CWT Wireless Standards & Radio Frequency Fundamentals 4 — Questions and Answers
Question 1: The 6 GHz band introduced with Wi-Fi 6E provides approximately how much additional spectrum in the US?
- 500 MHz
- 1.2 GHz (Correct answer)
- 1.2 GHz
- 2.4 GHz
Correct answer: 1.2 GHz
The FCC opened 1,200 MHz of spectrum in the 6 GHz band (5.925–7.125 GHz) for unlicensed Wi-Fi 6E use in the United States.
Question 2: What does RSSI measure in a Wi-Fi network?
- The data rate negotiated between AP and client
- The relative received signal strength at a wireless device (Correct answer)
- The channel utilization percentage
- The noise floor in dBm
Correct answer: The relative received signal strength at a wireless device
RSSI (Received Signal Strength Indicator) is a relative measure of the power level of a received radio signal, typically expressed as a negative dBm value.
Question 3: Which technology allows a single AP to serve multiple clients simultaneously by directing beams to individual users?
- SISO
- OFDM
- MU-MIMO (Correct answer)
- DSSS
Correct answer: MU-MIMO
Multi-User MIMO (MU-MIMO) enables an AP to use multiple antennas to transmit to several clients at the same time, increasing overall throughput.
Question 4: What is the primary advantage of using a directional antenna over an omnidirectional antenna in a point-to-point wireless link?
- Lower cost
- Increased gain and focused signal toward the remote end (Correct answer)
- Broader coverage area
- Simpler installation
Correct answer: Increased gain and focused signal toward the remote end
Directional antennas concentrate RF energy in a specific direction, providing higher gain and longer link distances compared to omnidirectional antennas.
Question 5: What is the Friis transmission equation used to calculate?
- The noise figure of a receiver
- The received signal power given transmit power, antenna gains, and distance (Correct answer)
- The channel capacity of a wireless link
- The bit error rate at a given SNR
Correct answer: The received signal power given transmit power, antenna gains, and distance
The Friis transmission equation calculates the power received by an antenna given the transmitted power, antenna gains, wavelength, and separation distance.
Question 6: Which 802.11 feature uses the physical carrier sense mechanism and a network allocation vector (NAV) to avoid collisions?
- CSMA/CD
- CSMA/CA (Correct answer)
- TDMA
- FDMA
Correct answer: CSMA/CA
CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) uses both physical sensing and a virtual NAV timer to reduce the probability of collisions in wireless networks.
Question 7: What does 'noise floor' refer to in RF engineering?
- The minimum transmit power of an access point
- The cumulative level of unwanted background RF energy in a given frequency band (Correct answer)
- The maximum interference level permitted by the FCC
- The lowest supported data rate of a radio
Correct answer: The cumulative level of unwanted background RF energy in a given frequency band
The noise floor is the aggregate level of thermal and environmental RF noise present in a spectrum band, and a signal must rise above it by a sufficient SNR margin to be decoded.
CWT Wireless Standards & Radio Frequency Fundamentals 4
The 6 GHz band introduced with Wi-Fi 6E provides approximately how much additional spectrum in the US?