CWDP CWDP Outdoor and Mesh Networking 2 — Questions and Answers
Question 1: What is the purpose of Dynamic Frequency Selection (DFS) in 5 GHz outdoor WLAN deployments?
- To automatically select the least-congested channel for maximum throughput
- To detect radar signals and vacate channels to prevent interference with safety systems (Correct answer)
- To dynamically adjust transmit power based on client distance
- To enable channel bonding for higher bandwidth
Correct answer: To detect radar signals and vacate channels to prevent interference with safety systems
DFS monitors for radar transmissions and moves WLAN equipment off channels to prevent interference with radar systems.
Question 2: A designer is planning a campus outdoor WLAN using 802.11ac APs. Which channel width provides the best balance of throughput and interference avoidance in an outdoor environment?
- 160 MHz channels
- 80 MHz channels
- 40 MHz channels (Correct answer)
- 20 MHz channels
Correct answer: 40 MHz channels
40 MHz channels in 5 GHz outdoor deployments balance throughput with sufficient spectrum availability and reduced co-channel interference risk.
Question 3: What factor most significantly increases free-space path loss between two outdoor wireless nodes?
- Antenna polarization mismatch
- Doubling the operating frequency or distance (Correct answer)
- Cable losses in the transmission line
- Ambient temperature above 90°F
Correct answer: Doubling the operating frequency or distance
Free-space path loss increases by 6 dB when distance or frequency doubles, as defined by the Friis transmission equation.
Question 4: When designing an outdoor mesh for a smart city deployment, which protocol is used by mesh nodes to discover routes and forward traffic efficiently?
- STP (Spanning Tree Protocol)
- Hybrid Wireless Mesh Protocol (HWMP) defined in IEEE 802.11s (Correct answer)
- OSPF over wireless links
- ARP flooding between mesh nodes
Correct answer: Hybrid Wireless Mesh Protocol (HWMP) defined in IEEE 802.11s
IEEE 802.11s defines HWMP as the default path selection protocol for Wi-Fi mesh networks.
Question 5: What is the recommended minimum link margin (fade margin) for a reliable outdoor point-to-point WLAN bridge link?
- 2–5 dB
- 5–10 dB
- 15–20 dB (Correct answer)
- 30–40 dB
Correct answer: 15–20 dB
A fade margin of 15–20 dB accounts for atmospheric fading, rain fade, and multipath variations to ensure reliable link availability.
Question 6: Which environmental factor causes the most significant signal attenuation for outdoor 5 GHz links during adverse weather?
- Direct sunlight on antennas
- Heavy rain causing rain fade above 10 GHz
- Wind causing antenna misalignment (Correct answer)
- High humidity at ground level
Correct answer: Wind causing antenna misalignment
Wind-induced antenna sway causes misalignment of high-gain directional antennas, significantly degrading narrow-beam outdoor links.
CWDP CWDP Outdoor and Mesh Networking 2
What is the purpose of Dynamic Frequency Selection (DFS) in 5 GHz outdoor WLAN deployments?