CWDP Channel Planning and RF Design 3

Question 1

What is the '20/40 MHz coexistence' mechanism defined in 802.11n for the 2.4 GHz band?

Accepted Answer

A protection mechanism that restricts 40 MHz operation when legacy or neighboring APs are detected on adjacent channels

Answer

20/40 MHz coexistence prevents 40 MHz operation in 2.4 GHz when overlapping BSS or legacy devices are present, protecting existing networks from harmful interference.

Question 2

What does EIRP stand for, and why is it significant in RF channel design?

Accepted Answer

Effective Isotropic Radiated Power — it represents the total RF power output in a specific direction combining transmit power and antenna gain

Answer

EIRP (Effective Isotropic Radiated Power) is the product of transmit power and antenna gain, and it is the regulatory-controlled quantity that cannot exceed FCC limits for a given channel and band.

Question 3

In channel planning, what does 'channel reuse distance' refer to?

Accepted Answer

The minimum physical separation required between APs using the same channel to prevent co-channel interference

Answer

Channel reuse distance is the minimum separation between co-channel APs that ensures their signals are attenuated enough to avoid significant interference at each other's coverage areas.

Question 4

Which US regulatory body governs maximum transmit power levels and permitted channels for WLAN deployments?

Accepted Answer

FCC (Federal Communications Commission)

Answer

The FCC sets the legal limits for transmit power, antenna gain, and permitted channels for unlicensed spectrum used by WLAN in the United States.

Question 5

What is the primary channel planning risk when deploying 80 MHz channels in an 802.11ac/Wi-Fi 5 environment?

Accepted Answer

The number of non-overlapping channels drops significantly, greatly increasing co-channel interference risk

Answer

80 MHz channels consume four times the spectrum of 20 MHz channels, leaving very few non-overlapping options in the 5 GHz band and making co-channel interference nearly unavoidable in dense deployments.

Certified Wireless Design Professional (CWDP) Practice Test

Certified Wireless Design Professional (CWDP) Practice Test

CWDP Channel Planning and RF Design 3