SRNC UICC Type Identification for Inter-RAT Handover
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Solution Overview
Problem
Current solutions for inter RAT handover in UTRAN to E-UTRAN do not effectively identify the type of UICC in a UE, leading to inefficient handover decisions and resource allocation, particularly for USIM-less UEs, which are not allowed to perform handovers due to lack of E-UTRA capability indication.
Innovation Solution
The SRNC analyzes security keys received from the SGSN using known key conversion functions to determine the type of UICC, allowing handover to E-UTRAN only if the UE has a valid USIM or if the ongoing service is an emergency call, thereby enabling handover for UEs with GSM subscriptions during emergency situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SRNC configures the UE to perform measurements on E-UTRA cells, then handover preparation is enabled, but resource waste occurs if handover is later rejected due to UICC type limitations
Solution Approach 1:
The SRNC performs preliminary identification of the UICC type (SIM vs USIM) by analyzing security keys before initiating E-UTRA measurements or handover preparation. This preliminary action prevents configuration of measurements that would later be rejected, thereby avoiding waste of radio resources while ensuring handover success when appropriate
Solution Approach 2:
The security key analysis acts as an intermediary mechanism between the SGSN authentication process and the SRNC handover decision. By extracting UICC type information from security keys received from the SGSN, the system determines eligibility for E-UTRA handover without requiring direct communication between the UICC and SRNC
2Productivity
If the SRNC restricts handover to USIM-equipped UEs only, then resource allocation is optimized, but service continuity is interrupted for SIM-equipped UEs during emergency calls
Solution Approach 1:
The system applies different handover policies based on the specific service context and UICC type. For normal services, only USIM-equipped UEs are allowed to handover to E-UTRAN. For emergency calls, SIM-equipped UEs are also permitted to handover. This localized quality adjustment ensures resource efficiency for regular traffic while maintaining service continuity for emergency situations
3Reliability
If the network performs full AKA authentication procedures, then security is ensured, but signaling overhead increases
Solution Approach 1:
The system extracts the essential UICC type identification information from the security keys already generated during the AKA authentication process. Instead of performing additional authentication procedures or requiring separate UICC type indication messages, the SRNC derives the necessary information (SIM vs USIM) by analyzing the security keys received from the SGSN, thereby avoiding additional signaling overhead
Data Source
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AI summary
The invention relates to a method and arrangement in a serving Radio Network Controller, SRNC for controlling inter RAT handover to E-UTRAN of a UE with E-UTRA capability operating in a serving network comprising said SRNC, wherein the SRNC receives, from a Serving GPRS Support Node, SGSN, security keys generated at authentication and key agreement, AKA, upon attachment of the UE to the serving network; characterized in the steps of - determining (202) which type of UICC the UE is equipped with by analyzing the security keys received from SGSN; - using the knowledge of which type of UICC the UE is equipped with to base a decision (204) on whether to allow handover of the UE to E-UTRAN.