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why cellular phone are called cellular

Discussion in 'Electronic Basics' started by [email protected], Nov 27, 2005.

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  1. Guest

    i want to know why celllular phone are called so and other details like
    what is bluetooth, gprs gsm there advantages and disadvantages
     
  2. Christian S.

    Christian S. Guest

    They are called such because they are used within a cellular network
    http://en.wikipedia.org/wiki/Cellular_network

    Chris
     
  3. There were mobile, and even portable, phones before cellphones came along.
    But it meant connecting with one (or a few) central stations (and usually
    required an operator at that station to do the actual dialing), and relatively
    high power was needed. Only a handful of frequencies were assigned to
    mobile phone use, and only one person could use a given frequency at a time
    in most locations. Thus it could never be a system for the masses, and
    the cost was quite high.

    Cellphones change all that. They got a slew of frequencies. More important,
    the "base stations" are spread out all over town. This means power levels
    are much lower, at the base and in the cellphone. If you're in area A,
    someone across town in area X can use the same frequency because the
    frequencies are high enough in the radio spectrum so they won't travel far,
    and the power levels additionally limit the range of the signals. This means
    the frequencies can be reused throughout a city, just making sure that
    adjacent cell "bases" don't use the same ones. As someone moves along,
    they will move into a new cell, and the network will automatically switch
    them over to the next one (ie change the frequency, and pass them on to
    the next cell, so the user never notices that anything has changed. The
    cellphones are a lot "smarter" than the old mobile phones, that had
    nothing but the radio transmitter and receiver.

    Michael
     
  4. Kingcosmos

    Kingcosmos Guest

    <<If you're in area A,
    someone across town in area X can use the same frequency because the
    frequencies are high enough in the radio spectrum so they won't travel
    far,
    and the power levels additionally limit the range of the signals.

    Maybe I misunderstood, but this seems to imply that higher frequencies
    have inherently short distances in which they travel. All things equal
    (environmental conditions, amplitude, power) does a low frequency
    physically travel further than a high frequency? I would figure it
    would be signal strength at distance X that comes into play. Can you
    comment?
     
  5. It involves refraction. Lower frequencies (longer wavelength) pass
    around obstacles that are much smaller than their wavelength with
    little loss or reflection. When a wave encounters an object larger
    than its wavelength, it tends to be absorbed by the object, or
    reflected by it, or some combination of those two. Little of it will
    continue on behind the obstacle.

    So, going straight up, the distance capability is pretty independent
    of wavelength, except for atmospheric absorption and reflection at
    some resonance frequencies. But along the ground, where the waves
    propagate through trees, buildings and lots of other obstacles, the
    short wavelengths get lost much closer to the source.
     
  6. quietguy

    quietguy Guest

    You would find the site 'howstuffworks' very helpful for these sort of
    questions

    David
     
  7. Kingcosmos

    Kingcosmos Guest

    It involves refraction. Lower frequencies (longer wavelength) pass
    The reason I asked is that my college professor told us a story
    concerning Best Buy 'experts' and cordless phones. He had asked one of
    the associates about the 5.8 GHz phones and he was told that they can
    'communicate further' because of the higher frequency when compared to
    the 2.4 GHz phones. He told us that 'that is not true' but never went
    into detail about it. By the time I got around to figure out why this
    is so a semester later he had moved on.

    I figured it would have something to do with the atmosphere, obstacles,
    clarity, bandwidth, and of commerical reasons for the increasing
    frequency range. Thanks for the explanation.
     
  8. Jasen Betts

    Jasen Betts Guest

    lower frequencies tend to pass arround and through obstacles, higher
    frequencies thend to be absorbed or reflected by them.


    Bye.
    Jasen

    visible light is strictly line of sight :)
     
  9. Ryan

    Ryan Guest

    i want to know why celllular phone are called so

    Because if you map the coverage areas of multiple transceiver towers,
    their ranges are each adjoining roundish objects resembling cells (such
    as organism tissues under a microscope).

    http://www.itu.int/osg/spu/ni/images/mtso.gif
     
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