ACMA Wireless Fundamentals 4 — Questions and Answers
Question 1: What does RSSI measure in a wireless network?
- The data throughput of a wireless client
- The relative strength of a received wireless signal (Correct answer)
- The number of retransmissions on a channel
- The encryption strength of a WPA2 connection
Correct answer: The relative strength of a received wireless signal
RSSI (Received Signal Strength Indicator) is a relative measurement of the power level of a received wireless signal.
Question 2: Which technology allows multiple antennas to transmit and receive simultaneously in 802.11n and later, improving throughput?
- MU-MIMO
- OFDMA
- MIMO (Correct answer)
- Beamforming
Correct answer: MIMO
MIMO (Multiple Input Multiple Output) uses multiple antennas to send and receive multiple data streams simultaneously, increasing throughput.
Question 3: What is the purpose of a Beacon frame in 802.11 wireless networks?
- To request association with an AP
- To periodically advertise the BSS and its capabilities (Correct answer)
- To probe for available APs in range
- To confirm a client's IP address assignment
Correct answer: To periodically advertise the BSS and its capabilities
Beacon frames are periodically broadcast by APs to advertise the SSID, supported rates, and other BSS parameters.
Question 4: What SNR (Signal-to-Noise Ratio) value in dB is generally considered the minimum for reliable VoIP over Wi-Fi?
- 5 dB
- 10 dB
- 25 dB (Correct answer)
- 40 dB
Correct answer: 25 dB
An SNR of at least 25 dB is generally recommended for reliable VoIP traffic over Wi-Fi to ensure acceptable call quality.
Question 5: Which channel bonding technique doubles the channel width from 20 MHz to 40 MHz in the 5 GHz band?
- Spatial multiplexing
- Channel aggregation
- Channel bonding (Correct answer)
- Guard interval reduction
Correct answer: Channel bonding
Channel bonding combines two adjacent 20 MHz channels into a 40 MHz channel, nearly doubling maximum throughput.
Question 6: What is the free-space path loss characteristic — as the distance between transmitter and receiver doubles, signal strength decreases by approximately how much?
- 3 dB
- 6 dB (Correct answer)
- 10 dB
- 20 dB
Correct answer: 6 dB
In free space, doubling the distance results in approximately 6 dB of additional path loss, following the inverse square law.
Question 7: In the context of 802.11 security, what does the 4-way handshake accomplish?
- It verifies the AP's SSID and BSSID before association
- It derives and confirms the Pairwise Transient Key (PTK) for unicast encryption (Correct answer)
- It exchanges certificates between client and RADIUS server
- It negotiates the modulation and coding scheme for the session
Correct answer: It derives and confirms the Pairwise Transient Key (PTK) for unicast encryption
The 4-way handshake confirms that both client and AP possess the correct PMK and derives the PTK used for unicast data encryption.
ACMA Wireless Fundamentals 4
What does RSSI measure in a wireless network?