5G Does Not Change Traditional "Capacity Versus Coverage" Issues

One way of making sense of claims about 5G performance is to recall that the traditional trade off between coverage and capacity will continue to hold, even as huge new blocks of millimeter wave spectrum are released for use.

Ultimately, all the noise about strategy and assets and advantage aside, our knowledge about existing use of mobile and other devices should provide a clue to network and spectrum choices.

Many note that perhaps 80 percent of data is consumed by mobile users who are stationary, in their homes, offices or other non-moving locations. That, in part, explains the high use of Wi-Fi by smartphone customers.

The obvious implication for 5G networks is that although coverage (with lower capacity) works for outdoor and mobile use, the places where millimeter wave spectrum really adds value are locations where users are stationary (and might otherwise use Wi-Fi).

So we might as well understand, early on, that peak 5G speeds (gigabit) will tend to be found only in urban and other high-density areas where people live and work. Though 5G will supply faster speeds in mobile scenarios, speeds are unlikely to reach those possible in fixed locations, simply because the physics does not support it.

Though it is easy to debate the merits of using spectrum below 6 GHz, or in the higher-frequency millimeter bands (24 GHz, 28 GHz, 39 GHz for example), the traditional trade offs between coverage versus capacity will still have to be made.

The only difference is that the range of frequencies will shift. Where 2 GHz once was seen as “high frequency” with better capacity performance, while 800 Mhz was better for coverage, now any spectrum below 6 GHz is seen as the “coverage” suppliers, while millimeter wave spectrum is seen as the capacity bands.

source: GSM History

Ultimately, we are likely to see all service providers rely on sub-6 GHz for coverage, even if that means sacrificing capacity (speed). To supply the gigabit per second speeds 5G makes possible will require the millimeter bands, but with coverage limitations.

To be sure, millimeter saves also offer greater spectral efficiency than lower-frequency signals. Simply, the higher the frequency, the higher the potential bandwidth.