B3.5-R3: NETWORKING AND MOBILE COMMUNICATIONS
: JANUARY 2006
NOTE:
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.
Time: 3 Hours Total Marks: 100
1.a) How do the layers of TCP/IP protocol suite correlate to the layers of the OSI?
b) Compare the performance of slotted aloha with that of pure aloha. What is the limitation of aloha protocol in general?
c) Explain the concepts of handoff and dropped call rate. What are soft and hard handoffs.
d) Draw and discuss the conceptual model of DECT (Digital European Cordless Telephone). Give its application areas.
e) If 20 MHz of total spectrum is allocated for a duplex wireless cellular system, with Simplex channel has 25KHz RF bandwidth, find the number of duplex channels and number of channels per cell site, if N=12 cell reuse is used.
f) Compare and contrast the various 2.5G technology paths that each of the major 2G standards provide. Which path has the highest Internet access speed?
g) Draw and explain the wireless LAN architecture and also explain the terms infrastructure mode and Adhoc mode.
(7x4)
2.a) What are connection oriented and connectionless services? What are service primitives? Explain with an example how these are used.
b) Discuss the role of transport layer and data link layer in the OSI model.
c) What is spread spectrum communication. Explain the terms processing gain, pseudo random code generator and Walsch code.
(6+6+6)
3.a) What are mobile data communication services and name them. Describe the architecture of HSCSD (High Speed Circuit Switched Data).
b) Draw the detailed block diagram of a cellular system and explain. Also explain the different strategies implemented to avoid interferences in TDMA, FDMA & CDMA systems.
(9+9)
4.a) Give an account of radio specifications for cordless telecommunication systems such as CT2and DECT.
b) What is VSAT? Give the components of VSAT systems.
c) Draw and explain the functional architecture for PACS (Personal Access Communication System). Discuss the frame structure and its radio aspects.
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5.a) Draw CDMA based mobile system architecture and explain, how it provides reliable basic phone services. Write the benefits of CDMA to users.
b) Draw the basic reference architecture and signaling interfaces for GSM. Why is Smart card needed in GSM, while it is not required in AMPS?
(9+9)
6.a) How do you compare D-AMPS and GSM systems in terms of coverage area, transmitted power and error control system, explain what you can do to address adjacent channel and co-channel interference.
b) With the help of a neat diagram explain the UMTS (Universal Mobile Telecommunication System) network architecture. Discuss in detail the logical parts: I) user equipment and ii) core network. How is the number of handoffs reduced of r the fast moving traffic?
(9+9)
7.a) Draw and explain the WAP network configuration. Also discuss the WAP protocol stack.
b) What is frequency management? Discuss different fixed channel assignment strategies. What are its limitations are compared to non-fixed channel assignment methods.
(9+9)
