Wireless LAN Frame Exchange for Low Power Devices
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Solution Overview
Problem
Low-power devices in wireless LAN systems face challenges in efficient frame exchange due to limited transmission/reception operations within specific time intervals and require effective time synchronization in scenarios with a large number of devices, such as Machine-to-Machine (M2M) communication.
Innovation Solution
The method involves an access point (AP) initiating frame exchange with a station (STA) based on the STA's maximum awake time, which is communicated through frames like the PS-Poll, and includes transmitting and receiving Time Synchronization Function (TSF) timer information to ensure accurate timing and synchronization, even when the STA does not listen to beacon frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low-power devices limit transmission/reception operations to specific time intervals to save energy, then power consumption is reduced, but frame exchange efficiency deteriorates
Solution Approach 1:
The station transmits a PS-Poll frame in advance to request buffered data from the access point before entering sleep mode. This preliminary action ensures that the access point prepares and transmits data during the station's limited awake time, resolving the contradiction by enabling efficient frame exchange within the constrained time interval while maintaining power savings.
2Use of energy by moving object
If low-power devices do not listen to beacon frames to save energy, then power consumption is reduced, but time synchronization accuracy deteriorates
Solution Approach 1:
The access point acts as an intermediary by including Time Synchronization Function (TSF) timer information in the data frame it transmits in response to the PS-Poll frame. This allows the station to update its time synchronization without listening to beacon frames, resolving the contradiction by providing accurate time information through the data frame intermediary while maintaining power savings from not listening to beacons.
3Use of energy by moving object
If frame exchange is performed within limited awake time intervals, then power management is optimized, but time synchronization complexity increases
Solution Approach 1:
The access point combines multiple functions into a single data frame transmission: responding to the PS-Poll request, delivering buffered data, and providing TSF timer information for time synchronization. This merging reduces the number of separate frames and interactions needed, simplifying the time synchronization process while maintaining optimized power management within limited awake time intervals.
Data Source
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AI summary
The present invention relates to a wireless communication system, and more particularly to a method for exchanging a frame for a low power device and an apparatus therefor in a wireless LAN system. A method for enabling an access point (AP) to exchange a frame with a station (STA) in a wireless LAN system according to an embodiment of the present invention includes the steps of receiving the information of the maximum awake time from the STA. When the frame exchange is expected to be accomplished within the maximum awake time, the frame exchange can be performed. When the frame exchange is expected to exceed the maximum awake time, the frame exchange is stopped, and a new back-off procedure can be invoked.