Thursday, March 13, 2014

SIM cards tutorial - Part 1:Getting started


SIM (Subscriber Identity Module) cards are the key to cell phone networks. Initially SIM cards came with GSM networks. But these days SIM cards are also used in CDMA networks. This series of tutorials will take you around and inside SIM cards.
What is a SIM card? 

SIM cards can be considered as a micro-computer system. It contains CPU, memory and an I/O interface. A micro operating system is also running inside SIM cards. It is this operating system which implements high level security features of SIM cards. Despite of this, SIM card is of no use as a standalone device. SIM card should be connected to some other interfacing hardware to achieve various tasks.
SIM cards generally belongs to the family of contact smart cards. Internal and external architectures of SIM cards are actually slightly modified version of contact smart cards. SIM cards strictly follow some global standards. Some of these are listed below. 

    GSM 11.11 - Base standard for GSM SIM cards
    ISO 7816    - Electrical interface standards for contact smart cards
    3GPP          - Base standard for CDMA SIM cards
    ETSI           - General standard for smart cards

What is its use?

SIM cards are used for authentication and security in mobile networks. Authentication is the procedure by which a registered user is granted access to the mobile network.Key used for encryption of the communication channel is also based on SIM cards. Apart from all these SIM cards contains other information like contacts, SMS, last dialed number. In olden days when mobile phone memories were limited, storage was also a major function of SIM cards.

Physical structure
The physical structure of SIM cards resembles a piece of plastic or fiber sheet with some metallic contacts. SIM cards generally comes in following form factors.

Credit card sized (Obsolete now)

Mini SIM card
Micro SIM card
Nano SIM card
 SIM card pin out 

SIM card pin out
On every SIM cards you can find six or eight golden colored contacts. It is through this contacts SIM card communicates with a mobile phone. In most of the case, entire electronics inside a SIM card resides beneath these golden contacts. So if you get a partially broken SIM with no damage to the above said area, then in most cases you can retrieve the data.

Next part - SIM card architecture


KeVaL sHaH said...

i have Swipe Elite Plus Smartphone,
suddenly both simCard signals not come says 'No Service or Emergency Call' but SimCard Contacts Show

Anonymous said...

It's a hardware fault in your smartphone

Mm Azad khan said...

I have same problems

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