Mobile Station RLF Detection and NAS Notification

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Solution Overview

Problem

Conventional mobile communication systems fail to detect the transition of a mobile station from an RRC_Connected state to an RRC_Idle state resulting from Radio Link Failure (RLF), leading to downlink data loss and prolonged radio link recovery times during re-connection processes.

Innovation Solution

Incorporating a monitor unit within the mobile station to detect RLF and notify the NAS function, which then initiates a location registration request with the mobile switching center, including an Active Flag for radio link recovery, and waits for a predetermined time before transmitting the request to avoid congestion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the mobile station waits for downlink data generation before notifying the network of RLF transition, then the network can detect the state transition, but downlink data is lost without reaching the mobile station

Engineering Contradiction:

Improvedownlink data delivery reliabilityVSAvoiddata loss period

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The mobile station performs location registration notification in advance before downlink data arrives, by detecting RLF transition from connected to idle state and proactively notifying the network. This preliminary action ensures the network knows the mobile station's state before data needs to be delivered, preventing data loss.

Inventive Principle:

Principle #10Preliminary action

2Speed

If the mobile station immediately transmits location registration request after detecting RLF, then re-connection is initiated quickly, but network congestion may occur due to simultaneous requests from multiple stations

Engineering Contradiction:

Improvere-connection speedVSAvoidnetwork congestion avoidance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The mobile station introduces a predetermined waiting period after detecting RLF before transmitting the location registration request. This periodic delay allows multiple mobile stations to stagger their re-connection attempts, preventing network congestion while still achieving relatively quick re-connection.

Inventive Principle:

Principle #19Periodic action

3Use of energy by moving object

If the mobile station remains in idle state after RLF without active re-connection, then energy consumption is reduced, but radio link recovery time is prolonged

Engineering Contradiction:

Improveenergy consumption in idle stateVSAvoidradio link recovery time

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The mobile station performs location registration notification proactively after detecting RLF transition, initiating the re-connection process before data loss occurs. This preliminary action reduces the overall recovery time while allowing the station to return to idle state afterward to conserve energy.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP2341745B1Mobile station

Publication Date: 2017.03.29 NTT DOCOMO INC

AI summary

In a mobile station (UE) according to the present invention, an AS function is configured to notify, when detecting a failure in a radio link established with the radio base station is detected or when discovering a cell subject to a location registration by a cell selection process, a NAS function of the detection or the discovery; and the NAS function is configured to transmit, in response to the notification, a location registration request signal to a mobile switching center (MME).