###### Abstract  
The Industrial Internet of Things (IIoT) applications are required to provide precise measurement functions as feedback for controlling devices. The applications traditionally use polling-based communication protocols. However, in polling-based communication over current industrial wireless network protocols such as ISA100.11a, WirelessHART have difficulty in realizing both scheduled periodic data collection at high success ratio and unpredictable on-demand communications with short latency. In this paper, a polling-based transmission scheme using a network traffic uniformity metric is proposed for IIoT applications. In the proposed scheme, a center node controls the transmission timing of all polling-based communication in accordance with a schedule that is determined by a Genetic Algorithm. Communication of both periodic and unpredictable on-demand data collection are uniformly assigned to solve the above difficulties in the schedule. Simulation results show that network traffic is generated uniformly and a center node can collect periodic data from nodes at high success ratio. The average success probability of periodical data collection is 97.4% and the lowest probability is 95.2%. the industrial IoT; polling-based communication; scheduling +
Footnote †: journal:  
0000-0001-998-3000-0000-0000-0000-0000-0000-0000-00000-0000-  
meters connected to the network and for sending the retrieved data to the management system from smart meters. Both AMI and DA use polling schemes to exchange messages between a central device and end devices. In addition, a real-time system such as DA or PA reacts or responds to the applications within a fixed amount of time in order to avoid system failures. Both processing and reacting should be done within a pre-determined deadline that includes communication latency. Traditional PA systems use data collection protocols like Modbus that were originally designed for use with low-bandwidth wired communications such as serial communications and tolerant of long communication latency [9]. Traditional dedicated wired communication protocols for industrial applications have been well designed to meet requirements regarding the deadline. The IoT needs connectivity for devices and Industrial Wireless Sensor Networks (IWSNs) [10; 11] have been emerging as a new means of wireless communications for the IoT. Recently, several protocols for IWSNs such as WirelessHART [12], ISA100.11a [13], and IEEE802.15.4e [14], have been developed and standardized in order to increase the communication reliability in a wireless network with frequent packet loss and big latency under the heavy network utilization. These standards are time-synchronized and assigned communication timings when devices join the wireless network. Both application data packets and network control packets are transmitted according to the assignment. When polling-based protocols for industrial applications are used over IWSNs, the number of retransmissions of polling queries over IWSN layer should be considered in order to maintain a high reliability of industrial systems. At the same time, their timing of the retransmission should be carefully considered in order to keep the deadline. Moreover, industrial applications as described above basically gather heterogeneous periodic information from field devices. The transmission frequency of periodic information collection is normally static. At the same time, they also require unpredictable communication for gathering on-demand data or operating devices by a center device within specific end-to-end deadlines [15; 16; 17]. In general, traditional industrial communication protocols over wired communications take into consideration maintaining the deadline even if the unpredictable communication occurs in the network. For frequent data collection in DA, the wired network load can be as much as ten times less than upper bound [18].