Direct-to-device (D2D) satellite connectivity allows standard, unmodified mobile phones to communicate directly with satellites, eliminating the need for specialized satellite phones or ground terminals. AST SpaceMobile is the leading pure-play D2D company, deploying large phased-array satellites that emulate cellular base stations from orbit. SpaceX and T-Mobile's partnership brings D2D capability to Starlink satellites, initially for text messaging.
D2D has the potential to close the global connectivity gap for the 3+ billion people who lack reliable cellular coverage. The technical challenges are significant: the satellites require enormous antenna arrays (AST SpaceMobile's are 64+ square meters) to achieve sufficient link budget with the low-power antennas in standard smartphones. Spectrum coordination with terrestrial mobile operators is another critical challenge being navigated through regulatory frameworks globally.