All Bands will Support 5G, But Millimeter Wave is Strategic

Millimeter wave is not all of 5G, nor is 5G mostly about millimeter wave. Low, mid-band and high-band frequencies all will support 5G. 

But millimeter wave spectrum is strategic for 5G and all succeeding mobile generations for the simple reason that it represents the single biggest amount of unencumbered spectrum--with the highest capacity-- to support 5G and future networks. 

There is a simple reason why millimeter wave frequencies will prove important for 5G, and essential for 6G and future networks. Simply put, even if most of the sub-2 GHz spectrum were not already allocated to other users, the low-band spectrum is limited in terms of bandwidth. 

That matters as end user consumption of data keeps growing in excess of 25 percent a year. If mobile networks must keep supplying ever-faster speeds, millimeter wave and mid-band spectrum are key ways much more bandwidth can be supplied without dramatically increasing cost per bit, both supplied and consumed. 

As always, the other means for increasing mobile network bandwidth is to shrink the size of cells. Millimeter wave networks will use both techniques, of necessity. Simply put, millimeter wave requires small cells. 

Put simply, unless lots of millimeter wave spectrum is made available, the mobile business model breaks. 

The fundamental constraint is that more bandwidth has to be supplied at constant prices, for the most part. Consumers simply cannot, and will not, pay much more for mobile bandwidth, even as their consumption grows fast. 

This illustration by SureCall shows the big upside and the biggest challenge. Compared to 4G operating in the low end of the mid-band frequencies (around 2 GHz), millimeter wave has 25 times the potential capacity, in a base case. Latency performance is better as well, though that is a function of the standard, not the physics.

source: SureCall

The challenges lie in signal propagation. As with all radio frequency signals, distance and capacity are inversely related. Lower frequencies can travel farther, but have less capacity. Higher frequencies have limited range, but very-high bandwidth. 

In fact, until Moore’s Law vastly reduced signal processing costs and performance, it was not commercially feasible to use millimeter wave spectrum for retail end user communications, as useful as point-to-point trunking applications have been. 

It is hard to underestimate the value of millimeter wave spectrum. In the following illustration, the width of the blue bars roughly illustrates the amount of capacity at different frequencies. 

source: Anokiwave

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 U.S. Federal Communications Commission 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.

Millimeter wave represents orders of magnitude more effective capacity than all of the present mobile spectrum put together.