Achieving Minimum Latency in Multi-Hop MAC Protocol for Wireless Sensor Networks

Achieving low latency and high energy efficiency are critical requirements in many of sensor network applications. Combining the duty cycling mechanism and multi-hop transmission is one of the solutions to this problem. Multi-hop protocols such as demand wakeup MAC (DW-MAC) schedule data transmissions during the sleep period. In so doing, a data packet can traverse multiple hops within a single operational cycle. By introducing a scheduling parameter, called proportional mapping function, DW-MAC can provide better performance in terms of both latency and energy efficiency, while avoiding data collision. In this paper, we derive the minimum value R_min of the scheduling function by numerically analyzing the delivery latency. Using that value, a DW-MAC-like protocol not only guarantees no collisions at the intended receivers but also achieves the minimum latency in the multi- hop scenario. In addition, we also show the upper and lower bounds of the delay. We evaluated the accuracy of our findings by running ns-2 simulations in multiple scenarios.