What are the ISM Bands, and What Are They Used For?

The Industrial, Scientific, and Medical (ISM) frequency bands are designated radio frequency bands as defined by the ITU Radio Regulations. These frequency bands were set aside for RF use for purposes other than telecommunications. Hence, using the ISM bands for telecommunications is possible, but telecommunications devices using these frequencies must be able to withstand the interference from other RF and microwave technologies, such as microwave ovens, RF heating, and other potentially electromagnetic interference (EMI) producing devices. Though the ITU determines the international band designations, individual countries exact ISM band frequencies may differ.

Key Takeaways 

• ISM bands are specific RF frequency ranges reserved by the International Telecommunication Union (ITU) primarily for industrial, scientific, and medical uses. Still, today, many wireless communication systems also operate in them.  

• Because ISM-band frequencies are license-free (in many jurisdictions) for low-power, short-range systems, they are widely used for technologies such as WiFi (2.4 GHz), Bluetooth, Zigbee, RFID, and NFC. 

• Using ISM bands for communications means devices must be designed to tolerate interference from other users (e.g., microwave ovens, RF heating systems) since the band is shared and not exclusively for telecom. 

• For system design in IoT, wireless, industrial automation, or consumer electronics, knowing the ISM bands helps with frequency planning, regulatory compliance, and interference mitigation.

Though originally set aside for non-communication purposes, many short range, low power, license-free, or unlicensed error-tolerant communications systems operate within the ISM-band. Of the most common uses outside of communications, are induction heating for industrial and home applications, microwave heating for industrial and home applications, and RF and microwave heating for medical purposes, such as diathermy, hyperthermia therapy, and RF/microwave ablation. Recently, there have also been radar systems developed that operate in the ISM bands, specifically the 2.4 GHz ISM band, due to the readily available and inexpensive wireless ICs available for these frequencies.

The most common everyday uses of the ISM bands are for low-power and short range telecommunications, such as WiFi, Bluetooth, Zigbee, wireless telephones, RFID, and NFC. Many in the US are familiar with the 2.4 GHz ISM band, as most WiFi and Bluetooth communications operate in these bands, though more recently, 5 GHz WiFi systems have become more available. There are also many common RFID and NFC systems that use 13.56 MHz in the 13.553 MHz to 13.567 MHz ISM band, and many credit cards, secure access, personnel identification, and wireless payment systems use these technologies.

Moreover, many of the latest smart home and hobbyist electronics use Zigbee technology in the 915 MHz and 2.4 GHz ISM bands for low-power and short range communications between devices. In the next few years, it is likely that 60 GHz WiFi (WiGig, known as IEEE 802.11ad), operating in the 60 GHz ISM band, will gain popularity for extremely high throughput device-to-device communication. Some examples of this application may be high definition, 4k, video streaming and extremely fast device-to-device wireless data transfers.

There have been many more modulation schemes and communications platforms targeted for the ISM bands emerging in the past few years than prior years. Some of the reasons for this could be the increased potential of The Internet of Things (IoT) and Industry 4.0 applications, which will likely rely on low-power and short range machine-type communications without users being directly involved. Examples of these new technologies include Thread, Z-wave, LoRa, and NB-IoT. Though future applications of ISM bands may include satellite communications, right now there are no available ISM bands available for current cubeSATs, nanoSATs, or other smallSATs.

FAQs (Frequently Asked Questions) 

Q1: What are ISM bands?
A: ISM bands are frequency ranges set aside by the ITU for industrial, scientific, and medical applications; however, they are also widely used for license-free wireless communication devices under regulated conditions.  

Q2: Why do many WiFi and Bluetooth systems use ISM bands?
A: Because these bands allow unlicensed operation for low-power wireless devices, making them ideal for short-range communication and mass-market adoption. 

Q3: Do ISM band devices need a licence?
A: In many regions, devices in ISM bands can operate under licence-exempt rules, but they must meet specific technical limits (e.g., power, duty cycle, spurious emissions) and tolerate interference from other users. 

Q4: What is a common example of the use of ISM bands?
A: The 2.4 GHz ISM band is used by WiFi 802.11 (b/g/n), Bluetooth, Zigbee, and many IoT sensors because the band is globally available (though regulations vary).  

Q5: Are there limitations when using ISM bands?
A: Yes, interference is often more prevalent because of many devices sharing the band; certain frequencies may have regulatory restrictions or regional differences; and high-power communication over ISM bands may be more challenging due to these constraints.