I feel odd even asking that question, but one of my practice tests asks:
The IEEE 802.11-2007 standard defines WLAN communications to operate in which of the following frequencies? (Choose all that apply.)
A - 2.4 GHz
B - 900 MHz
C - 5 GHz
D - 2.4 MHz
I immediately selected ABC as the answer as those are the three ISM bands and as it turns out I got it wrong.
Here was the "Show Answer":
DSSS (802.11), HR-DSSS (802.11b), and ERP (802.11g) all operate in the 2.4 GHz frequencies. OFDM (802.11a) operates in the 5 GHz frequencies. HT (802.11n) devices can operate in either the 2.4 or 5 GHz frequency bands.
So now I'm wondering...
Is 900MHz a legacy band now, no longer covered by 802.11-2007, or presumably 802.11-2012?
I tried to look it up but apparently the IEEE charges you to download their stuff.
While the 900mhz was one of the ISM bands, it was never part of 802.11
They are all valid Radio frequencies but only 2.4 and 5 GHz are used for WLAN (802.11). In some countries, 4.9 GHz and other other frequencies are also used for public safety or other government functions.
So, indeed out of options given, only 2.4 Ghz and 5 GHz are correct.
What's making me nuts...
No, wait... I was nuts when I got here.
What's bugging me is that I can't seem to find anything in the official material that makes this distinction clear. Maybe I'm just missing it, but I honestly can't find a definitive statement on it.
Do one thing then: Download the 802.11-2007 standard pdf and then search for "900" or "902". There is not even a single reference. Do this for 2.4 and 5 GHz you would get a reference on each page almost.
When I went to the IEEE site to read the documents for myself I discovered they had a Pay-Wall.
BTW, I believe everyone. I was just surprised to discover it.
No, there is no payment needed.
Enter your email address and you are good to go:
I wish I could upload it for you here. But, for some reason, upload file option is giving an error.
This is covered in the CWNA Official Study Guide in Chapter 5 - IEEE 802.11 Standards. When you read through the history of the standards, you learn that 802.11 prime defined 2.4 GHz operations and that 802.11a introduced 5 GHz operations. You will notice that 900 MHz is missing from the chapter. On page 164, Table 5.1 is the most concise overview of the information required, so this would be a good table to memorize.
Hope this helps,
Respectfully, the problem there is that it's like knowing your doorbell is broken. You kind of have to hear it not ring.
While I am now perfectly clear on the subject, and thank you to everyone who chimed in; maybe the next revision could have a once sentence note calling attention to the fact that although 900MHz was covered in the ISM that readers should note that it is not defined by 802.11?
Just a thought.