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So what they used to need a pizza sized phased array antenna that draws 10 Amps for is now possible with existing hardware? A bit impossible to believe unless t

So what they used to need a pizza sized phased array antenna that draws 10 Amps for is now possible with existing hardware? A bit impossible to believe unless there's a major caveat. I suppose it wouldn't be too hard to get the signal to the ground, but how can the satellites receive anything from the phone? Regardless, if this works then infinite range robotics with just a 4G modem is now possible. Anyone wanna fly a solar powered RC plane across the Atlantic? :P

stetrain 3y ago
The major caveat is extremely limited bandwidth. They are basically putting an LTE cell tower on the satellites. This can be used for very low-bandwidth applications, starting with just text messages. They are not providing 100MB+ broadband via this connection.
- moffkalast 3y ago
  Ah, so more like a LoRa level connection. Would still work for receiving telemetry and sending autopilot commands I guess. I would've thought that an LTE tower would have more throughput, but I suppose they might need far more error correction than usual?
  - stetrain 3y ago
    The website says text messages in 2024, voice and data starting in 2025, and IoT in 2026. So it seems they have had the same thought on the usefulness for remote telemetry data. I don't know a lot about LTE signals but given the distances to the satellite and wide coverage area each satellite is responsible for it makes sense that performance is significantly diminished compared to your local cell tower.
  - olyjohn 3y ago
    There's only a few thousand satellites up in orbit right now. Maybe 4000-5000? Half of them are on the other side of the planet at any given time... The service is already strained in a lot of areas. It's not gonna be easy to give bandwidth to another few million phones.
    - lxgr 3y ago
      Not just half, but most of them will be below the horizon at any point in time – their orbits are pretty low. But since mobile phones don't really have directional antennas anyway (unlike Starlink terminals), having more than one satellite in sight above the horizon doesn't really help with capacity anyway. (You need steerable beams on both sides to make use of spatial multiplexing.)
  - lxgr 3y ago
    LTE supports a very wide range of bandwidths (0.2 MHz for NB-IoT up to multiples of 20 MHz for carrier aggregation) and modulation rates. Given the transmit power constraints on both sides of satellite-to-mobile, Starlink/T-Mobile will most likely be targeting the extreme low end on both bandwidth and modulation rates.
- LAC-Tech 3y ago
  Thank you for this context. The site says "Voice and Data Starting 2025", I do wonder what will change by then.
  - stetrain 3y ago
    I imagine this will still start as pretty limited and improve over time. Voice is not that bandwidth intensive but is latency sensitive. "Data" covers a wide range that probably won't include streaming 4K YouTube at first.
matrix_overload 3y ago
The caveat is on the operator's side. Your satellites need to be much closer to the user, that means much less square miles of coverage per satellite, due to the Earth's curvature. So you need like 1000x more satellites compared to the 10 Amp antenna setup, but if you have an economically viable way of launching them, you're good to go.

stetrain 3y ago

The major caveat is extremely limited bandwidth. They are basically putting an LTE cell tower on the satellites. This can be used for very low-bandwidth applications, starting with just text messages. They are not providing 100MB+ broadband via this connection.

moffkalast 3y ago
Ah, so more like a LoRa level connection. Would still work for receiving telemetry and sending autopilot commands I guess. I would've thought that an LTE tower would have more throughput, but I suppose they might need far more error correction than usual?
- stetrain 3y ago
  The website says text messages in 2024, voice and data starting in 2025, and IoT in 2026. So it seems they have had the same thought on the usefulness for remote telemetry data. I don't know a lot about LTE signals but given the distances to the satellite and wide coverage area each satellite is responsible for it makes sense that performance is significantly diminished compared to your local cell tower.
- olyjohn 3y ago
  There's only a few thousand satellites up in orbit right now. Maybe 4000-5000? Half of them are on the other side of the planet at any given time... The service is already strained in a lot of areas. It's not gonna be easy to give bandwidth to another few million phones.
  - lxgr 3y ago
    Not just half, but most of them will be below the horizon at any point in time – their orbits are pretty low. But since mobile phones don't really have directional antennas anyway (unlike Starlink terminals), having more than one satellite in sight above the horizon doesn't really help with capacity anyway. (You need steerable beams on both sides to make use of spatial multiplexing.)
- lxgr 3y ago
  LTE supports a very wide range of bandwidths (0.2 MHz for NB-IoT up to multiples of 20 MHz for carrier aggregation) and modulation rates. Given the transmit power constraints on both sides of satellite-to-mobile, Starlink/T-Mobile will most likely be targeting the extreme low end on both bandwidth and modulation rates.
LAC-Tech 3y ago
Thank you for this context. The site says "Voice and Data Starting 2025", I do wonder what will change by then.
- stetrain 3y ago
  I imagine this will still start as pretty limited and improve over time. Voice is not that bandwidth intensive but is latency sensitive. "Data" covers a wide range that probably won't include streaming 4K YouTube at first.

matrix_overload 3y ago

The caveat is on the operator's side. Your satellites need to be much closer to the user, that means much less square miles of coverage per satellite, due to the Earth's curvature. So you need like 1000x more satellites compared to the 10 Amp antenna setup, but if you have an economically viable way of launching them, you're good to go.