A Self-adaptive Low Delay MAC Protocol For Event-driven Industrial Wireless Networks

In many industrial wireless networks, sensor nodes sense an event and then generate related data packets to transmit. In such event-driven networks, contention medium access control (MAC) protocols such as 802.11 DCF are widely used to address the burst traffic. However, due to the fixed probability distribution of contention time-slot selection (PDCS), traditional methods may cause severe collisions when a great number of packets are being transmitted in a short period. To deal with this problem, a MAC protocol that dynamically adjusts PDCS and contention window simultaneously is proposed in this paper. This method exploits the spatial and temporal relationship of packet generation among source nodes in industrial wireless networks. In this method, sensor nodes related to the same event source converge to the optimal PDCS quickly and collisions are significantly reduced. Delay performances of this method are evaluated through simulations. According to the simulation, our protocol outperforms current MAC protocols in access delay by about 20% in event-driven networks.