A subscriber identity module or subscriber identification module (SIM) on a removable SIM card securely stores the service-subscriber key (IMSI) used to identify a subscriber on mobile telephony devices (such as mobile phones and computers). The SIM card allows users to change phones by simply removing the SIM card from one mobile phone and inserting it into another mobile phone or broadband telephony device.
A SIM card contains its unique serial number, internationally unique number of the mobile user (IMSI), security authentication and ciphering information, temporary information related to the local network, a list of the services the user has access to and two passwords (PIN for usual use and PUK for unlocking).
SIM cards are available in three standard sizes. The first is the size of a credit card (85.60 mm × 53.98 mm x 0.76 mm). The newer, most popular miniature version has the same thickness, but has a length of 25 mm and a width of 15 mm, and has one of its corners truncated (chamfered) to prevent misinsertion. The newest incarnation known as the 3FF or micro-SIM has dimensions of 15 mm × 12 mm. Most cards of the two smaller sizes are supplied as a full-sized card with the smaller card held in place by a few plastic links; it can easily be broken off to be used in a device that uses the smaller SIM.
The first SIM card was made in 1991 by Munich smart card maker Giesecke & Devrient, who sold the first 300 SIM cards to Finnish wireless network operator Radiolinja.
Smart card technology
There are three operating voltages for SIM cards: 5 V, 3 V and 1.8 V (ISO/IEC 7816-3 classes A, B and C respectively). The operating voltage of the majority of SIM cards launched before 1998 was 5 V. SIM cards produced subsequently are compatible with 3 V and 5 V or with 1.8 V and 3 V.
A W-SIM is a SIM card that incorporates core cellular technology in the card itself.
A virtual SIM is a mobile phone number provided by a mobile network operator that does not require a SIM card to terminate phone calls on a user's mobile phone.
Features added in later releases
The specification that standardized the micro-SIM form factor continues to evolve. Some features introduced recently include:
* a micro-SIM form factor
* allow for multiple simultaneous applications accessing the card through logical channels;
* introduce mutual authentication as a way to eliminate carrier spoofing by allowing the SIM card to authenticate the cell tower to which it is connecting;
* add a new PIN protection with hierarchical PIN management with a universal PIN, an application PIN and a local PIN; and
* expand the phonebook storage of the SIM card with entries for email, second name, and groups.
Card sizes
SIM cards were first made the same size as a credit card (85.60 mm × 53.98 mm × 0.76 mm). The development of physically smaller mobile devices prompted the development of a smaller SIM card, the mini-SIM card. Mini-SIM cards have the same thickness as full-size cards, but their length and width are reduced to 25 mm × 15 mm.
The mini-SIM card has the same contact arrangement as the full-size SIM card and they are normally supplied within a full-size card carrier, attached by a number of linking pieces. This arrangement (defined in ISO/IEC 7810 as ID-1/000) allows for such a card to be used in a device requiring a full-size card, or to be used in a device requiring a mini-SIM card after cleanly breaking the scorings manufactured in the outline of a mini-SIM card.
Even smaller device sizes have prompted the development of a yet smaller card size, the 3FF card or micro-SIM. Micro-SIM cards have the same thickness and contact arrangement again, but the length and width are further reduced to 15 mm × 12 mm. The specifications for the 3FF card or micro-SIM also include additional functionality beyond changing the physical card size.
Development of the micro-SIM
The micro-SIM was developed by the European Telecommunications Standards Institute along with SCP, 3GPP (UTRAN/GERAN), 3GPP2 (CDMA2000), ARIB, GSMAssociaton (GSMA SCaG and GSMNA), GlobalPlatform, Liberty Alliance, and the Open Mobile Alliance (OMA) for the purpose of fitting into devices otherwise too small for a mini-SIM card.[2][3]
The form factor was mentioned in the Dec 1998 3GPP SMG9 UMTS Working Party, which is the standards-setting body for GSM SIM cards,[4] and the form factor was agreed upon in late 2003.[5]
The micro-SIM was created with backwards compatibility in mind. The major issue with backwards compatibility was the contact area of the chip. Retaining the same contact area allows the micro-SIM to be compatible with the previous, larger SIM readers through the use of plastic cutout surrounds. The SIM was also designed to run at the same speed (5 MHz) as the previous version. The same size and positions of pins resulted in numerous "How-to" tutorials and YouTube video with detailed instructions how to cut a mini-SIM card to micro-SIM size with sharp knife or scissors. These tutorials became very popular among first owners of iPad 3G after its release on April 30, 2010 and iPhone 4 on June 24, 2010.
The chairman of EP SCP, Dr. Klaus Vedder, said
"With this decision, we can see that ETSI has responded to a market need from ETSI customers, but additionally there is a strong desire not to invalidate, overnight, the existing interface, nor reduce the performance of the cards. EP SCP expect to finalise the technical realisation for the third form factor at the next SCP plenary meeting, scheduled for February 2004."
Usage in mobile phone standards
The use of SIM cards is mandatory in GSM devices. The equivalent of a SIM in UMTS is called the Universal Integrated Circuit Card (UICC), which runs a USIM application, while the Removable User Identity Module (R-UIM) is more popular in CDMA-based devices e.g. CDMA2000. The UICC is still colloquially called a SIM card. Many CDMA-based standards do not include any removable card, and the service is bound to a unique identifier contained in the handset itself.
The satellite phone networks Iridium, Thuraya and Inmarsat's BGAN also use SIM cards. Sometimes these SIM cards work in regular GSM phones and also allow GSM customers to roam in satellite networks by using their own SIM card in a satellite phone.
The SIM card introduced a new and significant business opportunity of mobile telecoms operator/carrier business of the mobile virtual network operator (MVNO) which does not own or operate a cellular telecoms network, but which leases capacity from one of the network operators, and only provides a SIM card to its customers. MVNOs first appeared in Denmark, Hong Kong, Finland and the UK and today exist in over 50 countries including most of Europe, USA, Canada, Australia and parts of Asia and account for approximately 10% of all mobile phone subscribers around the world.
On some networks, the mobile phone is locked to its carrier SIM card, meaning that only the specific carrier's SIM cards will work. This is more common in markets where mobile phones are heavily subsidised by the carriers, and the business model depends on the the customer staying with the service provider for a minimum term (typically, 12 or 24 months). Common examples are the GSM networks in the USA, Canada, the UK and Poland.
A plethora of online and high-street (third-party) businesses now offer the ability to remove the SIM-lock from a phone, effectively making it possible to then use the phone on any network by inserting a different SIM card. Some of these resellers use wholeseller databases.[7] This is a useful benefit for travellers that might want to put a local SIM card into their phone when they arrive in a country, in order to minimize roaming charges. In many countries, now it is possible to buy a pre-pay SIM card just by walking into a store, and these SIM-only deals are a cost effective way to stay in contact when travelling.
Phones sold as pre-pay often come with an operator subsidy, especially in competitive mobile markets like the UK. These phones are sold not just through mobile phone stores, but also supermarkets, catalogs, stationery outlets and online; thus the mobile companies are constantly competing to lower the price. Prepay phones come with a bundled SIM, which can be activated by the user in case the phone is bought up. The handsets are often SIM-locked to ensure that the user does not use another operator, allowing the original operator to eventually recoup its subsidy. However, because the units can be unlocked for a small fee (and even the operators themselves offer this service), units can be bought cheaply, separated from the original SIM card and sold on for a profit, perhaps in other markets, perhaps as contract phone. This is known in the industry as box breaking, and often harms the profits of the operator while allowing complicit sales staff and box breakers to reap the rewards. Note that, if a prepaid handset breaks, the SIM card (representing the prepaid account value, plus user's address book, history, etc) can typically be moved to another prepaid handset if the phone-network is the same. That is, the account is tied to the portable SIM card, not the handset, on prepaid phones. This is useful because by 2010, prepaid handsets cost less than the value a user might have stored in an account.
Mostly, GSM and 3G mobile handsets can easily be SIM-unlocked and used on any suitable network with any SIM card. A notable exception is the Apple iPhone, where in most markets Apple has gone to extreme lengths to lock-down their phones; thus they can only be used with the partner's network. This has led to a popular hack called the jailbreak, which allows custom software unapproved by Apple to run on the phone. Then software can be run to unlock the phone, which frees the iPhone from the partner network; thus any SIM card can be inserted. (Note that jailbreaking, in itself, does not unlock the phone, and has other uses as well.) Apple and the hackers are locked in a war of escalation - described by Apple CEO Steve Jobs as "a game of cat and mouse"[8] - with Apple constantly trying to close loopholes in their operating system, and the hackers finding new ways to jailbreak each version when it becomes available.
In countries where the phones are not subsidised e.g. Italy and Belgium, all phones are unlocked. Where the phone is not locked to its SIM card, the users can easily switch networks by simply replacing the SIM card of one network with that of another while using only one phone. This is typical, for example, among users who may want to optimise their telecoms traffic by different tariffs to different friends on different networks.
Dual SIM phones are now made by some mobile phone manufacturers, which save the user from carrying around a separate phone for every number. There are two types, the first, that allow one to switch between the SIMs, and the second, that allow both SIMs to be active simultaneously.
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