RRC Inactive Small Data Transmission With Uplink Timing Alignment
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Solution Overview
Problem
Existing wireless communication systems face issues with frequent Idle-Connected-Idle transitions for small data transmission in RRC_INACTIVE state, leading to increased network signaling load, latency, and power consumption, as well as challenges in maintaining uplink synchronization and resource efficiency.
Innovation Solution
A method for small data transmission (SDT) in RRC_INACTIVE state, involving the configuration of SDT thresholds and Timing Alignment Timers to manage uplink synchronization, allowing data transmission without transitioning to RRC_CONNECTED state, and utilizing various SDT procedures such as 2-step and 4-step RACH-based and configured grant-based methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE transitions to RRC_CONNECTED state for small data transmission, then data transmission can be performed, but network signaling load and latency increase
Solution Approach 1:
The network pre-configures SDT parameters including uplink resources, downlink resources, and timing advance commands while the UE is in RRC_INACTIVE state. This preliminary configuration enables the UE to perform small data transmission immediately without transitioning to RRC_CONNECTED, thereby reducing signaling latency while maintaining data transmission capability.
2Productivity
If the UE transitions to RRC_CONNECTED state for small data transmission, then data transmission can be performed, but network signaling load increases
Solution Approach 1:
The patent extracts the essential data transmission functionality from the RRC_CONNECTED state and enables it to operate independently in RRC_INACTIVE state through SDT. By separating small data transmission from the full connection establishment process, the network signaling load is significantly reduced while maintaining data transmission capability.
3Quantity of substance
If the UE stays in RRC_INACTIVE state for small data transmission, then signaling overhead is reduced, but uplink synchronization becomes difficult to maintain
Solution Approach 1:
The network provides preliminary timing advance commands and uplink configuration parameters before the UE enters RRC_INACTIVE state. These pre-configured parameters enable the UE to maintain uplink synchronization for small data transmissions without requiring frequent synchronization updates, thereby reducing signaling overhead while maintaining synchronization reliability.
4Productivity
If the UE frequently transitions between RRC_IDLE and RRC_CONNECTED states, then data transmission can be performed, but power consumption increases
Solution Approach 1:
The patent enables continuous small data transmission in RRC_INACTIVE state without requiring transitions to RRC_CONNECTED. By maintaining the UE in the lower-power RRC_INACTIVE state while allowing data transmission through pre-configured resources, the power consumption is significantly reduced while maintaining data transmission capability.
Data Source
AI summary
A method for small data transmission (SDT) in RRC_INACTIVE state and related devices are provided. The method includes receiving a SDT configuration, which is used for configuring SDT UL grant, wherein the SDT configuration comprises a SDT threshold; based on the SDT threshold, determining which type of SDT procedures is to be applied in RRC_INACTIVE state; upon reception of a Timing Advance (TA) command in the RRC_INACTIVE state, applying the TA command, and starting or restarting Timing Alignment Timer (TAT) for keeping uplink (UL) time alignment during SDT in the RRC_INACTIVE state; and applying the determined SDT procedure based on the started or restarted TAT, wherein the SDT configuration and/or the SDT UL grant is sustained even if the TAT expires. With this method, UL synchronization/timing maintenance in RRC_INACTIVE state is realized.