  The Internet of Things (IoT) technology uses small and cost-effective sensors
for various applications, such as Industrial IoT. However, these sensor nodes
are powered by fixed-size batteries, which creates a trade-off between network
performance and long-term sustainability. Moreover, some applications require
the network to provide a certain level of service, such as a lower delay for
critical data, while ensuring the operational reliability of sensor nodes. To
address this energy challenge, external energy harvesting sources, such as
solar and wind, offer promising and eco-friendly solutions. However, the
available energy from a single energy source is insufficient to meet these
requirements. This drives the utilization of a hybrid energy harvesting
approach, such as the integration of solar and wind energy harvesters, to
increase the amount of harvested energy. Nevertheless, to fully utilize the
available energy, which is dynamic in nature, the sensor node must adapt its
operation to ensure sustainable operation and enhanced network performance.
Therefore, this paper proposes a hybrid energy harvesting-based energy neutral
operation (ENO) medium access control (MAC) protocol, called HENO-MAC, that
allows the receiver node to harvest energy from the solar-wind harvesters and
adapt its duty cycle accordingly. The performance of the proposed HENO-MAC was
evaluated using the latest realistic solar and wind data for two consecutive
days in GreenCastalia. The simulation results demonstrate that the duty cycle
mechanism of HENO-MAC effectively utilizes the harvested energy to achieve ENO
and uses the available energy resources efficiently to reduce the packet delay
for all packets and the highest priority packet by up to 28.5% and 27.3%,
respectively, when compared with other existing MAC protocols.
