ACMA Wireless Fundamentals 2 — Questions and Answers
Question 1: Which IEEE 802.11 amendment introduced OFDMA as a key feature for improved multi-user efficiency?
- 802.11n
- 802.11ac
- 802.11ax (Correct answer)
- 802.11g
Correct answer: 802.11ax
802.11ax (Wi-Fi 6) introduced OFDMA, which divides channels into resource units to serve multiple clients simultaneously.
Question 2: What is the primary purpose of a CSMA/CA mechanism in 802.11 wireless networks?
- To encrypt wireless frames
- To avoid collisions before transmitting (Correct answer)
- To assign IP addresses to clients
- To balance load across APs
Correct answer: To avoid collisions before transmitting
CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) listens for channel activity and uses random backoff timers to reduce collisions.
Question 3: Which wireless band typically provides greater range but lower throughput due to its lower frequency?
- 6 GHz
- 5 GHz
- 2.4 GHz (Correct answer)
- 60 GHz
Correct answer: 2.4 GHz
The 2.4 GHz band propagates farther through obstacles but offers fewer non-overlapping channels and lower maximum throughput than 5 GHz.
Question 4: What does EIRP stand for in the context of wireless networking?
- Effective Isotropic Radiated Power (Correct answer)
- Encoded Infrared Routing Protocol
- Extended Interference Reduction Profile
- Equivalent Internal Radio Propagation
Correct answer: Effective Isotropic Radiated Power
EIRP is the total radiated power combining transmit power and antenna gain, used by regulators to limit interference.
Question 5: In 802.11 networks, what is the function of the ACK (Acknowledgment) frame?
- To initiate the four-way handshake
- To confirm successful receipt of a unicast data frame (Correct answer)
- To advertise SSID to nearby clients
- To request a data rate change from the AP
Correct answer: To confirm successful receipt of a unicast data frame
The receiving station sends an ACK frame after successfully receiving a unicast frame to confirm delivery.
Question 6: Which modulation technique is used by 802.11b to achieve its highest data rate of 11 Mbps?
- OFDM
- CCK (Correct answer)
- BPSK
- QAM-64
Correct answer: CCK
802.11b uses Complementary Code Keying (CCK) to achieve 5.5 and 11 Mbps data rates.
Question 7: What term describes the phenomenon where a wireless signal bounces off walls, floors, and ceilings, causing multiple copies to arrive at the receiver at different times?
- Refraction
- Multipath (Correct answer)
- Attenuation
- Doppler shift
Correct answer: Multipath
Multipath propagation occurs when signals reflect off surfaces and arrive at the receiver via multiple paths, potentially causing interference.
ACMA Wireless Fundamentals 2
Which IEEE 802.11 amendment introduced OFDMA as a key feature for improved multi-user efficiency?