Csiro invented wifi

[coppice]

Do modern wi-fi chips still support those old spread spectrum modes, for backward compatibility, or are they pure OFDM now? Interestingly, the 5GHz bands have always been exclusively OFDM. Spread spectrum was only used at 2.4GHz.

Hey, @coppice, do you have time to expand on the differences? I thought OFDM was one example of spread spectrum, but I'm no expert and keen to learn.

What is usually called spread spectrum uses a single carrier which hops around in some manner, so it spreads over a fairly wide band. Usually, multiple users are hopping over the same chunk of spectrum, with different hoping patterns, to keep them distinct. This can be very robust in the presence of interference sources, as with some redundancy and error detection/correlation in the protocol you can work around the chunks of data being sent when the carrier hits the interference frequency. OFDM uses the same carrier frequencies all the time, but you have lots of concurrent carriers within a band, separated in frequency in a way they keeps them orthogonal to each other. That is, not mutually interfering. At the receiver any carriers being hit by interference won't demodulate properly, while the rest will. Then with some redundancy and error detection/correction you can work around those problem carriers. The final result is interesting, as each carrier operates at a relatively low symbol rate for the total amount of spectrum being used, equalising away multi-path interference is much easier than with a single carrier of the same total bandwidth operating at a very high symbol rate. In mobile systems that's a huge plus, as the multi-pathing is constantly changing. Even in static applications, it can be a big win. Analogue TV suffered from ghosting due to multi-pathing, and those ghosts could be quite dynamic when there were trees blowing on windy days and so on. The OFDM TV standards just work.

So, spread spectrum is a relatively narrow band signal spread around a broader chunk of spectrum in a predetermined pattern which the receiver can follow. OFDM just fills an often quite large chunk of spectrum with carrriers, which are not spread around.

[NiHaoMike]

Its now 0% of wi-fi. I wonder how many things are left using spread spectrum? More importantly, does it have any interesting qualities that would make people use it for anything new going forwards? Perhaps in ULP applications that need some robustness?

Bluetooth still uses FHSS.

[Buriedcode]

I didn't think WiFi used FHSS apart from the very first standard, when it was quickly dropped in favour of the more resistant direct sequence spreading?

As with all modern standards, they're pretty complicated meaning that no one person actually "invented", but rather tens of different technologies, likely involving the contributions of thousands, with a combination of different breakthroughs and survival of various ideas eventually coalescing into a usable standard.

People still like to cling on to the idea of a lone maverick inventor/Doctor/Scientist who somehow fights the establishment and changes our world.  Sure, its happened, but its far more common that advancements are made incrementally across many fields - which makes it less appealing and much harder to assign credit.  Sure people like their heroes, but they often twist the facts to support them.

[SteveThackery]

What is usually called spread spectrum uses a single carrier which hops around in some manner, so it spreads over a fairly wide band. Usually, multiple users are hopping over the same chunk of spectrum, with different hoping patterns, to keep them distinct. This can be very robust in the presence of interference sources, as with some redundancy and error detection/correlation in the protocol you can work around the chunks of data being sent when the carrier hits the interference frequency. OFDM uses the same carrier frequencies all the time, but you have lots of concurrent carriers within a band, separated in frequency in a way they keeps them orthogonal to each other. That is, not mutually interfering. At the receiver any carriers being hit by interference won't demodulate properly, while the rest will. Then with some redundancy and error detection/correction you can work around those problem carriers. The final result is interesting, as each carrier operates at a relatively low symbol rate for the total amount of spectrum being used, equalising away multi-path interference is much easier than with a single carrier of the same total bandwidth operating at a very high symbol rate. In mobile systems that's a huge plus, as the multi-pathing is constantly changing. Even in static applications, it can be a big win. Analogue TV suffered from ghosting due to multi-pathing, and those ghosts could be quite dynamic when there were trees blowing on windy days and so on. The OFDM TV standards just work.

So, spread spectrum is a relatively narrow band signal spread around a broader chunk of spectrum in a predetermined pattern which the receiver can follow. OFDM just fills an often quite large chunk of spectrum with carrriers, which are not spread around.

Totally brilliant! Thank you for that excellent explanation. I've checked and as you said earlier, @coppice, modern WiFi doesn't use spread spectrum any more, although 802.11b used to. As such, I don't think we can give any credit to Lamarr for modern-day WiFi.

[SteveThackery]

As with all modern standards, they're pretty complicated meaning that no one person actually "invented", but rather tens of different technologies, likely involving the contributions of thousands, with a combination of different breakthroughs and survival of various ideas eventually coalescing into a usable standard.

Totally agree. WiFi is a massively collaborative effort. I don't think we can even use the word "invented" for it - perhaps "developed" is more suited.

People still like to cling on to the idea of a lone maverick inventor/Doctor/Scientist who somehow fights the establishment and changes our world.  Sure, its happened, but its far more common that advancements are made incrementally across many fields - which makes it less appealing and much harder to assign credit.  Sure people like their heroes, but they often twist the facts to support them.

Again I totally agree. That description probably expired around the end of the 19th century. Nowadays collaboration is pretty much the only way to push the boundaries forward.

[Siwastaja]

did invent the idea of frequency hopping spread spectrum as a means of avoiding both jamming and interception.

But in the end - I have invented frequency hopping, too. It is one of those fairly simple ideas, which just come to you when you have a problem to solve, and you can design them on a napkin. Frequency hopping specifically isn't a mathematically heavy concept; just come up with rules to switch frequencies, and have all participants follow them. These rules could be as simple as following a list, or maybe producing pseudo-random numbers with LFSR or similar.

What defines an actual real invention is how hundreds of such simple ideas are combined to implement something which works and is useful as a whole. And as such, many real inventions therefore belong to teams of people; many who remain unnamed but possibly contributed more than those whose names are written in books of history.

[coppice]

did invent the idea of frequency hopping spread spectrum as a means of avoiding both jamming and interception.

But in the end - I have invented frequency hopping, too. It is one of those fairly simple ideas, which just come to you when you have a problem to solve, and you can design them on a napkin. Frequency hopping specifically isn't a mathematically heavy concept; just come up with rules to switch frequencies, and have all participants follow them. These rules could be as simple as following a list, or maybe producing pseudo-random numbers with LFSR or similar.

Simply hopping around will get you some measure of stealth, but if its communications performance you are after you need to go further. You need to truly integrate all those "chips" of the signal to see a processing gain, and head towards the Shannon limit. That's when spread spectrum gets interesting for commercial use. When Lamarr published her ideas, the maths of that hadn't even been figured out. She was working in WW2. The channel capacity theorem wasn't developed until just after WW2. Similar things happened with other technologies in WW2. They chirped radars, so that they could pump out more intense pulses, without the peak energy causing flashovers in waveguides and so on. It wasn't until the early 60s that a proper mathematical analysis of how that smearing of the signal over time also brings a processing gain, and improves the radar's performance. I always find it odd that that took so long. Once you read Shannon from 1948, it kinda naturally follows.

[SteveThackery]

What defines an actual real invention is how hundreds of such simple ideas are combined to implement something which works and is useful as a whole. And as such, many real inventions therefore belong to teams of people; many who remain unnamed but possibly contributed more than those whose names are written in books of history.

Well OK - that's your definition of an invention, but it isn't the generally accepted one:

U.S. Patent Law: a new, useful process, machine, improvement, etc., that did not exist previously and that is recognized as the product of some unique intuition or genius, as distinguished from ordinary mechanical skill or craftsmanship.

It says nothing about how many people are involved.

But in the end - I have invented frequency hopping, too. It is one of those fairly simple ideas, which just come to you when you have a problem to solve, and you can design them on a napkin.

That's the problem with many inventions: once invented they seem obvious and trigger the usual chorus of "Well, I could have invented that!"  I think there are two things at play here. Firstly, as technology advances some inventions seem almost inevitable, and if one person didn't come up with it another would have done the next day. Secondly, it is often the case that we cannot send our mind back in time and appreciate what the intellectual landscape was like at the time. In 21st century eyes, spread spectrum seems so obvious it's like we were born knowing about it, but 85 years ago it was a very different world.

You claim to have invented spread spectrum yourself, presumably before learning about it. I don't believe you: anyone vaguely interested in modern technology will have heard or read about it - perhaps only at the most superficial level - by the time they are young adults. We are surrounded by this type of technology and an inquisitive mind can discover this stuff so easily these days. It's important to remember that Lamarr's intellectual breakthrough happened in the complete absence of modern day context. And the fact that her invention remained unused for 20 years does suggest that it was before its time, and that it wasn't obvious. When there is no obvious application, an obvious solution seems unlikely.

Anyway, I remain happy to give Lamarr full credit for it. I think observing a pianola and suddenly realising that the notes can represent different carrier frequencies, and by fitting out the receiver with the same piano roll and syncing their start, the two can send information that is secure and very hard to jam... well, I think it was a tremendous insight in the context of that time.

[edavid]

I don't think Lamarr could possibly be described as the (or 'an') inventor of WiFi. She invented frequency hopping spread spectrum.

She did not.  There was a great deal of prior art, and her patent doesn't seem to add anything important.

For all the details, see this excellent article:

https://www.americanscientist.org/article/random-paths-to-frequency-hopping

[TimFox]

Before retirement, the IP department of the parent corporation would send a patent attorney to summarize the law and encourage us to file patent disclosures with the company based on our work.
Legal definitions do not always correspond to dictionary definitions:  he reminded us that our inventions should make logical sense to us, but that did not necessarily mean "obvious" (obvious to one skilled in the art).

[ejeffrey]

Since wireless "ethernet" in the form of ALOHAnet predated wired Ethernet, the idea of the "invention of WiFI" is a bit of a dubious concept.  Obviously the 802.11 family of standards have a bunch of technical features including the spread spectrum techniques that were not present in ALOHAnet, but the thing that makes wifi important was the standardization process.  They collected a bunch of interesting and important technologies that already existed, combined them into a useful standard, and got vendors and regulators all harmonized so that it could be widely produced and used.

[Siwastaja]

My point is, question all superhero inventor stories unless you truly understand what the invention really was.

Real work is almost always a lot of teamwork (explicitly, and also implicitly by utilizing ideas of others, we are not in a vacuum) - and a lot of perspiration.

Making a big deal about having a patent is nearly always a red flag. 99.9% of patents are trivial or outright trolling. Laymen still awe patents and those who hold them, but if you have to actually read them (and I have had, filing my own), your eyes start bleeding.

[SteveThackery]

I don't think Lamarr could possibly be described as the (or 'an') inventor of WiFi. She invented frequency hopping spread spectrum.

She did not.  There was a great deal of prior art, and her patent doesn't seem to add anything important.

For all the details, see this excellent article:

https://www.americanscientist.org/article/random-paths-to-frequency-hopping

Thanks for the link - excellent article.

I think this is complicated. Loads of inventions have prior art, even though they aren't supposed to.  The article gives a great account of the complex ways new technologies emerge.  I'm sure a similar story could be told for all sorts of inventions. Also, the same thing might legitimately be invented more than once when the inventors are unaware of the prior art.  Does credit go to the first person to get a patent? Or the first person to come up with the idea? Or the first person to reveal their idea to the world? How can you prove those latter two?

As for Lamarr, we cannot know if she was aware of the prior art. It is also clear from the article that we cannot attribute the invention definitively to any other individual, either.  Several people were thinking along the same lines. Therefore I think we can safely say she was "one of the inventors of frequency hopping as a method of preventing jamming". This acknowledges that others were also thinking along the same lines, some of them well before Lamarr.

[SteveThackery]

My point is, question all superhero inventor stories unless you truly understand what the invention really was.

Real work is almost always a lot of teamwork (explicitly, and also implicitly by utilizing ideas of others, we are not in a vacuum) - and a lot of perspiration.

Making a big deal about having a patent is nearly always a red flag. 99.9% of patents are trivial or outright trolling. Laymen still awe patents and those who hold them, but if you have to actually read them (and I have had, filing my own), your eyes start bleeding.

I think that is spot on.  Heroic lone inventors are exceedingly rare, and every such story should be treated with scepticism.

In the case of Lamarr, she came up with a great idea, but we've no idea if she was aware of prior art. (I didn't realise there was so much, and I'm happy to stand corrected.)