Back-off Timer for Radio Access Technology Selection
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Solution Overview
Problem
Cellular phones experience significant battery degradation due to repetitive scanning for alternate radio access technologies when signal strength is moderately weak, leading to inefficient power consumption.
Innovation Solution
Implementing a back-off timer mechanism that decays at a increasing rate if the alternate radio access technology signal is not strong enough to warrant a switch, and using a motion sensor to suspend or adjust the timer based on device stationarity, allowing the device to reassess signal strength periodically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cellular phone continuously scans for an alternate radio access technology when the current signal is moderately weak, then the phone can switch to a stronger signal when available, but the repetitive scanning causes significant power consumption and battery degradation
Solution Approach 1:
The patent implements periodic scanning with exponentially increasing intervals (1 second, 2 seconds, 4 seconds, 8 seconds, etc.) instead of continuous scanning. The back-off timer controls this periodic behavior, allowing the phone to scan at regular intervals that grow progressively longer, thereby reducing power consumption while maintaining the ability to detect and switch to better signals when they become available.
2Use of energy by moving object
If the cellular phone uses a back-off timer with exponentially increasing intervals to reduce scanning frequency, then power consumption is reduced, but the response time to detect improved signals is increased
Solution Approach 1:
The back-off timer intervals are dynamic rather than fixed. The scanning interval starts at 1 second and exponentially increases (2 seconds, 4 seconds, 8 seconds, etc.) based on how long the phone has been using the current signal. This dynamic adjustment allows frequent initial scanning to quickly detect signal improvements, then gradually reduces scanning frequency to save power as the connection stabilizes.
Data Source
AI summary
Methods and apparatus for selecting an inter-radio access technology for an electronic device are disclosed. In an embodiment, a wireless electronic device determines if a first radio signal strength (e.g., LTE) is weak enough that the device should start scanning for another radio access technology (e.g., CDMA). If the first radio signal strength (e.g., LTE) is very weak (e.g., even weaker than the level that caused the device to start scanning), and a second radio signal strength (e.g., CDMA) is above a second threshold, then the device selects the second radio access technology (e.g., switches from LTE to CDMA). If (a) the first radio signal strength (e.g., LTE) is not weak enough to warrant a move to another radio access technology, (b) the second radio signal strength (e.g., CDMA) is not above the second threshold (e.g., not strong enough to warrant a move), and/or (c) a motion sensor determines that the device is relatively stationary (e.g., signal strengths are unlikely to change), then the device sets a back-off timer (e.g., set to expire in one second before trying again, and then two seconds before trying again, then three seconds etc).