CWT Wireless Standards & Radio Frequency Fundamentals 5

Question 1

What is the key difference between 2.4 GHz and 5 GHz Wi-Fi in terms of propagation?

Accepted Answer

2.4 GHz has longer range but is more prone to interference from overlapping channels

Answer

The 2.4 GHz band provides longer range and better wall penetration but suffers from heavy interference due to only 3 non-overlapping channels and many competing devices.

Question 2

In OFDM, what is the role of subcarriers?

Accepted Answer

They carry independent data streams in parallel across narrow sub-channels within a wide channel

Answer

OFDM divides a wide channel into many narrow orthogonal subcarriers that carry data in parallel, improving spectral efficiency and robustness against multipath interference.

Question 3

What is the Hidden Node Problem in Wi-Fi, and which mechanism was designed to address it?

Accepted Answer

Two clients can hear the AP but not each other, causing collisions; addressed by RTS/CTS

Answer

The hidden node problem occurs when two clients cannot hear each other but both transmit to the AP simultaneously; RTS/CTS (Request to Send / Clear to Send) exchanges reserve the medium to prevent collisions.

Question 4

Which 802.11 amendment introduced support for operation in the TV White Space (TVWS) spectrum below 1 GHz?

Accepted Answer

802.11af

Answer

IEEE 802.11af (also called White-Fi or Super Wi-Fi) operates in unused TV broadcast channels (54–790 MHz), offering extended range due to favorable propagation at lower frequencies.

Question 5

What is the significance of the Fresnel zone in wireless link design?

Accepted Answer

It is an elliptical region around the line-of-sight path that must be kept mostly clear of obstructions to avoid signal loss

Answer

The Fresnel zone is a series of ellipsoidal regions around the LOS path; obstructions within the first Fresnel zone cause significant diffraction loss, so at least 60% clearance is recommended.

(CWT) Certified Wireless Technician Practice Test

(CWT) Certified Wireless Technician Practice Test

CWT Wireless Standards & Radio Frequency Fundamentals 5