5 ms·

Huh, I wonder how they manage to pick up the tiny amount of RF energy a normal phone can output from that far away, and through the noise of literally millions

Huh, I wonder how they manage to pick up the tiny amount of RF energy a normal phone can output from that far away, and through the noise of literally millions of other phones in the satellite's field of view. Gotta be some real weird RF voodoo happening in there.

dmitrygr 4y ago
Well, so far they only promised to. So, probably it’ll be done the same way that Teslas could self drive, across the county, unassisted in 2017
- daydream 4y ago
  > Well, so far they only promised to. Apple’s solution works today. Consumers are using it. This is mentioned in the article.
  - deleted 4y ago
    [deleted]
  - pests 4y ago
    Apple's solution is making use of special features in the radio package. The post states unmodified phones.
    - bee_rider 4y ago
      Still, the fact that Apple has figured out the weird RF voodoo already makes it seem like a less ridiculous proposition.
      - pests 4y ago
        Qualcomm is the one who has figured out the weird RF voodoo you speak of. Apple is just consuming that.
        markus_zhang 4y ago
        Is there any tech manual out there? Would love to see how it works.
      - tshaddox 4y ago
        I always assumed the main thing with satellite messengers was that they transmit with much higher power. Not that such a system is easy to design, but the “voodoo” mentioned previously was more about achieving compatibility with an existing RF system at much longer ranges than the system was designed for.
      - shaklee3 4y ago
        it's not rf voodoo. it's a highly spread signal at an extremely low nitrate. this has been common for communications satellites for a very long time.
  - kalupa 4y ago
    except the article mentions specifically that Apple is partnered with Globalstar, not Starlink, for their emergency services functionality
    - la64710 4y ago
      And except that it actually saved someone’s life
  - spookthesunset 4y ago
    Apples solution is in SOS emergency situations only. It is extremely limited in what you can transmit—which near as I can tell is just a well defined message format.
  - makeitdouble 4y ago
    Apple’s solution is to have you find the signal and manually point to it to send a very small payload on a very slow link. If we’re looking for existing technology, current actually working GPS phones would be a better showcase of what’s possible.
    - bombolo 4y ago
      You know how slow unassisted GPS is?
- martyvis 4y ago
  It's strange that you think that this is so unachievable yet we have things like Bluetooth, WiFi, LoRa and regular cell phone all working with relatively tiny amounts of power and discriminating from the noise generated by other nonparticipants. This would amaze anyone from before the 70s.
  - pontilanda 4y ago
    What? My wifi barely reaches the other side of my room with a wall in between, how am I supposed to think 350 miles is within reason? Even with clear sky, your signal to a tower an order of magnitude closer would be unusable. If you look at apple’s latest feature, even them, with specific hardware probably, requires minutes of open-sky pointing directly at the closest satellite, to transmit mere bytes of data. That tells me that if your phone is just hanging in your pocket, indoors, with a 5G nearby, it’s not going to reach the satellite at in any shape or form.
    - martyvis 4y ago
      I know nothing of your own situation, but having personally deployed fully working and operational WiFi for a 10000 plus seat stadium, various other campuses, but also seeing cell phones work in your pocket moving in a car or in a big city shopping centre is amazing. Even the Starlink stuff that is already deployed. Anyway let's wait and see - I'm pretty sure T-Mobile wouldn't have signed on for something that is just a pipedream
      - dmitrygr 4y ago
        > I'm pretty sure T-Mobile wouldn't have signed on for something that is just a pipedream Las Vegas and a few other cities did, from the same salesman: https://www.wsj.com/articles/elon-musk-boring-company-tunnel-traffic-11669658396 https://www.wsj.com/articles/elon-musk-boring-company-tunnel...
      - pontilanda 4y ago
        > This would amaze anyone from before the 70s. I'm not saying that it's impossible, I'm just pointing out your smugness at the fact that it's not common knowledge. > the Starlink stuff You mean the stuff that requires a large, hot disc on your roof and therefore not in your pocket? Are we talking about the same things there? > I'm pretty sure T-Mobile wouldn't have signed You trust big companies too much, they make mistakes all the time.
midoridensha 4y ago
I studied a little of RF engineering in college. It just seemed like a black art to me.
- willnonya 4y ago
  Money well spent eh
sgtnoodle 4y ago
Cell phones can supposedly connect to towers up to 25 miles away (presumably at the slowest supported data rate.) Starlink is about 350 miles up. Let's round up to 400 to allow for satellites not being directly overhead. That's 2^4 times farther away, or 24dB of signal difference. It seems like a sufficiently fancy phased antenna array on the satellite could compensate for that. Also, the atmosphere is 99% gone at 20 miles up, so that probably helps. Also, with the goal of only supporting SMS, a modern software defined radio chipset could probably be made to use an incredibly low data rate that adds more signal margin than currently used by any cell network.
- snovv_crash 4y ago
  I didn't realise that 4G/5G could connect to receivers that far away. From memory, the maximum Timing Advance in 2G corresponded to ~25km. After that the phones won't get ACKs fast enough due to speed of light and will assume that the response isn't for them. WiFi has similar limits, but much shorter. I know some usecases of WiFi transceivers with longer distances (~5km) which required tweaked firmware that wasn't technically wifi-compliant, to have longer receive windows.
  - shenberg 4y ago
    Even in 2G you have special cells that allocate two+ adjacent time-slots for a channel and so can effectively double the max range at the cost of serving less concurrent clients. This is used in sparsely populated regions (think remote highways etc). It's not a physical, the-signal-can't-reach issue.
morcheeba 4y ago
You are correct - two things happening here: 1. Picking up RF energy from far away. This is the easy part - cell phone antennas are already a big compromise and can be improved on if you increase size or cost. Instead of omni-directional antennas and low-power amplifiers, a directional antenna and low noise amp will work wonders. Cell phones already have extra power to get through buildings and trees; in this case that power would be used to go extra distance (because there won't be these obstacles). 2. Many users seen at once. Each beam is only a 15-mile-diameter circle. In the really remote areas where this coverage would be needed, I don't suspect that there would be too many cell phones - maybe a few hundred at most. http://www.satmagazine.com/story.php?number=1026762698 http://www.satmagazine.com/story.php?number=1026762698
- fulafel 4y ago
  There is no mention in the article of using external antennas with the existing phones.
TheSpiceIsLife 4y ago
Can we still detect the Voyager probe signals?

dmitrygr 4y ago

Well, so far they only promised to. So, probably it’ll be done the same way that Teslas could self drive, across the county, unassisted in 2017

daydream 4y ago
> Well, so far they only promised to. Apple’s solution works today. Consumers are using it. This is mentioned in the article.
- deleted 4y ago
  [deleted]
- pests 4y ago
  Apple's solution is making use of special features in the radio package. The post states unmodified phones.
  - bee_rider 4y ago
    Still, the fact that Apple has figured out the weird RF voodoo already makes it seem like a less ridiculous proposition.
    - pests 4y ago
      Qualcomm is the one who has figured out the weird RF voodoo you speak of. Apple is just consuming that.
      - markus_zhang 4y ago
        Is there any tech manual out there? Would love to see how it works.
    - tshaddox 4y ago
      I always assumed the main thing with satellite messengers was that they transmit with much higher power. Not that such a system is easy to design, but the “voodoo” mentioned previously was more about achieving compatibility with an existing RF system at much longer ranges than the system was designed for.
    - shaklee3 4y ago
      it's not rf voodoo. it's a highly spread signal at an extremely low nitrate. this has been common for communications satellites for a very long time.
- kalupa 4y ago
  except the article mentions specifically that Apple is partnered with Globalstar, not Starlink, for their emergency services functionality
  - la64710 4y ago
    And except that it actually saved someone’s life
- spookthesunset 4y ago
  Apples solution is in SOS emergency situations only. It is extremely limited in what you can transmit—which near as I can tell is just a well defined message format.
- makeitdouble 4y ago
  Apple’s solution is to have you find the signal and manually point to it to send a very small payload on a very slow link. If we’re looking for existing technology, current actually working GPS phones would be a better showcase of what’s possible.
  - bombolo 4y ago
    You know how slow unassisted GPS is?
martyvis 4y ago
It's strange that you think that this is so unachievable yet we have things like Bluetooth, WiFi, LoRa and regular cell phone all working with relatively tiny amounts of power and discriminating from the noise generated by other nonparticipants. This would amaze anyone from before the 70s.
- pontilanda 4y ago
  What? My wifi barely reaches the other side of my room with a wall in between, how am I supposed to think 350 miles is within reason? Even with clear sky, your signal to a tower an order of magnitude closer would be unusable. If you look at apple’s latest feature, even them, with specific hardware probably, requires minutes of open-sky pointing directly at the closest satellite, to transmit mere bytes of data. That tells me that if your phone is just hanging in your pocket, indoors, with a 5G nearby, it’s not going to reach the satellite at in any shape or form.
  - martyvis 4y ago
    I know nothing of your own situation, but having personally deployed fully working and operational WiFi for a 10000 plus seat stadium, various other campuses, but also seeing cell phones work in your pocket moving in a car or in a big city shopping centre is amazing. Even the Starlink stuff that is already deployed. Anyway let's wait and see - I'm pretty sure T-Mobile wouldn't have signed on for something that is just a pipedream
    - dmitrygr 4y ago
      > I'm pretty sure T-Mobile wouldn't have signed on for something that is just a pipedream Las Vegas and a few other cities did, from the same salesman: https://www.wsj.com/articles/elon-musk-boring-company-tunnel-traffic-11669658396 https://www.wsj.com/articles/elon-musk-boring-company-tunnel...
    - pontilanda 4y ago
      > This would amaze anyone from before the 70s. I'm not saying that it's impossible, I'm just pointing out your smugness at the fact that it's not common knowledge. > the Starlink stuff You mean the stuff that requires a large, hot disc on your roof and therefore not in your pocket? Are we talking about the same things there? > I'm pretty sure T-Mobile wouldn't have signed You trust big companies too much, they make mistakes all the time.

midoridensha 4y ago

I studied a little of RF engineering in college. It just seemed like a black art to me.

willnonya 4y ago
Money well spent eh

sgtnoodle 4y ago

Cell phones can supposedly connect to towers up to 25 miles away (presumably at the slowest supported data rate.) Starlink is about 350 miles up. Let's round up to 400 to allow for satellites not being directly overhead. That's 2^4 times farther away, or 24dB of signal difference. It seems like a sufficiently fancy phased antenna array on the satellite could compensate for that. Also, the atmosphere is 99% gone at 20 miles up, so that probably helps. Also, with the goal of only supporting SMS, a modern software defined radio chipset could probably be made to use an incredibly low data rate that adds more signal margin than currently used by any cell network.

snovv_crash 4y ago
I didn't realise that 4G/5G could connect to receivers that far away. From memory, the maximum Timing Advance in 2G corresponded to ~25km. After that the phones won't get ACKs fast enough due to speed of light and will assume that the response isn't for them. WiFi has similar limits, but much shorter. I know some usecases of WiFi transceivers with longer distances (~5km) which required tweaked firmware that wasn't technically wifi-compliant, to have longer receive windows.
- shenberg 4y ago
  Even in 2G you have special cells that allocate two+ adjacent time-slots for a channel and so can effectively double the max range at the cost of serving less concurrent clients. This is used in sparsely populated regions (think remote highways etc). It's not a physical, the-signal-can't-reach issue.

morcheeba 4y ago

You are correct - two things happening here: 1. Picking up RF energy from far away. This is the easy part - cell phone antennas are already a big compromise and can be improved on if you increase size or cost. Instead of omni-directional antennas and low-power amplifiers, a directional antenna and low noise amp will work wonders. Cell phones already have extra power to get through buildings and trees; in this case that power would be used to go extra distance (because there won't be these obstacles). 2. Many users seen at once. Each beam is only a 15-mile-diameter circle. In the really remote areas where this coverage would be needed, I don't suspect that there would be too many cell phones - maybe a few hundred at most. http://www.satmagazine.com/story.php?number=1026762698 http://www.satmagazine.com/story.php?number=1026762698

fulafel 4y ago
There is no mention in the article of using external antennas with the existing phones.

TheSpiceIsLife 4y ago

Can we still detect the Voyager probe signals?