Wireless Communication

In free space transmission, the signal attenuation increases

• proportionally with distance

• proportionally with the square distance

• proportionally with distance cube

When transmitting over a perfectly reflecting, smooth, plane earth , the path loss

tends to increase

• linearly with distance

• with the square of distance

• with distance cube

• with the fourth power of distance

Consider a cellular operator, who must select an appropriate frequency reuse

distance. If radio propagation attenuation increases rapidly with distance,

his cellular systems will be

• relatively inefficient.

• relatively efficient

Consider propagation over a perfectly reflecting, smooth, plane earth .

Doubling the antenna height of a mobile receiver near the cell boundary

• does not change the received power

• leads to 3 dB power increase

• leads to 6 dB power increase

What is the most appropriate multipath model for micro-cellular transmission,

where a dominant line-of-sight plus many weak reflections are present?

• Rayleigh Fading

• Rician Fading

• Nakagami Fading

• Shadow fading

The Doppler spread depends on

• the fade margin

• the speed of the antenna

• the delay spread

If reflected waves arrive with uniformly distributed angles of arrival,

the Doppler spectrum ,

• is bell shaped

• is U-shaped

• has a raised cosine shape

• has a rectangular shape

The channel delay spread determines

• the number of taps needed in an adaptive equalizer

  (used to mitigate the effect of frequency dispersion)

• the loop bandwidth needed in the PLL tracking the received signal

  (used to to track time-dispersion)

Antenna diversity with two antennas spaced by 40 cm is used to

combat shadowing .

• This can improve performance substantially

• This does not significantly improve performance

Diversity , i.e., reception through multiple antennas, works better

• with antennas spaced about a wavelength

• with antennas spaced about one eighth of wavelength