5G RRC Connection Reestablishment via Cell Type Detection
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Solution Overview
Problem
Existing methods for reestablishing an RRC connection after handover failure are not applicable to the 5G system, leading to service disruptions and failed reconnection attempts.
Innovation Solution
A method where the terminal device determines whether the RAT of the first cell is the same as the source cell and whether the first cell is a first-type cell, and based on this, decides whether to send a connection release cause value to the upper layer or an RRC connection reestablishment request to the reselected base station, effectively increasing the probability of resuming the RRC connection and reducing signaling exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device uses the conventional RRC connection reestablishment method after handover failure, then the procedure is simple, but the connection resumption fails in 5G systems with different RATs
Solution Approach 1:
The patent changes the decision parameters for connection reestablishment by introducing judgment on whether the first cell is a first-type cell (connected to source core network) and whether RATs match. This parameter-based differentiation enables the terminal to select the appropriate reestablishment path (intra-RAT vs inter-RAT) based on cell type and RAT compatibility, thereby improving connection resumption success rate in 5G systems.
Solution Approach 2:
The patent makes the connection reestablishment procedure dynamic by allowing the terminal to adapt its behavior based on real-time conditions (cell type, RAT match, core network connectivity). The terminal dynamically chooses between sending reestablishment request to same-RAT base station or entering idle mode, optimizing the procedure for each specific scenario rather than using a fixed conventional approach.
2Reliability
If the terminal device sends RRC connection reestablishment request to base station in first cell with different RAT, then connection may be resumed, but signaling exchange increases and service continuity is disrupted
Solution Approach 1:
The patent applies preliminary action by having the terminal device judge whether the first cell is a first-type cell and whether RATs match before initiating connection reestablishment. This preliminary judgment prevents unnecessary signaling exchanges by identifying suitable cells in advance, thereby reducing time loss and maintaining service continuity.
Solution Approach 2:
The patent introduces the concept of first-type cells (cells connected to source core network) as intermediaries that facilitate successful connection resumption. By identifying and selecting first-type cells as target cells for reestablishment, the terminal can resume connection more efficiently without requiring extensive signaling with incompatible base stations, thus reducing time loss.
3Ease of operation
If the terminal device enters idle mode when RAT differs from source cell, then procedure is simple, but connection resumption probability decreases
Solution Approach 1:
The patent changes the operational parameters by introducing cell type classification (first-type vs second-type cells) and RAT matching criteria. This allows the terminal to differentiate between scenarios where entering idle mode is appropriate and scenarios where sending reestablishment request to same-RAT base station is better, thereby improving connection resumption probability while maintaining procedure simplicity through clear decision criteria.
Data Source
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AI summary
Embodiments of this application relate to the field of communications technologies, and disclose a connection reestablishment method and apparatus, to implement connection reestablishment for a terminal device in a 5G system. The method includes: selecting, by a terminal device, a first cell; and when a RAT of the first cell is different from a RAT of a source cell and the first cell is not a first-type cell, leaving, by the terminal device, a connected mode, and sending a connection release cause value to an upper layer, where the connection release cause value comprises at least one of a handover failure, a type of the first cell, a core network type corresponding to the first cell, the RAT of the first cell, whether the first cell is connected to a source core network, a non-access stratum NAS resume indication, a NAS change, and a core network type change, the connection release cause value is used to indicate the upper layer to determine whether to change a type of a core network connected to the terminal device, the first-type cell is a cell connected to the source core network, and the source core network is a core network accessed in the source cell by the terminal device.