6 ms·

What the... is that what's possible with 5G? Amazing, and even days ago I was thinking of satellite smartphone internet as something scifi because of (clearly i

What the... is that what's possible with 5G? Amazing, and even days ago I was thinking of satellite smartphone internet as something scifi because of (clearly incorrect!) complicated antenna requirements.

fragmede 4y ago
Satellite phone Internet previously existed, it's just crazy expensive.
- jupp0r 4y ago
  It’s $10 per month for my Garmin InReach which gives you emergency comms and let’s you upgrade to unlimited SMS and some other stuff for $60. I use it a lot and it’s very reasonable. Runs on Iridium.
  - erikpukinskis 4y ago
    I have a Garmin InReach too, but to say it’s “satellite phone internet” is a stretch. You can send little blips of data. There’s no phone service. Nor is there any internet service.
    - jupp0r 4y ago
      If you read the T-Mobile announcement, that’s exactly what you’ll get. Not saying it’s not great but I think people have the misconception that they’ll have usable satellite internet which is really not happening due to physics.
mlindner 4y ago
<deleted>
- trothamel 4y ago
  It's being transmitted to existing phones, so it's going over 5G, LTE, or both.
shadowgovt 4y ago
Radio's got some crazy physics. So baseline, a modern cell phone can connect to a tower about 45 miles away. Stsrlink satellites orbir about 10 times out from that. They are solving this problem by some very clever phased array technology to be deployed on the satellites themselves, because when it comes to radio, you can often solve the problem of signal reception by boosting either the transmitter or the receiver side of the story. This is how we've kept in touch with the Voyagers all this time. The Voyager radio technology is getting no better, but the technology we can throw at it from a ground station has been out-stripping the loss due to distance and degradation (or at least approximately keeping pace).
- mlindner 4y ago
  > So baseline, a modern cell phone can connect to a tower about 45 miles away. Isn't that primarily because of the Earth's curvature and obstructions/hills?
  - shadowgovt 4y ago
    Good question. I've had a bear of a time sourcing good info on this and would welcome a solid analysis.
    - ac29 4y ago
      Radio horizon is somewhat complex, but 45 miles is not entirely unreasonable from an elevated position. https://en.wikipedia.org/wiki/Line-of-sight_propagation#Radio_horizon https://en.wikipedia.org/wiki/Line-of-sight_propagation#Radi... There could also be timing related constraints that limit max range: radio waves propagate at the speed of light which is fast, but not instant.
      - genewitch 4y ago
        microwaves go about 10% further than the horizon, barring any tropospheric ducting - which cell towers shouldn't, in general. The issue you have with long distances is multipath, which can throw off the complex timing required to have multiple users in realtime on a single radio.
LeoPanthera 4y ago
I think the "complicated antenna requirements" still exist - they've just put the complicated antenna on the satellite, instead of on the phone.
- assttoasstmgr 4y ago
  Yeah that's not how it works. You can't just "put the complicated antenna on the satellite, instead of on the phone" and declare this problem solved. If you believe that I have a bridge to sell you. I'm declaring shenanigans right now on Elon's pitch but what else is new. It makes me sad that this thread is full of (probably) SWEs in a complete froth who took this at face value with little understanding of how antennas work. No, your existing phone will not be able to work on this service, full stop. The issue is not getting signal from the satellite to your phone. That's the easy part - after all, your phone receives GPS signals. Satellites have powerful transmitters and high-gain antennas. Even GPS which is considered extremely low-power has a TX power of around 20-25 watts and EIRP is probably an order of magnitude higher after the antenna (probably enough to turn your eyeballs into Easter eggs if you were standing in front of it). The issue is going the other way. For messaging to work, your phone needs a two-way connection. Your current iPhone/Android handset is simply not designed for satellite communication. "But muh Garmin inReach" ..... have you stared at one and wondered "why can't my iPhone do this"? First, the antenna is the size of a thumb, it looks like a helical antenna to me, which would make sense given that most satellite communications uses something called "circular polarization" to combat things like the Faraday effect. This requires an antenna specifically designed for it. Your iPhone doesn't have one, which means more signal loss. Iridium phones look similar - very Michael Douglas in Wall Street industrial design. Satellite phones and communicators are designed to direct most of the energy upwards towards the sky. Your existing phone does not so you are losing most of the energy in an omnidirectional pattern. Even things like 406 MHz emergency beacons send extremely short message bursts - just a few bytes - the link budget needed to sustain an IP connection (uplink) with an existing handset just isn't there. So I'm expecting Elon to deliver on the magical complicated-super-antenna that works with your existing mobile handset right around the same time he gives us his FSD Cybertruck. Which is to say, never.
  - 4y ago
wongarsu 4y ago
4G/LTE was commonly quoted as 3km range for rural installations (using the 2GHz bands). 5G added 700MHz and 800MHz bands that are quoted as 10-20km achievable range. For typical cell tower heights 20km is about the range where they would sink behind the horizon, so that might be the practical limit here. Starlink satellites are about 330km up, so one order of magnitude further. But they also have basically unobstructed line of sight (if you are under blue sky). Compared to the normal conditions a cell phone has to deal with that might get you a substantial improvement. I think it's plausible that at least some existing phones can do it, with the tiny bandwidth you would expect from a poor signal.
- teraflop 4y ago
  330km is only when the satellite is directly overhead. Starlink's coverage is typically given on the assumption that the satellites may be as low as 25 degrees above the horizon, and at that elevation, the straight-line distance is more like 700km if my math is right.
  - virtuallynathan 4y ago
    None are currently at 330km, and the first shells of v2 will be at 540-570km.
- kibibyte 4y ago
  GPS is a thing, so I can imagine that a phone would be able to receive satellite signals pretty easily. But for transmission, I can't imagine this working without having your phone put a ton of power into sending a powerful enough signal, perhaps more so than how much power you need to passively receive GPS signals in the absence of traditional cell towers?
  - sgtnoodle 4y ago
    It sounds like the data rate is incredibly low. That allows for a lot of signal margin. GPS receivers are sensitive to something like -165dBm. It's probably harder for the satellite to hear from the phone. Especially at a lower frequency like 700Mhz, a phone's tiny antenna is going to be a rather inefficient transmitter. Maybe 5g technology helps by allowing the phone to do some rudimentary beam forming using multiple antennas?
thepasswordis 4y ago
Satellite smartphone internet is still sci fi. This is extremely low bandwidth and intended for sending extremely high latency text chats. Elon said in the presentation that it could be as much as 30 mins between hitting send and the message going through. This competes with existing stuff from existing satellite providers. It’s really really cool, and doesn’t need to be full on smartphone satellite internet to fulfill that coolness!
- gfosco 4y ago
  His 30 minute example was when there are only a few satellites in space. Once many are active, it would allegedly become near-realtime.

fragmede 4y ago

Satellite phone Internet previously existed, it's just crazy expensive.

jupp0r 4y ago
It’s $10 per month for my Garmin InReach which gives you emergency comms and let’s you upgrade to unlimited SMS and some other stuff for $60. I use it a lot and it’s very reasonable. Runs on Iridium.
- erikpukinskis 4y ago
  I have a Garmin InReach too, but to say it’s “satellite phone internet” is a stretch. You can send little blips of data. There’s no phone service. Nor is there any internet service.
  - jupp0r 4y ago
    If you read the T-Mobile announcement, that’s exactly what you’ll get. Not saying it’s not great but I think people have the misconception that they’ll have usable satellite internet which is really not happening due to physics.

mlindner 4y ago

trothamel 4y ago
It's being transmitted to existing phones, so it's going over 5G, LTE, or both.

shadowgovt 4y ago

Radio's got some crazy physics. So baseline, a modern cell phone can connect to a tower about 45 miles away. Stsrlink satellites orbir about 10 times out from that. They are solving this problem by some very clever phased array technology to be deployed on the satellites themselves, because when it comes to radio, you can often solve the problem of signal reception by boosting either the transmitter or the receiver side of the story. This is how we've kept in touch with the Voyagers all this time. The Voyager radio technology is getting no better, but the technology we can throw at it from a ground station has been out-stripping the loss due to distance and degradation (or at least approximately keeping pace).

mlindner 4y ago
> So baseline, a modern cell phone can connect to a tower about 45 miles away. Isn't that primarily because of the Earth's curvature and obstructions/hills?
- shadowgovt 4y ago
  Good question. I've had a bear of a time sourcing good info on this and would welcome a solid analysis.
  - ac29 4y ago
    Radio horizon is somewhat complex, but 45 miles is not entirely unreasonable from an elevated position. https://en.wikipedia.org/wiki/Line-of-sight_propagation#Radio_horizon https://en.wikipedia.org/wiki/Line-of-sight_propagation#Radi... There could also be timing related constraints that limit max range: radio waves propagate at the speed of light which is fast, but not instant.
    - genewitch 4y ago
      microwaves go about 10% further than the horizon, barring any tropospheric ducting - which cell towers shouldn't, in general. The issue you have with long distances is multipath, which can throw off the complex timing required to have multiple users in realtime on a single radio.

LeoPanthera 4y ago

I think the "complicated antenna requirements" still exist - they've just put the complicated antenna on the satellite, instead of on the phone.

assttoasstmgr 4y ago
Yeah that's not how it works. You can't just "put the complicated antenna on the satellite, instead of on the phone" and declare this problem solved. If you believe that I have a bridge to sell you. I'm declaring shenanigans right now on Elon's pitch but what else is new. It makes me sad that this thread is full of (probably) SWEs in a complete froth who took this at face value with little understanding of how antennas work. No, your existing phone will not be able to work on this service, full stop. The issue is not getting signal from the satellite to your phone. That's the easy part - after all, your phone receives GPS signals. Satellites have powerful transmitters and high-gain antennas. Even GPS which is considered extremely low-power has a TX power of around 20-25 watts and EIRP is probably an order of magnitude higher after the antenna (probably enough to turn your eyeballs into Easter eggs if you were standing in front of it). The issue is going the other way. For messaging to work, your phone needs a two-way connection. Your current iPhone/Android handset is simply not designed for satellite communication. "But muh Garmin inReach" ..... have you stared at one and wondered "why can't my iPhone do this"? First, the antenna is the size of a thumb, it looks like a helical antenna to me, which would make sense given that most satellite communications uses something called "circular polarization" to combat things like the Faraday effect. This requires an antenna specifically designed for it. Your iPhone doesn't have one, which means more signal loss. Iridium phones look similar - very Michael Douglas in Wall Street industrial design. Satellite phones and communicators are designed to direct most of the energy upwards towards the sky. Your existing phone does not so you are losing most of the energy in an omnidirectional pattern. Even things like 406 MHz emergency beacons send extremely short message bursts - just a few bytes - the link budget needed to sustain an IP connection (uplink) with an existing handset just isn't there. So I'm expecting Elon to deliver on the magical complicated-super-antenna that works with your existing mobile handset right around the same time he gives us his FSD Cybertruck. Which is to say, never.
- 4y ago

wongarsu 4y ago

4G/LTE was commonly quoted as 3km range for rural installations (using the 2GHz bands). 5G added 700MHz and 800MHz bands that are quoted as 10-20km achievable range. For typical cell tower heights 20km is about the range where they would sink behind the horizon, so that might be the practical limit here. Starlink satellites are about 330km up, so one order of magnitude further. But they also have basically unobstructed line of sight (if you are under blue sky). Compared to the normal conditions a cell phone has to deal with that might get you a substantial improvement. I think it's plausible that at least some existing phones can do it, with the tiny bandwidth you would expect from a poor signal.

teraflop 4y ago
330km is only when the satellite is directly overhead. Starlink's coverage is typically given on the assumption that the satellites may be as low as 25 degrees above the horizon, and at that elevation, the straight-line distance is more like 700km if my math is right.
- virtuallynathan 4y ago
  None are currently at 330km, and the first shells of v2 will be at 540-570km.
kibibyte 4y ago
GPS is a thing, so I can imagine that a phone would be able to receive satellite signals pretty easily. But for transmission, I can't imagine this working without having your phone put a ton of power into sending a powerful enough signal, perhaps more so than how much power you need to passively receive GPS signals in the absence of traditional cell towers?
- sgtnoodle 4y ago
  It sounds like the data rate is incredibly low. That allows for a lot of signal margin. GPS receivers are sensitive to something like -165dBm. It's probably harder for the satellite to hear from the phone. Especially at a lower frequency like 700Mhz, a phone's tiny antenna is going to be a rather inefficient transmitter. Maybe 5g technology helps by allowing the phone to do some rudimentary beam forming using multiple antennas?

thepasswordis 4y ago

Satellite smartphone internet is still sci fi. This is extremely low bandwidth and intended for sending extremely high latency text chats. Elon said in the presentation that it could be as much as 30 mins between hitting send and the message going through. This competes with existing stuff from existing satellite providers. It’s really really cool, and doesn’t need to be full on smartphone satellite internet to fulfill that coolness!

gfosco 4y ago
His 30 minute example was when there are only a few satellites in space. Once many are active, it would allegedly become near-realtime.