China is hosting one of the few in-person technology trade shows since the start of the coronavirus pandemic.
More than 200 companies and about 20,000 people are expected to attend Mobile World Congress Shanghai.
But the three-day event has been scaled back from previous years - 60,000 were at the last MWC Shanghai, in 2019.
Faces masks are obligatory at the show. And exhibitors have been told they must observe "strict" capacity limits at their stands.
The event's organiser said the combination of Covid-prevention measures and the country's vibrant technology sector meant it was the only place that could host such an exhibition at this time.
"We believe this congress will help strengthen the confidence of the global industry," GSMA trade association head of Greater China Sihan Bo Chen added.
The trade show takes place against the backdrop of continuing US-China trade tensions.
At Huawei's keynote address, chairman Ken Hu said it had managed only slight growth over the past year.
President Donald Trump's administration put the company on an export blacklist in 2019 and cut off its access to computer chip manufacturers in 2020.
"Huawei was confronted with some extraordinary difficulties," Mr Hu said.
The show also comes at a time that other attendees - including US chip designer Qualcomm - have warned they face-chip supply issues of their own because demand is outstripping supply.
But it is also an opportunity to show off innovations.
So far, these have included:
ZTE's Axon 30 smartphone - its second attempt to make a phone with a selfie camera hidden under the display, after the original was criticised for relatively poor-quality photos
Oppo's 125-watt flash charger, which the company says can fully recharge a smartphone in 20 minutes
Huawei's foldable Mate X2 handset - the company has switched to a design pioneered by Samsung but says it has found a way to close the device so both sides lie flat against each other rather than there being a gap around the hinge
The GSMA is still hoping to host a version of MWC in Barcelona at the end of June, when it plans to require visitors to have tested negative for coronavirus within 72 hours of arriving at the venue.
But some have doubts.
"With the current situation, it's hard to see many people being both willing and able to travel until later in 2021," Opensignal analyst Ian Fogg tweeted.
"September maybe, June is much more iffy."
And there is still a question mark over some of the year's other big technology showcases, with growing speculation Los Angeles' E3 video-games expo will be limited to virtual live-streamed content.
Banner image reading 'more about coronavirus'