Ookla’s November 3 analysis of U.S. route tests finds Starlink Direct to Cell (D2D) texts and small-data tasks less reliable and slower than a representative terrestrial cellular network on the same routes. RootMetrics’ second-half 2026 tests take place in moving cars.
How D2D compared with cellular
In the U.S. national-route tests, RootMetrics records lower D2D success rates and longer median times for both messages and small-data tasks. The cellular results come from a representative network tested along the same routes, according to Ookla’s analysis.
| Measure | Starlink D2D | Terrestrial cellular comparison |
| Texts delivered | 86.1% | 98.1% |
| Median text-delivery time | 16.6 seconds | 1.3 seconds |
| Fully successful lite-data tests | 60.1% | 92.9% |
| Partially successful lite-data tests | 34.5% | 5.9% |
| Failed lite-data tests | 5.4% | 1.2% |
| Median lite-data task time | 922 ms | 156 ms |
What the 30 KB task measures
The lite-data test attempts to download a 30 KB file once per second for 20 seconds. Its completion time measures how those small tasks went, not the network’s maximum download speed: Ookla says the task does not fill the connection and its timing is dominated by round trips.
The route results also come from moving-car tests. Ookla says Starlink recommends using D2D outdoors while stationary, so these tests do not reproduce that recommended setting.
Signal results and per-beam estimates
On T-Mobile’s U.S. national routes, RootMetrics reports no-signal results in 2.01% of tests in the second half of 2024 and 0.50% in the second half of 2026. D2D connections make up around 2% of those route tests in the latter period.
Separate Speedtest Android background scans put the U.S. median RSRP, a measure of received signal strength, at -120 dBm for D2D and -105 dBm for terrestrial LTE from October 2025 through September 2026. Values closer to zero indicate a stronger received signal. RootMetrics’ 2026 drive tests separately measure D2D signal strength at -118 dBm.
Ookla calculates an estimated capacity of 4.7 Mbps per beam using a median D2D RSSNR of 3.0 dB, 5 MHz operation and a 3GPP calculation. RSSNR describes signal quality relative to noise. Ookla says each beam covers an area about 21 miles across. The 4.7 Mbps figure is a model-derived capacity estimate, not a speed measured on an individual phone.
A separate U.S. study by Garcia-Cabeza and co-authors models 3.1 Mbps of downlink capacity per beam from crowdsourced measurements collected from October 2024 through July 2025. The study describes this as an upper-bound average for a single user occupying the full beam. Its estimate and Ookla’s 4.7 Mbps calculation use different periods and methods; neither measures download speed delivered to a user’s phone.
What SpaceX reports about the uplink
In a March 4, 2024 filing to the Federal Communications Commission, SpaceX reports that measured uplink and downlink link budgets were within 1–2 dB of its modeled values during non-commercial PCS G Block tests conducted with T-Mobile’s consent. The filing gives no uplink throughput rate. Read SpaceX’s FCC filing.
