Handover Probability Mechanism for SRVCC Call Reliability
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Solution Overview
Problem
SRVCC handover failures occur frequently, especially at cell edges where LTE and legacy network coverage is insufficient, leading to call failures and decreased audio quality, resulting in an unsatisfactory user experience.
Innovation Solution
An enhanced handover mechanism using Interworking Wireless Local Area Network (iWLAN) handovers, where user equipment (UE) receives historical data to determine the probability of failed handovers and initiates a call handover to WiFi when the probability exceeds a threshold, avoiding less reliable legacy radio access technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SRVCC handover is used to handover from LTE to legacy network, then voice call continuity is maintained, but handover failures occur frequently at cell edges leading to call failures and decreased audio quality
Solution Approach 1:
The patent introduces an intermediary mechanism (handover probability determination based on historical data and location data) between the handover decision and execution. The UE determines the probability of handover failure using historical handover data and current location information, then compares this probability against a threshold to decide whether to proceed with SRVCC handover or initiate alternative actions (such as maintaining LTE connection or switching to WiFi). This intermediary probability assessment mechanism prevents unreliable handovers from being executed, thereby reducing call failures and audio quality degradation while maintaining voice call continuity when handover is reliable.
2Duration of action of moving object
If SRVCC handover is initiated in areas with poor LTE coverage, then call continuity is attempted, but handover failures increase and user experience deteriorates
Solution Approach 1:
The patent applies preliminary action by having the UE proactively determine the handover failure probability using historical data and current location data before actually initiating the SRVCC handover process. The UE accesses historical handover data stored in its memory and current location data, calculates the probability of handover failure, and compares it against a threshold. If the probability exceeds the threshold (indicating high risk of failure), the UE prevents the handover from occurring or takes alternative actions. This preliminary probability assessment prevents unreliable handovers in poor coverage areas, maintaining call continuity only when handover is likely to succeed.
3Reliability
If historical data is collected and processed to determine handover probability, then handover reliability is improved, but device complexity and processing requirements increase
Solution Approach 1:
The patent implements self-service by having the UE autonomously collect, store, and process its own historical handover data without requiring external network assistance for data collection. The UE maintains local memory for storing historical handover data and independently accesses this data along with current location data to determine handover probability. The device serves itself by managing its own handover decision-making process using its own accumulated experience (historical data), reducing the need for complex network-side processing and external data sources.
Solution Approach 2:
The patent uses copying by storing historical handover data locally in the UE's memory. Instead of repeatedly querying the network for handover statistics or real-time network conditions, the UE creates a local copy of historical handover data and uses this copied information for probability determination. This local copying mechanism reduces processing complexity compared to real-time network analysis while still providing reliable handover decisions based on accumulated historical experience.
Data Source
AI summary
A user equipment (UE), base station and a corresponding method for receiving historical data from a diagnostic server, receiving location data of the UE, determining a probability of a failed handover during a call based on the historical data and the location data, comparing the probability of the failed handover to a threshold value and initiating a call handover to a wireless local area network when the probability of the failed handover exceeds the threshold value. Also, a UE, base station and corresponding method for determining if one or more UEs have an active voice over WiFi call or if the UEs are registered with a Internet protocol ("IP") multimedia subsystem ("IMS") over WiFi and biasing a cell reselection procedure of the UE to select a cell of a packet switched network such as LTE.