Load-Aware Power Saving Mechanism in WLAN

In wireless local area networks (WLANs), the power saving mechanism for distributed coordination function (DCF) allows stations (STAs) to periodically wake up and check the existence of buffered packets in the access point (AP). If notified by the beacon of buffered packet's presence, an STA contends for sending the PS-Poll to the AP which will respond with the corresponding buffered packet either 1) immediately (immediate-send), or 2) at a later time (later-send). IEEE 802.11 standard does not specify the detailed scheme of later-send and most current mechanisms adopt immediate-send. Though immediate-send performs well under light load condition, it is inefficient under heavy load condition because of the existence of some STAs contending throughout the whole beacon interval at the price of corresponding power consumption but getting no access opportunity, which degrades the power saving performance of both total power consumption and energy efficiency, i.e. the average power consumed for one unit of payload. The authors propose and analyze a load aware power saving mechanism (LAPS) that uses immediate-send under light load condition and uses a proposed detailed mechanism of later-send under heavy load condition. The threshold to divide light and heavy load is also calculated-numerical results show the effectiveness of our mechanism.