This is not about how to use two SIM’s on an existing single SIM phone. For that, you need a double SIM adapter: it will look weird, hanging off your phone, but it can be hidden under a phone case. A double SIM adapter, however, allows you to use only one SIM at a time.
Another solution is buying a 2nd phone, or buying a double SIM one, which is:
— heavier
— more expensive
— less autonomous
— emitting more SAR
A dual SIM phone needs to have two transceivers: one for each SIM connection. It needs a bigger battery, which is going to empty faster anyways, so that both SIM’s can be active at any given time. The radiation value of a such phone is also higher. There’s a simple solution to these problems, but perhaps oversimplifying things for the customers makes less money, and that’s why it hasn’t been done yet.
Turning a single SIM phone into a multi-SIM one requires software modification, and a new SIM identification system. The SIM has an ID number (see card) that makes it unique to a network: the carrier assignes a phone number to that ID, and now the SIM has a phone number. When the client wants to change his phone number, for example, the carrier will assign a new one to that ID: a physical SIM change won’t be necessary.
An ID contains the following:
— country code
— carrier code
— SIM code
The carrier code connects the SIM to the right network, and the SIM code tells the network who you are.
Multiple SIM’s, same carrier
This version is the easiest to implement. The new type of ID should contain:
— country code
— carrier code
— SIM code
— account code array (e.g. A, B, C)
The SIM code tells the network who you are. But the account code tells which of your phone numbers you’d like to use when making a call (A, B, or C). When receiving a call, the network identifies you by the SIM code, and tells your phone which extension is solicited (A, B or C). Conference calling can be done in the carrier’s network and streamed to the client’s phone as one call (which I suppose already happens).
Multiple SIM’s, different carriers
In this case, the new ID type should contain:
— country code
— carrier code array (e.g. 1, 2, 3)
— SIM code
— account code array (e.g. A, B, C)
This version should be more difficult to implement, because the phone can register to a single network (it could register in all, but that’s a different story). A problem occurs when the client stays in network “1” and must receive a call (or make a call) on carrier “2”. But it’s not the solutions that are missing. It’s the will.
It’s just a matter of carriers agreements and network structuring.
Today I’ve read that a similar idea was patented in 2013, and implemented in Germany. I’ve registered mine on “Invent With Nokia” in 2015, as a draft. After they rejected my smart phone battery idea for not being novel, although I still think it was, I haven’t really felt encouraged to try again.
An 8er 