Open GSM modem

From Openmoko

Jump to: navigation, search

GSM is the mobile standard supported by the Neo1973.

The modem in the phone is not open source, it is talked to over a serial interface.

A number of applications could be made possible if the source was available to the modem. These include:

  • Moving some policy inside the modem, so that it could take a list of numbers to wake the CPU on, and a list of numbers to ignore. To reduce battery use.
  • Access to packet by packet signal strengths and timings to aid with positioning.


There is a fundamental problem.

GSM works so well because the towers are carefully planned. They are designed so they don't interfere with each other.

If nobody does anything bad, this all 'just works'.

However, if someone wrote a 'free local data' transmitter, which simply used the modem to send direct to another modem, it would jam a GSM channel. If you are not much further away from the tower than people making phone-calls, then your signal strength will be strong enough to knock 8-16 phone users off the channel.

These users may simply be able to redial, and they will get through.

On the other hand, it would only take a few users using this sort of software to completely prevent anyone from making phone calls in the area unless they were significantly closer to the tower than the users of this software.

This can be tens, or hundreds of square kilometers in rural areas.

Some of these calls will be emergency calls.

In addition and are examples of legislation, which makes sale of equipment able to change IMEI illegal. This would make it illegal to sell phones of this sort once the first one is misused.

See also

Personal tools