RF, Microware and Optical Frequency Communications – A Review of Technologies
4. Frequencies used for communications
1. Terrestrial Communication Frequencies: There are many bands of frequencies used for terrestrial (ground-based) communication by civilians. Some of the commonly used bands are:
Very Low Frequency (VLF): 3 kHz to 30 kHz
Low Frequency (LF): 30 kHz to 300 kHz
Medium Frequency (MF): 300 kHz to 3 MHz
High Frequency (HF): 3 MHz to 30 MHz
Very High Frequency (VHF): 30 MHz to 300 MHz
Ultra High Frequency (UHF): 300 MHz to 3 GHz
These bands are used for various types of communication, such as AM and FM radio broadcasting, TV broadcasting, two-way radios, cell phone networks, and Wi-Fi.
2. Satellite Communication Frequencies: Satellites also use a range of frequencies for communication, including:
L-band: 1 GHz to 2 GHz
S-band: 2 GHz to 4 GHz
C-band: 4 GHz to 8 GHz
X-band: 8 GHz to 12 GHz
Ku-band: 12 GHz to 18 GHz
Ka-band: 26.5 GHz to 40 GHz
These frequencies are used for various types of satellite communication, such as satellite TV, satellite phone networks, and satellite internet.
3. Fiber optic communication typically uses light in the near-infrared range of the electromagnetic spectrum, with wavelengths in the range of 800 nanometers (nm) to 1600 nm. These wavelengths correspond to frequencies in the range of about 190 THz to 380 THz.
The allocation of these frequencies is regulated by government agencies, such as the Federal Communications Commission (FCC) in the United States and the International Telecommunication Union (ITU) internationally, to avoid interference between different communication systems.
Note: Cellular backhaul networks typically use microwave frequencies in the range of 6 GHz to 38 GHz, and sometimes higher frequencies in the E-band (60 GHz to 90 GHz) or V-band (57 GHz to 71 GHz). These networks are typically considered part of the terrestrial communication infrastructure, as they involve wireless links between cellular base stations and core networks over a land-based infrastructure.
Microwave backhaul networks can be used to connect remote cell sites to central switching offices or data centers, or to provide high-speed data connections between other types of communication networks. They are commonly used in urban and suburban areas, where it may not be feasible to install fiber-optic cables for backhaul.
The use of microwave backhaul for cellular networks has been growing in recent years, as mobile data traffic continues to increase and demand for high-speed connectivity grows.
5. Free to use (open) frequencies in terrestrial frequencies
There are some free to use frequencies in the terrestrial communication bands that can be used by anyone without a license. These frequencies are called the "ISM bands" (Industrial, Scientific and Medical bands) and they are available for use in many countries around the world.
The ISM bands are typically used for low-power, short-range communication, and for industrial, scientific and medical applications such as microwave ovens, RFID tags, and wireless medical devices. The frequencies allocated to the ISM bands vary depending on the region, but they are typically in the range of 900 MHz to 2.4 GHz and 5.725 GHz to 5.875 GHz.
In addition to the ISM bands, there are some other frequencies that are free to use for certain types of communication, such as citizen's band (CB) radio in the HF band, and the Family Radio Service (FRS) and General Mobile Radio Service (GMRS) in the UHF band, in the United States. However, the use of these frequencies may be subject to certain restrictions, such as power limits and antenna height limitations.
It's important to note that even though some frequencies may be free to use without a license, it's still important to follow regulations and guidelines to ensure that your communication does not interfere with other communication systems.
