using multple sim cards for the same arduino gsm shield where only one sim slot exists

Question

I have a aduino uno and a gsm arduino shield. I want to send sms with different gsm networks. Each at once. As an example if I sent "1" to arduino, it should send a sms to my mobile with the network "AT&T" and if I sent "2", a sms should come to my mobile with the network "Mobistar". There's only one sim slot in the gsm shield. How can I achive this?

Answer 1

Your options are basically:

1. Look for a single SIM that supports multiple operators - not available as far as I know. This is not a technical thing, it depends upon agreements between operators.

2. Have multiple GSM devices, each with its own SIM slot containing a SIM from a different operator (this is probably your best option if you're not planning to send a lot of SMSs).

3. Look for a commercial SMS gateway that can send to different operators - I don't know if any of them offer that service.

4. Look for multiple commercial SMS gateways that each send SMSs to a different operator (Note that using a commercial SMS gateway is the only realistic option if you're planning to send large numbers of SMSs).

5. Use a roaming SIM, that is to say a SIM from another country. Operators don't usually allow you to select another operator when you're using a SIM in its home country - you have to stay on the home network. But you generally get more choice when you're roaming. In this case, you would have to find all the available networks via AT commands (e.g.3GPP TS 27.007 section 7.3 AT+COPS), and choose the network that you want for the SMS. That may not be terribly reliable though - it depends a bit on how the SIM is set up. And of course you'd be limited to the number of SMSs that you could send via one SIM.

It depends a bit on your requirements - if it's just a demo, how many SMSs you want to send etc.