Grouped WLAN Channel Access for Scalable STA Power Savings
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Solution Overview
Problem
Existing WLAN systems face challenges in supporting large numbers of stations (STAs) due to limitations in channel bandwidth and spectrum fragmentation, leading to inefficient power consumption and increased overhead in traffic indication maps (TIMs), particularly in sub-1 GHz bands like 802.11ah, which cannot effectively manage the power saving requirements of diverse traffic patterns.
Innovation Solution
Implementing a method where STAs receive parameters for channel access and power saving schedules, negotiate power saving methods with the AP, and utilize sectorized beacons and partial virtual bitmaps in TIM elements to optimize channel access and reduce power consumption, especially for sensor and meter-type devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If traditional TIM elements are used to indicate traffic for all STAs, then all STAs can be notified of their traffic status, but the overhead increases significantly and power consumption rises for large numbers of STAs
Solution Approach 1:
The patent segments the set of all STAs into multiple groups, where each group is assigned a separate group traffic indication map (GTIM) element. This segmentation allows the system to indicate traffic status for multiple STAs using multiple smaller GTIM elements rather than one large TIM element, thereby reducing the overhead while maintaining complete traffic indication coverage for all STAs in the network.
2Reliability
If STAs continuously monitor the channel for traffic indications, then they can immediately detect incoming traffic, but power consumption increases significantly
Solution Approach 1:
The patent implements periodic channel access opportunities for different STA groups, where STAs wake up at scheduled intervals to monitor for traffic indications specific to their group. This periodic monitoring approach allows STAs to remain in low-power states between monitoring intervals while still reliably detecting incoming traffic when they do wake up, significantly reducing overall power consumption compared to continuous monitoring.
3Quantity of substance
If channel bandwidth is increased to support more STAs, then more STAs can be served simultaneously, but spectrum availability is limited and fragmentation prevents bandwidth expansion
Solution Approach 1:
The patent segments the STA population into multiple groups that can access the channel at different times and frequencies. By creating multiple STA groups with dedicated channel access opportunities, the system can support a larger total number of STAs than would be possible with a single wide channel, effectively overcoming the spectrum bandwidth limitation through temporal and spatial multiplexing of multiple narrower channels.
4Productivity
If all STAs are allowed to access the channel simultaneously, then channel utilization is maximized, but collision probability increases and efficiency decreases
Solution Approach 1:
The patent implements periodic channel access slots assigned to different STA groups, where each group is granted channel access at specific time intervals. This periodic scheduling prevents simultaneous channel access attempts by all STAs, thereby reducing collision probability and improving channel access success rates while maintaining high overall channel utilization through efficient time-division multiplexing of multiple STA groups.
Data Source
AI summary
A method and apparatus for power savings in a wireless local area network (WLAN) are disclosed. A station (STA) may receive parameters that associate the STA to a specific group of STAs and perform a channel access during a period that is allowed for the group of STAs based on the parameters. The STA may receive information regarding an access slot that is allowed for the group of STAs and access a channel during the access slot. The STA may receive a schedule for wake up from a doze state and goes in and out of the doze state based on the schedule. A highest channel access priority may be provided to a sensor or meter type of STA. The STA may indicate to an access point (AP) that the STA will not listen to a traffic indication map (TIM) or a delivery TIM (DTIM) in a beacon.