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Data transmission in Mobile phones

Discussion in 'General Electronics Chat' started by sagarin, Mar 29, 2007.

  1. sagarin

    Thread Starter New Member

    Mar 27, 2007
    Wishes to all..,

    How is it possible to have zero cross talks in mobile phones besides a large number of calls a a time? How does the call reach the particular number when dialled?
  2. Papabravo


    Feb 24, 2006
    I can sum it up in one word. Multiplexing
  3. Dave

    Retired Moderator

    Nov 17, 2003
    There have been several types of Multiplexing used in mobile phone communications:

    1st Gen used Frequency Division Multiplexing - simple, and had a long symbol duration making it less susceptable to inter-signal interferences; however had a low bandwidth efficiency (expensive) and suffered from an issue know as the near-far-problem which caused severe near channel interference.

    2nd Gen uses Time Division Multiplexing - simple in terms of time-slot allocation and power control at the base-station; however had low symbol duration makin it sensitive to inter-signal interference, required guard bands wasting bandwidth and there is a hardware overhead administrating the system timing (which becomes an increasing problem as more people use the network).

    3rd Gen uses Code Division Multiplexing - robust system that is resistant to frequency sensitive fading, has flexible and high date rates, and is less sensitive to synchronisation requirements; however this comes at the cost of increased system complexity and bandwidth (which as you should know is very expensive).

  4. mrmeval

    AAC Fanatic!

    Jun 30, 2006