Question: What is the primary purpose of utilizing the protocol extension mechanism in the UTRAN Iu-BC interface's Service Area Broadcast Protocol (SABP), as per 3GPP standards?
Option 1: To implement mandatory features for ensuring multivendor interoperability.
Option 2: For standardizing existing basic functionalities across all vendors.
Option 3: To temporarily fix known issues in the current standard release.
Option 4: For integrating operator-/vendor-specific features not part of the basic standardized functionality, or for research on new algorithms/features before potential standardization.
Explanation: The protocol extension mechanism is designed for accommodating special operator- or vendor-specific features not considered part of the fundamental, standardized functionality required for interoperability. It also allows vendors to test and evaluate new features before they might be proposed for standardization, without altering the basic, standardized operations of the SABP.