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androidsim-card
bdutta74
bdutta74

Reputation: 2860

Android Telephony - dual SIM versus single SIM with multiple IMSI

Mobile handsets can have dual SIMs, where each SIM (usually) has a single IMSI. However it is possible for a SIM card to have dual IMSI as well, and in fact IMSI that can be "configured on it" on-the-fly by operator. The latter mechanism is used for roaming scenarios, such as for business customers, where one (fixed) IMSI will be used by your home-country operator's phone number, and the other (flexible) IMSI that could be configured to visited-country operator's phone number (with whom your operator has a specific roaming arrangement). This way people can call you on either number, and you do not have to swap SIMs. Note that this was possible even before dual-SIM phones became relatively common.

For multi-SIM, I found some answers such as this one where one answer suggests using MultiSIM API (from 3rd party), and another answer suggests using the official supported API available since Android 5.1 (API level >22) or the unsupported TelephonyManager way from this answer (which I presume works for older API levels as well). However, it is not evident if those API's work for single SIM multi IMSI as well.

Unfortunately, I am yet to lay my hands on dual-IMSI SIM card to try this out. While I am trying to procure one, can anyone who has tried confirm or share findings ?

Upvotes: 2

Views: 1291

Answers (1)

QuickPrototype
QuickPrototype

Reputation: 883

I'm not exactly sure what the question is, however a single SIM will only ever have one active imsi. Yes SIM cards can can multiple imsi's and an operator can update the imsi. However a SIM will only have ONE active IMSI.

A SIM can only have one active IMSI due to the SIM specification which says a IMSI must be stored in file ID: 

3F00 (MF) -> 7F20 -> (DF_GSM) -> 6F07 (EF_IMSI).

A device (phone/modem) will request the IMSI from this file and only this file. if they were two "active" IMSI's no device currently would know where to find that IMSI without a firmware change.

Upvotes: 2

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