CCNP Wireless FAQ: Wireless Fundamentals
Q1. How does the wavelength of a wireless signal change as the frequency of the signal increases?
Answer: As the frequency of a wireless signal increases, the wavelength of the signal becomes shorter.
Q2. When a 2.4-GHz signal encounters an obstruction, what happens?
Answer: When a 2.4-GHz signal encounters an obstruction, some of the signal is attenuated, some of the signal is reflected, and some of the signal diffracts around the obstruction.
Q3. Does ionospheric reflection occur at microwave frequencies?
Figure: Microwave Signal Reflection
Answer: Ionospheric reflection generally does not occur at microwave frequencies.
Q4. How is wireless power measured?
Answer: Wireless power is measured using decibel (dB) ratios compared to a recognized reference level, typically 1 mW (dBm).
Q5. In the abbreviation dBm, what does the “m” stand for?
Answer: In dBm, the “m” stands for 1 milliwatt, or one-thousandth of one watt.
Q6. If 1Watt equals +30 dBm, then 2W equals how many dBm?
Answer: 2W equals +33 dBm.
Q7. The main lobe of a non-isotropic antenna radiates power in which direction?
A. In one horizontal direction
B. In two horizontal directions
C. Equally in all horizontal directions
D. Both A and C
Answer: D. The main lobe of a directional antenna radiates power in only one horizontal direction. The main lobe of an omnidirectional antenna radiates power in all horizontal directions.
Q8. If you can stand at one antenna and see the antenna at the other end of a wireless link, do you have a line-of-sight wireless path?
Answer: If you can see the other antennaandif you have a clear Fresnel zone, you have a line-of-sight wireless path. If you can see the other antenna but more than 60 percent of the Fresnel zone is obstructed, you do nothave a clear wireless line-of-sight path, even though you might have an unobstructed opticalLOSpath. The obstructed Fresnel zone adds additional attenuation and the wireless performance is reduced.
Q9. Tripling the distance on an unobstructed wireless link requires increasing the power how many times?
Answer: Tripling the distance on an unobstructed wireless link requires a power increase of three squared, or nine times, assumingLOSpaths.