Ever wondered how spectrum is allocated to different services? I recently came across the pie chart below showing allocation of spectrum between 108 and 6000 MHz for a “typical” European country. I decided to do a similar exercise for US spectrum allocation.
But first I like to give a brief overview of how spectrum is allocated. There are two organizations responsible for spectrum in the US: the National Telecommunications and Information Administration (NTIA) regulates spectrum use for federal users and the Federal Communication Commission (FCC) regulates spectrum use for non-federal users (including local and state governments). Spectrum bands can be designated for exclusive Federal users, or exclusively for non-federal users. But often, spectrum is shared between the two.
The FCC rules are stated in Title 47 of the U.S. Code of Federal Regulations. The frequency allocation table is detailed in Section 106 of Part 2 (or in short, 47 CFR 2.106). The table is unique to the United States and spans the range between 9 kHz and 275 GHz. There are 29 different services for non-federal users and 26 services for federal users. In addition, there are services used by the FCC that are not defined in Part 2 such as PCS (Personal Communications Services), ESMR (Enhanced Specialized Mobile Radio), and WCS (Wireless Communication Service) among other services. Most common wireless applications used today are below 100 GHz. The band below 6 GHz is of especial interest as many consumer devices and applications operate in it as shown in the table below.
|AM Radio||530 kHz – 1.7 MHz|
|Television||54 – 88, 174 – 216, 470 – 698 MHz|
|FM Radio||88 – 108 MHz|
|Cellular Phones||700, 800, 1700, 1900, 2100 MHz|
|Satellite Radio (Sirius XM)||2.3 GHz|
|WiFi & Bluetooth||2.4 GHz|
Spectrum is allocated for different services on a primary and secondary basis. A band can be allocated to multiple primary and secondary services that share the spectrum. Secondary services operate on the condition of non-interference with primary services. Sometimes, the secondary service has very large commercial popularity over the primary service as for example the 5 GHz unlicensed bands (WiFi). Because there are multiple uses of spectrum where different services are more popular or universal than others, categorizing spectrum for a snapshot view involves many judgment calls. I undertook such exercise with the result below. As I did this, I chose to allocate the entire band of spectrum to the dominant application or user and ignoring other uses that are less popular or commercially dominant. Therefore, while exclusive federal spectrum is about 13% of the total between 300 MHz and 6 GHz, the effective ownership is about 32%. It follows also that some applications of certain services would be under-represented. For example, the 3.65 non-exclusive licensed band is shared between fixed services and fixed satellite stations that are protected with an exclusion zone. In my classification, I assigned this band to fixed services rather than satellite. Another example: the 3.7-4.2 GHz band is heavily used by satellite services (C-band downlink) but also fixed services are co-primary. Fixed services are largely being migrated out of this band, so the dominant service is satellite. Alternatively, the 5925-6425 MHz band is where the uplink C-band satellite service operates and it is shared to a large extent with active fixed wireless deployments. I have assigned this band mainly to fixed service even though satellite service is just as popular.
One can see that generating a quick snapshot of spectrum allocation is not a straightforward matter and is highly subject to interpretation as it involves judgment calls for categorizing spectrum services. Such graphics have to be ‘taken with a grain of salt.’