Spectrum: What Is It? Why Does It Matter?
Webster defines spectrum as follows, “The entire range of wavelengths or frequencies of electromagnetic radiation extending from gamma rays to the longest radio waves and including visible light.”
Electromagnetic radiation is the magic that allows all of our portable devices to communicate without wires, toy radio-controlled cars, cordless phones, wireless microphones, over the air television, AM/FM radio, satellite radio, satellite TV, WiFi, Bluetooth, cell phones, etc., etc., etc. They all use electromagnetic radiation. We generally carve up the entire electromagnetic radiation spectrum into chunks, called bands, when talking about them. Bands are further divided into channels.
The terms “band” and “channel” should be familiar to you. Perhaps you recall an old radio that had a “band” selector that let you choose between “FM” and “AM,” or perhaps even other bands, like shortwave. Perhaps you recall the ’70s with the CB (citizens band) radio craze. Channel is also a familiar term with “television channel” still being commonly used.
WiFi networks operate in the 2.4 GHz band or the 5 GHz band. Within each of those bands, channels are defined.
The United States radio spectrum allocation chart is fascinating to view.
Radio Frequency Spectrum is by its very nature a shared public resource. The radio waves moving through the air, and space, do not pay any attention to property line boundaries. They do attenuate over distance and can be blocked by some objects. Two transmitters on the same frequency, in the same area, transmitting at the same time usually results in interference. Interference usually means that neither signal made it to the receiver as intended. The Federal Communications Commission (FCC) is responsible for making the rules in the United States to allow this spectrum to be used most effectively.
All this matters because in order to communicate wirelessly, you need available spectrum that is protected from interference. Wireless communications are everywhere and we depend on them operating reliably.
In 1963, the FCC allocated 20 microwave channels, 6 MHz each, in the 2.5 GHz spectrum for use by educational institutions. They were to be used for one-way television transmission of educational content. This service was called Instructional Television Fixed Service (ITFS). Later, the FCC permitted leasing of excess spectrum by the educational institution to other parties. In 1998, the FCC modified the rules for spectrum use so that 2-way cellular transmission was permitted in this spectrum.
The 2-way transmission and leasing options resulted in much of the spectrum being used commercially, with the commercial providers paying the educational institutions for the spectrum that was assigned to them at no charge by the FCC.
In 1995 the FCC stopped issuing new EBS licenses. Data transmission has changed significantly since 1995. Long Term Evolution (LTE), aka 4G, cellular transmission is now readily available in much of the United States. Building private LTE networks is now very economical, as equipment has become commoditized. Unfortunately, having the equipment does nothing if there is no available spectrum in which to operate it.
Some schools and libraries make WiFi available to students after hours. Generally, the students need to be in the parking lot in order to access that signal. LTE signals reach much further from an antenna that WiFi signals. It is able to extend that coverage area to a few miles from the building, instead of a few hundred feet that is typical for WiFi.
School buildings and libraries are generally constructed in the communities that they serve. Being able to offer Internet access to students that live within a few miles of a school or library could go a long way to help close the homework gap. The build-it-yourself approach allows the school to provide the same network experience to students when they are on campus or at home. This might include content filtering, direct access to school resources, IP address management, authentication, etc.
The FCC is poised to change the rules for EBS again. One option they are considering is to auction the spectrum to the highest bidder. That would essentially eliminate “Educational” from EBS and it would become just another band that is used by the highest bidder. Since EBS is the only band allocated specifically for education, it would be a shame to see it disappear.
Stay tuned, the FCC will probably be announcing more on this topic in the near future.
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