SMS (Short Messaging Service) is widely used in the context of cellular IoT for data transmission, status updates or remote device control. The main benefits of SMS communication are simplicity, widespread network availability, and a relatively low-cost solution for specific types of data transfer. Devices in areas that are remote or have insufficient coverage, SMS is used as a backup transmission tool when other network technologies, such as 3G/4G LTE or NB-IoT, are offline.
To understand SMS in the context of IoT, it is important to distinguish between SMS MO (Mobile Originated) and MT (Mobile Terminated).
What is SMS MO?
SMS MO refers to when a device sends an SMS to another device. In other words, the SMS originated from the IoT device. SMS MO messages are often used for notifications and alerts, status updates or to transmit data when internet connectivity is unavailable.
Example: A smart meter for energy consumption sending a usage report to the server of the utility company.
What is SMS MT?
SMS MT refers to a message being received by a device from an external sender. In other words, the message terminates in the IoT device. In IoT deployments, the ‘external sender’ is usually the company’s server or SMS gateway. SMS MT is often used for sending device commands, requesting updates or configuring devices.
Example: The server sends an SMS to a vending machine to update its pricing configurations.
What are the main differences?
| SMS MO | SMS MT | |
|---|---|---|
| Direction of Communication | Outgoing, initiated by the IoT device to transmit data or alerts. | Incoming, initiated by an external sender to the IoT device for commands or configuration. |
| Usage Scenarios | Commonly used in reporting and sending alerts from IoT devices. | Useful for sending commands to control or manage IoT devices remotely. |
| Billing | Charges typically apply to the sender (the IoT device’s SIM card). | Charges generally apply to the sender. So, it is typically free of charge for the receiving device. |
| Reliability in IoT Environments | Offers reliability when other communication methods are unavailable. | Offers reliability when other communication methods are unavailable. |
Conclusion:
SMS MO and SMS MT are essential tools in the cellular IoT. They enable flexible and reliable communication, especially in use cases where internet availability is limited.
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