Inter-RAT Reestablishment in Multi-RAT Dual Connectivity
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Solution Overview
Problem
Existing dual-connectivity configurations in LTE and NR networks face challenges in efficiently re-establishing radio resource control connections, particularly in multi-RAT scenarios like NE-DC and NGEN-DC, where transitioning to RRC_IDLE mode and re-establishing connections from scratch is time-consuming and resource-intensive.
Innovation Solution
The implementation of methods and procedures that allow a UE to re-establish a connection with a target cell of a different radio access technology (RAT) by verifying integrity and calculating message authentication codes, enabling inter-RAT re-establishment without transitioning to idle mode, and maintaining context information to reduce interruption time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE transitions to RRC_IDLE mode to re-establish connections in inter-RAT scenarios, then connection re-establishment can be performed, but the interruption time and resource consumption increase significantly
Solution Approach 1:
The patent applies preliminary action by maintaining the RRC connected state and context information during inter-RAT re-establishment instead of transitioning to idle mode. The source node stores UE context information including security parameters and configuration data before the handover, enabling the target node to quickly resume the connection without requiring full re-establishment procedures. This preliminary preservation of connection state directly reduces interruption time while maintaining re-establishment capability.
Solution Approach 2:
The patent uses the source node as an intermediary that facilitates the inter-RAT re-establishment process. The source node receives the re-establishment request from the UE, verifies it using stored context information, and then coordinates with the target node to complete the handover. This intermediary role allows the UE to maintain connected state throughout the process, avoiding the time-consuming transition to idle mode while ensuring secure and valid re-establishment.
2Reliability
If the UE transitions to RRC_IDLE mode for inter-RAT re-establishment, then connection can be re-established, but network resource consumption increases
Solution Approach 1:
The source node performs preliminary actions by storing and preserving the UE context information including security parameters, bearer configurations, and radio resource allocations before the inter-RAT handover. This preliminary preservation eliminates the need for the UE to re-negotiate these parameters in the target node, significantly reducing signaling overhead and network resource consumption while enabling efficient re-establishment without idle mode transition.
Solution Approach 2:
The patent implements copying by having the target node obtain and use a copy of the UE context information from the source node during the re-establishment process. Instead of requiring the UE to re-establish all connection parameters from scratch, the target node receives and processes a copy of the contextual data, reducing the computational and signaling resources required for re-establishment while maintaining connection reliability.
3Loss of time
If the UE maintains context information during inter-RAT re-establishment, then interruption time is reduced, but the complexity of managing multiple RAT contexts increases
Solution Approach 1:
The patent applies segmentation by dividing the context management into distinct components: the source node stores and manages the UE context information including security parameters and configuration data, while the target node receives and processes this information during re-establishment. This segmentation of context management responsibilities reduces the complexity burden on the UE by offloading context storage and management to the network nodes, enabling fast re-establishment without significantly increasing device complexity.
Solution Approach 2:
The source node acts as an intermediary that simplifies context management during inter-RAT re-establishment. It maintains the UE context information and provides it to the target node upon receiving a re-establishment request, eliminating the need for the UE to manage and transfer complex context data itself. This intermediary approach reduces device complexity while enabling rapid re-establishment by handling context management in the network rather than at the UE.
4Reliability
If integrity verification is performed using PSCell parameters in inter-RAT scenarios, then security is maintained, but the complexity of verification procedures increases
Solution Approach 1:
The patent applies universality by using the PSCell parameters (physical cell identity and C-RNTI) for multiple purposes: they serve as both the radio resource identifiers for the secondary cell group and as the basis for integrity verification of the re-establishment request. This multi-functional use of existing parameters maintains security verification capability while avoiding the need for separate verification mechanisms, thereby limiting the increase in procedure complexity despite enhanced security requirements for inter-RAT scenarios.
Data Source
AI summary
Embodiments include methods for a target node to establish a connection with a user equipment (UE) operating in dual connectivity (DC) with a PCell utilizing a first radio access technology (RAT) and with a PSCell utilizing a second RAT. Embodiments include receiving, from the UE, a re-establishment request message comprising parameters associated with the PSCell, a first message authentication code (MAC), and an indication of the UE's selection of a target cell served by the target node as a replacement for the PCell. The target cell utilizes the second RAT. Embodiments include verifying the message integrity based on the first MAC, and determining a full UE context based on the plurality of parameters associated with the PSCell and on a successful verification of the message integrity. Embodiments include establishing a connection with the UE based on the full UE context, whereby the target cell serves as a PCell for DC.