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The one Manty tech leap which always annoyed me

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Re: The one Manty tech leap which always annoyed me
Post by tlb   » Sun Dec 19, 2021 9:03 am

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Daryl wrote:Seeing as how this is a nautical derived series, consider how much information Nelson could cram into a few signal flags? Somewhat like ordering a Chinese takeaway, I'll have a 13,23,36,42,and a 57.

Fox2! wrote:With a sophisticated and well thought out code book, one can compress any message required into a few flag hoists. IIRC, Hornblower in one story has a competition among his junior lieutenants and midshipmen to send a given message in the fewest flags. The winner was quite creative in his use of homonyms that were in the code book for words that weren't.

There are compression tricks that can be employed with images and sound as part of video transmission, but you still have an enormous amount of data to move. It is the increase and improvement in bandwidth needed in the course of a few years that was the source of the complaint, Some of that has been addressed by the improvements in node technology and the use of multiple nodes and the vast improvement in power availability due to the development of micro fusion reactors.
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Re: The one Manty tech leap which always annoyed me
Post by Dahak   » Sun Dec 19, 2021 3:59 pm

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Dahak wrote:
One thing that should also be thrown out alongside the other responses of bit-rate-vs-baud-rate is that I believe that somewhere along the line (I can't recall if on-page or online comment) I seem to remember - I could be wrong - His Weberness commenting along the lines that the original starship-mounted FTL Comm used the entire drive node array to generate signals (a la HMS Nike), where the latest marks of the FTL Comm used individual nodes in an array (a la HMS Hexapuma and HMS Volcano).


Just for reference:

https://infodump.thefifthimperium.com/entry/Harrington/156/1/

https://infodump.thefifthimperium.com/entry/Harrington/154/1/
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Re: The one Manty tech leap which always annoyed me
Post by ThinksMarkedly   » Sun Dec 19, 2021 11:53 pm

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Jonathan_S wrote:If you could pack 40 bits per pulse, like you suggested, then even a 1 pulse signal could carry 1 trillion different values -- even after you deduct quite a lot of that to leave room for some robust error correcting codes that still seems to leave vastly more codes that you'd need for any amount of "most likely threat parameters". I suggest that it's nowhere near that efficient at packing data into pulses, not at this early stage, or else it wouldn't take 4 pulses just to fit a custom code list for a reasonable number of just the most likely threat parameters.


Quite agreed. From Honor's description of the uses they were envisaging, it sounds like no more than 2 or 3 bits per pulse, giving a full "message" of 4 pulses at best 12 bits. If you build in 2 bits for error correction, that's a mere 1024 different messages.

It's also possible she was talking nonsense. She's not a comms specialist.

I'd also note that these RDs have a FTL transmission range of 4 light hours - while the newer really high bandwidth FTL like Keyhole II and Hermes have far shorter ranges; like around 40 times shorter (Keyhole II being good for around 5-6 LM). It's possible that the grav signals "smear" over distance as they travel along the Alpha wall and to get the maximum range you might need not only a much more powerful pulse but you also might need to use simpler encoding so it's still intelligible at those extended ranges.



But it does seem that due to the reduced transmission ranges the newer really high bandwidth FTL should needs far less powerful grav generators -- which presumably would be correspondingly smaller but also be easier to engineer for high pulse rates.

And the 1903 PD FTL tech might well have been capable of higher bandwidth that we see from these RDs if they'd been willing to engineer less powerful, shorter ranged, transmitters.


Or they stopped trying to transmit for over light-hours. The passage you quoted talks about how it had been mankind's dream to have FTL comms over interstellar range, so the R&D team might have been pursuing that first and 4 light-hours was the best they could, with the signal attenuation that is created by that distance. That would explain why they were mounting a huge power source.

But then they realised they were never going to get interstellar ("insurmountable limitations") and decided to focus on tactical uses only. At which point some young person who was not part of the project pointed out that tactical uses don't need light-hours: almost all combat happens within half a light-hour. So if you're not trying to send a message that will be received by something 8x closer, if it's a simple squared attenuation that's 64x better signal at the receiver. But in fact, most attenuation approximations are actually to the third or fourth power, so it could be even better than that.

Then you add the Fifth Imperium posts Dahak linked to above. It looks like the biggest improvement in pulse cycle time was the fact that they didn't need to charge a capacitor to send each.

Then I could add that the biggest breakthrough was finding out just how to modulate signals. Remember this is a medium that no one has ever transmitted on before. There is no technology for how to finely control the pulse you're sending. Before it exists, you're doing a basic ASK or FSK (Morse code can be thought of as a very crude form of FSK). But once you do know how to do that, you can apply 2200 years of theoretical and applied development of information transmission. That could be a jump equivalent from going from Morse code to a modern 4096-QAM (see also) or OFDM) overnight.

In fact, our own gravcoms are very similar to that. We know that the medium exists and we know there are pulses in it (see the LIGO and Virgo confirmations of the existence of gravitational waves). But right now, transmission is wholly impractical.

PS: Larry Niven and Greg Benford's third book on the Bowl of Heaven trilogy, "Glorious," talks about how an advanced, K2-level civilisation uses gravitational waves for interstellar communication.
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Re: The one Manty tech leap which always annoyed me
Post by Jonathan_S   » Mon Dec 20, 2021 1:30 am

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ThinksMarkedly wrote:In fact, our own gravcoms are very similar to that. We know that the medium exists and we know there are pulses in it (see the LIGO and Virgo confirmations of the existence of gravitational waves). But right now, transmission is wholly impractical.

PS: Larry Niven and Greg Benford's third book on the Bowl of Heaven trilogy, "Glorious," talks about how an advanced, K2-level civilisation uses gravitational waves for interstellar communication.

Also good points in the bits I snipped - but wanted to just address this part.

Unfortunately we also know from LIGO that those gravitational waves move at only the speed of light -- sadly no FTL comms for us via that route.

Though they do travel insanely long distances if you don't mind the wait; LIGO having detected events up to 172 billion LY away. However, I don't know whether gravity waves are any more energy energy efficient at long range signaling than electromagnetic waves would be or if the range is due solely to the insane power of the original event.
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Re: The one Manty tech leap which always annoyed me
Post by ThinksMarkedly   » Mon Dec 20, 2021 10:43 am

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Jonathan_S wrote:Unfortunately we also know from LIGO that those gravitational waves move at only the speed of light -- sadly no FTL comms for us via that route.

Though they do travel insanely long distances if you don't mind the wait; LIGO having detected events up to 172 billion LY away. However, I don't know whether gravity waves are any more energy energy efficient at long range signaling than electromagnetic waves would be or if the range is due solely to the insane power of the original event.


Well, so does light. We're observing galaxies that existed a mere few hundred million years after the Big Bang using the HST. With the JWST, it's expected we'll be able to peek even further back. This Real Engineering video I watched yesterday was discussing how it's attempting to gather light at a rate of about 1 photon per second (the video focuses on the mechanical and technological aspects of the Webb, rather than the physics).

We can even see further back in the form of the Cosmic Microwave Background radiation, though that tells us no features. We hope to eventually see even further back in the form of the Cosmic Neutrino Background (CνB).

Gravitational waves being FTL have been a popular trope in sci-fi that unfortunately the scientists have just confirmed busted. Einstein's equations did say they moved at the speed of light, but until someone confirmed they existed and matched the reception of a signal there to a light-speed signal, Einstein could've been wrong... not bloody likely, but he could have. But his equations say that that's the speed, but don't say why that is. Neither does our current understanding of quantum physics, because that doesn't explain gravity either.

BTW, if you wanted to transmit something with very little to no attenuation, neutrinos would be the best, since they interact with almost nothing. Meanwhile, I'm hoping for the first simultaneous gravitational, electromagnetic, and neutrino detection event. I don't know what kind of event that would be though... do neutron star and blackhole mergers emit neutrinos?
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Re: The one Manty tech leap which always annoyed me
Post by Relax   » Mon Dec 20, 2021 4:22 pm

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clancy688 wrote:
A fair point, but I believe that a bit rate of 0.102 bit/s is completely useless in any tactical application. It's simply impossible to convey meaningful information about occurences in a 3D space in a timeful manner with that sort of pulse.


PCM

Modulates not only frequency rate, but magnitude. We have zero information about how uniform said pulse is that you are reading, or if it is wave with near zero hysteresis which can be heavily modified in magnitude and duration. AS soon as that barrier is breached we are talking exponential growth in bandwidth. Magnitude modulation of course will lead to lower com range. But you can still use frequency modulation but lower com rate.
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Re: The one Manty tech leap which always annoyed me
Post by cthia   » Thu Dec 23, 2021 7:21 am

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It is not that Clancy doesn't have a point. He does. And many explanations have been covered. But I would like to add that no single technology in the history of man resembles anything like its prototype stage. After proof of concept, it is off to the races.

However, I would imagine that a lot of the early problems had as much to do with the receivers just as much with the source. Drones and missiles down range had to be able to parse what is being sent while accelerating at breakneck speeds.

Son, your mother says I have to hang you. Personally I don't think this is a capital offense. But if I don't hang you, she's gonna hang me and frankly, I'm not the one in trouble. —cthia's father. Incident in ? Axiom of Common Sense
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Re: The one Manty tech leap which always annoyed me
Post by kzt   » Tue Dec 28, 2021 2:09 am

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clancy688 wrote:A fair point, but I believe that a bit rate of 0.102 bit/s is completely useless in any tactical application. It's simply impossible to convey meaningful information about occurences in a 3D space in a timeful manner with that sort of pulse.

The transmission rate of ELF radio is very slow, on the order of 3 bits per second, but people find it useful in special cases.

FTL early on is not a tactical application, it's an operational application. It's used when units are quite separate from each other. And it would normally be codewords you would send, possibly followed by something clarifying. Assuming you are sending 20 total characters it would take ~20 seconds. Which means that if the receiver is within ~6 million KM it would be faster to use radio.

But it has a lot of range and is very stealthy against typical opponents.
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Re: The one Manty tech leap which always annoyed me
Post by Joat42   » Mon Jan 10, 2022 11:07 am

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tlb wrote:
Daryl wrote:Seeing as how this is a nautical derived series, consider how much information Nelson could cram into a few signal flags? Somewhat like ordering a Chinese takeaway, I'll have a 13,23,36,42,and a 57.

Fox2! wrote:With a sophisticated and well thought out code book, one can compress any message required into a few flag hoists. IIRC, Hornblower in one story has a competition among his junior lieutenants and midshipmen to send a given message in the fewest flags. The winner was quite creative in his use of homonyms that were in the code book for words that weren't.

There are compression tricks that can be employed with images and sound as part of video transmission, but you still have an enormous amount of data to move. It is the increase and improvement in bandwidth needed in the course of a few years that was the source of the complaint, Some of that has been addressed by the improvements in node technology and the use of multiple nodes and the vast improvement in power availability due to the development of micro fusion reactors.

As someone who has worked with video-compression, you'd be amazed how much you can compress video if you cheat or are smart about it. You can for example totally suppress any noise in an video which makes it look unreal/artificial but it'll compress extremely well - you then re-introduce artificial noise when decompressing the video to make it look "real".

Regardless, considering the amount of processing-power available in the Honorverse and the progress on entropy encoding would probably mean the bitrate to transfer any kind if HD-video could be magnitudes less than we are capable of today. So a 1.5MBit video-stream today could for example be a 15kbit or less in Honorverse.

And in regards to the improvements in bandwidth, we are talking about something that's improved from a very primitive platform up to something that's quite sophisticated - that leap in performance from the beginning isn't linear, it's usually logarithmic so as the technology matures we will se it converge towards being linear.

---
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Re: The one Manty tech leap which always annoyed me
Post by Jonathan_S   » Mon Jan 10, 2022 12:47 pm

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Joat42 wrote:There are compression tricks that can be employed with images and sound as part of video transmission, but you still have an enormous amount of data to move. It is the increase and improvement in bandwidth needed in the course of a few years that was the source of the complaint, Some of that has been addressed by the improvements in node technology and the use of multiple nodes and the vast improvement in power availability due to the development of micro fusion reactors.

As someone who has worked with video-compression, you'd be amazed how much you can compress video if you cheat or are smart about it. You can for example totally suppress any noise in an video which makes it look unreal/artificial but it'll compress extremely well - you then re-introduce artificial noise when decompressing the video to make it look "real".

Regardless, considering the amount of processing-power available in the Honorverse and the progress on entropy encoding would probably mean the bitrate to transfer any kind if HD-video could be magnitudes less than we are capable of today. So a 1.5MBit video-stream today could for example be a 15kbit or less in Honorverse.

And in regards to the improvements in bandwidth, we are talking about something that's improved from a very primitive platform up to something that's quite sophisticated - that leap in performance from the beginning isn't linear, it's usually logarithmic so as the technology matures we will se it converge towards being linear.[/quote]
Just had a thought come into my mind.

We saw with what the ex-prisoners did with the coms equipement at Hades that canonically Honorverse com computers can do realtime rendering of a person that's visually indistinguishable from video of them. (The tricky bits, for them, were trying to convert the text into that person's wording and mannerisms). And most video calls are just a person (or people) talking in front of a fairly generic background.

I doubt they bother but you might well be able to make extremely low bandwidth "video" calls using that capability. Instead of actually sending compressed frames of video, during the call's handshake send the remote side the 3D model of the caller -- then in addition to their voice just send the remote side the muscle movements of the caller and let the receiving com computer render it all back into video by applying the observed muscle movements to the 3D model of the caller.
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