T-Mobile said it added two new technologies to most of its wireless network to double LTE speeds, but only a few phones so far can take advantage.

Only the latest Samsung phones, the Galaxy S7 and Galaxy S7 Edge, are capable of using the faster speeds. And the phones won’t speed up until they receive a software upgrade next month, the carrier said.

It is possible that the upcoming iPhones upgrades, which Apple is expected to unveil on Wednesday, will also be compatible with the new technologies. “More phones will support it soon,” T-Mobile’s chief technology officer, Neville Ray, said in a blog post on Tuesday.

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The new technologies, called 4X4 MIMO and 256 and 64 QAM, could let customers download data at up to 400 megabits per second, about twice the limits of current LTE.

T-Mobile tmus said 4X4 was available in 319 cities. The QAM addition was live on half of the carrier’s network and would be fully installed by the end of October, Ray said.

The news follows Verizon’s vz announcement last week that it had rolled out a technique known as carrier aggregation to increase speeds by about 50% on its LTE network in 461 cities. T-Mobile said it was already offering carrier aggregation across 425 cities in its LTE network.

The carriers are focused on adding new technologies to squeeze faster speeds out of their current 4G LTE networks as the next generation of wireless, 5G, still appears to be years away.

The battling press releases also come as competition is expected to heat up in the wireless market once the new iPhones hit. In the first half of the year, competition has waned and the rate of customers changing carriers hit a record low. But new iPhones typically prompt a flurry of promotional deals to entice subscribers to defect to get free or discounted Apple aapl devices.