Why 2.4GHz? Chasing wireless history(indiegogo.com) |
Why 2.4GHz? Chasing wireless history(indiegogo.com) |
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.
CMOS radio didn't exist in 1995.
802.11a didn't come out 'after' 802.11b. 802.11a and 802.11b were ratified on the SAME DAY.
802.11g is a bit more than "802.11a in 2.4GHz".
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.
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.
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?
> Our office is inside of the FCC building and we have full complete access to FCC files,
> FCC divisions, FCC bureaus and FCC archives! We are the official contractor given top
> priority by the Federal Government in handling FCC documents to benefit the public.
<sarcasm>Yes, what a boon for the public.</sarcasm>
FWIW, I hate being so negative about this. But as is often the case with governmental affairs, this seems like total bullshit.
"Additionally, microwaves can melt certain types of rocks, producing small quantities of synthetic lava"
I know what I'm making for Thanksgiving.
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.
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
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.
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 ;)
http://www.wired.com/gadgetlab/2010/09/wireless-explainer/2/
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.
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Which is disappointing, but perhaps I can reach an ex employee.
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.
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.
There may be an old ham out there who remembers why 2.4GHz was reserved for ISM use.
edit: fixed typo, thanks lutusp
Ask yourself next time your pocket vibrates.
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.
http://www.archives.gov/research/guide-fed-records/groups/17...
BCPI seems like some sort of copy service / a service for people who do not want to fly in and physically visit the archives.
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.
You could even make it work in the lab, but holding a design in production wasn't possible then.
http://amasci.com/weird/microwave/voltage2.html
Teaser: the title is "UNWISE MICROWAVE OVEN EXPERIMENTS"
s/AARL/ARRL/
These can only be found by crawling through the top level directory, which I only found through Google. It's just not a priority for the FCC.
http://transition.fcc.gov/Bureaus/Mass_Media/Databases/docum...
http://transition.fcc.gov/Bureaus/OSEC/library/legislative_h...
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.
http://www.sss-mag.com/pdf/97_mmlan.pdf
Percival is an inventor on one of the fundamental WLAN patents (recently in the news):
http://www.google.com/patents/US5487069
Skellern and Weste were the founders of Radiata Communications, which was first to market with 802.11a, before being bought by Cisco.
http://www.computerworld.com.au/article/75649/cisco_acquires...
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. --- Edit: fix URL + name
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.