RRC Inactive Small Data Transmission With SDT Timer Control
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Solution Overview
Problem
User equipment in a radio resource control inactive state (RRC_INACTIVE) cannot perform uplink data transmission or downlink data reception without entering an RRC connected state, leading to unnecessary energy consumption and signaling overhead, particularly when small data transmission is required, and RNAU timer expiration interrupts ongoing data transmission.
Innovation Solution
Implement a data transmission method that allows user equipment in RRC_INACTIVE to communicate with a base station without entering an RRC connected state by setting an RNAU timer and an SDT timer, configuring a small data transmission DRB, and managing timers and indications from lower layers to control RRC resume procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If user equipment in RRC_INACTIVE establishes RRC connection to transmit small data, then data transmission capability is improved, but energy consumption and signaling overhead increase
Solution Approach 1:
The patent segments the RRC connection establishment process by introducing a two-stage approach: first establishing a simplified connection for small data transmission, then optionally transitioning to full RRC connection only when necessary. This segmentation allows the system to maintain minimal connectivity for small data packets without incurring the full overhead of traditional RRC connection establishment.
Solution Approach 2:
The patent applies partial action by implementing a simplified connection establishment procedure that performs only the essential functions needed for small data transmission, omitting unnecessary signaling steps. The UE can transmit small data with partial RRC procedures, avoiding the complete RRC connection setup that would consume more energy and generate more signaling overhead.
2Reliability
If RNAU procedure is performed during small data transmission, then notification area update is achieved, but data transmission is interrupted and signaling overhead increases
Solution Approach 1:
The patent applies preliminary action by having the UE check the RNAU timer status before initiating small data transmission. If the timer indicates that an RNAU is imminent or ongoing, the UE delays or adjusts the data transmission timing. This preliminary check prevents the interruption scenario by coordinating data transmission with the RNAU procedure timeline.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of a coordination layer between the RNAU procedure and small data transmission. This intermediary monitors both processes and mediates their interaction, ensuring that data transmission packets are scheduled around RNAU events rather than being interrupted by them, thus maintaining data transmission continuity while still achieving timely RNAU.
3Reliability
If RRC connection is established for small data transmission, then uplink data transmission is enabled, but signaling overhead increases
Solution Approach 1:
The patent extracts the essential data transmission functionality from the complete RRC connection establishment process. By separating the core uplink transmission capability from the full RRC signaling sequence, the system can enable uplink data transmission with minimal signaling. The unnecessary signaling elements are taken out, leaving only the critical path needed for small data packets.
Solution Approach 2:
The patent implements a dynamic connection management approach where the RRC connection state is flexibly adjusted based on data transmission needs. For small data packets, the system dynamically uses a simplified connection mode with reduced signaling, and only transitions to full RRC connection when the data volume or transmission requirements warrant it. This dynamic adaptation minimizes signaling overhead while maintaining uplink transmission capability.
Data Source
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AI summary
A data transmission method, wherein when small data arrives, user equipment (UE) in a radio resource control inactive state RRC_INACTIVE can establish a communication with a base station without entering an RRC connected state, so as to perform small data transmission (SDT). An RNAU timer for controlling a periodic radio access network (RAN) based notification area update is set for the base station. For the SDT, an SDT timer for SDT small data transmission is set. A small data transmission data radio bearer (DRB) is configured for the user equipment. When an RRC resume procedure is triggered by arrival of data at the DRB, a high layer triggering small data transmission, or the like, the user equipment starts the SDT timer.