A Systematic Review on the Data Interoperability of Application Layer Protocols in Industrial IoT

Due to the rising popularity of the Internet of Things (IoT), interconnected infrastructures with better flexibility and efficiency are being developed for industry 4.0. The use of IoT in industry 4.0 introduces a new term "Industrial IoT (IIoT)", which allows remote monitoring of wide-ranging industrial processes. IIoT tends to function with a large number of heterogeneous devices, therefore, data interoperability is the biggest challenge in achieving seamless real-time communication. To achieve data interoperability, there is a need to integrate various IoT application layer protocols; separately, as well as, with other data acquisition protocols along with hardware/software platforms. Although such integrations are frequently presented in the state-of-the-art, a comprehensive investigation and analysis of such approaches in single research work are hard to find. Therefore, in this article, a Systematic Literature Review (SLR) is presented by investigating 34 influential research works, published during 2014-2020, where interoperability of application layer protocols is performed for IIoT. Consequently, the selected research studies are divided into three categories: 1) Integration of IoT application layer protocols- 13 papers; 2) Integration of IoT and data acquisition protocols-6 papers; 3) Integration of IoT protocols with hardware/software platforms-15 papers to resolve interoperability issues. Moreover, nineteen (19) tools used for integration in the selected research works are identified. Furthermore, leading approaches to perform such integrations are recognized, e.g., Gateways. It has been concluded that although researchers frequently propose centralized (e.g., gateway or protocol converter) and distributed intermediator (e.g., Middleware) to achieve required interoperability for IIoT, it is a need of a day to develop a device level solution without the involvement of intermediator. This will solve different interoperability problems in industries like scalability, load balancing, and a single point of failure.