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GSM (SAT - 1) - 33

SIM Application Toolkit - SAT [Under GSM]
» ME-SIM interface, 11.11 «
» SAT, 11.14 «

On your GSM mobile, you may have observed a operator specific menu like Hutch plus . If you put SIM from different GSM operator, you will see menu changed to new operator. Typically this menu will have options or sub-menus for services like get latest news on sports, download latest ring tones, buy movie tickets etc. From where this menu comes ? The answer is SIM Application Toolkit or SAT.

SAT is a way by which SIM can use ME to provide operator specific services or applications. Let us take above example of displaying operator specific menu to user.

For SAT to work, both SIM and ME need to support SAT service. ME comes to know about SIM capabilities by reading SIM (EF) file called SIM Service table (EFsst). SIM is made aware of ME capabilities by ME sending a command Profile Download containing ME capability information to SIM. This communication happen during SIM activation. For displaying menu, SIM sends proactive SAT command, SETUP MENU (assuming both SIM and ME support it) which contain MENU information like menu title (called alpha identifier), menu items etc. When user selects one of the menu items, ME informs this to SIM as MENU selection . Application in SIM can then take further action. The further action could be sending SMS, displaying text etc. which would be specification provided SAT command.

Above example describes what is called Proactive SIM which allow SIM to request ME to do certain actions for SIM. Examples are SETUP MENU, SEND SMS, SET UP CALL, PROVIDE LOCAL INFO etc.

Another important functionality provided by SAT is Call/SMS control by SIM . If this is active, when user makes a call, before invoking Call Control procedure, ME first informs SIM about call being made (containing number to which call is being made and other information). SIM has to give go ahead for call to proceed. SIM may reject the call (ME then does not proceed with call, it just informs user that call rejected by SIM), may modify the number (ME proceeds with the call but with different number provided by SIM), or may allow call to proceed as usual (ME proceeds with call as usual). Similar rules apply for SMS control by SIM.

There is also functionality called Event download . If active, ME need to inform SIM when certain events happen like location area change. The list of events to be monitored are given by SIM in proactive SIM command SET UP EVENT LIST after which ME start monitoring it.

SAT provide number of such mechanisms and functionalities using which lot of different features/services can be thought of.

Before we see example, a word about ME - SIM interface. As per 3GPP 11.11, ME works as master and SIM as slave. ME sends commands to SIM (like SELECT and READ RECORD commands to read file from SIM). SIM responds back with result. Proactive SIM commands require SIM to work as master. This is achieved in roundabout way: when SIM responds for command sent by ME after execution, it uses result code 90 to indicate successful execution of command. But when it has proactive SIM command to be sent, it uses a result code 91 to indicate not only successful execution of current command but also that it wants to send proactive SIM command. ME then has to send FETCH command and SIM responds back with proactive SIM command. For this procedure to work even when ME is not sending any SIM commands, proactive polling is used. In proactive polling, ME sends STATUS command periodically. This allows SIM to indicate if it wants to send proactive command as described above.

In next chapter, we will an example.

References: None.

Copyright © Samir Amberkar 2010§

Inside MS Layer 3 - Call Rel « GSM Index » SAT - 2