G6, G5 and 5G: Everything from Mobile World Congress press day

The show floor for Mobile World Congress , the world's biggest showcase for wireless technology and mobile devices, doesn't officially open until Monday. But like all good trade shows, "day zero" is press conference day.

The elephant in the room at the 2017 show is the phone that isn't here: the Galaxy S8. But Samsung teased the phone at the end of its otherwise sedate Sunday press conference, confirming the rumors that the phone would indeed be unveiled on March 29 in New York City.

MWC 2017: All the gadgets announced so far

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With no big Samsung announcement, the playing field was left wide open for the likes of LG , Huawei , Lenovo and ZTE to strut their stuff. Here's what they had to show.

LG G6 rules the roost

Watch this: LG G6 is water-resistant, with a whole lotta screen

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With no Galaxy phone on deck, the LG G6 was the big dog of the day. The Korean company's 2017 flagship phone offers a nice big 5.7-inch screen with an unusually tall 18:9 aspect ratio (instead of the 16:9 standard). It's the first phone with support for Dolby Vision HDR, which could mean better-looking images, too. It's fully waterproof, and has a dual-lens camera with some nifty photo tricks, too. Early downsides? The G6 doesn't retain the LG G5 's swappable batteries -- a feature that's largely going the way of the dodo -- and its Qualcomm Snapdragon 821 processor is effectively a 2016 chip that's a step behind the latest and greatest 835 we'll see in upcoming phones .

But hey -- it does have a headphone jack.

• LG G6 hands-on: 4 reasons you'll want this sleek phone with its massive screen (and 2 reasons you won't)
• The LG G6 has a new camera app for Instagram addicts. Here's how to use it
• LG G6 is the first phone to debut Dolby Vision HDR
• LG G6 hopes to out-iPhone the iPhone 8

Nokia goes back to the future

Yes, Mobile World Congress has a bit of a retro flavor this year. The show kicked off on Saturday night with the introduction of the BlackBerry KeyOne, a full-on Android-powered keyboard phone (produced by China's TCL) that recalls company's pre-iPhone glory days.

Get a close look at the rebooted Nokia 3310

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Not to be outdone, old-timer Nokia (or, at least, licensee HMD Global) showed off three Android phones of its own. More enticing, however, was its 3310 "feature phone," a non-smartphone based on a 1990s classic that makes phone calls and sends texts -- and not very much else. But will this revived Nokia finally come forward with a real game-changing phone? The jury's still out on that one.

Oh, and remember when Nokia bought Withings, the French health and wearable company? That brand is going away, and those products will get the Nokia brand going forward.

• Nokia 6 is the company's top-line Android phone
• Nokia 3 and 5 bring up the middle of its new Android phone lineup
• Nokia 3310 reboot has month-long battery life
• Where's the Nokia phone we're craving?
• A cheeky rebadging means you can soon buy a Nokia smartwatch

Lenovo's budget play

Nokia bought Withings, and Lenovo bought Motorola. But the company has wisely kept the Moto smartphone brand alive. Its newest Android models are trying to redefine "budget," offering high-end niceties like splashproof metal bodies, expandable storage , dual SIM slots and -- outside the US, at least -- NFC support.

Watch this: Moto G5 Plus has a metal build and flagship camera

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Lenovo is also expanding the Moto Mod offerings on its higher end Moto Z line, with snap-on gaming and even Alexa accessories on deck for the future.

• Moto G5 Plus wants to take bargain phones to the next level
• Hands-on with the Moto G5's metal budget build
• Amazon will make a Moto Mod with Alexa for the Moto Z
• New Moto Mod for gamers goes after the Nintendo Switch

New Samsung tablets , and a Galaxy S8 teaser

Samsung ended press day with a fairly sleepy event. Two new tablets -- one Android and one Windows -- dominated the proceedings, and a new Gear VR headset with a bundled controller made an appearance, too. But Samsung did end the show with a video teaser for that missing Galaxy S8: Expect to see it unveiled on March 29 in New York City.

• Samsung debuts classy, all-glass, HDR-ready Android tablet
• Samsung Galaxy Book sets its sights on the Microsoft Surface
• Samsung bets on tablets -- at a time no one's buying them
• Samsung's new Gear VR headset adds a controller to the mix
• Samsung Galaxy S8 launch date official: March 29 in New York

Everything else: Google Assistant goes big, early 5G news and new Huawei phones

Plenty of other headlines were coming out of Barcelona today, too. Next-generation 5G wireless was highlighted at nearly every press conference -- it looks like the first products may hit even sooner than originally thought, whether or not standards are ready. Huawei showed off its latest phones and wearables, too.

And Google dropped some big news: Its voice-activated Google Assistant, currently only on Google's Pixel phones and slated for the LG G6, will actually be available on nearly every Android 6.0 and later phones (in certain territories) as soon as this week. That's a free upgrade for millions of mobile users.

• Google Assistant is coming a lot more Android phones
• This 'Gigabit' phone is 5G hype's jump-the-shark moment
• 5G phones are coming earlier than you thought
• Huawei's new P10 phones: dual Leica cameras, 3D face detection and plenty of Pantone
• Huawei Watch 2 will last 25 days, still track steps
• HP Pro x2 redesign encroaches on Surface Pro territory

Check out all the news from Mobile World Congress 2017 here.