Dual Active Protocol Stack for Seamless Inter-Master Node Handover
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Solution Overview
Problem
In cellular networks, handovers between user equipment (UE) and network nodes can cause disruptions in data transmission due to changes in master and secondary node connections, particularly in scenarios involving dual active protocol stacks and secondary cell group bearers, leading to potential data interruptions during inter-master node handovers.
Innovation Solution
The implementation of a dual active protocol stack (DAPS) in user equipment (UE) and network nodes, which allows for seamless handovers by establishing and managing dual security layers and common or separate Medium Access Control (MAC) entities, enabling continuous data transmission using both the source and target keys during the handover process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a handover procedure is performed in conventional cellular networks, then the UE can switch from one master node to another, but data transmission is interrupted during the handover process
Solution Approach 1:
The dual active protocol stack is established before the handover is triggered, with both source and target protocol stacks being configured and ready. The target protocol stack is set up in advance with all necessary parameters and security keys, so that when handover is initiated, the UE can immediately switch to using the target stack without interruption to data transmission.
Solution Approach 2:
During the handover process, both the source and target protocol stacks remain active simultaneously. Data transmission continues uninterrupted through the target protocol stack while the source protocol stack remains operational until the handover is complete. This ensures continuous useful action (data transmission) throughout the handover process rather than having gaps where transmission stops.
2Reliability
If the MAC entity is reset during handover to ensure security, then security is maintained, but data transmission is disrupted
Solution Approach 1:
The target MAC entity is configured and ready in advance before handover, with all security parameters and keys pre-established. When handover is triggered, the UE can immediately activate the target MAC entity without needing to reset it, thereby maintaining both security and continuous data transmission.
Solution Approach 2:
The system dynamically switches between source and target MAC entities based on handover state. Both MAC entities can be active simultaneously during the transition period, with the target MAC entity becoming operational without requiring a reset, allowing seamless switching while maintaining security through proper key management.
3Reliability
If dual active protocol stack is established with both source and target keys, then data transmission continuity is improved, but device complexity increases
Solution Approach 1:
The protocol stack is segmented into distinct source and target components, each with its own security context and parameters. This segmentation allows independent management of each stack, making the complexity more manageable by organizing it into separate, well-defined modules rather than a monolithic structure.
Solution Approach 2:
The dual active protocol stack design creates a universal framework that can handle both source and target connections simultaneously. The same protocol stack structure and management mechanisms are used for both source and target, allowing the system to manage multiple active connections through a unified approach rather than requiring separate specialized handling for each.
Data Source
AI summary
A method is disclosed, e.g. performed by a user equipment, the method comprising: establishing a connection to a first master node, receiving a first reconfiguration message including configuration information for a secondary node addition including a first key, performing a random access to the secondary node, transmitting and/or receiving data towards/from the secondary node on one or more secondary cell group bearers using the first key, receiving a second reconfiguration message relating to an inter-master node handover from the first master node to a second master node, the reconfiguration message comprising configuration information relating to a dual active protocol stack (DAPS) for one or more secondary cell group bearers associated with the secondary node and a second key; establishing the dual active protocol stack for the one or more secondary cell group bearers of the secondary node based on the configuration information; transmitting and/or receiving data towards/from the secondary node on the one or more secondary cell group bearers using the first key hosted by the dual active protocol stack for the one or more secondary cell group bearers; performing a random access to the second master node; transmitting a reconfiguration complete message to the second master node; and transmitting and/or receiving data towards/from the secondary node for the one or more secondary cell group bearers using the second key hosted by the dual active protocol stack for the one or more secondary cell group bearers. Related methods that may be performed by network nodes are disclosed. Further, a corresponding system and corresponding apparatuses, computer programs, and computer-readable storage media are disclosed.