CWNA General Information 5 — Questions and Answers
Question 1: In the 2.4 GHz band (IEEE 802.11), how many non-overlapping 20 MHz channels are available in the United States?
- 1
- 3 (Correct answer)
- 4
- 11
Correct answer: 3
Only channels 1, 6, and 11 are non-overlapping in the US 2.4 GHz band, making 3 non-overlapping channels available for co-channel interference avoidance.
Question 2: What is the primary function of the 802.11r amendment?
- Protecting management frames against spoofing
- Enabling fast BSS transition to reduce roaming latency (Correct answer)
- Defining quality of service for voice traffic
- Specifying mesh network operation
Correct answer: Enabling fast BSS transition to reduce roaming latency
802.11r (Fast BSS Transition) enables clients to pre-authenticate to neighboring APs, dramatically reducing the latency when roaming between APs.
Question 3: Which term describes the practice of a client station selecting the best AP based on RSSI when multiple APs share the same SSID?
- Load balancing
- Band steering
- Active scanning
- Roaming (Correct answer)
Correct answer: Roaming
Roaming is the process by which a client station disassociates from one AP and associates to another AP offering a better signal within the same ESS.
Question 4: What formula is used to calculate the decibel equivalent of a power ratio?
- dB = 10 × log10(P1/P2) (Correct answer)
- dB = 20 × log10(P1/P2)
- dB = 10 × ln(P1/P2)
- dB = P1/P2 × 100
Correct answer: dB = 10 × log10(P1/P2)
Power ratios are expressed in decibels using the formula dB = 10 × log10(P1/P2), where P1 and P2 are the two power values being compared.
Question 5: Which 802.11 management frame is sent by a client station to request access to a BSS after authentication?
- Probe Request
- Authentication Request
- Association Request (Correct answer)
- Reassociation Request
Correct answer: Association Request
An Association Request is sent by a client to an AP after the authentication process completes, requesting to join the BSS and share resources.
Question 6: What does 'guard interval' refer to in OFDM-based 802.11 transmissions?
- A time gap between OFDM symbols to prevent inter-symbol interference (Correct answer)
- The preamble added before each MPDU for synchronization
- The space between non-overlapping channels in the spectrum
- The minimum SIFS time between frames
Correct answer: A time gap between OFDM symbols to prevent inter-symbol interference
The guard interval is a brief period of silence inserted between OFDM symbols to allow multipath reflections to dissipate and prevent inter-symbol interference.
Question 7: Which regulatory domain body governs WLAN transmit power and channel usage rules in the United States?
- ITU-R
- ETSI
- FCC (Correct answer)
- ANACOM
Correct answer: FCC
The Federal Communications Commission (FCC) regulates the use of radio frequency spectrum in the US, including transmit power limits and channel allocations for WLANs.
CWNA General Information 5
In the 2.4 GHz band (IEEE 802.11), how many non-overlapping 20 MHz channels are available in the United States?