HE-MAC: Hop Extended MAC Protocol for Wireless Sensor Networks

Due to the limited battery in wireless sensor networks (WSNs), energy efficiency is an important factor when designing a MAC protocol. To minimize energy consumption, most of MAC protocols in WSNs exploit low duty cycling. Among those, RMAC allows a node to transmit a data packet for multiple hops in a single duty cycle, which is made possible by exploiting a control frame named Pioneer (PION) for the path set up. In this paper, we present a MAC protocol called hop extended MAC (HE-MAC) that enables a node to transmit a data packet for more hops in a single duty cycle compared to RMAC. It employs an EXP (Explorer) frame to set up the path for multiple hop transmission, which contains the information about the maximum hop that a packet can travel through in a single duty cycle. Using the information in EXP and an internal state of ready-to-receive (RTR), HE-MAC extends the relay of a packet beyond the termination of the data period by two more hops compared to RMAC. Also along with our proposed adaptive sleeping method, it also reduces power consumption. We analytically obtain the packet latency in HE-MAC and evaluate the performance through ns-2 simulations. Compared to RMAC, HE-MAC shows 42.2% less power consumption and 23.6% less packet delay on average for a random topology of 300 nodes.