Entner: The misguided and misleading spectrum discussion

Roger Entner Recon Analytics

Roger Entner

There is currently series of proposals going around in Washington around the value of high-frequency spectrum versus low-frequency spectrum. The discussion might be academically interesting, but are divorced from the real world.

When we look at the text-book properties of spectrum it is clear that lower frequency spectrum has ideal propagation characteristics.  Using the same level of transmission power, a lower frequency signal goes further than its higher band brethren in flat territory and has an easier time penetrating walls and foliage. Comparatively speaking, lower frequency spectrum requires carriers to construct fewer cell sites to cover a given area. For example, a 1900 MHz-based wireless networks needs one-third more cell sites than an 800 MHz-based wireless network.

And now comes the current discussion about whether and how low-band spectrum should be allocated among competing wireless companies as the FCC develops the rules for the upcoming broadcast incentive auction.  Recall that Congress directed the FCC to reallocate broadcast spectrum for wireless broadband services as a way to head-off the looming capacity crunch facing most U.S. wireless carriers. Something that seems to have been forgotten is that the spectrum crunch in the United States does not exist in rural America.  It only exists in the densely populated urban areas. Rural America is as well covered as it is profitably possible to cover with the industry's existing spectrum portfolio of 700 MHz to 2.5 GHz.

Where we have a problem is in the densely populated areas where the spectrum propagation characteristics of high-band spectrum are preferred because the focus is on expanding capacity, not coverage. In fact, the very properties that make low frequency spectrum so useful for covering large, flat, lightly populated areas become handicaps in the densely populated urban canyons where the spectrum crunch is happening. The reason has everything to do with physics and network design. In the densely populated areas, carriers have to deploy more and smaller cell sites to handle exploding usage patterns.  More cells sites means more opportunities for interference, especially as the cell sites are located in closer and closer proximity to each other due to limited locations for cell site deployment in urban markets.  In this scenario, high-band frequencies are prized because they give the networks the depth of capacity the carriers need, yet create fewer interference issues than low band. Further, whether low band can cover more miles with fewer sites is irrelevant in the urban markets.  It's all about capacity in midtown Manhattan.  As a result, a 700 MHz network in New York City looks identical to a 2.5 GHz network in terms of how many sites it needs to achieve close to identical coverage.

What this tells us is that the need for spectrum is due to capacity constraints rather than coverage constraints.  A debate about spectrum policy that ignores this reality is clearly misguided.  Further, a policy debate over whether to treat companies that hold low-band differently than licensees of high-band for purposes of future transaction or auctions involving low-band is also misguided.  Consider the following chart which depicts licensees of various bands of spectrum.