UE Context Retrieval for Small Data Transmission in RRC Inactive
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Solution Overview
Problem
Current specifications do not adequately address UE context retrieval and data forwarding for Small Data Transmission (SDT) in the RRC_INACTIVE state, particularly when deciding whether to relocate the anchor for UE context to a new network node.
Innovation Solution
A method where a new network node requests an old network node for UE context retrieval and data forwarding, with the old network node deciding whether to relocate the anchor, using existing XnAP signaling to support Small Data Transmission (SDT) without impacting the UE side, and incorporating SDT indicators and assistance information in the request and response messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If UE context retrieval is performed for SDT in RRC_INACTIVE state, then data forwarding capability is improved, but network node complexity increases
Solution Approach 1:
The XnAP Retrieve UE Context procedure is enhanced to serve dual purposes: traditional RRC connection resumption and SDT in RRC_INACTIVE state. By making the procedure universal, the network node can handle both scenarios using the same signaling mechanism, avoiding the need for separate complex procedures and thus improving data forwarding capability without proportionally increasing complexity.
Solution Approach 2:
The patent introduces SDT indicators and assistance information as new parameters in the Retrieve UE Context procedure. These parameters enable the old network node to identify when SDT is required and make informed decisions about anchor relocation. By changing the procedure to include these specific parameters, the system achieves efficient SDT support while maintaining compatibility with existing signaling frameworks.
2Productivity
If anchor relocation is performed for UE context, then data forwarding efficiency is improved, but signaling overhead increases
Solution Approach 1:
The patent implements dynamic anchor relocation decisions based on real-time network conditions and UE requirements. The old network node evaluates factors such as data volume, network load, and UE location to determine whether anchor relocation is beneficial. This dynamic approach allows the system to achieve high data forwarding efficiency when needed while avoiding unnecessary relocation signaling, thus balancing productivity gains with overhead minimization.
Solution Approach 2:
Instead of always performing full anchor relocation, the system applies partial actions by selectively relocating the anchor only when necessary for SDT operations. The old network node uses assistance information to determine the minimum required action, which may be less than full context transfer. This partial action approach reduces signaling overhead while maintaining sufficient data forwarding efficiency for small data transmissions.
3Device complexity
If existing XnAP signaling is reused for SDT, then implementation complexity is reduced, but protocol compatibility challenges arise
Solution Approach 1:
The patent embeds SDT-specific functionality within the existing XnAP Retrieve UE Context procedure structure. The SDT indicators and assistance information are nested as optional fields within the standard procedure messages. This nesting approach allows the system to reuse existing signaling frameworks, reducing implementation complexity, while the optional nature of the new fields maintains backward compatibility with older network nodes that do not support SDT.
Solution Approach 2:
The patent incorporates SDT indicators and assistance information at the beginning of the Retrieve UE Context procedure, allowing the old network node to prepare for SDT operations in advance. By performing preliminary identification and classification of SDT requirements early in the procedure, the system can efficiently handle protocol compatibility issues and prepare appropriate responses before the main data forwarding operations begin, thus reducing overall implementation complexity.
Data Source
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AI summary
Systems and methods for User Equipment (UE) context retrieval and data forwarding to support Small Data Transmission (SDT) are provided. In some embodiments, a new network node can request an old network node for UE context retrieval and data forwarding if the UE in RRC_INACTIVE state sends small data to the new network node. In some embodiments, the old network node decides whether to relocate the anchor for UE context to the new network node or rejects the relocation. The request includes either or both of (a) an indication that the UE context retrieval is related to a SDT performed by the UE and (b) UE assistance information that informs the old network node that the UE has started a SDT procedure.