Mobile Station Registration Timer Adjustment for Ping-Pong Handover Reduction
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Solution Overview
Problem
The integration of unlicensed radio access networks with conventional cellular networks leads to a higher probability of 'ping-pong' effects due to frequent handovers and lacks effective control over mobile station context history, resulting in increased signaling and processing loads.
Innovation Solution
The access network controller maintains a mobile context alive with a context keep-alive timer after de-registration and adjusts the access network reselection timer upon re-registration, allowing it to manage and reduce undesirable handover frequencies by setting a new timer value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed access network reselection timer is used in the mobile station, then the implementation is simple, but it cannot adapt to varying handover frequencies and fails to reduce ping-pong effects effectively
Solution Approach 1:
The access network reselection timer value is changed from a fixed predefined value to a dynamically adjustable parameter. The network controller can modify the timer value based on observed handover patterns and mobile station behavior, allowing the system to adapt to varying conditions and reduce ping-pong effects while maintaining operational flexibility.
Solution Approach 2:
The system implements a feedback mechanism where the network controller monitors handover frequency and mobile station registration patterns, then adjusts the access network reselection timer accordingly. This closed-loop control allows the network to respond to actual handover behavior and optimize the timer value to prevent excessive handovers.
2Quantity of substance
If the mobile context is erased upon de-registration, then the network controller memory is freed, but the network loses the ability to detect and respond to high frequency handovers
Solution Approach 1:
The network controller performs preliminary actions by maintaining the mobile context in memory for a predetermined period after de-registration. This allows the controller to accumulate sufficient data about handover patterns before erasing the context, enabling detection of high-frequency handover scenarios that would otherwise be invisible to the network.
Solution Approach 2:
Instead of immediately erasing the mobile context upon de-registration, the system retains it partially longer than the minimum required time. This extended retention period provides the network with sufficient information to detect and respond to abnormal handover patterns, with the context being erased only after the observation period expires.
3Productivity
If hysteresis is added to handover algorithms to limit signaling load, then frequent handovers are reduced, but the solution is ineffective in unlicensed radio access networks with small cell sizes
Solution Approach 1:
The access network reselection timer acts as an intermediary control mechanism between the mobile station's handover decisions and the network's signaling load. By adjusting this timer, the network can indirectly influence handover frequency without modifying the fundamental handover algorithm or requiring complex hysteresis calculations, providing a simpler and more effective control method for small cell networks.
Data Source
AI summary
The current invention relates to the registration of mobile stations in a mobile communications network. It has particular relevance to handovers and roaming between base stations of an unlicensed radio access network (110) and those of a conventional cellular network (120). As the cells in an unlicensed radio access network have a rather small size, it means that handover potentially can occur far more frequently than for a conventional cellular network. This can result in an undesired ‘ping-pong’ effect, i.e. that the mobile station is switching back and forth between two radio cells too frequently. The current invention reduces this effect by preventing the mobile station to register to the unlicensed radio access network during a modifiable period of time (306).