(keitai-l) Re: closing down cellphones in cinemas

From: Timothy J Mckinnon <mckint_at_ecomm.net.au>
Date: 07/02/02
Message-ID: <NEBBIECBEKIBPCKKLFMEEEHMCNAA.mckint@ecomm.net.au>
Then why does my Nokia interfere with my car sound system when the signal
gets weak buy making a curious clicking sound. I always thought that the
cellphone (GSM at least anyway) tried to handshake with the nearest cell by
transmitting, not just receiving. The cell has to know that it has a phone
in its *domain* so it can route calls to it. So the cell phone must tell the
nearest cell that it is available, and this is through the phone *pinging*
for a connection.

Am I right or not?


-----Original Message-----
From: keitai-l-bounce@appelsiini.net
[mailto:keitai-l-bounce@appelsiini.net]On Behalf Of Ben Hutchings
Sent: Monday, July 01, 2002 11:39 PM
To: keitai-l@appelsiini.net
Subject: (keitai-l) Re: closing down cellphones in cinemas

On Fri, 28 Jun 2002, Nick May wrote:

> http://news.bbc.co.uk/hi/english/sci/tech/newsid_2067000/2067672.stm
> Sorry - another link, about efforts to close down cellphones in cinemas
> and the like.
> When an incoming signal is very weak, cellphones presumably ramp up the
> power of their own signals. So if this tech. "half worked" it would lead
> to all the cellphones in the cinema blasting away on full power all
> trying to contact the nearest base station....
> What do cellphones do when the signal is non-existant? Do they  just put
> out a very low power signal? Or do they blast away?

If a handset loses the signal from its current cell without being
handed-off then it should presumably try to search for a new cell by
itself.  Until the handset has identified the frequencies, timing, etc.
used by the cell, it's quite useless for it to attempt to transmit
anything.  I don't think there's going to be any 'blasting away on full
power'.  (For GSM at least, handsets are not allowed to change power
level; the base station makes the decision.)  On the other hand, the base
station probably might well spend a while increasing signal power before
giving the handset up for lost.

(The process of searching for a new cell can apparently consume quite a
bit of power even though the transmitter isn't active.  My Motorola GSM
handset has various options for speed of search to allow the user to
trade-off battery life against speed of reconnection to a network.)

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Received on Tue Jul 2 07:29:06 2002