Advanced Television

SpaceX serious about Direct-to-Phone

January 12, 2024

A slew of statements from SpaceX executives – and a serious of job openings – suggest SpaceX is serious about the prospects of ‘direct-to-phone’ connectivity from its Starlink satellites.

SpaceX staffers have been testing signals from the half-dozen suitably equipped Starlink satellites now in orbit. The tests have used T-Mobile’s terrestrial network. SpaceX says it will add another 800+ satellites by mid-year equipped with the direct-to-phone technology.

SpaceX’s president (and Elon Musk’s #2) Gwynne Shotwell, said on January 10th: “Satellite connectivity direct to cell phones will have a tremendous impact around the world, helping people communicate wherever and whenever they want or need to. It will also be a boon for me to eliminate dropped calls during my commute in rural Texas! Super well done to the team and thank you!”

Sara Spangelo, who co-founded the ‘Swarm’ satellite business which SpaceX acquired in August 2021 and is now a senior director at SpaceX and “co-lead” on its direct-to-cell division, is now looking for new employees.

Swarm was designed as a lower cost communications network with tiny satellites each about size of a slice of toast. It is Swarm’s technology which is being added to new Starlink craft.

Spangelo said on January 10: “[We are] thrilled to announce we’ve sent our first text messages from cellphones through SpaceX’s Direct to Cell network, validating the link budget. We are excited to change the future of connectivity!”

SpaceX, on January 8th, said: “The Starlink team successfully sent and received our first text messages using T-Mobile network spectrum through one of our new Direct to Cell satellites launched six days prior. Connecting cell phones to satellites has several major challenges to overcome. For example, in terrestrial networks cell towers are stationary, but in a satellite network they move at tens of thousands of miles per hour relative to users on Earth. This requires seamless handoffs between satellites and accommodations for factors like Doppler shift and timing delays that challenge phone to space communications. Cell phones are also incredibly difficult to connect to satellites hundreds of kilometers away given a mobile phone’s low antenna gain and transmit power. Starlink satellites with the Direct to Cell payload are equipped with innovative new custom silicon, phased array antennas, and advanced software algorithms that overcome these challenges and provide standard LTE service to cell phones on the ground. As the global leader in rocket and satellite launch and manufacturing, SpaceX is uniquely positioned to rapidly scale our Direct to Cell network and will rapidly launch a constellation of hundreds of satellites to enable text service in 2024 and voice, data, and Internet of Things (IoT) services in 2025.”

That’s the good news. But questions remain. Top of the list is whether a ground-based phone can manage a satellite signal while the user is in a car or other vehicle. While urban users will have the benefit of a local cellular operator (T-Mobile in the US), what happens when the driver is in the middle of nowhere, and which the satellite is designed to serve.

One observer asked whether a user in an open-topped car would cope with wind noise from the usual airflow buffeting.

SpaceX helpfully outlined the tasks ahead: “The first challenge is transmitting sufficiently strong radio signals to and from cell phones that were not designed to connect to satellites, with very low gain antennas and transmit power (max 0.2 Watts). Our team developed custom silicon onboard the satellite that is optimised for this application and reduces power and cost on the satellite. We also developed large 2.7 m x 2.3 m advanced phased arrays that use extremely sensitive radio receivers and high-powered transmitters for communicating with cell phones from space. The antennas were designed to ride on the Starlink v2mini satellites and are reliably launched and deployed to low-Earth orbit every few days by the Falcon 9 rocket. SpaceX is uniquely positioned to rapidly scale out our first Direct to Cell constellation in mere months, due to our unique and unprecedented vertical integration controlling both launch and satellite production in addition to operations. In the future, we will launch Direct to Cell satellites on Starship to improve the service even further and increase our launch cadence.”

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