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One of the key features of GSM is the Subscriber Identity Module, commonly known as a SIM card. The SIM is a detachable smart card [ 3 ] containing a user's subscription information and phone book. This allows users to retain their information after switching handsets.
A typical SIM card (mini-SIM with micro-SIM cutout) A SIM card or SIM (Subscriber Identity Module) is an integrated circuit (IC) intended to securely store an international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephone devices (such as mobile phones and laptops).
The history of the GSM module dates back to the 1980s when the GSM network was first introduced. The first GSM module was designed to work with analogue phones, and it was not until the late 1990s that digital GSM modules were introduced. Today, the GSM module is an essential component used in various communication systems.
When talking about IS-95/GSM multi-mode phones, for example, or AMPS/IS-95 phones, the base band processing is very different from system to system. This leads to real difficulties in component integration and so to larger phones. An interesting special case of multi-mode phones is the WCDMA/GSM phone.
GSM module or GPRS modules are similar to modems, but there's one difference: the modem is an external piece of equipment, whereas the GSM module or GPRS module can be integrated within an electrical or electronic equipment. It is an embedded piece of hardware. A GSM mobile, on the other hand, is a complete embedded system in itself.
The GSM standards are defined by the 3GPP collaboration and implemented in hardware and software by equipment manufacturers and mobile phone operators. The common standard makes it possible to use the same phones with different companies' services, or even roam into different countries. GSM is the world's predominant mobile phone standard.
CAMEL Phase 1 defined only very basic call control services, but introduced the concept of a CAMEL Basic call state model (BCSM) to the Intelligent Network (IN). Phase 1 gave the gsmSCF the ability to bar calls (release the call prior to connection), allow a call to continue unchanged, or to modify a limited number of call parameters before allowing it to continue.
As of 2019, all available mobile phones have a proprietary baseband chip (GSM module, cellular modem), [2] [3] [4] except for the Necuno, which has no such chip and communicates by peer-to-peer VOIP. [5] [6] The modem is usually integrated with the system-on-a-chip and the memory. [4]