[HN Gopher] 100 Gbps achieved from space to Earth ___________________________________________________________________ 100 Gbps achieved from space to Earth Author : sizzle Score : 237 points Date : 2022-12-07 18:26 UTC (4 hours ago) (HTM) web link (news.mit.edu) (TXT) w3m dump (news.mit.edu) | JoeAltmaier wrote: | I 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 | Kuinox wrote: | That error correction, great video of 3blue1brown explaining | how one such algorithm works: | | https://www.youtube.com/watch?v=X8jsijhllIA | pclmulqdq wrote: | Another 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. | sgtnoodle wrote: | This 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 wrote: | > _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 wrote: | That's super cool. Error correcting codes are truly amazing | technology. | MayeulC wrote: | Which is exactly what Wi-Fi does, adjusting the amount of | parity data depending on link loss, to keep retransmissions | to a minimal. | sgtnoodle wrote: | Indeed. 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. | sedatk wrote: | You must have a retransmission mechanism anyway. You can always | implement such mechanisms on top of a retransmitting protocol. | nonameiguess wrote: | US 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. | reillyse wrote: | "...to downlink all the data they could ever dream of." I think | they are significantly underestimating the dreams of users of | comms. | make3 wrote: | yeah satellites potentially have gigantic cameras arrays and | sensors of all kinds | kipchak wrote: | Things 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_wo... | jabthedang wrote: | wdb wrote: | And somehow I can not even get 100Mbps internet connection in | Central London (Zone 2) | luc_ wrote: | Does this have implications for real-time satellite video data? | wwwtyro wrote: | I'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? | nix23 wrote: | You forgott latency...not usable for rt communication. | emkoemko wrote: | how 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 wrote: | There'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 wrote: | Your 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. | nine_k wrote: | Latency to the Moon and back is below 2.5 seconds. | Bouncing a signal off the Moon is a known ham radio | operators' pastime. | kipchak wrote: | I've seen numbers of about 2.7Mbps[1] for average peak traffic | rates per subscriber on cable, which would give you about | 37,000 users if I didn't mess up my bits and bytes. | | But as the FSO link is point to point, you would need something | like a high-altitude platform station (HAPS) like a blimp, UAVs | with RF or a RF tower on the ground to receive the FSO signal, | and then broadcast it to many users. | | [1]https://www.nctatechnicalpapers.com/Paper/2018/2018-analysis | ... | foreverobama wrote: | You're dreaming, buddy. 5G can't even be successfully utilized | in the richest nation on earth (U.S.). This brand new tech is | decades from customer applications. Cool display of technology, | but I won't get excited over something that won't improve the | lives of anyone except the military industrial complex and its | benefactors while internet services and cell services continue | to degrade every year. | dang wrote: | Since you've already started breaking the site guidelines | again, I've banned this account. | | If you don't want to be banned, you're welcome to email us at | hn@ycombinator.com with reason to believe that you'll stick | to the site guidelines in the future. They're here: | https://news.ycombinator.com/newsguidelines.html. | jaywalk wrote: | Zero 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. | foreverobama wrote: | And 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 wrote: | I'm sure this varies by region, since anecdotally reception and | bandwidth is significantly improved everywhere I've been in the | past 10 years. | surfpel wrote: | Pretty rare for me to see it below 50mbps. Usually around 200 | or above. | ROTMetro wrote: | This. Rural Rocky Mountains here and in the last year 5g has | made service exponentially better. | anigbrowl wrote: | [citation needed] | TreeRingCounter wrote: | ckosidows wrote: | MKBHD 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. | kart23 wrote: | 5G is better in some usecases. LTE gets destroyed at sporting | events or festivals, while 5G can support more devices and | faster speeds. | qwertywert_ wrote: | This is 1 point-to-point link (laser) with direct aim required. | No forwarding, no more than 1 user. | | I don't see how this relates to the use-case of millions of | broadband users that you are talking about where you are | routing fiber cables all over the place. We do have 800-gigabit | fiber in core networks, we just don't route it to every home | b/c why would we. And 5G radiates to 1000s of users | simultaneously.. regularly getting multi-gigabit speeds on | mmWave as a regular user is pretty amazing to me. | latchkey wrote: | It amazes me that we can do this from space, but I can't do this | from my house. /s | foreverobama wrote: | Exactly. Which is why I'm always less than enthused by articles | such as this. With the telecommunications industry, it seems | breakthroughs such as this never make their way to the average | or even slightly high-end user such as myself. | | Wake me when telecommunications industry gets their shit | together. | poly_morphis wrote: | Nearby to me is the Microsoft HQ campus. Few miles away is | Amazon, not to mention most every other major software company. | Even SpaceX has an office here. My home has one available ISP, | and that's Comcast. I pay monthly for 100/30 what other homes | pay for 1000 up & down. The home 50ft behind mine has fiber. | It's insane to me. | Dylan16807 wrote: | What's your budget? | latchkey wrote: | That got me thinking about trying to find the mission budget | for TBIRD and I came up empty handed after a bunch of | googling... | nix23 wrote: | 300 dollars if you life in switzerland is enough 30 for 10. | wdb wrote: | Happy to pay upto PS5.000,00 for setup/digging and then upto | PS60/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 | toast0 wrote: | Line of sight is easier to arrange upwards. | pkaye wrote: | Kind of nice that cubesats and (SpaceX) rideshares brings down | the costs enough that more of such experiments can be done. | pcthrowaway wrote: | Now they just need to work on the latency. | sedatk wrote: | Almost there: https://www.cnn.com/2022/12/01/world/scientists- | baby-wormhol... | ghalvatzakis wrote: | Signal in space travels 3 times quicker than fiber optics. This | means that in some cases the latency may be lower than fiber. | kaibee wrote: | Its 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 wrote: | is there a reason some US stock markets are using lasers ? | wouldn't fibre be just as fast as laser going through the | air? | govg wrote: | Lasers 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 wrote: | The 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 wrote: | Yes 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. | redanddead wrote: | It's all the rage in spacetech these days... Especially among | American and Chinese startups. | pifm_guy wrote: | Don'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 wrote: | I'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 wrote: | 10-100 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). | keithnz wrote: | there'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" | sschueller wrote: | I 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. | OkayPhysicist wrote: | The moon is only a second away. That's awkward for | conversation, but perfectly possible for a structured meeting | setting. | nix23 wrote: | Humans 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 wrote: | They did that recently on the TV show Avenue 5. | shadowofneptune wrote: | Or 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. | delta_p_delta_x wrote: | > latency | | Well, the Moon's semi-major axis is about 380000 km, which | means latency is _lower-bounded_ to about 1 s. | | Similarly, Mars' closest approach is 54.6 million km. That | means a latency lower bound of 3 minutes. | Kye wrote: | The satellite is only 300 miles up. The processing power on the | satellite itself probably matters more for latency. At 200Gbps | max (2x100), it's probably no slouch. | [deleted] | jtsiskin wrote: | That's the speed of light, an aspect we can't improve. The | article is about bandwidth, an area we are able to affect. | 7952 wrote: | You can send the data through a different medium to improve | latency which satellite optical links could help with. | bhaney wrote: | This is already sending data via lasers traveling through | free space (and air, which has nearly the same speed of | light as free space). You're not going to get a medium with | a faster speed of light than free space unless you get into | space-warping theoretical stuff. Even if you managed to run | a fiber optic cable between a satellite and the earth, it | would be around a third slower than lasers through space. | HideousKojima wrote: | Speed of light is still a limit, fastest possible roundtrip | time between the Earth and moon is 2.5 seconds. Round trip | between the Earth and Mars would be over 6 _minutes_ when | Mars is at its very closest to Earth. | emkoemko wrote: | in space its the distance, light has a speed limit | Zigurd wrote: | In 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. | packetlost wrote: | Laser link (not RF) implies a whole bunch of things: | | 1. speed of light through atmosphere, so basically _c_ 2. line- | of-sight is required, likely stationary base stations. Probably | also subject to atmospheric and weather conditions | jamesmunns wrote: | For those curious, I went and looked it up, and the one way | (not round trip!) light travel time to the moon is about 1.3 | seconds, and one way light travel time to mars is 3-22 minutes | or so, depending on how far they are at the time. | | So maaaaaybe you could have a really painful conversation with | someone the moon, but not Mars. | | edit: This is WITHOUT any latency introduced by the | link/protocol, or if you have to then route the message from | one side of the earth to the other, just time-of-flight | distance calculations, so the absolute minimum possible | latency. | KptMarchewa wrote: | 1.3 seconds delay for conversation is mildly inconvenient, | not painful. | dannylandau wrote: | Anyone familiar with this start-up --https://www.aalyria.com/? | | Seems like they are miles ahead of the MIT team which is still in | the demo stage. | momofarm wrote: | Now they can watch youporn on ISS, don't forget turn it off when | livestream on nasa tv. | rumdonut wrote: | Hey, I worked on this. Glad to see it getting a lot of press :). | wmlavender wrote: | Is this likely to work at Lunar distances anytime soon? I saw | that the James Webb telescope people were unhappy about losing | much of their communication time on the Deep Space Network to | the Artemis 1 mission. Could this be more cost effective than | an major upgrade to the Deep Space Network? | | How about at Earth-Sun L1 and L2 distances? | elihu wrote: | I would expect L1-to-earth communication to be problematic | because you'd have to distinguish the signal from the | background radiation of the sun. | | It'd be interesting to know what the technical limits are in | terms of output power and aim/focus. Generally, doubling | distance means the signal power drops to 1/4th, and maximum | data capacity of a communication link is proportional to the | signal/noise ratio. So that would mean a 100 Gbps link might | drop to 25 Gbps. You might be able to bring the signal/noise | ratio back up by using a better detector or a more powerful | laser, or aiming better. Or maybe the 100 Gbps data rate is | limited by the transceiver, and there's actually plenty of | S/N ratio margin that can be traded for range without | affecting data rate at all. | Kye wrote: | Are 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 wrote: | Not 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/Ena | bling_Support/Space_Engineering_Techn... | | https://ntrs.nasa.gov/api/citations/20150009433/downloads/20. | .. | | https://www.fierceelectronics.com/electronics/fpga- | enables-h... | iwillbenice wrote: | tiffanyh wrote: | Anything you can share on latency? | | (congrats on the achievement) | Rebelgecko wrote: | Isn't it just "distance/c"? (or something like 0.999c since | light is a bit slower in the atmosphere) | tiffanyh wrote: | That's why I actually ask. | | E.g. "light travels approximately 1.5x slower through | optical fiber than in a vacuum" | | https://www.commscope.com/globalassets/digizuite/2799-laten | c... | bloggie wrote: | Fun and somewhat related fact - this is one of the main | advantages of hollow-core transmission fibers! As far as | I know, currently only used to extend the range of HFT | orgs... | ccakes wrote: | Terrestrial radio links are similar in that they can be | lower latency than fibre though spectrum concerns can | come into play. | brianwawok wrote: | Radio links can also often be straighter. Easier to go | over someone's house then ask permission to dig a trench. | Arnavion wrote: | ("1.5x slower" == "its speed in optical fiber is 1/1.5 = | 2/3 of the speed in vacuum") ___________________________________________________________________ (page generated 2022-12-07 23:00 UTC)