CWNP CWDP-305 - Certified Wireless Design Professional

The initiation of a project requires a formal document that authorizes its commencement and outlines its objectives, scope, stakeholders, and overall framework. This document is known as theProject Charter.

As detailed in the CWDP-305 Official Study and Reference Guide, the Project Charter serves several critical functions:

Authorization: It formally authorizes the existence of the project and provides the project manager with the authority to apply organizational resources to project activities.

High-Level Overview: The charter outlines the project's purpose, objectives, and high-level requirements, offering a clear understanding of what the project aims to achieve.

Stakeholder Identification: It identifies key stakeholders and their roles, ensuring that everyone involved understands their responsibilities and the project's governance structure.

Other documents listed, such as the Budget, Bill of Materials, and Work Breakdown Structure, are essential components developed during the planning phase but are not the initiating document.

Laptops are more likely to support advanced wireless features such as 3x3:3 Multiple Input Multiple Output (MIMO) configurations and 256 Quadrature Amplitude Modulation (QAM), which are integral to achieving the higher data rates offered by 802.11ac. These devices typically have the physical space and power resources to accommodate multiple antennas and the processing capabilities required for such advanced features.

In contrast, devices like handheld scanners, tablets, USB 2.0 adapters, and mobile phones are often limited to 1x1 or 2x2 MIMO configurations due to size, power, and cost constraints, making them less likely to support 3x3:3 MIMO and 256 QAM.

DHCP Option 43 is used to provide vendor-specific information to clients, such as the IP address of a Wireless LAN Controller (WLC).When lightweight access points (APs) need to discover a WLC, configuring DHCP Option 43 allows the APs to obtain the necessary information to locate and join the controller.

The CWDP-305 Official Study and Reference Guide details the use of DHCP Option 43 for AP and WLC communication.

Comprehensive and Detailed Explanation:

In a 3x3 802.11n configuration supporting two spatial streams over a 20 MHz channel with a short guard interval (400ns), the maximum data rate achievable is 144 Mbps. This is derived from the MCS (Modulation and Coding Scheme) index tables defined in the 802.11n standard, where MCS 15 corresponds to two spatial streams at 64-QAM modulation with a 5/6 coding rate. Therefore, the correct maximum MCS rate for this configuration is 144 Mbps.

Comprehensive and Detailed Explanation:

Devices dynamically adjust their PHY rates based on link conditions to maintain connectivity. Factors that influence a downward shift in data rates include:

A. Signal degradation: Weaker signals (e.g., due to distance or obstruction) cause devices to drop to more robust, lower PHY rates.

B. Packet loss: High packet error rates trigger rate adjustments to improve reliability.

C. Interference: Competing RF signals can lead to retransmissions and lower effective throughput.

D. Retransmissions: Repeated retransmissions indicate poor link quality, prompting lower data rates to improve reliability.

“A device may reduce PHY rates due to poor SNR, high packet error rates, interference, or excessive retransmissions. Lower data rates offer greater robustness in degraded RF conditions.”

— CWDP-305 Study Guide, Chapter: ProtocolandSpectrum Analysis

Comprehensive and Detailed Explanation:

When calibrating a floor plan for predictive and manual site surveys, using the longest available measurement, such as a straight exterior wall, provides the most accurate and reliable RF data.Longer measurements reduce the impact of scaling errors, ensuring that the entire floor plan is accurately represented in the survey software.Shorter measurements, like those of a single ceiling tile or doorway, can introduce significant scaling errors over larger distances.

In the 2.4 GHz band, 40 MHz channels are formed by bonding two adjacent 20 MHz channels. The primary channel is the one the client uses to initiate communication, and the secondary channel is either above (+1) or below (-1) the primary.

For channel 4 as primary with a +1 secondary offset:

Primary channel: 4 (2.427 GHz)

Secondary channel: 5 (2.432 GHz)

This configuration stays within the allowed channels 1-11.

Detecting interference during a spectrum analysis walkthrough is a critical part of WLAN design. The appropriate action is to record the details using the spectrum analyzer’s logging features or document it for later assessment.

From CWDP-305:

“When interferers are discovered during a walkthrough, they should be recorded and investigated. This documentation helps in adjusting AP placement, channel assignment, or applying mitigation strategies during the design process.”

— Reference: CWDP-305 Official Study and Reference Guide, Chapter on ProtocolandSpectrum Analysis

Wi-Fi 6E introduces access to the 6 GHz spectrum, which provides a significantly larger number of non-overlapping 20 MHz, 40 MHz, and even 80 MHz and 160 MHz channels than the 5 GHz band. This abundance of spectrum allows channel bonding (e.g., 40 MHz) with minimal adjacent channel interference (ACI).

From CWDP-305:

“The availability of contiguous spectrum in the 6 GHz band allows for wider channels, such as 40 MHz and 80 MHz, to be used more frequently without interference issues seen in the 5 GHz band.”

— Reference: CWDP-305 Official Study and Reference Guide, Chapter on Designing for Specific Applications

A survey tray is a lightweight, portable platform that allows WLAN engineers to carry laptops and survey gear comfortably while walking and taking measurements. It helps maintain posture and prevents strain during long survey sessions.

From CWDP-305:

“Using a survey tray allows the engineer to maintain proper posture and prevent back strain while conducting extended walkabouts during site surveys.”

— Reference: CWDP-305 Official Study and Reference Guide, Chapter on Advanced Site Surveys