Programmable SIM card

Author: Anagha Ravi


The primary role of subscriber identity modules (SIMs) is to help cellular networks identify their subscribers and securely authenticate their identities. The process starts with a SIM transmitting a 64-bit identifier–the international mobile subscriber identity number, or IMSI–and a code representing the subscriber authentication key (Ki) to a cellular network when your device attempts to connect. Once the network receives this information, it checks it against a corresponding list of identifiers and keys in a database known as the authentication center (AuC) to verify the SIM. If the information checks out, the network allows your device to complete the connection process. 

The SIMs that most people are familiar with have just one set of identifiers and keys because they are locked to a single mobile network operator. This means that if you want to switch to a different operator, you have to change the SIM card in your device. Such single-operator SIMs are not programmable; their credentials are baked in during manufacture and cannot be changed. 

For the average user, changing SIM cards is usually no more than a minor inconvenience that they can mitigate somewhat by using a dual-SIM phone. However, there are many situations–think of buoys at sea, or businesses that have to manage hundreds or thousands of SIMs remotely–where it is undesirable or impossible to switch SIM cards. For such use cases, programmable SIMs are ideal.

What are programmable SIM cards?

Unlike standard SIM cards, the identifiers and keys for programmable SIMs can be securely reprogrammed, which means a single SIM can connect to many mobile networks–hundreds, in some cases. These types of SIMs are sometimes referred to as ‘reprogrammable’ or ‘multi-network roaming cards.’ 

Programmable SIMs can be removable, as is the case with the type sold on Amazon and other ecommerce stores; embedded somewhere on a device; or purely virtual, in which case they are known as soft SIMs. Embedded programmable SIMs are often referred to as embedded universal integrated circuit cards (eUICCs) or eSIMs. (Strictly speaking, ‘eSIM’ refers to a GSMA-defined standard that allows mobile operators to load profiles onto SIMs over the air. However, the term is also widely used to refer to the embedded programmable SIM hardware found in some modern smartphones and tablets.) 

In the field of internet of things, programmable SIMs are known as IoT or Machine-To-Machine (M2M) SIMs. Programmable SIMs that are incorporated into modems and application processors are known as iUICCs or iSIMs.

History of programmable SIM cards

In some ways, programmable SIMs are a logical progression of the SIM card technology, which traces its roots to the development of the Global System for Mobile Communications (GSM) technology. In 1982, operators in 13 European countries signed a memorandum of understanding to lay the groundwork for GSM. In 1995, the GSM MoU group, as it was known, was formally registered under the name ‘Global Systems for Mobile Communications Association’ (GSMA). The association owns the GSM trademark and represents mobile operators worldwide. 

In 1989, the European Telecommunications Standards Institute (ETSI) took over the responsibility of standardizing the still-nascent communications technology. Over the next few years, the organization developed standards that made possible the development of SIM cards. The first SIM cards were made by Giesecke & Devrient, a German firm that specialized in smart cards and banknote security. The company sold its initial batch of 300 cards to Radiolinja, a Finnish wireless network provider, which hosted the world’s first GSM call in 1991. 

These early SIM cards were the size of a credit card. Known as full-size or 1FF SIMs, they were replaced by considerably smaller mini-SIM cards in 1996. Mini SIMs are also known as 2FF, standard or regular SIMs. However, even these proved too large as smartphones became progressively slimmer, leading to the introduction of 3FF form factor SIM cards, popularly known as micro-SIMs, in 2003. In 2010, the iPhone 4 became the first smartphone to use micro-SIM cards. Despite the diminutiveness of the card–it is roughly the same size as an average human thumbnail–the race to pack ever-more gadgetry into increasingly thinner shells meant even the micro-SIM was eventually deemed too large. In 2012, the 4FF form factor SIM, or the nano-SIM, was introduced. The first smartphone to use this tiny card was the iPhone 5.

The hunt for more space to pack components means many modern flagship smartphones have to do without such niceties as headphone jacks, suggesting that the days of the nano-SIM are numbered as well. A probable portent of this development is the growing tendency to include both programmable embedded SIMs and typical SIM slots in high-end smartphones and tablets.

The technical foundations of programmable SIMs were laid in the late 1990s when industry stakeholders formed a collaborative initiative, the Third Generation Partnership Project (3GPP), to forge a more refined and secure mobile telephony system. Currently responsible for managing standards for GSM and related technologies such as 2G, 3G, 4G and 5G, this initiative developed the Universal Mobile Telecommunications System (UMTS). More importantly, it redefined SIM-ware as two separate elements: hardware and software. Rejigging the definition in this manner meant SIMs could now take virtually any form–a standard form-factor SIM card, a chip embedded on a motherboard, a component of a system-on-a-chip, or just software. 

How do programmable SIM cards work?

Programmable SIM cards can be remotely provisioned with the subscription credentials of more than one carrier, allowing users to switch from one to another when needed. Where the necessary roaming agreements have been concluded, these SIMs can download the needed credentials from the databases of mobile operators. 

During the process of changing carriers, programmable SIMs deactivate the identifiers and keys in use and activate the credentials of the network to which they are switching. This process is analogous to changing SIM cards. 

Provisioning a few SIM cards to connect to a private long-term evolution (LTE) network requires little more than a smart card programming device, the necessary software, and blank programmable SIMs. However, provisioning hundreds or thousands of SIMs is a far more formidable task, and it is typically accomplished through specialized vendor portals. 

Programmable SIM solutions require numerous roaming agreements to be in place to guarantee uninterrupted connectivity. However, signing agreements with hundreds of carriers around the world is a tedious process. For this reason, vendors of programmable SIM solutions usually work with connectivity brokers, who sign up numerous carriers and then parley these relationships into a range of simple connectivity solutions, which they then offer to their customers.

Types of programmable SIM cards

There are two types of programmable SIM cards: physical and virtual. The former category includes both non-removable M2M SIMs and removable SIMs, which come in the usual form factors – mini (2FF), micro (3FF), and nano (4FF). 

Nonremovable M2M SIMs are available in two ETSI-defined form factors: MFF1 and MFF2. The primary difference between the two is that MFF2 SIMs come with integrated heat sinks to improve thermal performance. MFF2 SIMs are sometimes referred to as DFN-8, SON-8 or VQFN-8. 

All these SIM types have ruggedized variants–sometimes known as industrial or automotive IoT SIMs in the M2M field – for use in extreme environments. However, because removable SIMs, along with the mechanisms that make it possible to insert and remove them, are more likely to suffer from corrosion and mechanical failure, ruggedized SIMs tend to be of the non-removable variety. Non-removable SIMs are sometimes referred to as machine identification modules (MIMs). 

SIM functionality can be integrated into modems and application processors to create virtual SIMs known as iSIMs or iUICCs. These SIM types are somewhat similar to soft SIMs but are more secure because they run in dedicated environments or on special processor cores. 

In contrast, soft SIMs are purely virtual and do not require specialized hardware to run. However, because they lack many of the security features that their non-virtual counterparts offer, soft SIMs are generally unpopular with mobile operators. 

Programmable SIM cards also differ in the way they connect to networks. Steered cards prioritize connections to one carrier over others, though they have the capacity to connect to a range of operators. On the other hand, unsteered or non-steered cards are not programmed with a particular carrier preference; they connect to whatever operator has the best signal in a given location. Because unsteered SIMs prioritize connectivity rather than carrier preference, they are generally preferred over their steered counterparts.

Programmable SIM cards use cases

Vehicle tracking

Programmable SIMs can be configured to switch among multiple operators to maintain the best possible connection in any location, an attribute that is particularly valued in fields that require uninterrupted real-time location tracking, including vehicle tracking. 

Equipment tracking

Companies around the world spend millions of dollars and thousands of man hours every year trying to locate misplaced equipment. Programmable SIM solutions have proved to be a valuable mitigant in this regard. Nanolink, for example, offers programmable SIM-based trackers that can be securely attached to high-value equipment so that firms can quickly track them down. 

Package tracking

Because they can be provisioned with multiple operator profiles, programmable SIM solutions are particularly suited to package tracking. A notable example is SenseAware, a FedEx solution that uses eSIMs and M2M modules to keep track of high-value packages. 

Acquiring real-time patient data

Getting real-time data for diagnostic purposes can be challenging when patients are on the move or at home. Programmable SIM solutions can be invaluable in such circumstances as well. For instance, the Canadian firm m-Health offers a SIM-based electrocardiographic device dubbed m-CARD that tracks cardiac electrical activity and transmits the information to user-specified locations for analysis. The company also offers wearables and AR glasses for medical and recreational uses that can collect and securely transmit data to remote locations as well. Apart from ensuring these devices to maintain unbroken connectivity, programmable eSIMs also allow m-Health and other wearables manufacturers to make smaller, more power-efficient connected devices than would be possible with traditional SIMs or other applicable connectivity technologies.

Cellular vehicle-to-everything (C2VX)

Programmable SIM solutions are also seeing increasing adoption in cellular vehicle-to-everything (C2VX) applications, where they can ensure uninterrupted connectivity as cars move or are sold in different countries. Apart from ensuring unbroken connectivity, programmable SIM solutions can help carmakers meet certain regulatory requirements in a more convenient matter. For instance, authorities in Europe, the United States and Russia require vehicles to be locatable during emergencies; carmakers can provide a single programmable SIM to connect to both emergency services and the car owner’s cellular services of choice.

Benefits of programmable SIM cards

One of the most notable benefits of programmable SIM cards is ease of management; organizations can configure and update a large number of SIMs over the air quickly and efficiently. In addition, because users can easily switch to an operator offering the best value for their money at any given moment, these SIMs can help cut costs by a significant margin. And as they can be installed virtually anywhere on a motherboard, programmable SIMs can make phone design easier, allowing for more innovation and helping handset manufacturers find additional space to install componentry. 

The ability to download local SIM profiles over the air means travelers can avoid international roaming costs. Programmable SIMs may also make possible new business models, such as forms of account aggregation that would present customers with a single bill for usage across multiple networks, or the ability to automatically switch to a network offering the best rates or coverage at any given moment.