Power efficient PS-Poll
A IEEE 802.11 Wireless Local Area Network (WLAN) system of an access point (AP) and one or more stations (STAs) reduces power consumption and increases battery life of power efficient low power STAs by decreasing the amount of time that a power efficient low power STA remains in an awake state. After indicating power efficient low power operation during association with an AP supporting such operation, the power efficient low power STA may enter the doze state from the time that the power efficient low power STA sends a PS-Poll until the power efficient low power STA receives the buffered DATA frame from the AP. While implementing the power efficient PS-Poll method, the AP can send the buffered DATA frame to the STA SIFS after the AP sends an ACK to the received PS-Poll from the STA.
1. A method of reducing the power used by a wireless station, the method comprising:
waking a first wireless station from a doze state to send a PS-Poll frame from the wireless station to an access point;
in response to the PS-Poll frame being received at the access point, receiving at the first wireless station from the access point an acknowledgement frame containing a traffic buffering bit indicating that traffic for the first wireless station is buffered by the access point and that a data frame is available to transmit to the first wireless station;
detecting a frame transmitted by a second wireless station that is not for the first wireless station, the second wireless station being different from the access point, after receiving at the first wireless station from the access point the acknowledgement frame indicating that the data frame is available and before receiving at the first wireless station the data frame transmitted by the access point;
in response to detecting the frame transmitted by the second wireless station that is not for the first wireless station, causing the first wireless station to re-enter the doze state before receiving at the first wireless station the data frame transmitted by the access point;
waking the first wireless station from the doze state a second time; and
receiving at the first wireless station the data frame transmitted by the access point.
2. The method of claim 1 , further comprising:
receiving, at the first wireless station, before receiving the acknowledgement frame a beacon frame from the access point, the beacon frame including an indication of support for a transmission opportunity power save operation in a specific transmission opportunity.
3. The method of claim 2 , wherein the first wireless station re-enters the doze state during the specific transmission opportunity in which a receiver of the frame transmitted by the second wireless station in the specific transmission opportunity is not the first wireless station.
4. The method of claim 2 , wherein the first wireless station does not receive the frame transmitted by the access point in the specific transmission opportunity when a receiver of the frame transmitted by the second wireless station is not the first wireless station.
5. The method of claim 1 , wherein the first wireless station receives an indication from the access point that the access point supports power efficient low power wireless stations in a basic service set.
6. The method of claim 1 , wherein during association, the first wireless station indicates to the access point that the first wireless station is a power efficient low power wireless station.
7. The method of claim 1 , wherein waking the first wireless station from the doze state to send the PS-Poll frame from the wireless station to the access point includes waking the first wireless station from the doze state after a beacon signal to send the PS-Poll frame from the wireless station to the access point.
8. The method of claim 1 , wherein waking the first wireless station from the doze state the second time includes waking the first wireless station from the doze state the second time within the same beacon cycle.
9. An apparatus that uses reduced power, comprising:
a controller configured to:
wake a first wireless station from a doze state and to send a PS-Poll frame to an access point,
in response to the PS-Poll frame being received at the access point, receive at the first wireless station from the access point an acknowledgement frame containing a traffic buffering bit indicating that traffic for the first wireless station is buffered by the access point and that a data frame is available to transmit to the first wireless station,
detect a frame transmitted by a second wireless station that is not for the first wireless station, the second wireless station being different from the access point, after the acknowledgement frame indicating that the data frame is available is received and before receiving at the first wireless station the data frame transmitted by the access point;
in response to detecting the frame transmitted by the second wireless station that is not for the first wireless station, cause the first wireless station to re-enter the doze state before receiving at the first wireless station the data frame transmitted by the access point;
wake the first wireless station from the doze state a second time; and
receive at the first wireless station the data frame transmitted by the access point.
10. The apparatus of claim 9 , wherein the controller is configured to receive, at the first wireless station, before receiving the acknowledgement frame a beacon frame from the access point, the beacon frame including an indication of support for a transmission opportunity power save operation in a specific transmission opportunity.
11. The apparatus of claim 10 , wherein the first wireless station re-enters the doze state during the specific transmission opportunity in which a receiver of the frame transmitted by the second wireless station in the specific transmission opportunity is not the first wireless station.
12. The apparatus of claim 10 , wherein the first wireless station does not receive the frame transmitted by the access point in the specific transmission opportunity when a receiver of the frame transmitted by the second wireless station is not the first wireless station.
13. The apparatus of claim 9 , wherein the first wireless station receives an indication from the access point that the access point supports power efficient low power wireless stations in a basic service set.
14. The apparatus of claim 9 , wherein the controller is configured, during association, to indicate to the access point that the first wireless station is a power efficient low power wireless station.
15. The apparatus of claim 9 , wherein the controller is configured to wake the first wireless station from the doze state after a beacon signal to send the PS-Poll frame from the wireless station to the access point.
16. The apparatus of claim 9 , wherein the controller is configured to wake the first wireless station from the doze state the second time within the same beacon cycle.
17. A method that reduces the power used by a wireless station, the method, the method comprising:
after receiving an indication that a first wireless station is a power efficient low power wireless station, receiving a PS-Poll frame from the first wireless station at an access point;
in response to receiving the PS-Poll, transmitting to the first wireless station from the access point an acknowledgement frame containing a traffic buffering bit indicating that traffic for the first wireless station is buffered by the access point and that a data frame containing buffered data for the first wireless station is available to transmit;
after transmitting to the first wireless station from the access point the acknowledgement frame indicating that the data frame containing buffered data for the first wireless station is available and before transmitting to the first wireless station from the access point the data frame containing buffered data for the first wireless station, receiving a data frame transmitted by a second wireless station at the access point, the second wireless station being different from the first wireless station;
in response to receiving the data frame transmitted by the second wireless station at the access point, transmitting to the second wireless station from the access point an acknowledgement frame; and
after transmitting to the second wireless station from the access point the acknowledgement frame, transmitting to the first wireless station from the access point the data frame containing buffered data for the first wireless station.
18. The method of claim 17 , wherein the first wireless station enters a doze state upon determining that the frame transmitted by the second wireless station is not for the first wireless station.
19. The method of claim 18 , wherein the first wireless station enters the doze state after transmitting an acknowledgement frame from the first wireless station to the access point that acknowledges the received data frame.
20. The method of claim 17 , wherein, during association, the access point indicates that the access point supports power efficient low power wireless stations in a basic service set.
21. The method of claim 17 , during association, the access point receives an indication that the first wireless station is a power efficient low power wireless station.
22. The method of claim 17 , further comprising:
transmitting a beacon signal before receiving the indication that the first wireless station is the power efficient low power wireless station.
23. An apparatus that reduces the power used by a wireless station, the apparatus comprising:
a controller configured to:
after receiving an indication that a first wireless station is a power efficient low power wireless station, receive a PS-Poll frame from the first wireless station at an access point,
in response to receiving the PS-Poll, transmit to the first wireless station from the access point an acknowledgement frame containing a traffic buffering bit indicating that traffic for the first wireless station is buffered by the access point and that a data frame containing buffered data for the first wireless station is available to transmit;
after transmitting to the first wireless station from the access point the acknowledgement frame indicating that the data frame containing buffered data for the first wireless station is available and before transmitting to the first wireless station from the access point the data frame containing buffered data for the first wireless station, receive a data frame transmitted by a second wireless station at the access point, the second wireless station being different from the first wireless station;
in response to receiving the data frame transmitted by the second wireless station at the access point, transmit to the second wireless station from the access point an acknowledgement frame; and
after transmitting to the second wireless station from the access point the acknowledgement frame, transmit to the first wireless station a data frame containing buffered data for the first wireless station.
24. The apparatus of claim 23 , wherein the first wireless station enters a doze state upon determining that the frame transmitted by the second wireless station is not for the first wireless station.
25. The apparatus of claim 24 , wherein the first wireless station enters the doze state after transmitting an acknowledgement frame from the first wireless station to the access point that acknowledges the received data frame.
26. The apparatus of claim 23 , wherein, wherein the controller is configured to indicate, during association, that the access point supports power efficient low power wireless stations in a basic service set.
27. The apparatus of claim 23 , wherein the controller is configured, during association, to receive an indication that the first wireless station is a power efficient low power wireless station.
28. The apparatus of claim 23 , wherein the controller is configured to transmit a beacon signal before receiving the indication that the first wireless station is the power efficient low power wireless station.