An Introduction to IoT Radio Communications

16 Jan 2026 - by Archie Hilton

Radio communications are often seen as a “black art”, though in reality the fundamental concepts are very approachable. This article gives you the basics that will enable informed decision-making in your next IoT project.

What is Radio?

Radio waves are a form of light which is invisible to our eyes. Light has amplitude, wavelength, and frequency¹ measured in Hertz (Hz, cycles per second) which is directly tied to wavelength. Longer wavelengths mean lower frequencies[^2]. This is a classical simplification meant to provide an intuitive interpretation, and while strictly correct, it suffices.

With visible light, amplitude corresponds to brightness and wavelength determines the colour. With radio, amplitude is signal strength and the wavelength/frequency operate as different communication channels.

We communicate with radio waves due to their efficient energy use and their ability to travel long distances and penetrate buildings.

Radio wave frequency matters; Low Frequency (LF) radio behaves very differently to Ultra-High Frequency Radio (UHF), where IoT most devices operate. At higher frequencies like 2.4GHz (commonly used for Wi-Fi), radio behaves similarly to visible light. It reflects off of surfaces, scatters around and is more sensitive to obstructions like brick walls and metal. Unlike visible light however, some materials like wood and plasterboard are partially transparent, which is why Wi-Fi can propagate through a house.

Materials affect sound and radio waves similarly. Imagine someone playing the drums in your living room and listening to them in various places:

• The living room: Very loud, cymbals are harsh and the snare is snappy, lots of high frequencies.
• The hallway: Less harsh but still loud. More echo.
• The upstairs bedroom: Loud but very muffled.
• Next door: Audible low frequency rumble of the toms.
• Down the street: Nothing at all.

The principle is the same in radio; lower frequencies can penetrate materials better and travel further, while high frequencies tend to fall off earlier. Much like sound, radio reflects and penetrates materials.

We use high-frequency radio despite the range limitations because information can be transmitted faster with better reliability given a good signal. The reason why this is true is beyond the scope of this article, though keen readers may want to look into Shannon’s Limit and, once sufficiently excited about information theory and how it applies to radio, study for their Foundation Amateur Radio License.

Radio Bands

A radio “band” is a range of frequencies allocated to a specific purpose. Common in IoT is the 2.4GHz ISM (Industrial, Scientific and Medical) band, regulated by the ITU and generally accepted worldwide.

Originally, ISM bands were created for devices which emit radio-frequency noise during operation, but when communication standards like Wi-Fi, Zigbee and Bluetooth came into existence they adopted these bands due to the convenient regulatory requirements. This meant, of course, that they had to tolerate interference from noisy equipment and each other.

There are other ISM bands like 902-908MHz (Americas only) and non-ISM bands like the ETSI 300.220 863-869MHz range in Europe which offer similar low regulatory requirements. While data throughput is slower at these frequencies, the improved propagation results in remarkable transmission distances.

The main advantage of the 2.4GHz band is that it’s agreed upon virtually worldwide, meaning that there are few regional differences to worry about. Sub-GHz bands like 902-908MHz and 863-869MHz only apply to certain countries and carry with them local regional regulations.

As an example, 863-869MHz is actually split up into several independent bands with their own power requirements and “duty cycle” requirements (where you’re only permitted to be transmitting a certain fraction of any given time). The “N” band (868.700-869.200MHz) has a 0.1% duty cycle limitation, enforced in a one-hour rolling window. This means your transmission time in the last hour must never exceed 3.6 seconds.

Radio Standards

Radio standards define how devices communicate with each other using radio. They define the bands used, the channels, communication method, and more.

One of the more common standards is 2.4GHz Wi-Fi, also referred to by its official name, IEEE 802.11. There are multiple amendments to the standard, with some examples being 802.11n and 802.11ax. You may also be familiar with Bluetooth, another 2.4GHz standard.

Each standard warrants its own article entirely and comes with their own strengths and weaknesses. For example, Wi-Fi is perfect for internet-connected IoT devices like Amazon Alexa, whereas Zigbee offers significant battery life savings for simpler devices that can operate at the slower data speeds. Sub-GHz standards like LoRa take advantage of the longer distance travel at the expense of lower data rates to achieve multi-kilometer transmit distances with very little power, making it ideal for deployed sensors. Technologies like LoRaWAN build on top of LoRa, standardising things like authentication and data format.

Where to Learn More

In the coming weeks, we’ll cover the most common radio standards used in IoT and explore how their characteristics influence real-world design choices. We’ll look at practical considerations around range, data rate, power consumption, reliability, and how these influence everything from device architecture to deployment strategy.