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CS718 – Wireless Networks

In CS718 Wireless Networks we have you covered with Digitized Past Papers From Fall of Mid Term and Final Term.

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    Q 1: Briefly note on BCH code and its working.  BCH … Discoverer: Bose, Chaudhuri and Hocquenghem.  Multiple error correcting codes  Generalization of Hamming Code.  Flexibility in choice of parameters: Block length, code rate
     For positive pair of integers m and t, a (n, k) BCH code has parameters:
    Block length: n = 2m – 1
    Number of check bits: n – k = 2t + 1
     Correct combinations of t or fewer errors  The generator polynomial can be constructed from the factors of (X
    2m-1 +1)
    Q 2: Write down the classes of A/Gb mode of GPRS.  Class A: MS can operate simultaneous packet switched and circuit switched services.  Class B: MS can operate either one at one time – Most common for handsets today.  Class C: MS can operate only packet switched services – e.g. Expansion cards for laptops. Q 3: How MULTIMEDIA further divides in UMATS types?
    Service classes in UMTS
     In 3G network, ME will be able to establish multiple connections simultaneously.  Network allows efficient cooperation between application with diverse quality of service
    requirements.  The quality can be defined by two main parameters
    Guaranteed and max bit rate possible (kbps)
    Permissible delay (ms)
    Based on the QoS criteria, multimedia services has been further classified
     Conversational: The most delay sensitive, e.g. applications video telephony, VoIP
     Streaming: Flow which is steady and continuous, it is server to user  Interactive: Web browsing is an example. A user may request timetables of buses, trains or
    flight schedule
     Background: Short messages, file transfer, ema
     Works in circuit switch mode.  Speed increased by allowing single user to use consecutive time slots in GSM standard
     Relaxes error control coding algorithms specified in GSM increasing data rate from 9.600 to
    14.400 Kbps  By using 4 slots, raw data rate of up to 57.6 kbps to individual user.  Ideal for dedicated streaming or real-time interactive web sessions
    Q 5: Write brief note on EDGE.  EDGE2.75G More advanced upgrade to 2G that requires addition of new hardware and
     Developed as a path to become eventual 3G high speed data access  New modulation 8-PSK in addition to GSM standard GMSK.  Allows nine different formats known as Multiple modulation and Coding Scheme (MCS)  Each MCS state may either use GMSK (low rate) or 8-PSK (high rate).  A family of MCS for each GSM slot and users can adaptively determine best MCS setting
     User start first with max error protection and max data rate until the link has unacceptable
    outage or delay
     By combining different channels (multi-carrier trans), EDGE provides upto several megabits
    per second data throughput. Q 6: Issues regarding handoff in interSystem.
    If a mobile moves from one cellular system to a different system controlled by a different MSC
    Issues to be addressed
    1. A local call becomes a long-distance call (roaming)
    2. Compatibility between two MSC must be determined
    3. Different systems have different policies and methods for managing handoff requests
    Q 7: Write about QoS profile in GPRS bearer
    QoS Profile for GPRS Bearers
    4 parameters:
    1. Service precedence: 3 classes
    2. Reliability parameter: 3 classes
    3. Delay parameters: 4 classes
    4. Throughput parameter: Maximum and mean bit rates
    QoS profile is included in Packet Data Protocol (PDP) context
    Negotiation managed through PDP procedures (activation, modification and deactivation)
    Q 8: Describe about Call routing in GSM network with Detailed diagram
    Frequent path breaks due to mobility
    High cost and time of deployment Quick and cost-effective deployment


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