  The Internet of Things (IoT) will bring about the next industrial revolution
in Industry 4.0. The communication aspect of IoT devices is one of the most
critical factors in choosing the suitable device for the suitable usage. So
far, the IoT physical layer communication challenges have been met with various
communications protocols that provide varying strengths and weaknesses.
Moreover, most of them are wireless protocols due to the sheer number of device
requirements for IoT. This paper summarizes the network architectures of some
of the most popular IoT wireless communications protocols. It also presents a
comparative analysis of critical features, including power consumption,
coverage, data rate, security, cost, and Quality of Service (QoS). This
comparative study shows that Low Power Wide Area Network (LPWAN) based IoT
protocols (LoRa, Sigfox, NB-IoT, LTE-M ) are more suitable for future
industrial applications because of their energy efficiency, high coverage, and
cost efficiency. In addition, the study also presents an industrial Internet of
Things (IIoT) application perspective on the suitability of LPWAN protocols in
a particular scenario and addresses some open issues that need to be
researched. Thus, this study can assist in deciding the most suitable protocol
for an industrial and production field.
