CWS CWS WLAN Hardware and Antennas 4 — Questions and Answers
Question 1: A Yagi antenna is best described as which type of antenna?
- Omni-directional with high vertical gain
- Highly directional with multiple elements along a boom (Correct answer)
- Flat panel for wall mounting
- Collinear array for ceiling deployment
Correct answer: Highly directional with multiple elements along a boom
A Yagi antenna uses a driven element, reflector, and multiple director elements along a boom to achieve high gain in a single forward direction.
Question 2: What is co-channel interference (CCI) in a WLAN deployment?
- Interference caused by two different frequency bands overlapping
- Interference between access points using the same channel (Correct answer)
- Interference from non-Wi-Fi devices like microwaves
- Signal degradation caused by multipath reflections
Correct answer: Interference between access points using the same channel
Co-channel interference occurs when two or more access points operate on the same channel within range of each other, competing for airtime.
Question 3: Which cable type is preferred for connecting outdoor antennas to access points over long cable runs to minimize signal loss?
- RG-58
- Cat6 Ethernet
- Low-loss coaxial cable (e.g., LMR-400) (Correct answer)
- RG-174
Correct answer: Low-loss coaxial cable (e.g., LMR-400)
Low-loss coaxial cables like LMR-400 have significantly lower attenuation per foot than standard cables, preserving signal strength over long outdoor runs.
Question 4: What is a patch antenna primarily used for in WLAN deployments?
- Providing 360-degree indoor coverage
- Directional coverage in a specific area like a hallway or outdoor sector (Correct answer)
- Connecting two buildings over several miles
- Receiving satellite signals for GPS timing
Correct answer: Directional coverage in a specific area like a hallway or outdoor sector
Patch antennas provide directional coverage with moderate gain, commonly used for hallways, outdoor coverage sectors, and focused indoor zones.
Question 5: What is the significance of the Fresnel zone in outdoor wireless link planning?
- It defines the maximum transmit power allowed by the FCC
- It is the elliptical area around the line of sight that must be at least 60% clear for optimal signal (Correct answer)
- It determines the antenna height required by building codes
- It specifies the cable length limit for PoE installations
Correct answer: It is the elliptical area around the line of sight that must be at least 60% clear for optimal signal
The first Fresnel zone is an elliptical volume around the direct path between antennas; obstructing more than 40% of it significantly degrades link performance.
Question 6: What does MIMO stand for in the context of 802.11n and later Wi-Fi standards?
- Minimum Input Maximum Output
- Multiple Input Multiple Output (Correct answer)
- Modulated Interface Mixed Operation
- Managed Infrastructure Mobile Optimization
Correct answer: Multiple Input Multiple Output
MIMO (Multiple Input Multiple Output) uses multiple antennas at both the transmitter and receiver to improve throughput and reliability through spatial multiplexing.
Question 7: An enterprise access point is described as 3x3:3 MIMO. What does this notation mean?
- 3 GHz frequency, 3 channels, 3 dBi gain
- 3 transmit antennas, 3 receive antennas, 3 spatial streams (Correct answer)
- 3 clients, 3 VLANs, 3 SSIDs supported
- Third generation, revision 3, with 3 dBm output
Correct answer: 3 transmit antennas, 3 receive antennas, 3 spatial streams
The notation TxR:S indicates transmit chains x receive chains: spatial streams, so 3x3:3 means 3 transmit, 3 receive antennas supporting 3 simultaneous spatial streams.
CWS CWS WLAN Hardware and Antennas 4
A Yagi antenna is best described as which type of antenna?