How Do IoT Devices Connect to One Another?

• An IoT device
• A wireless link
• A cloud service

What you will learn

• Name the main ways an IoT device can connect to others.
• Describe how a device sends its data to the cloud.
• Explain what a gateway does and why one is sometimes needed.

Before you start

You should know in a few words what the Internet of Things is, as covered in the previous article.

Which technologies link IoT devices?

To send data to the cloud, an IoT device needs a path connected to the internet. IBM lists Wi-Fi, Bluetooth, cellular, Zigbee and LoRaWAN among the connectivity technologies used in IoT.

Think of connections as different roads. Besides the wireless examples above, links can use a cable; each is used where it fits. A protocol is a set of agreed rules for sending messages along such a road.

The IETF notes that most smart object deployments can use the Internet protocol suite that is already standardized. So a small sensor can often speak the same basic language as a laptop.

• A device
• A radio link
• A wired link
• A cellular mast

Can two devices talk to each other directly?

Yes. Sometimes two devices made by different manufacturers are meant to communicate directly, as with a light switch and a light bulb. The IETF calls this the device-to-device pattern.

For this to work out of the box, the manufacturers need to agree on the protocol stack, the set of protocols the devices use together. This is one part of compatibility: RFC 7452 also points to decisions about information and data models, authentication, security and privacy.

Agreement is not always there. IBM says that IoT devices from different manufacturers often use different standards and protocols, which makes machine-to-machine communication hard.

• A light switch
• A light bulb
• A direct link

How does a device reach the cloud?

A common way is to upload sensor data to an application service provider. The IETF calls this the device-to-cloud pattern.

The network a device uses is typically not controlled by the provider. RFC 7452 lists WLAN, wired Ethernet and cellular radio among the access technologies that are reused. Ethernet uses a cable; WLAN and cellular use radio.

This pattern may lead to silos: data kept apart and harder to combine with information from elsewhere. The IETF says device-to-cloud communication may lead to this situation; a provider may also let third-party devices connect to its server infrastructure.

• A first device with a sensor
• A second device with a sensor
• An application service provider

What does a gateway do?

A gateway connects different technologies and can also perform networking and security functions. The IETF says one has to be added to the communication architecture in some cases, such as when interoperability with legacy non-IP devices is needed.

A second IETF document describes a common setup. Resource-constrained smart objects are connected to the Internet via a gateway that is directly reachable. The gateway does the work of reaching the wider network, so the small device does not have to.

• Small devices
• A gateway
• A cloud service

Real-world example

Try this with an adult. Look around your home for objects that talk to a network, such as a phone, a speaker or a light with an app. For each one, guess which way it connects: directly to another device, to a cloud service, or through a gateway. Write your guesses down. Then check the manual or the app settings together.

Common misunderstandings

All IoT devices use the same connection. IBM lists several connectivity technologies, and the IETF describes several patterns, so devices differ.

Every device talks straight to the cloud. Devices can also talk to each other, and a gateway can sit between a device and the network.

Devices from different makers always understand each other. IBM notes that they often use different standards and protocols.

Frequently asked questions

Do IoT devices need Wi-Fi?

No single technology is required. IBM lists Wi-Fi, Bluetooth, cellular, Zigbee and LoRaWAN, and the IETF also mentions wired Ethernet.

What is the difference between device-to-cloud and device-to-gateway?

In device-to-cloud, a device uploads data to an application service provider. In device-to-gateway, a gateway bridges between different technologies.

Why can my smart devices from different brands not work together?

Devices from different manufacturers often use different standards and protocols. Agreeing on a protocol stack is one part; manufacturers also need to consider information and data models, authentication, security and privacy.

Summary

• IoT devices connect with technologies such as Wi-Fi, Bluetooth, cellular, Zigbee and LoRaWAN.
• Devices can communicate directly, upload sensor data to a service provider, or use a gateway that bridges technologies.
• For devices from different manufacturers to communicate out of the box, agreeing on a protocol stack is one part; information models, security and other choices can matter too.