Learn how SIM card works Saibaar

Many years ago, people used to talk from one place to another through wires during landlines. But day by day, with the development of civilization, people have taken their intellect and information technology to another height.

Where before people used to talk on wires, now that communication is done through SIM on smartphones. At a time when people were in trouble with it, SIM card has not only reduced the hassle in people's lives but also taught people to think about information technology anew.

What is a SIM card?

The full form of the English word SIM (SIM) is the Subscriber Identity Module. The SIM card we see today was first created in 1991. It connects the mobile phone to the network and provides the desired service to the service seeker. Messages, the internet, etc. are available.

 Part of the SIM card:

The SIM card usually has its own number known as the IMSI number. IMSI stands for International Mobile Subscriber Identity. It also has an authentication letter or authentication key provided by the service provider with the phone. (+ 8801 ××××××××). The first three digits or numbers are a country's own code, after three digits one or two digits is the network code of the service provider and the last numbers are the identification number of the SIM used. Each country has its own code. As it is different, if you want to use the SIM card of one country in another country, you must use it while roaming.

The way of SIM card works:

Many people do not know how to do so much with such a small thing. So let's find out: -

In fact, the main thing about a SIM card is the chip in the SIM and the number that exists in it. When a new SIM is connected to a mobile, the IMSI number on that SIM card goes to the mobile operator providing the service. The service provider company then finds out the authentication key from the database for the IMSI number. Creates a response number by calculating the authentication key with the random number. Then the random number is sent to the phone by the service provider then the SIM card creates that random number and another new random number by the SIM card authentication number. The company generates and the other random number that generates the SIM card on the phone (if the same) then the service provider receives all the data of the SIM and the phone and connects to the network tower.

It is good to note that some of the numbers written on the SIM card are ICCID numbers, the full form of which is the Integrated Circuit Card Identifier. When traveling abroad, this number testifies that the SIM card you use is a valid SIM card.

What is a roaming system?

Each SIM card works in a specific area. For example, a SIM card in Bangladesh only works in Bangladesh and usually does not get a network outside. For example, if someone from Bangladesh goes to America and starts a roaming system if someone calls that SIM in Bangladesh, then the SIM company providing the service in Bangladesh sends the call to the American service provider according to the location of its customer and then goes to the customer. In this case, the American service provider will keep the details of the call for the Bangladeshi SIM card call in the United States and will send the bill to the Bangladeshi SIM company. In this, the customer has to pay the Bangladeshi SIM bill. As a result, 550 will cost a little more than a normal phone call

Types of SIM cards:

In 1991, the first full-size SIM, then mini-SIM, then micro-SIM came, and now almost everyone has a nano-SIM card in their phone. In the future, e-SIM cards will be widely used. Most of the SIM cards in developed countries are locked with the phone. If someone buys a phone and has a SIM attached to it, the customer will not be able to buy another SIM or access the mobile even if he wants to.

SIM card data memory:

A SIM card can usually store 8 to 256 KB of data and about 250 names or numbers. The SIM card's memory contains ICCID numbers, IMSI numbers, authentication keys, LAIs, emergency numbers, SMS numbers. LAI is the local area identity that tracks the location of the phone. When moving from one network to another, the new LAI value changes and is stored in the SIM and overloaded.