Access Point Transmit Power Control for Mobile Voice Roaming
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Solution Overview
Problem
Existing WLAN technologies face challenges in maintaining voice quality for mobile voice clients due to interference from access points operating on the same channel, where automatic channel selection and transmit power control can compromise voice quality.
Innovation Solution
An access point equipped with circuitry and a power control algorithm that gradually adjusts its transmit power based on the position of mobile voice clients, setting the power level to reach the nearest access point 10 dB above the noise floor, and adjusts this power in increments of 1 dB per second, ensuring seamless roaming and minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If automatic transmit power control is used to reduce interference between access points, then interference is reduced, but voice quality deteriorates
Solution Approach 1:
The system dynamically adjusts transmit power based on real-time conditions rather than using fixed power levels. The access point continuously monitors the positions of mobile voice clients and other access points, then adaptively changes power settings to maintain voice quality while minimizing interference. This dynamic approach resolves the contradiction by allowing the system to optimize both interference reduction and voice quality maintenance based on current network conditions.
Solution Approach 2:
The patent applies different power control strategies to different spatial regions and client types. Instead of uniformly reducing power across all directions, the system identifies specific areas where mobile voice clients are located and maintains appropriate power levels in those zones while reducing power in other directions where interference occurs. This localized quality control allows the system to preserve voice quality for mobile clients while still achieving interference reduction in other areas.
2Object-affected harmful factors
If transmit power is reduced to minimize overlap, then interference is reduced, but coverage area shrinks
Solution Approach 1:
The system dynamically adjusts transmit power based on real-time conditions rather than using fixed power levels. The access point continuously monitors the positions of mobile voice clients and other access points, then adaptively changes power settings to maintain voice quality while minimizing interference. This dynamic approach resolves the contradiction by allowing the system to optimize both interference reduction and voice quality maintenance based on current network conditions.
Solution Approach 2:
The system performs preliminary positioning of mobile voice clients and preliminary calculation of optimal power levels before actual power adjustment occurs. By anticipating the needs of mobile clients and pre-calculating appropriate power settings, the system can reduce power to minimize interference while maintaining adequate coverage through proactive power management rather than reactive adjustments.
3Reliability
If transmit power is adjusted frequently to track mobile client position, then voice quality is maintained, but power control stability deteriorates
Solution Approach 1:
The system implements periodic power adjustments rather than continuous changes. Power is recalculated and adjusted at specific intervals or when certain thresholds are met, such as when a mobile client moves a significant distance or when network conditions change substantially. This periodic action maintains voice quality by responding to significant position changes while avoiding excessive fluctuations that would destabilize power control.
Solution Approach 2:
The system applies partial power adjustments rather than maximum changes. When power needs to be modified to maintain voice quality, the system makes incremental adjustments rather than drastic changes, limiting the magnitude of each power change to maintain stability while still responding to mobile client position changes.
Data Source
AI summary
Operation of a mobile voice client utilizing a WLAN for access is enhanced by controlling the rate at which transmission power is changed by the access point with which the mobile voice client is associated. The access point calculates a target transmit power level based at least in-part on the distance to the nearest fixed position wireless device and the distance to the mobile voice client. The access point then determines whether the target transmit power level differs from a current transmit power level. If the target transmit power level is greater than the current transmit power level, the current transmit power level is increased at a first controlled, non-instantaneous rate such as 1 dB per second. If the target transmit power level is less than the current transmit power level, the current transmit power level is decreased at a second controlled, non-instantaneous rate such as 1 dB per second.