RAT Transfer During Inactive Periods in Active Data Sessions
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Solution Overview
Problem
Current methods for transferring user equipment (UE) between different radio access networks, such as UTRAN and E-UTRAN, are inefficient, particularly when UE remains active and does not enter idle or PCH states, leading to prolonged connection in non-preferred networks even after CS services are terminated.
Innovation Solution
The method involves a UE indicating inactive periods in ongoing packet-switched data sessions to a network node, allowing for proactive transfer to a preferred radio access network (E-UTRAN) using existing mechanisms like PSHO or RWR, with optional CSFB indications to distinguish between service requests and fallback scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE remains in connected mode during active data sessions, then data transmission continuity is maintained, but UE cannot transfer to preferred RAT (E-UTRAN) even when CS service is terminated
Solution Approach 1:
The network node proactively identifies inactive periods in ongoing data sessions and initiates RAT transfer before the inactive period begins. This allows the UE to switch to the preferred E-UTRAN network in advance, ensuring seamless connectivity when data transmission resumes without requiring the UE to enter idle mode.
Solution Approach 2:
The system implements feedback mechanisms where the network node monitors data session activity patterns and uses this information to determine optimal transfer timing. By continuously monitoring session state and providing feedback about inactive periods, the network can dynamically adjust transfer decisions to maintain both data continuity and RAT flexibility.
2Device complexity
If UE transfers to E-UTRAN only after entering idle or PCH states, then transfer mechanism is simple, but transfer time is prolonged and user disturbance increases
Solution Approach 1:
The network node performs RAT transfer in advance during identified inactive periods, rather than waiting for the UE to enter idle or PCH states. This preliminary action reduces transfer time and minimizes user disturbance by completing the handover before the next data transmission event.
Solution Approach 2:
The system dynamically determines transfer timing based on real-time monitoring of data session activity. Instead of following a fixed state-based transfer mechanism, the network adaptively selects transfer moments based on actual session patterns, allowing transfers to occur during connected mode when conditions are favorable.
3Adaptability or versatility
If UE uses standardized LTE Cell Reselection to return to E-UTRAN, then transfer mechanism is standardized, but transfer can only occur in Idle mode or specific PCH states
Solution Approach 1:
The invention extends RAT transfer capability to work in connected mode, not just in idle or specific PCH states. By making the transfer mechanism universal across different UE states, the system maintains flexibility in when transfers can occur while using standardized procedures where applicable.
Solution Approach 2:
The network node acts as an intermediary that coordinates the transfer process, monitoring session activity and initiating transfers at appropriate times. This intermediary function enables standardized transfer mechanisms to work effectively in connected mode by providing the necessary coordination and timing control.
Data Source
AI summary
A network node (16) of a first radio access network is configured to transfer a user equipment (11) from the first radio access network to a second radio access network, wherein the second radio access network has a different radio access technology, RAT, than the first radio access network. The transfer is initiated when the network node receives an indication of an inactive period in an ongoing packet-switched data session from the user equipment, and the network node transfers the user equipment to the second radio access network as a result of said indication.