I don't know the answer to why the 2.4GHz ISM band is at 2.4GHz, but I do know the answer as to why the 2.4GHz band was chosen over others. (I also know why the 61.5 GHZ ISM bad was chosen to be 61.5GHz.)
The choice of the 2.4GHz band needs to be seen in the context of 1995, when the first WLAN prototypes were built.
The lower limit was set by the desire to have the smallest antennas possible, to allow WLAN equipped devices to be portable. The higher the frequency, the smaller the wavelength, the smaller the antenna.
The upper limit was set by what was technically possible in 1995. The desire was to use cheap CMOS technology to build WLANs. In 1995, it was just possible to build a 2.4GHz radio in CMOS and research was in progress to build a 5GHz radio.
Consequently the first WLANs came out at 2.4GHz. Since then, WLANs have remained at that frequency for compatibility reasons (Metcalfe's law). 802.11a was defined to be 5GHz, because 802.11a came out after 802.11b and by then a 5GHz radio was possible in CMOS. Due to the dominance of 2.4GHz, 802.11g was later defined to be 802.11a at 2.4GHz, to take advantage of readily available 2.4GHz RF components, and allow 802.11a rates without having to have a dual-band radio.
61.5GHz was chosen for ISM because it is heavily attenuated by oxygen the atmosphere. This makes it unsuitable for long-range communications, but great for short range, since the high attenuation provides a degree of isolation between networks.
I'm looking at this from the point of view of the technology, rather than the standards, as that's where I was involved. From a technology point of view, 802.11b (particularly its 1 and 2Mbps modes) was developed before 802.11a, and so is "older". I know this, because I had the design for the world's first 802.11a modem on my computer's screen, and one of the professors had earlier bought an instance of a DSSS WLAN (essentially 802.11b) to see how it performed.
Granted the early "802.11b" radios might not have been CMOS. Their frequency was limited by what was technically possible in a consumer product though. I can't remember exactly what was in that "802.11b" WLAN. The 802.11a band was definitely set by what was possible in CMOS. The CMOS radio itself might not have existed in 1995, but planning was in progress and we had a pretty good idea of what was possible.
802.11b was CCK modulation (and to a lessor extent PBCC, but that didn't take-off).
DSSS wasn't 802.11b, it was 802.11 (or half of it, the other PHY at that point was FHSS). 802.11b's 1Mbps and 2Mbps modes were DSSS, and pre-existed 802.11b. These (and the FHSS PHY) were all part of the 1997 standard. 802.11b and 802.11a came along in September of 1999.
Who is 'we'? Because you don't seem to know what you're talking about.
I'm one of the other authors. Maybe I'm wrong, in that the written history tells it differently, but I'm recalling what was said around the meeting table and across the office partition. I might be a bit loose with the terminology, but to me it's not packaged up neatly into standards, as it was a non-linear development process when I was dealing with it.
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Edit: fix URL + name
after a little googling i can find references to papers pblished in 1994 and 1995 that refer to GHz CMOS components (eg A. Rofougaran et al., A 1 GHz CMOS RF
Front-end IC with Wide Dynamic Range,
ESSCIR, 1995, pp. 250-253; J. Carols and M. S. J. Steyaert, A 1.5 GHz Highly
Linear CMOS Down Conversion Mixer, IEEE
Journal of Solid-State Circuits, Vol. 30, 1995,
pp. 736-742.)
i know nothing about this, so perhaps they are irrelevant, but on face value it seems like a 2.5GHz system could have existed in labs at that date, or at least was clearly going to be possible.
Given that the FCC is funded by the taxpayers I find it frustrating that the FCC document archive is sitting behind a paywall-esque system. Is there a good reason for this?
With all the money it costs to physically store and maintain the documents, I would imagine that they could instead scan and index them, and then put them up online and make them available to taxpayers for free, since we (the taxpayers) have effectively already paid for it, and continue to pay for it continually.
How did the BCPI become the sole contractor to have access to these documents? How can I find out how this came to be?
document archive is sitting behind a paywall-esque system. Is there a good reason for this?
Traditionally the reason is it requires somebody to go find the physical copy, scan it, and send it to you.
I would imagine that they could instead scan and index them, and then put them up online
Physical archival, once archived, is pretty low-maintenance. They could scan and index them, but that costs something. Yes, the information in the documents has already been paid for, but transferring that information has not.
<sarcasm>Yes, what a boon for the public.</sarcasm>
Well, at least you can get access if you need it. Compared to zero access, I'd say that's a boon. Also a good first step.
They should have the policy that once someone requests a document it is made public (just the document, no the request). Bootstrap the digital index with the most interesting documents as suggested by public demand.
The National Archives should have jurisdiction for storing the documents of all federal agencies, departments and commissions. Just like the NSA has jurisdiction to secure every federal computer network.
It's the same reason that federally funded scientific research is only available in for-profit journals. Someone has to pay for the costs associated with publishing things, and the scientists/FCC don't want it coming out of their budget.
Of course, the money being paid to access papers in for-profit journals is also coming from the government, just in a less efficient way.
The cost of publishing - especially written documents - has dropped to essentially free in the last two decades, though. I hear your argument from time to time, but it's a really hard sell these days.
Well, to be precise, it's 2.4GHz and 902-928MHz, so, for completeness, you'll want to chase down both of them. (I spend a lot of time on 902-928 MHz at 1 Watt. )
It should be somehow connected to the width of roman roads, I'm pretty sure of it. But the connection is not an obvious one: "speed of light / 2.4 gHz / (56 1/2 inch) = 0.087041".
Is it really true that microwaves would work on that whole range of frequencies? I thought there was a water resonance at 2.4 GHz that they were designed to excite.
I would say that a lot of the rationale would come from:
1) Availability of the 2.4GHz band in other established countries
2) Propagation characteristics of 2.4GHz (this would also explain why the 900MHz ISM band exists given the better coverage) being relatively well known at the time
3) Separation, at least originally, from heavily populated bands at the time
Note that the $500 funding goal would only allow for 10 hours of discovery (exc. email & per-page costs), which may not be a lot if the investigator needs to find meeting minutes, memos and communications with other regulatory bodies from over half a century ago.
At the time there was very little going on that high up in the band, it seems that the US rep at the ITU Atlantic City conference was pushing for it to be a worldwide standard because of the possibility that the then fridge sized ovens (raytheon radarrange) would be used on ships, which would of course travel to other regulatory domains.
I don't think propagation was a factor at the time, as there doesn't seem to be anything special about that frequency. The S-band is also around there which works fine for long distance.
You're right, 500 won't go very far, but I was sceptical that anyone would care enough for it to get going at all! Great to see the response so far though. Happy to answer any questions - Hugh
I explain my take on the documents I've found so far, and the band's eventual rise to Wi-Fi fame a little better here, though I'll have to dig out the references page a little later http://www.skynet.ie/~teslacut/appendixA.pdf
Out of interest, have you tried approaching the University to see if they have funds available to help you out? That would be my first port of call - $500USD isn't much to them.
It certainly crossed my mind, but given financial constraints at the moment I didn't think they would jump on the idea. Also, this is a complete side topic for my real research, so I shouldn't even be doing it. It's tweaked some interest now though so they certainly might be more amenable, if nothing for the good PR.
They're making a big song and dance about being poor, but Universities still have tons of cash sloshing about :)
Fair point though if it's not something explicitly connected with your research - but good thinking about the publicity aspect of it :)
Best of luck with it all - please forgive my non-donation, I'm a student too and, as you know, it's feast or famine and this is the back end of a semester ;)
I always assumed those were set aside as unlicensed spectrum and that was why so many things existed along those bands. Probably also some propagation characteristics?
My guess would be that it has something to do with design considerations for early cavity magnetrons, which generate the radio waves for microwave ovens.
I suspect FCC simply allowed Raytheon to use whatever frequency its "Radarange" oven used. After all, Raytheon was the main radar producer for the US military. Presumably the military had a strong influence on FCC. Remember, it all happened in 1947, just 2 years after World War II.
Indeed, I strongly suspect the answer will be something along these lines. I have tried to research the operating frequency of the radarange, but have come up empty. If you click the 'contact us' link on the page you've referenced, you find this section:
Academic Research Assistance
We do not entertain requests for academic research assistance. Our web site is rich in both historic company information and current product material. Explore the links from our home page, Our Company, History, and search engine.
Which is disappointing, but perhaps I can reach an ex employee.
I always thought it was some balance of range vs bandwidth, some nonsense about lower frequencies having larger range but having lower peak data carrying capacity, and higher bandwidths having less range but more data.
Which still wouldn't explain why we didn't use low bands for cellular (all the time at least, hello 900mhz) and high bands for wifi.
We had 2.4 GHz systems working in 1992. They were crude frequency hoppers, but they worked and were designed to take advantage of the FCC rules for the unlicensed ISM bands.
The first WLANs that were similar to what we have today with APs and mobile clients were in the late 80s
It's crazy that everyone is using 2.4Ghz for Wi-Fi. My flat is swamped with 2.4Ghz WiFi all conflicting with each other for the 3 non-overlapping channels and the much larger 5Ghz range is completely unused.
Really? That sort of thing actually is part of my research. Could you possibly forward a screenshot of what it looks like? Netstumbler or the OS's wifi control panel. If you could also describe the urban environment (apartments or houses, how many occupants, etc) that would be amazing. Thank you!
Lots of networks is pretty common everywhere I look. In commercial buildings with lots of tenants it is even worse. I live in suburbia (detached houses) and can see between 5 and 10 networks depending on which corner of the house I am in. Only my own AP was on 5GHz, but discovered someone else has finally started using that range too. It also looks like several of my neighbours turn their wifi off when they are not at home!
If you want to collect this kind of data, then an easy way is to ask Android users to run "Wifi Analyzer" and use the Share menu to send you the results. It is a glob of XML but includes all the necessary details.
It is surprising to me just how many devices shipped today do. Quite why they do it I don't understand since I never see it mentioned in feature lists.
All Apple's laptops have for quite a while, however with the iPhone they still didn't have 5 Ghz on the 4s and only added it on the 5 - not that Apple let you run a WiFi analyzer on it anyway.
The Android Wifi Analyzer app shows what access points are detected and their signal strengths, channel usage, encryption etc. It is not a traffic sniffer - some screenshots at https://play.google.com/store/apps/details?id=com.farproc.wi... I couldn't find anything similar in the app store. I did find several apps that scan your local network (eg Fing).
No one mentions 5GHz in their specs. You can't tell from Google's Nexus pages which devices support it. Apple's older pages (eg Mac Mini) similarly don't say anything but newer pages (eg iPhone 5 and iPad) do. For any vendor about the only clue is they sometimes mention 802.11a support.
It's a good read, and one of my starting points, but I had already seen some official archival material that contradicted several of the article's claims. There aren't too many references given that can be chased down either.
Thanks for the suggestion, I hadn't, but I know that some friends of that sort of person have forwarded it on, so I'm trying to get in touch. Will certainly update everyone if that turns up something.
The choice of the 2.4GHz band needs to be seen in the context of 1995, when the first WLAN prototypes were built.
The lower limit was set by the desire to have the smallest antennas possible, to allow WLAN equipped devices to be portable. The higher the frequency, the smaller the wavelength, the smaller the antenna.
The upper limit was set by what was technically possible in 1995. The desire was to use cheap CMOS technology to build WLANs. In 1995, it was just possible to build a 2.4GHz radio in CMOS and research was in progress to build a 5GHz radio.
Consequently the first WLANs came out at 2.4GHz. Since then, WLANs have remained at that frequency for compatibility reasons (Metcalfe's law). 802.11a was defined to be 5GHz, because 802.11a came out after 802.11b and by then a 5GHz radio was possible in CMOS. Due to the dominance of 2.4GHz, 802.11g was later defined to be 802.11a at 2.4GHz, to take advantage of readily available 2.4GHz RF components, and allow 802.11a rates without having to have a dual-band radio.
61.5GHz was chosen for ISM because it is heavily attenuated by oxygen the atmosphere. This makes it unsuitable for long-range communications, but great for short range, since the high attenuation provides a degree of isolation between networks.