What are licensed and unlicensed wireless frequency bands?
Licensed frequency bands are reliable and offer better performance than unlicensed frequency bands, which are low cost and easy to deploy but interference is common.
We are surrounded by wireless technologies more so now than ever before. Some wireless technologies come to mind...
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more easily because we tend to use them at a personal level, like Wi-Fi and cellular networks. But the concept of wireless encompasses an incredibly far-ranging landscape, from Bluetooth and broadcast technologies to military radars and satellite communications -- each landing in its own slice, or slices, of wireless spectrum, often referred to as bands.
In the United States, the Federal Communications Commission (FCC) sets rules that govern the use of radio spectrum and wireless bands, and similar agencies exist around the world. The general construct for bands is they are either licensed or unlicensed, but we're starting to see nuance to that delineation. It's worth considering some of the differences between licensed vs. unlicensed frequency bands and how the frequency management landscape is starting to evolve.
What are licensed bands?
Licensed bands ensure consistent performance and reduce interference concerns because individual companies or users pay a licensing fee for exclusive transmitting rights. To understand licensed bands further, let's go back to simpler times.
When broadcast radio and TV were new, specific bands were allotted for all stations to use. Within those bands, individual stations applied for licenses. What specific frequency channels they were allowed to use within a band were part of their license agreements, along with power output and areas of allowed coverage.
The license framework was, and still is, designed to make sure an FM radio station on 88.3 MHz has plenty of space between itself and any other stations on the same frequency, for example. Furthermore, no other technologies are allowed to use this licensed space, thus ensuring a fairly coordinated radio frequency landscape across the licensed bands.
Cellular networks are more modern examples of technology that rely on licensed bands, and there are also licensed point-to-point bridge systems, where two wireless endpoints can be joined together to form a link in spectrum that is uncluttered thanks to licensing. Bridges using the 80 GHz band are just one example.
Benefits of licensed frequency bands
Licensed bands offer two major advantages: reliability and performance. Each frequency is typically dedicated for a specific use. If another entity attempts to use radio equipment in the same band without authorization, legal remedies -- in the form of FCC enforcement and other actions -- are available.
Licensed bands allow users to manage performance more efficiently, enabling them to take advantage of lower noise levels and an environment where competition is limited.
What are unlicensed bands?
When comparing licensed and unlicensed frequency bands, unlicensed bands don't have the same rigid requirements that licensed bands do. At the same time, it's not quite a free-for-all. The FCC still defines maximum power levels allowed and other constraints that guide even the unlicensed bands. Organizations like the Wi-Fi Alliance and Bluetooth Special Interest Group help educate end users on benefits and proper use of common unlicensed frequencies.
One popular unlicensed band is the 2.4 GHz industrial, scientific and medical band. Here, you'll find Wi-Fi, Bluetooth, drone control signals, wireless microphones and hundreds of other technologies. Each one has the potential to make life miserable for the others to a certain degree through cochannel interference, but there are often -- but not always -- ways to carefully design these services so they can operate and coexist successfully.
Any product that will use an unlicensed band still needs to be type-approved by the FCC. This is how the manufacturer shows that a given product follows the rules. Consumers can then buy those products without being required to get their own licenses.
Benefits of unlicensed bands
Unlicensed bands offer low-cost access. They are free for anyone to use, provided users follow existing constraints limiting power levels and other operations. These bands give innovators and other entrepreneurs the opportunity to introduce new services and technologies more quickly than if they had to apply for permission to use licensed spectrum, which has become increasingly scarce.
Lightly licensed bands on the rise
Even as the FCC attempts to creatively reallocate what technologies are allowed in which band, regulators and industry alike are realizing there is only so much spectrum that can be used. Because of the endless thirst for more spectrum, we're seeing more use of so-called lightly licensed bands, such as 3.5 GHz, used by the new Citizens Broadband Radio Service (CBRS) systems.
These bands rely on internet-based databases to control what discrete channel a given component can use -- based on what other channels in that band that may be in use by other CBRS systems or from higher-priority users in the same space, such as Navy radars and satellite communications. This model is becoming a popular FCC-prescribed way to ensure coexistence with other users of the same bands, while opening those bands somewhat for new users.
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