increased spectral efficiency d) both a) and b) are correct

40. The increased capacity of SDMA due to [ ] a) Focused signal transmitted into narrow transmission beams b) Smart antennas pointing towards mobile stations c) Use of different frequencies at same time slot d) Both a) and b) are correct

2MARKS QUESTIONS

1. List the uses of multiple access techniques.

2. Expand CDMA, FDMA, TDMA and SDMA.

3. Draw the figure depicting the basic concept of FDMA.

4. Draw the figure depicting the basic concept of TDMA.

5. Mention the types of Spread spectrum multiple access techniques.

6. Define Packet Radio.

7. Write some features of TDMA.

8. What is CDMA digital cellar standard?

9. What are the disadvantages of FDMA?

10. List the disadvantages of FDMA.

11. Give the differences between Wireless and Fixed Telephone networks.

12. What are the types of Random Access methods?

13. Give the schematic of SS7 protocol architecture.

14. What are the QOS in wireless networks?

15. What are the limitations in wireless networking?

16. Mention the types of routing services provided by networks. 17. Name the data only mobile services developed to provide packet radio connectivity through a network.

18. Define Common channel signaling.

19. Give the differences between circuit and packet switching.

20. Define PSTN and PBX.

10 MARK QUESTIONS

1. a) Explain in detail the TDMA & FDMA multiple access techniques.

b) Explain fixed network Transmission hierarchy in detail?

2. a) Explain in detail the CDMA multiple access technique.

b) Explain the CDMA working principle.

3. Compare the performance of TDMA, FDMA, CDMA, SDMA techniques.

4. a) What is Spread spectrum multiple access and explain its types.

b) Explain TDMA frame structure and its efficiency.

5. a) Define FDMA and also describe its various features?

b) List the different types of CSMA protocols?

6. a) Discuss about public switch telephone network.

b) Explain signaling traffic in SS7?

7. a) Explain the techniques of traffic routing in wireless networks..

b) Explain the various generations of wireless networks?

8. a) Describe Packet switching with neat diagram?

b) Describe various processes like registration tunneling?

9. a) Explain the mobile IP operation?

b) Explain CDPD and ARDIS in detail?

10 a) Explain in detail the development of wireless networks.

b) Write the difference between the wired and wireless telephone networks?

UNIT-V

MULTICARRIER MODULATION

MULTIPLE CHOICE QUESTIONS 1) In Data transmission using Multiple Carriers the number of stream is chosen to make symbol time on

each sub stream much------------------- the delay spread of the channel. [ ] a)Equals b) Less than c) Greater than d) 0

2) In multicarrier transmitter the data rate for each with Sub channel [ ] a)RN = N/R b) RN = R N c) RN = N + R d) RN = R/N

3) In multicarrier transmitter the bit stream is divided in N Sub stream via [ ] a)Parallel to Serial Converter b)Serial to Parallel Converter c) Both a and b d) None of the above

4) In transmitted signal s(t) = I = 0ΣN-1 Si g(t) Cos (2πfit + φ i) ‘ Si ‘denotes [ ]

a) Constant b) Symbol c) Complex Symbol d) Complex conjugate 5) The channel gain ‘αi’ = ----------------- [ ]

a)αi = |H (fi )| b) αi = H (fi ) c) αi = |H (f (t))| d) αi = H f (t) 6) Total required bandwidth for non-overlapping sub channels is [ ]

a)B = N ( 1-β-e)/ TN b) B = N ( 1+β+e)/ TN c) B = N ( 1+β+e) TN d) B = N TN 7) The total system bandwidth with overlapping Sub channels is [ ]

a)B = TN b) B = TN / N c) B = TN* N d) B = N / TN 8) In multicarrier system β denotes [ ]

a) Multiple factor b) Constant c) roll off factor d) null factor 9) The received SNR is γi = ------------------ [ ]

a)γi = αi PI /N0 BN b) γi = αi 2 PI /N0 BN c) γi = αi PI /N0 d) γi = αi 2 PI /N0 10) In frequency Equalization the flat fading (αi) on the ith sub channel is basically ----------------. [ ]

a) Multiplied b) Converted c) Inverted d) Cancel 11) In frequency equalization the resultant signal power is [ ]

a)Pi b) Pi2 c) Pi +1 d) Pi <1 12) The N-point DFT of X [n] is defined as [ ]

a)DFT {X[n] }= x[i] Δ1/(√N) X[n] e (2πni)/ N b) DFT {X[n] } = x[i] Δ 1/(N) X[n] e (2π)/ N c) DFT{X[n]} = x[i] Δ1/ (N2) X[n] e (2πN)/ni d) DFT{X[n] } = x[i] Δ(√N) X[n] e(2πni)/ N

13) The y [n] of Discrete Time Convolution of the input of the channel impulse response is [ ] a)y [n] = k Σ h[k] b)y [n] = k Σ h[k]X[k] c)y [n] = k Σ h[k] X[n-k] d) y[n] = k Σ X [n-k]

14) The N-point circular Convolution of X[n] and h[n] is defined as [ ] a)y [n] = k Σ h[k] X [n-k] N b) y [n] = k Σ h[k] X [n-k] c) y [n] = k Σ X [n-k] d) y [n] = k Σ h[k]

15) In a Cyclic Prefix the DT channel length μ +1 = [ ] a) TM b) TM TS c) TM + TS d) TM /TS

16) In a Cyclic Prefix rate of reduction [ ] a) N/ μ +N b) N( μ +N) c) N( μ N) d) μ N

17) In OFDM the input data _______in to blocks of size N refers to as an OFDM symbol [ ] a) Multiplied b) added c) divided d) Subtracted

18) A cyclic prefix ____to each OFDM Symbol to induce circular Convolution of the input and channel impulse response [ ] a) Multiplied b) added c) divided d) Subtracted

19) What is the benefit of Cyclic Prefix [ ] a) Reduction of Size b) accurate c) Cost d) fast result.

20) In OFDM Transmitter_____________converter is used at input section [ ] a) Parallel to Serial b) Serial to Parallel c) Digital to Analog d) Analog to Digital

21) In OFDM receiver _______________ converter is used at input section [ ] a) Parallel to Serial b) Serial to Parallel c) Digital to Analog d) Analog to Digital

22) In receiver of OFDM the ________________type of demodulation is done [ ] a) QAM b) PAM c) PCM d) PTM

23) For Continuous Time OFDM the frequency equalization having noise is scale by [ ] a) H (i) b) 1+ H (i) c) 1/ H (i) d) 1- H (i)

24) In Matrix Representation of OFDM the V[n] denotes [ ] a) Input b) output c) noise d) result of matrix

25) What is the matrix form of OFDM [ ] a) Y = Hx- V b) Y = Hx/V c) Y = Hx d) Y = Hx+ V

26) In Matrix Representation of OFDM ‘A’ denotes [ ] a) Matrix of Eigen values of H҃ b) Diagonal matrix of Eigen values of H҃ c) Eigen values of H҃ d) values of H҃

27) The DFF operation of x[n] can be represented by the matrix multiplication [ ] a) Y = Qx b) Y = Q/x c) X = Qx d) X = Q/x

28) If ‘V’ eigenvector of H’ and λ is Eigen value then [ ] a) λ = H b) λ V= H c) λ = H V d) λ V= H V

29) The Singular value of decomposition of ‘H’ can be written as [ ] a) H = Σ VH b) H =U Σ VH c) H = U d) H = U Σ V

30) In vector coding the filter transmitted vector is [ ] a) X = V b) X = V+1 c) x= V X d) x= V +X

31) In vector coding the filter received vector is [ ] a) Y = UH y b) Y = UH-1 y c) Y = UH + y d) Y = UH - y

32) In vector coding ‘H ‘ is obtained by appending ‘μ’ extra symbols to each block of N data symbols

these are called_______________ [ ] a) Vectors b) Multiple vectors c) Vector code words d) Code words.

33) The complexity of finding the SVD of the N X (N + μ) matrix H ________with N [ ] a) Decreases b) Increases c) Multiplied d) divided

34) In H = U Σ VH ‘Σ’ denotes [ ] a) Diagonal Matrix b) Matrix c) Value of Matrix d) Addition

35) The data rate of Adaptive loading [ ] a)R = BN b) R = BN ii γi <γkΣ log (γi) c)R = BN ii γi >γkΣ log (γi/ γk) d) R = BN + 1

36) In Adaptive loading the ‘γk’ denotes [ ] a) Cutoff fade length b) constant c) multiplier d) Cutoff value

37) The capacity for Adaptive loading [ ] a)C = ii γi >γ0Σ BN b)C = ii γi > γ0Σ BN log (γi) c) C = iiΣBN log(γi/γ0) d) C= ii γi >γ0Σ BN

38) The X[n] for Known h[n] is Cyclic Prefix is [ ] a) X[n] = IDFT {Y(I) } b)X[n] = IDFT { Y(I)/ H [I] } c) X[n] = DFT {Y(I) } d) X[n] = DFT { Y(I)/ H [I] }

39) The ISI is eliminated by this condition in data transmission [ ] a) BN = BC b) BN >> BC c) BN << BC d) BN >BC

40) The symbol time ‘TN’ in data transmission [ ] a) TN = (1+ β) BN b) TN = (1+ β)/ BN c) TN = β BN d) TN = β/BN

UNIT-V MULTICARRIER MODULATION

2MARKS QUESTIONS

1. Explain the principle involved in OFDM?

2. What is meant by guard time and cyclic extension in OFDM?

3. State the need for scrambling in OFDM

4. Define the term IFFT?

5. What are the advantages and disadvantages of OFDM?

6. What are the properties of MIMO channel matrix?

7. Illustrate the term guard time.

8. Examine the need of Scrambling in OFDM?

9. Analyze how the clipping is done in OFDM.

10. Apply the concept of filtering in OFDM.

11. Summarize delay spread?

12. Assess the significance of scrambling?

14. Analyze the difference between OFDM and OFDMA?

15. Develop the peak to average power ratio for OFDM signals.

16. Illustrate the disadvantages of multicarrier OFDM modulation system?

17. What is the purpose of cyclic prefix in OFDM?

18. Formulate the need for PPP?

19. Evaluate the performance of OFDMA?

20. Give the concept of multicarrier transmission technique?

UNIT-V MULTICARRIER MODULATION

10 MARKS QUESTIONS

1. a) Explain the concept of data transmission using multiple carriers.

b) Illustrate how OFDM concept is emerged in multicarrier modulation technique.

2. a) Develop the concept of multicarrier modulation techniques in OFDM with suitable diagrams.

b) Consider a multicarrier system with TN = 0.2 ms: TN>> Tm for Tm the channel delay spread, so

each sub-channel experiences minimal ISI. Assume the system has N=128 sub channels. If raised

cosine pulses with β=1 are used, and the additional bandwidth due to time limiting required to

insure minimal power outside the signal bandwidth is ϵ/TN =0.1, then what is the total bandwidth of

the system.

3. i) What is a DFT and give its properties?

ii) Explain the concept of Cyclic Prefix.

4. i) Explain about the parameters required for OFDM system design.

ii) Draw the block diagram of OFDM transmitter and receiver. Explain them in detail.

5. Discuss PAP reduction schemes with a neat diagram and explain its application.

6. Explain in detail of any two methods to reduce peak-to-average power ratio in multicarrier OFD

system.

7. a) Discuss the generation of subcarriers using the IFFT with a neat diagram.

b) What is Vector Coding?

8. Write about the following in detail.

1. Guard time.

2. Cyclic extension

3. Windowing

4. Clipping in OFDM system

9. a) Explain the challenges in Multicarrier systems.

b) Draw the block diagram of a multicarrier OFDM digital communication.

10. Write short note on

i) Clipping iii) Discuss in detail about peak power problem in OFDM. iii) Filtering