Download PTU. I.K. Gujral Punjab Technical University (IKGPTU) M.Tech. ECE 1st Semester 75800 ADVANCED COMMUNICATION SYSTEMS Question Paper.

1 | M-75800 (S35)-1940

Roll No. Total No. of Pages : 02
Total No. of Questions : 08
M.Tech.(ECE)(Wireless communication)(2018 Batch) (Sem.?1)
Subject Code : MTWC-PE2A-18
M.Code : 75800
Time : 3 Hrs. Max. Marks : 60

INSTRUCTIONS TO CANDIDATES :
1.Attempt any FIVE questions out of EIGHT questions.
2.Each question carries TWELVE marks.

1. a) Using the Gram schmidt orthogonalization procedure, find a set of orthonormal basis
function to represent the three signals S
1
(t), S
2
(t) and S
3
(t) as given below :

FIG.1
b) Express each of these signals in terms of the set of basis functions found in a part (a)
2. Use Schwarz's inequality to derive optimum transfer function for matched filter i.e.
h
opt
(t), which maximizes output signal-to-noise-ratio (SNR
o,max
) for the real-valued signal
?(t). Also, mention H
opt
(f) and SNR
o,max
clearly.
3. Consider a input binary sequence 0010110 at the input of modified duo-binary signaling
scheme. Find the corresponding output binary sequence. Also extract the original
sequence at the receiver using the decision rule defined for the same.
4. What is correlator? Explain the difference and similarity between correlator and matched
filter.
0
1
2
3
4
?1
?2
?3
?4
1 2 3
0
1
2
3
4
?1
?2
?3
?4
1
2
3
0
1
2
3
4
?1
?2
?3
?4
1 2 3
?5
t t t
S (t) 1 S (t) 2 S (t) 3
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1 | M-75800 (S35)-1940

Roll No. Total No. of Pages : 02
Total No. of Questions : 08
M.Tech.(ECE)(Wireless communication)(2018 Batch) (Sem.?1)
Subject Code : MTWC-PE2A-18
M.Code : 75800
Time : 3 Hrs. Max. Marks : 60

INSTRUCTIONS TO CANDIDATES :
1.Attempt any FIVE questions out of EIGHT questions.
2.Each question carries TWELVE marks.

1. a) Using the Gram schmidt orthogonalization procedure, find a set of orthonormal basis
function to represent the three signals S
1
(t), S
2
(t) and S
3
(t) as given below :

FIG.1
b) Express each of these signals in terms of the set of basis functions found in a part (a)
2. Use Schwarz's inequality to derive optimum transfer function for matched filter i.e.
h
opt
(t), which maximizes output signal-to-noise-ratio (SNR
o,max
) for the real-valued signal
?(t). Also, mention H
opt
(f) and SNR
o,max
clearly.
3. Consider a input binary sequence 0010110 at the input of modified duo-binary signaling
scheme. Find the corresponding output binary sequence. Also extract the original
sequence at the receiver using the decision rule defined for the same.
4. What is correlator? Explain the difference and similarity between correlator and matched
filter.
0
1
2
3
4
?1
?2
?3
?4
1 2 3
0
1
2
3
4
?1
?2
?3
?4
1
2
3
0
1
2
3
4
?1
?2
?3
?4
1 2 3
?5
t t t
S (t) 1 S (t) 2 S (t) 3
2 | M-75800 (S35)-1940

5. What are the advantages of orthogonal frequency division multiplexing (OFDM) for
digital transmission over channels subject to fading, and what is the main disadvantage of
OFDM? Find an expression to find the bit error rate over AWGN channel for OFDM
system.
6. Derive the condition of maximum likelihood (ML) decision rule and show that ML
decision rule is to choose the message point closest to the received signal using likelihood
function for AWGN channel.
7. Find an probability of Bit Error rate for the BFSK receiver in a digital communication
system receives the following signal :
r(t) = s
i
(t) + n(t), i =1,2
Where, s
i
(t) is the signal component and n(t) is white Gaussian noise with zero mean and
N
0
/2 variance.
8. Four signals s
1
(t), s
2
(t), s
3
(t) and s
4
(t) are of equal energy E and are defined for finite
interval 0 ? t ? T as s
1
(t) =
1 2 2
( ), ( ) ( ),
E E
t s t t
T T
? ? ? s
3
(t) = ?s
1
(t) and s
4
(t) = ?s
2
(t).
Also ?
1
(t) and ?
2
(t) are orthonormal functions defined for the interval 0 ? t ? T. Assume
the signals are transmitted with equal probability over AWGN channel. Determine :
a) The dimension of observation space
b) Signal constellation
c) Decision regions
d) Euclidean distance between signal points.

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