RRC Re-establishment via LTE SCG Fallback
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Solution Overview
Problem
In the initial deployment of 5G NR networks, there is a coverage gap compared to existing LTE networks, leading to user equipment (UE) experiencing radio link failure (RLF) or handover failure (HOF) at the edge of NR cells, prompting the need for seamless RRC connection re-establishment with LTE cells.
Innovation Solution
The UE is configured to support dual connectivity between NR and LTE networks, allowing it to detect MCG failures and suspend bearers, then transmit messages to an LTE SCG cell for RRC connection re-establishment, potentially skipping the random access channel procedure for the new cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If UE uses NR network for communication, then data rate and network capacity are improved, but coverage reliability deteriorates at cell edges due to RLF/HOF
Solution Approach 1:
The patent implements dynamic switching between NR and LTE networks based on real-time connection status. When MCG failure is detected, the UE dynamically transitions from NR (MCG) to LTE (SCG) network, allowing flexible adaptation between high-speed NR and reliable LTE coverage areas
Solution Approach 2:
The patent introduces an intermediary mechanism where the SCG cell (LTE) serves as a backup and recovery point when the MCG cell (NR) fails. The configuration allows the UE to use the SCG as an intermediate step for RRC connection re-establishment, ensuring continuous communication without direct NR-to-NR failures
2Reliability
If UE performs traditional RRC re-establishment procedure, then connection recovery is achieved, but handover time and service interruption increase
Solution Approach 1:
The patent performs preliminary configuration where the SCG cell is pre-configured with necessary parameters and the UE stores re-establishment information before failure occurs. When MCG failure happens, this pre-prepared configuration enables immediate transition to SCG without time-consuming reconfiguration procedures
Solution Approach 2:
The patent skips the traditional random access channel (RACH) procedure by directly transmitting an RRC re-establishment message to the SCG cell using existing uplink resources. This rushing through of the RACH step significantly reduces handover time and service interruption duration
3Productivity
If operators deploy NR network with limited coverage, then network capacity and advanced features are improved, but coverage area deteriorates compared to LTE
Solution Approach 1:
The patent segments the network coverage into two parts: NR network for high-capacity service in available areas and LTE network for broad coverage areas. The dual connectivity configuration allows the system to utilize both network segments effectively, with NR providing enhanced capacity where available and LTE providing fallback coverage where NR is absent
Solution Approach 2:
The patent makes the UE capable of operating in multiple network modes (NR-only, LTE-only, or dual connectivity), allowing the same UE to universally access both NR and LTE networks. This multi-functionality enables the system to leverage the coverage advantages of LTE while enjoying the capacity benefits of NR
Data Source
AI summary
Provided are a method of performing RRC establishment procedure a device supporting the method. According to one embodiment of the present invention, the method includes: configuring a master cell group (MCG) cell and a secondary cell group (SCG) cell; receiving configuration related to MCG failure; detecting the MCG failure on the MCG cell; suspending MCG bearer and MCG transmission of split bearer; and transmitting a message to the SCG cell based on the configuration.