CWNP CWNA-109 Dumps Questions Answers

Impedance is the measure of opposition to the flow of alternating current (AC) in a circuit. Impedance mismatch occurs when the impedance of the radio does not match the impedance of the antenna or the cable. This causes some of the transmitted or received signal to be reflected back, resulting in a loss of power and efficiency. The voltage standing wave ratio (VSWR) is a metric that indicates the amount of impedance mismatch in a transmission line. A higher VSWR means a higher impedance mismatch and a lower signal quality. A VSWR of 1:1 is ideal, meaning there is no impedance mismatch and no reflected power. A VSWR of 2:1 means that for every 2 units of forward power, there is 1 unit of reflected power12.

The other options are not correct because they do not affect the VSWR in RF cables. A high gain yagi antenna or a high gain parabolic dish antenna can increase the signal strength and directionality, but they do not cause impedance mismatch in the cable. Radio output power above 100 mW but below 400 mW is within the acceptable range for most WLAN devices and does not cause excessive VSWR in the cable3.

References: 1:CWNA-109Official Study Guide, page 77 2: VSWR 3:CWNA-109Official Study Guide, page 81

An immediate concern that you note after hearing this information is that the power budget in the edge switches must be carefully planned and monitored based on the number of supported PoE devices. PoE stands for Power over Ethernet and is a technology that allows Ethernet switches to deliver power along with data to devices such as VoIP phones and 802.11 access points. PoE devices are classified into different classes based on their power consumption and output. The edge switches have a limited power budget that determines how many PoE devices they can support simultaneously. If the power budget is exceeded, some PoE devices may not receive enough power or may shut down unexpectedly. Therefore,it is important to plan and monitor the power budget in the edge switches based on the number and class of PoE devices connected to them. Using Ether-channel, placing switches in optimal locations, or avoiding distortion are not immediate concerns related to PoE devices. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 234; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 224.

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.

References:

• CWNA Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109, by David D. Coleman and David A. Westcott.
• Best practices for conducting pre-design site visits in wireless network planning.