| Exam 200-355 | Question id=2424 | 802.11 Technology Fundamentals |
Which four options are the characteristics of the original 802.11 protocol?
| 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 the2.4 GHz ISM frequency spectrum | |
| H. |
The protocol sets the maximum throughput at1 Mb/s |
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 center frequency is 2.412, this channel spans from 2.401 GHz to 2.423 GHz) and does not move (no hopping, which is why the sequence is said to be direct instead of hopping). Then, over this 22 MHz channel, several bits of information are sent in parallel. If a source of interference affects part of the channel, it will prevent only the bits sent in that frequency from reaching the receiver.