Beacon Frame TIM Positioning for Wireless Station Power Savings
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Solution Overview
Problem
In wireless communications, stations in standby mode need to wake up frequently to receive lengthy beacon frames to determine if an access point has buffered data, leading to increased power consumption and reduced battery life, especially in handheld devices.
Innovation Solution
The position of the Traffic Indication Map (TIM) element is moved near the beginning of the beacon frame, allowing stations to receive only part of the frame to check for buffered data, and the use of partial virtual bitmaps and a check beacon informational element to indicate significant changes, enabling stations to selectively receive the remainder of the frame only when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If stations receive the entire beacon frame to determine buffered data, then complete information is obtained, but power consumption increases and battery life decreases
Solution Approach 1:
The beacon frame is segmented into multiple parts, with the TIM element positioned at the beginning. Stations in power-saving mode can receive only the first part containing the TIM element to determine buffered data, without needing to receive the entire beacon frame. This segmentation allows stations to obtain necessary information while minimizing wake time and power consumption.
Solution Approach 2:
Stations perform partial reception of the beacon frame by receiving only the TIM element portion at the beginning, rather than the complete frame. This partial action is sufficient to determine whether buffered data exists, eliminating the need to receive excessive data and reducing power consumption accordingly.
2Reliability
If stations wake up frequently to receive beacon frames, then buffered data can be detected, but battery life is reduced
Solution Approach 1:
The beacon frame structure is segmented with the TIM element at the beginning, enabling stations to wake up briefly to receive only this critical portion. This segmentation allows reliable buffered data detection while minimizing the duration of wake state, thereby preserving battery life.
Solution Approach 2:
The TIM element is placed at the beginning of the beacon frame structure, performing the critical data indication function preliminarily. Stations can check this preliminary information quickly to determine if full beacon reception is necessary, reducing the frequency and duration of wake-ups and extending battery life.
3Loss of time
If the TIM element is positioned at the beginning of the beacon frame, then stations can receive only part of the frame, but the beacon frame structure must be modified
Solution Approach 1:
The beacon frame is segmented with the TIM element positioned at the beginning, creating a logical division between critical data indication and other beacon information. This segmentation enables stations to receive only the necessary portion, reducing wake time while the structural modification remains a one-time configuration change.
Data Source
AI summary
Stations in standby mode periodically wake up to check for buffered data at the access points. Traditionally, the information is available by checking the periodic beacon frame for a traffic indication map (TIM). Unfortunately, the length of beacons has steadily increased with the progression of the various wireless standards requiring stations to wake up for longer periods to merely check for buffered data. Several approaches are disclosed which address this shortcoming, including the broadcast of TIM frames, the partial reception of beacon frames and the use of an embedded TIM frame within a beacon frame.