Inter-RAT Handoff Coordination via Priority Arbitration
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Solution Overview
Problem
In wireless communications systems, multi-mode user terminals experience conflicts between carrier selection priorities set by the mobile terminal's MMSS and those broadcast by the Access Network, leading to ping-ponging between different RAT carriers and operators, and increased power consumption and delay during cross-operator roaming.
Innovation Solution
Access Networks broadcast neighbor lists with prioritization rules that ensure consistency with the home network's policy, giving precedence to home network carriers and only allowing reselection to non-home network carriers when all home network RATs are unavailable, using PLMN_IDs to identify operators and setting thresholds for link quality measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multi-mode terminals use MMSS with operator-provisioned carrier priorities, then the terminal can select authorized or preferred systems when powering up or roaming, but conflicts arise with AN-broadcast priorities causing ping-ponging between carriers
Solution Approach 1:
The patent segments the priority information into two distinct sources: MMSS priorities provisioned by the home operator and AN-broadcast priorities from the serving access network. By separating these priority mechanisms and establishing a clear precedence rule (AN-broadcast priorities take precedence), the system resolves the conflict that causes ping-ponging while preserving both selection capabilities and connection stability.
2Productivity
If ANs broadcast neighbor lists with carrier priorities, then inter-RAT reselection can be directed, but conflicts with MMSS priorities cause terminals to ping-pong between carriers of different RATs and operators
Solution Approach 1:
The patent introduces a priority arbitration mechanism as an intermediary between MMSS and AN-broadcast priority systems. When both mechanisms provide carrier priorities, the system uses a predefined resolution rule (AN-broadcast priorities take precedence) to arbitrate the conflict, enabling efficient directed handoffs while preventing unstable ping-ponging behavior.
3Adaptability or versatility
If terminals perform cross-operator roaming handoff, then access to different operator networks is enabled, but large power consumption and delay are experienced
Solution Approach 1:
The patent applies preliminary action by having the home operator provision MMSS priority information in advance during terminal setup. This pre-configured priority data enables the terminal to make informed carrier selection decisions during roaming without needing to perform extensive real-time searches, thereby reducing both power consumption and handoff delay while maintaining roaming capability.
Data Source
AI summary
A method is provided whereby wireless system operators broadcast each other's carriers in an inter-RAT neighbor list according to protocols that minimize conflicts with carrier-selection algorithms provisioned in served mobile terminals. According to the method of the invention, Access Networks (ANs) broadcast neighbor lists for their own carriers and carriers of different operators serving the same geographical area, the neighbor list being used for inter RAT reselection. The carrier-selection priorities broadcast in the neighbor list are established to be consistent with the priority policy respecting home network and non-home networks as provisioned in the mobiles by their operator. In case of conflict, the cross-RAT priority broadcast by the AN shall take precedence over the cross-RAT priority provisioned in the mobiles. A network ID, such as PLMN_ID, may be broadcast for each carrier in the neighbor list to support reselection precedence followed by the mobile terminal between home network carriers and the carriers of a non-home network.