5 ms·

FWIW that is what Starlink has been saying themselves. Their operations have always been linked to cheaper launches. My opinion is that it is easy to get side t

FWIW that is what Starlink has been saying themselves. Their operations have always been linked to cheaper launches. My opinion is that it is easy to get side tracked when your leader gets stuck in political activism.

cozzyd 4y ago
Do cheap launches help when spectral bandwidth over an area is going to be the true limitation? Starlink's problem is going to be that most profitable areas are better served by terrestrial LTE/5G, leaving only truly remote areas that are low density enough. But not many people live there...
- mlyle 4y ago
  > Do cheap launches help when spectral bandwidth over an area is going to be the true limitation? Spectral bandwidth doesn't matter so much with beamforming with reasonably narrow beams. At least not until you get to a lot of satellites overhead at once. Dishy probably obtains a beam ~3 degrees wide; there's a lot of 3x3 degree sectors in the sky. Similarly, the ground "cells" are 300 sq km; there's a lot of these in view of the satellite. > Starlink's problem is going to be that most profitable areas are better served by terrestrial LTE/5G Yup, for the most part I agree. Still, there is a pretty large rural population.
  - shaklee3 4y ago
    bandwidth matters a lot. it's why SpaceX pays so much on legal fees for fcc filings
    - mlyle 4y ago
      > bandwidth matters a lot. Sure, how much data you can exchange per satellite is roughly proportional to the bandwidth. Increasing bandwidth or increasing satellites increases data rate. > it's why SpaceX pays so much on legal fees for fcc filings Note that a whole lot of the paper that goes to the FCC relates to the FCC's statutory authority over space debris and constellation licensing.
      - shaklee3 4y ago
        they have spent an immense amount of money and time on fcc filings for spectrum. this is a mixture of asking for spectrum, proving they're not interfering, and trying to beat kuiper and others to market.
        mlyle 4y ago
        > they have spent an immense amount of money and time on fcc filings for spectrum. Well, sure. It has a multiplicative effect with number of satellites on throughput. Not to mention the proxy warfare they've endured from other constellation vendors through the FCC. The big point which I responded to was there was a claim that adding more satellites doesn't add throughput ("Do cheap launches help")-- that one could be purely spectrum limited and not benefit from additional satellites. Directional antennas make this not true for any reasonable number of satellites.
  - cozzyd 4y ago
    well 3 degrees wide means at best ~28 square degrees on the sky (pi * 3 * 3). But the problem is the other way. It looks like Starlink has 7 GHz total downlink bandwidth from satellite to customers. A cell may be ~300 sq km, but no way you can pipe all that bandwidth in adjacent cells due to interference (or... if you did, you'd probably lose in spectral efficiency). If we assume something like 10 Gbps/cell total downlink bandwidth (based on two polarizations, 1/4 the total bandwidth and 3 bits/Hz efficiency), then you can maybe serve... 500 people / cell reasonably? How many people live in places with fewer than a few people/km^2? Only Alaska averages below that in the US.
    - mlyle 4y ago
      > well 3 degrees wide means at best ~28 square degrees on the sky (pi * 3 * 3). If you use a diameter for a circle area, you need to divide by 4, to get like ~7. I was just going to do 3*3 = 9. > It looks like Starlink has 7 GHz total downlink bandwidth from satellite to customers. A cell may be ~300 sq km, but no way you can pipe all that bandwidth in adjacent cells due to interference Both the downlink and the uplink are directional. Yes, there's some power lost in side lobes, but.. So, if you have multiple satellites overhead, you can have a mosaic pattern where satellite A illuminates a hex, and then other satellites illuminate its neighbors. And even though some energy spills over, it's strongly rejected by the receivers because it's coming from the completely wrong direction. > How many people live in places with fewer than a few people/km^2? In addition to the incorrect pessimism about downlink bandwidth (also, one should expect ~5bits/Hz)... You're not taking into account any reasonable capacity factor, and you're assuming each service is one person. You're also assuming that you sell through to 100% of the populace and there's no one in the cell served by other technologies. If 95% of a suburban area can get FTTH, cable, or reasonable LTE, that still leaves 5% as possible customers for Starlink to fill in. > Only Alaska averages below that in the US. OK, but people are concentrated into cities, leaving a whole lot of land area with concentrations below this even in states with much higher average population density.
      - shaklee3 4y ago
        5bps/Hz is way overestimating their spectral efficiency.
- marcosdumay 4y ago
  > Do cheap launches help when spectral bandwidth over an area is going to be the true limitation? I don't get the question. Do costs matter when revenue is limited? Of course they matter. They matter even more the more limited is the potential revenue.

cozzyd 4y ago

Do cheap launches help when spectral bandwidth over an area is going to be the true limitation? Starlink's problem is going to be that most profitable areas are better served by terrestrial LTE/5G, leaving only truly remote areas that are low density enough. But not many people live there...

mlyle 4y ago
> Do cheap launches help when spectral bandwidth over an area is going to be the true limitation? Spectral bandwidth doesn't matter so much with beamforming with reasonably narrow beams. At least not until you get to a lot of satellites overhead at once. Dishy probably obtains a beam ~3 degrees wide; there's a lot of 3x3 degree sectors in the sky. Similarly, the ground "cells" are 300 sq km; there's a lot of these in view of the satellite. > Starlink's problem is going to be that most profitable areas are better served by terrestrial LTE/5G Yup, for the most part I agree. Still, there is a pretty large rural population.
- shaklee3 4y ago
  bandwidth matters a lot. it's why SpaceX pays so much on legal fees for fcc filings
  - mlyle 4y ago
    > bandwidth matters a lot. Sure, how much data you can exchange per satellite is roughly proportional to the bandwidth. Increasing bandwidth or increasing satellites increases data rate. > it's why SpaceX pays so much on legal fees for fcc filings Note that a whole lot of the paper that goes to the FCC relates to the FCC's statutory authority over space debris and constellation licensing.
    - shaklee3 4y ago
      they have spent an immense amount of money and time on fcc filings for spectrum. this is a mixture of asking for spectrum, proving they're not interfering, and trying to beat kuiper and others to market.
      - mlyle 4y ago
        > they have spent an immense amount of money and time on fcc filings for spectrum. Well, sure. It has a multiplicative effect with number of satellites on throughput. Not to mention the proxy warfare they've endured from other constellation vendors through the FCC. The big point which I responded to was there was a claim that adding more satellites doesn't add throughput ("Do cheap launches help")-- that one could be purely spectrum limited and not benefit from additional satellites. Directional antennas make this not true for any reasonable number of satellites.
- cozzyd 4y ago
  well 3 degrees wide means at best ~28 square degrees on the sky (pi * 3 * 3). But the problem is the other way. It looks like Starlink has 7 GHz total downlink bandwidth from satellite to customers. A cell may be ~300 sq km, but no way you can pipe all that bandwidth in adjacent cells due to interference (or... if you did, you'd probably lose in spectral efficiency). If we assume something like 10 Gbps/cell total downlink bandwidth (based on two polarizations, 1/4 the total bandwidth and 3 bits/Hz efficiency), then you can maybe serve... 500 people / cell reasonably? How many people live in places with fewer than a few people/km^2? Only Alaska averages below that in the US.
  - mlyle 4y ago
    > well 3 degrees wide means at best ~28 square degrees on the sky (pi * 3 * 3). If you use a diameter for a circle area, you need to divide by 4, to get like ~7. I was just going to do 3*3 = 9. > It looks like Starlink has 7 GHz total downlink bandwidth from satellite to customers. A cell may be ~300 sq km, but no way you can pipe all that bandwidth in adjacent cells due to interference Both the downlink and the uplink are directional. Yes, there's some power lost in side lobes, but.. So, if you have multiple satellites overhead, you can have a mosaic pattern where satellite A illuminates a hex, and then other satellites illuminate its neighbors. And even though some energy spills over, it's strongly rejected by the receivers because it's coming from the completely wrong direction. > How many people live in places with fewer than a few people/km^2? In addition to the incorrect pessimism about downlink bandwidth (also, one should expect ~5bits/Hz)... You're not taking into account any reasonable capacity factor, and you're assuming each service is one person. You're also assuming that you sell through to 100% of the populace and there's no one in the cell served by other technologies. If 95% of a suburban area can get FTTH, cable, or reasonable LTE, that still leaves 5% as possible customers for Starlink to fill in. > Only Alaska averages below that in the US. OK, but people are concentrated into cities, leaving a whole lot of land area with concentrations below this even in states with much higher average population density.
    - shaklee3 4y ago
      5bps/Hz is way overestimating their spectral efficiency.
marcosdumay 4y ago
> Do cheap launches help when spectral bandwidth over an area is going to be the true limitation? I don't get the question. Do costs matter when revenue is limited? Of course they matter. They matter even more the more limited is the potential revenue.