dc-unit-8 bits

7/17/2019 dc-unit-8 bits

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1. In general, Spread Spectrum communications is distinguished by which of these elements?a) The signal occupies a bandwidth much greater than that which is necessary to send the

information

b) The bandwidth is spread by means of a code which is independent of the datac) The receiver synchronizes to the code to recover the data

d) ll of the above

!. "hich of this is the way to spread the bandwidth of the signala) #re$uency hopping

b) Time hopping

c) %irect se$uenced) ll of the above

&. The digital data is directly coded at a much higher fre$uency. The code is generated pseudo'randomly, the receiver (nows how to generate the same code, and correlates the received

signal with that code to etract the data. "hich type of spread spectrum is this?

a) #re$uency hopping

b) Time hoppingc) %irect se$uence

d) *one of the above

+. The signal is transmitted in short bursts pseudo'randomly, and the receiver (nows before

hand when to epect the burst. "hich type of spread spectrum is this?

a) #re$uency hopping b) Time hopping

c) %irect Se$uence

d) *one of the above

. "hat is the data rate for daptive %ifferential -ulse ode /odulation 0%-/)a) (2its3sec

b) 14 (2its3secc) &! (2its3sec

d) 4+ (2its3sec

4. "hat is the data rate for 5ow %elay ode 6cited 5inear -rediction 05%'65-)?

a) (2its3sec

b) 14 (2its3secc) &! (2its3sec

d) 4+ (2its3sec

7. The subscriber unit correctly generates its own matching code and uses it to etract theappropriate signals. 6ach subscriber uses

a) singal independant channels.

b) several independant channels.c) singal dependant channels.

d) several dependant channels.

. In %/, the pseudo'random code must have the following property



a. It must be deterministic b. It must appear random to a listener without prior (nowledge of the code

c. The code must have a long period

d. ll of the above

8. "hat will be the correlation of two codes , if the two codes are identical ?

a. 9 b. 9.c. 1

d. Infinite

19. The bit rate of the -* code is called

a. hipping #re$uency 0fc)

b. Information rate 0fi)c. hip

d. 6poch

11. In %/, the bit rate of the digital data is called

a. chipping fre$uency

b. information ratec. chip

d. 6poch

1!. :ne bit of the -* code is called

a. chipping fre$uency

b. information ratec. chip

d. 6poch

1&. The length of time before the code starts repeating itself 0the period of the code) is calleda. chipping fre$uency

b. information rate

c. chipd. 6poch

1+. The epoch must be ;;;;;;;;; the round trip propagation delaya. shorter than

b. longer than

c. e$ual to

d. *one of the above

1. %/ technology is inherently resistant to

a. Interference b. <amming

c. 2oth 1 = !




14. The sharing of a medium and its lin( by two or more devices is called ;;;;;;;.a. modulation

b. encoding

c. line disciplined. multipleing

17. "hich multipleing techni$ue transmits analog signals?a. #%/ b. T%/

c. "%/

d. 0a) and 0c)

1. "hich multipleing techni$ue transmits digital signals?

a. #%/ b. T%/

c. "%/


18. "hich multipleing techni$ue shifts each signal to a different carrier fre$uency?

a. #%/

b. T%/c. 2oth 0a) and 0b)


!9. In synchronous T%/, for n signal sources of the same data rate, each frame contains

;;;;;;; slots.

a. n b. n > 1

c. n ' 1d. 9 to n

!1. In T%/, the transmission rate of the multipleed path is usually ;;;;;;; the sum of the

transmission rates of the signal sources.

a. greater than b. less than

c. e$ual to

d. not related to

!!. "hich multipleing techni$ue involves signals composed of light beams?

a. #%/

b. T%/c. "%/

d. none of the above



!&. ;;;;;;;;; utilization is the use of available bandwidth to achieve specific goals.a. #re$uency

b. 2andwidth

c. mplituded. *one of the above

!+. ;;;;;;;; can be achieved by using multipleing ;;;;;; can be achieved by using

spreading.a. 6fficiency privacy and anti@amming b. -rivacy and anti@amming efficiency

c. -rivacy and efficiency anti@amming

d. 6fficiency and anti@amming privacy

!. ;;;;;;;; is the set of techni$ues that allows the simultaneous transmission of multiple

signals across a single data lin(.a. %emodulating

b. /ultipleing

c. ompressing


!4. In a multipleed system, ;; lines share the bandwidth of ;;;; lin(.

a. 1 n b. 1 1

c. n 1

d. n n

!7. The word ;;;;;; refers to the portion of a ;;;;;;; that carries a transmission.

a. channel lin( b. lin( channel

c. line channeld. line lin(

!. ;;;;;; can be applied when the bandwidth of a lin( 0in hertz) is greater than the combined

bandwidths of the signals to be transmitted.

a. T%/ b. #%/

c. 2oth 0a) or 0b)

d. *either 0a) or 0b)

!8. #S/ is an ;;;;;;;;;techni$ue.

a. analog

b. digitalc. either 0a) or 0b)




&9. ;;;; is designed to use the high bandwidth capability of fiber'optic cable.a. #%/

b. T%/

c. "%/d. *one of the above

&1. ;;;;;; is an analog multipleing techni$ue to combine optical signals.

a. #%/ b. T%/c. "%/


&!. ;;;;; is a digital process that allows several connections to share the high bandwidth of alin(.

a. #%/

b. T%/c. "%/


&&. ;;;;; is a digital multipleing techni$ue for combining several low'rate channels into onehigh'rate one.

a. #%/

b. T%/c. "%/


&+. "e can divide ;;;; into two different schemesA synchronous or statistical.

a. #%/

b. T%/c. "%/


&. In ;;;;;;;; T%/, each input connection has an allotment in the output even if it is notsending data.

a. synchronous

b. statisticalc. isochronous


&4. In ;;;;;;;; T%/, slots are dynamically allocated to improve bandwidth efficiency.

a. synchronous

b. statistical

c. isochronousd. none of the above

&7. In ;;;;;;;;, we combine signals from different sources to fit into a larger bandwidth.

a. spread spectrum b. line coding

c. bloc( coding




&. ;;;;;;; is designed to be used in wireless applications in which stations must be able to

share the medium without interception by an eavesdropper and without being sub@ect to

@amming from a malicious intruder.a. Spread spectrum

b. /ultipleing

c. /odulationd. *one of the above.

&8. The ;;;;;;; techni$ue uses / different carrier fre$uencies that are modulated by the sourcesignal. t one moment, the sign modulates one carrier fre$uency at the net moment, the

signal modulates another carrier fre$uency.

a. #%/ b. %SSS

c. #BSS

d. T%/

+9. The ;;;;;; techni$ue epands the bandwidth of a signal by replacing each data bit with n

bits.

a. #%/ b. %SSS

c. #BSS

d. T%/



1. d

!. d&. c

+. b

. c

4. b7. b

. d

8. c19. a

11. b

1!. c1&. d

1+. b

1. c14. d

17. d1. b

18. a!9. a

!1. a

!!. c

!&. b!+. a

!. b

!4. c

!7. a!. b

!8. a

&9. c&1. c

&!. b

&&. b&+. b

&. a

&4. b&7. a

&. a&8. c

+9. b+1.

+!.



43.

dc-unit-8 bits

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