Wireless Network Administrator MCQ Flashcards

What is the center frequency of channel 40 in the U-NII-1 band?

Answer: 5.2 GHz

The U-NII-1 band for 5 GHz Wi-Fi operates from 5.150 GHz to 5.250 GHz. Within this band, channels are spaced 20 MHz apart. Channel 36 has a center frequency of 5.180 GHz, and channel 40 is the next channel up. Therefore, the center frequency for channel 40 is 5.180 GHz + 20 MHz = 5.200 GHz, or 5.2 GHz.

What are a few of layer two retransmissions' drawbacks?

Answer: Excessive MAC sublayer overhead

Layer two retransmissions, common in wireless networks like Wi-Fi, occur when data frames are not successfully received and acknowledged. While necessary for reliability, frequent retransmissions consume valuable airtime and processing power at the MAC sublayer. This leads to excessive overhead, reducing the network's overall efficiency and effective throughput, as more time is spent re-sending data rather than transmitting new information.

Which of the subsequent statements is accurate?

Answer: When a downgrade occurs, the final received signal will never be stronger than the originally transmitted signal.

Signal 'downgrade' or 'fade' refers to the attenuation or weakening of a signal as it travels through a medium. Due to factors like absorption, reflection, and scattering, the received signal will always be weaker than the signal originally transmitted from the source. Therefore, a downgrade inherently means the final received signal cannot be stronger than the initial transmission.

What is a PD Class 0 device's maximum power consumption?

Answer: 12.95 W

According to the IEEE 802.3af Power over Ethernet (PoE) standard, a Powered Device (PD) classified as Class 0 is designed to draw a maximum power of 12.95 watts. This classification helps Power Sourcing Equipment (PSE) manage and allocate power efficiently to connected devices on the network.

Which of these cryptographic techniques has been broken?

Answer: 64-bit WEP

Wired Equivalent Privacy (WEP), particularly its 64-bit and 128-bit versions, is a deprecated and highly insecure encryption protocol for Wi-Fi. It has been widely broken due to fundamental cryptographic flaws, such as a weak initialization vector (IV) and vulnerabilities in its RC4 stream cipher implementation. These weaknesses allow attackers to easily recover the WEP key, rendering it ineffective for securing wireless communications.

What is the name of the ratio between the minimum voltage and maximum peak voltage on a line?

Answer: VSWR

VSWR, or Voltage Standing Wave Ratio, is a critical measurement in radio frequency engineering. It quantifies the efficiency of power transmission from a source through a transmission line to a load by measuring the ratio of the maximum to minimum voltage (or current) in a standing wave pattern. A high VSWR indicates a significant impedance mismatch, leading to power reflection and loss.

What company is responsible for WLAN product interoperability?

Answer: Wi-Fi Alliance

While the IEEE (Institute of Electrical and Electronics Engineers) develops the 802.11 standards for wireless LANs, the Wi-Fi Alliance is the global industry association responsible for ensuring product interoperability. They conduct rigorous testing and provide 'Wi-Fi Certified' labels to products that meet their standards, guaranteeing that devices from different manufacturers can seamlessly connect and work together.