Which four options are the characteristics of the original 802.11 protocol? (Choose four.)
A.
Defined DSSS and FHSS as possible methods for modulation
B.
Designed to operate in the 5 GHz ISM frequency spectrum
C.
The most common deployment is three non-overlapping channels that are 20 MHz wide
D.
The protocol sets the maximum throughput at 1 Mb/s or 2 Mb/s
E.
Defined FHSS and OFDM as possible methods for modulation
F.
The most common deployment is three non-overlapping channels that are 22 MHz wide
G.
Designed to operate in the 2.4 GHz ISM frequency spectrum
H.
The protocol sets the maximum throughput at 1 Mb/s
Explanation:
I think there is a mistake here since the original 802.11 standard defines DSSS and FHSS as mosulation methods and both of them use 22 MHz wide channels. OFDM in turn, which came afterwards, use 20 MHz wide channels.
I think the trick is that each channel is 5MHz wide and deployment was suggested on 1,6,11 meaning that it is 20MHz.
you are right Daperzoid!
Correct answers are : A,D,F,G
your all not right, original 802.11 standard defines DSSS and FHSS and uses 20MHz channels, refer to http://en.wikipedia.org/wiki/IEEE_802.11, so the answers are correct!
Daerzoid , I’m sure you right
Guess we would have to check the original 802.11 standard. However, from Cisco book:
“FHSS is still described in the original 802.11 protocol, but another technique was preferred and adopted by all 802.11 networks:
Direct Sequence Spread Spectrum. Instead of small channels and a jumping sequence, the information is sent over a wider channel.
This channel is 22 MHz wide”
If the wider channel is 22 MHz it implies FHSS allowed for smaller channels.
I think the big part we are missing is the never-forgiving wording “The most common deployment”…
The 802.11 DSSS separates 2.4 ISM band into 11 overlapping channels spaced 5MHz. The 802.11 transmitter always sends symbols (1 or several chips) at the rate of 11Mbps, which requires 22MHz bandwidth. The 802.11 does not use the benefits of the multiple coding sequences.
https://www.okob.net/texts/mydocuments/80211physlayer/
Moreover, who gives a rat’s fuzzy butt? We’re 15 years past that spec and the question should not be on a test in 2013. More craptacular minutia to randomly disqualify otherwise qualified technical resources by virtue of a poorly written test.
So it’s 2015 and this question is still there, however, we now have a new official cert guide publication for this exam released in february 2014 to help further the arguments. Please remember though that the key to answering the question is not about knowing what is actually right or wrong based on the defined standard (we can all read just fine) it’s about what we think Ciscos interpretation of the correct answer is because that is all that matters within the question’s environment. That said, here is their official wording from the mouth of the beast in their latest publication…
…
p27 – Whatevr advantages fhss gained avoiding interference was lost because of the following limitations… narrow 1mhz channel bandwidth, limiting data rate to 1-2mb.
p27 – (DSSS) Each channel is 22mhz wide…/snip In the 2.4ghz band where dsss is used, there are 14 possible channels, but only 3 of them that do not overlap.
p31 – dsss spreads the chips of single data stream into one wide 22mhz channel. It is inherently limited to 11mbps data rate because of the consistent 11-mhz chipping rate that feeds into the rf modulation.
p52 – original 802.11 standard publication in 1997, only transmission types available for use were fhss and dsss (dpsk,dqpsk).
…
Since no channels of 20mhz width were publicized in the original 802.11 standard (according to the documentation provided by the people who wrote the book and wrote the exam) I have to assume answer C is incorrect.
Other interpretations?