IoT Gateways vs IoT Modems – What’s the Difference?

IoT Gateways vs IoT Modems

By now, you have probably seen a wide array of IoT Gateways and IoT Modems in our growing catalog of products.  We don’t blame you if you are feeling a little confusion.  Further complicating the matter, you may also recall the introduction of a MQTT Gateway and a MQTT Modem.  So now it’s time for us to end the confusion and address the topic of IoT Modems and IoT Gateways head on.

Defining this terminology requires we step back and look at the objectives of each technology. In some applications you may need IoT gateways.  Other applications may need IoT modems. You may be surprised to learn that you might actually need both, depending on your IoT implementation strategy. Let’s start by defining these technologies from the viewpoint of NCD design engineers.

IoT Gateway Definition

IoT Sensor Sends Data to Gateway which Converts to Real-World Values and Sends to Microsoft Azure Amazon AWS Losant MQTT Broker Temboo Kosmos


Raw Data


Real-World Data

Cloud Platform

IoT Gateways are best defined as devices that receive wireless data from remote sensors, translate these data into meaningful real-world values, and communicate these data to popular cloud platforms such as Microsoft Azure, Amazon AWS, Losant, MQTT, and more.  The key component of IoT Gateways are their ability to translate data from raw sensor bytes into real-world values such as temperature, humidity, pressure, speed, duration, frequency, current, voltage, and other types of meaningful data.  As new IoT sensor types are introduced, IoT Gateways will require periodic firmware updates to include new translator profiles.

IoT Modem Definition

IoT Sensor Sends Data to Modem that Connects to Ethernet USB RS-485 Bluetooth and WiFi


Raw Data


Raw Data

Communication Technology

IoT Modems are best defined as devices that receive wireless data from remote sensors and forward these data to a different communications format, such as Bluetooth, TCP, Serial, RS-485, or other popular communication technology.  IoT modems simply transfer data bytes from one format to another format.  Unlike IoT Gateways, IoT Modems never require firmware updates as they are not capable of interpreting the data in any way.  Converting data types means all of the data parsing (interpretation of IoT sensor data) is performed at the software or server level rather than the hardware IoT gateway level.

Using IoT Modems as IoT Gateways

Because modems only translate data types, modems may be used as the hardware component of a custom IoT Gateway, provided software is utilized to translate the incoming data into real-world values.  IoT Modems are typically used in conjunction with Node-Red to provide an IoT Gateway solution with incredible power and flexibility.

Node-Red allows logical flow-building, so reactions and events may be generated based on actual sensor values.

*Example of Node-Red Flows

MQTT Gateways and MQTT Modems

MQTT Gateways and MQTT Modems are very similar to IoT Gateways and IoT Modems. An MQTT Gateway translates data from incoming sensors and posts the real-world data to the MQTT broker. An MQTT Modem only subscribes to a receive topic and publishes to a transmit topic. This means raw, uninterpreted IoT sensor data is simply published to the MQTT transmit topic.

In the case of NCD endNodes, data is received by the device by subscribing to the MQTT receive topic. Responses from endNode devices are published to the MQTT transmit topic. Again, only raw data bytes are published and subscribed to the MQTT broker when using MQTT Modems. Actual real-world data is communicated to a MQTT broker when using a MQTT Gateway.

MQTT Modem with Sensor

MQTT Modem Communicates Raw Sensor Data to MQTT Broker from IoT Sensor


Raw Data

MQTT Modem

Transmits Raw Data

MQTT Gateway with Sensor

IoT Sensor MQTT Gateway Converts Data from Sensors to Real-World Values


Raw Data

MQTT Gateway

Transmits Real-World Data

MQTT Gateway with endNodeTM Device

MQTT Gateway Relays Raw Data Between MQTT Broker and endNode IoT Sensor or Device

endNode Device

Transmits & Receives Raw Data

MQTT Modem

Transmits & Receives Raw Data