Benefits and Applications of MQTT in SCADA for Reliable Data Exchange

We’re at a time where you need multiple Industrial IoT (Internet of Things) devices—more than you can count on your fingers—to efficiently run a plant.

The thing is, many of those IoT devices have both limited processing power and network bandwidth. This represents a challenge for SCADA (Supervisory Control and Data Acquisition) systems where the goal is to gather and exchange information between devices.

Fortunately, MQTT (Message Queuing Telemetry Transport) arose as a solution. In this article you will learn more about how MQTT can be used with SCADA systems, its key components, benefits, and applications.

What is MQTT and How Does it Connect with SCADA Systems?

MQTT is a messaging protocol used to facilitate the exchange of data between devices and applications. It stands out in environments where devices have limited processing power, network bandwidth, and low internal memory.   

The gist of connecting MQTT with SCADA systems comes from seeking a reliable and efficient way for data exchange. SCADA systems play a pivotal role in monitoring and controlling industrial processes in real-time. But this can’t be done when there’s no communication between devices. MQTT enhances the capabilities of SCADA systems, making them even more powerful for industrial automation.

Figure 1: Diagram of where MQTT fits into a SCADA system

How Does MQTT Work?

MQTT uses a publish/subscribe architecture, a messaging pattern in which senders (publishers) and receivers (subcribers) aren’t linked. They communicate through what you would call a “middleman” (broker) for the data exchange.

Here are the key components of MQTT explained:

• Publishers: A client (device or application) that send messages to specific topics on the broker. It publishes information subscribers might be interested in.
• Subscribers: A client that subscribes to specific topics and gets messages related to those topics.
• Broker: It’s the intermediary of messages from publishers to subscribers. It manages the topics ensuring messages end-up in the right place.
• Topic: A topic is like a channel where messages are published and subscribed from. There are different topics which also means multiple channels.
• QoS (Quality of Service): You can choose the level of assurance you prefer when delivering a message. It can be QoS 0 (at most once), QoS 1 (at least once), and QoS 2 (exactly once).
• Last Will and Testament (LWT): As dramatic as this one sounds, it just means that a specific message will be sent to everyone else if you suddenly go offline.
• Retained messages: The broker can retain the last message sent on a topic.

Here’s a step-by-step breakdown of how the publish/subscribe process works:

1. Publisher sends a message and labels a topic
2. Broker receives the message and identifies the topic
3. Broker recognizes the subscribers that have interest in the topic
4. Broker sends message to subscribers
5. Subscribers receive the message and take action

The fact that publishers and subscribers don’t need to be linked together (or are unaware of each other’s existence) allows this architecture to be flexible and scalable. Collecting data from SCADA using MQTT is easier than using traditional industrial protocol and devices can be added or removed without affecting the overall system.

5 Benefits of MQTT in SCADA Systems

Using MQTT in SCADA systems offers multiple benefits. Here are some key advantages.

#1. Efficient Data Transmission and Reliable Communication

The MQTT protocol is designed to minimize messages, meaning it doesn’t add unnecessary data. This makes MQTT ideal for limited technological resources while keeping a streamlined communication.

Besides, the QoS feature guarantees the delivery of critical information even in less-than-ideal network conditions. This ensures reliable communication which enhances efficiency.

#2. Low Bandwidth Consumption

MQTT excels at low bandwidth consumption by using a binary format for messages. This reduces the amount of data transmitted over the network. It also reduces latency as it minimizes the time required for a message to travel from publisher to the broker and lastly the subscriber.

#3. Simplified Integration with IoT Devices

MQTT is a standardized protocol for communication. This makes integration with multiple IoT devices and sensors an easy task—regardless of the brand and model.  

The simplified integration with IoT devices allows for a highly scalable system. You can add or remove as many IoT devices as you want from your network without altering the existing infrastructure of your SCADA system. 

#4. Improved Battery Life for IoT Devices

MQTT is called the lightweight protocol because it minimizes messages and sends them “lightweight”. The efficient handling of messages contributes to reduced energy consumption for IoT devices. As a result, these devices can operate for longer periods on a single charge.

This sole benefit makes MQTT an excellent choice for battery-powered sensors and devices.

#5. Enhanced Security

You can use secure protocols like MQTT over TLS/SSL to encrypt data in transit. Any information shared between devices and the broker is kept confidential and secure. In cases where there’s a lost connection or the network connection isn’t stable, MQTT queues messages and makes sure they’re delivered once the connection is reestablished.

Applications of MQTT in SCADA Systems

The benefits that we just addressed open up a wide range of applications for using MQTT in SCADA systems.

Here’s a list of some applications:

• Remote Monitoring and Control: SCADA systems integrated with MQTT facilitate the management of operations from a central location. Operators can monitor production lines without being physically present at the plant.
• Predictive Maintenance: By using MQTT to transmit data to the SCADA system, you can monitor your machinery in real-time.
• Environmental Monitoring: Industries such as wastewater, which measure critical parameters like pH levels and flow rates, can use MQTT to monitor these variables and ensure compliance with environmental standards.
• Supply Chain and Logistics: MQTT has applications in industries where delivery to distribution centers is essential. In a modern warehouse, MQTT can help different inventory management systems communicate, optimizing the overall logistics.
• Energy Management: MQTT can collect and transmit data from energy meters to the SCADA system for monitoring and optimization of energy utilization.
• IoT and IIoT Integration: MQTT is a communication protocol widely used in IoT for its easy integration. This integration enhances data collection and analysis which is one of the main advantages of using IoT for industrial automation.

Wrapping Up: Key Takeaways on MQTT

There has been a long discussion about SCADA vs. IIoT in which experts have concluded that SCADA and IIoT can work together to bring enhanced industrial automation. Now, integrating MQTT with SCADA brings this idea a step forward.

The more we embrace these trends, the smarter, more efficient, and more agile industrial automation becomes. We’ll get to a point where predictive analytics and enhanced security aren’t just options but more like new standards for the Industry 4.0 era.