F 35 Sensor Fusion and networking

[charlielima223]

my and a question

I remember when the F-22 was coming out, one of the things that was touted about the F-22 was it's integrated avionics. Pilots often praised it as making their job easier. Now the F-35 is touted with sensor fusion. Obviously the F-35 has more processing power than the Raptor and now it would seem that for the Raptor "to be relevant" (was there ever a time when it wasn't?) it now has sensor fusion.

Integrated avionics... The Super Hornet has it. Typhoon has it. Rafale has it. Su-35 has it. F-16V will have it. F-15SA has it. So it seems that to look or stay relevant sensor fusion is being tossed around to every aircraft that has any level of systems integration. Other than wording was there any difference between the Raptor's "integrated avionics" and now this "sensor fusion"?

[les_paul59]

The sensor fusion term has been thrown around a lot, you are correct charlie. Lockheed's version of sensor fusion is different from the eurocanard's by being more advanced in nature. The f-35's avionics were based off of the successful maturity of the f 22

That being said other jets have some level of sensor fusion but its widely agreed upon that the f22 and f35 have the best

The raptor has had subsequent upgrades to improve the fusion since ioc, and to answer your question: All of the 4.5 gen jets have some fusion or "integrated avionics" but each jet is unique in the quality and level of sophistication inherent in the software.

its not black and white there are varying degrees of quality in between...case in point the euro-canards

[Scorpion82]

Scorpion do you honestly believe that in 5 years after the raptor gets a helmet and a 5th to 5th datalink, and a mode 5 iff that this discussion will even be relevant....honestly wake me up when the uk retrofits most of their typhoons with an AESA radar. The raptor had one in 03

The point of this discussion from my point of view is that it's not all black and white, unfortunately most people limit themself to this. It's as if one would say all Chinese are small, all Russian drink Vodka, all French are arrogant or all Americans are fat. These are stereotypes like 5th gens are superior and more advanced than anything else in every conceiveable aspect just by the virtue of being labeled 5th gen. Some people here are making fun joking about silly analogies. In comparison to the F-22 in particular the Rafale and Typhoon were both designed around the same time with only not decades appart where entirely different philosophies and technologies exists. That's being overlooked here completely and I'm convinced that any of the great analogy creators and distributors of silly one liners would be quite quick in pointing out that an advanced F-15, F-16 or F/A-18 variant is still very competitive to a Rafale or Typhoon. They would be right on that, but if they follow their own logic then it's impossible because "you can't retrofit", "they weren't designed to be capable of this or that" etc. I'm trying to create some awareness here and to motivate people to look beyond the horizon of buzz words and stuff randomly thrown around in such discussions in order to make a case, ignoring facts and avoiding common sense because it's so much easier to stick to black and white.

[les_paul59]

I agree with you scorpion, people shouldnt assume that the f-22 is superior in every way over a 4.5 gen but there ia a reason people called the raptor 5th gen in the first place

When it came out it was vastly superior than any other jet, recently the 4.5 gens have caught up by adding aesa radars and upgrading their esm suites.

I still think the fusion on 5th gens is better

[blindpilot]

... I'm convinced that any of the great analogy creators and distributors of silly one liners would be quite quick in pointing out that an advanced F-15, F-16 or F/A-18 variant is still very competitive to a Rafale or Typhoon. They would be right on that, but if they follow their own logic then it's impossible because "you can't retrofit", "they weren't designed to be capable of this or that" etc. I'm trying to create some awareness here and to motivate people to look beyond the horizon of buzz words and stuff randomly thrown around in such discussions in order to make a case, ignoring facts and avoiding common sense because it's so much easier to stick to black and white.

I appreciate your perspective on black and white versus grades of grey, but there comes a point where paradigm shifts need to have light shown brightly on the subject.

From 2006's Exercise Northern Edge in Alaska where the blue force (with 4th gen fighters working with a handful of F-22s) scored a 241-2 kill ratio, to later examples of F-22 doing ISR type coordination work over 2016 Syria, it becomes obvious that the subject is a lot more black and white than some would imagine. The game has changed, and the change is not just, or even mostly, stealth related. It is what is happening when the "integrated fused sensor network" whatever that is, is implemented at upper decision levels. It's not the integration per se, but the implementation that emerges at high level objective management.

So I return to a buzzword analogy one liner. The BlackBerry in 2011 was certainly technologically comparable to the iPhone, (gray) .... but RIM did not even know it was out of the game (black and white). Those are the facts, ignoring nothing. And the RIM folks on the unemployment line can see that clearly now, ... with their own 20/20 hindsight common sense.

Pretending a software and pod upgrade to an F-15 will be 90% effective all alone may end up becoming tragically delusional, unless it is flying wing on an F-35, where it "?""magically ""?" becomes 110% effective, with lesser upgrades. The framework has changed. When frameworks change, that is the definition of black and white. And just like what was shown in 2006, the Typhoons and Rafales can indeed be even more effective ... if they have a couple F-22/35s integrated into the blue force. I would assert these things unfolding in the F-22/F-35 are unique, and not evolutionary of things seen in other aircraft. That may be a difference of opinion. I'm sure President Obama thinks the BlackBerry is just as good/superior as an iPhone/Androids. That's an opinion too, held by 1.2% (well probably < 1.2% by now) of cell phone users.

Just saying,
BP

[hornetfinn]

'F-35 with regular EOTS targeting from 10 km away is likely much better than non-VLO platform targeting from 200 km away with some uber-targeting pod'?

That makes no sense. In a hypothetical world, however unlikely, what's better? Detect something from 200 km away moving through the air or 10 km?

Detecting something isn't targeting it. We are comparing targeting pods here and this means targeting things on ground. Targeting something 10 km away is far easier than targeting it 200 km away. First the sensor resolution and sensitivity would need to be at least 400 times higher in the latter case to have equal performance. Even if that was possible, the target would need to be on a perfectly flat ground without any obstacles (hills, mountains, trees, buildings) between it and targeting system. This would be very unlikely in real world situation 200 km away but would not be a problem 10 km away. Of course then there is the problem that no targeting system has laser or other methods to measure accurate range to target 200 km away.

Basically what I'm saying that being VLO gives F-35 possibility to go much closer to target and be much more effective than non-VLO platform even if the latter had much superior sensors. Of course EOTS is extremely good targeting pod and only some very latest podded systems have equal or possibly slightly superior performance. There is no podded system in existence or even in any designer dreams that would negate the advantages of stealth technology allowing going much closer to targets. Like every other targeting system, EOTS is going to be upgraded in the future. Right now it's very close to top when it comes to targeting systems anyway. What makes it even better is the fact that it's very tightly connected to sensor fusion engine of the jet unlike any podded system is.

[KamenRiderBlade]

I can't wait till they port the Sensor Fusion technology to other platforms.

Imagine Tanks with Sensor Fusion.

Soldiers with Sensor Fusion.
- Helmets having 360 EO/IR degree camera's fused with GPS data.

Ships with Sensor Fusion

Subs with Sensor Fusion

[hornetfinn]

Could you tell what more advanced technologies any 4th gen fighter has that F-22 lacks besides IRST?

You mean besides JDTIS vs MIDS, lack of HMD, a pending MODE 5 IFF capability for example?

Those have almost zero impact on sensor fusion though and all are going to be implemented in near future AFAIK. Btw, I don't get what you mean with "JDTIS vs MIDS"? F-22 currently can receive Link-16 messages which it can use in sensor fusion just like other fighters. Sending Link-16 messages would have zero impact on F-22 effectiveness although it will improve capabilities of other fighters using Link-16 only.

I agree though that there are some features in some advanced 4th gen fighters that F-22 currently lacks. However when it comes to sensors and sensor fusion, IRST is really the only thing F-22 lacks.

All sensor fusion engines give tracks as outputs but the methods to get there are different.

What 4++ gen (Rafale, EF Typhoon for example) sensor fusion does is:
1. Pilot operates and tasks the sensors how he sees fit.
2. Datalink shared tracks between fighters within seconds from commencing tracking and update interval is usually several seconds so accuracy is pretty poor for sensor fusion
3. Each sensor generate detections and correlates them to tracks inside the sensor. ID is done by individual sensors if possible.
4. Tracks from each sensor is sent to sensor fusion engine
5. Sensor fusion engine correlates tracks to single displayed track file.
6. Single track is displayed to pilot



5th gen sensor fusion works differently:
1. Sensor fusion engine tasks the sensors automatically
2. High-speed intra-flight datalinks (IFDL and MADL) share sensor data between aircraft very quickly and target data accuracy is very high and up-to-date.
2. Each sensor sends all the information they generate to sensor fusion engine after some preprocessing. Each sensor can still generate detections and tracks by themselves also if tasked by sensor fusion engine
3. Threat libraries and other such data are used by sensor fusion for example to ID targets from all the sensor data available
4. Sensor fusion engine generates detections from all the sensor data and correlates them to tracks
5. Single track is displayed to pilot

That's 1. a mere listing that doesn't distinguish between what individual platforms are capable of and 2. not entirely accurate with regards to what the sensor fusion process looks like on the Typhoon or Rafale for example. I can't say too much about the Rafale here, though there is some evidence that it performs better in this field than Typhoon does. The DL limitations in their present form are granted, as are the limitations of the M-Scan radar onboard the aircraft, but ID fusion is done by these aircraft's fusion engine as well with the ID data being weighed according to mission data tuneable rules to produce a reliable single target type identity and allegiance. The tasking of the sensors is to some extend automated as well, but not fully automated. One also needs to detail what tasks exactly are automated, but that's apparently something which goes into the realms of classification and that's the problem with this discussion in general, generic statements and buzz words are thrown around but little apparent detail is provided to actually work out the actual differences and not the gross unspecific listing on the slides of one manufacturer's presentation.

Can you show me any documentation that supports your claims? All I've found is what I described above. Sure there might be some similarities to 5th gen sensor fusion, but there are still several factors severely restricting sensor fusion capabilties in all 4th gen fighters:

1. Connection from sensors to sensor fusion. This means databus architecture, bandwidth and latencies. Best 4th gen systems have 20 Mbps max speed databuses (STANAG 3910 type). Most F-22 and F-35 have 20 times higher speed databuses (IEEE 1394b) with growth potential to at least 8 times higher speed still. In real life the difference is larger due to many factors. That is huge difference for sensor fusion and presenting information to pilot also. You have to remember that AESA radars and modern IRST systems can generate data at very high rate.

2. Data transfer rate between fighters. Like I said earlier, the data transfer speed is likely tens if not hundreds of times faster between F-35s and F-22s than in 4th gen fighters which all have Link-16 or equal datalink. All aircraft and all their sensors in F-35 or F-22 flight contribute a lot to sensor fusion whereas it's not really so with 4th gen fighters. Basically 5th gen systems are fusing information from many different sensors geographically separated by tens of kilometers.

3. Stealth. This means ability to go closer to enemy without being detected and thus being able to gather more and more accurate information using the sensors. Even if sensors and sensor fusion were equal, this still gives huge advantage in SA.

While first two could theoretically be installed on 4th gen fighters, their architectures and avionics systems would have to be totally rebuilt. Since the systems have these limitations, it's likely the computing and signal processing systems in sensor fusion engine would need to be significantly upgraded also along with a lot of software. It's like nothing stops installing sensor fusion engine and advanced sensors to 1st gen jet fighters if you modify them enough. Theoretically doable but nobody is going to do it since it costs a lot of money.

I don't see any difference to fusing tracks. There might similarly be no subsequent detection or that closely spaced targets are erraneously fused. It depends on sensor fusion algoritms to handle such problems. Actually fusing at lower level gives a lot more tools to handle them, although it's admittedly more difficult to do properly.

If you have a track you have a confirmed target, ofcourse you can lose that one, but if you have a single detection you have an intermediate bearing and/or range only which is static by nature. Only through the correlation of succesive detections it is actually possible to determine a target's velocity, closure rate, heading etc., also enabling the fusion engine and/or sensor to calculate a track's likely position within the next scan frame. Arguably initiating tracks is not to difficult for an AESA radar or starring IIR array and almost instant. The building of tracks within a centralized place still requires processing to be performed on all individual sensor detections, whether that's done by distributed units or within a single unit doesn't make too much of a difference. But yes there is one particular advantage of doing it this way you may use spurious sensor detections to update existing tracks, whereas such detections would be displayed as such or surpressed altogether when the processing is done elsewhere but no correlation with existing tracks would occur. Raw detections could however also be passed to the fusion engine without further processing in theory, there is no apparent technical limitation that would prevent this within a distributed architecture. The main difference between the federated and distributed systems architecture is that in the former case the processing cards are spread across multiple LRIs, whereas in the latter case they are cramed into a single LRI. You still have the distribution of data processing among the different modules that's why for example there are 66 slots per ICP on the F-22.

The difference is that in 5th gen system that all the data from all the sensors is handled in one system whereas in 4th gen systems the individual sensor handle their own data and then handle only the data they consider important (their own tracks or possibly detections) to sensor fusion engine. The sensor fusion in 4th gen systems is unaware to how the sensors decided what signals are important and what not. 4th gen systems don't have data transfer and likely also computing capacity to do it otherwise.

One significant advantage of 5th gen sensor fusion systems is that in the event of one sensor detecting something, but still not strong enough to create a track or even good detection, the sensor fusion can use other sensors to try to find out if that was actually something important.

[hornetfinn]

I can't wait till they port the Sensor Fusion technology to other platforms.

Ships with Sensor Fusion

Ships are one of the first platforms where sensor fusion has been implemented. They have all the sensors and are easy to install computing systems as weight and volume is not much of a problem compared to fighter aircraft.

[bigjku]

I question the basic assumption that it is even relevant if some aircraft is 80% as effective as what it is up against when it comes to sensors and stealth. If we put both up against a 4th generation opponent that is great I suppose. But if they are up against an F-22 or F-35 or Pak-fa (assuming it has a lower RCS than existing aircraft which seems slightly questionable) then what good does that performance do you? The Eurofighter or Su-35 is still going to be shot down in appealing numbers before they even know what is around. In the vast majority of scenarios those with 5th generation aircraft can collect their disproportionate kills go home and come back and do it again until the other side is dead or so terrified of flying they won't go up anymore.

Look at the history of near peer air combat. Small technical advantages have led to huge kill disparities until corrected. The main difference being you can't as easily make up the difference now as you could in WWI or WWII. But you can see periods where one side enjoyed a technological edge and would obtain a massive kill ratio in its favor. The results of the exercise pitting the F-22 against other aircraft aren't a mistake. The F-35 wil do nearly as well. They will see first, dictate terms of engagement and fire first almost every time. And history tells us those are the most highly correlate things to winning in the air.

[flighthawk128]

I can't wait till they port the Sensor Fusion technology to other platforms.

Imagine Tanks with Sensor Fusion.

Soldiers with Sensor Fusion.
- Helmets having 360 EO/IR degree camera's fused with GPS data.

Ships with Sensor Fusion

Subs with Sensor Fusion

As Hornetfinn said, ships already have sensor fusion. That's how they network the battlespace within a carrier group; I believe you can link the fire control radars together if necessary as well. Some ground vehicles also already have sensor fusion; it's called IVIS. It's in Abrams and Bradleys, and networks information throughout all other IVIS equipped vehicles.

Soldiers and subs will be more difficult. Soldiers will have to be able to see the data in real time, while also remaining vigilant to their surroundings; quite a difficult design challenge. Subs can't even communicate via normal means without nearing the surface, so there's physically a communication barrier that must be overcome first; also quite a daunting design challenge. I'm sure they've looked at possible solutions to these, but decided they weren't feasible (Future Solder program for the grunts; I don't have any data regarding the subs although I'm sure they've tried). Maybe when tech advances a little more, we may be able to accomplish these.

Now... I'm more curious as to linking ground vehicles' IVIS with the ships' sensors with the planes' sensors. THAT is a challenge to do, but will grant command (and individual elements) almost a complete holistic view of the battlefield. Pretty cool stuff, and it's starting to advance to a hyperwar stage where all the friendlies know where each other are, and have a fairly good/clear picture of the opposition. As it shows time and time again, good accurate information is the key. All the better to smash them with!

[Scorpion82]

Those have almost zero impact on sensor fusion though and all are going to be implemented in near future AFAIK. Btw, I don't get what you mean with "JDTIS vs MIDS"? F-22 currently can receive Link-16 messages which it can use in sensor fusion just like other fighters. Sending Link-16 messages would have zero impact on F-22 effectiveness although it will improve capabilities of other fighters using Link-16 only.

I was talking about technologies employed here in general based on my previous statement which you queried. But as we are at it, IFF is very relevant for sensor fusion! A friendly IFF response not only tells you friend or unknown, it can also tell you a lot more things such as altitude, more detailed ID data etc. very valuable in and contributive to maintain awareness of friendlies and to avoid fracticides. It is theoretically even possible that in case of sector interrogations you may detect objects that are not yet detected and tracked by your onboard sensors. Transponder detections could be correlated with other sensor tracks to help obtaining ID data without interrogating platforms, so it's very relevant for the sensor fusion process and MODE 5 offers quite some interesting new capabilities that are not present on MODEs 1 to 4.

As far as the JTIDS onboard the F-22 is concerned it would be interesting to know to what extend it has been updated to cope with the steadily growing data sharing capabilities of MIDS in general. It's true that "sending" JTIDS messages would have no apparent impact on the F-22's own capabilities, but it also contradicts what people here generally attribute to 5th generation fighters, the "data distributors and gatherers". Right now the F-22 can benefit from LINK16 networks and from data sharing between F-22s via IFDL (btw is it known how many F-22s can be linked up through IFDL at once?), but itself can't share anything with the rest of a fighting force, unless you have some relaying platforms such as BACN which I consider as an "okay workaround" but not as an optimal solution, especially in contested environments, Raptors can only share data among each other. This may well change in the future, but it remains to be a limitation for the time being. That's also a reason why I personally prefer to discuss more specific examples instead of generalising it to 5th gen or whatever. The F-35 is in this department a very different beast. Btw, albeit I have outlined it before the F-22 only fuses LINK16 feeds since Inc. 3.2A, or in other words "the all fusing" super fighter didn't fuse the feeds from anyone other than his own breed for about a decade!

As far as the HMD is concerned, yes it's not a sensor itself, though it can be used to cue sensor and weapon seekers or to designate targets in head up conditions or to generate a rapid waypoint or point of interest shared via DL at a glance into the outside world. Displaying tracks/targets inline with the HMDs FoV additionally enhances the pilots SA and enables him to keep his head up more often and for longer periods.

Can you show me any documentation that supports your claims? All I've found is what I described above. Sure there might be some similarities to 5th gen sensor fusion, but there are still several factors severely restricting sensor fusion capabilties in all 4th gen fighters:

1. Connection from sensors to sensor fusion. This means databus architecture, bandwidth and latencies. Best 4th gen systems have 20 Mbps max speed databuses (STANAG 3910 type). Most F-22 and F-35 have 20 times higher speed databuses (IEEE 1394b) with growth potential to at least 8 times higher speed still. In real life the difference is larger due to many factors. That is huge difference for sensor fusion and presenting information to pilot also. You have to remember that AESA radars and modern IRST systems can generate data at very high rate.

For the Typhoon, which is the aircraft I'm best informed about, there are some direct highspeed connections between specific LRIs beyond the STANAG3838 & 3910 busses utilized by the 7 sub-systems. T3 aircraft are designed with a high speed data network specifically to cope with the growing demands of data transfer capabilities and with hindsight of future, more capable sensors incl. Captor-E, but also others. There are also provisions for a GPMC, whereas the existing processing systems have been upgraded a couple of times already.

2. Data transfer rate between fighters. Like I said earlier, the data transfer speed is likely tens if not hundreds of times faster between F-35s and F-22s than in 4th gen fighters which all have Link-16 or equal datalink. All aircraft and all their sensors in F-35 or F-22 flight contribute a lot to sensor fusion whereas it's not really so with 4th gen fighters. Basically 5th gen systems are fusing information from many different sensors geographically separated by tens of kilometers.

LINK16 DLs have seen a couple of upgrades themselves incl. the ability to share data a high rates, with update rates being boostable for specific tasks to be accomplished. How that actually compares to the performance of IFDL or MADL escapes me, though I believe that at least MADL and possibly IFDL as well maintain a sizeable advantage here. Apparently the USAF has at leased raised the idea to integrate MADL on 4th gens as well, whether that's just a fictional consideration or something that has been accessed as part of a feasibility or risk mitigation study already is unknown to me, however.

3. Stealth. This means ability to go closer to enemy without being detected and thus being able to gather more and more accurate information using the sensors. Even if sensors and sensor fusion were equal, this still gives huge advantage in SA.

This is indeed a very real advantage and the reason why I consider VLO in combination with fighter performance as the real discriminator of 5th gens in comparison to 4th gens. That's definitely a capability that you are not going to retrofit.

While first two could theoretically be installed on 4th gen fighters, their architectures and avionics systems would have to be totally rebuilt. Since the systems have these limitations, it's likely the computing and signal processing systems in sensor fusion engine would need to be significantly upgraded also along with a lot of software. It's like nothing stops installing sensor fusion engine and advanced sensors to 1st gen jet fighters if you modify them enough. Theoretically doable but nobody is going to do it since it costs a lot of money.

That analogy is far exaggerated and I hope it's only presented that way for illustrative purposes, because it's not doable to fit a 1st gen aircraft with such technologies, not even theoretically. For advanced 4th gens still in production it's still a very real prospect of achieving this. Many of the technologies employed on these aircraft are quite competitive and I'm not talking about individual systems that are missing on this or that platform, but systems similar in function, i.e. navigation sensors and systems, radios, recording equipment, armament control systems, but also sensors. Certain technologies developed for the F-22 for example have been leveraged to design systems for other aircraft, the AN/APG-80 for example though it's probably no the best one.

The difference is that in 5th gen system that all the data from all the sensors is handled in one system whereas in 4th gen systems the individual sensor handle their own data and then handle only the data they consider important (their own tracks or possibly detections) to sensor fusion engine. The sensor fusion in 4th gen systems is unaware to how the sensors decided what signals are important and what not. 4th gen systems don't have data transfer and likely also computing capacity to do it otherwise.

Within one LRI, but not necessarily within one processing module, that's why there are 66 processing cards within the CIP! The ICP is in comparison significantly more performant with fewer modules to begin with. Some dedicated processing modules are required as certain types of data need certain types of processing and there is subsequently still the need to process data from different sources on different boards, which is like processing data in different LRIs which are fully interconnected. There are two key advantages for the modular processing unit however, first the boards pass data internally and not through data busses interconnecting different LRIs (particularly useful when the interconnecting busses are limited in performance) and you can emulate the software on identical boards providing some more redundancy. Other advantages of such a configuration, but unrelated to the avionics capabiliities itself are lower weight, volume, cooling and power consumption weighing 1 or 2 such LRIs against potentially many. The "many" is relative however as all modern 4th gens meanwhile process an increasing amount of data in fewer processing LRIs which could be described as some kind of cut down CIP/ICP. In some cases such as the Rafale the aircraft in fact features a very similar architecture to the ICP/CIP with its MDPU. There is a presentation available here: http://www.docdatabase.net/more-dassault-aviation-feedbacks-on-its-military-and-civil-ima-applications-273187.html

One significant advantage of 5th gen sensor fusion systems is that in the event of one sensor detecting something, but still not strong enough to create a track or even good detection, the sensor fusion can use other sensors to try to find out if that was actually something important.

There is no real practical limitation why that shouldn't work on 4th gens either, though I doubt that any of them does this at this point. However, there are two fold limitations to this philosophy, first stong enough single detection to track isn't going to work as tracking is a continues process as I have explained before already. Secondly there are limitations wrt to cueing/looking after something. The only two sensors capable to actually look for something onboard the F-35 are the radar and the EOTS. The DAS "sees" or not, ESM receives or not neither can be cued, but both can cue the radar or EOTS. In case of the F-22 only the AN/APG-77 could look after, but one would assume that it can't be in the interest of a VLO platform to ping at any conceivable position where something has been noticed briefly as this would compromise LO. In some situations it might surely make sense, though but there are both limitations and trade offs to accept when doing so.

[cantaz]

Maybe BP can chime in on this, but aren't all databus in use on 4th gen variations of 1553? Meaning architecturally limited to half-duplex, command/response? Doesn't matter if the implementation is copper or fiber. That should by definition differentiate how each gen does fusion, given that beside the massive difference in speed between even the fastest 1553 implementation vs the slowest 1394, the way data can be routed within each bus type is quite different.

[hornetfinn]

Maybe BP can chime in on this, but aren't all databus in use on 4th gen variations of 1553? Meaning architecturally limited to half-duplex, command/response? Doesn't matter if the implementation is copper or fiber. That should by definition differentiate how each gen does fusion, given that beside the massive difference in speed between even the fastest 1553 implementation vs the slowest 1394, the way data can be routed within each bus type is quite different.

Yes they do. Eurofighter Typhoon, Dassault Rafale and Super Hornet have STANAG 3910 type fast (20 Mbps) databus channel which is basically faster 1553 databus. It's definitely possible to improve the speed of these systems with many types of upgrades but there are still serious limits to what could be done with these types of databuses. They are great for many applications where speed and low latency is not really required. IEEE 1394b type databuses are much better where high speed and low latency is required due to their higher speed (400 Mbps standard to 6400 Mbps currently possible) and asynchronous transmissions (lower latency and responsiveness). They also offer the advantage of lower weight and volume requirements which means more channels can be easily installed. For example AFAIK, F-35 has far more databus channels than any other fighter aircraft which leads to massive advantage in terms of data transfer capabilities. I don't know of any 4th gen system that has anywhere even remotely similar capabilties even planned.

[jetblast16]

'...the F-22 only the AN/APG-77 could look after, but one would assume that it can't be in the interest of a VLO platform to ping at any conceivable position where something has been noticed briefly as this would compromise LO...'

Not necessarily. That is where LPI(R) comes into play. Passive detection (photon catching) is best in certain situations, but it has its limitations (range, atmospherics, etc)