Computers Today, May 16-31, 1999, Telecom; Open SeSIM

Subscriber Identity Module card for GSM phones has revolutionised the concept of communications-on-the-move. Based on smart card technology, it is now enabling the GSM terminal to become a mobile gateway into the world of voice, data, video and multimedia through the Internet.

The cellular phone industry began by feeding on people's desire to make calls and send data on the move. Today, an increasing number of users and expectations are pushing companies to deploy new technologies for that extra edge. Roaming agreements between different national operators are enabling users to travel freely between countries, taking their mobile handset with them. It is expected that there will be more than 150 million users of GSM phones by the year 2000.

So what's the emerging trend? For one, the development of dual-band handsets, capable of operating on more than one frequency. This further extends the roaming ability of handsets and moves closer to the goal of a truly global cellular system. A key force stimulating this massive growth is the convergence of telecom and computer technology. Cellular telephones are already more than just simple handsets to make voice calls. For those not in the know of things, you can send your fax or E-mail, reach the voicemail or surf the Web through the versatile gadget.

At the heart of this service revolution is a small card called the Subscriber Identification Module which fits inside all GSM handsets.This smart card incorporates a specially designed embedded microchip. The chip contains the user's account details along with information on service access and preferences. Information stored in the card can include, among other features, frequently dialled telephone numbers, tariff details, optional features and additional services to which the user has subscribed.

The Lock and Key

In the world of SIM cards, a mobile user is not phone dependent. All one needs is a SIM card and almost any GSM phone.

However, this is not all true, because all over the world, service providers sometimes give away phones for free or almost free. To prevent the owners from swapping GSM networks to a competitor, they use something called SIM-lock. It means that the particular phone is barred from the use of any other SIM card. A SIM-lock works as follows: the operator has entered a lock-code into the phone to tie it to a specific SIM card. It is fully possible to unlock the phone again. But that can be done only by entering the lock-code again, which only the net operator has access to.

So, having a SIM-locked phone means that it's tied to single card or a single operator, but not the other way around. A customer can use his SIM card in another unlocked phone or a phone locked to the same network operator. Using a SIM-lock makes it possible for the net operators to subsidise a phone even more, because the operator knows for sure that the clients can only use one single network service. In some countries, as in the case of Hungary, all phones sold through a network operator are SIM-locked.

It is around this plastic card that mobile systems are evolving to provide faster and more sophisticated communications capabilities, without the restriction of a fixed connection. SIM cards hold the information independently of the handset in which they are used. Hence, whether you go from Delhi to Indore, or from Mumbai to Boston, remove the SIM from your handset, insert it into another and operate as though it were the same phone. The SIM card is often called "the real phone", as it stores all the personal details, including the phone number. For GSM phones, these cards come in two sizes: one is the size of a credit card and the other is about the size of a stamp. Both cards contains the same electronic circuits; it's only the plastic surrounding that differs. The advantage of the bigger card is that is easier to swap; the small card might slip between your fingers. The manufacturers, however, prefer the small card as it allows them to build even smaller phones.

As it evolves, the SIM for a GSM phone is almost like buying a phone card for a payphone. The subscriber pays for a specified number of call minutes in advance, and the relevant amount of credit is loaded into the GSM. Once the specified number of minutes is used up, the card must be re-charged for further calls. For the subscriber, the SIM card can be used in any other GSM compatible phone that accepts cards of the same size. There is a PIN (Personal Identification Number) for the SIM card, which is equipped with a numeric identity known only to the user. A cellular customer can borrow almost any other GSM phone and insert his or her own SIM card and make calls as usual. Be sure that the phone bill will incorporate these calls too.

The SIM cards are beginning to do more than just store your phone number. There are many functions that can be embedded on the microchip's small surface. For example, a SIM card may have memory space to save maybe 100 names and phone numbers, and about 15 short text messages. Efforts are on to develop cards with memory enough for 200 names and phone numbers, and more messages.

The mobile trend nowadays is to have a prepaid SIM card. Just as motorists re-fuel their cars when the tank is low, mobile phone users of, for example, AirTel and Essar Cellphone in Delhi, are able to 'charge up' a pre-payment card for their mobile calls when the call time runs out. The result: lower operator debts, less need for credit control, and a 20 percent saving on operational costs. Nowhere does a prepaid card help more than in remote areas, where cellular operators face a growing problem of chasing payments from errant subscribers. Many of these subscribers do not have a bank account, let alone a credit card, and live many kilometres from the nearest city. Conventional monthly billing may result in the operator carrying forward an ever increasing pile of debt.

GSM may provide a solution which is both efficient from the operator's viewpoint, and acceptable to the customer. Not many know that the key, of course, is the SIM card. The card is programmed with a secret code used by the cellular operator to identify the phone, and with a PIN for the subscriber. Once the PIN is activated, the subscriber cannot use the phone without entering the correct number. Such a high level of security means that SIM is also ideal for keeping a watch on customer payment information.

With the growing capabilities of a SIM card, Web surfing from mobile devices is taking on a whole new dimension. New services are being developed to make Internet usage even more convenient for mobile users. There is JavaCard specification for a type of microprocessor card which allows execution of Java "applets" (small, self-contained applications). These have been coded in a subset of Sun's standard Java programming language. These applets can be downloaded from the terminal or server-for example, when the card is inserted into an ATM terminal, through the Internet or telephone systems. Phase 2+ GSM cellular SIMs will be based on JavaCard technology. Users will, therefore, be able to access other applications such as banking facilities from their mobile telephone handsets. The handsets will download the necessary applets using the GSM short message service (SMS) protocols, and these will then execute on the SIM.

An exciting advancement in SIM technology has been the development of powerful software called a SIM Card Application Toolkit. This software enables new features and information to be downloaded into a SIM card through the GSM network. Prior to its development, subscribers had little ability to add new features or change information stored on their SIM. This can now be done easily through the network. The specifications for the SIM Card Application Toolkit have been defined by the European telecommunications Standards Institute as part of GSM Phase 2+.

The ability to download information and features securely over the network adds a paradigmatic dimension to mobile telecommunications since its invention. Already a number of companies are looking at these applications to offer new services to customers. Services could include call scrambling, paging or message retrieval, and SMS capabilities.

The advantages are many. But users are still yearning for more, especially facilities available in the West. One function that might come in handy in India would be the facility to bar the SIM cards from allowing calls to other phone numbers than those kept on the card; at the same time they are enabled to receive calls. This could be of great use to parents who wish to keep a tab on their children at home. The youngsters can only call the numbers not barred by the parents. This makes it impossible for youngsters prone to making long and expensive calls to their friends.

For silicon chip designers and manufacturers, such as Motorola and Fujitsu, the development of SIM technology provides considerable challenges. Experts predict 37 million GSM SIM cards will be in use by 1999, with the number slated to reach 60 million by 2000. With rising expectations, chip manufacturers have to ensure that their products strike a balance between security, features and price. Chips must have sufficient memory and processing capability to deal with planned applications while remaining cost effective to design the cards.

Many industry watchers predict that it will be the telecommunications industry-particularly the wireless mobile sector--that will drive the smart card industry into the next century. Currently, the Asia-Pacific smart card market is growing at the staggering rate of 150 percent a year. This, at least in part, is being fed by the growing popularity of GSM telephones, especially in developed parts of the region such as Hong Kong, Malaysia and Singapore. Proof of this trend is some of the major investments being carried out by some of the industry's major players. For chip manufacturers, the future is looking bright. For users, the massive investment being made in chip design and manufacture will lead to better services and a more flexible lifestyle. SIM is just the beginning.