PD-MAC: Pulse Detection Based MAC Protocol in Distributed Wireless Networks

CSMA/CA based MAC protocols, i.e., IEEE 802.11, make use of control messages and backoff scheme to avoid collision in distributed wireless networks. However, the channel utilization of 802.11 decreased dramatically with the development of advanced physical layer techniques, such as OFDM, since increasing data rate makes the control messages transmission and backoff time occupy larger proportion of the transmission period. To address this, we propose PD-MAC. Instead of control message, PD-MAC uses pulse signals to express the control information. Pulses can be transmitted and detected concurrently with the user data, thus the control information transmission and backoff time can be overlapped with user data transmission. Moreover, to make the pulse signal express enough information, PD-MAC utilizes the 2-dimensional feature of OFDM signals, that is, position of pulses in both time domain and frequency domain. We implement the physical layer prototype of PD-MAC with USRP N210 and evaluate MAC layer performance with trace-driven simulation. PD-MAC can achieve 95.4% channel efficiency and provide throughput gains of up to 71.6%, 33.4%, and 11.2% compared with 802.11 DCF, 802.11ec and back2F, respectively.