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IoT & M2M Iridium

December 14, 2022

Introducing Iridium Messaging Transport (IMT)

Taking full advantage of IMT, the latest Iridium network service evolution, Ground Control is proud to announce the development of a new Satellite IoT delivery network. This ultra-efficient solution is designed to meet the needs of IoT applications that require transmission of larger data payloads from very remote locations.

What is Iridium Messaging Transport (IMT)?

The new IMT service from Iridium is designed for IoT / M2M applications, and joins several other satellite airtime services in this space. So what makes IMT different?

Table explaining differences between IoT satellite services

This table compares these satellite services to each other, not to the broader ecosystem of connectivity options.

Message Based vs IP Based

The simplest distinction between these two means of communication is that message-based services send discrete data packets at intervals determined by the owner / operator; IP-based services can send and receive data continuously. An advantage of IP-based connections is that many, particularly legacy, applications, use TCP/IP protocols, and so data can pass seamlessly between different systems. The major benefit of utilising message-based connections is that they are far lower cost, because you’re only billed for the data payload and not for any communication overhead (e.g. TCP).

Connection Speeds

Iridium already has a message-based airtime service called Short Burst Data, or SBD; Inmarsat has a similar service called IDP (IsatData Pro). Both are designed for very small amounts of data: environmental monitoring and asset tracking for example.

Iridium introduced Certus 100 which offers the ability to send more data, more frequently, and is ideal for legacy installations and telemetry streaming applications.

IMT sits in between these two services; with the ability to send 100 KB per message, far more data can be transmitted than via the SBD or IDP services, but because it’s message-based, it remains a lower cost solution than Certus 100.

Total Cost of Ownership

IMT airtime is more expensive than SBD airtime, but lower cost than Certus 100 airtime because you’re charged for the data payload only. We would recommend IMT is leveraged in mission-critical use cases, where the value of receiving the data far outweighs the cost of retrieving it.

Power Usage

A device leveraging the IMT service will generally use less power than a device using Certus 100, because the data is sent and received on demand, and data packets can be optimised. However, simply because the message can be up to 100 KB – that’s enough to send compressed images – an IMT-enabled device will use more power than an SBD or IDP equivalent. Battery and solar power is an option, but mains power is preferred.

Which Devices Utilise IMT?

At this time, there are very few devices that can access the IMT service; Ground Control’s RockREMOTE and RockREMOTE Rugged are two of them. With the RockREMOTE you can use a combination of connectivity options: Certus 100, LTE-M, and/or IMT. Users configure the device to use the airtime that is most economical for their particular use case; Ground Control will consult and assist with this exercise if needed.

When Would You Use IMT?

Iridium SBD
Inmarsat IDP
Iridium IMT
Iridium Certus 100
Inmarsat BGAN M2M
Great For:
Very small amounts of data from individual sensors
Very small amounts of data from individual sensors
IoT applications with larger data transmission requirements Sensors already ‘speaking’ MQTT
Fixed or mobile IoT applications which require IP connection
Fixed IoT applications with larger amounts of data to transfer via an IP connection
Small amounts of telemetry data
Small amounts of telemetry data
Larger amounts of telemetry data; compressed images
Connected M2M protocols e.g. Modbus RTU, WITS DPN3
Connected M2M protocols e.g. Modbus RTU, WITS DPN3
Use Cases:
SCADA, Agritech, Basic asset tracking
SCADA, Agritech, Basic asset tracking
Remote camera traps preventing poaching / trespassing; Remote surveillance capabilities for on-the-move assets
Visibility and control of assets spread over a wide area; Extending the reach of telemetry applications
Visibility and control of assets spread over a wide area; Extending the reach of telemetry applications

How does Ground Control’s new satellite IoT delivery network work?

The IoT delivery network is designed to deliver large message payloads for a wide range of IoT applications in a highly cost effective way. It leverages the new IMT satellite service, the RockREMOTE terminal, and the MQTT messaging transport.

It provides an end-to-end solution comprised of:

  1. An MQTT application deployed on the RockREMOTE terminal; this provides the interface for your remote application to submit and receive data payloads
  2. The Iridium IMT satellite service
  3. An MQTT server application, delivered via Ground Control’s Cloudloop platform, which enables your IoT service application to submit and receive data payloads.

A 2021 research paper found that 75% of businesses experienced connectivity challenges when trialing IoT projects (source), ranging from coverage to interoperability to cost. Ground Control’s IoT Gateway is designed to address each of these challenges, providing global coverage, industry standard interfaces, and cost efficiency.

From remote monitoring to predictive maintenance, improved processes to sustainability, the value of IoT data collection is under no doubt. The new satellite IoT delivery network allows Ground Control’s customers to grow beyond the restrictions of current IoT projects, delivering greater depth and breadth of data insight.

What is MQTT?

MQTT is a messaging protocol – a structured way for applications to exchange payloads of data between applications – designed for IoT. TCP / IP is another messaging (or communication) protocol, used to connect network devices on the internet, and in private computer networks.

MQTT was designed specifically for IoT, where the data transmission requirements are usually small, and the microcontrollers that host the code are also very small (physically and in terms of the amount of instructions they can support). So MQTT is very lightweight and efficient.

Another advantage of MQTT is that it has small message headers; this is the initial portion of a data packet, and contains control information such as addressing and version. In IP messaging protocols this is (relatively speaking) quite a large amount of information which makes sending data via IP more resource intensive. MQTT’s small message headers ensure that the network bandwidth is optimised.

It has become the industry standard for newer IoT projects because of its many advantages, including reliable message delivery, security, and scalability.

For more information on MQTT, visit

Talk to us about IMT

If you have an IoT connectivity challenge which satellite can solve, and you'd like expert, impartial advice on the best airtime and delivery network for your requirements, email or call us, or complete the form.

We've been delivering satellite and cellular connectivity services for over 20 years, and our partnerships with leading satellite operators means we can offer great pricing and a robust, reliable service, in addition to our commitment to delivering innovative, customer-driven data and device management solutions.