Asynchronous MAC Protocol with QoS Awareness in Wireless Sensor Networks

In wireless sensor networks (WSNs), MAC protocols utilize duty cycling to extend the network lifetime. Receiver-Initiated MAC (RI-MAC) is an asynchronous duty cycling protocol, which schedules transmissions based on receivers. By letting a receiver initiate the rendezvous for the transmissions between senders and the receiver, the protocol achieves good latency performance at the cost of high energy consumption at the senders. On the other hand, different types of traffic are very popular in WSNs. The MAC protocols are necessarily to be equipped QoS (quality of service) mechanisms to handle with the variation of traffic. In this paper, we propose AQ-MAC; a new asynchronous MAC protocol with QoS awareness. AQ-MAC adopts the receiver-initiated manner and provides QoS service per packet following the priority imposed. When a node has an incoming packet with a high priority, it immediately turns on the radio in order to wait for a transmission initiated by a receiver. Otherwise, the node keeps a low priority packet in a queue and sends out in a burst until a high priority packet comes or after a timeout value. In addition, AQ-MAC utilizes a packet concatenation scheme to improve the energy efficiency by reducing control overhead. We have evaluated AQ-MAC in multiple scenarios using ns-2. The results show that AQ-MAC adapts well with different types of traffic as well as achieves good performance in terms of energy efficiency and latency.