Millemeter Wave is Tactically a Chore but Strategically Essential

Opinions about millimeter wave spectrum for mobile networks often focuses on short-term issues rather than long-term realities. In the near term, millimeter wave spectrum does require denser, small cell networks. 

That means higher network costs and construction issues. Mobile operators naturally will prefer to build 5G on mid-band spectrum, which can reach high coverage with important advances in potential bandwidth much faster than a “millimeter wave only” alternative. 

Long term, as mobile bandwidth demands continue to increase, no matter what is done with cell sizes, reclaiming low-band spectrum and more-sophisticated radio technology, the only available spectrum to support 6G and future generations will be found in the millimeter regions. 

In this illustration, the existing 2G, 3G and 4G spectrum assets are shown at the far left. The width of the blue bars roughly illustrates the amount of capacity at different frequencies. 

The horizontal axis represents the frequency spectrum from approximately 1 GHz to 90 GHz on a relative scale (mobile services tend to use frequencies at 600 MHz to 800 MHz at the low end).

The orange bars show the approximately 11 GHz (capacity, not frequency)  of new spectrum released by the FCC for both licensed and unlicensed use. Note that the total amount of new bandwidth is orders of magnitude more than all bandwidth presently available for mobile purposes.

The red and green blocks show frequency allocations for the aerospace, defense and satellite communications industries, parts of which might ultimately be available using shared spectrum mechanisms.

source: Anokiwave  

The point is that higher data demand will require additional spectrum, even if all the other tools (smaller cells, spectrum sharing, better radios) are used. The illustration below makes the same point. The traditional “mobile spectrum” is shown in light blue. For the most part, other users have rights to use spectrum below 600 MHz. 

That means new spectrum must come from the millimeter and other high-band spectrum areas. 

source: Researchgate 

Millimeter wave is not as easy to engineer as low-band or even mid-band resources. Much more backhaul facilities are required. More radio engineering often is necessary. And indoor signal coverage is nearly a separate task, as millimeter signals are largely restricted to outdoor coverage. 

So it is quite understandable that some do not believe millimeter wave will be so important, near term, as mid-band spectrum. 

Longer term, networks will have to be crafted to use millimeter wave assets, though. There simply are no other sources of new spectrum to be tapped, once all other mobile spectrum from legacy networks is repurposed.