Unlicensed (ISM – Industrial, Scientific, Medical) bands are allocated worldwide for data exchange. The ISM band is the part of the radio frequency spectrum for general use that can be utilized without licensing. The only requirement for products developed for the ISM band is compliance with the regulations set by the governing authorities for that part of the frequency spectrum. These rules differ from country to country. In the United States, the Federal Communications Commission (FCC) sets the standards, while in Europe, it is the European Telecommunications Standards Institute (ETSI).
In Russia, based on the decisions of the State Commission for Radio Frequencies (SCRF) No. 08-24-01-001 dated 28.04.2008 and No. 07-20-03-001 dated 07.05.2007, the frequency bands LPD 433.075 - 434.750 MHz, PMR 446.00625 - 446.09375 MHz, and 868.7-869.2 MHz are allocated for these purposes. These radio frequencies can be used without obtaining a special permit from the SCRF and completely free of charge, provided that the requirements for bandwidth, transmitted power (up to 10 mW near 434 MHz, up to 500 mW near 446 MHz, and up to 25 mW near 868 MHz), and the intended purpose of the radio transmitting device are met.
Devices designed to operate in the ISM band are characterized by low power consumption and low data transmission rates. However, in recent times, the data rates of new versions of standards within this band have shown a tendency to increase.
The most commonly used ISM frequency bands are 2.4 GHz and sub-gigahertz frequencies. Due to heavy congestion in the 2.4 GHz band, there has been a shift toward the 5 GHz band in recent years. While the 2.4 GHz band is a universal frequency range, sub-gigahertz bands intended for low-power wireless applications differ across countries. In the United States, the most popular range remains 902–928 MHz, while in Europe, the highest activity is observed in the 868 MHz range.
Various wireless systems such as Bluetooth, Wi-Fi, 802.15.4, Zigbee, and microwave ovens operate in the 2.4 GHz frequency range.
Other license-free frequency bands: LPD, PMR, CB frequency band