Power Save Poll; 802.11 Power Save Without Poll - Infineon AIROC CYW43012 Manual

Low-power system design with AIROC™ Wi-Fi & Bluetooth® combo
chip and PSoC™ 6 MCU
WLAN power optimization techniques
3.1.4.1

Power save poll

Power save poll suits for STAs that primarily transmit data to the Wi-Fi network at low-duty cycles. The PS-poll
mechanism works as follows:
1. STA sends a frame to the AP with the Power Management bit set and then goes to sleep.
2. AP notes that the STA has gone to sleep, and buffers frames for the STA.
3. STA wakes up periodically to check the AP beacon frame for an indication of buffered frames. The wake
period depends on the configured listen interval and whether the STA is configured to receive group-
addressed frames from a beacon containing a DTIM.
4. If the AP indicates that it has buffered frames addressed to the STA, the STA sends a PS-Poll frame to the AP.
5. The AP sends a frame to the STA and sets the 'More Data' bit if additional frames are buffered.
6. The STA might send another PS-Poll frame to retrieve additional buffered frames (if the More Data bit was
set) or return to sleep.
7. When the STA needs to transmit data, it can wake up and transmit data anytime without waiting for the
beacon interval as AP is active all the time.
AP
Slave listening to Beacon @ DTIM interval
STA1
(With PS-Poll)
Figure 3 Power save poll
3.1.4.2

802.11 power save without poll

A non-standard mechanism known broadly as 802.11 power save without poll (PS-non-poll) enables STAs to
use 802.11 power saving based on a 'trigger' frame as follows:
STA sends a frame to the AP with the 'Power Management' bit set and then goes to sleep.
1.
2. AP notes that the STA has gone to sleep and buffers frames for the STA.
3. STA wakes up periodically. The STA may (or may not) first check the AP beacon frame for an indication of
buffered frames before sending any frames to the AP.
4. The STA sends a Null Function data frame, or a data frame if available, to the AP with the Power
Management bit cleared.
5. The AP notes that the STA is awake and sends buffered frames.
6. STA receives the frames, waits for a timeout period to receive additional frames (if available), and then
returns to sleep as described in Step 1.
Application note
DTIM = 3
Beacon with
TIM
DTIM
PS-Poll from STA1
TIM with data for
STA1
12
Data for STA1
002-27910 Rev. *C
2023-05-29