Wireless Network Handover Control to Prevent Ping-Pong Mobility
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Solution Overview
Problem
In high-speed environments, such as high-speed trains or highways, user equipment frequently experiences rapid cell changes, leading to high network processing loads and potential service disruptions due to 'ping pong' handovers back to weaker cells, which can overwhelm network resources and cause connection drops.
Innovation Solution
Implementing a prohibit time period after handover during which handovers back to a weaker source cell are inhibited, using signal strength differences and UE speed to determine this period, allowing the UE to move out of the source cell's coverage before attempting another handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover is triggered early when target cell signal strength is lower than source cell, then service continuity is improved by allowing more time for handover completion, but ping pong handover risk increases causing network load and connection stability to deteriorate
Solution Approach 1:
The patent applies preliminary anti-action by introducing a prohibit time mechanism that proactively prevents handover back to the source cell before the ping pong condition can occur. When handover is triggered early (when target cell signal is lower than source cell by a negative offset), the system preemptively suspends handover back to source for a calculated prohibit time period, thereby counteracting the potential harmful ping pong effect before it manifests.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the handover triggering parameters (negative offset values) and introducing a time-based parameter (prohibit time) that modifies the handover decision criteria. The prohibit time is calculated based on UE speed and signal strength differences, thereby adapting the handover parameters to current network conditions to prevent ping pong while maintaining service continuity.
2Loss of time
If handover is triggered when target cell signal strength is greater than source cell by negative offset, then handover completion time is improved, but handover back to source cell is more likely increasing network signalling load
Solution Approach 1:
The prohibit time mechanism serves as a preliminary anti-action that anticipates and prevents the harmful effect of excessive handover signalling. By suspending handover back to source cell during the prohibit period, the system reduces the quantity of handover signalling messages that would otherwise be exchanged, thereby addressing the contradiction between fast handover completion and reduced network signalling load.
3Measurement precision
If prohibit time is calculated based on UE speed and signal strength difference, then accuracy of preventing ping pong is improved, but complexity of handover control increases
Solution Approach 1:
The patent applies parameter changes by using measurable physical parameters (UE speed and signal strength difference) to calculate the prohibit time duration. This approach improves the precision of ping pong prevention by adapting the prohibit time to actual propagation conditions, while the calculation complexity is managed by using straightforward mathematical relationships between these parameters.
Data Source
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AI summary
A wireless communication network that supports mobility of a user equipment from a source cell to a target cell. The network providing the target cell is configured to receive handover preparation information for a handover from the source cell to the target cell and where the handover preparation information indicates that the target cell has a lower signal strength than the source cell, the target cell generates an indication of a prohibit time, the prohibit time being a time period following handover during which a user equipment should be impeded from a handover back to said source cell.