We are finally starting to see a glimpse of some of the 5G specifications being introduced into cellular networks. AT&T announced recently that it was going to be testing dynamic spectrum sharing (DSS) in the network, introducing one of the major benefits of 5G. The company will be testing the technology somewhere in north Texas.
DSS technology allows a cellular carrier to use a block of spectrum for both 4G LTE and 5G customers. Currently, each carrier has set up entire separate spectrum blocks for 5G customers that are only used for 5G. As more people buy 5G phones, those new spectrum blocks will get crowded and could eventually perform worse than 4G.
With DSS, a carrier can use any block of spectrum in the manner being requested by a customer handset. A handset seeking a 4G connection will get a traditional 4G channel of bandwidth. If a handset asks for a 5G connection, then that phone can connect as 5G and can provide whatever 5G features are available at a cell site.
I can’t say for sure because I may have missed announcements, but this is the first introduction of a 5G feature that I have noticed. Until now there has been no true 5G. There have been 4G LTE phones that used traditional bands of spectrum and 5G phones that have used new bands of spectrum – but the 5G phones don’t yet benefit from any of the upgrades due to the 5G specifications that will make 5G superior to 4G. Instead, customers have been reporting a good 5G experience because their phone grabs a relatively unbusy band of new spectrum that isn’t as crowded as 4G has become.
DSS is important to cellular carriers because it will make all of their spectrum available to 5G customers. This will allow for a smooth transition over time where 5G customers can address 5G features from any spectrum band and where 4G LTE customers continue to use those same spectrum bands in the traditional manner.
This is only a trial, and most trials uncover issues that need to be tweaked, so it’s likely to be much later this year or next year before AT&T is ready to roll out DSS in other markets.
We are still waiting for the most important 5G features to be introduced. The most powerful feature is going to be frequency slicing where a cell site can easily tailor the transmission path to meet the demands of a customer. This is the feature that will be able to devote a large data path to a heavy data user. The real benefits of 5G can’t be realized until the 5G features have been widely introduced and also loaded into cellphones.
The timing of getting features into cellphones is one of the biggest challenges for the cellular carriers. For the DSS trial to work there has to be sufficient handsets in north Texas that can use the feature. This means that carriers need to introduce features into handsets in advance of introducing them in the field, and I have to imagine that phones blessed by AT&T already have some version of DSS software included.
Something that the cellular carriers aren’t going to be talking about is that for many years the feature sets in the software for handsets will differ by carrier. It’s not going to be an easy transition to move a 5G phone between AT&T and T-Mobile for a while since they will use 5G differently. Eventually, everybody will provide all of the features, but until they do there will be differences in 5G performance between carriers.
The primary advantage of DSS is that the carriers don’t have to keep turning up new bands of spectrum to keep 5G customers happy with the experience. No matter where a customer is, with DSS a 5G phone will be able to grab spectrum – although if they grab 4G spectrum they end up back in the same crowded pot of traditional spectrum with all of the 4G customers. If carriers decide to give 5G customers any sort of priority in traditional spectrum bands, then we’ll see performance start to degrade over time for people with 4G LTE handsets. That sounds like a good strategy to get people to upgrade phones.
From a customer performance perspective, this is not an exciting announcement. This early 5G feature doesn’t give anybody faster performance. The only real benefit is to the carrier to let them use their full range of spectrum for a 5G customer.
Meanwhile, the 5G marketing machine that has snowed every politician in Washington DC will continue to crow about how great 5G is for America, while at the same time complain how we’re losing the 5G battle with the Chinese. Those are both false narratives because there aren’t yet any customers in the US getting a real 5G experience. Even folks in center cities that are using the fast millimeter wave spectrum don’t have 5G – they just have handsets that use the faster millimeter wave spectrum.
But the introduction of a 5G feature into the wild means the day will come when real 5G will hit the network and customers will begin to see a difference between 4G and 5G. By then, the marketing machine will probably be off talking about 6G.