DOEACC Society 2006 DOEACC C Level CE2 - Wireless

CE2-R3: WIRELESS AND MOBILE NETWORKS
NOTE:
Time: three Hours Total Marks: 100
1.
a) Sometimes when a cellular user crosses the boundary from 1 cell to another, the current
call is abruptly terminated, even though all transmitters and receivers are functioning
perfectly. Why?
b) What is the difference ranging from adjacent channel interference and co-channel interference?
c) Sometimes the user is moving within the cell towards the BSS and experiences sudden loss
in signal strength. What is it due to? elaborate the factors responsible for temporary signal
loss?
d) Why are GEO systems for telecommunications currently being changed by fiber optics?
e) Why the collision avoidance is used in the wireless ad-hoc networks/WLAN in place of the
collision detection methods?
f) How is Ultra Wide Band (UWB) various from frequency hopping used in Blue-tooth?
g) Prove that the capacity of WLL is independent of the path loss.
(7x4)
2.
a) Differentiate ranging from wireless and fixed networks. elaborate the time limitations in wireless
networking?
b) Show that the magnitude (envelope) of the sum of 2 independent identically distributed
complex (quadrature) Gaussian sources is Rayleigh distributed. presume that the Gaussian
sources are zero mean and have unit variance.
(8+10)
3.
a) The US Digital Cellular TDMA system uses a 48.6 kbps data rate to support 3 users per
frame. every user occupies 2 of the 6 time slots per frame. What is the raw data rate
given for every user?
b) Using a concentric Cellular geometry determine recursive expressions for the 2 weighting
factors for the equivalent hexagonal geometry for the 2nd layer and all following layer
cells.
(9+9)
4.
a) Show how to integrate the registration and the authentication procedures in GSM.
b) Which of the subsequent is a blank-and-burst channel in AMPS system? what are.
i) Paging Channel
ii) Reverse Voice Channel
iii) Slow Associated Control Channel
iv) Fast Associated Control Channel
(8+10)
5.
a) What mechanisms would reason breakdown in the reverse link of an IS-95 CDMA System
as the number of users in a sector approaches the theoretical limit.
b) explain the similarities and differences ranging from a Conventional Cellular Radio System and
Satellite Based Radio System. Which system would support a larger number of users for a
provided frequency allocation? Why?
(9+9)
CE2-R3 Page one of two January, 2006
1. ans ques. one and any 4 ques. from two to 7.
2. Parts of the identical ques. should be answered together and in the identical
sequence.
6.
a) Compare the Infrared Transmission Technology with Radio Transmission Technology used
in WLANs. explain the issue of hidden terminals. How is it solved?
b) elaborate the various techniques used for Improving Coverage and Capacity in Cellular
System? How co-channel interference is decreased using sectoring?
(9+9)
7.
a) What is the need for security in Blue-tooth system? How does authentication take place
ranging from 2 Blue-tooth devices? Use diagrams to support your explanation.
b) explain different channel allocation technologies used in WLANs? Compare fixed and
dynamic channel allocation schemes.
(8+10)
CE2-R3 Page two of two January, 2006

Earning:   Approval pending.