DOEACC B Level Networking and Mobile Communications previous years question papers

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1.
a) Differentiate between Narrow Band System and Broad Band System.
b) What is Handoff and roaming? How is handoff performed during roaming?
c) “The MAC protocol for the wired network cannot be used for wireless.” Is the statement
true or false? Justify your answer.
d) Explain briefly SMS with security aspects for secure SMS?
e) Explain Ad-Hoc Network Topology. Compare the Ad-Hoc Topology with Infrastructure
Topology.
f) Discuss the goals of cryptography. What is Cryptosystem and Encryption?
g) Draw and discuss the conceptual model of operation of MTSO. Give its role in providing
Mobile services.
(7x4)

2.
a) Explain frequency reuse in Cellular Communications. What are the advantages of this
approach? List different frequency reuses schemes and explains any one of them.
b) If a US AMPS Cellular operator is allocated 12 MHz for each simplex band and if Bt is
12 MHz, Bguard is 10 KHz and Bc is 30 KHz, find the number of channels available in FDM
system.
(9+9)

3.
a) Differentiate between Circuit Switched Data Services and Packet Switched Data
Services on Cellular Networks.
b) Explain pure ALOHA and slotted ALOHA with their usage in mobile communication
system.
c) Explain the following terms:
i) Processing Gain
ii) Pseudo random code generator
iii) Walsche code
(6+6+6)

4.
a) How do the third generation cellular systems differ from second generation cellular
systems?
b) If 30 MHz of total spectrum is allocated for a duplex wireless cellular system in which
simplex channel has 35 KHz RF bandwidth. Find the number of duplex channels and
number of channels per cell site, if N=12 cell reuse is used.
c) Discuss the basic architecture of GPRS and explain, how it is used to enhance data
rates in a GSM system.
(6+6+6)

1. Answer question 1 and any FOUR questions from 2 to 7.
2. Parts of the same question should be answered together and in the same
sequence.

5.
a) What are the different ways in which secret keys can be distributed to two different
communicating parties?
b) What are the reasons for WAP defining its own security layers? Discuss the important
function of WSP and WAE.
c) Name the layers specified by IEEE 802.11 standard. Discuss the role of these layers.
(6+6+6)

6.
a) What is a Protocol Data Unit? List and explain its fours fields.
b) What is the function of a WAP gateway? Discuss WAP protocols.
c) Write short notes on Direct Sequence Spread Technology & Frequency Hopping Spread
Spectrum Technology.
(3+6+9)

7.
a) Which technology is generally used in most of VSATs installed globally? What are
reasons of using it? How can the frequency carrier be assigned between any two VSATs
on a demand basis?
b) What are the general requirements for Radio Access to IMT-2000? Discuss the
evaluation and specification process for IMT-2000 radio access technologies.
(9+9)

1.
a) What are the advantages and disadvantages of cellular systems with small cells?
b) Name the three basic propagation mechanisms which impact propagation in a mobile
communication system. When do they occur?
c) What are the classes of IP addressing scheme and how many numbers of host-IDs and
network IDs are there in each class?
d) “VSAT operates at slow data rates”. Justify the statement by giving reasons.
e) What is a WAP gateway? Discuss its important functions.
f) Determine the maximum throughput that can be achieved using ALOHA and slotted
ALOHA.
g) What are the reasons for the use of infrared transmission for WLANs?
(7x4)

2.
a) Discuss the benefits of spread spectrum system? How the spread spectrum can be
achieved?
b) Explain Circuit switching and Packet switching. What are the factors that influence the
use of packet switching in personal communication services?
c) Discuss the basic differences and similarities between wireless WAN and WLAN.
(6+8+4)

3.
a) What do you mean by DECT? Explain its system architecture.
b) Discuss the problems and advantages of forwarding mechanisms in ad-hoc networks
regarding security, power saving and network stability.
c) Compare and contrast Bluetooth with HIPERLAN.
(6+6+6)

4.
a) Draw the GPRS architecture showing the main components. Which is the component
responsible for assignment of an IP address to the mobile? Why does there a need of
mapping between the mobile’s IMSI and its IP address?
b) What are the requirements for a mobile IP? What are the entities for mobile IP? Explain
how data is transferred from a mobile node to a fixed node.
(8+10)

5.
a) Discuss the general system features of personal access communication system.
b) Explain the functional Network Architecture of IMT-2000.
(9+9)

1. Answer question 1 and any FOUR questions from 2 to 7.
2. Parts of the same question should be answered together and in the same
sequence.
6.
a) Explain the data transfer services that OSI defines for the discrete data components
passed across the interface and between peer entities.
b) What are the major technologies for WLL system? Discuss the advantages and
disadvantages of these technologies.
(10+8)

7.
a) What is a Broadcast Network? What is the significance of network layer in broadcast
network?
b) Explain the OSI model in detail.
(9+9)

1.
a) How does LLC sublayer ensure to transport efficiently multimedia traffic over the radio
interface?
b) Differentiate between Direct Sequence and Frequency Hopping spread spectrum
techniques.
c) What are the data and messaging services supported by Personal Access
Communication System (PACS)? Explain briefly.
d) What is a Bluetooth technology? Discuss the different layers that Bluetooth uses.
e) List four significant factors which influence the choice of speech-coders in mobile
communication. Which factor influences more as per your opinion? Give reasons.
f) Discuss the advantages and disadvantages of Ad-Hoc Networks.
g) Explain the architecture and features of “Short Message Service”.
(7x4)

2.
a) A pure ALOHA network transmits 200-bit frames on a shared channel of 200 kbps. What
is the throughput if the system (all stations together) produces 1000 frames?
b) Discuss the advantages of WLAN. What are its disadvantages? What are design goals
for WLANS?
c) If GSM uses a frame structure where each frame consists of eight time frame slots, and
each time slot contains 156.25 bits, and data is transmitted at 270.833 kbps in the
channel. Find
i) The time duration of a bit
ii) The time duration of a slot
iii) The time duration of a frame.
(6+6+6)

3.
a) What is channelization? Explain at least two channelization protocols in detail?
b) Explain the typical call flow sequences in GSM.
(9+9)

4.
a) What are the advantages and disadvantages of layered model?
b) Explain small scale multipath propagation. Discuss the factors that influence small scale
fading.
c) Briefly discuss the operation of a CDMA multiple access system. In what ways it is
superior to TDMA? Mention the potential application of CDMA.

1. Answer question 1 and any FOUR questions from 2 to 7.
2. Parts of the same question should be answered together and in the same
sequence.
(4+5+9)

5.
a) Differentiate between slotted ALOHA and Pure ALOHA? Discuss the limitation of pure
ALOHA.
b) What are the application areas of DECT? Discuss the conceptual model of DECT in
brief.
c) What are the limitations in wireless networking? Discuss the security issues in wireless
networks.
(6+6+6)

6.
a) Discuss the advantages and disadvantages of VSAT networks. Explain the operation of
VSAT.
b) Differentiate between:
i) Wireless Datagram Protocol and Wireless Transaction Protocol
ii) Wireless Session Protocol and Wireless Application Environment
(10+8)

7.
a) Explain, how MACAW protocol is operated in WLANS?
b) Discuss the features of the following:
i) Circuit Switched Data Services
ii) Packet Switched Data Services.
(9+9)

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