First 5G call is made over AT&T's C-band spectrum
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T-Mobile's acquisition of Sprint was a brilliant move on the part of the carrier because it gave the upstart wireless provider control over Sprint's hoard of mid-band 2.5GHz spectrum. Using mid-band spectrum is the key to T-Mobile's 5G layer cake system that starts with the 600MHz low-band airwaves that travel great distances but deliver 5G speeds that are not much faster than 4G.
At the opposite end of the spectrum is the extremely fast high-band mmWave spectrum with signals that are limited in distance and are easily blocked by structures.
AT&T and Nokia team up to successfully complete the carrier's first test call over its C-band mid-range spectrum
The solution is to use spectrum in the middle that is faster than low-band but not as fast as mmWave, and covers more distance than mmWave but not as much as low-band. And that is what T-Mobile delivers with the mid-band spectrum it obtained from Sprint. Some analysts believe that its mid-band holdings will help T-Mobile become the nation's fastest 5G provider thanks to its triple-layer cake.

AT&T's 5G delivers faster data speeds, larger capacity, and faster latency
So what stops AT&T and Verizon from copying T-Mobile? The amount of mid-band spectrum available for cellular networks is limited, but the FCC recently auctioned off 280MHz of C-band spectrum in the 3.7-3.98 GHz band. Verizon spent $45.4 billion on winning bids with $23.4 billion bid by AT&T and just $9.3 billion spent by T-Mobile.
But not all C-band is the same as T-Mobile CEO Mike Sievert stated several months ago when he said that "the truth is that C-band is best for urban areas because it doesn’t propagate as well as T-Mobile’s substantial existing mid-band frequencies. For us, C-band makes a great story even better, and we are incredibly pleased with our clear success in this auction. Our competitors had no choice but to go all in with a break-the-bank attempt to remain relevant in the 5G era."
AT&T announced this past week that it had teamed up with Nokia to successfully make the first phone call on AT&T's C-band spectrum using a 5G enabled device with a smartphone-like form factor. The latter is powered by Qualcomm's Snapdragon X55 5G Modem-RF System. Nokia’s AirScale baseband and 5G massive MIMO C-Band radio (with a large number of connections from the radio to the device) were also deployed in the test.
The nation's third largest carrier, by the end of 2023 AT&T hopes to cover 200 million people with C-band signals which will beat Verizon's announced schedule. In March, AT&T and Nokia signed a five-year deal that will enable the carrier to cover the United States with Nokia's C-band airwaves. Nokia last year became the first 5G supplier to use C-band to successfully complete a trial in the states.
AT&T hopes to enable 5G C-band calls for subscribers later this year
Paritosh Rai, who oversees AT&T's 5G Project Management Office, stated that "Bringing 5G innovation to market is very important to our teams. Working on these C-band field test calls gave us a feeling of, 'Let’s make history again!'" Later this year, AT&T is expected to flick the switch that will make C-band signals available to the first batch of AT&T's 5G customers.
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