DL SPS Handling in MT-SDT for RRC_INACTIVE UEs
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Solution Overview
Problem
Existing wireless communication systems face inefficiencies in managing small data transmissions in the RRC_INACTIVE state, leading to unnecessary power consumption and signaling overhead due to frequent transitions between RRC_INACTIVE and RRC_CONNECTED states for both mobile originated (MO) and mobile terminated (MT) data, particularly in 5G networks.
Innovation Solution
Implementing Downlink Semi-Persistent Scheduling (DL SPS) during Mobile Terminated Small Data Transmission (MT-SDT) procedures, allowing UEs to manage configured DL assignments in RRC_INACTIVE state, and transitioning to RRC_CONNECTED state only when necessary, thereby optimizing data handling and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE transitions to RRC_CONNECTED state for every small data transmission in RRC_INACTIVE state, then the data transmission can be completed reliably, but the power consumption increases and signaling overhead increases
Solution Approach 1:
The patent segments the data transmission process by introducing two distinct modes: MO-SDT (Mobile Originated Small Data Transmission) for uplink data and MT-SDT (Mobile Terminated Small Data Transmission) for downlink data. This segmentation allows the UE to handle different transmission directions using optimized procedures specific to each case, avoiding unnecessary full RRC_CONNECTED transitions for small data packets while maintaining reliable transmission through dedicated SDT mechanisms.
Solution Approach 2:
The patent implements dynamic state management where the UE can flexibly transition between RRC_INACTIVE and RRC_CONNECTED states based on actual data transmission needs. The network can dynamically configure SDT parameters and trigger SDT procedures when small data needs to be transmitted, allowing the system to adapt to varying traffic patterns and minimize unnecessary state transitions, thereby reducing power consumption while maintaining transmission reliability.
2Reliability
If the UE transitions to RRC_CONNECTED state for every small data transmission in RRC_INACTIVE state, then the data transmission can be completed reliably, but the signaling overhead increases
Solution Approach 1:
The patent extracts the essential data transmission functionality from the full RRC connection establishment procedure by creating a simplified SDT (Small Data Transmission) mechanism. This extracted mechanism retains only the necessary elements for small data transmission (such as configured grants for uplink and dedicated PDSCH for downlink) while removing unnecessary signaling steps, thereby reducing signaling overhead while maintaining transmission reliability through the preserved essential functions.
Solution Approach 2:
The patent employs preliminary configuration where the network pre-configures SDT parameters (such as configured grants, PDSCH resources, and SPS configurations) while the UE is in RRC_INACTIVE state. This preliminary action prepares all necessary transmission resources in advance, so when small data needs to be transmitted, the UE can immediately use the pre-configured resources without going through the full connection establishment process, thus reducing signaling overhead while ensuring reliable transmission.
3Reliability
If the UE maintains DL SPS configuration during MT-SDT procedure and transitions to RRC_CONNECTED, then downlink data reception is ensured, but the device complexity increases
Solution Approach 1:
The patent makes the DL SPS (Downlink Semi-Persistent Scheduling) configuration universal by designing it to function effectively in both RRC_INACTIVE and RRC_CONNECTED states. The same SPS configuration can be used for MT-SDT procedures in inactive state and for regular downlink data reception in connected state, eliminating the need for separate configuration mechanisms and reducing overall device complexity while ensuring reliable downlink data reception across different states.
Solution Approach 2:
The patent introduces the RRC_INACTIVE state as an intermediary state between RRC_IDLE and RRC_CONNECTED, which supports limited data transmission functions. This intermediary state allows the UE to maintain essential configurations (like DL SPS) without the full overhead of RRC_CONNECTED, serving as a bridge that reduces complexity compared to always being connected while ensuring reliable downlink reception through maintained SPS configurations.
4Ease of operation
If the UE releases DL SPS configuration upon receiving RRC resume message, then the configuration management is simplified, but the productivity decreases
Solution Approach 1:
The patent ensures continuity of DL SPS configuration across state transitions by maintaining the configuration when transitioning from RRC_INACTIVE to RRC_CONNECTED state during MT-SDT procedures. This continuity allows the UE to seamlessly continue receiving downlink data using the same SPS resources without reconfiguration delays, thereby maintaining high data transmission efficiency while keeping configuration management relatively simple through consistent configuration persistence.
Data Source
AI summary
Methods, systems, and apparatuses are provided for mobile terminated small data transmission in a wireless communication system. A User Equipment (UE) can apply Downlink (DL) Semi Persistent Scheduling (SPS) in a Mobile Terminated Small Data Transmission (MT-SDT) procedure. The UE can handle the configured DL assignment for DL SPS. A method for a UE in a wireless communication system can comprise receiving one or more configurations of DL SPS for Radio Resource Control Inactive (RRC_INACTIVE) state, initiating a MT-SDT procedure in response to receiving a paging indicating MT-SDT, receiving, in RRC_INACTIVE state, one or more DL transmissions using a configured DL assignment for the DL SPS during the MT-SDT procedure, and keeping the one or more configurations of the DL SPS and entering RRC_CONNECTED state in response to receiving a RRC resume message during the MT-SDT procedure.