B.Tech
(U.P.T.U.)
EIGHT
SEMESTER EXAMINATION, 2009-2010
Wireless
communications
Q.1
Attempt any four parts of the following: (5*4=20
Marks)
Q.1(a)
Consider free space propagation model. Calculate the received power
is dBM at a free space distance of 100 meter from the transmitting
Antenna, if the transmitter produced 50 Watt of power and it apply to
unity gain antenna with a 900 Mhz carrier frequency.
Q.1(b)
Explain three basic propagation mechanism. Consider ground reflection
model. Calculate total electric field at any distance from
transmitting antenna?
Q.1(c)
What are the small-scale multipath propagation? Discuss the factors
influencing small scale multipath fading.
Q.1(d)
A general design rule for microwave link is 60% clearance of the
first Fresnel zone. For a 1 km link at 2.5 GHz , what is the maximum
first Fresnel zone radius? What clearance is required for this
system?
Q.1(e)
Derive the impulse response model for a multipath channel.
Q.1(f)
Do practical link budget design using log distance path loss model.
Q.2
Attempt any four parts of the following: (5*4=20 Marks)
Q.2
(a) Explain the working of direct sequence spread spectrum (DS-SS)
with the help of block diagram.
Q.2(b)
A FF-SS user 50 KHz channels over a continuous 20 MHz spectrum. Fast
frequency hopping is used, where two hops occurs for each bits. If
BFSK modulation is used find out number of Hops per second if each
user transmits at 25 kbps.
Q.2(c)
Derive probability of error for coherent binaryPSK modulation is slow
flat fading channels.
Q.2(d)
Derive the average probability of bit error for DS-SS system for K
number of user.
Q.2(e)
Discuss survey of equalization techniques.
Q.2(f)
Classify and explain diversity techniques used in wireless
communication.
Q.3
Attempt any two parts of the following: (10*2=20
Marks)
Q.3
(a) With the help of block diagram, explain the working of linear
predictive coder system. What are the advantages of non-uniform
quantization ?
Q.3
(b) Elaborate the features of frequency division multiple access
scheme. Give its two applications. If in AMPS, cellular operator is
allocated 12.5 MHz for each simplex band and if Bt
is
12.5 MHz, Bguard
is
10 KHz, find the number of channel available in an FDMA system.
Q.3
(c) Classify speech coders and explain with suitable diagram each
type in brief.
Q.4
Attempt any two parts of the following: (10*2=20 Marks)
Q.4
(a) Discuss the importance of adjacent channel interference. How
capacity improvement is achieved using cell splitting approach?
Q.4
(b) What is prioritizing hand offs and where it is used? If 20 MHz of
total spectrum is allocated for a duplex wireless cellular system and
each simplex channel has 25 kh. RF bandwidth, find number of duplex
channel and total number of channel per cell size, if N=4 cell resuse
is used.
Q.4
(c)(i) What are various channel assignment strategies? Explain them.
(ii)
Discuss the concept of macro, micro and pico cells. When do they
become useful?.
Q.5
Attempt any two parts of the following: (10*2=20 Marks)
Q.5
(a) What does GSM stands for? Describe its entire working. What are
the features added in 2.5G wireless network from 2G network?
Q.5
(b) Disscuss the features of IS-95 in details.
Q.5
(c) Explain IEEE 802.11 MAC protocol and write the parameter of IEEE
standard.
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