Ism (Industrial Science and Medicine) frequency band is defined by ITU-r (ITU Radio Communication Department). This frequency band is mainly open to industry, science, medicine and three institutions. This is a free license and no authorization is required. It only needs to observe a certain transmission power (generally lower than 1W) and does not interfere with other frequency bands. Generally speaking, all countries in the world have reserved some wireless frequency bands for industrial, scientific research and microwave medical applications. ISM bands are not uniform in different countries. For example, in the United States, there are three frequency bands: 902-928 MHz, 2400-2484.5 MHz and 5725-5850 MHz, while in Europe, 900MHz is used for GSM communication. And 2.4GHz is the ISM frequency band shared by all countries. Therefore, wireless networks such as wireless local area network (IEEE 802.11b/IEEE 802.1g), Bluetooth and ZigBee can all work in the 2.4GHz band.
ISM frequency bands specified by ITU-R are as follows:
Frequency range center frequency availability
6.765–6.795 MHz 6.780 MHz
13.553–13.567 MHz 13.560 MHz
26.957–27.283 MHz 27. 120 MHz
40.66–40.70 MHz 40.68 MHz
433.05–434.79mhz 433.92mhz ITU area only 1.
Only applicable to 902–928mhz 915mhz ITU area 2.
2.400–2.500 GHz 2.450 GHz
5.725 to 5.875 GHz 5.800 GHz
24–24.25 GHz 24. 125 GHz
6 1–6 1.5 GHz 6 1.25 GHz
122– 123 GHz 122.5 GHz
In fact, the regulation of frequency band management of wireless products is not perfect. Among them, 2.4G is an unlicensed frequency band in different countries, and the following are other different free frequency bands:
L north America: 3 15MHZ and 9 15MHZ, 902~928MHZ.
L EU: 433MHZ and 868MHZ, and some other frequency bands in Japan and Australia.
At present, 800M and 900M frequency bands have been occupied by GSM cellular mobile networks in China, and most products work at about 433MHZ. 3 15M frequency band is the main frequency band of early wireless remote control products, so the wireless electromagnetic environment in this section is quite complicated and the wireless data transmission is unreliable. At present, the 433M frequency band is becoming more and more complicated, because many new car remote controllers are gradually using this frequency band. So these two frequency bands are more used for wireless remote control to transmit simple data. In view of the measurement data collection of utilities such as water, electricity and gas, the national radio management department has issued two application-free wireless measurement frequency bands (470-5 10M), which are specially used for wireless data transmission of civil metering equipment.