Hierarchical Inter-RAT Handover Decision Mechanism
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Solution Overview
Problem
Current mechanisms lack an efficient method for handover decision between heterogeneous access systems like SAE, I-WLAN, WiMAX, and UMTS, and RAN entities are incapable of making inter-RAT handover decisions due to the lack of target access system specific handover criteria and ranking information.
Innovation Solution
A hierarchical method for inter-RAT handover decision making, where the serving network entity, starting from the RAN entity, uses available target access system handover criteria and ranking information to assess measurement reports and decide on handovers, escalating decisions to core network entities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If RAN entities make handover decisions using conventional mechanisms, then intra-RAT handover can be performed, but inter-RAT handover decisions fail due to lack of target access system specific handover criteria and ranking information
Solution Approach 1:
The handover decision function is segmented between RAN entities and core network entities. RAN entities handle intra-RAT handovers using conventional mechanisms, while inter-RAT handover decisions are escalated to core network entities that possess target access system specific handover criteria and ranking information. This segmentation allows each entity to operate within its capability boundaries while achieving comprehensive handover support.
Solution Approach 2:
The core network entity acts as an intermediary with access to target access system specific handover criteria and ranking information. When a RAN entity encounters an inter-RAT handover scenario, it escalates the decision to the core network entity, which serves as a mediator with the necessary information to make informed inter-RAT handover decisions.
2Reliability
If handover decisions are escalated to core network entities, then inter-RAT handover reliability improves, but network complexity and decision-making time increase
Solution Approach 1:
The network entities are segmented into different functional levels: RAN entities for intra-RAT handovers and core network entities for inter-RAT handovers. This segmentation distributes complexity appropriately, with core network entities handling only the specific task of inter-RAT handover decisions where their additional complexity is justified by access to target access system specific criteria.
Solution Approach 2:
Core network entities perform partial handover decision functions by only handling inter-RAT handover scenarios rather than all handover types. This partial action approach allows core network entities to maintain specialized knowledge for inter-RAT decisions without the overhead of processing all handover types, reducing unnecessary complexity.
3Reliability
If hierarchical handover decision making is implemented, then handover failures are reduced, but information processing requirements and network signaling increase
Solution Approach 1:
Information processing is segmented between RAN entities and core network entities. RAN entities process measurement reports and generate handover requests for inter-RAT scenarios, while core network entities process the escalated decisions using target access system specific handover criteria and ranking information. This segmentation distributes information processing load according to each entity's capabilities and available information.
Solution Approach 2:
Core network entities pre-store target access system specific handover criteria and ranking information, performing preliminary preparation for inter-RAT handover decisions. This preliminary action allows them to quickly assess measurement reports and make informed decisions without extensive real-time information processing, reducing the information processing load during actual handover events.
Data Source
AI summary
The invention relates to the field of mobile communication systems. In particular, the invention discloses a method for handover decision making during an inter-radio access technology (RAT) handover. According to the method, the decision for inter-RAT handover may be taken by the serving network entity in a hierarchical manner beginning with a radio access network (RAN) entity and proceeding towards a core network (CN) entity. Further, the serving network entity may take the decision for the inter-RAT handover based on the information and knowledge of the target access system handover criteria and the ranking available in the network entity.