RLC Context Storage for Low-Latency Small Data Transmission
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Solution Overview
Problem
Current 5G NR systems face inefficiencies in small data transmission (SDT) from the RRC_INACTIVE state due to unnecessary power consumption, signaling overhead, and latency caused by frequent state transitions to RRC_CONNECTED, especially in scenarios without anchor relocation.
Innovation Solution
Storing UE-specific uplink and downlink SDT contexts at network nodes to facilitate efficient SDT without anchor relocation, including UE-specific RLC context and tunnel endpoint identifiers, allowing immediate RLC processing and data forwarding without repeated context fetch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE transitions to RRC_CONNECTED state for small data transmission, then data transmission capability is improved, but power consumption increases
Solution Approach 1:
The network node stores UE-specific SDT contexts (including RLC context, security context, and bearer context) in advance during the RRC_INACTIVE state, so that when small data transmission is needed, the UE can immediately use the pre-stored context without transitioning to RRC_CONNECTED, thereby avoiding the power consumption associated with state transition while maintaining data transmission capability
Solution Approach 2:
The patent creates and stores a copy of the UE's RLC context and other transmission parameters in the network node (gNB or CU-UP) during the inactive state. This copied context can be rapidly deployed for small data transmissions without requiring the full RRC connection establishment, enabling efficient data transfer with minimal power consumption
2Productivity
If the UE transitions to RRC_CONNECTED state for small data transmission, then data transmission capability is improved, but signaling overhead increases
Solution Approach 1:
The patent extracts only the essential RLC context and transmission parameters needed for small data transmission from the complete RRC connection setup and stores them separately in the network node. This extracted minimal context allows SDT to proceed with significantly reduced signaling overhead compared to full RRC connection establishment, while still maintaining the necessary data transmission capability
3Productivity
If the UE transitions to RRC_CONNECTED state for small data transmission, then data transmission capability is improved, but latency increases
Solution Approach 1:
The network node performs preliminary storage of UE-specific SDT contexts (RLC context, security context, bearer context) during the RRC_INACTIVE state. When small data transmission is initiated, the UE can immediately use these pre-stored contexts without undergoing the time-consuming RRC connection establishment process, thereby significantly reducing latency while maintaining full data transmission capability
Solution Approach 2:
The patent creates rapid-copy mechanisms for UE context information in the network node, allowing the stored RLC context to be instantly deployed for small data transmissions. This copying approach eliminates the need for time-consuming context retrieval and re-establishment, achieving low-latency transmission while preserving complete transmission capability
4Reliability
If RLC context is fetched repeatedly for each SDT procedure, then transmission reliability is improved, but backhaul signaling increases
Solution Approach 1:
The network node performs preliminary storage of the UE's RLC context and other transmission parameters in a readily accessible location (gNB or CU-UP) during the RRC_INACTIVE state. This pre-positioned context eliminates the need for repeated backhaul signaling to fetch RLC context for each SDT procedure, while ensuring transmission reliability by having the complete context locally available for immediate use
Solution Approach 2:
The network node configures itself to automatically store and maintain UE-specific SDT contexts locally without requiring external fetch operations. This self-service mechanism ensures that the RLC context is always available locally for SDT procedures, maintaining transmission reliability while eliminating the need for repeated backhaul signaling exchanges
Data Source
AI summary
Systems, methods, apparatuses, and computer program products for improved signaling of small data transmission (SDT) are provided. One method may include storing, at a first target network node, a user equipment (UE)-specific uplink (UL) small data transmission (SDT) context for a user equipment (UE) in a non-connected radio resource control (RRC) state that previously had initiated a small data transmission (SDT) procedure without anchor relocation via the first target network node or a second target network node. The method may also include performing radio link control (RLC) processing of the radio link control (RLC) protocol data units (PDUs) received from the user equipment (UE) using the stored user equipment (UE)-specific uplink (UL) small data transmission (SDT) context.