Inter-RAT Data Forwarding Without Sequence Numbers
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Solution Overview
Problem
In LTE-NR/5G dual connectivity arrangements, there is a conflict in data forwarding standards during inter-RAT handovers, where the secondary node forwards data with sequence numbers, while the target node expects it without sequence numbers, leading to inconsistencies and increased latency and processing overhead.
Innovation Solution
A method where the master node sends a release request with a 'forward without sequence number' indication to the secondary node, instructing it to strip sequence numbers from data and forward it directly to the target node, bypassing the master node in the data forwarding path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the secondary node forwards data with sequence numbers during inter-RAT handover, then data integrity can be maintained, but it causes inconsistency with target node expectations and increases processing overhead
Solution Approach 1:
The patent changes the parameter of data forwarding by introducing a configuration indicator that specifies whether to forward data with or without sequence numbers. This allows the system to adapt the data forwarding mode (with SN or without SN) based on the specific handover scenario and target node capabilities, resolving the contradiction between maintaining data integrity and reducing processing overhead.
2Device complexity
If the secondary node forwards data through the master node during handover, then data routing is simplified, but it increases latency by adding an extra forwarding hop
Solution Approach 1:
The patent segments the data forwarding path by allowing direct forwarding from the secondary node to the target node, separating the control plane (which still uses the master node for coordination) from the user plane data path. This enables the data path to be optimized for speed while the control path maintains proper coordination, resolving the contradiction between routing simplicity and latency.
3Stability of the object's composition
If the data forwarding path includes the master node, then centralized control is maintained, but it increases latency and processing load
Solution Approach 1:
The patent uses the master node as a control plane intermediary that sets up the direct data forwarding path between the secondary node and target node, then steps out of the data path. The master node mediates the handover process by configuring the direct path and coordinating the transition, while allowing data to flow directly without passing through the master node, thus maintaining control stability while reducing latency.
4Stability of the object's composition
If sequence numbers are included in forwarded data, then data ordering can be ensured, but it creates incompatibility with target node expectations and increases processing overhead
Solution Approach 1:
The patent makes the data forwarding mode dynamic by introducing configuration indicators that can be set differently for different handover scenarios, RAT types, and target node capabilities. The system can dynamically switch between forwarding with sequence numbers and forwarding without sequence numbers, allowing adaptation to different interoperability requirements while maintaining data ordering when needed.
Data Source
AI summary
A method may include receiving, by a secondary node of a third radio access technology (RAT) that is operating as a secondary node for an inter-radio access technology (inter-RAT) dual connectivity connection with a user device from a master node of a first RAT that is operating as a master node for the inter-RAT dual connectivity connection with the user device, a release request including a forward without sequence number indication that instructs the secondary node of the third RAT to forward, without sequence numbers, data for the dual connectivity connection to a target node of a second RAT, wherein the second RAT is different than the first RAT; and forwarding, by the secondary node of the third RAT towards the target node of the second RAT, via a data forwarding path that omits the master node of the first RAT, data without sequence numbers to the target node.