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
    6
    0
    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

    Expert

    Feb 24, 2006
    10,152
    1,793
    I can sum it up in one word. Multiplexing
     
  3. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    145
    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).

    Dave
     
  4. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
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