5G Small Data Transmission for Additional Uplink Data in RRC Inactive
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Solution Overview
Problem
Existing small data transmission (SDT) procedures in the RRC inactive state of a 5G NR system are inefficient due to the inability of user equipment (UE) to indicate additional data in the buffer during an ongoing transmission, leading to resource wastage and increased latency when transitioning to the RRC connected state.
Innovation Solution
The UE is enabled to transmit an indication for new data during an ongoing small data transmission procedure, allowing simultaneous transmission of additional data without transitioning to the RRC connected state, using mechanisms like scheduling requests and buffer status reports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE waits until the SDT procedure is complete before transmitting additional data, then the RRC-based SDT procedure can be properly executed with authentication and context retrieval, but the additional data becomes available only after the first SDT transmission, causing the UE to initiate a new SDT procedure after the ongoing procedure ends, leading to resource inefficiency and increased PRACH collision probability
Solution Approach 1:
The network pre-configures uplink resources (PUSCH) and associated transmission parameters for the UE before the SDT procedure completes. This preliminary configuration enables the UE to transmit additional data that becomes available during the ongoing SDT procedure without initiating a new random access procedure, thereby improving transmission efficiency while maintaining reliable procedure completion
Solution Approach 2:
The system transitions from a static resource allocation approach to a dynamic one where the network can allocate additional uplink resources during the ongoing SDT procedure based on UE data availability. This dynamic resource configuration allows the UE to adapt to new data arrivals without leaving the inactive state or restarting the SDT procedure
2Reliability
If the UE transitions to RRC connected state to transmit additional data, then complete data transmission capability is available, but significant delay occurs due to Xn latency (20-30 ms) for UE context retrieval procedure
Solution Approach 1:
The network performs preliminary actions by pre-configuring uplink resources and transmission parameters before the SDT procedure completes. This allows the UE to remain in the inactive state and transmit additional data without triggering the time-consuming Xn latency associated with full RRC connected state transitions and context retrieval procedures
Solution Approach 2:
The system uses a simplified version of the connected state resources - pre-configured PUSCH resources with associated parameters - that replicate the essential data transmission capability of the connected state without requiring full context retrieval. This copying approach provides sufficient functionality for small data transmissions while avoiding the time penalty of complete state transitions
3Productivity
If the network sends RRC release message in the same MAC payload with contention resolution, then the SDT procedure can be concluded efficiently, but the network may need to wait to see whether DL data arrives or waiting for UE context to be fetched
Solution Approach 1:
The SDT procedure is segmented into distinct phases: the contention resolution phase and the resource configuration phase. The network can send the RRC release message in the same MAC payload with contention resolution to efficiently conclude the procedure, while separately pre-configuring uplink resources that remain available for additional data transmissions, thus maintaining both efficiency and completeness
Data Source
AI summary
The invention inter alia relates to a user equipment comprising means configured to transmit, to the network, first data in a small data transmission procedure in a non-connected state; and during said small data transmission procedure in the non-connected state, transmit, to the network, an indication for transmission of second data, the second data becoming available for transmission after said first data having been transmitted.