13 ms·
100 Gbps achieved from space to Earth
- JoeAltmaier 4y agoI wonder if re-transmission is the best solution to corrupt blocks. Some students that commuted to school on a train (MIT?) figured out if they transmitted ECC-style blocks combined with RAID-style parity blocks they could instead rebuild corrupt data. It all depends on the kind of corruption. Periodic spikes, white noise, blackouts - different problems need different solutions
- sgtnoodle 4y agoThis is known as "forward error correction". If the nature of the corruption is known and predictable, then you can design a reasonably efficient scheme to mitigate it. Otherwise, I suspect some amount of acknowledgement and retransmission at the MAC layer or above is a good idea. It really depends on the latency of the link, though, and the probability of corruption. If a round-trip delay is larger than a reasonable window size, and corruption is frequent, then FEC would help a lot. It's the only option for one-way comms such as digital broadcast television.
- jpmattia 4y ago> This is known as "forward error correction". Fun factoid: Reed and Solomon were working at MIT Lincoln Laboratory (ie where the OP result is from) when they invented RS codes. ISTR they were also working on satellite comm, in which Lincoln has a long history. [Source: I spent a decade there myself and drank the kool aid.]
- thehappypm 4y agoThat’s super cool. Error correcting codes are truly amazing technology.
- sizzle 4y agoAwesome, what are you up to nowadays? Anything interesting brewing you can share?
- jpmattia 4y agoThese days, most of my time is spent on video encoding and distribution for fun and profit: https://www.centaurdelivery.com https://www.centaurdelivery.com
- MayeulC 4y agoWhich is exactly what Wi-Fi does, adjusting the amount of parity data depending on link loss, to keep retransmissions to a minimal.
- sgtnoodle 4y agoIndeed. It's fun to look at the MCS table for something like 802.11ac. a lot of different rates are actually the same underlying modulation, but with varying amounts of overhead from forward error correction. 802.11 data frames also have an acknowledgement at the MAC layer. The radios dynamically ramp up the MCS rate until packets start dropping, then ramp the rate back down.
- wongarsu 4y agoAnd still, wifi links are among the top sources of packet loss. Without sophisticated forward error correction it would probably be much worse, but it shows that this is not an either-or question. The correct answer is: do both.
- cycomanic 4y agoI think communications theorists would argue that retransmitting is essentially an FEC, and likely a suboptimal one for these links. That said, real-world constrains don't always match up with theory, while modern optical communication makes extensive use of FEC (however RS codes are not used much anymore, in long-haul it's LDPC codes) AFAIK FECs for these type of "intermittent" links are very underdeveloped. Moreover, if the probabilities of long outages is too high, one would need a lot of memory for the FEC which becomes difficult to do in real-time processing (remember we need to process at >100Gb/s).
- sedatk 4y agoYou must have a retransmission mechanism anyway. You can always implement such mechanisms on top of a retransmitting protocol.
- nonameiguess 4y agoUS geointelligence uses error-correcting codes, but beyond that, individual detectors on sensor arrays fail all the time, and you can't go up there to replace them and you don't want to bring down an entire satellite when it still mostly works, so ground processing needs to be robust to missing data anyway. It's fairly straightforward to just interpolate pixels, but the full process is a bit more sophisticated and also involves building overlay layers rating the quality of each pixel, so follow-on processing like object and change detection is able to take into account not just hey, what am I looking at, but also how reliable is each individual part of the scene. To a human looking at the final image, though, you'd never know the difference. I'm assuming most of what this would be used for is imagery collected from space. For whatever reason, other commenters seem to think this is for holding conversations, but it clearly says it's for data from science missions. Even if you were trying to talk to someone on the other end, though, it's rarely that big a deal if part of a word cuts out. That happens all the time with existing ground-based calls or even just two people in a loud room and the human brain knows how to handle it.
- Kuinox 4y agoThat error correction, great video of 3blue1brown explaining how one such algorithm works: https://www.youtube.com/watch?v=X8jsijhllIA https://www.youtube.com/watch?v=X8jsijhllIA
- pclmulqdq 4y agoAnother comment has pointed this out, but Reed-Solomon coding was invented as a method of forward error correction. It was only applied later to storage systems as an "erasure code" because it can detect and correct extremely long runs of bad bits. Comparatively, it can detect and correct many fewer random bad bits.
- wwwtyro 4y agoI'm curious how many households this would support, taking into account usage distributions over time. Would this be sufficient for a medium city? A large town?
- jaywalk 4y agoZero households. This system is meant to communicate with one ground station at a time, and only for a very brief window. It's really only good for downlinking bulk data that was collected by the satellite, not Internet access.
- nix23 4y agoYou forgott latency...not usable for rt communication.
- emkoemko 4y agohow so? stock markets are using lasers to reduce trading latency vs everything else available so what do you mean not usable for real time communication?
- govg 4y agoThere's an inherent limit to how fast you can communicate with objects in space, so a video call with someone where you will have 1-2s of lag (guaranteed by laws of physics, not occasionally) might be unusable. There is also the impact of distance, you might have even higher latency to the same object depending on the time of the year (Earth - Mars today vs Earth - Mars few months out).
- nwiswell 4y agoYour figures are totally wrong. The distance to geostationary orbit is around 30,000 km, so at the speed of light (~300,000 km/s), that is 100 ms of latency. Low earth orbit is 3,000 km or so, meaning that's only 10 ms each way. Odds are good that if you had a mesh network of low earth orbit satellites (like Starlink) you could actually get an antipodal point-to-point video call with less latency than with terrestrial fiber. That's not a function of bad terrestrial switching/routing: it's the fact that light travels faster through vacuum.
- latchkey 4y agoIt amazes me that we can do this from space, but I can't do this from my house. /s
- Dylan16807 4y agoWhat's your budget?
- nix23 4y ago300 dollars if you life in switzerland is enough 30 for 10.
- latchkey 4y agoThat got me thinking about trying to find the mission budget for TBIRD and I came up empty handed after a bunch of googling...
- wdb 4y agoHappy to pay upto £5.000,00 for setup/digging and then upto £60/month for 1Gbps in Central London. G.Network, Pure Fibre, BT (not a business address), Hyperoptic all don't want to bite while some have fibre in a street short distance away (~100 meters) from my house
- fennecfoxy 4y agoIt's tough in the UK, especially London, especially especially central London. I moved from NZ where we'd done probably one of the best fiber rollouts of any country; I had 1Gbps into an apartment from about 2016 or so. Before that I'd had 200ish mbps into a house in the suburbs in about 2014 thanks to the previous tenants having run a business from the place and paid for a line in. Now I live in the UK I can see why it's hard - too much history/housing here is just built up far too much/not built up in a modern way either. Also I think when obtaining permissions from property owners in the case of flats, Kiwis are generally more likely to approve of something like that than people here.
- 4y ago
- sschueller 4y agoI don't always want to be the party pooper and this tech does have a lot of benefits when trying to transmit large items. However, you ain't ging to be video conferring to the moon or Mars with it. Not a single word about latency in the article.
- nix23 4y agoHumans wil adapt. If you want to call mars an ai will support you what the question/following sentence will be so you can answer the predicted question in one swoop. Problem solved.
- fortyseven 4y agoThey did that recently on the TV show Avenue 5.
- shadowofneptune 4y agoOr you could write an email? I don't see how that works at all, you'd still be sitting in silence for minutes while the response loops around.
- jtsiskin 4y agoThat’s the speed of light, an aspect we can’t improve. The article is about bandwidth, an area we are able to affect.
- 7952 4y agoYou can send the data through a different medium to improve latency which satellite optical links could help with.
- Zigurd 4y agoIn space, latency will be dominated by distance. In low orbits, lasers will have low latency, good enough for interactive applications. Geosynchronous, Moon, and farther can't be helped.
- rumdonut 4y agoHey, I worked on this. Glad to see it getting a lot of press :).
- Kye 4y agoAre you able to talk about what kind of hardware is on the satellite? I'm curious if it's commodity like the Mars helicopter or something made for the purpose.
- Aromasin 4y agoNot OP, so I'm guessing purely on my knowledge of how most of the industry works, but there's likely some sort of FPGA with custom IP at the center, connected to a powerful optical transmitter/receiver. Associated reading can be found here: https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Microelectronics/The_use_of_reprogrammable_FPGAs_in_space https://www.esa.int/Enabling_Support/Space_Engineering_Techn... https://ntrs.nasa.gov/api/citations/20150009433/downloads/20150009433.pdf https://ntrs.nasa.gov/api/citations/20150009433/downloads/20... https://www.fierceelectronics.com/electronics/fpga-enables-high-bandwidth-space-systems-lower-system-cost https://www.fierceelectronics.com/electronics/fpga-enables-h...
- error503 4y agoThe main paper seems to be behind a paywall (rolleyes), but I did find this synopsis that covers the basic approach and hardware: https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4406&context=smallsat https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4... It sounds like this test payload was part of a larger CubeSet built by NASA, but the actual datacom components seem pretty much off the shelf (besides the optics). 100Gbps transceivers, an optical mux, and an EDFA - all common in terrestrial telecom - and some IR optics to collimate the beam.
- tiffanyh 4y agoAnything you can share on latency? (congrats on the achievement)
- 4y ago
- ghalvatzakis 4y agoSignal in space travels 3 times quicker than fiber optics. This means that in some cases the latency may be lower than fiber.
- kaibee 4y agoIts actually only 50% faster. Light in a fiber optic travels at ~2/3c. In a vacuum it travels at c. So its c / (2/3) = ~1.5
- emkoemko 4y agois there a reason some US stock markets are using lasers ? wouldn't fibre be just as fast as laser going through the air?
- govg 4y agoLasers are easier to setup (you just need two end stations) and don't need dedicated lines (you don't have to lay any fiber). If you have an existing connection between two points, then fiber might be better / same, but if you had to setup something for cost / speed, then laser would win.
- nine_k 4y agoThe higher the index of refraction of a medium, the slower light travels in it. Air barely refracts light, and glass refracts it heavily. BTW laser links are prone to work worse in bad weather. Microwave links are often used instead.
- robochat 4y agoYes this is why many high frequency traders have installed laser or microwave links to their nearest stock exchanges, simply to gain a few microseconds advantage in their trades. Fibre isn't as fast as laser going through the air. It's 50% slower (as the parent comment states) (unless you are using special hollow core fibres which are uncommon for now). More importantly, fibres rarely go in a straight line between 2 points, they wind their way through buildings, down into basements, through buried pipes etc and this all adds extra distance to the route and hence more delay to the signals. A line of sight link is the shortest route between 2 points.
- reillyse 4y ago“…to downlink all the data they could ever dream of.” I think they are significantly underestimating the dreams of users of comms.
- make3 4y agoyeah satellites potentially have gigantic cameras arrays and sensors of all kinds
- kipchak 4y agoThings are much more difficult from space, but DLR/Mynaric posted 1.72 Tbit/s over 11 KM back in 2016, so we might optimistically not be too far off. https://www.dlr.de/content/en/articles/news/2016/20161103_world-record-in-free-space-optical-communications_19914.html https://www.dlr.de/content/en/articles/news/2016/20161103_wo...
- pcthrowaway 4y agoNow they just need to work on the latency.
- sedatk 4y agoAlmost there: https://www.cnn.com/2022/12/01/world/scientists-baby-wormhole-scli-intl-scn/index.html https://www.cnn.com/2022/12/01/world/scientists-baby-wormhol...
- redanddead 4y agoIt's all the rage in spacetech these days... Especially among American and Chinese startups.
- pkaye 4y agoKind of nice that cubesats and (SpaceX) rideshares brings down the costs enough that more of such experiments can be done.
- momofarm 4y agoNow they can watch youporn on ISS, don't forget turn it off when livestream on nasa tv.
- jabthedang 4y ago
- foreverobama 4y agoAnd yet here in 2022 cell reception quality is quite literally worse than it was in 2010. Telecommunications industry is really baffling at times. Just like when people were excited for 5G, I'm very skeptical that this technology will ever actually improve our lives in the short to medium term. Overall, services across the board seem to be worse than they were 10 years ago. And yet the tech is certainly more advanced. Really disappointed as a whole with the telecommunications industry. Maybe that's the field I should have focused more on, as they seem to be struggling to improve things even with technological breakthroughs such as this. Just a shame.
- adzm 4y agoI'm sure this varies by region, since anecdotally reception and bandwidth is significantly improved everywhere I've been in the past 10 years.
- anigbrowl 4y ago[citation needed]
- TreeRingCounter 4y ago
- ckosidows 4y agoMKBHD recently shared the same sentiment in a video. He feels, anecdotally, that 5G is worse than LTE. I feel the same way and recently switched my preferred network to LTE. You might find a better experience doing the same. I've found 5G to be truly awful and I live in one of the biggest cities in America where you would expect better infrastructure.
- wdb 4y agoAnd somehow I can not even get 100Mbps internet connection in Central London (Zone 2)
- dannylandau 4y agoAnyone familiar with this start-up --https://www.aalyria.com/ https://www.aalyria.com/? Seems like they are miles ahead of the MIT team which is still in the demo stage.
- cycomanic 4y agoI don't think they have any demonstrated space to ground comms yet. There are a number of players working on this though. I would say Lincoln lab is still the leader in this field though.
- luc_ 4y agoDoes this have implications for real-time satellite video data?
- pifm_guy 4y agoDon't optical links to space suffer terribly from atmospheric distortion? Imagine looking at a shell on the bottom of a swimming pool while there are ripples in the water.... Usually the shell is a bit distorted. But at some points in time, you see two shells... And other points in time, none. If the water represents the atmospheres shimmering due to changing density, and the shell represents the satellite you're trying to receive data from, then at some points in time, you won't be able to receive any data at all, because the receiver cannot see the satellite. Network links that are up and down every few milliseconds aren't very useful for much apart from bulk science data download. Perhaps that's why this is marketed for science missions rather than space internet?
- elihu 4y agoI'm not an expert in this area, but if I remember correctly a lot of satellites use radio links in the neighborhood of 10 Ghz for ground communication because they've found that band isn't affected much by atmospheric conditions.
- pclmulqdq 4y ago10-100 Ghz has very few bands where water is an absorber. It tends to fall between the molecular and atomic modes of many molecules, so you only suffer free space loss (which is still significant over long range at high frequency).
- walrus01 4y ago"traditional" geostationary satellites use various c, ku, ka and high ka bands. Anywhere from 6 to 30 GHz. Depends a lot on how new it is, what its intended use is and transponder/antenna configuration. and also depending on the intended size/type of earth stations and remote terminals. in addition to tracking/telemetry/control low data rate radios in the L/S-bands.
- keithnz 4y agothere's a big section of the article that talks about that (at a high level). Essentially all in the second half of the article with the title "From radio waves to laser light"
- fio_ini 4y agoGamers in space with 300fps and no lag. In the future when I get sniped in matchmaking it’ll be by an astronaut.
- itishappy 4y agoImagine the cooling system! A gaming computer can use 1000W. Google says spacecraft radiators reject 350W/m^2. If my math is correct (no guarantees) you'd need a king-sized-bed-sized panel just to cool your rig.
- twosdai 4y agoI don't think that because a computer uses 1000W of power it would produce 1000W of heat though. I think if that were true then there could be no computation done since all the energy of the electrons would be converted to heat. I'm not sure what the efficiency rating of computers is, or how much is turned heat. Not to rain on your back of the napkin math. Although I think your sentiment is right, the cooling systems for computers in space would need to be bigger since you can use convection to move the heat away.
- BenjiWiebe 4y agoIt is all heat, except for the light from your monitor which then turns into heat when it's absorbed. Computing isn't doing work in the physical sense. An HDD of ordered data doesn't have more potential energy than an HDD of data in a different order.
- andirk 4y agoUseless but slightly relevant aside: I was almost part of the first ecommerce transaction from outer space. This one civilian guy was in the middle of a large luxury item purchase before his space ship took him to outer space. My bosses emailed him and I think he responded from space somehow. They wanted him to sign off on the purchase to make it official, but he didn't until he got back to Earth Prime. Almost!
- midoridensha 4y agoThis isn't that hard to do, even with 1960s technology. It takes about 3 days with the Apollo launch system to get from the Earth to the Moon. So if you load roughly 800 4TB portable hard drives into one of these and fly it to the Moon, this will result in an average transmission speed of 100Gbps, if my math is correct.
- inetknght 4y agoBut goodness the ping time sucks in that one!
- midoridensha 4y agoSure, but if people only focus on bandwidth and ignore latency, as they usually do, my solution is easily done with off-the-shelf technology.
- airstrike 4y agoGood luck slapping 800 4TB hard drives from the 1960s onto a rocket. The Delta-v on that baby would suck
- midoridensha 4y agoWell, I meant today's portable 4TB hard drives, using rocket and lander tech from the late 60s.
- CobrastanJorji 4y ago
- oneplane 4y agoI might be wrong here (for a lack of in-depth knowledge) but isn't the full-body motion of the cubsat (for aiming) and the ARQ protocol the real development here? I know the laser links themselves might not be new, and while it hasn't been done like this, we knew that it would be possible considering we've done a ton of variants (sat-to-sat, station-to-station, over fiber, over glass, in open air, in a vacuum), even just hitting the beacons on the moon and measuring the reflection somewhat shows that long-distance links could be done. Maybe the new-ness in the laser aspect is the small satellite and energy package compared to high-powered lasers you might expect?
- docmechanic 4y agoEncouraging to see the CubeSat program producing such notable progress. Hopefully, we'll see many more reports of engineering advancements from miniaturization and commercial components adapted to the rigors of space.
- xyst 4y agoMeanwhile in the US, consumer internet is barely at 1 Gbps
- djha-skin 4y agoYes, but at what latency? That's the big pie in the sky with space intercommunication. Typical (pre-StarLink) latencies with satellite are like 3k milliseconds.
- s0sa 4y agoWhy is latency the “big pie in the sky”? We’re not talking about counter strike or Halo CE matches here, we’re talking about the ability to transmit large amounts of data from deep space very fast.
- stephen_g 4y agoOn what service? I have done a lot of military SATCOM, and our normal rount-trip latencies to geostationary could be as low as ~560ms. Not anything like as low as LEO (which are far, far closer to earth) but not unusable.
- schnable 4y agoBut what are the pings?