EC-503-B Mobile Communication - Dec 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aWrite the merits of cellular system and concept of frequency re-use.
   How to answer

   • Define cellular system and frequency reuse concept
   • List merits: capacity increase, spectrum efficiency, coverage, handoff
   • Explain reuse factor N, cluster, co-channel cells
   • Formula for capacity and reuse distance
2. 7 Marks
   bExplain the different generation of wireless network.
   How to answer

   • Define 1G to 5G generations
   • Frequency, switching, data rate for each generation
   • Key technologies: AMPS, GSM, CDMA, LTE
   • Comparison table
3. 7 Marks
   aExplain ground reflection propagation model.
   How to answer

   • Two-ray ground reflection geometry
   • Direct and reflected path, reflection coefficient
   • Path loss formula with transmitter-receiver heights
   • Diagram of propagation model
4. 7 Marks
   bDefine the terms: i) Doppler spread ii) Coherence time
   How to answer

   • Define Doppler spread due to mobility
   • Relation $B_D$ to velocity and wavelength
   • Define coherence time $T_c$
   • Relation $T_c \approx 1/B_D$ and implication
5. 7 Marks
   aWhat are cell-site antennas and mobile antennas?
   How to answer

   • Define cell-site/base station antennas
   • Types: omni, sector, panel antennas
   • Define mobile antennas: monopole, PIFA, whip
   • Requirements: gain, height, pattern
6. 7 Marks
   bExplain capacity of cellular system.
   How to answer

   • Define cellular capacity in Erlangs/channels
   • Relation to cluster size N and traffic
   • Channel capacity formula $C = M \times k$
   • Techniques to increase capacity
7. 7 Marks
   aExplain the architecture of GSM.
   How to answer

   • Block diagram: MS, BTS, BSC, MSC, HLR/VLR
   • Function of each subsystem
   • Interfaces Um, Abis, A
   • Call flow overview
8. 7 Marks
   bExplain GSM traffic channel and control channel.
   How to answer

   • Define traffic channels TCH/F, TCH/H
   • Define control channels BCCH, CCCH, DCCH
   • Purpose and burst structure
   • Uplink/downlink usage
9. 7 Marks
   aWhat is frequency hopped multiple access?
   How to answer

   • Definition of frequency hopping
   • Slow vs fast hopping
   • Advantages: interference averaging, security
   • Use in GSM
10. 7 Marks
    bDescribe CDMA with suitable diagram.
    How to answer

    • Principle of CDMA with spreading codes
    • Transmitter and receiver block diagram
    • Orthogonal codes and processing gain
    • Advantages and applications
11. 7 Marks
    aWhat are the dispersion parameters?
    How to answer

    • Define time and frequency dispersion
    • Parameters: delay spread, coherence bandwidth
    • Doppler spread, coherence time
    • Effect on ISI and fading
12. 7 Marks
    bDescribe the cell splitting and sectoring.
    How to answer

    • Concept of cell splitting to increase capacity
    • Diagram of split cells
    • Concept of sectoring with 120 deg antennas
    • Advantages: reduced interference, higher capacity
13. 7 Marks
    aExplain methods to reduce co-channel interference.
    How to answer

    • Define co-channel interference and C/I ratio
    • Methods: larger cluster size, sectoring, power control
    • Smart antennas and channel assignment
    • Effect on capacity trade-off
14. 7 Marks
    bExplain frequency division multiple access.
    How to answer

    • Principle of FDMA frequency division
    • Channel bandwidth and guard bands
    • Diagram of frequency allocation
    • Advantages, disadvantages and applications
15. 14 Marks
    Write short note on any two of following.

    1. a)Fading
    2. b)GSM radio sub system
    3. c)Frame structure
    How to answer

    • Select any two topics from fading, GSM radio subsystem, frame structure
    • Key definitions and diagrams for each
    • Types, components and functions
    • Applications and significance