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1.Draw the architecture of GSM system and
explain each block in brief.
2.Compare GSM, IS-136 and IS-95 standards
in terms of modulation schemes, multiple access schemes, frequencies used,
physical channel bandwidth, number of users/ physical channel and typical power
radiated by mobile stations using these standards. Give your answer in
tabulated form.
3.List advantages and disadvantages of
CDMA compared to GSM.
4.Explain in details the third
generation(3G) wireless networks standards:- 1) 3GW-CDMA (UMTS) 2) 3G cdma2000
3) 3G TD - SCDMA
5.With the aid of block diagrams, explain
in detail the IS-95 CDMA forwardand reverse channels and compare the two
6.Explain HSCSD for 2.5 GSM.
7.2G and 3G wireless networks.
8.Compare Wi-Fi and WiMAX in brief.
9.Compare HSCSD and GPRS. Explain briefly
GPRS
10.Answer following questions with respect
to Wi-MAX technology:( full-form, access method, approximate coverage range in
km, upper limit on data rate , range of radio channel bandwidth, two
applications)
1.Explain the three basic propagation
mechanisms whichimpact the propagation of signal in a mobile environment.
2.Give complete classification of types of
small-scale fading.
3.What is large scale propagation? Explain
in detail the free space propagationmodel
4.Explain in detail the impulse response
model of a multipath channel
5.Explain in detail the types of small
scale fading (including time delay andDoppler spread).
6.Derive the expression for Feher’s upper
bound.
7.Explain (i ) The effects of multipath
fading
(ii) Doppler spectrum
(iii) Multipath delay spread
8.Derive an expression for a ground
reflection model assuming distance between transmitter and receiver antenna is
very large compare to heights of the antennas.
9.Find median path loss using Okumura’s
model for d=50 km hte=100 m,hre=10 m. If EIRP from base station is 1kW at 900
MHz, find receivedpower. Take Amu(900 Mhz(50 km))=43 dB and GAREA=9 dB.
10.Compute the absolute mean path loss at
d0=3m and at d=22 m for a mobile radio system operated in the 2.4-to 2.48 GHz
authorized band. Assume the path loss exponent is n=3.5. Assume the first two
meters are LOS, afterwards NLOS propagation should be assumed.
11.Describe the concept of Doppler effect
with relevant mathematical expressions.
12.The received power at a distance of 100
km is 5 nw for a communication link. Determine the received power at a distance
200 km for the same link. Assume free space propagation mechanism.
13.For the Knife-edge geometry of FIG.1
show that ʋ=α(2 d1 d2/(λ(d1+d2)))1/2 , approximately. Assume d1,d2>>h
14.Suppose that a mobile station is moving
along a straight smooth surface between base stations BS1 and BS2. The distance
between BS1 and BS2 is 2000 m. Assume that the received power in dBm at Base
station is given by Pr=P0- 10*n*log (d/d0), where d is the distance between
mobile station and base station in meters. P0 is the power at distance d0 from
the mobile. Assume that P0=0 dBm and d0=1 m. Let n denote path loss exponent
which is 2.9. Given that the minimum usable level of signal is -88dBm and the
mobile is currently connected to BS1, determine the hand-off margin if hand-off
time is 4.5 second and the mobile speed is 100 km/hr.
15.Explain free space propagation of radio
signal.Establish the relation for thereceived power in free space. Define path
loss in free space.Calculate thereceived power at a distance of 3 KM from the
transmitter if the path loss exponent is 4.Assume that the transmitting power
of 4 W at 1800MHz.,ashadow effect of 10.5 dB,and the path loss at a reference
distance (do=100m) of -32dB.What is the allowable path loss? .
1.Explain in details about various channel
assignment strategies.
2.Explain the following terms with respect
to wireless networks:
a.Frequency
Reuse
b. Co-channel interference
c. Handoff
d.Umbrella
cell approach
e.Dwell
time
f.Cell
dragging
g.Cluster
h.MAHO
i. Channel Capacity
j.Differentiate
between Hard hand off and Soft handoff.
3.Why is hexagonal cell shape preferred
over square or triangular cell shape to represent the cellular architecture
4.Calculate the total available channels
for a cellular system having a total bandwidth of 60MHz which uses two 50 kHz
simplex channels to provide full duplex voice and control channels. Assume that
the system has nine cell reuse pattern and 1 MHz of the total BW is allocated
for control channels, determine an equitable distribution of control channels.
Also calculate the number of the control channels and voice channels/cell.
Assume the area of the cell is 9 Sq Km and the area of the entire system is
3630 Sq Km. If the cluster size is reduced to 4, what is the system capacity.
Comment on this.
5.A cellular service provider decides to
use a digital TDMA scheme which can tolerate a signal-to-interference ratio of
15 dB in the worst case. Find the optimal value of N for (a) omni directional
antennas, (b) 120* sectoring, and (c) 60* sectoring. Should sectoring be used?
If so, which sectoring (120* or 60*) will be better? Assume a path loss
exponent n=4.
6.Prove that for a hexagonal symmetry,the
co-channel reuse ratio is given by Q=(3N)1/2.
7.Illustrate the principle of cell
splitting in a cellular system. Prove that the transmit power of the microcell
must be reduced by 12 dB in order to fill in the original coverage area with
microcells, while maintaining the S/I requirement for the path loss exponent
n=4.
8.For a seven cell reuse pattern and
hexagonal cell geometry show that 120* sectoring improves signal to
interference ratio by about 5 dB.
9.A cellular system has 32 cells; each
cell has 1.6 km radius and the system reuse factor of 7. The system is to
support 336 traffic channels in total. Determine the total geographical area
covered, the number of traffic channels per cell and total number of
simultaneous calls supported by this system.
10.Assuming six co-channel interfering
cells, find the S/I ratio for path loss co-efficients of n=3 and n=4. Consider
cluster size N=7. In which case 15 dB requirement is met?what needs to be
changed to meet the same condition in second case?
11.For a regular cellular structure with
equal size hexagonal cells, show that D/R= (21) ½ , Where D is the minimum distance
between the centers of adjacent cells and R is the radius of each cell. Assume
7-cell reuse pattern.
12.Compare the S/I ratio for a mobile radio
for the following cases of cellular system with frequency reuse factor of 7 for
(i) Omni directional antenna (ii) 120* Directional antennas.
13.Consider two different cellular systems
that share the following characteristics. The frequency bands are 825-845 MHz
for uplink and 870-890 MHz for the downlink. A duplex circuit consists of one
30 kHz channel in each direction. The systems are distinguished by the reuse
factor, which are 4 and 19 respectively. For these systems, (i) Find the number
of simultaneous communications that can be supported by a single cell in each system. (ii) Suppose that
in each systems the cluster of cells (4,19) is duplicated 16 times, find the
number of simultaneous communications that can be supported by each system.
(iii)Suppose the average user makes 6 calls per 24 hours and mean call duration
is 6 minutes, estimate the total number of users that can be supported by each
system. (iv) If the billing for each customer is at the rate of 50
paisa/minute, determine average revenue per user (ARPU).
14.Derive the expression for S/I ratio for
adjacent channel interference for cellular systems.
15.Derive an expression for a ground
reflection model assuming distance between transmitter and receiver antenna is
very large compare to heights of the antennas.
16.The received power at a distance of 100
km is 5 nw for a communication link. Determine the received power at a distance
200 km for the same link. Assume free space propagation mechanism.
For a seven cell
reuse pattern and hexagonal cell geometry show that 120 sectoring improves
signal to interference ratio by about 5 dB.
