Question: In a Universal Subscriber Identity Module (USIM) Application Toolkit (USAT), when a Mobile Equipment (ME) encounters an "SMS RP-ERROR" general result, what is the requirement for the first byte of additional information provided by the ME?
Option 1: The first byte shall be a predefined default value ('FF') to indicate an error.
Option 2: The first byte shall be the cause value from the RP-Cause element of the RP-ERROR message, with bit 8 set to 0.
Option 3: The ME is not required to provide any additional information for "SMS RP-ERROR".
Option 4: The first byte must always indicate 'No specific cause can be given' ('00')
Explanation: According to the USIM Application Toolkit specifications, when an "SMS RP-ERROR" occurs, the ME must provide additional information. Specifically, the first byte of this information is mandated to be the cause value extracted from the RP-Cause element of the received RP-ERROR message, with the eighth bit (bit 8) set to 0. This ensures that the USIM (and thereby the network) can accurately diagnose and potentially resolve the issue, utilizing standardized cause values as defined in relevant specifications like TS 24.011 for SMS support on mobile radio interfaces.