A Deep Dive Into SIM Cards

The SIM card (subscriber identity module or subscriber identification module), in its simplest form, is the identification card of the wireless world. In today’s wireless carrier world, the SIM is the universal answer to secure identification with every carrier in the world. The SIM contains phone number, personal security keys and most importantly, the SIM carries unique encrypted identifiers for secure access to a wireless carriers’ data network.

Think of the SIM as a drivers’ license or credit card for comparison. The credit card and driver’s license only contain identifiers. The credit card doesn’t contain any money, or readable bank identifiers. The credit card simply identifies the individual and includes bank authentication identifiers that are meaningless to the outside world.

In today’s post, we’ll answer some frequently asked questions about SIM cards.

Why are SIM Cards a popular choice for connectivity?

SIM cards are the ONLY choice for GSM network connectivity with any of today’s 21st century wireless carriers worldwide. The SIM is a universal component to access wireless carrier networks.

How does a SIM Card connect to a carrier?

After a SIM card is inserted into a device, and power is turned on, the wireless device begins to search for its relevant carrier or roaming carrier cell sites based on the device MCC MNC. (MCC = Mobile Carrier Code; MNC = Mobile Network Code). Neither the SIM nor the carrier cell site performs any cell site analytics or function beyond providing authentication. The carrier selection process is actually a function of the modem/module firmware within the device. Once the device operating system selects the correct carrier cell site, the device connects to the appropriate carrier and sends encrypted data stating who it is (identification) and what functions it wants to perform (request data connection). The data connection request includes a specified carrier APN name. (APN = The Access Point Name (APN) defines the network path for all cellular data connectivity.) The device “request for access” is sent around the carriers’ internal systems for authentication and permission verification. Once all internal carrier authentication processes are complete, the wireless carrier creates a data session between the device and the carrier.

What's been the evolution of the SIM Card?

SIM cards, and their respective form factors, have evolved over the last 20 years. Originally designed to fit into older, larger phones, the SIM technology has decreased in size and increased in functionality by way of the ESIM.

  • - 2ff – Mini SIM
  • - 3ff – Micro SIM
  • - 4ff – Nano SIM
  • - eSIM – Embedded SIM
  • - iSIM – Integrated/Virtual SIM
  • iSIM is a more recent technology that enables the functionality of a SIM card to be integrated into a device’s main processor. The tech is actually like an eSIM but it’s embedded into the device.

What's the latest in SIM Cards?

Meet the eSIM. Over the past several years, SIMs have evolved into what the industry calls eSIMs. eSIMs are designed to be embedded (soldered) onto the device hardware. The original eSIM design was to bring multiple carriers together onto one SIM to promote cost effective device connectivity on local networks as opposed to potentially higher priced roaming costs generated from one carrier’s global roaming agreements. The “platform” could be built, controlled and maintained by third party data aggregators or carriers themselves.

Today, there are several eSIM options available. First, the form factors can be either an embedded, solder-on solution and or a traditional removable SIM form factor that is currently utilized in traditional wireless phones.

Due to the lack of enthusiasm from both US carriers and global carriers to join together on one SIM, other forms of the eSIM were introduced… and basically customers have two eSIM options readily available.

There are many physical eSIM options but, generally speaking they come in two “flavors”.

Physical eSIM Solution number 1

Platform based

  • Requires 3d Party eSIM provisioning platform
  • SIM can be provisioned and activated remotely
  • Platform based eSIM has the potential for 16 plus carriers at any given time with options to add/subtract additional carriers as needed.

Physical eSIM Solution number 2

Pre-Provisioned (Hard coded and NOT configurable)

  • Pre-Provisioned carriers burned into SIM card (non-changeable)
  • Multi-IMSI SIM – This SIM can also be referred as a Multi-IMSI SIM
  • An eSIM provisioning platform is NOT necessary for the Multi-IMSI SIM
  • This type of SIM with pre-provisioned carriers can be restricting especially if roaming agreements change.
  • Sometimes standard carrier roaming rates are cheaper than direct carrier relationships set up on the multi-IMSI SIM.

eSIMs can streamline and help reduce high global roaming fees. Below you will find some actual examples of existing eSIM utilizations.

International Airlines. International Airlines use eSIMs in their wireless data connections in airports all over the world. Wherever they land, the eSIM will have some carrier solution that will connect the plane's data network to the terminal network to download movies and concierge service-related items.

International Shipping

International shipment tracking on container ships have used a solution that includes an “applet (mini application)” on the actual SIM card itself. Using the “applet” upon reaching shore based wireless carriers, the device would first identify the MCC/MNC being broadcasted by local cell towers. Based on pre-programmed logic, the applet would connect to the local cell towers. Based on pre-programmed logic, the applet would connect to the local carrier the internal SIM was provisioned for. This would NOT require a platform per se.

One Skew for the World

One device/SIM skew that would work on carriers worldwide. Devices would be shipped anywhere in the world, and by utilizing the platform, the SIMs can be provisioned for the local area of the globe.

To learn more about OptConnect’s SIM card options, please call 877-678-3343.

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