This week, a company called AST Space Mobile announced that it had successfully transmitted a 4G LTE signal from its BlueWalker 3 satellite-(693-square-foot) to "off-the-shelf smartphones" in Hawall using AT&T's cellular network. The tech could be used to fill in coverage gaps in the U.S. according to the press release, it "achieved repeated successful download speeds above 10 Mbps during testing."  That's fast enough for normal browsing, messaging, and even watching videos.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            What's impressive here is  that cell phones typically connect to ground-based cell towers, not satellites. That's why it's hard to get cell service on a boat a few miles out to sea when you're traveling through a rural area. But by using satellites, AST Space Mibile may be able to expand coverage to theoretically nearly anywhere on the planet. No more worrying about passing through a signal deadzone.  "AST Space Mobile's space-based cellular capabilities are designed to be a critical extension for cellular communications," Abel Avellan, chairman and CEO of AST Space Mobile, said in the press release."In addition to supporting basic voice and text that we expect from phones, it would also enable users to browse the internet, download files, use messaging apps or stream video."                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             In rural areas, towers can theoretically have a range up to 45 miles, but the connection is affected by what wavelength the tower transmits, the geography of the region, how powerful the signal is transmitted, and many other factors, so the range is often a lot shorter. Providing high-speed cellular broadband to an area as vast as the US using ground-based towers is a major challenge not readily solvable with existing technology.  While there are satellite phones, like Iridium, and satellite broadband services that require a small dish, like Starlink, there isn't yet a satellite broadband service that can reach regular smartphones.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          Deploying this kind of technology means that in most locations, your smartphone would still connect to ground-based cell towers, but when you're driving through the Sierra Nevadas or Rocky Mountains, it would be able to connect to a satellite in low-Earth orbit. Apparently, AST SpaceMobile already has "agreements and understandings" with over 35 global cellular providers. To achieve its latest success, AST SpaceMobile relied on its BlueWalker 3 satellite, which it says is "the largest-ever commercial communications array deployed in low-Earth orbit." "It's now fully deployed and spans 693 square feet. It is able to beam its 4G LTE signal to cellphones in Hawaii over AT&T's network. Next, the company wants to achieve 5G speeds.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    HARRY GUINNESS  -  POPULAR SCIENCE