RRC Inactive State Data Transmission Latency Reduction
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Solution Overview
Problem
In wireless communication systems, there is a challenge in efficiently managing data transmissions in the Radio Resource Control (RRC) INACTIVE state due to limited resources, particularly in reducing latency for transitioning to the RRC_CONNECTED state when non-SDT data needs to be transmitted, as existing methods face delays in handling DCCH non-SDT data indications during Small Data Transmission (SDT) procedures.
Innovation Solution
The method involves generating Small Data Transmission (SDT) data units that can be transmitted in the RRC INACTIVE state, triggering an SDT procedure, generating an indication message for non-SDT data units, and transmitting this message via a Dedicated Control Channel (DCCH) during the SDT procedure, allowing for potential transition to the RRC_CONNECTED state even if the DCCH non-SDT data indication message is not transmitted, by sending an RRC Resume Request message through a Common Control Channel (CCCH) if an uplink grant is not available.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the UE waits for uplink grant availability during SDT procedure to transmit non-SDT data, then resource utilization is improved, but transmission latency increases
Solution Approach 1:
The UE transmits the indication message for non-SDT data during the SDT procedure itself, before the uplink grant is confirmed available. This preliminary action allows the network to prepare for the upcoming data transmission, reducing the overall latency while still waiting for resource availability confirmation.
Solution Approach 2:
Instead of pausing the SDT procedure to wait for uplink grant availability before indicating non-SDT data, the UE continues the SDT procedure uninterrupted and transmits the indication message concurrently. This maintains the continuity of the data transmission process and reduces idle waiting time.
2Speed
If the UE transitions to RRC_CONNECTED state immediately to transmit non-SDT data, then transmission speed is improved, but energy consumption increases
Solution Approach 1:
The transmission process is segmented into two phases: first, transmit small data units during the RRC_INACTIVE state using SDT procedure; second, transition to RRC_CONNECTED state only when necessary for larger or more complex data transmissions. This segmentation reduces unnecessary state transitions and associated energy consumption.
Solution Approach 2:
The system dynamically changes the RRC state parameter based on data transmission requirements. For small data units, the UE remains in RRC_INACTIVE state; for non-SDT data or when uplink grant is available, the UE transitions to RRC_CONNECTED state. This parameter change optimizes the balance between transmission speed and energy consumption.
Data Source
AI summary
The present disclosure relates to a method of performing data transmissions in a Radio Resource Control (RRC) INACTIVE state by a user equipment (UE) in a wireless communication system. Especially, the method includes the steps of generating at least one Small Data Transmission (SDT) data unit that can be transmitted in RRC INACTIVE state; triggering a SDT procedure for transmitting the at least one SDT data unit in RRC INACTIVE state; generating a non-SDT data unit that cannot be transmitted in RRC_INACTIVE during the SDT procedure; generating an indication message informing that there is the non-SDT data unit, based on an uplink grant related to the SDT procedure for transmitting the indication message being available; and transmitting the indication message via a Dedicated Control Channel (DCCH) during the SDT procedure to a network.