Service-Based Inter-RAT Handover for Wireless Networks
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Solution Overview
Problem
There is a need for a method to seamlessly hand over calls between different radio access technologies (RATs) in wireless communication systems, such as TD-SCDMA, WCDMA, and GSM, to ensure uninterrupted service as user equipment (UE) moves across varying network coverage areas, particularly during migration from 2G to 3G technologies.
Innovation Solution
The method involves determining the quality of signals from multiple target RATs while a UE is in a call with a source RAT and transmitting an indication of this quality, then handing over the call to one of the target RATs based on the service type of the call, such as circuit-switched or packet-switched services, to select the most suitable network for continued communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE hands over calls between different RATs during network migration, then service continuity is maintained, but handover complexity and decision-making difficulty increase
Solution Approach 1:
The UE autonomously determines signal quality of target RATs and autonomously selects the appropriate target RAT for handover based on pre-configured service type mappings, without requiring complex network-side handover decision mechanisms. This self-service approach maintains service continuity while reducing handover decision complexity.
Solution Approach 2:
The network pre-configures the UE with service type to RAT mapping information before handover occurs. This preliminary configuration enables the UE to quickly determine the appropriate target RAT during handover by simply matching the current service type against the pre-configured mappings, avoiding complex real-time decision-making while ensuring service continuity.
2Adaptability or versatility
If the UE monitors multiple target RATs simultaneously, then handover options increase, but signal quality measurement complexity increases
Solution Approach 1:
The UE focuses signal quality measurements only on RATs that are locally relevant to the current service type, as indicated by pre-configured mappings. Instead of uniformly measuring all possible target RATs, the UE selectively measures only those RATs that are appropriate for the current service, reducing measurement complexity while maintaining versatile handover options through the pre-configured service-RAT mappings.
3Ease of operation
If handover decisions are based on service type classification, then appropriate network selection is improved, but call interruption risk increases during the transition
Solution Approach 1:
The network provides feedback to the UE in the form of pre-configured service type to RAT mappings, enabling accurate network selection based on service type. This feedback mechanism ensures that the UE selects the most appropriate target RAT for the current service, improving network selection accuracy while maintaining call continuity through informed decision-making.
Data Source
AI summary
In geographical areas with incomplete Time Division Synchronous Code Division Multiple Access (TD-SCDMA) coverage, it may be beneficial for a multimode User Equipment (UE) to handover to a GSM network, a WCDMA network, a CDMA 1x RTT network, or an LTE network. When multiple networks are available to the UE and a poor signal quality is detected in the TD-SCDMA network, one of the available networks may be selected for inter-RAT handover based on a service type of the active call on the UE. For example, when a circuit-switched call, such as a voice call, is in progress on the UE, an inter-RAT handover to a GSM network occurs. In another example, when a packet-switched call, such as a data call, is in progress on the UE, an inter-RAT handover to a WCDMA network occurs. Selecting a network for inter-RAT handover based on an active call service type improves the service provided to the UE.