SGW ISR Handling for Downlink Data Delivery

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Solution Overview

Problem

In mobile communication systems, when a UE moves out of its registered area, downlink data packets are often lost due to the old MME sending paging messages to the wrong location, as it is unaware of the UE's new registration area.

Innovation Solution

The Serving Gateway (SGW) suspends downlink data processing until it receives a notification of the UE's new location registration, ensuring that data packets are delivered once the UE is fully registered with the new MME, thereby preventing packet loss during movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the SGW sends downlink data notification message to the old MME during UE movement, then the old MME can process the notification, but the UE cannot be paged because it has moved to a new area managed by a new MME

Engineering Contradiction:

Improvedownlink data delivery speedVSAvoiddownlink data packet reception reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The SGW waits for the new MME to complete location registration before sending the downlink data notification message. This preliminary action ensures that the UE is properly registered in the new area and can receive paging messages, preventing packet loss during movement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The SGW monitors the location registration status between the UE and the new MME. By implementing feedback mechanism, the SGW can determine the appropriate timing for sending the downlink data notification message, ensuring that the UE is ready to receive data in its new location.

Inventive Principle:

Principle #23Feedback

2Reliability

If the SGW waits for new MME location registration completion before sending downlink data notification, then packet loss is prevented, but data delivery is delayed

Engineering Contradiction:

Improvedownlink data packet reception reliabilityVSAvoiddata delivery time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The SGW performs a preliminary check to see if location registration is already in progress or completed before waiting. If registration is already complete or imminent, the SGW can proceed more quickly, reducing unnecessary delays while still ensuring reliability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The SGW dynamically adjusts its waiting behavior based on the actual state of location registration. Rather than using a fixed waiting period, the system adapts the timing based on real-time registration status, optimizing both reliability and speed.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP3240329B1Method in a serving gateway, SGW, involving change of MME when ISR is used

Publication Date: 2023.03.29 NEC CORP

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AI summary

The mobile communication system according to an exemplary embodiment of the present invention includes UE (45), MME (25), SGSN (27) and SGW (15). The SGW (15) includes means for, when ISR is active in the UE (45), the MME (25), the SGSN (27) and the SGW (15), sending a Downlink Data Notification message to the MME (25) and the SGSN (27), and when a Modify Bearer Request message is received from another MME (35) or another SGSN (37) different from the MME (25) and the SGSN (27), resending the Downlink Data Notification message only to another MME (35) or another SGSN (37) having sent the Modify Bearer Request message.