Digital and Wireless Communication mcq

 

1. The unit of average mutual information is

a)Bits

b) Bytes

c) Bits per symbol

d) Bytes per symbol

2. The method of converting a word to stream of bits is called as

a) Binary coding 

b) Source coding

c) Bit coding 

d) Cipher coding

3 When the base of the logarithm is 2, then the unit of measure of information is

a) Bits 

b) Bytes

c) Nats 

d) Hertz

4 The channel capacity is

a. The maximum information transmitted by one symbol over the channel

b. Information contained in a signal

c. The amplitude of the modulated signal

d. All of the above

5. According to Shannon Hartley theorem,

a. The channel capacity becomes infinite with infinite bandwidth

b. The channel capacity does not become infinite with infinite bandwidth

c. Has a tradeoff between bandwidth and Signal to noise ratio

d. Both b and c are correct

6. Information rate is defined as

a. Information per unit time 

b. Average number of bits of information per second

c. rH 

d. All of the above

7. Entropy is

a. Average information per message 

b. Information in a signal

c. Amplitude of signal 

d. All of the above

8. The information I contained in a message with probability of occurrence is given by (k is constant)

a. I = k log21/P 

b. I = k log2P

c. I = k log21/2P 

d. I = k log21/P2

9. A discrete source emits one of 5 symbols once every scond. The symbol Probabilities are ½,1/4,1/8,1/16,1/16 respectively. What is the source entropy near to.

a. 1.875 bits/symbol

b. !.875 bits

c. 1.895 symbol

d. None

10. Out of following which is not Block of Digital Communication System

a) Source Encoder

b) Channel Encoder

c) Modulator

d) Sequence Amplifier

11. How amount of Information is get Calculated in bits

a) log21/P 

b) log21/P2

c) log21/P2

d) None from Above

12. Select correct entropy for the source that emits one of three possible symbols A,B and C in a statistically independent sequence with probabilities ½,1/4,1/4.

a) 1.5 bits/Symbol

b) 2.8 bits

c) 15 bytes

d) 15 bytes /sym

13. The technique that may be used to increase average information per bit is

a. Shannon-Fano algorithm 

b. ASK

c. FSK 

d. Digital modulation techniques

14.  Which is the correct expression for code efficiency in terms of entropy.

a) Code efficiency = Average code word length(N)/Entropy(H) 

b) Code efficiency = Entropy(H) / 2*Average code word length(N)

c) Code efficiency = Entropy(H) / Average code word length(N)

d) None from Above

15.  What is correct formula to calculate information rate.

a) R = r H bits / sec b) R=sI bits

c) R= sH

d) H=sR

16.  For Shannon FANO coding scheme which of following steps is correct: Step 1: List the source symbols in order of decreasing probability. Step 2: Partition the set into two sets that are as close to equiprobable as possible, and sign 0 to the upper set and 1 to the lower set. Step: Continue this process, each time partitioning the sets with as nearly equal probabilities as possible until further partitioning is not possible.

a) Only 1

b) Only 2

c) Both 1 and 2

d) All are correct

17. In which block of Digital Communication system coding is performed

a) Discrete Information source

b) Source Decoder

c) Channel Encoder

d) Modulator

18. Select proper unit for Joint Entropy of Source

a) Bits/Sequence

b) Bits/Symbol

c) bits

d) None of above

19. The probability of occurance of various letters of the English alphabet are given below. A=0.081 B=0.016 C=0.032 D=0.037 E=0.124 F=0.023 G=0.016 H=0.051 I=0.072 J=0.001 K=0.005 L=0.040 M=0.022 N=0.072 O=0.079 P=0.023 Q=0.002 R=0.060 S=0.066 T=0.096 U=0.031 V=0.009 W=0.020 X=0.002 Y=0.019 Z=0.001

Which Element Carries less amount of Information.

a) A

b) T

c) E

d) Q

20. A source of Information A generates the symbols {a1,a2,a3,a4,a5} with probabilities [0.4, 0.3, 0.15, 0.10, 0.05] respectively.what will be entropy for above source

a) H ≈ 1.5370 bits/symbol

b) H ≈ 2.0087 bits/symbol

c) H ≈ 1.2560 bits/symbol

d) H ≈ none of above

31. Which among the following represents the flawless hand-off with no perceivable interruption of service?

A)Hard hand-off   

B)Soft hand-off

C) Intracell hand-off             

 D)Intercell hand-off

32.Which method of cellular network assists in minimizing the co-channel interference associated with the angle of degree?

A) Cell Splitting       

B) Cell Segmentation & Dualization

C) Cell Sectoring     

D) Handoff

                               

33. What is frequency reuse?

A)Process of selecting and allocating channels         

B)Process of selection of mobile users

C) Process of selecting frequency of mobile equipment        

D)Process of selection of number of cells

34.  In a cellular telephone system, which type of interference results from imperfect design of filters in receivers by allowing nearby frequencies to enter the receiver?

A) Co-channel Interference               

B)Adjacent-channel Interference

C) Equivance Interference 

D))None of the above

               

35. Which of the following is a universally adopted shape of cell?

A)Square  

B)Circle

C)Triangle               

D)Hexagon

               

36. If the system is designed with the usage of hexagonal-shaped cells, how are the base-stations located?

A) At the corner of the cell               

B)  At the edge of cell

C)  At the centre of cell        

D)  All of the above

                               

37. Why the shape of cell is not circle?

A)Overlapping regions or gaps are left         

B)Omni directionality

C)Complex design 

D)Small area

               

38. For a cellular system, if there are N cells and each cell is allocated k channel. What is the total number of available radio channels, S?

A) S=k*N   

B)S=k/N

C)S=N/k   

D)S=kN

                               

39.What is a cluster in a cellular system?

A) Group of frequencies     

B)Group of cells

C)Group of subscribers      

D)Group of mobile systems

                               

40. The spectrum of 30 M Hz Bandwidth divided into 50 KHz/duplex channels compute number of channel available per cell for 7 cell reuse

A)150 Channels/cell            

B)85 channels /cell

C)120 Channels/cell            

D)150 channels /cell

                               

41. What is the responsibility of MSC in cellular telephone system?

A)Connection of mobile to base stations    

B)Connection of mobile to PSTN

C)Connection of base station to PSTN          

D)Connection of base station to MSC

                               

42.Who has the responsibility of billing and system maintenance function in cellular system?

A)Base Station       

B)PSTN

C)MSC       

D)Mobile system

                               

43. What is handoff?

A)Forward channel              

B)Switching technique

C)Roamer 

D)Guard channel

               

44. Which one is not an advantage of using frequency reuse?

A)Increased capacity           

B)Limited spectrum is required

C)Same spectrum may be allocated to other network          

D)Number of base stations is reduced

               

45. The interference between the neighbouring base stations is avoided by ____________

A)Assigning different group of channels      

B)Using transmitters with different power level

C)Using different antennas              

D)Using different base stations

               

46 . Roaming is feature of

A) Cellular Telephony          

B) Cellular End Caller

C) Cellular Signal    

D) Cellular Feature

               

47. In____________________ of cells we divide a group of channels into smaller groupings

A)Segmentation   

B)Dualization

C)Handoff               

D)Roaming

                               

48. It is the process of subdividing a congested cell into smaller cells,

A)Dualization          

B)Cell Splitting

C)Segmentation   

D)Cell Sectoring

                               

49. It is a method to increase capacity is to keep the cell radius unchanged and seek methods to decrease D/R ratio.

A)Handoff               

B)Cell

C)Sectoring            

D)Dualization

                               

50. The Authentication Centre (AUC) provides authentication and encryption parameters that verify the user's identity and ensure the confidentiality of each call.

A)TRUE     

B)False

  51.Which of the following is the world’s first cellular system to specify digital modulation and     network level architecture?

A) AMPS    

B)GSM

C)IS-54      

D)CDMA

                               

  52.GSM stands for ____________

A)Global system for mobile              

B)Groupe special mobile

C)Global special mobile     

D)Groupe system mobile

                               

  53.Which of the following memory device stores information such as subscriber’s identification     number in GSM?

A) Register               

B)Flip flop

C)SMS       

D)SIM

  

54.Which of the following does not come under subsystem of GSM architecture?

A)BSS         

B)Channel

C)NSS        

D)OSS

               

55.Which of the following subsystem provides radio transmission between mobile station and MSC?

A) BSS        

B)  NSS

 C) OSS       

 D)BSC

               

56. ___________ manages the switching function in GSM.

A)BSS         

B)NSS

C)OSS        

D)MSC

                               

57. __________ supports the operation and maintenance of GSM.

A)MSC       

B)NSS

C)OSS        

D)BSS

               

58.The process of transferring a mobile station from one base station to another is

A) MSC       

B) Roamer

C) Hand off             

D)  Forward channel

                               

59. In a ______ handoff, a mobile station only communicates with one base station.

A) Hard      

B)soft

C)medium               

D)none of the above

               

60.In a ______ handoff, a mobile station can communicate with two base stations at the same time.

A) hard       

B)Medium

C) soft        

D) none of the above

                               

61.Select incorrect options relate with CDMA.

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

               

62.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

                               

63.The Authentication Centre (AUC) provides authentication and encryption parameters that verify the user's identity and ensure the confidentiality of each call.

A) True       

B) False

   

64.US digital cellular system based on CDMA was standardized as ________

A) IS-54      

B)IS-136

C)IS-95      

D)IS-76

               

65.In CDMA the pseudo random code must have following property

A)It must be deterministic 

B)It must appear random to listener without prior knowledge

C)Code must have long period        

D)All the Above

               

66.CDMA Technology is inherently Resistant to

A) interference 

B) Jamming

C)both a & b       

D) None from given

               

67.The Capacity of CDMA is depends on

A)Power Control Accuracy            

B)Interference Power

C) Both a & b      

D)None from Given

                               

68.Which Handoff work on principal of “Make before break”

A)Hard Handoff     

B)Soft handoff

C)Normal Handoff               

D) Regular Handoff

                               

69.“ Break before Make” is true for __________________

A)Hard Handoff     

B)Soft handoff

C)Normal Handoff               

D)Regular Handoff

                               

70. CDMA is advantageous over spreads spectrum techniques for

1.Privacy due to unique codes

2.It rejects narrow band interference

3.Resistance to Multipath fading

4.Its ability to frequency reuse

A)1,2 and 3 are correct       

B)1,2 and 3 are not correct

C)1 and 3 are correct         

D) All are correct