## 3 Internet of Things in Industrial Applications
### Recapitulation of Contemporary Research Developments in the IIoT
A good number of time synchronization schemes were presented in the literature for achieving high accuracy and productivity in IIoT systems. Pair broadcast synchronization protocol (PBS), group pair selection algorithm (GPA) and spanning tree-based energy-efficient time synchronization (STETS) [44], are a few examples of time synchronization schemes for IIoT as documented in the literature. In [44], a robust time synchronization scheme named _R-sync_ is proposed for distributed systems in IIoT that adopts two timers for timing synchronization using two-way message exchange synchronization. A root node selection algorithm is also presented in this paper [44] for balancing the energy consumption of connected sensor nodes and for extending the lifetime of IIoT networks. It is noteworthy to note that energy consumption and accuracy are crucial considerationpoints to bear in mind when designing time synchronization schemes because the energy of sensor nodes are usually limited. The performance of the proposed robust synchronization scheme (R-sync) is compared with three existing time synchronization schemes including GPA, STETS and timing-sync protocol for sensor networks (TPSN) using NS-2 simulation tool as well as experimental-based evaluation using wireless hardware nodes. Results obtained demonstrated the superior performance of the proposed R-sync time synchronization scheme in comparison to GPA, STETS and (TPSN). From the results obtained, all nodes were synchronized with greater energy-efficiency hence, the proposed R-sync algorithm demonstrated better timing synchronization in comparison to other synchronization schemes. The number of broadcast messages using R-sync, GPA and TPSN algorithms are compared together in the experiment using different communication range for the entire network, where 240 different sensor nodes are deployed in a random manner over an area. The number of broadcast message is need for analyzing the energy-efficiency of an algorithm as propagating messages require maximum consumption of energy during the life time of a node. Further results obtained from the experiment showed that as the communication range increases, R-sync requires a much lower number of broadcast message in comparison to other analyzed synchronization algorithms. The number of broadcast messages are also compared with different number of sensor nodes assuming R-sync, GPA and TPSN with each node set to a communication range of 85 m. The results obtained demonstrated that R-sync offered the least broadcast messages while increasing much slower in comparison to GPA and TPSN. Based on these results, it can be concluded that the energy consumption of R-sync is much lower than other compared synchronization algorithms especially in large-scale and densely connected IIoT systems. The IoT technology also finds beneficial applications in the power generation, power transmission and power distribution industries in application to WSN-based smart grid. A smart grid can simply be described as a fast-emerging and next-generation electricity grid technology that aims at enhancing the efficiency and reliability of the present conventional electric power grid infrastructures through the use of contemporary WSN-enhanced communication technologies for the efficient controls and automation of power grid systems. Since the demand and supply of electric power are designed to be automatically controlled using a two-way communication system in smart grid WSN applications, there is an enormous necessity for developing energy-efficient and energy-balanced routing protocols that will coordinate the transmission and reception of electric power for enhanced reliability and efficiency in electric energy consumption. As a result, a ticket-based routing (TBR) optimization using a genetic algorithm is developed for smart grid applications in [45]. Furthermore, a genetic algorithm is used to minimize the overhead of discovery messages in addition to minimizing the number of tickets.