Handover Coordination in Mobile Networks

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Solution Overview

Problem

The IEEE 802.16Rev2 specification does not allow for exclusive use of BS-initiated handover, leading to system instability due to the precedence of MS-initiated handover, which can result in inefficient resource management and network instability.

Innovation Solution

A method to coordinate MS-initiated and BS-initiated handover processes, enabling 'BS-controlled MS-initiated handover' by ensuring mandatory notification through MOB_MSHO-REQ or MOB_BSHO-REQ messages and restricting MS handover decisions to trigger conditions, thereby synchronizing handover decisions between the Mobile Station and Base Station.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If BS-initiated handover is enabled in the system, then network resource management capability is improved, but system stability deteriorates due to MS-initiated handover precedence

Engineering Contradiction:

Improvehandover control capabilityVSAvoidsystem stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system performs preliminary configuration by setting a handover coordination parameter at the base station before handover occurs. This parameter pre-establishes whether MS-initiated handover should be allowed or restricted, preventing conflicts before they arise. The base station configures this parameter based on network conditions and handover policies, ensuring stable operation while maintaining BS-initiated handover capability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention inverts the traditional handover precedence rule by making BS-initiated handover the default controlling mechanism rather than MS-initiated handover. When the handover coordination parameter indicates BS control, the base station's handover decisions take precedence over mobile station decisions, reversing the conventional approach and enabling stable BS-controlled handover operation.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If MS-initiated handover always takes precedence, then individual link optimisation is achieved, but network resource management efficiency deteriorates

Engineering Contradiction:

Improvechannel quality assessmentVSAvoidresource management efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The system applies different handover control strategies to different scenarios by using the handover coordination parameter to distinguish between MS-controlled and BS-controlled modes. In BS-controlled mode, the base station can override MS decisions to optimize network-wide resource allocation, while still allowing MS to provide accurate channel quality measurements for informed decision-making.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the operational parameter of handover control mode dynamically. The base station configures the handover coordination parameter to switch between allowing MS-initiated handover and restricting it to BS-controlled handover, enabling flexible adaptation between link optimization and resource management efficiency based on network conditions.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If both MS-initiated and BS-initiated handover are supported simultaneously, then handover flexibility is improved, but coordination complexity increases

Engineering Contradiction:

Improvehandover mechanism flexibilityVSAvoidhandover coordination complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The invention extracts the coordination complexity from the handover execution process and concentrates it in the base station's parameter configuration. By setting the handover coordination parameter centrally at the base station, the system eliminates the need for complex real-time coordination protocols between MS and BS, simplifying the overall system while maintaining both handover modes.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8355383B2Method, system and devices for supporting handover in mobile communication networks

Publication Date: 2013.01.15 NOKIA SOLUTIONS & NETWORKS OY

AI summary

Handover of a mobile station (MS) from a serving base station (BS) to a target base station in a mobile communication system supporting both MS-initiated handover and BS-initiated handover, is coordinated by ensuring that, both in the case of BS-initiated handover and in the case of MS-initiated handover: the mobile station (MS) and the base station (BS) share information, either via a MO_BSHO-REQ message sent from the BS to the MS in the case of BS-initiated HO or via a MO_MSHO-RETQ message sent from the MS to the BS in the case of MS-initiated HO, indicating a target base station for the mobile station (MS) to attempt handover; and the mobile station (MS) sends an information message (M0B_H0-IND) indicating the base station to which handover was attempted.