Performance analysis of energy-efficient MAC protocols using bidirectional transmissions and sleep periods in IEEE 802.11 WLANs

The Distributed Coordination Function (DCF) is the mandatory access method for any compliant device in Wireless Local Area Networks (WLANs) based on the IEEE 802.11 Standard. WLAN Access Points (APs) and stations (STAs) contend for the access to the wireless channel in order to transmit data by using a variation of Carrier Sense Multiple Access (CSMA). In doing so, they consume a significant amount of energy for continuously monitoring the channel state. In this paper we investigate backwards-compatible mechanisms to increase throughput and energy efficiency in WLANs during contention periods based on DCF. The first mechanism is called Bi-Directional DCF (BD-DCF) because it allows for bidirectional transmissions between APs and STAs with a single channel access invocation. The second mechanism is called Bi-Directional Sleep DCF (BDSL-DCF) as it allows overhearing STAs to enter the sleep state, i.e. switch off the radio transceiver, during bidirectional transmissions. We analyze the performance limits of the proposed protocols in terms of throughput and energy efficiency considering different values for the data packet length and data rate. The results of this work show that the BD-DCF and BDSL-DCF protocols can improve throughput up to 60% and energy efficiency up to 360% when compared to legacy DCF.