Large scale carrier aggregation for the win

The Super Bowl is not only the pinnacle of the American Football season, but it is also the show case event for wireless carrier. Every year, every wireless carrier sets aside tens of millions of dollars to improve the wireless network for the big game. The newest and best gets installed so that attendees and regular citizens alike get a superior experience. One of the challenges that mobile operators have to overcome in order to provide faster speeds is how to best use the spectrum they have. The spectrum portfolio of each carrier has different amounts of spectrum ranging from 600 MHz and 700 MHz all the way to 39 GHz. In order increase the speed for customers, the spectrum slivers can be bonded together in a process called carrier aggregation (CA). The maximum amount of spectrum that LTE can have in a channel is 20 MHz and 5G is 100 MHz. So even if a mobile network operator has 1,200 MHz of contiguous spectrum with 5G they could aggregate 12 100 MHz channel for the maximum amount of bandwith which directly translates into speed.

Global Wireless Solutions (GWS) conducted network testing during the 2021 Super Bowl in Tampa and provided some additional insights that typically don’t get mentioned with other tests. GWS found that AT&T used 8 channel CA using 800 MHz of its 39 MHz spectrum, Verizon used 6 CA using 600 MHz in 28 GHz, and T-Mobile 4 CA using 400 MHz in 39 GHz plus 80 MHz in the 2.5 GHz band. The availability using the 28 and 39 GHz band was almost the same for every carrier at 73% to 77%, which isn’t surprising considering the relatively small area covered. T-Mobile’s 2.5 GHz coverage added another 20% of coverage. Considering more spectrum means more speed, it comes as no surprise that AT&T was the fastest with peak speeds of 1.7 Gbps, Verizon with 1.5 Gbps and T-Mobile with 1.1 Gbps.

The GWS tests show that it is not only important to have a lot of spectrum. It is even more important to use it. Not only does the network have to be ready for it, but also the device. Most flagship devices are using the Qualcomm Snapdragon X55 modem. Devices using this modem, like the Samsung Note 20 that the GWS engineers used for the tests can utilize 8 channel CA in the mmWave band (> 6 GHz) with 2×2 MIMO and 200 MHz 4×4 MIMO below 6 GHz with 7×20 MHz channel CA for LTE. This means that when T-Mobile uses all its on average 130 MHz 2.5 GHz spectrum, current flagship devices will be ready. When Verizon and T-Mobile are ready to follow AT&T’s lead with 8 channel CA, the devices will also be able to support that. The Qualcomm X60 modem that’s for example in the Samsung Galaxy S20  can aggregate spectrum below and above 6 GHz. This allows to combine the better coverage characteristics of sub-6 GHz spectrum with the massive spectrum bands and therefore speeds that are available above 6 GHz. The X60 modem also works with the upcoming C-Band networks that will probably become available in 2022.