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 Forum index » House Training » HOWTO ( Solutions )
HOWTO get personal with your 3G (etc.) cellular modem
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dogle

Joined: 11 Oct 2007
Posts: 332

PostPosted: Sun 23 Feb 2014, 20:57    Post subject:  HOWTO get personal with your 3G (etc.) cellular modem
Subject description: - choose service, optimise signal strength etc.
 

- without wasting your time and money!

Communication with modems has been accomplished - since (almost) the days when they were driven by steam - via special character combinations known variously as e.g. 'AT codes' or 'Hayes strings'. It is very easy to use these, to your advantage, in Puppy .... if you know how.

In the following examples, it is assumed that Puppy has recognised your modem as /dev/ttyUSB0 (your mileage may vary, adjust the numeric if need be).

What cellular services can I pick up at my location?


- to find out which Internet Service Providers (ISPs) are within range, open a terminal (e.g. rxvt) and do-
Code:
modem-stats  -c "AT=COPS?" /dev/ttyUSB0

(include the quotes!)

- allow Puppy half a minute or so for scratting and sniffing; your modem will report all the services which it can 'see', each one in brackets with the following format:
(service status, numeric, e.g. 0=unknown, 1=available, 2=current, 3='forbidden'; abbreviated ISP identity; ?base station ID; service category, numeric, e.g. 0=GSM, 1='compact GSM', 2=UTRAN/3G).

Note that:

- you do not have to rush out and buy a set of SIMcards to see what is available! The AT=COPS? should tell you anyway, even if you are using a specific, old, time-expired SIMcard in your device, and even if your modem thought it was "locked" to a particular outfit.

- the string AT=COPS? will report services even if their signal is too weak to be useful for practical purposes. To find out what signal strength you can pick up from a given ISP, read on ....

What sort of signal can I get from that ISP?

To 'target' the signal from a particular ISP, you will need to have inserted a SIMcard associated with that ISP .... but, as before, don't waste your money whilst trying find out what's available by buying a new SIMcard, unless you must ... even a time/credit-expired voice (telephone) SIM for that provider's local service should suffice to check your signal strength.

- in the terminal, do-
Code:
modem-stats  -c  "AT+CSQ"  /dev/ttyUSB0

AT+CSQ will swiftly tell you the score, e.g. +CSQ: 18, 99

Here, the trailing 99 is just a dummy number indicating that there is no info on speed/bandwidth .... the leading number tells you the signal strength. Here is a rough guide:-
Code:

1      -111 dBm     (very very weak)
5       -103 dBm
10       -93  dBm
15        -83  dBm
20       -73  dBm
25        -63  dBm
30       -53  dBm   (super strong)

It is suggested that a signal strength in the range -75 to -85 dBm, i.e. the +CSQ -reported numbers 14 to 17, should be sufficient for a reasonably reliable data connection. It may not be worth striving for anything better than -60 dBm, say +CSQ -reported 26, because the base station may start to wind down transmit power if it thinks things are that good.

Note that there is no need to transmit ISP 'phone numbers', passwords and stuff for the purpose of running these tests, because Puppy is just sniffing the signals rather than establishing a connection to a service.

AT+CSQ is very useful, also, for experimenting to find the optimal position for your device, e.g. the 'sweet spot' for your dongle within your den which offers the best signal.

Don't forget that, if you get bored with repeatedly shoving out AT codes manually on the command line as above, PupDial can do this for you very nicely; f'rinstance, I keep the line
Code:

Init6 = AT+CSQ

in my /etc/wvdial.config, so that PupDial reports the signal strength whenever I connect.

Although much of this 'gen is available elsewhere on the forum, it is in bits and hard to find, so I thought it worth trying to pull it together in this HOWTO ..... but I am so far only just scratching the surface of the power which AT codes can place at your fingertips (there are so many of them!) .... if you know how to use them. Any corrections and contributions are most welcome, especially if you have succeeded in using any particular AT code to sort out a problem.
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mister_electronico


Joined: 20 Jan 2008
Posts: 660
Location: Asturias_ España

PostPosted: Sun 27 Jul 2014, 16:45    Post subject: Thanks for this post  

Thanks for this post is very interesting, I'll try in my mobile phone.

See you.
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mister_electronico


Joined: 20 Jan 2008
Posts: 660
Location: Asturias_ España

PostPosted: Sun 27 Jul 2014, 16:50    Post subject: Interesting  

For me it is interesting to remote automatism, able to send messages via GSM, and control of distant automatons.

Thank you.
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nic007

Joined: 13 Nov 2011
Posts: 740

PostPosted: Tue 29 Jul 2014, 01:46    Post subject:  

All good tips. Now that we're talking 3G cellphone modems, I strongly suggest trying Opera Mini as your browser like I do. You will need java installed and an emulator (I use microemulator) to run it on your desktop/laptop.
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dogle

Joined: 11 Oct 2007
Posts: 332

PostPosted: Tue 19 Aug 2014, 15:24    Post subject:  

Thanks nic007 (and my apologies for my late reply).

Could you perhaps expand your kind suggestion a little - e.g. what particular advantages do you find with Opera Mini, in the cellular context, (and why the Java install requirement)?
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nic007

Joined: 13 Nov 2011
Posts: 740

PostPosted: Tue 19 Aug 2014, 19:20    Post subject:  

dogle wrote:
Thanks nic007 (and my apologies for my late reply).

Could you perhaps expand your kind suggestion a little - e.g. what particular advantages do you find with Opera Mini, in the cellular context, (and why the Java install requirement)?

Hi Dogle, I just put out the suggestion as a matter of interest.. Opera Mini is a Java application, therefor you need JRE. With Opera Mini the data is compressed through Opera Mini's proxy server in real time. You can save up to 90% on data usage which obviously has a data cost advantage. It's fast and great for general browsing, I use it every day (on my computer).
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donkeymilk1

Joined: 02 Oct 2014
Posts: 11

PostPosted: Thu 02 Oct 2014, 19:05    Post subject:  

Thanks for interseting info,dogle .

would opera mini work on a pc ?

or is there something similar that saves on data use.
and can be run from pc.

i use a 3g t-mobile dongle ,i've got used to the data allowance dissappearing in 30mins after topping up £15.

so it would be nice to have it last a bit longer.
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nic007

Joined: 13 Nov 2011
Posts: 740

PostPosted: Thu 02 Oct 2014, 20:24    Post subject:  

donkeymilk1 wrote:
Thanks for interseting info,dogle .

would opera mini work on a pc ?

or is there something similar that saves on data use.
and can be run from pc.

i use a 3g t-mobile dongle ,i've got used to the data allowance dissappearing in 30mins after topping up £15.

so it would be nice to have it last a bit longer.

Yes. You require Java Runtime Environment, an emulator (I use microemulator) and Opera Mini browser. Advantages - Great for general browsing. You save a lot on data as the data is compressed by Opera Mini's proxy servers and it's very fast. Mobile versions of web pages (if available) are loaded by default which saves data. Negatives - You can't watch videos. There is a limit to the size of a web page you can load (you will find that when the web page is very big, the text is generally loaded but not all the images).

Another alternative is to use an HTML only browser like Dillo. Java will not be needed and you will save on data usage in comparison to using one of the large browsers. Should also be fast. You won't be able to watch videos
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