“Such signal, much wow”: Starlink’s first texts via “cellphone towers in space”

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A batch of Starlink satellites prior to launch
Enlarge / Starlink satellites with direct-to-cell capability.

SpaceX

SpaceX is showing off the first text messages sent between T-Mobile phones via one of Starlink’s low Earth orbit satellites. “On Monday, January 8, 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,” a Starlink update said.

SpaceX last week launched the first six Starlink satellites that can provide cellular transmissions to standard LTE phones. The service from what Starlink calls “cellphone towers in space” is expected to provide text messaging sometime this year for customers of T-Mobile in the US and carriers in other countries, with voice and data service beginning sometime in 2025.

SpaceX posted a photo of the two iPhones that exchanged the texts, which included messages such as “Such signal” and “Much wow.” The process that allowed those texts to be sent was pretty complicated, Starlink said.

“Connecting cell phones to satellites has several major challenges to overcome,” Starlink said. “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.”

Mobile phones have “low antenna gain and transmit power,” making it “incredibly difficult” to communicate with satellites hundreds of kilometers away, the company said. But Starlink’s new satellites “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.”

The satellite-to-phone service should work just about anywhere on the planet, but there would be no point in using it when you can connect to a ground-based cellular tower. As SpaceX CEO Elon Musk pointed out, the limited bandwidth means that “it is not meaningfully competitive with existing terrestrial cellular networks.”

T-Mobile said last week that field testing of Starlink satellites with the T-Mobile network will begin soon but did not announce a start date for actual service. T-Mobile said the Starlink connectivity will be useful in areas of the US where it has no coverage “due to terrain limitations, land-use restrictions,” and other factors.

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