Don't expect to be able to use the same phone across 5G networks, at least in the early days, says AT&T. "It's not because there isn't a desire and we don't want to," explained Gordon Mansfield, AT&T's VP of radio networks and device design, to PCMag. Technical challenges are the roadblock that will prevent 5G roaming from the onset. Specifically, phones won't be able to contain the 28 GHz 5G radio used by Verizon and T-Mobile, and the 39 GHz 5G radio used by AT&T in a single device. This means the first 5G phones will likely be carrier exclusives. The same story played out when LTE 4G first launched, as network operators used disparate bands for their high-speed service. It wasn't until 4G radios began to support multiple bands that LTE roaming became a reality. Mansfield believes this scenario won't last too long with 5G. "As an industry, that will be very quickly overcome; I don't think the single band introduction from the millimeter-wave point of view will last very long," he said. AT&T's first 5G device, expected before the end of the year, will be a puck-style mobile hotspot. The carrier hasn't said when it will go on sale, nor how much it will cost. The company is also preparing 5G-enabled smartphones, though those aren't expected to reach the market until 2019.


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