ISM radio band
The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific and medical purposes, excluding applications in telecommunications.
Examples of applications for the use of radio frequency energy in these bands include RF heating, microwave ovens, and medical diathermy machines. The powerful emissions of these devices can create electromagnetic interference and disrupt radio communication using the same frequency, so these devices are limited to certain bands of frequencies. In general, communications equipment operating in ISM bands must tolerate any interference generated by ISM applications, and users have no regulatory protection from ISM device operation in these bands.
Despite the intent of the original allocations, in recent years the fastest-growing use of these bands has been for short-range, low-power wireless communications systems, since these bands are often approved for such devices, which can be used without a government license, as would otherwise be required for transmitters; ISM frequencies are often chosen for this purpose as they already must tolerate interference issues. Cordless phones, Bluetooth devices, near-field communication devices, garage door openers, baby monitors, and wireless computer networks may all use the ISM frequencies, although these low-power transmitters are not considered to be ISM devices.
In regulatory practice, many low-power unlicensed systems operate in or adjacent to ISM-designated ranges on a non-protection basis, meaning they must tolerate interference from authorized users and are not entitled to interference protection.
Definition
The ISM bands are defined by the ITU Radio Regulations in footnotes 5.138, 5.150, and 5.280 of the Radio Regulations. Individual countries' use of the bands designated in these sections may differ due to variations in national radio regulations. Because communication devices using the ISM bands must tolerate any interference from ISM equipment, unlicensed operations are typically permitted to use these bands, since unlicensed operation typically needs to be tolerant of interference from other devices anyway. The ISM bands share allocations with unlicensed and licensed operations; however, due to the high likelihood of harmful interference, licensed use of the bands is typically low. In the United States, uses of the ISM bands are governed by of the Federal Communications Commission rules, while Part 15 contains the rules for unlicensed communication devices, even those that share ISM frequencies. In Europe, the ETSI develops standards for the use of short-range devices, some of which operate in ISM bands. The use of the ISM bands is regulated by the national spectrum regulation authorities that are members of the CEPT.In the United States, ISM equipment is addressed under FCC Part 18, while many unlicensed communication devices that share spectrum with ISM allocations are regulated under Part 15; Part 15 devices operate under general conditions that include acceptance of interference and no entitlement to protection from interference.
Frequency allocations
The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations.In order to improve harmonisation in spectrum utilisation, the majority of service allocations stipulated in this document were incorporated in national tables of frequency allocations and utilisations which are within the responsibilities of the appropriate national administrations. The allocation might be primary, secondary, exclusive, or shared. Exclusive or shared utilization is within the responsibility of administrations.
Type A = frequency bands are designated for ISM applications. The use of these frequency bands for ISM applications shall be subject to special authorization by the administration concerned, in agreement with other administrations whose radiocommunication services might be affected. In applying this provision, administrations shall have due regard to the latest relevant ITU-R Recommendations.
Type B = frequency bands are also designated for ISM applications. Radiocommunication services operating within these bands must accept harmful interference which may be caused by these applications.
ITU RR, = In Germany, Austria, Bosnia and Herzegovina, Croatia, North Macedonia, Liechtenstein, Montenegro, Portugal, Serbia, Slovenia and Switzerland, the band 433.05–434.79 MHz is designated for ISM applications. Radio communication services of these countries operating within this band must accept harmful interference which may be caused by these applications.
History
The ISM bands were first established at the International Telecommunications Conference of the ITU in Atlantic City, 1947. The American delegation specifically proposed several bands, including the now commonplace 2.4 GHz band, to accommodate the then nascent process of microwave heating; however, FCC annual reports of that time suggest that much preparation was done ahead of these presentations.The report of the August 9th 1947 meeting of the Allocation of Frequencies committee includes the remark:
"The delegate of the United States, referring to his request that the frequency 2450 Mc/s be allocated for I.S.M., indicated that there was in existence in the United States, and working on this frequency a diathermy machine and an electronic cooker, and that the latter might eventually be installed in transatlantic ships and airplanes. There was therefore some point in attempting to reach world agreement on this subject."
Radio frequencies in the ISM bands have been used for communication purposes, although such devices may experience interference from non-communication sources. In the United States, as early as 1958 Class D Citizens Band, a Part 95 service, was allocated to frequencies that are also allocated to ISM.
In the U.S., the FCC first made unlicensed spread spectrum available in the ISM bands in rules adopted on May 9, 1985. The FCC action was proposed by Michael Marcus of the FCC staff in 1980 and the subsequent regulatory action took five more years. It was part of a broader proposal to allow civil use of spread spectrum technology and was opposed at the time by mainstream equipment manufacturers and many radio system operators.
Many other countries later developed similar regulations, enabling use of this technology.
A major regulatory inflection point for non-ISM communications in these shared ranges was the FCC's decision to permit low-power, unlicensed spread-spectrum systems under Part 15 in several bands that overlap with internationally used ISM frequencies. Later FCC documents cite 1985 as the point when the Commission first made portions of the 2.4 GHz and 5.7–5.8 GHz ranges available for unlicensed use under Part 15, a change that preceded large-scale deployment of consumer and enterprise wireless networking technologies.
These developments reinforced the practical distinction highlighted elsewhere in the article: ISM allocations originated for non-telecommunications uses, but many communications systems were later permitted under national rules in the same frequency ranges, subject to interference-tolerance conditions for unlicensed operation.
Applications
Industrial, scientific and medical applications are – according to article 1.15 of the International Telecommunication Union's ITU Radio Regulations – defined as «Operation of equipment or appliances designed to generate and use locally radio frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications.»The original ISM specifications envisioned that the bands would be used primarily for noncommunication purposes, such as heating. The bands are still widely used for these purposes. For many people, the most commonly encountered ISM device is the home microwave oven operating at 2.45 GHz which uses microwaves to cook food. Industrial heating is another big application area; such as induction heating, microwave heat treating, plastic softening, and plastic welding processes. In medical settings, shortwave and microwave diathermy machines use radio waves in the ISM bands to apply deep heating to the body for relaxation and healing. More recently hyperthermia therapy uses microwaves to heat tissue to kill cancer cells.
However, as detailed below, the increasing congestion of the radio spectrum, the increasing sophistication of microelectronics, and the attraction of unlicensed use, has in recent decades led to an explosion of uses of these bands for short range communication systems for wireless devices, which are now by far the largest uses of these bands. These are sometimes called "non ISM" uses since they do not fall under the originally envisioned "industrial", "scientific", and "medical" application areas. One of the largest applications has been wireless networking. The IEEE 802.11 wireless networking protocols, the standards on which almost all wireless systems are based, use the ISM bands. Virtually all laptops, tablet computers, computer printers and cellphones now have 802.11 wireless modems using the 2.4 and 5.7 GHz ISM bands. Bluetooth is another networking technology using the 2.4 GHz band, which can be problematic given the probability of interference. Near-field communication devices such as proximity cards and contactless smart cards use the lower-frequency 13 and 27 MHz ISM bands. Other short-range devices using the ISM bands are: wireless microphones, baby monitors, garage door openers, wireless doorbells, keyless entry systems for vehicles, radio control channels for UAVs, wireless surveillance systems, RFID systems for merchandise, and wild animal tracking systems.
Some electrodeless lamp designs are ISM devices, which use RF emissions to excite fluorescent tubes. Sulfur lamps are commercially available plasma lamps, which use 2.45 GHz magnetrons to heat sulfur into a brightly glowing plasma.
Long-distance wireless power systems have been proposed and experimented with which would use high-power transmitters and rectennas, in lieu of overhead transmission lines and underground cables, to send power to remote locations. NASA has studied using microwave power transmission on 2.45 GHz to send energy collected by solar power satellites back to the ground.
Also in space applications, a helicon double-layer ion thruster is a prototype spacecraft propulsion engine which uses a 13.56 MHz transmission to break down and heat gas into plasma.