CWDP-305 Exam Dumps - Certified Wireless Design Professional

When APs are deployed in the same physical pattern across floors without channel and physical spacing considerations, co-channel interference (CCI) between floors occurs. This is particularly problematic when APs on different floors are vertically aligned on the same channels.

From CWDP-305:

“In multi-floor deployments, avoid placing APs on the same vertical axis across floors using the same channel. This leads to CCI. Stagger AP locations and vary channels to reduce interference.”

— Reference: CWDP-305 Official Study Guide, Wireless Design Process Chapter

An active site survey involves connecting a client device to the WLAN and measuring various performance metrics such as throughput, latency, and roaming behavior. This type of survey is essential for validating that roaming is functioning as intended, as it allows the surveyor to observe the client's ability to maintain a stable connection while moving between access points.

The Received Signal Strength Indicator (RSSI) is a measure of the power present in a received radio signal. While it is commonly used in WLAN location-based services due to its simplicity and the fact that it doesn't require additional hardware, RSSI-based positioning is susceptible to environmental factors like multipath propagation and signal attenuation, leading to lower accuracy.

In contrast:

Angle of Arrival (AoA) determines the direction of the incoming signal, offering better accuracy.

Time of Arrival (ToA) measures the time it takes for a signal to travel from the transmitter to the receiver, providing precise distance measurements.

Time Difference of Arrival (TDoA) calculates the difference in arrival times between multiple receivers, enhancing location accuracy.

When deploying a WLAN that includes both WMM-PS (Wi-Fi Multimedia Power Save) certified devices and legacy devices that do not support WMM, it's important to understand the implications on performance and battery life.

WMM-PS, based on Unscheduled Automatic Power Save Delivery (U-APSD), allows client devices to conserve battery power by managing the time the device spends in sleep mode and reducing the need for frequent wake-ups.This mechanism is particularly beneficial for applications like VoIP, where timely delivery of packets is crucial.

However, legacy devices that do not support WMM-PS rely on older power-saving mechanisms, such as PS-Poll, which are less efficient.When both WMM-PS and non-WMM-PS devices operate on the same WLAN, the differences in power-saving capabilities can lead to inconsistencies in performance and battery life.Specifically, WMM-PS devices may experience better battery conservation and performance, while non-WMM-PS devices may have reduced efficiency.

This scenario is addressed in the CWDP-305 Official Study and Reference Guide, which emphasizes the importance of understanding client capabilities and their impact on WLAN performance.

When designing a wireless bridge over a distance of 13 kilometers, it's crucial to account for the Earth's curvature, known as the "Earth bulge," which can obstruct the Fresnel Zone and degrade the signal.The Fresnel Zone is an elliptical area around the line of sight between two antennas, and any obstruction within this zone can cause signal diffraction and attenuation.

The CWDP-305 Official Study and Reference Guide highlights this consideration:

"For long-distance point-to-point links, the Earth’s curvature becomes a factor, and the Fresnel Zone must be clear of obstructions, including the Earth bulge, to maintain signal integrity."

Therefore, when planning such links, engineers must calculate the Fresnel Zone and ensure that the Earth bulge does not intrude into this zone, possibly requiring higher antenna placements or alternative solutions.

Comprehensive and Detailed Explanation:

Latency is a critical metric when designing WLANs for VoIP (Voice over IP) applications. High latency can result in poor call quality, including delays and echoes. Industry standards recommend that one-way latency should not exceed 150 milliseconds to maintain acceptable voice quality. Therefore, during site surveys and network design, measuring and minimizing latency is essential to ensure a high-quality VoIP experience.

A passive survey is the most appropriate survey type when diagnosing coverage and signal strength issues. It listens to beacons and probe responses to map the RF environment, showing actual signal levels, noise levels, and AP visibility across the site. Passive surveys are particularly valuable for understanding how clients "see" the network when associating.

From CWDP-305:

“Passive surveys are used to validate RF coverage and detect interference. They listen to beacon and other management frames to determine AP coverage areas without needing to associate to a specific AP.”

Active surveys require client association and are more suited for performance-related assessments (like throughput and latency), while predictive surveys are used for pre-deployment modeling.

— Reference: CWDP-305 Official Study and Reference Guide, Chapter on Post-Design ValidationandTroubleshooting