If SIM cards could talk, we’d imagine them to have few words. After all, they are ubiquitous yet universally forgotten most of the time, toiling away quietly in every mobile phone to provide us with the means to communicate with the rest of the world. As if to remind us of its importance, the Apple iPad has for a few moments cast some deserving attention on this unsung hero. Enter the microSIM, a name coined by Apple, which is about half the size of current SIM cards.

To understand this better, we spoke to Jean-Louis Carrara, vice president for Business Development at the Telecommunications unit from Gemalto North America, in an email interview recently.

How many types of SIM cards are available in the market today?

SIM cards refer to a generic term that actually includes many different product families. The first basic families are SIM (for 2G and some 3G networks), the RUIMs (for CDMA networks) and UICCs (for 3G and LTE networks). These cards support multiple telecom applications and other applications like payment, transit, etc.

Each product family is then defined by the size of the memory made available to the telecom operator. They are usually 64KB, 128KB, 256KB, 500KB, 700KB, etc.

Finally, SIM/UICC can be shipped in various form factors:

• The universally known plug-in SIM (also known by its standard name 2FF);
• The recently advertised microSIM, made famous thanks to the iPad (also known by its standard name 3FF);
• The ones specific to the Machine-to-Machine harsh environments SMD (surface mount design) or socketable SIM that can withstand higher temperatures, humidity, and vibrations. In that category, the most common package is vqfn8 (with 8 PINs), but others are available as well;
• Some in microSD form factors used today in unconnected mobile TV players.

How did the 3FF microSIM come about and what are its differences compared with the current 2FF SIM?

The 3FF came about a few years ago in the standardization as an answer to a concern from OEMs that the 2FF SIM was taking too much space for future devices.

Why did it take so long for 3FF to catch on?

It is the role of the standardization to prepare for the future. The need for a smaller SIM was identified ahead of the design requirements, which is better for the whole industry. Once the design requirements arise, all companies can look at what was already standardized and immediately converge toward a single rapidly workable solution. 3FF caught on when the design need appeared.

Are there any other devices that use the microSIM aside from the Apple iPad 3G?

Yes, in fact, the Lok8u device required microSIMs before Apple named the 3FF a microSIM.

What are the main advantages of the microSIM? Are there any tradeoffs in terms of capacity, functions, etc., due to its smaller size?

No, there are no tradeoffs in terms of capacity, functions, memory size, etc. The SIM/UICC chips are always smaller than the contact plate (the metallic area visible on the SIM), and the 3FF is still larger than the contact plate.

If I cut my current SIM card to match the size of the microSIM, will it work on the iPad?

This is not something we recommend because there are too many parameters that may prevent it from working. You will have to have support for the right radio in the SIM, your wireless service plan must be compatible with your new device, the network or device may have some specific constraint of which you are not aware, and you will have to be very precise in your cutting and not break the chip inside. This can easily turn into an expensive failed experiment.

Is it possible to have prepaid options for microSIM? Are there any barriers to that or is it purely a business strategy on the telco operators’ part?

Every plan can be associated with any form factor, including prepaid. These are distribution and provisioning decisions that each operator takes according to its market. SIM/UICC have successfully enabled all kinds of distribution models around the world and have always delivered strong security compared with other alternatives; that is why SIM/UICC are so prevalent in the wireless industry. Some operators distribute phones, others don’t and just distribute SIM/UICCs. Other operators subsidize all their phones, some sell one prepaid subscription with four SIMs to promote viral customer acquisition.

How are SIM cards locked to certain telco operators?

SIM cards are always owned by an operator and associated with that operator by their main identification, the IMSI (International Mobile Subscriber Identifier). The IMSI is a long number that contains the country of issuance and the mobile network code associated to that card. That’s how we can travel across the world, attach to a local network and that network immediately knows to contact our home network to authenticate us and authorize the international roaming service.

Do SIM cards have unique identifiers like phones?

Yes, SIM cards have unique identifiers–the IMSI (loaded in its memory), which is a network identifier, and the UICC-ID, which is usually printed on the plastic for easy visual identification.

What developments can we expect to see in the near future for SIM cards? More functions or perhaps higher memory capacities?

We’ve come a long way from the 2G SIM cards that were available only in credit card format, had just a one-size memory and could authenticate only on a 2G network. Today’s SIM/UICCs are truly IP-connected cryptographic devices. They communicate over HTTPS, authenticate us mutually to multiple types of networks, secure mobile TV systems, support payment, transit and other NFC applications, and are available in ever greater memory sizes and new and innovative form factors.

Who does Gemalto make 3FF microSIMs for and which carriers worldwide have adopted this type of SIM cards?

As the largest provider, Gemalto has already shipped SIM/UICCs in the 3FF form factor to dozens of carriers worldwide. The list remains confidential until the operators release these cards to the public.

By Damian Koh