UE-Initiated Inter-System Transfer for LTE to UMTS Session Continuity
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Solution Overview
Problem
Existing wireless communication systems face challenges in seamless inter-system handover between E-UTRAN and GERAN/UTRAN networks, particularly when a user equipment (UE) has simultaneous circuit switched (CS) and packet switched (PS) sessions, leading to unpredictable network behavior due to the inability of RNCs and BSCs to handle PS handovers effectively.
Innovation Solution
A method and apparatus for user equipment (UE) to initiate an inter-system transfer of a communication session by listening to both E-UTRAN and GERAN/UTRAN networks, establishing both CS and PS sessions, and transmitting an area update message to the target network to fetch session information, thereby enabling a UE-initiated transfer without triggering network-initiated PS handover procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If network-initiated PS handover is performed from E-UTRAN to UTRAN/GERAN, then the UE's PS session can be transferred, but the handover fails and causes undefined network behavior when the target RNC is different from the S-RNC controlling the UE's CS session
Solution Approach 1:
Instead of having the network initiate the handover from E-UTRAN to UTRAN/GERAN, the patent inverts the approach by having the UE initiate the inter-system transfer. The UE sends a routing area update request to the target UTRAN/GERAN network, which then fetches the PS session information from the E-UTRAN network. This inversion avoids the complexity of coordinating between multiple RNCs while achieving the same handover objective.
2Adaptability or versatility
If the UE registers and camps on both UTRAN/GERAN for CS domain and E-UTRAN for PS domain simultaneously, then voice services and data services can be provided concurrently, but the RNC/BSC cannot handle PS handover requests for UEs with existing CS connections
Solution Approach 1:
The patent segments the handover procedure into two independent parts: the CS session remains managed by the UTRAN/GERAN network while the PS session is transferred separately through a UE-initiated routing area update. This segmentation allows the PS handover to proceed independently without requiring coordination with the CS session's S-RNC, simplifying the overall procedure while maintaining concurrent service capability.
3Productivity
If the E-UTRAN triggers PS handover towards the D-RNC, then the handover can be initiated, but it causes undefined network behavior because only one RNC can act as the UE's S-RNC in UTRAN
Solution Approach 1:
The patent introduces the UE as an intermediary that initiates the transfer by sending a routing area update request to the target D-RNC. The D-RNC then acts as a mediator to fetch the PS session information from the E-UTRAN network's MME. This intermediary approach allows the handover to proceed directly to the correct D-RNC without triggering undefined behavior from improper RNC selection, maintaining both speed and reliability.
Data Source
AI summary
Apparatus and methods for a user equipment (UE) to initiate an inter-system transfer of a communication session include listening for communications from a first and a second technology type network. Further, the aspects include establishing a circuit switched session with the first technology type network and establishing a packet switched session with a serving node of a first one of the first or the second technology type network. Also, the aspects include determining to transfer the packet switched session to a target node of a second one of the first or the second technology type network. Additionally, the aspects include transmitting a message, by the UE, to the target node, thereby causing the technology type network of the target node to fetch information about the packet switched session from the other network of the serving node in order to effect the transfer and continuation of the packet switched session.