6 ms·
Closing in on the “perfect code” (2004)
- akhayam 3y agoIn 1993, two unknown French engineers claimed to have found a coding scheme to provide virtually error-free communications at data rates and transmitting-power efficiencies well beyond what most experts thought possible. Nobody believed them and set out to find the error in their paper... There was no error.
- deleted 3y ago[deleted]
- capitainenemo 3y ago30 years ago? What took so long for broad adoption? Patents? edit Article doesn't elaborate on why that might be, but it does note: "an alternative that has been given a new lease on life is low-density parity check (LDPC) codes, invented in the early 1960s by Robert Gallager at MIT but largely forgotten since then...Now researchers have implemented LDPC codes so that they actually outperform turbo codes and get even closer to the Shannon limit...Another advantage, perhaps the biggest of all, is that the LDPC patents have expired, so companies can use them without having to pay for intellectual-property rights."
- Yoric 3y agoUnfortunately, one of the common scenarios when it comes to percolating results from academia to industry is the following: 1. Academics make discovery/invent something. 2. Academics attempt to convince industry to adopt discovery. 3. Discovery is laughed out of industry as "impractical", "academic", etc. 4. Academics teach discovery to their students. 5. Students get into industry. 6. Students get into position of tech leads, architects, etc. 7. Students demonstrate the use of discovery. (by then, 30 years have elapsed) e.g. garbage collectors, type systems, threads, distributed systems, message passing concurrency, actors, JITs, metacompilation, machine learning, functional programming...
- pipo234 3y ago> 3. Discovery is laughed out of industry as "impractical", "academic", etc. To be fair, sometimes academic inventions are impractical given the technical landscape du jour. They only become feasible as technology and society progresses, say 30 years. Also, your observation does not mean any invention is meaningful (and will eventually be recognized as such). I for one, learned a bunch of "impractical", "academic" nonsense too in university. But yes, I think as a whole, your 7 points observation as a whole is very much at play in the Turbo Codes case. Yes.
- Yoric 3y agoFair enough.
- jiggawatts 3y agoThe specific issue with LDPC and Turbo Codes is that they both introduce latency, and require a ton of compute to decode. If you don't care about latency and have an "unlimited" compute budget, then they're great and hence they were used very early for deep space communications. The speed-of-light delay means that there's minutes or even hours of latency anyway. And of course, the receiving station is a data centre with as much computer power available as you please. In hand-held devices running on battery with latency constraints measured in milliseconds, it's an entirely different ballgame. Suddenly, there's real engineering problems to solve, and the trade-offs aren't always worth it. Something I've told people when both 4G and 5G technologies rolled out is that these are enabled by the advances in the bleeding edge of silicon chip technology. Both rely on very heavyweight signal decoding algorithms that require dedicated "offload" circuitry almost as big as the main CPU! Some anti-5G crazies think that their hand is getting hot from the "radiation", when in fact it is the decoding chip that's getting warm from the power it has to draw from the battery! PS: This is why every new 4G/5G/6G/etc... tech always gets panned as impacting battery life. One or two silicon process shrinks later, this is not a problem. The radio power didn't change, but the decoding power did!
- HopenHeyHi 3y ago0. Science Advances One Funeral at a Time
- giobox 3y agoNot an expert, but I've encountered Reed Solomon error correction extensively in my career, and this seems to be replacing RS applications? I wouldn't be surprised if there was a fair amount of inertia to overcome given how widely used and how well RS worked for a very long time. RS was critical for things like ADSL data transmission over POTS and other similar large scale applications. The wikipedia page for RS suggests some RS implementations are now "being replaced by more powerful turbo codes". > https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_cor...
- akhayam 3y agoJust adding some extra color: Turbo codes did get instant traction in the industry once the academics actually "believed" them to be true. So the friction came from the academics and not the industry. Today, every communication system you are using are relying on Turbo codes in some shape or form.
- topaz0 3y agoNote that the article is almost 20 years old, so it is more like 10 years for industry adoption.
- mturmon 3y agoTurbo codes were used in the Mars Reconnaissance Orbiter (2005 launch) due to work by JPL telecommunication researchers. (https://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter#Telecommunications_system https://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter#Te...) Edited to add an early link to more granular technical work: https://ipnpr.jpl.nasa.gov/progress_report/42-120/120D.pdf https://ipnpr.jpl.nasa.gov/progress_report/42-120/120D.pdf
- cryptonector 3y agoPatent lifetimes are 20 years.
- eikenberry 3y agohttps://en.wikipedia.org/wiki/Turbo_code https://en.wikipedia.org/wiki/Turbo_code
- rrwright 3y agoThe article is from 2004.
- zokier 3y agoSee also Fountain Codes, e.g. RaptorQ: https://en.wikipedia.org/wiki/Fountain_code https://en.wikipedia.org/wiki/Fountain_code
- akhayam 3y agoErasure codes are a work of art for storage use cases, but not as broadly relevant as, say Turbo codes or space-time codes (like Alamouti codes).
- jgalt212 3y ago> key to the next generation of multimedia cellphones How is perfect data transmission a make or break feature for lossy compression and transmission of audio and video?
- Vecr 3y agoYou get less overhead from the code. Actually, this article is from 2004, so if you use a 4G cell phone you actually already are using the code. 5G uses something different though.
- esprehn 3y agoThis should be tagged (2004)
- dang 3y agoAdded. Thanks!
- roboman 3y agoI worked on forward error correcting codes for a variety of systems. A few big issues with Turbo codes: 1. Decoder complexity - often 4x or more the complexity of simpler codes. 2. Encoder delay- you need to have a really long interleaver at the transmitter to get the big dB of improvements. 3. These work best an pure additive white gaussian noise channels - most channels suffer from multipath, fading and other disturbances. So while they are good far satellite broadcast system they don't always work as well in other applications.
- lincpa 3y ago[dead]