Question 2
In what frequency band does 802.11n operate in?
A. 5.0Ghz
B. 2.4Ghz
C. 3.7Ghz
D. 2.4Ghz and 5.0Ghz
Answer: D
Explanation
802.11n operates in the 2.4-GHz and 5-GHz bandwidths and is backward-compatible with 802.11a and 802.11b/g.
Question 3
Which three elements define the 802.11n implementation of MIMO? (Choose three)
A. Channel Bonding
B. Dynamic Frequency Selection
C. Maximal Ratio Combining
D. Packet Aggregation
E. Spatial Multiplexing
F. Transmit Beam Forming
Answer: C E F
Explanation
Multiple-Input Multiple-Output (MIMO) is a technology that is used in the new 802.11n specification. A device that uses MIMO technology uses multiple antennas to receive signals (usually two or three) as well as multiple antennas to send signals. Three elements that are implemented in MIMO are:
+ Maximal Ratio Combining (MRC): used by the receiver with multiple antennas to optimally combine energies from multiple receive chains. An algorithm eliminates out-of-phase signal degradation.
In this example, the radio receiver uses 3 antennae to take advantage of the multiple signals that each carry an identical copy of the data, by combining the received signals and performing algorithms that increase the sensitivity to the received signal.