[UA] Our modern mobile world

[Myles Corcoran]

[Liam Routt looking for advice on mobile phones]

As as GSM phone software guy I thought I'd answer this one.

> 1. Person A calls Person B. Both have mobile phones. After the fact can a
>    suitably authorized person find out:
>      a) where person A was at the time of the call?
>      b) where person B was at the time of the call?
>      c) how long the call was?
>      d) who has such information? The company that serves person
>         A? Person B's company? Both? Someone else?
>      e) and what sort of authority is required for such information?
>      f) how accessible is such information to unauthorized people?

Yes to a, b and c. The service provider (France Telecom, Orange 
etc.) have the record of the duration of the call. It's used for 
billing, obviously. Depending on the country the police may also 
obtain this information. See your local laws for details. The 
info is probably well secured from unauthorized access, but I 
don't deal with the money and security side of things.

> 2. What sort of info about the calling party does a mobile phone have?
>      a) their number? any additional identifier?
>      b) their location? even in general terms (USA, France, or Alabama?)
>      c) what about for calls that are not answered? when the phone is off?
>         when the phone is on and you just don't pick up?
>      d) what about for outgoing calls you have made?

	With the right services (which you pay for in most cases) 
you get the caller's number, with the international prefix and 
provider's prefix, allowing you to identify both country and 
operator of origin. There's new recommendations coming in that 
will make it possible (for the police mainly) to pinpoint a 
mobile to within about 100 metres, depending on the cell size 
in your area. Less population density, lower accuracy. 
	For call screening the same applies for the caller's 
number. You can pay for a service to restrict your number from 
being presented to others with caller id, but that doesn't stop 
the police or other authorized authorities. If the phone is 
off there's little or no chance of you knowing who called, unless 
they leave a message on voice mail.

> 3. How trackable are mobile phones?
>      a) when they are on?
>      b) when they are off?
>      c) with or without the "mobile network's" help?

	While on, the mobile sends out a regular signal to 
the nearby Base Stations to check the status of the radio 
channel and to identify itself to the network. When they're 
off all the mobile network provider has is the last location 
(roughly) where the phone was on. With the network's help 
you can probably pin down a mobile handset to within a 
few hundred metres in an built up area, maybe to less than 
a kilometre in the countryside. 

> 4. Answering machine-style services. Are they common, or standard? What
>    info, if any, do they tell you about the caller? Can the network
>    provider find out more?

	Very common. It's a good way to ensure that the phone 
company gets money even when you don't actually get the call. 
They are essentially indistinguishable from a fixed network 
answering machine. Message, beep, leave your own message. If 
you have voice mail, the network provider already has a bunch 
of information about you and won't really get any more from 
your voice mail setup, except that you're willing to pay more 
for keeping in contact.

> 5. Do mobile phones work outside the area that they were purchased for (as
>    long as there is coverage by some network provider)? So if I buy a
>    phone to use in Chicago, can I use it freely in Boston, San Fran, and
>    Paris, Moscow and Taipei? Do I need to set such access up specially?

	National roaming, as it's called, works pretty well in 
most industrialized nations. Except, curiously, in the US. This 
is because of the difference in mobile standards. Europe and lot 
of Asia and Africa use GSM. The States uses CDMA. I don't know 
about Oz. National roaming isn't usually provided by default 
and many providers require you to have subscribed for several 
months before allowing nat. roaming. 
	Basically, a European handset and the right subscription 
should allow you to roam anywhere in Europe, and probably in 
a few of the Asian/African states. A US handset and subscription 
allows you to roam internally in the US (remember coverage is 
poor in the big open spaces) and wherever else CDMA is used 
(parts of China for example!)

> 6. Ceasing service. How easy is it to cut off a mobile user through the
>    service provider (ie. authorities tell the company to stop A from
>    making any calls)?
>      a) if A stays in the local area?
>      b) if A travels to another state?
>      c) if A goes to another country?
>      d) in any case, can A receive calls, even if calls out cannot be
>         made?

Dead simple. All calls incoming and outgoing can be blocked (except 
for emergency calls). A subscription can be modified to allow 
outgoing but no incoming and vice versa with a single keyboard 
issued command. This is regardless of location or roaming.
 
> Anything else I should know? :)

	Yup. If you're setting things in the near-future (i.e 
more than 18 months from now) the UMTS third generation mobile 
standard will be replacing GSM and CDMA. This is faster, more 
secure and more expensive (at first) than either of the 2nd 
gen systems. It's like them but with more bells and whistles 
and much better data connectivity. It will be a while before 
they achieve video phone capability but it's certainly on 
the cards.

	Hope this helped.

	Myles 

--
Myles Corcoran - 023 20469 (w) - 023 20481 (fax) - 021 4503904 (h)   
Alcatel Ireland Ltd., Bandon, Cork, IRELAND - myles at ck.cit.alcatel.fr
    "There is much pleasure to be gained from useless knowledge." 
                                              - Bertrand Russell

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