CWS CWS WLAN Hardware and Antennas 3 — Questions and Answers
Question 1: What is the primary purpose of a PoE (Power over Ethernet) injector in a WLAN deployment?
- To boost Wi-Fi signal strength
- To deliver electrical power to an AP over the Ethernet cable (Correct answer)
- To convert fiber optic signal to Ethernet
- To provide VLAN tagging for wireless traffic
Correct answer: To deliver electrical power to an AP over the Ethernet cable
A PoE injector adds DC power onto an Ethernet cable, allowing an access point to receive both data and power through a single cable.
Question 2: A sector antenna with a 120-degree horizontal beamwidth is typically used in which deployment scenario?
- Indoor office coverage
- Point-to-point building bridges
- Outdoor cellular-style coverage with multiple sectors (Correct answer)
- Desktop client adapters
Correct answer: Outdoor cellular-style coverage with multiple sectors
Sector antennas with 120-degree beamwidth are deployed in groups of three (or more) to provide 360-degree outdoor coverage from a central tower or rooftop.
Question 3: What is antenna downtilt used for in outdoor WLAN deployments?
- To increase gain in the horizontal plane
- To direct energy toward users below the antenna rather than toward the horizon (Correct answer)
- To reduce the operating frequency
- To switch between 2.4 GHz and 5 GHz bands
Correct answer: To direct energy toward users below the antenna rather than toward the horizon
Antenna downtilt angles the radiation pattern downward to focus coverage on users in the intended service area and reduce interference with distant systems.
Question 4: Which IEEE 802.11 standard introduced MU-MIMO technology to allow simultaneous transmission to multiple clients?
- 802.11n
- 802.11ac Wave 1
- 802.11ac Wave 2 (Correct answer)
- 802.11g
Correct answer: 802.11ac Wave 2
802.11ac Wave 2 introduced Multi-User MIMO (MU-MIMO), allowing access points to transmit to multiple clients simultaneously using spatial streams.
Question 5: What is the function of a WLAN controller in an enterprise network?
- To amplify Wi-Fi signals between access points
- To centrally manage, configure, and monitor multiple access points (Correct answer)
- To convert 2.4 GHz signals to 5 GHz
- To provide DHCP services exclusively for wireless clients
Correct answer: To centrally manage, configure, and monitor multiple access points
A WLAN controller provides centralized management of access points, handling configuration, roaming, security policies, and performance optimization.
Question 6: What does the term 'antenna diversity' refer to in WLAN systems?
- Using antennas of different frequencies simultaneously
- Employing multiple antennas and selecting the best signal to reduce multipath fading (Correct answer)
- Installing antennas at different heights
- Supporting multiple Wi-Fi standards on one antenna
Correct answer: Employing multiple antennas and selecting the best signal to reduce multipath fading
Antenna diversity uses two or more antennas and dynamically selects or combines the one(s) receiving the strongest signal to combat multipath fading.
Question 7: What is the maximum output power allowed by the FCC for 2.4 GHz Wi-Fi devices in the United States?
- 10 mW (10 dBm)
- 100 mW (20 dBm) (Correct answer)
- 1000 mW (30 dBm)
- 10 W (40 dBm)
Correct answer: 100 mW (20 dBm)
The FCC limits 2.4 GHz ISM band intentional radiators to 1 Watt (30 dBm) conducted power, but with antenna gain limits the EIRP cap results in effective limits typically around 100 mW for point-to-multipoint.
CWS CWS WLAN Hardware and Antennas 3
What is the primary purpose of a PoE (Power over Ethernet) injector in a WLAN deployment?