Keeping the UE awake
摘要
說明書
By of further background, with respect to power savings mode in WiFi, power consumption on the Wi-Fi receive path is often about a third lower as compared to the transmit path. Thus, it may be more power efficient to shut down the transmit path and only listen when no outgoing frames are present. Further power savings can be achieved by the WiFi Station (STA) when it indicates to the access point (AP) (or wireless LAN controller) that it is entering power save mode and shut down its receive path. The AP (or wireless LAN controller) stores frames destined for a given STA in power save mode, and sends them to the STA when requested to do so. During association, a given STA uses the Listen Interval parameter to indicate to the AP how many beacon intervals it shall sleep before it retrieves the queued frames from the AP. The AP might not drop any queued frames until the STA's Listen Interval elapses.
In existing approaches, a given STA may enter power-save mode by sending a Null frame to the AP with the Power Management bit set. From then on, the AP (or wireless LAN controller) stores the packets destined to the STA in a per-STA queue, and sets the TIM field in the beacon frame to indicate that packets destined for the STA have been queued at the AP. The STA may wake up from sleep every Listen Interval to receive the beacon frame and, when it detects that the TIM field for it has been set, it may send a PS-Poll frame to the AP. In response, the AP may send the first queued frame to the STA. The STA may receive the queued data frame, and if the More Data field in this frame is set, it may send another PS-Poll frame to the AP. In some cases, the STA continues to send PS-Poll frames to receive the queued frames and when none are left, it goes back to sleep until the next Listen Interval.
