To Share or Not to Share? A Primer on the Important Question of the Spectrum

In a previous life I worked in radio management and one of the most interesting parts of the job for me was learning how the Federal Communications Commission (FCC) managed the FM band of the spectrum given over to radio frequencies. It was confusing, and governed by a book of rules as thick as the tax code so when I hear news about changes to the any of the spectrum my ears perk up. I know a lot of thought, time, science and argument has gone into the discussions leading to this point.

To understand the electromagnetic spectrum, think of it like the sky with different wavelengths serving as different altitudes. The radio frequency spectrum would be closest to earth, say from zero to 10,000 feet (just for example.) Within that range of “altitude” the FCC manages the different radio and television frequencies – FM, AM, short wave, UHF, etc. – by assigning them altitudes similar to the way the FAA moves air traffic through the sky. If you’re traveling on an international flight the FAA will tell you to fly at 50,000 feet, national through traffic at 40,000 feet, local landings at 10,000 feet, prop planes at 5,000 feet and so on. The FCC knows that FM scientifically, radio waves flying through the air in a certain range of “altitude” (technically hertz) and that antennas tuned to the right “altitude” can receive them, so they assign individual stations or companies specific hertz frequencies that only they can transmit their signal on. Any antenna searching that frequency will pick up their signal.

Mobile and wireless signals travel on the same part of the spectrum as radio and television signals. When I was in radio, the FCC opened an application window every few years during which stations could apply for new frequencies – either better places on the radio dial or frequencies in other locations used to expand their reach. Thousands of stations would often apply for the same signals because competition is fierce so you can see that adding mobile and wireless waves to the spectrum only makes for a more crowded and competitive environment. Pack too many signals too close together and you get interference and signal obstruction, which angers consumers and is expensive for companies to fix.

But many stations apply for frequencies they never end up using. Sometimes they sell them and sometimes those signals just sit there, unused. Furthermore some portions of the spectrum are reserved for government or scientific use – for the military, national defense, or research. Every few years the FCC evaluates whether those portions of the spectrum are being utilized and when they realized that large chunks of space sat empty much of the time, they started discussing spectrum sharing. That means someone like a mobile operator could be allowed to transmit on a portion of the spectrum normally reserved for someone else. Sometimes that would be dependent on the original owner’s need, for example if the Army only used on frequency for communications during a two week exercise every year then a wireless carrier might be allowed to use it the other fifty weeks. However when the Army needed the signal the carrier would be responsible for shutting off their access, leaving their customers either overcrowded onto other signals or just out of luck. Further concerns include ensuring things that need to be on, like medical devices or security, don’t get allocated to that shared portion of the network.

The going wisdom has been that spectrum sharing could be the answer for increased need as mobile data use continues to skyrocket. One study done in 2008 found that mobile data traffic was expected to increase twenty to fifty times levels at the time (research firms differed in results) by 2014. That, of course, is where we are today. Spectrum sharing could still work as long as the original owners of the bandwidth never need to use it, or for short periods of time. Say that a city is hosting the Super Bowl and expecting a huge influx of people; allowing wireless carriers more of the spectrum to allocate to that city can alleviate network overload on a temporary basis.

Yet a new study on shared spectrum just out from GSMA/Deloitte is a little concerning as it argues that spectrum sharing is not the answer, and in fact could seriously prohibit the economic growth of the mobile data industry. The report concludes that exclusive spectrum licensing – taking spectrum space off “reserved” status and just reassigning it to the wireless industry – could bring $260 billion to the US economy by 2030. Sharing the spectrum would reduce that number to at least $210 billion and possibly as low as $7 billion.

So you can see this is a massive decision, and one the FCC and its global counterparts have to both think through carefully, yet make soon, before we reach a crisis bottleneck in wireless data growth. All part of the growth pains of our wireless age.