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My bet is that the "pizza box" phased array rooftop antenna will evolve into a complete base-station. We know it has a multi-element RF front-end feeding in to

My bet is that the "pizza box" phased array rooftop antenna will evolve into a complete base-station. We know it has a multi-element RF front-end feeding in to massively parallel software defined radio (SDR). Likely available in PoE or wireless variants (solar+batteries+wifi; imagine the MIMO with 100 antenna elements!). SDR is quite interesting because it can track moving satellites, and do simultaneous multipath reconstruction of multiple terrestrial broadcast signals -- digital tlevision, FM/AM/satellite radio, shortwave, etc. No antenna pointing needed, as it's all done in software. After demodulating the carrier the video and audio content is streamed on a local web page available to computers/phones/tablets on the LAN. Existing TVs can be supported via an HDMI or analog (VGA/composite/3.5mm) stick w an RF remote. Optional (or one-time software unlock?) on-board storage for multimedia time-shifting and distributed CDN caching (reducing bandwidth and latency by keeping commonly served duplicate files like js libraries locally). Having a local server also lets them do fun things in the future like transparent LZMA compression, optional ad/telemetry/malware blocking, data pre-caching, smart shared HTTP caching, etc. The inclusion of on-board storage allows data to be sloshed around to best utilize the terrestrial spectrum (broadcast content) and satellite spectrum (multicast content). It's much like Tesla batteries allow energy to be sloshed around to best utilize distributed solar and the utility grid. With proper RF front-end design, support for the diversity of global broadcast standards can added through OTA software updates via satellite. This simplifies hardware into a single "world" model with regional software variants. Easy install, especially with the wireless version (mount on pole, erect, securely fasten, done). Broadcast signal reach and convenience (any device or TV) that beats the pants off of any OTA antenna out there. Convenient access to terrestrial broadcast content w time-shifting takes some of the load from streaming services, so it's a strategic move and not just a "gee wiz" feature they got cheap because of SDR. At $200-300 for the equipment and $50/mo for internet, with a good multimedia time shifting UI, SpaceX would cream every rural data provider out there. Anyway, just the idle dreams of an internet user living in a rural satellite "data desert"...

walrus01 10y ago
I've worked with phased array flat panel antennas used for geostationary Ku and Ka band two way satellite access. Phased array flat panel antennas cannot be purely software steered sufficiently to track a low earth orbit satellite from horizon to horizon. It's not good enough to just put a flat panel phased array facing straight up, you won't have enough gain aimed in the direction where the satellite actually is at any given moment. Assuming a CPE device that measures 1.5'x1.5' to 2'x2' in size, it will still need a motorized azimuth and elevation stepper motor system (or equivalent) to track a LEO satellite. If you're trying to do multi-Mbps data to/from a satellite in bands >10GHz (and probably >18GHz), the path loss through the atmosphere and RF parameters mean that you want as much gain as possible... This is why the most economical solutions for high capacity two way satellite through geostationary transponder capacity involve 1.8 to 3.0 meter size dish antennas. Gain is important. Gain and enough signal over noise ratio that you can do higher order QAMs and not spend half your bitrate on FEC. You could, I suppose, if the antenna system was cheap enough and large enough build a non moving, cone or pyramid shaped antenna covered in phase array segments that could maintain a high bandwidth connection in the >10GHz bands to a moving LEO satellite. But it would be pretty large. edit: for those who are curious and want to see an example of a parabolic (steered) use for moving satellite comms: https://www.google.com/search?q=melco+antenna+mitsubishi&ie=utf-8&oe=utf-8&client=firefox-b https://www.google.com/search?q=melco+antenna+mitsubishi&ie=... http://proceedings.kaconf.org/papers/2015/bsw_4.pdf http://proceedings.kaconf.org/papers/2015/bsw_4.pdf there is also an israeli company which is a competitor to mitsubishi in this space. and a few others. if you watch the weekly FCC filings for new satellite equipment licenses, there's a lot of MELCO antennas flying around on top of mid and large sized jet aircraft.
- manicdee 10y ago
  They will not be tracking any one satellite across the sky, only those of the 4000 best suited to that particular site at that particular time.
  - walrus01 10y ago
    I'm trying to visualize how it might be set up, from the perspective of the satellite... If you're familiar with how an o3b satellite uses numerous relatively focused high-Ka-band spot beams, I'm imagining each of these 4000 satellites doing something similar but with much smaller spot beams and tighter focus (but also the satellite is smaller, lower power and has smaller antennas so less gain). The really curious part is how the satellite to ground trunk link will be accomplished, if they're going to try to build something like a modern version of the satellite-to-satellite links that Iridium satellites use, but at much higher capacities, draining traffic from multiple satellites through whichever one happens to be over a gateway earth station at a particular time. Or perhaps the satellites will be able to do that and also opportunistically connect to operator-owned earth stations when they are in LOS.
- patrickyeon 10y ago
  I hope you don't mind, but I'm interested in talking to you about satellite comms and antennas specifically. You don't have any contact info listed in your profile, but if you'd like to talk you can either hit my personal address listed in my profile, or my planet.com one where my username is patrick.
- schiffern 10y ago
  Thanks, great comment. Mark my words, SpaceX is quietly working toward nothing less than a revolution in global data infrastructure, just as Tesla is working to accelerate a revolution in global energy infrastructure. Sneaking in some software, onboard storage, putting them on all Tesla cars, mesh networking the terrestrial base stations with MIMO links, etc. Cars suddenly become a global peer-to-peer mesh sneakernet. It would be fun if Tesla distributed data via "pulses" between passing cars... (signed high resolution maps? deep learning connectomes? the latest Netflix original series? :D) >Phased array flat panel antennas cannot be purely software steered sufficiently to track a low earth orbit satellite from horizon to horizon. Righto. SpaceX plans to steer the beam down to 40° from the horizon. This also minimized path losses. Drawing from the SpaceX filing: http://i.imgur.com/7zOZ7kr.png http://i.imgur.com/7zOZ7kr.png >All Ku-band downlink spot beams on each SpaceX satellite are independently steerable over the full field of view of the Earth. However, user terminals at the customers’ premises communicate only with satellites at an elevation angle of at least 40 degrees. Consequently, as shown in Figure A.3.1-1 below, each satellite operating at an altitude of 1,150 km will provide service only up to 40.46 degrees away from boresight (nadir), covering an area of about 3.5 million square kilometers (1,060 km radius) source: Figure A.3.1-1 on pp6 of the FCC technical information document, currently 404, via /u/SkywayCheerios https://www.reddit.com/r/spacex/comments/5d9724/spacex_has_filed_for_their_massive_constellation/da2qjj7/ https://www.reddit.com/r/spacex/comments/5d9724/spacex_has_f... https://licensing.fcc.gov/myibfs/download.do?attachment_key=1158350 https://licensing.fcc.gov/myibfs/download.do?attachment_key=... http://webcache.googleusercontent.com/search?q=cache%3Alicensing.fcc.gov%2Fmyibfs%2Fdownload.do%3Fattachment_key%3D1158350 http://webcache.googleusercontent.com/search?q=cache%3Alicen...
dzhiurgis 10y ago
I was thinking about CDN caching too! Imagine this <script src="https://cdn.spacex.com/js/jQuery-1.8.3.min.js" https://cdn.spacex.com/js/jQuery-1.8.3.min.js" />
jasonwatkinspdx 10y ago
> SDR is quite interesting because it can track moving satellites, and do simultaneous multipath reconstruction of multiple terrestrial broadcast signals -- digital tlevision, FM/AM/satellite radio, shortwave, etc. No antenna pointing needed, as it's all done in software. Don't conflate SDR, phased arrays, and MIMO. They're separate things. The latter two can be implemented vi a variety of hardware. State of the art radars tend to use a lot of FPGA's for aperture synthesis, not SDR. SDR also isn't quite the panacea you're presenting. You can't just slap some magic processor in something and then gain access to huge swaths of spectrum. Even highly advanced UWB phased array apertures are limited to around 10:1 bandwidth. Getting up to and past 1 gigasamples per second is difficult even using the prior mentioned pile of very expensive FPGAs. You won't be able to pull in everything from ~100mhz signals to 18ghz signals all in one $300 pizza box on your roof. The spacex device will be much more narrowly targeted.

walrus01 10y ago

I've worked with phased array flat panel antennas used for geostationary Ku and Ka band two way satellite access. Phased array flat panel antennas cannot be purely software steered sufficiently to track a low earth orbit satellite from horizon to horizon. It's not good enough to just put a flat panel phased array facing straight up, you won't have enough gain aimed in the direction where the satellite actually is at any given moment. Assuming a CPE device that measures 1.5'x1.5' to 2'x2' in size, it will still need a motorized azimuth and elevation stepper motor system (or equivalent) to track a LEO satellite. If you're trying to do multi-Mbps data to/from a satellite in bands >10GHz (and probably >18GHz), the path loss through the atmosphere and RF parameters mean that you want as much gain as possible... This is why the most economical solutions for high capacity two way satellite through geostationary transponder capacity involve 1.8 to 3.0 meter size dish antennas. Gain is important. Gain and enough signal over noise ratio that you can do higher order QAMs and not spend half your bitrate on FEC. You could, I suppose, if the antenna system was cheap enough and large enough build a non moving, cone or pyramid shaped antenna covered in phase array segments that could maintain a high bandwidth connection in the >10GHz bands to a moving LEO satellite. But it would be pretty large. edit: for those who are curious and want to see an example of a parabolic (steered) use for moving satellite comms: https://www.google.com/search?q=melco+antenna+mitsubishi&ie=utf-8&oe=utf-8&client=firefox-b https://www.google.com/search?q=melco+antenna+mitsubishi&ie=... http://proceedings.kaconf.org/papers/2015/bsw_4.pdf http://proceedings.kaconf.org/papers/2015/bsw_4.pdf there is also an israeli company which is a competitor to mitsubishi in this space. and a few others. if you watch the weekly FCC filings for new satellite equipment licenses, there's a lot of MELCO antennas flying around on top of mid and large sized jet aircraft.

manicdee 10y ago
They will not be tracking any one satellite across the sky, only those of the 4000 best suited to that particular site at that particular time.
- walrus01 10y ago
  I'm trying to visualize how it might be set up, from the perspective of the satellite... If you're familiar with how an o3b satellite uses numerous relatively focused high-Ka-band spot beams, I'm imagining each of these 4000 satellites doing something similar but with much smaller spot beams and tighter focus (but also the satellite is smaller, lower power and has smaller antennas so less gain). The really curious part is how the satellite to ground trunk link will be accomplished, if they're going to try to build something like a modern version of the satellite-to-satellite links that Iridium satellites use, but at much higher capacities, draining traffic from multiple satellites through whichever one happens to be over a gateway earth station at a particular time. Or perhaps the satellites will be able to do that and also opportunistically connect to operator-owned earth stations when they are in LOS.
patrickyeon 10y ago
I hope you don't mind, but I'm interested in talking to you about satellite comms and antennas specifically. You don't have any contact info listed in your profile, but if you'd like to talk you can either hit my personal address listed in my profile, or my planet.com one where my username is patrick.
schiffern 10y ago
Thanks, great comment. Mark my words, SpaceX is quietly working toward nothing less than a revolution in global data infrastructure, just as Tesla is working to accelerate a revolution in global energy infrastructure. Sneaking in some software, onboard storage, putting them on all Tesla cars, mesh networking the terrestrial base stations with MIMO links, etc. Cars suddenly become a global peer-to-peer mesh sneakernet. It would be fun if Tesla distributed data via "pulses" between passing cars... (signed high resolution maps? deep learning connectomes? the latest Netflix original series? :D) >Phased array flat panel antennas cannot be purely software steered sufficiently to track a low earth orbit satellite from horizon to horizon. Righto. SpaceX plans to steer the beam down to 40° from the horizon. This also minimized path losses. Drawing from the SpaceX filing: http://i.imgur.com/7zOZ7kr.png http://i.imgur.com/7zOZ7kr.png >All Ku-band downlink spot beams on each SpaceX satellite are independently steerable over the full field of view of the Earth. However, user terminals at the customers’ premises communicate only with satellites at an elevation angle of at least 40 degrees. Consequently, as shown in Figure A.3.1-1 below, each satellite operating at an altitude of 1,150 km will provide service only up to 40.46 degrees away from boresight (nadir), covering an area of about 3.5 million square kilometers (1,060 km radius) source: Figure A.3.1-1 on pp6 of the FCC technical information document, currently 404, via /u/SkywayCheerios https://www.reddit.com/r/spacex/comments/5d9724/spacex_has_filed_for_their_massive_constellation/da2qjj7/ https://www.reddit.com/r/spacex/comments/5d9724/spacex_has_f... https://licensing.fcc.gov/myibfs/download.do?attachment_key=1158350 https://licensing.fcc.gov/myibfs/download.do?attachment_key=... http://webcache.googleusercontent.com/search?q=cache%3Alicensing.fcc.gov%2Fmyibfs%2Fdownload.do%3Fattachment_key%3D1158350 http://webcache.googleusercontent.com/search?q=cache%3Alicen...

dzhiurgis 10y ago

I was thinking about CDN caching too! Imagine this <script src="https://cdn.spacex.com/js/jQuery-1.8.3.min.js" https://cdn.spacex.com/js/jQuery-1.8.3.min.js" />

jasonwatkinspdx 10y ago

> SDR is quite interesting because it can track moving satellites, and do simultaneous multipath reconstruction of multiple terrestrial broadcast signals -- digital tlevision, FM/AM/satellite radio, shortwave, etc. No antenna pointing needed, as it's all done in software. Don't conflate SDR, phased arrays, and MIMO. They're separate things. The latter two can be implemented vi a variety of hardware. State of the art radars tend to use a lot of FPGA's for aperture synthesis, not SDR. SDR also isn't quite the panacea you're presenting. You can't just slap some magic processor in something and then gain access to huge swaths of spectrum. Even highly advanced UWB phased array apertures are limited to around 10:1 bandwidth. Getting up to and past 1 gigasamples per second is difficult even using the prior mentioned pile of very expensive FPGAs. You won't be able to pull in everything from ~100mhz signals to 18ghz signals all in one $300 pizza box on your roof. The spacex device will be much more narrowly targeted.