[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)