Hybrid Cellular WLAN Handover Virtual Window
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Solution Overview
Problem
Existing handover techniques for hybrid cellular/WLAN wireless communication devices face delays in making handover decisions due to averaging and hysteresis delays, which can lead to unnecessary handovers and service disruptions.
Innovation Solution
The implementation of a real-time virtual window (VW) that adjusts its size based on channel conditions, allowing instantaneous channel quality measurement estimation without accumulating samples, thereby eliminating averaging delay and introducing a gradient of the mean of the virtual window to enhance handover stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CQM samples are accumulated over a given time frame to accurately estimate current channel quality, then measurement precision is improved, but handover decision speed deteriorates due to averaging delay
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing channel quality measurements in a buffer before handover decisions are needed. The system continuously accumulates CQM samples in advance and maintains a running average, so when a handover decision is required, the estimation is already prepared and can be immediately used without waiting for the averaging process to complete. This eliminates the averaging delay while maintaining measurement precision.
2Stability of the object's composition
If hysteresis level is introduced to reduce unnecessary handovers and improve stability, then handover stability is improved, but handover decision speed deteriorates due to hysteresis delay
Solution Approach 1:
The patent applies dynamics by making the hysteresis parameter adaptive rather than fixed. The hysteresis level is dynamically adjusted based on current channel conditions, device mobility state, and historical handover patterns. When channel conditions are stable, a larger hysteresis margin is applied to prevent unnecessary handovers. When conditions change rapidly or device is mobile, the hysteresis is reduced to enable faster response. This dynamic adjustment maintains handover stability while minimizing hysteresis delay.
3Loss of time
If short signal averaging time is used to reduce averaging delay, then handover decision speed is improved, but measurement precision deteriorates leading to unnecessary handovers
Solution Approach 1:
The patent applies continuity of useful action by implementing continuous channel quality monitoring and averaging that operates without interruption. Instead of periodically sampling and then averaging, the system continuously accumulates CQM samples in a rolling buffer and maintains a continuous running average. This continuous process ensures that the measurement precision is maintained at all times while the averaging delay is eliminated because the average is always current and ready for immediate use in handover decisions.
4Measurement precision
If long signal averaging time is used to improve measurement precision, then channel quality estimation accuracy is improved, but handover decision speed deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-computing and continuously updating the channel quality average in advance, storing it in a readily accessible buffer. The system performs the computationally intensive averaging operation continuously in the background before it is needed, so when a handover decision is required, the precise average value is already prepared and can be immediately compared against handover thresholds. This eliminates the time penalty of long averaging while maintaining measurement precision.
Data Source
AI summary
Real-time handover decision techniques are provided which can utilize prior known system behavior in making a handover decision to avoid averaging delay and hysteresis delay.