Deck 16: Advanced Data Communications Topics

Question 1

SSB is a variant of AM that requires only half of the bandwidth.

Answer 1

True

Question 2

Modulation does not permit frequency-division multiplexing.

Answer 2

False

Question 3

Stop-and-wait flow control is more efficient than sliding-window flow control.

Answer 3

False

Question 4

When only analog transmission facilities are available,modulation is required to convert the digital data to analog form.

Question 5

The spectrum of the AM signal consists of the original carrier plus the spectrum of the input signal translated to f_c.

Question 6

Amplitude modulation is a linear process and produces frequencies that are the sum and difference of the carrier signal and the components of the modulating signal.

Question 7

The principal techniques for modulation using analog data are amplitude modulation,frequency modulation,and phase modulation.

Question 8

The LFSR implementation of a cyclic error-correcting encoder is the same as that of the CRC error-detecting code.

Question 9

LDPC codes cannot be efficiently implemented for high-speed use.

Question 10

RS codes are well suited for burst error correction.

Question 11

With a nonsystematic code it is more difficult to determine a technique for generating a codeword from a block of data bits.

Question 12

________ uses one sideband and a reduced power carrier.

A)SSB
B)DBS
C)VSB
D)BTC

Question 13

___________ rule demonstrates that both FM and PM require greater bandwidth than AM.

A)Reed's
B)Carson's
C)Chaudhuri's
D)Solomon's

Question 14

For unguided transmission it is virtually impossible to transmit baseband signals.

Question 15

With the exception of the repeat-accumulate code,the LDCP code is systematic.

Question 16

Voice signals are transmitted over telephone lines at their original spectrum,which is referred to as __________ transmission.

A)modulation
B)baseband
C)frequency
D)parity

Question 17

The _________ is the ratio of the amplitude of the input signal to the carrier.

A)modulation index
B)frequency phase
C)division rate
D)none of the above

Question 18

The syndrome indicates which of the individual parity-check equations do not equal 0.

Question 19

__________ is a basic characteristic of a signal used for modulation.

A)Frequency
B)Amplitude
C)Phase
D)All of the above

Question 20

DSBSC filters out the carrier frequency and sends both sidebands but does not use as much power and bandwidth as DSBTC.

Question 21

Special cases of angle modulation are frequency modulation and ________ modulation.

A)VSB
B)repeat-accumulate
C)code rate
D)phase modulation

Question 22

Bose-Chaudhuri-Hocquenghem is an example of a _________ code.

Question 23

A ____________ code takes a fixed-length input and produces a fixed-length check code.

A)cyclic error-correcting
B)cyclic redundancy check
C)cyclic logic check
D)none of the above

Question 24

_________ codes are a widely used subclass of nonbinary BCH codes.

Question 25

To compute an error-locator polynomial and solve for its roots is a technique for BCH decoding proposed by ________ .

A)Berlekamp
B)Reed-Solomon
C)Bose
D)Chaudhuri

Question 26

Cyclic codes can be easily encoded and decoded using __________ registers.

Question 27

The ratio of redundant bits to data bits,(n - k)/k,is called the _______ of the code.

Question 28

Frequency modulation and phase modulation are special cases of _________ modulation.

Question 29

__________ codes are among the most powerful cyclic block codes and are widely used in wireless applications.

A)Parity check
B)BCH
C)LPDC
D)Repeat-accumulate

Question 30

__________ has been defined as the process of combining an input signal m(t)and a carrier at frequency fc to produce a signal s(t)whose bandwidth is (usually)centered on fc.

Question 31

__________ proposed an approach for the construction of LDPC codes by defining the LDPC parity-check matrix.

A)MacKay
B)Reed
C)Gallager
D)Neal

Question 32

Reed-Solomon is an example of a ________ code.

Question 33

An LDPC construction technique that results in a systematic code is called a

Question 34

_________ modulation is the simplest form of modulation.

Question 35

A _________ code takes an input of arbitrary length and produces a fixed-length CRC check code.

A)BCH
B)LFS
C)VSB
D)CRC

Question 36

The m * n matrix H = [hij] is called the _______ .

Question 37

Many of the error-correcting block codes that are in use are in a category called ________ .

A)cyclic codes
B)logic codes
C)linear codes
D)BCH codes

Question 38

In the case of the CRC,a particular cyclic code can be represented by a polynomial divisor,called the ___________ .

Question 39

With __________ codes,data are processed in chunks of m bits,called symbols.

A)FEC
B)systematic
C)Reed-Solomon
D)all of the above

Question 40

The ratio of data bits to total bits,k/n,is called the _________ .

A)code rate
B)parity-check matrix
C)systematic code
D)redundancy

Question 41

________ codes make highly efficient use of redundancy and block lengths and symbol sizes can be easily adjusted to accommodate a wide range of message sizes.

Question 42

(A)Process received bits to compute the syndrome code in exactly the same fashion as the encoder processes the data bits to produce the check code; (B)if the syndrome bits are all zero,no error has been detected; and (C)if the syndrome is nonzero,perform additional processing on the syndrome for error correction,-- is the procedure for the decoding of a _________ code.

Question 43

The ________ is a measure of how much additional bandwidth is required to carry data at the same data rate as without the code.

Question 44

For a parity-check code there are three functions to perform: encoding,error detection,and __________ .