Core Network Mediator for Wireless Device Mobility Data Loss
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Solution Overview
Problem
In wireless communication systems, particularly with RedCap UEs in RRC-Inactive state using long eDRX, there is a challenge in handling DownLink data mobility, leading to potential data loss when UEs move between radio access network notification areas without connectivity, causing buffered data to be lost as it cannot be forwarded to the new serving node.
Innovation Solution
A method where the first radio network node requests assistance from the core network to retrieve the UE context and buffered data using temporary identifiers, enabling the core network to aid in data forwarding even across nodes without direct connectivity, thus preventing data loss during mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the UE uses long eDRX in RRC-Inactive state to conserve energy, then the UE can sleep for longer periods (1-3 hours), but DL data may arrive and be buffered at a previous radio network node that loses connectivity with the UE's new serving node, causing data loss
Solution Approach 1:
The core network node acts as an intermediary to retrieve buffered DL data from the previous radio network node when the new serving node cannot access it directly. The core network receives a request from the new radio network node, retrieves the UE context and buffered data using the temporary identifier, and forwards it to the new serving node, ensuring data delivery despite loss of direct connectivity between RAN nodes
Solution Approach 2:
The system performs preliminary actions by buffering DL data at the previous radio network node before the UE moves out of coverage. The data is held in buffer until the UE returns or until the core network can retrieve it, preventing immediate data loss while the UE is in long eDRX sleep mode
2Adaptability or versatility
If the UE moves between radio access network notification areas with no connectivity between nodes, then the UE can maintain RRC-Inactive state, but buffered DL data at the previous node cannot be forwarded to the new serving node
Solution Approach 1:
The core network serves as a mediator that bridges the connectivity gap between RAN nodes. When the new serving node cannot directly communicate with the previous node, it requests assistance from the core network, which retrieves the buffered data using the temporary identifier and forwards it to the new node, preventing data loss during mobility
Solution Approach 2:
The core network creates a copy of the buffered DL data and UE context from the previous radio network node and transfers it to the new serving node. This copying mechanism ensures data availability even when direct node-to-node connectivity is lost during UE mobility
3Reliability
If the core network retrieves UE context from a previous radio network node using temporary identifier, then DL data can be forwarded across nodes without direct connectivity, but additional signaling overhead is introduced
Solution Approach 1:
The core network acts as an intermediary that simplifies the data retrieval process despite introducing signaling messages. The temporary identifier-based request mechanism reduces complexity compared to maintaining direct Xn interface connectivity between all possible RAN nodes, as the core network centralizes the context retrieval function
Data Source
AI summary
A method is disclosed, performed by a first radio network node, for handling mobility of a wireless device connected to a core network node. The first radio network node is outside a radio access network notification area (RNA) associated with the wireless device. The method comprises receiving, from the wireless device, one or more message(s) indicating that the WD has moved outside the RNA. The at least one message comprises a temporary identifier assigned to the WD. The method comprises sending to the core network node, upon failing to retrieve a User Equipment (UE) context for the WD directly from the RNA, a message requesting assistance in retrieving the UE context of the WD, wherein the message comprises a temporary identifier assigned to the WD.