POWER SAVE TRIGGER

摘要

Apparatuses and methods in a wireless local area network are disclosed for delivering queued downlink (DL) data from an access point (AP 110) to a plurality of wireless stations (STAs). The AP 110 determines, for each of the plurality of STAs, a presence of a corresponding set of queued DL data, transmits a beacon frame 510 identifying which of the plurality of STAs has queued DL data, and transmits, to each of the identified STAs, permission 520 to request delivery of queued DL data. Next, AP 110 receives, from each of the identified STAs, a request 530 for delivery of the queued DL data. Then, AP 110 concurrently transmits, to each of the identified STAs, the corresponding set of queued DL data 540. The AP 110 preferably uses power save (PS) trigger frames 520 to schedule concurrent DL data transmissions to the plurality of STAs. By using PS trigger frames 520, the plurality of STAs does not need to contend with each other for medium access to request delivery of queued DL data. Instead, a number of STAs that receive the PS trigger frame 520 may concurrently transmit requests 530 for delivery of the queued DL data without contending with each other for medium access, thereby reducing delays associated with medium access contention operations. Upon receiving the requests 530, the AP 110 may concurrently transmit queued DL data 540 to multiple STAs using OFDMA communications or multi-user multiple-input multiple-output (MU-MIMO) communications. ln an alternative embodiment, the AP's permission and the STA's request are implicit. ln this case, the AP 110 and the receiving STA5 exchange PS-Trigger capabilities and/or negotiate a number of PS-Trigger parameters prior to the delivery of queued DL data from the AP 110 to the receiving STA5. For at least some implementations, the AP 110 may selectively use PS-Trigger frames to schedule delivery of queued DL data based on a level of congestion on the shared wireless medium. The STAs may indicate their PS-Trigger frame capabilities in any suitable manner, for example in an association request. The WLAN may be formed by a plurality of Wi-Fi access points that may operate according to the IEEE 802.11 family of standards.