ACMA Wireless Fundamentals 3 — Questions and Answers
Question 1: How many non-overlapping 20 MHz channels are available in the 2.4 GHz band in the United States?
- 2
- 3 (Correct answer)
- 4
- 11
Correct answer: 3
In the US, only channels 1, 6, and 11 are non-overlapping 20 MHz channels in the 2.4 GHz band.
Question 2: Which regulatory body governs the unlicensed use of wireless frequencies in the United States?
- IEEE
- Wi-Fi Alliance
- FCC (Correct answer)
- IETF
Correct answer: FCC
The Federal Communications Commission (FCC) regulates unlicensed spectrum use in the US, including the 2.4, 5, and 6 GHz bands.
Question 3: What is the primary role of the Distribution System (DS) in an 802.11 BSS architecture?
- To provide DHCP addresses to clients
- To connect multiple APs and allow inter-BSS communication (Correct answer)
- To encrypt traffic between AP and client
- To detect rogue access points
Correct answer: To connect multiple APs and allow inter-BSS communication
The Distribution System interconnects BSSs within an ESS, typically implemented as a wired Ethernet backbone.
Question 4: What type of antenna radiates power equally in all directions in the horizontal plane, like a donut shape?
- Yagi antenna
- Parabolic dish antenna
- Patch antenna
- Omnidirectional antenna (Correct answer)
Correct answer: Omnidirectional antenna
An omnidirectional antenna radiates power in a 360-degree pattern horizontally, making it ideal for providing coverage in all directions.
Question 5: Which 802.11 frame type is responsible for carrying user data across the wireless medium?
- Management frame
- Control frame
- Data frame (Correct answer)
- Action frame
Correct answer: Data frame
Data frames carry the actual payload (user data) between stations in an 802.11 network.
Question 6: What is the maximum transmit power typically allowed for 802.11 devices operating in the US 2.4 GHz band (EIRP)?
- 100 mW
- 200 mW
- 1000 mW (Correct answer)
- 30 dBm
Correct answer: 1000 mW
The FCC allows up to 1000 mW (1 watt or 30 dBm) EIRP for 802.11 devices in the 2.4 GHz band.
Question 7: In Aruba architecture, what is the role of the Mobility Controller (MC) in a controller-based WLAN?
- It serves as the RADIUS server for 802.1X authentication
- It centrally manages APs and processes forwarded wireless traffic (Correct answer)
- It acts as the default gateway for wireless clients
- It only handles rogue AP detection and containment
Correct answer: It centrally manages APs and processes forwarded wireless traffic
The Aruba Mobility Controller centrally manages APs (in tunnel mode) and can forward, secure, and apply policies to wireless traffic.
ACMA Wireless Fundamentals 3
How many non-overlapping 20 MHz channels are available in the 2.4 GHz band in the United States?