Android Telephony - dual SIM versus single SIM with multiple IMSI

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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 ?

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androidsim-card
Do you have a reference that a single SIM can have multiple IMSI? AFAIK SIM card can have only one IMSI. The procedure that you are descirbing is done by the foreign mobile company, by entering the visitor SIM's details into their HLR, not by assigning a second IMSI to the same SIM. - TDG
Don't have the specifications, although I did find few patent filings on the topic. However this has apparently quite common especially for M2M MVNOs. Here is one brochure that mentions it: eseye.com/wp-content/uploads/… - bdutta74
See this (slideshare.net/ikwe22/…) slide#35, i.e. the UICC cards can have multiple applications, even of same type. This means that a sing UICC card can have multiple SIM and USIM applications, each with it's unique IMSI. ETSI TS 122.101 seems to cover this. - bdutta74
Very interesting. Thanks for the link. - TDG
What is the question? - QuickPrototype

1 Answers

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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.