CWNA-109 Exam Dumps : Certified Wireless Network Administrator

A pre-design site visit in preparation for a predictive wireless LAN design is essential for gathering physical and environmental data about the site. The key tasks to be performed during such a visit include:

Evaluating Building Materials: Different materials (concrete, glass, wood, etc.) have varying effects on RF signal propagation. Understanding the materials present helps in accurately predicting how signals will behave within the environment.

Floor Plan Verification: Ensuring that the floor plan documents are an accurate representation of the actual building layout is crucial. Discrepancies between the floor plans and the physical layout can lead to inaccuracies in the predictive design.

The other options, while potentially valuable in other contexts, are not directly related to preparing for a predictive design:

Installing APs (option A) for testing co-channel interference is more aligned with an active site survey rather than a pre-design visit for a predictive design.

Collecting information about security requirements (option B) is important but is not directly related to the physical aspects of the site that would impact a predictive design.

Testing antenna types (option C) would typically be part of an active site survey or the actual deployment phase, not a pre-design visit for predictive modeling.

Therefore, option D is the correct answer, focusing on evaluating physical aspects crucial for accurate predictive modeling.

The CWNA Official Study Guide (CWNA-109), Chapter 8: Troubleshooting and Spectrum Analysis, explains that hidden node problems occur when two or more client stations cannot hear each other but can both communicate with the same access point. This leads to collisions at the AP because the clients transmit simultaneously without sensing each other’s signals.

“Hidden node problems can often be identified in a protocol analyzer by observing excessive retransmissions from specific client stations. These retransmissions occur because the station’s frames are not acknowledged due to collisions caused by other stations that the transmitter cannot hear.”

— CWNA-108 Study Guide, Chapter 8, Hidden Node Problem Analysis, p. 393–395

Therefore, when analyzing for a hidden node issue, you will typically observe:

Retransmitted frames from multiple STAs.

Higher retry counts for affected stations compared to others.

Hence, the correct answer is C. Retransmitted frames from multiple STAs with higher retry counts than other STAs.