Radio Bands

The use of wireless devices is heavily regulated throughout the world. Each country has a government department responsible for deciding where and how wireless devices can be used, and in what parts of the radio spectrum. Most countries have allocated parts of the spectrum for open use, or “license-free” use. Other parts of the spectrum can only be used with permission or “license” for each individual application.

Most wireless products for short-range industrial and commercial applications use the license-free areas of the spectrum, to avoid the delay, cost and hassle of obtaining licenses. The license-free areas of the spectrum are also known as ISM bands – “Industrial, Scientific & Medical”. In many countries there are several ISM bands available, in different parts of the spectrum.

The radio spectrum is split into frequency “bands” and each band is split into frequency “channels”. The width of each channel is normally regulated.

The channel width dictates how fast data can be transmitted – the wider a channel, the higher the data rate.

The common frequency bands for industrial wireless applications are:

• 220 MHz band in China – licensed
• 433 MHz band in Europe and some other countries – license free
• 400 – 500 MHz – different parts are available in most parts of the world as licensed channels
• 869 MHz band in Europe – license free
• 915 MHz band in North and South America and some other countries – license free
• 2.4 GHz band allowed in most parts of the world – license free

Higher frequency bands are wider, so the channels in these bands are also wider, allowing higher wireless data rates. For example, licensed channels in the lower frequencies (150 – 500 MHz) are often regulated to 12.5 KHz, whereas channels in the license-free 2.4 GHz band can be hundreds of times wider.

However, for the same RF power, lower frequency gives greater operating distance. With wireless data, there is always a trade-off between distance and data rate. As radio frequency increases, the possible data rate increases, but operating distance decreases.