The one Manty tech leap which always annoyed me

Heya,

I'm currently in the process of relistening to the Honorverse novels, and once again I came across one specific Manty technology leap which always struck me as completely unbelievable. Yeah I know, this is SciFi and most tech is made up anyway, but even though SciFi shouldn't exactly be "realistic", it should at least try to be believable. And this certain piece of tech is, at least in-Honorverse, not.

I'm talking about the FTL communication. Specifically about the evolution of the FTL com. Don't misunderstand me, I'm completely fine with the idea of the FTL com as introduced in HH2. Low-speed gravity pulses akin to morse signals. That's fine with me.
And it's still like this in HH7 - when Prince Adrian is heading away from the convoy to the task force, it's stated that "the time required to generate each pulse meant a simple declarative sentence could take as much as two full minutes to transmit."
This means that the system has a super low transmission rate - if a sentence has about 120 letters and a letter is represented by an eight bit symbol, then we get a transmission rate of 8 bit/s.
So this has been the state of things in 1911 PD.
So let's leap to 1921 PD, when suddenly the Hermes Buoy appears - which acts as a relay system and can even transmit video.

Now where's the problem? The problem is how the Manties got from an 8 bit/s com system to something which can transmit video in barely 10 years. Which needs astronomically higher amounts of bandwith. As in several magnitudes higher. To bring this into perspective: A real world 1080p60 video call in teams needs about 1.5 Mbit/s. That is a bandwith 187500 times higher than 8 bit/s.

1903 PD: 8 bit/s
1911 PD: 8 bit/s
1921 PD: 1500000 bit/s

So somehow, after keeping the system at a super low transmission rate for a decade, they managed to increase the bandwith by a factor of 200000 in just another decade.

Sorry, that's just not even remotely believable.

/rant_end

Less we forget, the first public demonstration of TV is considered to have occurred in 1925; only several decades after radio. The first transmission of pictures was over telegraph lines.

It is possible that research on the beta squared node also assisted in the increase in bandwidth.

clancy688 wrote:Now where's the problem? The problem is how the Manties got from an 8 bit/s com system to something which can transmit video in barely 10 years. Which needs astronomically higher amounts of bandwith. As in several magnitudes higher. To bring this into perspective: A real world 1080p60 video call in teams needs about 1.5 Mbit/s. That is a bandwith 187500 times higher than 8 bit/s.

1903 PD: 8 bit/s
1911 PD: 8 bit/s
1921 PD: 1500000 bit/s

So somehow, after keeping the system at a super low transmission rate for a decade, they managed to increase the bandwith by a factor of 200000 in just another decade.

Sorry, that's just not even remotely believable.

/rant_end

Actually you vastly overstated the 1903 rate. HH2 says "Most importantly, it takes time for the generator to produce each pulse without burning itself out, which places an insurmountable limit on the data transmission speed. At present, we can only manage a pulse repetition rate of about nine-point-five seconds."

Assuming a bit can be transmitted in a single pulse then that's 9.5 s/bit; or 1/9.5 bit/s; or 0.102 bit/s.

So between 1903 and 1911 to go from 0.102 bit/s to 8 bit/s is already a 78 times faster transmission rate.
Yes, that's a long way from the 200,000 times improvement they still need by 1921 -- but it shows the technology wasn't stagnant.


And that was still, AFAIK, a single gravity generator being used to create the pulses. I believe it was the Shrikes where they pioneered using dozens together to not only boost the pulse rate but allow more complex signal modulation allowing data to be packed more efficiently into the pulses -- and that later made its way (with even more improvement) into the Ghost Rider RDs and later Hermes Buoys.

Jonathan_S wrote:Actually you vastly overstated the 1903 rate. HH2 says "Most importantly, it takes time for the generator to produce each pulse without burning itself out, which places an insurmountable limit on the data transmission speed. At present, we can only manage a pulse repetition rate of about nine-point-five seconds."

Assuming a bit can be transmitted in a single pulse then that's 9.5 s/bit; or 1/9.5 bit/s; or 0.102 bit/s.

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.

However, a pulse wouldn't necessarily convey a single bit, one pulse might be modulated to transfer more information, similar to QAM (i.e. encoding information in phase and amplitude of a signal). If, for example, a pulse every 9.5 seconds encodes 64 bits we're back at ~8 bit/s.
So the point about one pulse every 9.5 seconds doesn't necessarily indicate that there was any development between 1903 and 1911.

And yeah, if you start stacking stuff, like using multiple generators in parallel, increase the pulse rate, increase the modulation, then you'll be able to do large leaps in bandwith, but the 200k times leap still sounds far fetched.

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.

However, a pulse wouldn't necessarily convey a single bit, one pulse might be modulated to transfer more information, similar to QAM (i.e. encoding information in phase and amplitude of a signal). If, for example, a pulse every 9.5 seconds encodes 64 bits we're back at ~8 bit/s.
So the point about one pulse every 9.5 seconds doesn't necessarily indicate that there was any development between 1903 and 1911.

And yeah, if you start stacking stuff, like using multiple generators in parallel, increase the pulse rate, increase the modulation, then you'll be able to do large leaps in bandwith, but the 200k times leap still sounds far fetched.

Well those early FTL equipped RD did have a transmission distance of 4 light-hours.

Even a laboriously tapped out alert is still going to let you know somebody is there and roughly which way they're headed long before the 4 hours when you'd see the first lightspeed trace of them. Even the alerts takes 20 minutes to tap out, that's still 220 minutes sooner than you'd otherwise know they were there.


Those early RDs weren't trying to provide the rich data the RMN now gets from their Ghost Rider drones - no ECM profiles, no breakdown of ship class. But getting "ships sighted", followed later by number and size range, and then a general formation course and speed is already enough to give the defenders a massive leg up.

Just that generic "ships sighted", plus knowing which RD sent it, is enough to get your ships moving in the right general direction - even before you receive anything about their course and acceleration; and hours before you'd otherwise know anybody was there. That early movement gives you more defensive depth to play with, and gives them less time to build up their velocity.

And you've got time for additional information to trickle in - plus long before you reach combat range you'll have the enemy's wedges on your own FTL sensors and be seeing their lightspeed emissions directly.

So even if the transmission rate is less than 1 bit/s it's still useful, simply due to its range.

Jonathan_S wrote:Actually you vastly overstated the 1903 rate. HH2 says "Most importantly, it takes time for the generator to produce each pulse without burning itself out, which places an insurmountable limit on the data transmission speed. At present, we can only manage a pulse repetition rate of about nine-point-five seconds."

Assuming a bit can be transmitted in a single pulse then that's 9.5 s/bit; or 1/9.5 bit/s; or 0.102 bit/s.

You're confusing symbol rate (baud) with bit rate. You can transmit more than one bit per symbol. A simple encoding mechanism for this is the Amplitude Shift Keying (ASK), whereby different amplitude levels carry different values. To keep things binary, imagine you can transmit values symbols at amplitude -2, -1, +1 and +2. That is four different symbols, so you can assign two bits to them, which add up to four distinct values. In addition to that, you can transmit multiple signals over the same medium, usually in different frequencies (a form of frequency multiplexing). All of those techniques are used in anything we use today, so of course they would be used in the future too.

So even if they can transmit one pulse every 9.5 seconds, if that pulse carries 10 different frequency channels and you have 4 bits per symbol in each channel, we're talking 40x more than what you calculated. It's still a pitiful 4 bit/s, though.

The point is that each and every one of those areas are subject to technological improvement. You can send pulses more frequently, you can send in more frequencies (or you can find other ways of multiplexing), you can increase your symbol rate and you can send more bits per symbol. Assuming you have error detection or correction too, you can use more efficient ones if you have lower signal-to-noise ratio with improvements in transmitter power and receiver sensitivity.

And that was still, AFAIK, a single gravity generator being used to create the pulses. I believe it was the Shrikes where they pioneered using dozens together to not only boost the pulse rate but allow more complex signal modulation allowing data to be packed more efficiently into the pulses -- and that later made its way (with even more improvement) into the Ghost Rider RDs and later Hermes Buoys.

Right, using multiple transceivers can be used to overcome some technological limitations like the rate limit on cycling. It's another form of multiplexing.

Also note how multiple receivers can be used to increase the signal and lower the noise ratio too.

Please also understand this is military application. We're used to civilian uses, where we have one shared resource (the spectrum) and we must all use it. Civilians also expect that the power expenditure be kept to a minimum, either because it costs money to pay for the energy bill, or battery weight or battery time. In a military application, they will have fewer constraints on power and they also have a monopoly on the resource. They can use the entire spectrum and, if in doing so, you impede your enemy's ability to communicate, well, that's a feature not a bug.

ThinksMarkedly wrote:

Jonathan_S wrote:Actually you vastly overstated the 1903 rate. HH2 says "Most importantly, it takes time for the generator to produce each pulse without burning itself out, which places an insurmountable limit on the data transmission speed. At present, we can only manage a pulse repetition rate of about nine-point-five seconds."

Assuming a bit can be transmitted in a single pulse then that's 9.5 s/bit; or 1/9.5 bit/s; or 0.102 bit/s.

You're confusing symbol rate (baud) with bit rate. You can transmit more than one bit per symbol. A simple encoding mechanism for this is the Amplitude Shift Keying (ASK), whereby different amplitude levels carry different values. To keep things binary, imagine you can transmit values symbols at amplitude -2, -1, +1 and +2. That is four different symbols, so you can assign two bits to them, which add up to four distinct values. In addition to that, you can transmit multiple signals over the same medium, usually in different frequencies (a form of frequency multiplexing). All of those techniques are used in anything we use today, so of course they would be used in the future too.

So even if they can transmit one pulse every 9.5 seconds, if that pulse carries 10 different frequency channels and you have 4 bits per symbol in each channel, we're talking 40x more than what you calculated. It's still a pitiful 4 bit/s, though.

The point is that each and every one of those areas are subject to technological improvement. You can send pulses more frequently, you can send in more frequencies (or you can find other ways of multiplexing), you can increase your symbol rate and you can send more bits per symbol. Assuming you have error detection or correction too, you can use more efficient ones if you have lower signal-to-noise ratio with improvements in transmitter power and receiver sensitivity.

And that was still, AFAIK, a single gravity generator being used to create the pulses. I believe it was the Shrikes where they pioneered using dozens together to not only boost the pulse rate but allow more complex signal modulation allowing data to be packed more efficiently into the pulses -- and that later made its way (with even more improvement) into the Ghost Rider RDs and later Hermes Buoys.

Right, using multiple transceivers can be used to overcome some technological limitations like the rate limit on cycling. It's another form of multiplexing.

Also note how multiple receivers can be used to increase the signal and lower the noise ratio too.

Please also understand this is military application. We're used to civilian uses, where we have one shared resource (the spectrum) and we must all use it. Civilians also expect that the power expenditure be kept to a minimum, either because it costs money to pay for the energy bill, or battery weight or battery time. In a military application, they will have fewer constraints on power and they also have a monopoly on the resource. They can use the entire spectrum and, if in doing so, you impede your enemy's ability to communicate, well, that's a feature not a bug.

Fair, even those early drones may have had a symbol rate greater than their pulse rate. But I'd still argue that it couldn't be that much higher. Here's the full description.

Honor of the Queen wrote:“Our R&D people have been working on a new approach, however, and for the first time, we now have a limited FTL transmission capability.”
“An FTL capability?” Calgary blurted, and he was far from alone in his astonishment, for the human race had sought a way to send messages faster than light for almost two thousand years.
“Yes, Sir. Its range is too limited for anything other than tactical purposes—our best transmission radius is only about four light-hours at this time—but that’s quite enough to give us a marked advantage.”
[snip]
“The power requirement is enormous—our people had to develop an entire new generation of fusion plants to pull it off—and that’s only the first problem. Designing a pulse grav generator and packing it into the drone body came next. As you can probably imagine, it uses up a lot more mass than a drive unit, and it was a monster to engineer. And there are certain fundamental limitations on the system. Most importantly, it takes time for the generator to produce each pulse without burning itself out, which places an insurmountable limit on the data transmission speed. At present, we can only manage a pulse repetition rate of about nine-point-five seconds. Obviously, it’s going to take us a while to transmit any complex messages at that rate.”
“That’s true,” Honor put in, “but what we propose to do is program the onboard computers to respond to the most likely threat parameters with simple three or four-pulse codes. They’ll identify the threat’s basic nature and approach in less than a minute. The drones can follow up with more detailed messages once we’ve started responding.”

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.

Now as things improve, yes, they probably do improve the bits per pulse in addition to improving the pulses per second.



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.

clancy688 wrote:Heya,

I'm currently in the process of relistening to the Honorverse novels, and once again I came across one specific Manty technology leap which always struck me as completely unbelievable. Yeah I know, this is SciFi and most tech is made up anyway, but even though SciFi shouldn't exactly be "realistic", it should at least try to be believable. And this certain piece of tech is, at least in-Honorverse, not.

/rant_end

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).

IIRC correctly, the first time we saw the really high-bandwidth use of the FTL Comm was in Shadow of Saganami which was toward the end of the inter-war, or Ceasefire, years.

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.

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.

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.