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25 April 2023

AT&T turns up the heat on 5G SA, sheds little use case light

AT&T has been singing from the rooftops about its 5G Standalone (SA) network over the last week, boasting of taking 5G to the next level with messages that have largely been lapped up uncritically by analysts and journalists.

Yet, it highlights a sense of desperation among many operators over 5G SA, to which they may be committed but are concerned may not achieve ROI anywhere near as quickly as they anticipated, if at all. If we peer just a little beneath the surface of AT&T’s recent prognostications, we can see there has been a change of tack over some of the use cases presumed to deliver these new revenues, such as the connected car.

This is not to belittle the technologies or the achievements of AT&T’s engineers in staging some of the demonstrations featured in the recent announcements. The concern is more over how these advances can be translated into the desired revenues, given that so far consumers have taken 5G very much in their stride; with any improvements in capacity and speed taken for granted as part of the natural progression in such services, rather than being welcomed as a breakthrough worth paying for.

We can see that amid this publicity barrage for 5G SA in a blog just written by Jason Sikes, AT&T’s AVP (Assistant Vice President) of device architecture. He noted as an argument for deploying 5G SA that AT&T was witnessing demand for uplink capacity and speed increasing by around 30% per year over its mobile network, as a result of consumers generating more and more of their own content for uploading.

With that figure in mind, AT&T demonstrated two-carrier aggregation in the uplink in 5G SA, which was notable because nearly all the cases so far have been in the downlink where historically traffic has been much heavier. In this case, AT&T aggregated low 850 MHz spectrum in the band known as n5 with 40 MHz of mid C-Band n77 spectrum at 3.7 GHz, using Nokia’s 5G Air Scale portfolio and MediaTek’s 5G M80 mobile test platform.

AT&T found that the extra 40 MHz C-Band doubled uplink capacity compared with the low band alone. The operator then tried extending the C-band channel to 100 MHz and aggregating that with the low band, yielding a 250% increase in uplink capacity in that case.

Also significant here are AT&T’s trials of two-layer uplink MIMO over TDD (Time Division Duplex) to provide flexible uplink capacity that can be turned up or down on demand. TDD potentially increases capacity if it can deployed flexibly, by allowing use of the full channel width during transmission, but to operate most efficiently over combined uplink and downlink requires dynamic switching between the two.

After all, most available UE (User Equipment) can support no more than two RF transmitters, putting the onus on the ability to switch between them efficiently, which is what AT&T appears to have accomplished.

AT&T has also planned to start aggregating mmWave spectrum with the low and mid-band carriers, which Sikes says will then enable 5G NR-DC downlink speeds up to 5.3 Gbps, and uplink up to 670 Mbps. He speculates this would serve “stadiums, airports, and other high-density venues.”

It would indeed but the question is whether the punters would pay more for some assurance they will be able to upload at such rates in crowded public environments. There is no doubt that AT&T is heading in the right direction technically, but there is some confusion between the general public use case and some of the vertical sectors it is also seeking to address.

As part of this recent campaign, AT&T also cited the connected car as an important driver of uplink capacity. This might seem curious to those familiar with AT&T’s earlier promotion of C-V2X (Cellular Vehicle to Everything), which is part of the 3GPP standards but where the V2X component is largely served by local sidelink communications at 5.9 GHz in many countries – distinct from the public macro network.

AT&T has championed the C-V2X cause more vehemently than any other tier 1 operator,  and was at the front of the queue seeking to provide input to the first Connected Car report and forecast from Wireless Watch Research (then RAN Research).

Back then, AT&T was enthusiastic about local V2X and talked of a world where vehicles would be communicating locally among themselves to advertise their position and hazards they had identified, on the road towards full autonomous driving. That road has proved full of potholes, and that vision of local car connectivity has yet to come to pass beyond limited trials, often in places such as ports and industrial sites away from public roads.

AT&T has therefore adjusted its vision by focusing more on the uploading of data over the public network, rather than the V2X sidelink. There is already a lot of data uploaded from vehicles over public mobile networks but often relatively low volume telematics. AT&T envisages growing demand from users in cars seeking to upload data, but it is not clear whether that would all require dedicated connectivity beyond that already serving users on their smartphones.

AT&T is certainly eyeing up third-party applications such as insurance, which could entail sustained uploading of larger amounts of monitoring data, as drivers sacrifice privacy for the benefits of lower premiums. At any rate, AT&T is now focusing more on the public network in the connected car context.

AT&T is also targeting mobile gaming and video calling as two obvious applications demanding high uplink capacity. The operator brought 5G into its gaming equation in May 2022, when it launched the game Control Ultimate Edition in the USA. But with no download or subscription required, there is again the question of where revenues are coming from; presumably just selling premium packages with guaranteed SLAs for the specific application.

For video calling, AT&T does offer an option requiring no download, allowing calls to individuals or groups, with ability to switch between HD voice and video during the session. But consumers are already engaging widely in video calling via messaging apps such as WhatsApp, while meeting packages such as Zoom and Microsoft Teams achieve effectively the same task. It is not clear there will be that much extra demand for a dedicated video calling service at a time when the use of mobiles for traditional voice calls is in serial decline.