Tracking Device

[KaRyu]

I have a question here.

Does a mobile phone emits a certain kind of signal when it sends text messages? If it does, is it possible to track it?

 

[Nigel Goodwin]

I have a question here.

Does a mobile phone emits a certain kind of signal when it sends text messages? If it does, is it possible to track it?

A mobile phone emits certain signals regularly anyway, you don't need to send a text message - and obviously it could be tracked if required.

 

[KaRyu]

yeah i know that.
I want to know if it emits a different kind of signal when it sends text messages. I want to track a phone which sends a text message.

 

[picbits]

You can track any mobile phone when it is on but depending on your country will depend on what services are offered. There are some companies which use triangulation methods between control towers to track mobile phones to within 20-30 meters.

If you're trying to build something yourself we'll need to know your level of electronic and RF experience.

 

[KaRyu]

You can track any mobile phone when it is on but depending on your country will depend on what services are offered. There are some companies which use triangulation methods between control towers to track mobile phones to within 20-30 meters.

If you're trying to build something yourself we'll need to know your level of electronic and RF experience.

I am currently an Electronics Engineering student and is looking for a thesis topic.

I want to build an alarm system which will activate when a text message is being sent in a certain location(small radius only). After activating, the device will try to pinpoint the phone's location. It's application is for security in a classroom setting(especially in exams).

 

[picbits]

You will find that a text message will generate a certain amount of RF energy at a certain range of frequencies but apart from that you'll have great trouble to try and distinguish the difference between a text message or a normal phone registration. Maybe a text message would have a longer transmission period than a registration signal ? That would be up to you to investigate.

I'd use an array of tuned and highly directional antennas in two corners of the room. You need to look at 90 degrees from each corner maybe with 5 or 6 antennas per corner and a device to measure the signal strength of each antenna. From this you should be able to triangulate the position of the phone based on the two strongest antenna signals.

That is assuming of course only one phone is used at a time.

 

[KaRyu]

You will find that a text message will generate a certain amount of RF energy at a certain range of frequencies but apart from that you'll have great trouble to try and distinguish the difference between a text message or a normal phone registration. Maybe a text message would have a longer transmission period than a registration signal ? That would be up to you to investigate.

I'd use an array of tuned and highly directional antennas in two corners of the room. You need to look at 90 degrees from each corner maybe with 5 or 6 antennas per corner and a device to measure the signal strength of each antenna. From this you should be able to triangulate the position of the phone based on the two strongest antenna signals.

That is assuming of course only one phone is used at a time.

Thanks.
Is it a possible thesis topic?

 

[picbits]

Thanks.
Is it a possible thesis topic?

That is up to you to decide.

 

[alec_t]

To help you decide whether this is suitable for a thesis topic a preliminary experiment or two might be useful. Can you detect the signal from a phone? Can you demodulate it? Can you identify text-indicative patterns in the demodulated signal?

 

[KaRyu]

To help you decide whether this is suitable for a thesis topic a preliminary experiment or two might be useful. Can you detect the signal from a phone? Can you demodulate it? Can you identify text-indicative patterns in the demodulated signal?

That is my problem. I don't have enough time to conduct research and experiment to test my ideas.

 

[davenn]

That is my problem. I don't have enough time to conduct research and experiment to test my ideas.

then maybe you should be choosing a different thesis topic ?


Dave

 

[alec_t]

I don't have enough time to conduct research and experiment to test my ideas.

Surely the experimenting is the whole point of a thesis?

 

[KaRyu]

Surely the experimenting is the whole point of a thesis?

Uhmm, yeah that's true..
What I'm concerned about is if it fails..

 

[alec_t]

What I'm concerned about is if it fails..

Conducting experiments to show that something doesn't work can be just as valuable to science as showing that it does work, even if it's less satisfying to the experimenter. If you have concerns about that, discuss it with your tutor/professor or whoever will be assessing your thesis.

 

[RadioRon]

If the primary application is during an exam, i would think that any transmission from a student, whether it be voice, text message, or data would be bad. So why focus on text messages, why not just look for any phone traffic? At the risk of answering my own question, beware that phones may transmit automatically just to stay registered or to roam on a system so there are times when the phone will transmit even when you are not talking or texting or 'webbing'.

 

[KaRyu]

If the primary application is during an exam, i would think that any transmission from a student, whether it be voice, text message, or data would be bad. So why focus on text messages, why not just look for any phone traffic? At the risk of answering my own question, beware that phones may transmit automatically just to stay registered or to roam on a system so there are times when the phone will transmit even when you are not talking or texting or 'webbing'.

Hmm. You have a point. I'm really just confirming if there is a possibility of sensing signals of mobile phones and distinguishing what that signal is for.

 

[alec_t]

It's possible; the telcos must be doing it all the time . But it would involve a lot of computation for pattern recognition.

 

[cowboybob]

I am currently an Electronics Engineering student and is looking for a thesis topic.

I want to build an alarm system which will activate when a text message is being sent in a certain location(small radius only). After activating, the device will try to pinpoint the phone's location. It's application is for security in a classroom setting(especially in exams).

Is this for a BA, MA or PHD level thesis? Only reason I ask is it might matter what degree of complexity is required. Perhaps the following might be acceptable:

First off, it would seem to me that it would be reasonable to require that ALL cell phones be turned off for an exam.

That being the case, then you could design a receiver system to detect just the presence of a cell phone signal.

An array (or perhaps a single) antenna [stub, parabola, whatever]), might be strategically placed in the class room at, say, the center of the ceiling facing down. It (and its receiver system) could be de-tuned (and isolated) to limilt its range, and yet capture any cell phone emmissions.

That would be a sufficient indication of possibly nefarious use and would avoid any accusations of "spying" on a student's personal comms (which are being spyed on anyway, just not by you ).

<EDIT> Of course, YOUR cell would have to be off as well...

Then again, the idea might require a Faraday cage around the whole classroom, which might make the idea ridiculous. Be worth a shot, though, I'd think. Signal strength IS a factor of distance from the source.<EDIT/>

 

[KaRyu]

Is this for a BA, MA or PHD level thesis? Only reason I ask is it might matter what degree of complexity is required. Perhaps the following might be acceptable:

First off, it would seem to me that it would be reasonable to require that ALL cell phones be turned off for an exam.

That being the case, then you could design a receiver system to detect just the presence of a cell phone signal.

An array (or perhaps a single) antenna [stub, parabola, whatever]), might be strategically placed in the class room at, say, the center of the ceiling facing down. It (and its receiver system) could be de-tuned (and isolated) to limilt its range, and yet capture any cell phone emmissions.

That would be a sufficient indication of possibly nefarious use and would avoid any accusations of "spying" on a student's personal comms (which are being spyed on anyway, just not by you ).

<EDIT> Of course, YOUR cell would have to be off as well...

Then again, the idea might require a Faraday cage around the whole classroom, which might make the idea ridiculous. Be worth a shot, though, I'd think. Signal strength IS a factor of distance from the source.<EDIT/>

It's for BA. Maybe a cellphone signal detector would do it. I made things complicated .
But I want to build not only a device that can detect but also pinpoint it. Thanks

 

[cowboybob]

It's for BA. Maybe a cellphone signal detector would do it. I made things complicated .
But I want to build not only a device that can detect but also pinpoint it. Thanks

(My emphasis)

Well, that takes the concept to a much more difficult level. And I would think a level just about un-doable, if I'm understanding what a BA level exercise of this sort would require.

It would mean not just detecting the signal, but the means to decode and identify the cell number (or other identifying data). And that would require you knowing ALL the cell data particulars of ALL the students taking the exam. On what grounds would you have the legal right to acquire that information?

Or even more difficult, extract the exact location of the phone (by triangulation or whatever means?) in a very small, confined and perhaps confusing setting.

I would think that the task as I described would be difficult enough and, if achieved, be more than adequate for an A+ for the thesis and its resolution.

If a single cell signal were detected I'd think that would be sufficient to stop the test taking for ALL students and try again from scratch with a new test.

A draconian solution, but I'm pretty sure the students would get the picture and self-police to avoid that scenerio again.

I'm "old school": other than a simple calculator, NO electronics of any sort should be allowed in exams. While being able to find an answer is laudable (since that implies at least an understanding of the question asked), knowing the answer is the real test.