RRC State Resumption Using CU-DU SRB Context Coordination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is no effective solution for transitioning between the RRC inactive state and the connected state in the case of CU-DU separation in the 5G NR standard.
Innovation Solution
The RRC state transition method involves using a newly allocated SRB configuration to resume the RRC connection by replacing the existing SRB configuration, facilitated by the CU and DU, which manage and process terminal context separately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the gNB releases the RRC connection to transition the terminal to RRC inactive state, then power consumption of terminals is reduced and signaling overhead is reduced, but the terminal cannot quickly resume data transmission without proper context management between CU and DU
Solution Approach 1:
The gNB is segmented into CU and DU with separate context management. The CU maintains the RRC connection context while the DU maintains the radio resource context, allowing the terminal to transition to RRC inactive state with reduced power consumption while ensuring reliable data transmission can be resumed by coordinating between CU and DU context information
Solution Approach 2:
The F1 interface acts as an intermediary between CU and DU, enabling context information exchange. When the terminal needs to resume data transmission, the CU and DU can exchange necessary context information through the F1 interface to ensure reliable connection restoration without requiring the terminal to maintain continuous monitoring
2Reliability
If the terminal monitors the downlink control channel continuously to maintain RRC connected state, then data transmission reliability is maintained, but signaling overhead increases and power consumption increases
Solution Approach 1:
The system dynamically transitions the terminal between RRC connected and inactive states based on data transmission requirements. During inactive state, the terminal does not monitor the downlink control channel, reducing power consumption. When data transmission is needed, the terminal can transition back to connected state through uplink data transmission or RRC resume procedures, ensuring reliability is maintained when needed
3Loss of energy
If the RRC connection is released to reduce signaling overhead, then power consumption is reduced, but the terminal context information must be properly managed between CU and DU to enable quick resumption
Solution Approach 1:
Context information is segmented and stored separately in CU and DU. The CU stores RRC connection context including security parameters and configuration, while the DU stores radio resource context including scheduling information. This segmentation allows for efficient context management and quick resumption by retrieving only necessary information from each unit
Solution Approach 2:
When the terminal transitions to RRC inactive state, the CU and DU perform preliminary actions to preserve necessary context information. The CU maintains the RRC connection context and the DU maintains the radio resource context, so that when the terminal needs to resume, the context is already prepared and can be quickly restored without complex real-time negotiations
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Disclosed are a Radio Resource Control (RRC) state transition method, a terminal, a Centralized Unit (CU), a Distributed Unit (DU) and a computer-readable storage medium. The RRC state transition method includes: when a terminal changes from a current state to an RRC connected state, the terminal requests to resume an RRC connection by using an existing Signaling Radio Bearer (SRB) configuration; when the terminal receives a response from a Distributed Unit (DU) for request of resuming the RRC connection, if the response comprises a newly allocated SRB configuration, the terminal replaces the existing SRB configuration with the newly allocated SRB configuration to resume the RRC connection.