AT&T Promises Nationwide 5G in Second Quarter 2020

Low-band spectrum does matter, where it comes to coverage, no matter which mobile generation uses that spectrum. 

“Our 5G network covers 50 million people today and we expect to have nationwide 5G coverage in the second quarter,” says Randall Stephenson, AT&T CEO. 

Many early tests suggest that low-band 5G provides better access speeds than 4G, but not all that much, perhaps 20 percent in some cases. In principle, 5G speeds are expected to be higher or faster than 4G, but the precise degree of improvement depends on which 5G frequencies are used. 

Low band (600 MHz to 800 MHz) might be 20 percent faster than 4G. Mid-band 5G (2 GHz to 3.5 GHz) might be six times faster than 4G. Millimeter wave 5G (24 GHz, 28 GHz) might be an order of magnitude (10 times) faster than 4G. 

In principle, 4G can reach 100 Mbps, while 4G Category 4 can reach 150 Mbps and 4G using LTE Advanced can reach 1 Gbps. The 5G standard allows for speeds up to 10 Gbps, if enough millimeter wave spectrum is available, and the widest channels are used. 

So far, in South Korea, for example, customer experience on 5G might not be viewed as significantly different from 4G experience. 

Mid-band spectrum, on the other hand, has shown significant speed differences from 4G. To be sure, since wider channels supply much faster connections, channel size--in addition to frequency--explains why low-band 5G is not really different from 4G. 

Even if 5G channels can be quite a bit larger than 4G, as a practical matter, running 5G in the low band is subject to low-band channelization plans, which typically range from 10 MHz to 20 MHz, even if 5G can support channels of 500 MHz. 

Other techniques, such as dynamic spectrum sharing, allow 5G radios to operate in 4G bandwidth. But in such cases the 5G channels are limited to 4G limits. 

Spectral efficiency depends on several matters, including the type of radios used, the channel bandwidth, frequency and modulation techniques. Using the same radio modulation and radio types, 5G tends to be more bandwidth efficient than 4G. But the improvement is on the order of 20 percent when using low-band spectrum. Efficiency might approach 50 percent using mid-band frequencies. 

As there is a direct relationship between channel width and bandwidth or speed, so there is an inverse relationship between frequency and capacity. Lower frequencies simply are not as capable as mid-band or millimeter wave frequencies of supplying bandwidth and internet access speed. 

5G coverage is important, without question. But the eye-popping speeds possible with millimeter wave spectrum will not be possible when using low-band spectrum. 5G will be incrementally better than 4G when using low-band spectrum. But only incrementally and marginally better.