# Polling Mechanisms for Industrial IoT Applications in Long-Range Wide-Area Networks
## 2 Related Work  
Polling techniques for collecting data have been a topic well studied in the literature for several decades, especially because they have been commonly used in wired industrial networks. Nevertheless, wireless networks are only recently gaining relevance in industrial applications, with the popularity of IIoT and massive digitalization. A number of research papers have been published on the topic of using polling systems in wireless industrial applications. Some of these papers focus on developing new polling protocols that are more efficient and reliable than traditional polling protocols. Other papers focus on developing new methods for managing polling traffic in wireless industrial networks. The following papers are some of the most recent and relevant papers on the topic of polling systems in wireless industrial applications. Authors in [3] provide a comprehensive overview of frequency-domain contention and polling MAC protocols for IEEE 802.11 wireless networks. The paper discusses the advantages and disadvantages of these protocols, as well as their performance in different scenarios, which is a valuable resource for researchers who are interested in using polling systems in wireless industrial applications. The paper provides a good understanding of the different frequency-domain contention and polling MAC protocols that are available, as well as their performance characteristics. Following the IEEE 802.11-based approach, the article in [4] proposes a new rate selection algorithm for IEEE 802.11 industrial wireless LANs (WLANs). The algorithm, called Rate Selection for Industrial Networks (RSIN), is designed to minimize the error probability of polling packets, while considering the deadline imposed on packet delivery. It covers interesting topics for wireless polling but focuses on WLANs. Moreover, ref. [5] proposes a prototype implementation of a critical industrial wireless control system based on ultra-reliable low-latency communication (URLLC). The system uses a polling scheme to ensure that all sensors are read and that all actuators are updated within a tight deadline. This shows a polling application but addresses its uses in a 5G traffic profile and critical system requirements. In [6], authors propose the Acyclic Traffic Scheduling Algorithm (ATSA), which is not specifically designed for polling traffic. However, ATSA can be used to schedule polling traffic by giving polling traffic a higher priority than other acyclic traffic. This will ensure that polling traffic packets are always transmitted before other acyclic traffic packets. The work described in [7] proposes a new Medium Access Control (MAC) protocol for OFDMA-based networks (as Wi-Fi or cellular) in cyber-physical systems (CPSs). The protocol, called Priority-Aware Frequency Domain Polling (PAFDP), is designed to improve the reliability and performance of CPS networks by using priority-aware polling and frequency diversity. Authors in [8] propose a polling-based transmission scheme for industrial IoT applications. The scheme is designed to improve the uniformity of network traffic, which can lead to improved performance and energy efficiency. The paper begins by discussing the challenges of polling-based communication in industrial IoT applications. These challenges include the following: the need to collect data from a large number of devices, to collect data at regular intervals, and to minimize the amount of network traffic. The paper then proposes a polling-based transmission scheme that is designed to address these challenges, assuming the use of current industrial wireless network protocols such as ISA100.11a or Wireless HART. The scheme uses an algorithm to generate a schedule for polling the devices. The schedule is designed to minimize the variance in the time between polls,which can lead to improved uniformity of network traffic. Then, it presents an experimental evaluation of the proposed scheme using a simulation of an industrial IoT network.