Oliver Wang, Product Marketing Manager, Edge Connectivity and Computing, Moxa
In industries that rely on distributed data acquisition in remote areas, such as renewable energy or oil and gas, wired infrastructure is often lacking or impractical.
Although wireless computers provide an ideal solution for these applications, each scenario has different requirements for communication distance, transfer speed, bandwidth, power consumption, costs, and more. Choosing the best wireless IIoT gateway or alternative solution for energy industry applications requires taking these factors and their inherent trade-offs into consideration.
The following key factors—namely, wireless performance, network infrastructure, carrier approvals and compatibility, edge computing, and data and hardware reliability—describe the main considerations for selecting the best wireless solutions for an Industrial IoT gateway application and provide suggestions for how to overcome common pitfalls.
1. Wireless Performance
When choosing a cellular or Wi-Fi IIoT gateway, you need to consider the wireless bandwidth and communication distance for connecting edge systems to the cloud. These wireless performance requirements are largely determined by the data volume. For example, video surveillance files and system logs for remote control and monitoring systems can be quite large. In order to transmit higher volumes of these types of data to the cloud, you need more bandwidth to support faster uplink and downlink speeds, such as LTE Cat. 4 or even a Wi-Fi network.
However, since the wireless modules that provide higher uplink and downlink consume more power and are costlier for wireless carriers to support, data plans for these services are also more expensive. Some wireless carriers may offer more affordable data plans for low-power wide area networks (LPWAN) to businesses that require less data consumption. Although you may be able to negotiate a low monthly rate, such as US$1 per month1, choosing the most suitable option requires carefully calculating your daily or monthly data consumption in advance to stay within the limits of the plan.
Besides the data volume, the frequency and availability of data transmissions also need to be taken into consideration. For instance, some carriers may periodically disconnect NB-IoT modules in order to continuously optimize the number of connected devices on their LPWAN. Moreover, some NB-IoT modules are even designed to enter power saving mode immediately after connecting to an LPWAN in order to save power consumption on the connected device.
Last but not least, the wireless communication distance from your edge systems to the cloud also needs to be considered. To illustrate, Wi-Fi networks that generally have a maximum transmission distance of 50 meters may be insufficient for highly distributed IIoT applications, such oil fields that span vast distances in remote areas far from civilization.
2. Network Infrastructure
After assessing the wireless performance requirements for your industrial application, you will need to carefully consider the type of network infrastructure. Besides the data rates and volume requirements, initial setup fees and total cost of ownership should also be factored into deciding whether you build your own wireless network or use an existing network from a local carrier.
In addition, new cellular connectivity technologies, such as LTE Cat. M1 (LTE-M) or NB-IoT, might not be available in your region yet. As a result, it is crucial to first check carrier availability in order to determine which options you actually have.
Another infrastructure issue to consider is the actual environment in which your application takes place. For instance, Wi-Fi may provide more stable signals and connectivity for restricted areas near densely populated urban communities. On the other hand, cellular solutions may provide better service to remotely located
applications that span a wider area, offer considerable savings on cabling fees, and require less deployment effort. Moreover, LTE technologies can provide a scalable solution in remote outdoor areas where Ethernet wiring is impractical or cost- prohibitive.
3. Approvals and Compatibility
Each region has its own radiofrequency (RF) regulations that specify the wireless equipment you are allowed to import and use within the region. To avoid the risks associated with using a wireless device that is not permitted in your region, Moxa recommends choosing wireless devices that are already covered by the local RF regulator in the region where you want to deploy2.
In addition, different wireless carriers within the same region may also use different LTE bands. Some carriers may even use a specific RF band that is not generally supported by major LTE manufacturers or local competitors. Consequently, you should clarify requirements with your end users before selecting your wireless connectivity solution for collecting and transferring remote data.
Furthermore, some countries—such the United States, Canada, Japan, and South Korea—also require carrier approval before you can register your devices on the carrier’s network. Carrier approval guarantees your devices can operate normally on the carrier’s network and satisfies any criteria for interoperability.
4. Edge Computing
All IIoT applications involve collecting data from field devices, sensors, and other industrial equipment before transmitting the information to the cloud for advanced analytics. These field devices are said to be on the “edge” of the system, which is why they’re called “edge systems”. Although it is possible to send raw data from each edge system directly to the cloud, the latency and associated costs in most cases would be too burdensome. “Edge computing” essentially moves some of the data processing and actuation from the cloud to an IIoT gateway that connects all the field devices at a particular site.
Since each IIoT gateway may act as a data concentrator, protocol converter, and data preprocessing device for all the sensors and equipment that connect to it, a simple cellular router or Wi-Fi access point would not suffice. Industrial applications need to collect data from many different signals and protocols that need to be converted, stored, and preprocessed before transmitting the information over cellular or Wi-Fi networks.
Different IIoT applications may also have varying CPU, memory, storage, or power budget requirements. For example, most data acquisition and transfer applications use a customizable Linux OS platform with basic built-in and external storage, such as an SD card. More advanced applications may even run edge software that requires a Windows platform with higher CPU power and memory specifications. Consequently, CPU, memory, storage, and power budget requirements may also determine whether you choose an Arm-based or Intel-based edge computer with wireless connectivity for the IIoT gateway.
5. Data and Hardware Reliability
Ensuring reliability for your data connection may require more than one wireless technology, such as using both Wi-Fi and LTE failovers. Although Wi-Fi access points (AP) almost always offer better reliability and cost savings than cellular connections, there is still a chance that Wi-Fi AP credentials may be mistakenly changed or the Wi-Fi network is accidentally disconnected. LTE solutions can provide an affordable backup since the cellular connection only activates when the Wi-Fi link is down.
Dual-SIM functionality can also provide redundancy and help ensure network availability by allowing you to install SIM cards from two different carriers on a single device. You can even split your entire network between two different carriers if you wish. Not being bound to a single carrier increases your bargaining power when negotiating the cost of your data plan and provides an additional backup in case one of the cellular connections goes down.
For both Wi-Fi and LTE connectivity in outdoor or harsh environments, it is important to choose IIoT gateways that work reliably in a wide operating temperature range, such as from -40 to 70°C (-40 to 158°F). IIoT gateways that satisfy rugged industrial certifications are ideal for outdoor field installations. Many are even available in small form factors for cabinets and provide various interfaces—such as RS-232/422/485, Modbus, I/O, and Ethernet—to connect adjacent equipment, PLCs, and other edge devices.
Example: EV Charging Station
Click image to enlarge
Figure 2. Car Charging Station Diagram
Growth in the plug-in electric vehicles (PEV) market is creating an opportunity for utility companies to deploy PEV charging infrastructure, which is essential for encouraging more drivers to switch to electric cars and expanding the PEV market in general. The PEV charging infrastructure consists of charging stations spread over a large area, which requires a fair amount of energy if they are used on a regular basis. Most charging stations are unmanned, and many are located in suburban areas, far away from centralized control rooms. With the increase in the number of charging stations, operators face multiple challenges in maintaining good network connections and centralized management of billing and maintenance.
In this real-life example, an EV charging station customer had requirements for low power consumption to maximize electrical output, reliable operation in outdoor environments, CAN port support to connect with energy management system, and an open platform for billing program development.
To meet these requirements, as shown in the diagram, a rugged Arm-based IIoT gateway with power consumption under 10 W and CAN port support was deployed in the system architecture, along with industrial Linux open platform software with RESTful APIs to enable easy integration with a user billing and monitoring dashboard.