Most of the nation's major wireless service providers are rushing to make announcements about deploying 5G mobile service on some minor scale.
For example AT&T announced that it has begun operating its first 5G network in Austin, Texas as of late April. Verizon, meanwhile, claims in a press release of its own that it’s about to launch 5G service in 11 markets by summer.
T-Mobile is not claiming immediate access to 5G wireless technology, but instead is saying that it has already begun building out a national 5G network that starts with its recently-acquired 600 MHz band licenses.
While everybody is talking about 5G, it’s worth noting that each of these carriers is talking about a different way of using the technology. Verizon’s 5G solution is designed to operate as a fixed wireless broadband service, effectively supplementing the company’s fiber-based services. AT&T is moving forward with a type of 5G that actually uses the company’s LTE infrastructure, producing only minor speed enhancements, not the 20-fold increase in throughput being claimed by 5G advocates and developers.
T-Mobile is planning to implement an entirely new 5G network that will start with those 600 MHz frequencies it won in the auction that ended in March and then expand 5G service to the other bands it’s already using. According to T-Mobile, it’s solution will deliver those promised high speeds and low latency that currently elude LTE users.
Both Verizon and AT&T plan to base their 5G operations in what’s called the millimeter wave band, which is a range of frequencies that stretch from 30 to 300 GHz. It’s called that because the wavelength of the radio signals being used measures from about 1 to 10 millimeters. By contrast, the wavelength of the 600 MHz service that T-Mobile is planning is about a half a meter. That’s 500 millimeters.
The difference is significant in terms of both the physical features of a cell site and in the operational characteristics of signals at those frequencies. Millimeter waves propagate in straight lines much like light, which is no surprise because the shortest millimeter waves are only slightly longer than far infrared. For all practical purposes, they are the same as light waves.
There are some advantages to millimeter waves, not the least of which is that antenna sizes are much smaller, which in turn allows for smaller, less obvious cell sites. However the downside of millimeter waves is that they are absorbed by nearly anything that gets in their way. The obstacles include such things as foliage, water vapor, buildings and in many cases things you wouldn’t expect, such as the glass in windows.
What this means is that carriers will have to build many more transmitter sites than they would at lower frequencies so that they can provide for full coverage despite signal blocking and reflections.