Everyone knows that our mobile phones need a SIM card to connect to the operator's network. Without a SIM card, it's just a "bare" phone and cannot perform functions such as making calls. The SIM card plays a crucial role as an identification document for network operators.

What is a SIM Card?

A SIM card (Subscriber Identity Module) is actually a chip card containing a microprocessor. It stores the customer's phone information, encryption keys, and the user's phonebook. It can be used to authenticate the customer's identity on the GSM network and encrypt voice information during calls.

Internally, a SIM card has five modules, each corresponding to a function: a microprocessor CPU (8-bit), program memory ROM (3-8kbit), working memory RAM (6-16kbit), data memory EEPROM (128-256kbit), and a serial communication unit. These five modules are encapsulated behind the SIM card's copper interface, similar to the packaging of a regular IC card. These five modules must be integrated into a single integrated circuit; otherwise, their security will be compromised, as the interconnections between the chips could become crucial clues for unauthorized access and theft of the SIM card.

When a SIM card connects to a mobile phone, it requires at least five connection lines: power (VCC), reset (RST), clock (CLK), ground (GND), and data I/O port (I/O).

Regarding the form factor of SIM cards, when they were first invented, their size was similar to that of credit cards.

This size of card is also known as a standard card. However, for mobile phone users in China, we are more familiar with the following three card sizes:

The second-generation standard SIM card is commonly known as the "large SIM card" by domestic users.

The third-generation standard SIM card is the "micro SIM card," commonly known as the "small SIM card."

The fourth-generation standard SIM card is the "Nano SIM card."

These SIM cards actually have the same function; the difference lies in their design, which has become increasingly smaller to accommodate device miniaturization.

What is an IoT SIM card?

An IoT SIM card is a network that connects any object to the internet via information sensing devices such as RFID, infrared sensors, GPS, and laser scanners, according to agreed-upon protocols, to exchange information and communicate, enabling intelligent identification, location, tracking, monitoring, and management.

When connecting to the internet, devices can be connected to the IoT platform through various network types, including fixed broadband, NB-IoT, and 2G/3G/4G/5G. If the device uses 2G/3G/4G/5G or NB-IoT networks, a SIM card is required to access the operator's network.

As IoT technology develops, there are more and more types of devices, and the size of devices is getting smaller and smaller. The requirements for the adaptability of SIM cards to the external environment are getting higher and higher, the lifespan of SIM cards is getting longer and longer, and the size of SIM cards is getting smaller and smaller. This has led to the evolution of SIM card form from plug-in SIM cards to embedded SIM cards and vSIM (i.e., virtual SIM cards).

While Nano SIM cards are already quite small, they still require a corresponding card slot in the device. The structure and wiring of this slot are still too large for some smart wearable devices, smart bracelets, and smart glasses. Furthermore, the user information on a plug-in SIM card is fixed and cannot be changed; a single SIM card represents a contract between the user and the operator, meaning you must change the card if you want to switch operators. To solve these problems, eSIM and vSIM cards were developed.

Embedded SIM Card (eSIM):

ESIM, also known as eUICC (embedded UICC), as the name suggests, differs from traditional pluggable SIM cards by embedding the SIM card directly into the device. While still a SIM card, its core is a programmable integrated circuit embedded directly on the circuit board, several times smaller than a Nano SIM. Due to its programmable nature, eSIM cards support remote configuration via OTA (Over-The-Air) updates, allowing network switching by updating the operator's configuration file.

In summary, because eSIM virtualizes SIM card functionality and integrates it into devices, switching SIM card numbers when using eSIM will bring a completely new user experience: users no longer need to repeatedly insert and remove SIM cards, but can directly interact with the terminal via an app or the cloud to connect their smart devices to the selected local network globally, and can dynamically switch between networks, ensuring the device always enjoys high-quality network speeds. In this way, eSIM not only enhances the overall user experience but also greatly simplifies device management and allocation.

Virtual SIM Card (vSIM):

Virtual SIM card technology is also known as a virtual-SIM card. It can be said that vSIM is a further evolution of eSIM, inheriting the functionality of eSIM and eliminating the need for a physical card. Communication is achieved directly through the communication module's own hardware and software. Terminal devices with a communication module that supports vSIM functionality, along with specially customized underlying software, implement built-in encrypted data storage (IMSI, KI, etc.). During network login, authentication, and communication, the corresponding logic is automatically processed, thus providing a stable communication experience without the need for a physical SIM card.

Besides further reducing or even eliminating the physical card size, eSIM and vSIM cards primarily decouple users from operators, making switching operators as simple as switching Wi-Fi networks for users. However, for operators, this reduced user loyalty is clearly not a good thing, yet they are still heavily supporting eSIM and vSIM cards. Why is that?

The reason, as we've already mentioned, is the Internet of Things (IoT). For IoT devices, traditional plug-and-play SIM cards can no longer meet their internet access needs.

For example, if a device needs to move globally but requires continuous internet access to report data, what should the company responsible for it do? Obtain a SIM card with global internet access? But that would be too expensive. Obtain a local SIM card in each country or region the device passes through, and change the card every time it arrives in a new location? That would result in excessively high maintenance and operating costs. The over-the-air (OTA) writing capability of eSIM and vSIM cards perfectly solves this problem. Before arriving in a new region, the device only needs to update its configuration online and can then use local internet rates.

Therefore, IoT device manufacturers are pursuing these new technologies, and with the massive number of IoT devices needing to connect to the network, operators naturally won't let go of this huge market. As a result, various eSIM and vSIM cards are now flourishing, all vying for market share.