ACMA Wireless Networking Fundamentals & Technologies 4

Question 1

In 802.11, what is the purpose of the DIFS (Distributed Interframe Space)?

Accepted Answer

It is the minimum time a station must sense the channel idle before starting a transmission

Answer

DIFS is the mandatory idle period a station must observe before attempting a data transmission using the Distributed Coordination Function (DCF).

Question 2

Which term describes the technique where an AP steers a dual-band client from 2.4 GHz to 5 GHz to improve network performance?

Accepted Answer

Band steering

Answer

Band steering encourages capable dual-band clients to connect on the less congested 5 GHz band by manipulating probe responses or association parameters.

Question 3

What does 'spatial multiplexing' enable in MIMO wireless systems?

Accepted Answer

Sending multiple independent data streams over the same channel at the same time

Answer

Spatial multiplexing transmits independent data streams simultaneously using multiple antennas, multiplying throughput without requiring additional spectrum.

Question 4

In the context of 802.11 power management, what is a TIM (Traffic Indication Map)?

Accepted Answer

A field in the beacon that indicates which sleeping stations have buffered frames waiting at the AP

Answer

The TIM is included in AP beacons and indicates which associated sleeping stations have unicast frames buffered at the AP waiting for retrieval.

Question 5

Which 802.11 feature allows an AP to direct RF energy toward a specific client to improve signal quality?

Accepted Answer

Explicit transmit beamforming

Answer

Explicit transmit beamforming uses channel sounding feedback from the client to steer antenna energy directionally, improving SNR at the intended receiver.

(ACMA) Aruba Certified Mobility Associate Practice Test

(ACMA) Aruba Certified Mobility Associate Practice Test

ACMA Wireless Networking Fundamentals & Technologies 4