> In my case, however, I have to determine my geographic
> location independently of GPS. All I need to do is to relate
> a GSM tower's cell ID to a location very roughly. But even
> that rough tower location data seems to be unavailable.
I was thinking that you might be able to map the locations for
yourself as a separate exercise, prior to your implementing
your proposed main system. This would involve writing an
additional purpose-built application to initially correlate
GPS, cell ID and TA data as a foundation for the real
application.
How feasible this is would depend on the geographical area you
want to cover. Obviously, covering a significant part of a
country the size of the US in this way would be completely out
of the question (except for a large organization like google).
> I assume a way around this would be to purchase an API from
> every service provider, but this involves considerable
> expense, and there is no assurance that all providers would be
> willing to do this.
>
> So ONLY the network service providers can sell tower-based
> geo-location services (ie - triangulation) because they alone
> have the tower location data?
I agree that the secrecy is likely motivated by purely
commercial concerns.
Yep, it would be a huge job to map (and then keep updated) the towers
ourselves because we need to be operable throughout the U.S. But thank you
for all the good info, John. I've learned a lot!
Henry
"John Henderson" <jhenRemoveThis@talk21.com> wrote in message
news:67k4b0F2omag7U1@mid.individual.net...
> Henry VIII wrote:
>
>> In my case, however, I have to determine my geographic
>> location independently of GPS. All I need to do is to relate
>> a GSM tower's cell ID to a location very roughly. But even
>> that rough tower location data seems to be unavailable.
>
> I was thinking that you might be able to map the locations for
> yourself as a separate exercise, prior to your implementing
> your proposed main system. This would involve writing an
> additional purpose-built application to initially correlate
> GPS, cell ID and TA data as a foundation for the real
> application.
>
> How feasible this is would depend on the geographical area you
> want to cover. Obviously, covering a significant part of a
> country the size of the US in this way would be completely out
> of the question (except for a large organization like google).
>
>> I assume a way around this would be to purchase an API from
>> every service provider, but this involves considerable
>> expense, and there is no assurance that all providers would be
>> willing to do this.
>>
>> So ONLY the network service providers can sell tower-based
>> geo-location services (ie - triangulation) because they alone
>> have the tower location data?
>
> I agree that the secrecy is likely motivated by purely
> commercial concerns.
>
> John
>John, that was extremely helpful. Thank you very much.
>
>One final question, that I now realize I should have asked earlier but
>didn't think it would be an issue.
>
>The purpose of obtaining the cell ID is so that we can determine approximate
>location of the tower and our client connected to it. I was just told,
>however, that the networks keep tower locations secret. If that's true we
>would be unable to determine tower location even if we have the cell ID. Do
>you know if this is the case?
I don't think they advertise them, but most cells towers are pretty
ugly looking things. In addition you get the distance from the tower
from the timing advance. So while they don't advertise the location,
the actual locations are in fact, hard to hide.
>
>Henry.
>
>
>
>"John Henderson" <jhenRemoveThis@talk21.com> wrote in message
>news:67hp92F2nuafjU1@mid.individual.net...
>> Henry VIII wrote:
>>
>>> We are interested in knowing which cell tower we are connected
>>> to, just prior to initiation of the GPRS session. Connection
>>> will be telemetry data, no voice. The mobile laptop with GPRS
>>> card will be camped on a cell site but not interacting with
>>> it. Then our server will attempt to initiate a connection to
>>> it. The GPRS network will find our laptop. Our laptop needs
>>> to know at that time (or immediately before) which cell site
>>> it is connected to so it can report that in its response back
>>> to the server. We prefer connections to be TCP-IP rather than
>>> circuit-switched. Does all this sound possible?
>>
>> Assuming your modem card supports the necessary commands, this
>> will be easy. Below is an annotated log of a session with a
>> Siemens S55 phone. I'll start by using "AT+CREG?" to ask about
>> phone registration status.
>>
>> AT+CREG?
>> +CREG: 0,1
>>
>> OK
>>
>> I'm now changing the "+CREG" behaviour to report cell ID as
>> well, and also give me unsolicited results. By "unsolicited
>> results" I mean that the phone will report all changes of cell
>> ID automatically, when they happen, without my entering any
>> more commands.
>>
>>
>> AT+CREG=2
>> OK
>>
>> I'll ask again about registration status, and this time the LAC
>> and cell ID will be reported as well.
>>
>> AT+CREG?
>> +CREG: 2,1,"1030","639E"
>>
>> OK
>>
>> LAC (location area code) is 1030 hex (4144 decimal), and cell ID
>> is 639E hex (25502 decimal).
>>
>>
>> +CREG: 1,"1030","1401"
>>
>> The above is an unsolicited result code, showing me that the
>> phone has now camped on another cell (same LAC, but cell ID is
>> now 5151 decimal).
>>
>> I'll now ask which network I'm using. This will show my SIM's
>> home network, because the second argument in the "+CREG:"
>> result above, "1", says that the phone is currently registered
>> on the home network (rather than roaming).
>>
>> AT+COPS?
>> +COPS: 0,0,"Telstra"
>>
>> OK
>>
>> Now I want to see the registered network in numeric format, so
>> I'll ask for that.
>>
>> AT+COPS=0,2
>> OK
>> AT+COPS?
>> +COPS: 0,2,"50501"
>>
>> OK
>>
>> The operator part of the result consists of a 3-digit country
>> code "505" (MCC = Australia), and a 2-digit network code within
>> that country (MNC = Telstra). Note that some countries (North
>> America) use a 3-digit MNC as well as a 3-digit MCC).
>>
>> The reason I'm showing the MCC + MNC detail is that the cell ID
>> is only guaranteed to be absolutely unique if it consists of
>> the whole MCC + MNC + LAC + ID string, eg "505 01 1030 639E"
>>
>> +CREG: 1,"1030","639E"
>>
>> That was another unsolicited result showing that the phone
>> changed cell again.
>>
>> Now I'll ask the phone to scan all possible channels (takes a
>> while) and give me a list of all visible carriers.
>>
>> AT+COPS=?
>> +COPS: (2,"Telstra",,"50501"),(3,"vodafone
>> AU",,"50503"),(3,"YES OPTUS",,"50502)
>>
>> OK
>>
>>> Can you refer me to a Website where this information is
>>> available? We'll need to write the S/W to get the cell site
>>> ID from the card. We'll also need to be able to do a lookup
>>> of the cell site ID to determine its physical location.
>>
>> Any version of GSM 07.07 (or the later 2G/3G replacement, 3GPP
>> 27.007) will give you the full syntax of the above commands.
>> They're widely available on the net, including free official
>> downloads from www.etsi.org or www.3gpp.org
>>
>> John
>
Mobile Laptop on EDGE/GPRS
Linear Mode
