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.)
Received on Mon Jul 1 17:56:11 2002