NAS Message Buffering During Handover in Evolved Networks

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Solution Overview

Problem

In evolved networks, if a handover fails during NAS message processing, the EPC cannot timely inform the UE, leading to incorrect NAS message delivery, as existing solutions do not provide a method for sending NAS messages when the UE returns to the S-eNB service area.

Innovation Solution

The method involves sending a direct-transfer message to the S-eNB containing the NAS message, buffering it when handover fails, and using a retransmission timer to ensure the NAS message is sent correctly through the S-eNB or T-eNB based on handover success or failure, with an MME and eNodeB configured to manage these processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the EPC sends NAS messages during handover without buffering, then message delivery speed is improved, but message delivery correctness deteriorates when handover fails

Engineering Contradiction:

ImproveNAS message delivery speedVSAvoidNAS message delivery correctness

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The EPC buffers NAS messages before handover completion, preparing them in advance for potential retransmission. This cushioning mechanism ensures that if handover fails, the messages are already prepared and can be quickly retransmitted without loss, thus maintaining both speed and reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The system implements feedback through handover status reporting from eNodeB to EPC. When handover fails, the eNodeB reports the failure status, triggering the EPC to retransmit buffered NAS messages. This feedback loop ensures correct message delivery while maintaining efficient communication.

Inventive Principle:

Principle #23Feedback

2Reliability

If the EPC buffers all NAS messages during handover, then message delivery correctness is improved, but storage space requirements increase

Engineering Contradiction:

ImproveNAS message delivery correctnessVSAvoidEPC storage space

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The EPC buffers only the necessary NAS messages during handover rather than all messages. This partial buffering approach provides sufficient reliability for handover-critical messages while avoiding excessive storage space consumption for non-critical messages that don't require handover buffering.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If the EPC retransmits NAS messages after handover failure, then message delivery correctness is improved, but communication delay increases

Engineering Contradiction:

ImproveNAS message delivery correctnessVSAvoidNAS message delivery delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The EPC performs preliminary buffering of NAS messages before handover completion. This preliminary action ensures that messages are ready for immediate retransmission if handover fails, minimizing the time loss compared to generating and sending messages after detecting handover failure.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11399323B2Method and apparatus for non-access stratum message processing during handover in evolved network

Publication Date: 2022.07.26 HUAWEI TECH CO LTD

AI summary

A method and an apparatus for non-access stratum (NAS) message processing during handover are provided. The method includes the steps of sending a first message to a radio access network node, wherein the first message including a non-access stratum (NAS) message, and receiving a second message from the radio access network node, wherein the second message comprising the NAS message and cause information indicating a handover is triggered.