AT&T announced this morning that it has turned on its 4G LTE wireless network in Seattle and Portland, as the company prepares for the launch of the LTE-enabled iPhone 5 later this week.

Users of existing LTE-enabled devices on AT&T’s network should also see the benefits of the upgrade. LTE phones and tablets already on AT&T’s network include the Motorola ATRIX HD, Sony Xperia ion, HTC One X, Samsung Focus 2, Nokia Lumia 900 and Samsung Galaxy Note.

We’ve been signs that this was coming for a while. Back in July we heard from AT&T customers who were seeing LTE on their Android devices in specific spots in the Seattle region as the company tested the service.

Seattle and Portland are the latest in a series of markets where AT&T has activated LTE in recent days. AT&T is playing catchup with Verizon’s LTE network in advance of the iPhone 5 rollout, looking to prevent existing customers from making the leap to the competing provider.

The company says its LTE network offers speeds up to 10 times faster than 3G, with lower latency and more efficient use of spectrum.

Are you seeing LTE on your AT&T device this morning? Let us know in the comments, and give us a sense for the speeds you’re seeing.

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