ACMA Wireless Networking Fundamentals & Technologies 2 — Questions and Answers
Question 1: Which 802.11 amendment introduced OFDMA as the primary multiple-access scheme for Wi-Fi?
- 802.11ac
- 802.11ax (Correct answer)
- 802.11n
- 802.11g
Correct answer: 802.11ax
802.11ax (Wi-Fi 6) introduced Orthogonal Frequency Division Multiple Access (OFDMA), enabling simultaneous transmission to multiple clients.
Question 2: What is the maximum number of spatial streams supported by 802.11ac Wave 2?
- 2
- 4
- 8 (Correct answer)
- 16
Correct answer: 8
802.11ac Wave 2 supports up to 8 spatial streams using MU-MIMO, enabling higher aggregate throughput.
Question 3: In 802.11 terminology, what is the role of the Distribution System (DS)?
- It assigns IP addresses to wireless clients
- It interconnects access points within an ESS (Correct answer)
- It provides DHCP services to the BSS
- It encrypts data between the client and AP
Correct answer: It interconnects access points within an ESS
The Distribution System connects multiple APs together to form an Extended Service Set (ESS), enabling roaming between APs.
Question 4: What guard interval option did 802.11ax introduce that was NOT available in 802.11ac?
- 400 ns
- 800 ns
- 1600 ns
- 3200 ns (Correct answer)
Correct answer: 3200 ns
802.11ax introduced a 3200 ns guard interval to handle outdoor and high-multipath environments with longer delay spreads.
Question 5: Which band characteristic makes the 5 GHz frequency range generally preferable for high-throughput applications compared to 2.4 GHz?
- Better wall penetration
- More non-overlapping channels and less interference (Correct answer)
- Lower path loss over distance
- Wider compatibility with legacy devices
Correct answer: More non-overlapping channels and less interference
The 5 GHz band offers more non-overlapping channels and significantly less co-channel interference from other Wi-Fi and non-Wi-Fi devices.
Question 6: What does the term 'BSS Color' refer to in 802.11ax?
- A visual indicator in the management UI for RF band assignment
- A mechanism to differentiate overlapping BSSs and reduce unnecessary deferrals (Correct answer)
- A QoS marking field in the 802.11 frame header
- A color-coded channel plan displayed in Aruba Central
Correct answer: A mechanism to differentiate overlapping BSSs and reduce unnecessary deferrals
BSS Color is a field in 802.11ax beacons that identifies a specific BSS, allowing stations to ignore frames from other BSSs and reduce medium contention.
Question 7: Which of the following correctly describes a Hidden Node problem in wireless networks?
- A client that is outside the AP coverage area but still attempts to associate
- Two clients that can both hear the AP but cannot hear each other, causing collisions (Correct answer)
- An AP that is not broadcasting its SSID
- A rogue AP with a spoofed MAC address
Correct answer: Two clients that can both hear the AP but cannot hear each other, causing collisions
The hidden node problem occurs when two clients are both in range of an AP but out of range of each other, so their transmissions collide at the AP without either knowing.
ACMA Wireless Networking Fundamentals & Technologies 2
Which 802.11 amendment introduced OFDMA as the primary multiple-access scheme for Wi-Fi?