B.Tech
(U.P.T.U.)
EIGHT
SEMESTER EXAMINATION, 2004-2005
Wireless
communications
Q.1
Attempt any two parts of the following: (10*2=20
Marks)
Q.1(a)
Find a propagation loss in db in a system operating at 2.7 GHz when
the mobile unit is a distance of 213 m from base station. The
transmitting antenna has an aperture of 1 meter and receiving antenna
aperture is 10 cm.
Q.1(b)(i)
What is a slow fading channel, fast fading channel and frequency
selective channel?
Q.1(b)(ii)
What is meant by coherence time, coherence bandwidth and spread
factor of a fading channel.
Q.1(c)
Explain the impulse response model of a time varying mobile radio
channel.
Q.1(d)
Explain how the transmission bandwidth of a signal and speed of
surrounding object in a mobile radio channel affect the fading
pattern of a mobile radio channel.
Q.2
Attempt any four parts of the following: (5*4=20 Marks)
Q.2
(a) Explain with the help of block diagram the working of quadrature
modulation based MSK modulator.
Q.2(b)
Explain four parameters which are considered for quality speech
transmission and reception.
Q.2(c)
Explain frame efficiency in a TDMA system. How many number of channel
slots can be provided in a TDMA mobile system whose channel bandwidth
is Bc
and total spectrum allocated is Bt.
The maximum number of TDMA users supported on each radio channel is
m and allocated guard band is Bg.
Q.2(d)
What is near–far problem in CDMD wireless system ? What is done to
combat this problem ?
Q.2(e)
Explain cochannel interference and adjacent channel interference in a
cellular system.What is the relation between cochannel resue ratio
and cluster size in a cellular system?
Q.2(f)
On what factors does the hand off depend in the mobile system? What
is a forced hand off and mobile assisted hand off?
Q.3
Attempt any four parts of the following: (5*4=20
Marks)
Q.3
(a) Define radio capacity of a cellular system. The total allocated
spectrum for a cellular system is Bt
and channel bandwidth is Bc.
If the co-channel reuse factor Q for a cluster size N, What is the
ratio capacity for a path loss exponent n ?
Q.3
(b) Explain the methods for increasing the capacity of cellular CDMA
system.
Q.3
(c) Explain the salient features of VS DC/ AMPS Interim standard 54
(IS-54).
Q.3
(d) Explain the functions of all the channels in united states
digital cellular (USDC) system.
Q.3
(e)(i) Explain cyclic redundancy check process for detection of error
in mobile channel.
(ii)
Explain forward error correction process.
Q.3
(f) Explain the communication standard of any one mobile system.
Q.4
Attempt any two parts of the following: (10*2=20 Marks)
Q.4
(a) What is the difference between wireless and fixed telephone
networks? Explain with the help of block diagram the working of a
cellular radio network.
Q.4
(b) What is common channel signaling? Describe the common channel
signaling architecture for wireless networks.
Q.4
(c) Explain the following:
(i)
Message transfer part of signaling system No.7 (SS7).
(ii)
Wireless multimedia.
Q.5
Attempt any two parts of the following: (10*2=20 Marks)
Q.5
(a) Explain the satellite network configuration for a point to point
link, broadcast link and VSAT link. Explain the fixed format FDMA
format for satellite communication.
Q.5
(b) What is universal mobile telecommunication system. Explain its
working with reference to distributed database and network
reachability.
Q.5
(c) Explain the working of all traffic channels and controlled
channels used in GSM system.
Q.5
(d) Explain the modification in standard which have been proposed in
third generation cellular system.
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