SIM Phase II+

So, you can write a SIM application, but all it can actually do is manipulate files stored on the card. To create proper applications, you will need some sort of user interface, and without any kind of screen or input device, that's a challenge!

 

Obviously, the easiest way to do this is to make use of the screen and keypad on the mobile phone. This is what Phase II+ is designed to facilitate. Basically, if a handset supports Phase II+, then you can send it commands from the SIM to make it perform user interaction on behalf of your application. While the range of commands you can send to the handset is limited, the potential applications aren't.

 

The process is actually very simple: if a handset supports Phase II+, it sends a bit mask to the SIM indicating which of the following commands it will support. The SIM can then make use of those commands to interact with the user. Phase II+ is documented completely in the GSM 11.14 specification.

 

Phase II+ Command	Description
Display text	Display text on user screen.
Get inkey	Get a key press: used for dialogs.
Get input	Get string.
More time	Wait, SIM still processing.
Play tone	Play a tone - from headset if during call, otherwise from ringer.
Poll interval	Set interval for terminal to poll SIM. Too short an interval can drain battery.
Phase II+ Command	Description
Reset	Reset SIM, rebooting OS.
Set up menu	Create a menu.
Select Item	Select an item on a menu.
Send short message	Send SMS, with no user involvement.
Send SS	Send supplementary service message.
Set up call	Create a call.
Polling off	Stop polling. Can save battery life.
SMS PP	Get an SMS message. This will be downloaded to the SIM without user involvement.
Cell broadcast download	Get cell broadcast information. Again, this is done without user involvement.

 

If the SIM wants the handset (known as a "terminal" in this context) to perform an action, it responds to any command with the syntax 91,xx, where "xx" indicates the amount of data that is going to be sent. It is then up to the terminal to make a "fetch" request of the SIM to collect the command and action it, returning any results to the SIM. While this level of interaction is very basic, it still allows fairly complex applications to be developed.

Phase II+ Case Study: Telia and Postgirot Bank

Postgirot is part of Sweden Post. The MobilSmart brand was launched in 1997, and one of its main functions was paying bills through the user's mobile phones. It is in extensive use today, and has a security system involving encryption that's limited to GSM. This is how the system works, in a typical round of use:

 

Ø       PIN code entered, to start application

Ø       Postgirot account number entered

Ø       SIM creates SMS message

Ø       User adds comment

Ø       Signature created on SIM

Ø       Sent to Telia

Phase II+: Why Have WAP?

At first glance, it would appear that Phase II+ could provide much of the functionality available with WAP and WML, with the additional advantages of not replacing the handset or requiring new standards. However, there are a couple of areas where Phase II+ is distinctly lacking, and only WAP can be used.

 

The main point is that Phase II+ applications are written to the SIM before being distributed to customers, so that all functionality has to be decided on well before the service is launched, and it can't be changed later. This is in stark contrast to WAP/WML, where applications are always dynamically loaded, and new functions are easily added.

 

The makers of SIM cards are keen to promote the use of dynamically loaded applications, and this functionality is promised for the next version of all three of the operating systems in common use. However, this is an old promise, and the problems with the security of such a system continue to lead to delays.

Phase II with WML

So, is it possible to write a WML browser on a Phase II+ SIM? Well, almost. Obviously, you will need a very powerful SIM (with an associated cost impediment), and you're not going to be able to support graphics, but it's certainly possible to provide basic WML browsing using SMS as the carrier and the SIM to process and display the content.

 

This would mean that non-WAP compliant handsets would still be able to browse the Internet, simply by replacing the SIM. Several telecom companies have already undertaken research into this possibility, but the speed with which WAP handsets are being produced may remove the market for such a product.

Deploying Phase II+ Applications

Because Phase II+ applications have to be written to the SIM before the SIM is in the hands of the customer, it is necessary to make an arrangement with the telecom company that will be distributing the SIMs. (Alternatively, you can be the telecom company!) There is no way (or at least, there shouldn't be a way) of adding applications to a SIM once it is in the hands of the customer.

 

Having said that, telecom companies are generally very keen to add to their offerings, and are eager to talk to companies who can provide new applications. But it is important to remember that every SIM issued will carry the application, so it will need to appeal to a serious percentage of the customer base to be worthwhile.