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Google's new Nexus phones will work on its Project Fi network

The Nexus 5X and Nexus 6P can be used on the tech giant's experimental Wi-Fi network, giving consumers a few more choices in compatible devices.

Google has tripled the number of devices its Project Fi wireless service supports, a move the company hopes will spur adoption of the Wi-Fi-driven service.

James Martin/CNET

The Internet giant on Tuesday took the wraps off two new phones in its Nexus line of smartphones: the 5.2-inch Nexus 5X, made by LG, and the 5.7-inch Nexus 6P, made by Huawei. The new phones, introduced at an event in San Francisco, come with improved cameras and the latest version of the Android software dubbed Marshmallow. They also offer another key feature: support for Google's Wi-Fi-centric wireless network.

The Nexus product line has served as a testing ground for Google's Project Fi, the company's experimental wireless carrier service, since it was announced in April. The service offers customers the ability to switch between cellular and Wi-Fi signals for a phone call, reducing strain on cellular networks and lowering prices for consumers. The service has so far only been available for the Nexus 6 smartphone, which Google released last year. This has naturally limited the number of customers who could sign up for the service.

What is Project Fi?

Google launched the service earlier this year as a way to spur innovation in the wireless service market.

For Project Fi, Google uses more than a million Wi-Fi hotspots that provide cheap access to the Internet. To fill in coverage gaps, Google uses cellular networks from Sprint and T-Mobile when Wi-Fi isn't available or a signal is too weak. This is similar to other services from companies like Republic Wireless, Scratch Wireless and FreedomPop. They were among the first companies to build mobile businesses that use free Wi-Fi networks first and then switch to cellular service as a backup when Wi-Fi is not available.

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A key aspect of the Project Fi service is that it uses technology that can determine which network offers the best connection. This means it will seek out the best-performing network, whether that's Wi-Fi, or T-Mobile's or Sprint's 4G LTE and voice networks. Then it will seamlessly switch among these networks if the connection weakens. For instance, if you start a phone call or data session in a Wi-Fi hotspot at home and then get in your car and drive down the street, the call will stay connected even as your phone reconnects to a cellular service once it is out of range of the Wi-Fi connection.

Keeping costs low is a key priority for Google's Project Fi. Currently, users in the US pay $20 a month for unlimited calls and texts. Adding data costs $10 for each gigabyte of data used. If customers don't use their allotted data in a month, they get a data credit. The service has gotten mixed reviews. CNET editor Lynn La reviewed the service this summer in San Francisco and found it to be slow compared to pure cellular services.

Google admits it's early days for the project and it hopes that adding more phones that can be used on the network will drive usage and more experimentation with the Wi-Fi wireless service model.

CNET reporter Richard Nieva contributed to this report.