RRC Inactive UE Downlink Scheduling for Low-Latency Small Data

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Solution Overview

Problem

The existing procedures for Mobile Terminated (MT) Small Data Transmission (SDT) in wireless communications networks result in sub-optimal signaling and increased latency when using Configured Grant (CG)-SDT, as they are designed for Mobile Originated (MO) transmissions, leading to unnecessary signaling overhead.

Innovation Solution

Implementing a method where the UE and network node derive new security keys based on shared context keys to encrypt and decrypt data using Cell-Radio Network Temporary Identifiers (C-RNTI) for CG-SDT, allowing direct DL data transmission without initiating the CG-SDT procedure, thus optimizing signaling and reducing latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If existing MT-SDT procedures are implemented, then data transmission is possible, but signaling overhead increases and latency increases

Engineering Contradiction:

Improvesignaling overheadVSAvoidlatency

Core Design Contradiction:

Loss of informationVSLoss of time

Solution Approach 1:

The patent extracts and removes the unnecessary CG-SDT procedure initiation steps from the MT-SDT process. By recognizing that the network can directly schedule DL data transmission without requiring the UE to initiate CG-SDT, the solution eliminates redundant signaling messages while maintaining the essential data transmission functionality.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies preliminary action by pre-configuring the UE with CG-SDT resources and C-RNTI during the RRC inactive state, before actual data transmission is needed. This pre-configuration allows the network to immediately schedule DL data without requiring procedure initiation signaling at the time of data arrival, thus reducing latency and signaling overhead.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If CG-SDT procedure is initiated for MT-SDT, then data transmission can occur, but device complexity and procedure steps increase

Engineering Contradiction:

Improveprocedure simplicityVSAvoidprocedure steps

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent inverts the traditional approach by allowing the network to initiate DL data transmission directly to the UE in RRC inactive state, rather than requiring the UE to initiate the CG-SDT procedure first. This reversal simplifies the overall procedure by eliminating multiple initiation steps and reducing the complexity of the interaction sequence between network and UE.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS12568361B2User equipment, network node and methods in a wireless communications network

Publication Date: 2026.03.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method for handling a Mobile Terminating (MT) Small Data Transmission (SDT) from a network node to a user equipment (UE) in a wireless communications network. The UE receives a Downlink Control Information (DCI) from the network node. The DCI is identified when monitoring a Physical Downlink Control Channel (PDCCH) by means of a Cell-Radio Network Temporary Identifier (C-RNTI). The DCI indicates scheduled Downlink (DL) data related to the SDT. Further, the DCI is received when the UE has entered into an inactive mode. When the DCI has been received, the UE resumes the radio resources configured for a Configured Grant based SDT (CG-SDT) in the UE context, derives a new security key based on a security key present in the UE context, and when receiving the scheduled DL data related to the MT-SDT from the network node, the UE decrypts the DL data by means of the new security key.