| Author |
Message |
neeraj_indian007@yahoo.co
Guest
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 Posted:
Sun Nov 27, 2005 9:35 am Post subject:
why cellular phone are called cellular |
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i want to know why celllular phone are called so and other details like
what is bluetooth, gprs gsm there advantages and disadvantages
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Christian S.
Guest
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| Posted:
Sun Nov 27, 2005 9:35 am Post subject:
Re: why cellular phone are called cellular |
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On 27 Nov 2005 00:32:50 -0800, "neeraj_indian007@yahoo.co.in"
<neeraj_indian007@yahoo.co.in> wrote:
| Quote: | i want to know why celllular phone are called so and other details like
what is bluetooth, gprs gsm there advantages and disadvantages
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They are called such because they are used within a cellular network
http://en.wikipedia.org/wiki/Cellular_network
Chris |
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Michael Black
Guest
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| Posted:
Sun Nov 27, 2005 5:35 pm Post subject:
Re: why cellular phone are called cellular |
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"neeraj_indian007@yahoo.co.in" (neeraj_indian007@yahoo.co.in) writes:
| Quote: | i want to know why celllular phone are called so and other details like
what is bluetooth, gprs gsm there advantages and disadvantages
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
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Kingcosmos
Guest
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| Posted:
Mon Nov 28, 2005 12:48 am Post subject:
Re: why cellular phone are called cellular |
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<<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? |
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Kingcosmos
Guest
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| Posted:
Mon Nov 28, 2005 1:35 am Post subject:
Re: why cellular phone are called cellular |
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| Quote: | 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.
|
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. |
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quietguy
Guest
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| Posted:
Mon Nov 28, 2005 1:35 am Post subject:
Re: why cellular phone are called cellular |
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You would find the site 'howstuffworks' very helpful for these sort of
questions
David
"neeraj_indian007@yahoo.co.in" wrote:
| Quote: | i want to know why celllular phone are called so and other details like
what is bluetooth, gprs gsm there advantages and disadvantages |
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John Popelish
Guest
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| Posted:
Mon Nov 28, 2005 1:35 am Post subject:
Re: why cellular phone are called cellular |
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Kingcosmos wrote:
| Quote: | 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?
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. |
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Jasen Betts
Guest
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| Posted:
Tue Nov 29, 2005 2:05 pm Post subject:
Re: why cellular phone are called cellular |
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On 2005-11-27, Kingcosmos <waynelittle@sbcglobal.net> wrote:
| Quote: | If you're in area A,
|
| Quote: | 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?
|
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 :) |
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Ryan
Guest
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| Posted:
Mon Dec 05, 2005 8:14 am Post subject:
Re: why cellular phone are called cellular |
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| Quote: | i want to know why celllular phone are called so
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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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