U-APSD Trigger Frame Synchronization via Medium Sensing
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Solution Overview
Problem
In wireless LAN environments, mobile phones operating in U-APSD mode experience collisions between trigger frames, leading to delays and reduced quality of service, which existing technologies fail to adequately address without increasing bandwidth consumption through additional signaling.
Innovation Solution
Mobile phones synchronize trigger messages by sensing the end of another device's unscheduled service period and transmitting after a specified interval, ensuring no collision occurs without requiring additional signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If mobile phones transmit trigger frames independently in U-APSD mode, then power saving is achieved, but trigger frame collisions occur causing delays and reduced quality of service
Solution Approach 1:
Each mobile phone performs preliminary sensing of the wireless medium to detect the ending time of another phone's unscheduled service period before transmitting its own trigger frame. This advance detection and timing coordination prevents trigger frame collisions while maintaining independent U-APSD operation, thereby preserving both power saving and quality of service benefits
2Reliability
If additional signaling is used to coordinate trigger frame transmission, then trigger frame collisions are avoided, but bandwidth consumption increases
Solution Approach 1:
Mobile phones autonomously sense the wireless medium and detect the ending time of other phones' unscheduled service periods using existing protocol mechanisms. Each phone independently determines when to transmit its trigger frame based on this sensing, eliminating the need for additional coordination signaling while ensuring collision-free transmission. This self-service approach maintains reliability without increasing bandwidth consumption
Data Source
AI summary
A wireless LAN is comprised of a number of wired infrastructure devices, including at least one access point able to support a number of wireless communication devices configured to operate in the U-APSD mode. The wireless communications devices periodically contending for the wireless medium to transmit trigger messages to the access point and the access point responding by transmitting at least one frame of information. The wireless communications devices operate to synchronize the transmission of their trigger messages such that the possibility that the messages collide with one another is minimized.