4 ms·

Iridium was a marvel of engineering no-doubt but Starlink as a constellation is in a different league entirely. They also followed different engineering princi

by jpgvm 4y ago

Iridium was a marvel of engineering no-doubt but Starlink as a constellation is in a different league entirely. They also followed different engineering principles, Iridium was engineered to perfection while Starlink is hacked until it works and paper over the kinks with sheer scale and many iterations. Worth mentioning I have nothing but admiration for the original Iridium constellation, it was decades ahead of it's time, it's just so unfortunate they didn't see that broadband needs were going to dominate communications in time or maybe Motorola in it's original glory would still be around today.

walrus01 4y ago
big difference also is that iridium was designed from the outset to address handheld size customer terminals like an original iridum 9505 phone, starlink is something that needs a considerably larger fixed phased array. rf laws of physics being what they are I don't see a ku/ka-band starlink handheld phone or anything similar to the iridium L/S-band hockey puck sized antennas any time soon. the business model was clearly not the best, as witnessed by its spectacular bankruptcy, and the acquisition by the 2nd corporate incarnation of iridium.
- Robotbeat 4y ago
  Starlink has plenty of room for increasing their antenna size on the satellite size to something that a handheld could use. I was surprised how small the phased array on the sat side is. Increase that to make it similar to the size of the satellite (not counting solar array) and with the larger v2 satellites, and they'd have much more gain (allowing the handheld antenna to be smaller). They essentially already use 5G bandwidth. It'd only work well outside, though.
  - lxgr 4y ago
    Isn‘t part of what allows much hire bandwidths for Starlink due to spatial frequency reuse, which requires mandatory beamforming on both sides of the connection? There are many satellites overhead at any given time (the current LEOs and MEOs usually have just one), so terminals need to be able to limit their gain to a small angle not only for gain reasons. Steering in handheld applications seems very difficult. Of course, they could dedicate parts of their spectrum to "one sided beamforming" and compete with Iridium that way (no idea if the L-band has any other advantages over Ka when used like that).
    - Robotbeat 4y ago
      Modern cellphones with 5G (and wifi, etc) do beamforming already.
      - walrus01 4y ago
        Not in the same way that a flat panel phased array that maintains a fixed angle and aim at the sky can.
        Robotbeat 4y ago
        Actually in exactly the same way. The nice thing about phased arrays is they steer electronically, so you can aim them extremely fast and compensate for any movement. That's how 5G works and that's also how Starlink on moving vehicles works.
        walrus01 4y ago
        a flat panel phased array still has considerably more gain in the direction it's aimed, vs a randomly oriented omnidirectional (physical) antenna in a phone. i can guarantee you starlink doesn't work well when the array elements aren't aimed correctly in the general direction of where the satellites are. the path loss and need for more gain at LEO satellite distance is considerably greater than talking about terrestrial cellphone networks in bands <2500 MHz.
        Robotbeat 4y ago
        5G phones already use a flat panel phased array, just with fewer elements (and less gain, but that can be compensated by using a lot more elements on the satellite side and by operating at much lower bandwidth). And yes, I understand the difference between lower frequencies and higher. 5G can also use lower frequencies but the main bandwidth advantage (over LTE/etc) is in the higher frequency, the mm-wave, roughly 25-50GHz, a frequency band that overlaps that used by the Starlink phased arrays.

by jpgvm 4y ago

walrus01 4y ago

big difference also is that iridium was designed from the outset to address handheld size customer terminals like an original iridum 9505 phone, starlink is something that needs a considerably larger fixed phased array. rf laws of physics being what they are I don't see a ku/ka-band starlink handheld phone or anything similar to the iridium L/S-band hockey puck sized antennas any time soon. the business model was clearly not the best, as witnessed by its spectacular bankruptcy, and the acquisition by the 2nd corporate incarnation of iridium.

Robotbeat 4y ago
Starlink has plenty of room for increasing their antenna size on the satellite size to something that a handheld could use. I was surprised how small the phased array on the sat side is. Increase that to make it similar to the size of the satellite (not counting solar array) and with the larger v2 satellites, and they'd have much more gain (allowing the handheld antenna to be smaller). They essentially already use 5G bandwidth. It'd only work well outside, though.
- lxgr 4y ago
  Isn‘t part of what allows much hire bandwidths for Starlink due to spatial frequency reuse, which requires mandatory beamforming on both sides of the connection? There are many satellites overhead at any given time (the current LEOs and MEOs usually have just one), so terminals need to be able to limit their gain to a small angle not only for gain reasons. Steering in handheld applications seems very difficult. Of course, they could dedicate parts of their spectrum to "one sided beamforming" and compete with Iridium that way (no idea if the L-band has any other advantages over Ka when used like that).
  - Robotbeat 4y ago
    Modern cellphones with 5G (and wifi, etc) do beamforming already.
    - walrus01 4y ago
      Not in the same way that a flat panel phased array that maintains a fixed angle and aim at the sky can.
      - Robotbeat 4y ago
        Actually in exactly the same way. The nice thing about phased arrays is they steer electronically, so you can aim them extremely fast and compensate for any movement. That's how 5G works and that's also how Starlink on moving vehicles works.
        walrus01 4y ago
        a flat panel phased array still has considerably more gain in the direction it's aimed, vs a randomly oriented omnidirectional (physical) antenna in a phone. i can guarantee you starlink doesn't work well when the array elements aren't aimed correctly in the general direction of where the satellites are. the path loss and need for more gain at LEO satellite distance is considerably greater than talking about terrestrial cellphone networks in bands <2500 MHz.
        Robotbeat 4y ago
        5G phones already use a flat panel phased array, just with fewer elements (and less gain, but that can be compensated by using a lot more elements on the satellite side and by operating at much lower bandwidth). And yes, I understand the difference between lower frequencies and higher. 5G can also use lower frequencies but the main bandwidth advantage (over LTE/etc) is in the higher frequency, the mm-wave, roughly 25-50GHz, a frequency band that overlaps that used by the Starlink phased arrays.