Local Switch Handover in GSM Base Station Subsystems

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Solution Overview

Problem

In GSM systems, the existing handover process for local calls results in wastage of transmission resources and delays due to the need to release and re-establish the local switch, leading to potential speech loss during handover between Base Station Subsystems.

Innovation Solution

The method involves maintaining the local switch link and establishing a link with the Media Gateway for uplink speech data transmission during handover, allowing simultaneous transmission on both links after receiving a handover command from the Mobile Switching Center Server, and releasing resources only after successful handover completion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the local switch function is used for local calls within the same BSS, then transmission resource waste is avoided, but handover cannot be performed when one party needs to move to another BSS

Engineering Contradiction:

Improvetransmission resource wasteVSAvoidhandover capability

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent establishes the Media Gateway link in advance before handover is needed, while maintaining the local switch link. This preliminary preparation ensures that when handover becomes necessary, the path to the Media Gateway is already established, enabling seamless transition without service interruption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains both the local switch link and the Media Gateway link simultaneously during the handover preparation phase. This continuity ensures that the local switch function remains active for ongoing calls while the handover path is prepared, allowing uninterrupted service during the transition.

Inventive Principle:

Principle #20Continuity of useful action

2Adaptability or versatility

If the existing handover method is used (releasing local switch first), then handover can be performed, but speech loss occurs and handover time is delayed

Engineering Contradiction:

Improvehandover capabilityVSAvoidspeech continuity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The Media Gateway link is established in advance before the handover is executed. This preliminary action ensures that when the Mobile Station moves to a new BSC, the communication path through the Media Gateway is already in place, preventing speech loss and enabling immediate handover without waiting for link establishment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

By maintaining both the local switch link and the Media Gateway link simultaneously, the system creates a cushion or backup path before handover is needed. This dual-link approach ensures that if one path becomes unavailable, the other can immediately take over, preventing speech loss and ensuring continuous service.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Adaptability or versatility

If the local switch is released and re-established for handover, then handover can be completed, but handover time is deferred and complexity increases

Engineering Contradiction:

Improvehandover capabilityVSAvoidhandover time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The link between the BSC and Media Gateway is established in advance during the local call setup phase. This preliminary action eliminates the need to establish this link during handover, significantly reducing handover time and avoiding service interruption while maintaining the simplicity of the local switch function.

Inventive Principle:

Principle #10Preliminary action

4Reliability

If simultaneous transmission on both local switch link and Media Gateway link is performed, then speech loss is avoided during handover, but transmission resources are temporarily doubled

Engineering Contradiction:

Improvespeech continuityVSAvoidtransmission resource usage

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system dynamically manages the two links by maintaining both simultaneously during the handover preparation phase, then seamlessly switching from the local switch link to the Media Gateway link when handover is executed. This dynamic approach ensures continuous service while efficiently utilizing transmission resources, as the dual-link state is temporary and necessary only during the transition period.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP2536214B1Method, system and base station subsystem for realizing handover in local switch

Publication Date: 2019.06.26 ZTE CORP

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AI summary

The present invention provides a method for implementing a handover in a local switch, and the method comprises: when one party Mobile Station of a call implementing a local switch mode performs a Base Station Subsystem handover, the Base Station Subsystem handover transmits uplink speech data of the Mobile Station which does not need to perform the handover on a local switch link of the Base Station Subsystem and a link between the Base Station Subsystem and a Media Gateway simultaneously. A Base Station Subsystem implementing a handover in a local switch is also provided by the present invention. The present invention can efficiently avoid the speech loss of the Mobile Station performing the handover during the handover, and guarantees that the Mobile Station which needs to perform the handover can receive the speech data of the other party user no matter the Mobile Station is in the original BSS or the target BSS, thus maintaining the call between the two Mobile Stations efficiently.