Optimal Hop Extended MAC protocol for wireless sensor networks

In wireless sensor MAC protocols, duty cycling has been exploited to put sensor nodes into sleeping state most of the time, thereby saving the limited battery efficiently. In this paper, we present a MAC protocol called Hop Extended MAC (HE-MAC) that enables a source node to transmit a data packet for multiple hops in a single duty cycle. It employs an EXP (Explorer) frame to set up the path for multiple hop transmission, which contains the information about the maximum number of hops that a packet can travel through in a single duty cycle. Using this information and an internal state of Ready-to-Receive (RTR), HE-MAC relays the packet beyond the termination of the data period. Along with our adaptive sleeping method, it additionally reduces power consumption. Then, we analytically obtain the packet latency of HE-MAC and find its optimal wakeup duration with respect to packet latency. Through ns-2 simulations, we observe that HE-MAC achieves 42.2% less power consumption and 23.6% less packet delay on average compared to RMAC 9] for a random topology of 300 nodes. With the allocated optimal wakeup duration, the latency of HE-MAC is reduced by 54.3% at maximum and 41.1% on average, compared to the case of default setting.