PDN Context Retention for Fast WiFi to LTE Handover
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Solution Overview
Problem
Current handover procedures in wireless communications networks between 3GPP and non-3GPP access technologies, such as LTE and WiFi, result in high signaling loads and latency due to extensive communication rounds between network nodes, leading to inefficient handover processes.
Innovation Solution
Maintaining the PDN connection context for a predetermined time period when handing over from 3GPP to WiFi, allowing for subsequent handovers back to 3GPP without the need for detach procedures, thereby reducing the number of communication rounds and signaling loads by reusing the existing PDN connection context.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the standard attach procedure is followed for handover from WiFi to LTE, then the handover can be completed with proper network registration, but the signaling load increases and handover latency increases due to multiple communication rounds between network nodes
Solution Approach 1:
The network node performs preliminary actions by maintaining the PDN connection context in an active state for a predetermined time period after the mobile terminal hands over to WiFi. This preliminary maintenance of context allows the network to quickly restore LTE connectivity when the terminal returns, avoiding the need for full detach and re-attach procedures, thus reducing handover latency while ensuring reliable handover completion
Solution Approach 2:
Instead of performing complete detach and re-attach procedures, the system uses a simplified context restoration process that copies or reuses the previously maintained PDN connection context. This copying approach eliminates the need for repeated signaling rounds with HSS, SGW, and PGW, significantly reducing handover latency while maintaining handover reliability
2Reliability
If the standard attach procedure is followed for handover from WiFi to LTE, then proper network registration is achieved, but the signaling load on network nodes increases due to multiple communication rounds
Solution Approach 1:
The network node performs preliminary actions by maintaining the PDN connection context in an active state during the WiFi connectivity period. This preliminary context preservation eliminates the need for subsequent detach and re-attach signaling sequences, reducing the signaling load on MME, SGW, PGW, and HSS while ensuring proper network registration is achieved through the simplified context restoration process
Solution Approach 2:
The invention extracts and removes the unnecessary detach and re-attach signaling steps from the handover procedure. By taking out these redundant communication rounds between network nodes and maintaining context locally, the signaling load is significantly reduced while the essential network registration function is preserved through context restoration
3Loss of time
If PDN connection context is maintained for a predetermined time period, then handover latency is reduced and signaling load is decreased, but network node memory usage increases
Solution Approach 1:
The network node applies partial action by maintaining PDN connection context for only a predetermined, limited time period rather than indefinitely. This partial maintenance strategy reduces memory usage compared to permanent storage while still being sufficient to cover typical WiFi connectivity durations, achieving the right balance between reducing handover latency and managing memory resources efficiently
Solution Approach 2:
The system changes the temporal parameter of context maintenance by introducing a predetermined time period threshold. Context is maintained actively only within this time window, after which it is released. This parameter-based control optimizes the balance between handover performance and memory consumption, ensuring low latency for typical WiFi usage patterns while preventing excessive memory accumulation
Data Source
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AI summary
The present invention relates to a network node and a method at the network node of handing over a mobile terminal between a first RAT and a second RAT in a wireless communications network. The invention further relates to a computer program performing the method according to the present invention, and a computer program product comprising computer readable medium having the computer program embodied therein. A method at a network node of a packet core network of performing handover of a mobile terminal between a first Radio Access Technology (RAT), and a second RAT in a wireless communications network is provided in an embodiment of the present invention. The method comprises receiving a request for handover of the mobile terminal to the second RAT, establishing a PDN connection with the mobile terminal via the first RAT, and performing handover of the mobile terminal to the second RAT. The method further comprises maintaining PDN connection context for the PDN connection established via the first RAT for a time period, and releasing the PDN connection context at expiry of the time period.