Digital Communications

Bandwidth Efficiency Plane and Bandwidth Efficient Modulation

Question 1
Marks : +2 | -2
Pass Ratio : 100%
Which modulation scheme uses nonlinear transponders?
MSK
Offset QPSK
MSK & Offset QPSK
None of the mentioned
Explanation:
Offset QPSK and MSK are two examples of constant envelope modulation schemes that are attractive for systems using non linear transponders.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
The bandwidth efficiency increases as M increases.
True
False
Explanation:
The bandwidth efficiency decreases as M increases.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
The bandwidth efficiency of MFSK is
M/log2M
log2M/M
M/log10M
log10M/M
Explanation:
For non coherent orthogonal MFSK modulation the bandwidth efficiency is R/W=log2M/M.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
The primary communication resource is
Transmitted power
Received power
Efficiency
None of the mentioned
Explanation:
The primary communication resources are transmitted power and channel bandwidth.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
QPSK is a composite of
Two BPSK
Three BPSK
Two FSK
Two M-ary PSK
Explanation:
QPSK is effectively a composite of two BPSK signals transmitted on orthogonal components of the carrier.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
Greater the redundancy lesser is the bandwidth expansion.
True
False
Explanation:
Within the same block size, the code with greater redundancy requires more bandwidth expansion.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Which modulation is the most efficient one?
BPSK
BFSK
QPSK
QAM
Explanation:
Of all the modulation showed, QAM is the most bandwidth efficient one.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
The bandwidth efficiency of QFSK is _______ that of BFSK.
Greater than
Less than
Equal to
None of the mentioned
Explanation:
The bandwidth efficiency of QPSK is equal to that of the BFSK.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
Which modulation requires more bandwidth?
QPSK
OQPSK
BPSK
BFSK
Explanation:
BPSK requires more bandwidth than the other modulation techniques for the given level of spectral density.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
The IF transmission bandwidth of MFSK is
M/T
T/M
2M/T
M/2
Explanation:
In non coherent orthogonal MFSK modulation, the IF transmission bandwidth is WIF = M/T.