Frequency Swept RSSI Headset Proximity Detection
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Solution Overview
Problem
Existing methods for determining the proximity of a headset to its base station using received signal strength indication (RSSI) are inaccurate due to multi-path fading and polarization issues, leading to unreliable NEAR/FAR state detection.
Innovation Solution
The method involves measuring RSSI across a frequency band, either naturally or forcibly, and processing the peak RSSI values to determine the NEAR/FAR status by correlating the RSSI envelope and using autocorrelation of the signal over time, with hysteresis applied to stabilize state transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RSSI is measured at a single frequency, then measurement simplicity is maintained, but measurement precision deteriorates due to multi-path fading and polarization issues
Solution Approach 1:
The frequency band is segmented into multiple discrete frequency points for RSSI measurement. Instead of measuring at a single frequency, the system measures RSSI at multiple frequencies (e.g., 5-10 frequencies spaced across the band) and processes these segmented measurements to determine proximity, thereby avoiding the fading issues at any single frequency while maintaining manageable complexity through systematic processing of the segmented data.
2Reliability
If frequency swept RSSI measurement is implemented, then reliability of proximity detection is improved, but loss of time increases due to multiple frequency measurements
Solution Approach 1:
The system performs RSSI measurements at multiple frequencies in a periodic sequence rather than continuously at all frequencies simultaneously. By cycling through the frequency points in a structured periodic manner and using the temporal pattern of measurements, the system achieves reliable proximity detection while minimizing the total time required compared to exhaustive simultaneous multi-frequency measurement.
Solution Approach 2:
The system performs preliminary RSSI measurements at multiple frequencies to establish a baseline frequency response profile before making the final proximity determination. This preliminary action at selected frequency points allows the system to account for multi-path effects and polarization variations in advance, enabling faster and more reliable final assessment without requiring exhaustive continuous measurement at all frequencies.
3Measurement precision
If peak RSSI values are used for proximity determination, then measurement precision is improved, but device complexity increases due to signal processing requirements
Solution Approach 1:
The system replaces complex mechanical or hardware-based signal processing with software-based autocorrelation algorithms. Instead of using hardware filters or analog processing to extract proximity information from multi-frequency RSSI measurements, the invention uses digital signal processing techniques (autocorrelation of the RSSI envelope) that can be implemented in software, thereby achieving precise proximity measurement while keeping the physical device complexity manageable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases the reliability of NEAR/FAR presence detection by mitigating the effects of multi-path fading and polarization variations, providing more accurate proximity assessments.
Implementation Method 1
Received signal strength depends on transmit power level, the direct line of sight distance between transmitter and receiver and any reflected radio waves received (multi-path)
Implementation Method 2
deep fades can be caused by reflectors at or beyond the first Fresnel zone. Fresnel zones are ellipsoids with transmitter and receiver at the foci and the surface defined by all paths that are an odd-multiple of a half-wavelength farther than the direct path between transmitter and receiver, causing cancellation
Implementation Method 3
processing the peak RSSI values to determine the NEAR/FAR status by correlating the RSSI envelope and using autocorrelation of the signal over time
Implementation Method 4
with hysteresis applied to stabilize state transitions
Data Source
AI summary
A method and apparatus for determining proximity of a headset relative to its base. A plurality of frequency swept RSSI signals are measured and processed to determine a near status or a far status of the headset relative to its base. In one example, a peak RSSI signal is identified in the plurality of frequency swept RSSI signals. The peak RSSI signal is compared to a near/far threshold RSSI value to generate a near status or far status indication.