
Why 2.4GHz? Chasing wireless history - Bob_Sheep
http://www.indiegogo.com/why2point4
======
femto
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.

~~~
gonzo
Your post is full of errors.

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".

~~~
femto
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.

~~~
gonzo
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.

~~~
femto
"we" = the authors of this paper:

<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...](http://www.computerworld.com.au/article/75649/cisco_acquires_taste_radiata/)

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

------
jaytaylor
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?

<http://bcpiweb.com/fcc.php>:

> 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.

~~~
sliverstorm
_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.

~~~
jonknee
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.

~~~
anotherhue
I don't know why these documents have been scanned, but this is where I've
gotten all the online references so far. And no, there is no index :(

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/Mass_Media/Databases/documents_collection/scandoc/)

[http://transition.fcc.gov/Bureaus/OSEC/library/legislative_h...](http://transition.fcc.gov/Bureaus/OSEC/library/legislative_histories/)

------
ghshephard
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. )

------
dchichkov
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".

------
monochromatic
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.

~~~
elithrar
A myth! See <http://en.wikipedia.org/wiki/Microwave_oven#Principles> \- second
paragraph.

~~~
scarmig
I feel totally stupid for not knowing this. That's counteracted by what I now
know is possible, though:

"Additionally, microwaves can melt certain types of rocks, producing small
quantities of synthetic lava"

I know what I'm making for Thanksgiving.

~~~
scarmig
It also led me to find this:

<http://amasci.com/weird/microwave/voltage2.html>

Teaser: the title is "UNWISE MICROWAVE OVEN EXPERIMENTS"

------
elithrar
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.

~~~
anotherhue
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

~~~
anotherhue
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>

------
alexhawdon
Good luck with your search!

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.

~~~
anotherhue
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.

~~~
alexhawdon
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
;)

------
gprasanth
This wired article _seems_ to explain it:

<http://www.wired.com/gadgetlab/2010/09/wireless-explainer/2/>

------
rtkwe
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?

~~~
maaku
I think the Indiegogo is to find out _why_ 2.4ghz was chosen over other
possible bands.

------
phreeza
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.

------
ash
Some speculations:

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.

<http://www.raytheon.com/ourcompany/history/leadership/>

~~~
anotherhue
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.

------
zanny
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.

------
philb11
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

------
rythie
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.

~~~
anotherhue
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!

~~~
rogerbinns
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.

~~~
rythie
A lot of phones don't support 5Ghz though - so you would have to account for
that in your results.

~~~
rogerbinns
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.

~~~
rythie
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.

~~~
rogerbinns
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...](https://play.google.com/store/apps/details?id=com.farproc.wifi.analyzer)
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.

------
mef51
found this article interesting: [http://ca.gizmodo.com/5629814/giz-explains-
why-everything-wi...](http://ca.gizmodo.com/5629814/giz-explains-why-
everything-wireless-is-24ghz)

~~~
anotherhue
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.

~~~
tomkinstinch
Have you reached out to the ARRL or the equivalent International Amateur Radio
Union organization for your country?

There may be an old ham out there who _remembers_ why 2.4GHz was reserved for
ISM use.

edit: fixed typo, thanks lutusp

~~~
anotherhue
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.

------
ck2
Ah American democracy - freedom and knowledge for all, who can afford it.

------
thinkingtall
To give everyone cancer...

Ask yourself next time your pocket vibrates.

