Brief on Frequency Dependent Conductivity In Metallic Wires/Traces

More on ISM Bands Around the World

More on ISM Bands Around the World

By: Peter McNeil

Though not likely the original intent of the creators of the industrial, scientific, and medical (ISM) radio frequency bands commonly accepted throughout the world, much of the modern ISM bands usage is now low-power wireless communications. A large portion of Internet-of-Things (IoT) technology is reliant on “unlicensed” but not “unregulated” ISM bands. This is an important distinction, especially for the future of IoT and wireless communications as these bands set aside for a wide range of use cases.

Given the pervasiveness of wireless telecommunications, it can be easy to forget that the ISM bands were created for applications like microwave heating and medical hyperthermia treatments. Since this is the case, wireless telecommunication devices must operate in such a way that doesn’t interfere with these applications but must also accept interference from these other use cases. This is why the ISM bands have transmit power limitations in band and also out-of-band transmitted energy limitations.

This allows for organizations to manufacture, market, and sell devices that operate in accordance with the ISM band regulations that are not additionally licensed or given explicit permission by regional regulatory agencies. However, many regulatory agencies do require some form of authorization, such as a Declaration of Conformity or certification procedure prior to deployment or marketing of a device. An example of this is the United States Federal Communication Commission (FCC) Part 18 regulations for ISM band rules and Part 15 for unlicensed communication devices that operate in ISM frequency ranges.

This is why there are strict limitations on the power transmitted by Wi-Fi and other low-power wireless devices operating in the 433 MHz, 915 MHz, 2.4 GHz, and 5 GHz ISM bands. This is also why the output power of transmitters for these devices can’t merely be increased to extend range or improve signal-to-noise ratio (SNR) and bit-err0r-rates (BER). In lieu of higher output power, ISM band devices are often designed to use communication and modulation schemes that enhance the robustness of communications and overcome power limitations, such as spread-spectrum communication and frequency-hopping techniques.

It is also important to note that not all ISM frequency ranges are available worldwide and many are subject to local acceptance. For instance, the 433 MHz ISM frequency range is accepted in ITU Region 1 but is otherwise not an ISM band available for Australia. In this case Australia issues a license for use of this band. Another example is the 915 MHz band, which is available in Region 2 only, but there are additional exceptions that limit the use of this band in some locations.

Though the ITU has each ISM frequency band with designated regions, each country provides its own rules and regulations for ISM band use. Canada has similar regulations to the United States FCC regulations. The United Kingdom uses provisions of the Wireless Telegraphy Act to regulate ISM band use. The European Telecommunications Standards Institute (ETSI) is the European agency responsible for regulation of ISM band operation and requires self-declaration from a manufacturer that their product satisfies all legal requirements set by a Directive.

Learn more about the ISM bands here:

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