3 ms·

Do any of the 4G/5G protocols accommodate satellite-based comms with some sort of special transmit mode from the phone side? It blows my mind that any of this

by xattt 3y ago

Do any of the 4G/5G protocols accommodate satellite-based comms with some sort of special transmit mode from the phone side? It blows my mind that any of this is possible, because I was a futurist as a kid, but completely dismissed off-the-shelf cell-to-sat as sci-fi only.

jacquesm 3y ago
Well, given that it is pretty much always line-of-sight it has (relatively) low power requirements compared to the distance involved, from you to the satellite you will mostly have to deal with attenuation by water vapor. Also: satellite can do beam steering through phasing shifting multiple antennas without any moving parts. So once a satellite knows you exist it can further reduce the power requirements by focusing on a phone when sending or receiving from that particular phone.
- Scoundreller 3y ago
  Do the satellite-side phased arraying work that quickly to go to the per-customer level? I figured it would just be used to account for the spinning and moving nature of the satellite.
  - jacquesm 3y ago
    The satellite side isn't nearly as power constrained as a cell phone so they don't have to get it that precise. But every dB counts. They hit multiple subscribers at once with the sat side footprint but if an area is nearly empty I don't see why they couldn't keep a particular phone in the centroid (such as in emergency services to uninhabited areas). Likely they will differentiate between populated and less populated areas by allocating more time to a spot to service all of the customers. https://erkansaka.net/2023/10/03/a-video-how-does-starlink-satellite-internet-work/ https://erkansaka.net/2023/10/03/a-video-how-does-starlink-s... Of course the gain wouldn't be as nice as when both sides can do the phased array trick but cell phones don't have the same kind of antenna capabilities that Starlink's dish has. This is the relevant bit: https://www.youtube.com/watch?v=qs2QcycggWU&t=1265s https://www.youtube.com/watch?v=qs2QcycggWU&t=1265s I suspect the reason it is text service and not voice is that the phone antenna constraint results in severe bandwidth limitations. And with all that tech working for them I still think it is a small miracle they got this to work.

by xattt 3y ago

jacquesm 3y ago

Well, given that it is pretty much always line-of-sight it has (relatively) low power requirements compared to the distance involved, from you to the satellite you will mostly have to deal with attenuation by water vapor. Also: satellite can do beam steering through phasing shifting multiple antennas without any moving parts. So once a satellite knows you exist it can further reduce the power requirements by focusing on a phone when sending or receiving from that particular phone.

Scoundreller 3y ago
Do the satellite-side phased arraying work that quickly to go to the per-customer level? I figured it would just be used to account for the spinning and moving nature of the satellite.
- jacquesm 3y ago
  The satellite side isn't nearly as power constrained as a cell phone so they don't have to get it that precise. But every dB counts. They hit multiple subscribers at once with the sat side footprint but if an area is nearly empty I don't see why they couldn't keep a particular phone in the centroid (such as in emergency services to uninhabited areas). Likely they will differentiate between populated and less populated areas by allocating more time to a spot to service all of the customers. https://erkansaka.net/2023/10/03/a-video-how-does-starlink-satellite-internet-work/ https://erkansaka.net/2023/10/03/a-video-how-does-starlink-s... Of course the gain wouldn't be as nice as when both sides can do the phased array trick but cell phones don't have the same kind of antenna capabilities that Starlink's dish has. This is the relevant bit: https://www.youtube.com/watch?v=qs2QcycggWU&t=1265s https://www.youtube.com/watch?v=qs2QcycggWU&t=1265s I suspect the reason it is text service and not voice is that the phone antenna constraint results in severe bandwidth limitations. And with all that tech working for them I still think it is a small miracle they got this to work.