GS-MAC: A Scalable and Energy Efficient MAC Protocol for Greenhouse Monitoring and Control Using Wireless Sensor Networks

Wireless sensor networks (WSNs) are widely used in agricultural greenhouses to monitor and control farming-related parameters. These networks are composed of multiple sensor nodes, usually deployed in an ad hoc fashion. But the nodes mostly run on batteries. So if a node fails or loses power, it creates areas in the network with no sensor coverage, consequently affecting the entire system. Therefore minimizing energy use is essential for extending the network lifetime. Researchers have proposed multiple energy-saving schemes in the past but the majority have not eliminated the sources of energy waste, and are not suitable for greenhouse applications. In light of this, we propose GS-MAC, a scalable and energy-efficient medium-access-control (MAC) protocol specialized for greenhouse monitoring and control: Unlike previous designs, our technique is applicable to both homogenous and heterogeneous settings. To minimize power use, nodes periodically sleep, but GS-MAC avoids periodic node synchronizations, unlike traditional duty cycling mechanisms. Instead, nodes use coordinated universal time (UTC) to maintain strict schedules to avoid energy waste and maintain constant low-duty cycles even with increasing node density. GS-MAC also uses short node addresses to reduce packet overheads. Finally, GS-MAC adopts a contention approach on reserved time slots scheduled between communication rounds to maintain scalability. Our work is evaluated on MATLAB, with simulation parameters obtained from actual hardware. The experiment results show that GS-MAC is more efficient by at least 2.7 times compared to previous research in terms of duty cycling, energy consumption, and network lifetime, in exchange for increased delays.