5 ms·

Want to emphasize Elon's follow up that this is the peak for a beam, and the beams are very wide, so this is basically only possible in places far from ground b

Want to emphasize Elon's follow up that this is the peak for a beam, and the beams are very wide, so this is basically only possible in places far from ground based networks and probably also requiring the place to be sparse enough to only have the one device in the beam area.

simfree 3y ago
Elon's tweet also doesn't mention upload speed. Download speed isn't very useful when your trying to send a MMS showing where your trapped and it's taking tens of minutes to upload.
- xscott 3y ago
  This hypothetical case of sending a large multimedia message instead of 8 bytes for latitude and longitude and 3 more bytes for the letters "SOS" doesn't seem sincere.
  - deleted 3y ago
    [deleted]
  - huppeldepup 3y ago
    minor fyi. Had to look up how to get lat/long on an iphone without internet access. It’s in the default compass app.
    - plugin-baby 3y ago
      Where? Mine has zero options now - just displays the compass, with the level in the middle.
      - watermelon0 3y ago
        Seems it's not available everywhere, for some reason. > Note: Your coordinates and elevation may not be available in certain countries or regions. https://support.apple.com/en-gb/guide/iphone/iph1ac0b663/ios https://support.apple.com/en-gb/guide/iphone/iph1ac0b663/ios
        plugin-baby 3y ago
        Thanks, this article pointed me in the right direction. Coordinates were missing for me because locations services were disabled for the Compass app.
        Terretta 3y ago
        some reason = GNSS: https://medium.com/@ilyakorogodin/where-is-a-navigation-chip-in-my-iphone-92ab55a61863 https://medium.com/@ilyakorogodin/where-is-a-navigation-chip... Article opens iPhones of several generations since iPhone 3G to discover how they do GNSS positioning.
    - Traubenfuchs 3y ago
      Google Maps and Apple Maps show it when you set a marker. You don‘t need internet.
  - jeroenhd 3y ago
    I would be less worried about bytes and more about the general TCP handshake/acks making it through. You can easily add height, heart rate, and all other kinds of information before you come close to the network overhead. You could also gamble UDP+overhead, but I assume you want some kind of assurance that your SOS made it through. You also need to be able to get a session within the beam. If you're stuck in the middle of a desert you'll be fine, but if you're within range of a minor town you may not be able to get any signal.
    - david-gpu 3y ago
      Not an expert, but my understanding is that SMS text messages don't rely on TCP or UDP. Instead, they use their own protocol called SMPP with an overhead of less than 100B.
  - SergeAx 3y ago
    This hypothetical case, on the other hand, only require two bytes of the reply, with letters "OK".
- 15457345234 3y ago
  [flagged]
- whatshisface 3y ago
  Antennas couple the same both ways.
  - ryandamm 3y ago
    But power doesn’t, right? Happy to be corrected (please, educate me!) but I think this is asymmetric, in practice.
    - deleted 3y ago
      [deleted]
  - arghwhat 3y ago
    That does not guarantee two-way communication. Pick-up patterns, resonance and filtering, power and local environment makes SNR highly asymmetrical. Imagine you focus a high gain antenna dish A at an isotropic antenna B. A will almost exclusively hear B, but B will hear things from all directions, making it harder to single out A. Now, A could use their higher gain to scream louder at B - but that's not always a viable option, and could just peak the frontend of B if done wrong. Different antennas and radio circuits have different selectivity, dictating how they react to nearby noise. A dedicated tranceiver station is often much more selective than consumer devices meant to handle many bands and protocols using a small set of multi-purpose antennas and with space requirements limiting room for radio frontends and filters. The power rating of a dedicated transceiver station may also be quite a bit higher than that of a portable device, adding to the asymmetry. There are also differences in atmospheric effects - primarily reflection and refraction - which for these wavelengths happen in the troposphere. With refraction happening closer to the ground (from the perspective of orbit), that makes for another SNR asymmetry.
- cyberax 3y ago
  To achieve this kind of speed, you need at least around 600kbps at the barest minimum for TCP ACK packets (~50 bytes), assuming that downstream packets are full-frame 1500 bytes.
  - dmitrygr 3y ago
    That’s not really true since one ACK packet can acknowledge multiple RXed data packets.
  - bsdetector 3y ago
    The tweet's 17 Mb/s is UDP down from satellite, so no ack replies from the phone, and 15% packet loss. So it really doesn't say anything about upload speed.
- lallysingh 3y ago
  A map for how to get out, or a video for first aid procedures, or a guide on what's safely edible around you, or other survival information until help can get there can make a big difference.
  - Scoundreller 3y ago
    Those all could be unnecessary with advanced planning
- frankacter 3y ago
  The nuance of this news is that it is a for a standard consumer mobile device. It is not intended to replace coverage in areas where telcos exist, rather to supplement in times of spotty coverage or emergencies. >@Elon: This service works in partnership with wireless providers, like what @SpaceX and @TMobile announced. In your scenario you would likely be sending text/sms based communication as a primary priority (ie. coordinates, instructions) with MMS as a secondary luxury. If you are permanently or frequently in an area without telco service you would want to make use of specialized hardware which is optimized for starlink communication. For example, here is video of Elon using starlink for video conferencing which demonstrates not only high upload speeds, but also quick swapping between satellites without disconnect. https://youtu.be/tKqJ5-kkUGk?si=RVilCEke7J3zXoQK&t=367 https://youtu.be/tKqJ5-kkUGk?si=RVilCEke7J3zXoQK&t=367
londons_explore 3y ago
If future satellites have fold out antennas that are 45 meters diameter, spot sizes of half a mile are possible. With that, service will make sense everywhere except urban areas. 45 meter fold out antennas are very possible. Imagine you screen print antenna wires onto a mylar sheet, then double up the sheet and seal the edges to make it like a large airbed. Then, when in space, inflate it.
- stavros 3y ago
  I don't think it's very easy to find air in space, though.
  - londons_explore 3y ago
    Doesn't matter. An airbed will hold its shape with just 0.1 psi of pressure, and that works out to only 0.6 kg of compressed gas for the whole thing. Once inflated, there are no forces causing it to fold up again, so it doesn't matter if the gas leaks out of holes after years.
    - jdjdjdjrgrgh 3y ago
      Gravity -- it is within the earths gravity well, this force still applies. Thrusters -- satellites have thrusters to keep it in orbit and to avoid obstacles. Thus losing pressure will cause the inflatable to lose shape.
      - londons_explore 3y ago
        Gravity is effectively nil on a satellite - the satellite is within the gravity well, yes, but is constantly falling in a parabolic path, so doesn't feel any gravity. The total forces experienced due to gravity and related forces will be nano-newtons, so irrelevant. They are dwarfed by the drag force. Thrusters are ion drive thrusters, so have typical forces of 2 milliNewtons (0.2 grams-force). I don't think 2 millinewtons will be sufficient to fold an airbed-like structure, even with 0 internal pressure. (imagine a fly lands on a plastic bag... the fly isn't heavy enough to flatten the bag, even though the bag has no internal structure - a fly is about 0.2 grams).
numpad0 3y ago
17Mbps UDP downlink to standard smartphones. Half a dozen sqkm/sqmi minimum cell size. Analog modem equivalent uplink theoretically possible. That's DVB. That's an executive summary for a digital TV standard.
- chrisjc 3y ago
  Not sure if I entire understand what you're saying. Do you mean to suggest this would work well for digital video broadcasting (or equivalent to it)? If so, this is what I have been theorizing as a potential future step for Starlink. Once they get the hardware costs down or offer basic versions that are good enough to receive a multicast signal and limited uplink (basic stuff like authentication, etc), they could start providing an equivalent to DirectTV or Cable TV. I'm making the assumption that multi-casting a set of entertainment channels would be relatively inexpensive, and putting aside the question about the value of non-on-demand content for the moment... This would create competition for incumbents and more options for the consumer. Perhaps more importantly for Musk, this would give him the ability to create a media platform that won't be inhibited/constrained/censored by what he and his peers refer to as "legacy media". His recent actions/behavior (twitter, disney lawsuit/buyout, Murdoch/Tucker/Fox relationships, etc) suggest to me that this is his plan. Whether or not you like him or think he and his companies deserve it, it's pretty obvious that they are being targeted by big-media and politicians, and constantly criticized and attacked. Antisemitism, Tesla shorting and "recall" news 24/7 , bankrupting Twitter, Starship failures, and so on... He has FU money and it's obviously personal to him (Disney lawsuit), so why not?

simfree 3y ago

Elon's tweet also doesn't mention upload speed. Download speed isn't very useful when your trying to send a MMS showing where your trapped and it's taking tens of minutes to upload.

xscott 3y ago
This hypothetical case of sending a large multimedia message instead of 8 bytes for latitude and longitude and 3 more bytes for the letters "SOS" doesn't seem sincere.
- deleted 3y ago
  [deleted]
- huppeldepup 3y ago
  minor fyi. Had to look up how to get lat/long on an iphone without internet access. It’s in the default compass app.
  - plugin-baby 3y ago
    Where? Mine has zero options now - just displays the compass, with the level in the middle.
    - watermelon0 3y ago
      Seems it's not available everywhere, for some reason. > Note: Your coordinates and elevation may not be available in certain countries or regions. https://support.apple.com/en-gb/guide/iphone/iph1ac0b663/ios https://support.apple.com/en-gb/guide/iphone/iph1ac0b663/ios
      - plugin-baby 3y ago
        Thanks, this article pointed me in the right direction. Coordinates were missing for me because locations services were disabled for the Compass app.
      - Terretta 3y ago
        some reason = GNSS: https://medium.com/@ilyakorogodin/where-is-a-navigation-chip-in-my-iphone-92ab55a61863 https://medium.com/@ilyakorogodin/where-is-a-navigation-chip... Article opens iPhones of several generations since iPhone 3G to discover how they do GNSS positioning.
  - Traubenfuchs 3y ago
    Google Maps and Apple Maps show it when you set a marker. You don‘t need internet.
- jeroenhd 3y ago
  I would be less worried about bytes and more about the general TCP handshake/acks making it through. You can easily add height, heart rate, and all other kinds of information before you come close to the network overhead. You could also gamble UDP+overhead, but I assume you want some kind of assurance that your SOS made it through. You also need to be able to get a session within the beam. If you're stuck in the middle of a desert you'll be fine, but if you're within range of a minor town you may not be able to get any signal.
  - david-gpu 3y ago
    Not an expert, but my understanding is that SMS text messages don't rely on TCP or UDP. Instead, they use their own protocol called SMPP with an overhead of less than 100B.
- SergeAx 3y ago
  This hypothetical case, on the other hand, only require two bytes of the reply, with letters "OK".
15457345234 3y ago
[flagged]
whatshisface 3y ago
Antennas couple the same both ways.
- ryandamm 3y ago
  But power doesn’t, right? Happy to be corrected (please, educate me!) but I think this is asymmetric, in practice.
  - deleted 3y ago
    [deleted]
- arghwhat 3y ago
  That does not guarantee two-way communication. Pick-up patterns, resonance and filtering, power and local environment makes SNR highly asymmetrical. Imagine you focus a high gain antenna dish A at an isotropic antenna B. A will almost exclusively hear B, but B will hear things from all directions, making it harder to single out A. Now, A could use their higher gain to scream louder at B - but that's not always a viable option, and could just peak the frontend of B if done wrong. Different antennas and radio circuits have different selectivity, dictating how they react to nearby noise. A dedicated tranceiver station is often much more selective than consumer devices meant to handle many bands and protocols using a small set of multi-purpose antennas and with space requirements limiting room for radio frontends and filters. The power rating of a dedicated transceiver station may also be quite a bit higher than that of a portable device, adding to the asymmetry. There are also differences in atmospheric effects - primarily reflection and refraction - which for these wavelengths happen in the troposphere. With refraction happening closer to the ground (from the perspective of orbit), that makes for another SNR asymmetry.
cyberax 3y ago
To achieve this kind of speed, you need at least around 600kbps at the barest minimum for TCP ACK packets (~50 bytes), assuming that downstream packets are full-frame 1500 bytes.
- dmitrygr 3y ago
  That’s not really true since one ACK packet can acknowledge multiple RXed data packets.
- bsdetector 3y ago
  The tweet's 17 Mb/s is UDP down from satellite, so no ack replies from the phone, and 15% packet loss. So it really doesn't say anything about upload speed.
lallysingh 3y ago
A map for how to get out, or a video for first aid procedures, or a guide on what's safely edible around you, or other survival information until help can get there can make a big difference.
- Scoundreller 3y ago
  Those all could be unnecessary with advanced planning
frankacter 3y ago
The nuance of this news is that it is a for a standard consumer mobile device. It is not intended to replace coverage in areas where telcos exist, rather to supplement in times of spotty coverage or emergencies. >@Elon: This service works in partnership with wireless providers, like what @SpaceX and @TMobile announced. In your scenario you would likely be sending text/sms based communication as a primary priority (ie. coordinates, instructions) with MMS as a secondary luxury. If you are permanently or frequently in an area without telco service you would want to make use of specialized hardware which is optimized for starlink communication. For example, here is video of Elon using starlink for video conferencing which demonstrates not only high upload speeds, but also quick swapping between satellites without disconnect. https://youtu.be/tKqJ5-kkUGk?si=RVilCEke7J3zXoQK&t=367 https://youtu.be/tKqJ5-kkUGk?si=RVilCEke7J3zXoQK&t=367

londons_explore 3y ago

If future satellites have fold out antennas that are 45 meters diameter, spot sizes of half a mile are possible. With that, service will make sense everywhere except urban areas. 45 meter fold out antennas are very possible. Imagine you screen print antenna wires onto a mylar sheet, then double up the sheet and seal the edges to make it like a large airbed. Then, when in space, inflate it.

stavros 3y ago
I don't think it's very easy to find air in space, though.
- londons_explore 3y ago
  Doesn't matter. An airbed will hold its shape with just 0.1 psi of pressure, and that works out to only 0.6 kg of compressed gas for the whole thing. Once inflated, there are no forces causing it to fold up again, so it doesn't matter if the gas leaks out of holes after years.
  - jdjdjdjrgrgh 3y ago
    Gravity -- it is within the earths gravity well, this force still applies. Thrusters -- satellites have thrusters to keep it in orbit and to avoid obstacles. Thus losing pressure will cause the inflatable to lose shape.
    - londons_explore 3y ago
      Gravity is effectively nil on a satellite - the satellite is within the gravity well, yes, but is constantly falling in a parabolic path, so doesn't feel any gravity. The total forces experienced due to gravity and related forces will be nano-newtons, so irrelevant. They are dwarfed by the drag force. Thrusters are ion drive thrusters, so have typical forces of 2 milliNewtons (0.2 grams-force). I don't think 2 millinewtons will be sufficient to fold an airbed-like structure, even with 0 internal pressure. (imagine a fly lands on a plastic bag... the fly isn't heavy enough to flatten the bag, even though the bag has no internal structure - a fly is about 0.2 grams).

numpad0 3y ago

17Mbps UDP downlink to standard smartphones. Half a dozen sqkm/sqmi minimum cell size. Analog modem equivalent uplink theoretically possible. That's DVB. That's an executive summary for a digital TV standard.

chrisjc 3y ago
Not sure if I entire understand what you're saying. Do you mean to suggest this would work well for digital video broadcasting (or equivalent to it)? If so, this is what I have been theorizing as a potential future step for Starlink. Once they get the hardware costs down or offer basic versions that are good enough to receive a multicast signal and limited uplink (basic stuff like authentication, etc), they could start providing an equivalent to DirectTV or Cable TV. I'm making the assumption that multi-casting a set of entertainment channels would be relatively inexpensive, and putting aside the question about the value of non-on-demand content for the moment... This would create competition for incumbents and more options for the consumer. Perhaps more importantly for Musk, this would give him the ability to create a media platform that won't be inhibited/constrained/censored by what he and his peers refer to as "legacy media". His recent actions/behavior (twitter, disney lawsuit/buyout, Murdoch/Tucker/Fox relationships, etc) suggest to me that this is his plan. Whether or not you like him or think he and his companies deserve it, it's pretty obvious that they are being targeted by big-media and politicians, and constantly criticized and attacked. Antisemitism, Tesla shorting and "recall" news 24/7 , bankrupting Twitter, Starship failures, and so on... He has FU money and it's obviously personal to him (Disney lawsuit), so why not?