# Polling Mechanisms for Industrial IoT Applications in Long-Range Wide-Area Networks
## 1 Introduction  
The industrial Internet of Things (IIoT) is rapidly transforming the way we operate and manage industrial assets. By connecting sensors, actuators, and other devices to the internet, IIoT can provide real-time data and insights that can be used to improve efficiency, productivity, and safety. As introduced in [1, 2], the concept of functional safety is relevant in industrial systems. Functional safety is the ability of a system to perform its required safety functions in a reliable manner under all conditions, including normal operation, abnormal operation, and fault conditions. One challenge is that the IIoT is a complex and heterogeneous environment, with a wide variety of devices and networks. This can make it difficult to ensure that all devices and networks comply with functional safety requirements. Another challenge is that the IIoT is a dynamic environment, with devices and networks constantly changing. This can make it difficult to maintain functional safety over time. IIoT is a trending solution to collect data from a large number of devices, which as can be seen, comes with challenges. Polling is a popular way to gather data in industrial use cases and digitalization because it is simple and efficient. The central server polls each device at regular intervals, and the device sends back the data that it has collected. This can be completed over a variety of networks, including wired, wireless, and cellular. Polling has a number of advantages, including the following:  
1. Simple: Polling is a simple and straightforward way to gather data. The central server does not need to know anything about the devices that it is polling, and the devices do not need to be able to communicate with each other. Efficient: Polling can be an efficient way to gather data, especially if the devices are not generating a lot of data. The central server can poll the devices at regular intervals, and the devices only need to send back the data that has changed since the last poll. 3. Scalable: Polling can be scaled to accommodate a large number of devices. The central server can simply poll more devices at regular intervals. However, polling also has some challenges to overcome, including the following:  
1. Latency: Polling can introduce latency into the system. The time it takes for the central server to poll a device and for the device to send back the data can add up. 2. Battery drain: Polling can drain the batteries of the devices that are being polled. If the devices are polled too often, the batteries may not last as long. 3. Bandwidth usage: Polling can use up a lot of bandwidth, especially if the devices are requested by the polling master to generate data more frequently. Polling has been used for decades to gather data from a variety of devices. This means that there are a lot of tools and resources available to help implement polling on a system. It is compatible with a wide range of devices. So, it can be used to gather data from a variety of devices, including sensors, actuators, and controllers. This makes it a flexible and versatile solution for gathering data in industrial use cases, which comprise applications such as environmental monitoring, asset tracking, or smart metering. While low-power wide-area networks (LPWANs) offer long battery life, low data rates, and wide coverage, their limited bandwidth presents challenges for polling in industrial Internet of Things (IIoT) applications. This is particularly true for LoRaWAN, a popular LPWAN technology. Although LoRaWAN boasts long range, low power, wide availability, security, and private network deployment, its bandwidth constraints necessitate careful consideration when employing polling techniques. These challenges include the following:  
1. Bandwidth overhead: polling can consume a significant amount of bandwidth, which can be a problem for LoRaWAN. 2. Latency: polling can introduce latency, as the central controller must wait for each device to respond before it can request data from the next device. 3.