RRC Inactive Small Data Transmission Using gNB-DU Context Retention
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Solution Overview
Problem
In 3GPP Release 16, user equipment (UE) in the RRC_INACTIVE state does not support data transmission, requiring it to switch to the RRC_CONNECTED state for both downlink and uplink data, leading to unnecessary power consumption and signaling overhead even for small data transmissions.
Innovation Solution
A method and apparatus enabling small data transmission (SDT) by allowing UE to remain in the RRC_INACTIVE state, involving a gNB-CU determining UE context suspension and using UE IDs to maintain context at gNB-DUs, enabling data transmission without transitioning to RRC_CONNECTED state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE switches to the RRC_CONNECTED state for data transmission, then data transmission can be performed, but power consumption and signaling overhead increase unnecessarily
Solution Approach 1:
The patent segments the RRC state machine into distinct states (RRC_IDLE, RRC_CONNECTED, and the new RRC_INACTIVE state). This segmentation allows the UE to remain in a low-power state (RRC_INACTIVE) while still supporting data transmission, thus resolving the contradiction between maintaining data transmission capability and reducing power consumption.
Solution Approach 2:
The patent introduces dynamic state transitions, allowing the UE to flexibly switch between RRC_INACTIVE and RRC_CONNECTED states based on data transmission requirements. This dynamic approach enables the system to optimize power consumption while maintaining data transmission capability when needed.
2Productivity
If the UE switches to the RRC_CONNECTED state for data transmission, then data transmission can be performed, but signaling overhead increases
Solution Approach 1:
By segmenting the RRC state machine and introducing RRC_INACTIVE as an intermediate state, the patent reduces the frequency of full RRC connection establishment and release procedures. This segmentation allows data transmission to occur in the RRC_INACTIVE state with minimal signaling, thus reducing signaling overhead while maintaining data transmission capability.
Solution Approach 2:
The patent implements partial connection maintenance in the RRC_INACTIVE state, where essential data transmission functionality is preserved without the complete overhead of full RRC connection management. This partial action approach reduces signaling overhead while sufficient for small data transmissions.
3Use of energy by moving object
If the UE remains in the RRC_INACTIVE state, then power consumption is reduced, but data transmission is not supported
Solution Approach 1:
The patent makes the RRC_INACTIVE state dynamic by enabling optional data transmission functionality. The UE can transition to this state for power savings, but when data transmission is required, it can perform SDT or transition to RRC_CONNECTED, thus dynamically balancing power consumption and data transmission capability.
Solution Approach 2:
The patent changes the parameters of the RRC_INACTIVE state by introducing new capabilities (SDT support, context suspension/resumption). This parameter change transforms RRC_INACTIVE from a purely idle state to one that can support data transmission, thus resolving the contradiction between power consumption and data transmission capability.
4Productivity
If the UE switches to the RRC_CONNECTED state and then back to RRC_INACTIVE state for each data transmission, then data transmission is completed, but unnecessary power consumption and signaling overhead occur
Solution Approach 1:
The patent applies preliminary action by having the gNB-CU proactively determine and prepare the RRC_INACTIVE state with SDT capabilities before data transmission occurs. The UE context is suspended and prepared in advance, allowing the UE to immediately perform data transmission in RRC_INACTIVE state without unnecessary state transitions, thus preventing energy loss.
Solution Approach 2:
The patent implements feedback mechanisms where the gNB-CU monitors UE data transmission patterns and dynamically determines whether to maintain the UE in RRC_INACTIVE state or transition to RRC_CONNECTED. This feedback loop prevents unnecessary state transitions and associated energy consumption.
Data Source
AI summary
Disclosed are methods for a random access. One embodiment of the subject application provides a method performed by a gNB, including determining a user equipment (UE) to enter an RRC_INACTIVE state by a gNB central unit (gNB-CU), sending a UE context suspension indication and a UE identification (ID) of small data transmission (SDT) to at least one first gNB distributed unit (gNB-DU) by the gNB-CU, storing the UE ID of SDT and keeping a UE context of SDT by the at least one first gNB-DU, and treating the UE in the RRC_INACTIVE state and forwarding a radio resource control (RRC) release manage to the UE by the at least one first gNB-DU, wherein the UE context suspension indication is for indicating the at least one first gNB-DU to keep a the UE context of SDT in the RRC_INACTIVE state, and the UE ID of SDT is for identifying the UE context of SDT. Related apparatuses are also disclosed.