Developing an asynchronous NoAck-based full-duplex MAC for IEEE 802.11 networks in a systems approach

Many studies have introduced full-duplex (FD) medium access controls (MAC) in wireless networks that realize the physical FD capability of the latest devices. However, practical experiences with 802.11 wireless LANs (WLANs) have not yet been addressed. This study proposes a novel FD MAC that extends the IEEE 802.11 based on no acknowledgment (NoAck) data transmission. Because ACK is not needed after data transmission, the MAC can be purely asynchronous; there is neither overhead required for synchronizing transmission, such as request-to-send/clear-to-send (RTS/CTS) handshaking, nor wasted time even in asymmetric traffic. The proposed MAC also provides access point (AP) initiated uni-directional full-duplex (AP-initiated UFD) transmission, which has mostly not been supported in practice, by extending the carrier sense condition. An approximated collision avoidance method is also introduced, where a CTS frame without a preceding RTS is transmitted by AP using FD capability to protect the frame being received. A prototype of the proposed MAC is implemented in ns-3 network simulator, and extensive simulation experiments are conducted in various test setups to validate the correct MAC behaviors, performance improvement, and fairness. The results show that performance improvements, more than twice as high under favorable conditions, are possible while maintaining interoperability with legacy devices.