T-Mobile and SpaceX have announced the upcoming launch of their direct-to-cellular satellite internet service in July. While the service is currently in beta, offering only text messaging over satellite, data speeds are expected to be slow initially according to an analysis by Universidad Politecnica de Madrid. The study used crowdsourced mobile network data to evaluate the capabilities and limitations of the service. The current data speeds of 4 Mbps outdoors may not meet expectations for users in remote areas, but potential future improvements could see speeds increase to 24 Mbps. However, regulatory developments and service demand will play a key role in determining the enhancement of performance. Despite the slower speeds initially, T-Mobile's satellite internet service still stands out as an impressive offering in the US market, providing connectivity in areas where traditional networks may be unavailable.
Based on SINR measurements, we estimate a current mean throughput of approximately 4 Mbps, which is functional for basic services but significantly below terrestrial averages.
—Universidad Politecnica de Madrid
The speed could increase to up to 24 Mbps in the future, considering the FCC updated the out-of-band emissions limits for T-Mobile in March. TMF Associates's Tim Farrar points out that "the paper [incorrectly] assumes 10dB SINR improvement to calculate the higher theoretical capacity," so 24 Mbps is a very optimistic and possibly unrealistic theoretical maximum speed.
Looking ahead, throughput and performance may improve to 24 Mbps with higher radiated power (as recently authorized by the FCC), wider bandwidth allocation, and continued constellation expansion. However, these enhancements will depend on regulatory developments —particularly spectrum access— and on the evolution of service demand.
—Universidad Politecnica de Madrid
Regardless, the data service may fall short of expectations initially, but the speeds could improve over time.
