CWDP-305 Certified Wireless Design Professional Questions and Answers

Comprehensive and Detailed Explanation:

For reliable Voice over Wi-Fi (VoWiFi) service, a minimum RSSI of -67 dBm is generally recommended. This level ensures sufficient signal strength to support the quality of service required for voice applications, providing adequate signal-to-noise ratio (SNR) and minimizing the likelihood of dropped calls or poor audio quality.

Comprehensive and Detailed Explanation:

In WLAN architecture, theManagement Planeis responsible for overseeing and configuring the network's operational aspects, including automated RF management tasks such as:

Dynamic Channel Assignment

Transmit Power Control

Load Balancing

Coverage Hole Detection and Correction

These functions ensure optimal performance and reliability of the wireless network by adapting to changing RF conditions.

Antenna gain is a measure of how well an antenna directs or concentrates radio frequency energy in a particular direction. Higher gain antennas focus energy more narrowly, resulting in longer range and better signal strength in the targeted direction.

4λ Dipole:Typically offers modest gain and is omnidirectional, making it unsuitable for high-gain requirements.

Yagi:Provides moderate directional gain, generally up to around 20 dBi.

Horn:Offers directional gain, but usually not exceeding 20-25 dBi.

Dish:Parabolic dish antennas are designed for very high gain applications, often exceeding 30 dBi. They are ideal for point-to-point links over long distances.

Therefore, to achieve a gain of 35 dBi, a dish antenna is the appropriate choice.

Before engaging with a customer, it's crucial to conduct thorough research to understand their business operations, objectives, and challenges. This preparation allows you to tailor your approach and solutions to their specific needs.

Key aspects to research include:

Business Model:Understand the core services or products the company offers.

Customer Base:Identify the primary customers or clients they serve.

Recent Developments:Review recent press releases, news articles, or announcements to stay informed about any significant changes or initiatives.

This proactive approach demonstrates professionalism and a genuine interest in the customer's success, fostering trust and facilitating more productive discussions.

Comprehensive and Detailed Explanation:

When transitioning from a centralized to a distributed data forwarding model in a WLAN architecture, it's important to consider the capabilities of the existing APs. Some APs designed specifically for centralized forwarding may lack the necessary hardware or firmware support to operate effectively in a distributed forwarding mode. This can lead to compatibility issues and may require hardware upgrades or replacements to ensure proper functionality in the new architecture.

In high-density environments with limited DHCP address pools, it's crucial to manage IP address allocation efficiently. Reducing the DHCP lease time to a shorter duration, such as 20 minutes, ensures that IP addresses are recycled more frequently. This approach minimizes the risk of address exhaustion by promptly reclaiming addresses from devices that disconnect or become inactive. While adjusting client timeouts and maximum client limits can help manage network load, they don't directly influence DHCP address utilization.

Centralized data forwarding means all wireless traffic is tunneled back to a central controller, which handles tasks such as filtering, firewalling, and policy enforcement.

From CWDP-305:

“Centralized data forwarding enables consistent policy enforcement and traffic filtering by handling all traffic at the controller rather than at individual APs.”

This approach provides better control and visibility, especially in environments with strict security and traffic management requirements.

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

In this scenario, lightweight APs are connected to access ports on VLANs 7, 8, and 9. When these APs boot up, they obtain IP addresses via DHCP on the VLAN to which they are physically connected. Each AP then establishes a Layer 3 CAPWAP tunnel to the WLAN controller. The initial DHCP process occurs before the tunnel is established, so the IP address assigned to each AP is associated with its local VLAN (7, 8, or 9).DumpsPedia

For accurate deployment of access points in a multi-floor indoor environment, providing a camera and marking tools is essential. A camera allows the installation team to reference visual cues from the design, ensuring APs are placed in the correct locations. Marking tools help in identifying precise mounting points on ceilings or walls, facilitating adherence to the design plan. These tools, combined with the design documentation, enable the installation team to execute the deployment accurately, maintaining the integrity of the WLAN design.

Starting with a Tx Power Level of "1" at 17 dBm, each increment halves the power:

Level 2: 17 dBm - 3 dB = 14 dBm

Level 3: 14 dBm - 3 dB = 11 dBm

Level 4: 11 dBm - 3 dB = 8 dBm

Converting 8 dBm to mW:

10^(8/10) ≈ 6.31 mW

The closest provided option is 6.25 mW.

The primary goal of the initial pre-deployment meeting is to ensure that the deployment team fully understands the design documentation, including the rationale behind design decisions. This understanding is crucial for accurate implementation and to address any potential issues proactively.

Target Wake Time (TWT) is a power-saving feature introduced in 802.11ax (Wi-Fi 6) that allows devices to negotiate specific times to wake up and communicate, reducing the need for constant listening and thereby conserving battery life. This feature is particularly beneficial for IoT devices and other battery-powered clients.

In a centralized data forwarding architecture, Access Points (APs) tunnel all client traffic to the WLAN controller.The controller then processes this traffic and forwards it to the appropriate destination.During this process, the controller maps the Differentiated Services Code Point (DSCP) values from the client's IP packets to the appropriate IEEE 802.1Q priority tag values.This mapping ensures that Quality of Service (QoS) is maintained across the wired network, allowing switches and routers to prioritize traffic based on these tags.Cisco

Disabling legacy 802.11b data rates (such as 1, 2, 5.5, and 11 Mbps) improves efficiency by reducing airtime used for low data rate transmissions. These rates significantly increase channel occupancy time and reduce network throughput. It also helps eliminate backward compatibility modes like protection mechanisms.

From CWDP-305:

“One of the most effective ways to improve efficiency in 2.4 GHz networks is to disable the use of legacy 802.11b rates. This prevents low-rate clients from consuming excessive airtime and reduces the need for protection frames.”

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

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.

Comprehensive and Detailed Explanation:

Involving end-users in the final meeting ensures that the WLAN infrastructure meets their needs and expectations.Their feedback is crucial for validating the network's performance and usability, as they are the primary users who will interact with the system daily.

Comprehensive and Detailed Explanation:

WPA/WPA2-Personal is typically used in scenarios where:

A.Client devices lack support for 802.1X/EAP, making enterprise authentication methods unfeasible.

C.Devices are provisioned in bulk with shared credentials, simplifying deployment without the complexity of individual 802.1X configurations.

However:

B.High-latency roaming is undesirable; low-latency is preferred for seamless connectivity.

D.Requiring unique access credentials aligns more with WPA/WPA2-Enterprise, which supports individual authentication.

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.

Comprehensive and Detailed Explanation:

In designing Point-to-Point (PTP) outdoor wireless links, local vegetation plays a significant role in signal propagation and potential attenuation. Key considerations include:

A. Leaves:Foliage, especially leaves, can absorb and scatter RF signals, particularly at higher frequencies. Seasonal changes can affect signal strength due to varying leaf density.

B. Tree height growth:Over time, trees can grow into the line-of-sight path, causing signal obstruction. Planning should account for potential future growth to maintain clear paths.

C. Water density:Vegetation with high water content can absorb RF energy, leading to increased signal attenuation. This is especially pertinent in areas with lush, dense foliage.

D. Reflection factor:While reflections can impact signal quality, in the context of vegetation, absorption and scattering are more critical factors than reflection.

To ensure that Access Points (APs) are installed in the exact locations specified in the design, it's essential to use visual aids and physical markers.Cameras can capture images of the intended installation sites, and marking tools can be used to indicate precise mounting locations on-site.This approach minimizes errors during installation and ensures adherence to the design plan.

The CWDP-305 Official Study and Reference Guide highlights the use of such tools:

"Use cameras and marking tools to document and indicate AP placement, ensuring accurate installation according to the design."

In WLAN deployments, each SSID is typically mapped to a unique VLAN. This allows logical separation of traffic, enabling different security policies, QoS settings, and routing for different user groups or services.

From CWDP-305:

“Each SSID in a WLAN is usually mapped to a different VLAN on the wired infrastructure. This allows for segregation of traffic, application of different network policies, and enhanced security enforcement.”

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

In outdoor environments, channel contention, co-channel interference (CCI), and adjacent channel interference (ACI) can negatively affect bridge performance. The most effective method for identifying usable channels is through a site survey, which includes spectrum analysis at both endpoints.

From CWDP-305:

“Performing an outdoor site survey is critical for point-to-point deployments. This reveals existing RF usage in the area, allowing the selection of channels with minimal interference for optimal link stability.”

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

Mounting location significantly impacts AP radiation patterns and coverage. A wall mount vs. ceiling mount can change signal distribution, SNR, and roaming performance. In such cases, the design assumptions have changed and must be reassessed. Stakeholders must be informed.

From CWDP-305:

“If deviations from the installation design occur, such as AP mounting position changes, the RF environment will likely be affected. The only responsible action is to reassess and, if needed, redesign to meet stated requirements.”

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

In a bandpass filter, the ripple refers to the variation in insertion loss within the passband.If the maximum in-band loss is 1.5 dB and the ripple is 0.4 dB, the minimum in-band loss can be calculated by subtracting the ripple from the maximum loss:blog.knowlescapacitors.com

1.5 dB (maximum loss) - 0.4 dB (ripple) = 1.1 dB (minimum loss)

Therefore, the minimum in-band loss is 1.1 dB.

Effective Isotropic Radiated Power (EIRP) is calculated by adding the transmit power (in dBm) to the antenna gain (in dBi).

Transmit power: 25 mW = 14 dBm

Antenna gain: 3 dBi

EIRP = 14 dBm + 3 dBi = 17 dBm

The CWDP-305 Official Study and Reference Guide provides guidance on calculating EIRP to ensure compliance with regulatory limits and optimal network performance:

"EIRP is the sum of the transmitter output power and the antenna gain, accounting for any losses. Accurate EIRP calculations are essential for regulatory compliance and effective wireless design."

Elevator shafts and similar structures can create RF “dead zones” due to their highly attenuating materials like metal. In such cases, simply increasing power or gain typically does not solve the issue due to shadowing. The recommended approach is to move APs or install additional APs on the obstructed side.

From CWDP-305:

“Obstructions such as elevator shafts may require re-positioning or the addition of APs to ensure proper coverage. These obstructions can block RF propagation regardless of transmit power or antenna gain.”

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

Comprehensive and Detailed Explanation:

Real-Time Location Systems (RTLS) utilize various technologies to track and locate assets or individuals in real-time. The methods include:

A. Sound:Ultrasonic sensors can be used for location tracking by measuring the time it takes for sound waves to travel between devices.

B. 802.11-capable laptops:Wi-Fi-based RTLS can leverage existing 802.11 infrastructure and devices to determine location based on signal strength and triangulation.

C. Active RFID:Active RFID tags have their own power source and can transmit signals to readers, allowing for real-time tracking over longer distances.

D. Infrared:Infrared sensors can be used for location tracking, especially in environments where line-of-sight is available.

F. UWB (Ultra-Wideband):UWB technology provides high-precision location tracking by transmitting signals over a wide frequency spectrum.

G. Passive RFID:Passive RFID tags do not have their own power source and are activated by the electromagnetic field of a reader, suitable for tracking items in close proximity.

E. UHV:Ultra-High Voltage (UHV) is not a technology used in RTLS and is therefore not applicable.

RSSI (Received Signal Strength Indicator):Higher RSSI indicates stronger signal reception.

Noise Floor:Lower noise floor improves clarity of communication.

SNR (Signal-to-Noise Ratio):A high SNR is required for good throughput and reliability.

A well-designed WLAN will have:

High RSSI (strong signal)

Low Noise Floor (less interference)

High SNR (clear distinction between signal and noise)

From CWDP-305:

“A strong, clean signal (high RSSI, low noise) results in higher SNR, which directly correlates with better performance and fewer retransmissions.”

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

The ability to locate a client device using WLAN infrastructure relies on the client actively transmitting frames that can be detected by multiple access points. These frames are typically management or data frames used during association, authentication, or normal operation.

If the client device is turned off, it is not transmitting any 802.11 frames. Therefore, the infrastructure cannot detect or triangulate its location using standard methods such as RSSI (Received Signal Strength Indicator) or time difference of arrival.

According to the CWDP-305 Official Study and Reference Guide (Chapter: Designing for Specific Applications), location-based services (LBS) are dependent on the active participation of the client device. Without beacon frames, probe requests, or any other 802.11 activity, no positioning data can be gathered.

“Client devices must be actively transmitting for their location to be calculated through triangulation or trilateration. If a device is powered off, it cannot be tracked by the WLAN infrastructure.”

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

If the number of APs changes due to budget constraints, a complete redesign is required to reevaluate coverage, capacity, and performance expectations. Increasing transmit power or relying on 2.4 GHz is not a valid solution, as it can result in co-channel interference and poor roaming.

From CWDP-305:

“A design is based on specific coverage and capacity requirements. Any major change, such as reducing the number of APs, requires a full redesign to determine the impact and ensure that business requirements can still be met.”

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

When the WLAN controller and APs reside on different subnets, a router is required to facilitate communication between them. The router enables Layer 3 routing, allowing the APs to discover and communicate with the controller across subnet boundaries.

When using controller-based WLANs, configuration profiles (e.g., for SSIDs, VLANs, radio settings, etc.) are defined on the controller and then assigned to APs—often by AP group or based on AP naming convention or location. This enables automatic provisioning once APs connect to the network.

From CWDP-305:

“Prior to deployment, profiles should be configured on the controller and associated with AP groups or individual APs. Once connected, APs will download their configuration from the controller automatically.”

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

Comprehensive and Detailed Explanation:

High channel utilization can be caused by various factors, but one critical issue to rule out is the presence ofan RF signal generator causing a Denial of Service (DoS)attack. Such devices can emit continuous or intermittent signals that occupy the channel, preventing legitimate Wi-Fi communication. Identifying and eliminating such sources is essential for maintaining optimal network performance.

Low PHY rates: Can contribute to increased airtime usage but are not the primary concern in this context.

High workload or frame rates: Indicate heavy usage but not necessarily malicious interference.

When using predictive design tools for WLAN planning, it's crucial to calibrate the floor plan to ensure accurate distance measurements. This involves setting the scale of the imported floor plan so that the tool can accurately simulate RF propagation and coverage.

The CWDP-305 Official Study and Reference Guide states:

"Before placing APs and other elements, calibrate the floor plan to ensure that distances and areas are accurately represented, which is essential for precise predictive modeling."

Comprehensive and Detailed Explanation:

Virtual Private Networks (VPNs) are commonly employed in WLANs for:

Remote AP tunneling to a corporate WLAN controller or VPN concentrator:This allows remote access points (APs) to securely connect back to the corporate network over the internet, ensuring that data traffic is encrypted and secure.

Client device connectivity to corporate resources from unsecured public networks:VPNs enable client devices to securely access corporate resources when connected to public or unsecured networks, protecting sensitive data from potential threats.

Comprehensive and Detailed Explanation:

Per-user Pre-Shared Keys (PSKs) offer several advantages over a single PSK used across an entire Extended Service Set (ESS):

User-Based Access Control:Assigning unique PSKs to individual users allows for better tracking and control over network access.

Simplified Key Management:If a user's PSK is compromised or they leave the organization, only their key needs to be changed, not the entire network's.

Option C:Per-user PSKs are not a standard defined or certified by the Wi-Fi Alliance; they are an implementation choice.

Option D:Mutual authentication is a feature of WPA/WPA2-Enterprise using 802.1X, not of PSK-based systems.

Band steering is a technique used to encourage dual-band clients to connect to the less congested 5 GHz band.However, some clients may not respond to steering attempts and persist in attempting to connect on the 2.4 GHz band.To ensure connectivity for these persistent clients, APs are designed to eventually respond to their Probe Requests on the 2.4 GHz band after a certain number of ignored attempts.

The CWDP-305 Official Study and Reference Guide states:

"Band steering mechanisms must account for clients that do not support or respond to steering attempts, allowing them to connect on the 2.4 GHz band after a defined number of ignored Probe Requests."

Comprehensive and Detailed Explanation:

Co-Channel Interference (CCI) in the 2.4 GHz band can significantly degrade WLAN performance due to the limited number of non-overlapping channels available.If the WLAN was primarily designed for 5 GHz, the 2.4 GHz band serves as a secondary or best-effort option.In such cases, turning off 2.4 GHz radios on some APs can reduce CCI by minimizing overlapping coverage areas, thereby improving overall network performance.

Barcode scanners are typically used in retail, logistics, and warehouse environments to transmit small amounts of data (e.g., scanned UPC codes) to backend systems. Therefore, their throughput requirements are minimal.

From CWDP-305:

“Barcode scanners and similar IoT devices typically transmit small packets at low intervals and have very low throughput requirements. WLAN design for such devices should focus on coverage and roaming, not capacity.”

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

Web-based applicationsare designed to operate over the internet using web browsers. Each user interaction, such as clicking a link or submitting a form, typically results in multiple communications between the client and server. These interactions often involve the transfer of various resources, including HTML files, CSS stylesheets, JavaScript files, images, and other data.

This pattern of frequent back-and-forth communication can place significant demands on network resources, particularly in terms of bandwidth and latency. When designing WLANs to support web-based applications, it's essential to ensure sufficient capacity and performance to handle these demands effectively.

While 802.11ac and 802.11ax standards support theoretical data rates exceeding 1 Gbps, real-world throughput is often lower due to various factors, including management overhead, environmental conditions, and client capabilities. The actual data throughput experienced by clients is typically less than the maximum PHY rates due to protocol overhead and other inefficiencies inherent in wireless communication.

The CWDP-305 Official Study and Reference Guide notes:

"Theoretical maximum data rates are seldom achieved in practice due to factors such as protocol overhead, interference, and client limitations. Therefore, infrastructure upgrades should be based on actual performance requirements and measurements."

Therefore, advising an upgrade to MultiGig switches solely based on the theoretical maximum data rates of 802.11ac and 802.11ax may not be justified without considering actual network performance and requirements.

CAPWAP (Control and Provisioning of Wireless Access Points):Modern standard protocol for tunneling management and data frames between APs and WLCs.

GRE (Generic Routing Encapsulation):Sometimes used by vendors as an alternative tunneling method, especially for data transport.

From CWDP-305:

“CAPWAP is the most widely used protocol for communication between access points and controllers. GRE is also utilized in some vendor implementations for tunneling user data.”

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

The Effective Isotropic Radiated Power (EIRP) is calculated using the formula:

Omni Calculator

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The Things Network

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EIRP (dBm) = Transmit Power (dBm) + Antenna Gain (dBi) - Cable Loss (dB)

The Things Network

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blog.iptel.com.au

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Assuming negligible cable loss, we first convert the transmit power from milliwatts to dBm:

wifinigel.blogspot.com

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Everything RF

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Transmit Power = 25 mW = 10 * log10(25) ≈ 14 dBm

Now, adding the antenna gain:

EIRP = 14 dBm + 3 dBi = 17 dBm

Therefore, the EIRP of the APs in this design is 17 dBm.

If a persistent source of interference cannot be removed, the best course of action is to design around it—usually by changing channels to avoid the affected frequencies. This minimizes the impact on WLAN operation while still coexisting with the interfering device.

From CWDP-305:

“If interference is detected during post-deployment validation and cannot be mitigated by removal, channel reallocation is the most effective way to work around the problem without affecting WLAN integrity.”

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

Comprehensive and Detailed Explanation:

Painting access points (APs) can interfere with their performance and may void the manufacturer's warranty. Most manufacturers advise against painting APs because certain paints, especially those containing metallic particles, can affect radio frequency (RF) propagation and heat dissipation. Additionally, paint can block ventilation openings, leading to overheating, and can cover LEDs or other indicators, hindering maintenance and troubleshooting. Therefore, it's important to consider these factors and consult the manufacturer's guidelines before painting APs.

Extreme Networks

EAP-TLS (Extensible Authentication Protocol-Transport Layer Security) is considered one of the most secure EAP methods. It requires both the client and the server to have certificates, enabling mutual authentication. This method eliminates the need for passwords, reducing the risk of credential theft.

EAP-TTLS allows for server-side certificates and can use passwords for client authentication, making it less secure than EAP-TLS.

PEAP encapsulates EAP within a TLS tunnel, typically using server certificates and password-based client authentication.

Among common construction materials, fire-rated steel doors present the highest level of RF attenuation. Steel reflects and absorbs significant RF energy, often reducing signal strength by 10–20 dB or more.

From CWDP-305:

“Fire-rated metal doors and elevator shafts are among the most attenuating structures in a building. These materials reflect and absorb RF signals, severely limiting Wi-Fi propagation.”

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

Active site surveys involve connecting to the WLAN and measuring performance metrics such as signal strength, throughput, and roaming behavior.This type of survey is essential to verify that clients can seamlessly roam between APs without connectivity issues.

The CWDP-305 Official Study and Reference Guide highlights the role of active surveys in assessing the real-world performance of a WLAN, including the effectiveness of roaming configurations.

In wireless site surveys, especially when using predictive modeling tools,calibrationis a critical step to ensure that the simulated RF coverage accurately reflects the real-world environment.

Calibration involves measuring actual signal strengths at various locations within the environment and adjusting thesimul-ationparameters accordingly. This process accounts for real-world factors such as wall materials, furniture, and other obstructions that can affect signal propagation.

Failing to calibrate thesimul-ationcan lead to discrepancies between predicted and actual coverage, potentially resulting in poor network performance and user experience.

The wavelength (λ) of a radio wave is calculated using the formula:

λ = c / f

Where:

c = speed of light (approximately 3 x 10^8 meters/second)

f = frequency in HzScribd

For 802.11ac operating at 5.5 GHz:Quizlet

λ = 3 x 10^8 / 5.5 x 10^9 ≈ 0.0545 meters ≈ 5.45 cm

This approximates to 5.5 cm (2.16 inches).

When designing a WLAN for applications like Telnet, which are sensitive to latency and require consistent connectivity, it's crucial to minimize co-channel interference.Reducing the AP transmit power helps in creating smaller cells, thereby limiting the overlap between adjacent APs operating on the same channel.This approach reduces contention and interference, ensuring a more stable and reliable connection for latency-sensitive applications.

An AP-on-a-Stick (APoS) survey is a method used to validate predictive WLAN designs by temporarily placing an access point at the planned installation location and measuring its performance in the actual environment. This approach helps in confirming the accuracy of the predictive model and ensures that the AP placement will meet the desired coverage and performance requirements.

In the 5 GHz band, all Wi-Fi traffic (802.11a/n/ac/ax) uses OFDM or OFDMA modulation. If multiple APs use overlapping or identical channels, this results in Co-Channel Interference (CCI). Legacy technologies like HR/DSSS and ERP operate in 2.4 GHz and do not contribute to CCI in 5 GHz.

From CWDP-305:

“CCI occurs when multiple devices share the same channel. In 5 GHz, all compliant Wi-Fi traffic uses OFDM-based PHYs, so other nearby OFDM networks are a primary source of CCI.”

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

Comprehensive and Detailed Explanation:

The current WLAN setup with only two APs supporting over 300 client devices is insufficient and leads to performance degradation. Simply adding more APs without a proper design can cause co-channel interference and other issues. Upgrading Ethernet connections or increasing AP power does not address the core problem of inadequate design for high-density environments. The appropriate action is to redesign the WLAN specifically for the auditorium, considering factors such as client density, application requirements, and RF environment to ensure reliable and efficient Wi-Fi performance.

Comprehensive and Detailed Explanation:

In the "local MAC" variation of the centralized WLAN architecture, all MAC (Media Access Control) functions are performed by the Access Point (AP). A minimal subset of network control is offloaded to the WLAN controller, which also handles management and monitoring functions. This approach allows for more efficient processing at the edge of the network, reducing latency and improving performance.

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.

In Voice over WLAN (VoWLAN) deployments, it's crucial to differentiate between various types of voice-related traffic to ensure optimal Quality of Service (QoS).Real-Time Protocol (RTP) carries the actual voice payload, while control protocols like RTCP manage session control and quality feedback.Assigning distinct priority levels to these traffic types allows the network to prioritize voice payloads appropriately while still handling control traffic efficiently.

Comprehensive and Detailed Explanation:

For Voice over IP (VoIP) over WLAN, seamless roaming is critical to maintain call quality. To achieve this:

D.Ensuring that at least two access points (APs) are visible with adequate signal strength from any location allows client devices to roam between APs without dropping the connection. This overlap facilitates smooth handoffs and maintains call continuity.

A.While measuring cell overlap is useful, the key is to design the network to provide the necessary overlap, not just measure it.

B.Increasing output power can lead to larger cells but may cause interference and reduce the number of available channels, which is counterproductive in dense environments.

C.Higher gain antennas focus the signal, which may not provide the desired omnidirectional coverage needed for consistent overlap.

Comprehensive and Detailed Explanation:

Real Time FFT stands for Real Time Fast Fourier Transform.It is a spectrum analysis tool that displays the maximum signal amplitude detected at each frequency in real time.This visualization helps in identifying transient RF events, such as sporadic interference or brief signal spikes, which might not be captured in averaged spectrum analyses.By providing immediate feedback on the RF environment, Real Time FFT graphs are invaluable for troubleshooting and optimizing WLAN performance.

In Wi-Fi networks, the IEEE 802.11e amendment introduces Quality of Service (QoS) features, allowing traffic to be categorized into different Access Categories (ACs) to prioritize data transmission. For Voice over WLAN (VoWLAN) applications, it is crucial to prioritize voice traffic to ensure low latency and jitter. The AC_VO (Voice Access Category) is designated for this purpose, providing the highest priority over other traffic types.

Implementing AC_VO ensures that voice packets are transmitted with minimal delay, which is essential for maintaining call quality in enterprise environments.

In Europe, the 2.4 GHz band includes channels 1 through 13, whereas in North America, channels 12 and 13 are typically not used due to regulatory restrictions.If the AP in the hotel room is operating on channel 13, a laptop configured for North American standards may not detect or connect effectively to that channel, resulting in a low Received Signal Strength Indicator (RSSI).

The CWDP-305 Official Study and Reference Guide explains:

"Client devices configured for specific regulatory domains may not support all channels available in other regions. This can lead to connectivity issues when devices encounter channels that are not permitted in their configured domain."

Therefore, the most likely cause of the low RSSI is the client's inability to properly connect to the AP operating on channel 13, leading it to associate with a more distant AP on a different channel, hence the weaker signal.

Coverage must be validated from the perspective of the least capable or lowest-spec client device expected in the environment. This ensures that all necessary devices—not just the most capable ones—can associate and operate reliably.

From CWDP-305:

“Validating coverage should focus on the least capable client device since it will typically have the weakest radio and lowest sensitivity. This ensures all users can connect and meet performance requirements.”

— Reference: CWDP-305 Official Study Guide, Post-Design Validation Chapter

In environments where access points (APs) are mounted on high ceilings (e.g., over 20 feet), it's essential to direct the wireless signal downwards towards the client devices on the floor. Patch antennas, which are directional antennas, are ideal for this scenario as they can focus the RF energy downward, providing better coverage and signal strength to the intended area.

The CWDP-305 Official Study and Reference Guide emphasizes the importance of antenna selection based on mounting height and coverage requirements:

"When APs are mounted on high ceilings, using directional antennas like patch antennas can help focus the RF energy towards the client devices, ensuring optimal coverage and performance."

Comprehensive and Detailed Explanation:

Enabling the "Validate server certificate" option is a critical security measure when configuring Extensible Authentication Protocol (EAP) types, such as EAP-TLS or PEAP. This setting ensures that the client verifies the authenticity of the RADIUS server's certificate during the authentication process, preventing man-in-the-middle attacks. By validating the server certificate, clients can confirm they are connecting to a legitimate network, thereby maintaining the integrity and security of the WLAN.

Microsoft Learn

A radome (a portmanteau of "radar" and "dome") is a structural, weatherproof enclosure that protects a radar or antenna system. Constructed from materials transparent to radio waves, such as fiberglass, radomes shield antennas from environmental elements like wind, rain, and debris without interfering with signal transmission. They are commonly used in outdoor wireless deployments to ensure the longevity and performance of antenna systems.

The Physical Installation Guide is a document that offers step-by-step instructions for technicians on mounting and configuring access points. It includes details such as mounting locations, orientation, cabling requirements, and configuration settings. This guide ensures that APs are installed consistently and according to the design specifications, which is crucial for optimal network performance. Unlike the Statement of Work or Bill of Materials, which outline project scope and equipment lists respectively, the Physical Installation Guide focuses specifically on the practical aspects of AP deployment.

Maximal Ratio Combining (MRC) is a technique used in MIMO (Multiple Input Multiple Output) systems to improve signal quality by combining multiple received signals. However, 1x1:1 client devices have only one transmit and one receive antenna, making them incapable of utilizing MRC, which requires multiple antennas to combine signals effectively.

The CWDP-305 Official Study and Reference Guide explains:CliffsNotes

"Features like Maximal Ratio Combining, which rely on multiple antennas, are not applicable to single-stream (1x1:1) client devices."

The introduction of a new requirement, such as supporting RFID location tracking, after the site survey has commenced constitutes scope creep.Scope creep refers to the uncontrolled expansion of project scope without corresponding adjustments to time, cost, and resources.Implementing location tracking requires specific design considerations, including AP placement and calibration, which should be planned from the project's outset.Introducing such requirements mid-project can lead to design inefficiencies and increased costs.

iPerf is a widely used open-source network testing tool that measures bandwidth, latency, and packet loss over IP networks. It is frequently used in WLAN and LAN environments to evaluate end-to-end throughput performance.

From CWDP-305:

“iPerf is a commonly used tool for throughput validation in WLAN and LAN designs. It can be used with laptops or mobile devices to generate traffic and measure capacity in a controlled way.”

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

Active site surveys involve connecting to the WLAN and moving through the environment to assess performance metrics such as throughput and signal strength.During this process, roaming behavior is also observed, as the client device transitions between APs.Evaluating roaming performance is critical to ensure seamless connectivity and optimal user experience.

The CWDP-305 Official Study and Reference Guide emphasizes:

"Active surveys not only measure throughput but also provide insights into client roaming behavior, which is essential for validating network performance."

Comprehensive and Detailed Explanation:

Short ASCII passphrases, especially those 12 characters or fewer, are more vulnerable to dictionary attacks. Attackers can use precomputed tables or brute-force methods to guess these passphrases, especially if they are common or simple. The WPA/WPA2-Personal security model relies on the strength of the passphrase; thus, longer and more complex passphrases significantly enhance security.

Option B:The strength of group keys in a BSS is not directly affected by the length of the passphrase but rather by the encryption protocols in use.

Option C:Regardless of the passphrase length, the Pairwise Master Key (PMK) derived is 256 bits.

Option D:Most AP and client vendors support ASCII-based passphrase entry, making this option incorrect.

Site survey adapters are often specialized devices with enhanced sensitivity and are calibrated for accurate measurements. In contrast, standard client devices may have varying hardware and driver configurations, leading to differences in RSSI readings. Therefore, it's common to observe discrepancies between survey results and actual client experiences. This emphasizes the importance of considering client device capabilities during WLAN design and validation.

In a controller-based WLAN infrastructure, when the Wireless LAN Controller (WLC) and Access Points (APs) reside on different subnets, a router is essential to facilitate communication between them.The router enables inter-subnet routing, allowing APs to discover and communicate with the WLC.

The CWDP-305 Official Study and Reference Guide emphasizes the necessity of proper Layer 3 routing for APs to locate and join controllers across different subnets.

Comprehensive and Detailed Explanation:

When troubleshooting 802.1X/EAP authentication issues, consider the following:

A.Ensure the RADIUS server is online and that the APs and WLAN controllers are configured to communicate with it on the correct port. Misconfigured ports can prevent authentication requests from reaching the server.

C.Verify that the authenticator (e.g., AP or controller) supports the EAP type configured on the client. A mismatch can lead to authentication failures.

D.If using certificate-based EAP methods (like EAP-TLS), confirm that the client's certificate is valid, not expired, and trusted by the RADIUS server. Certificate issues are common causes of authentication problems.

Note:

B.The RADIUS shared secret is configured between the authenticator and the RADIUS server, not on the client (supplicant). Therefore, this option is not applicable.

A specification sheet (spec sheet) provides detailed technical capabilities of a device, including supported Wi-Fi standards (e.g., 802.11a/b/g/n/ac/ax), number of spatial streams, band support, and security protocols. This helps WLAN designers understand performance expectations and compatibility.

From CWDP-305:

“Specification sheets are critical for evaluating client capabilities. They include information about supported frequency bands, maximum data rates, MIMO capabilities, and supported security protocols.”

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

Receive sensitivity indicates the minimum signal strength at which a device can successfully receive and demodulate a signal at a specified data rate.In this case, a receive sensitivity of −82 dBm @ 18 Mbps means that the device requires a signal stronger than −82 dBm to reliably demodulate data at 18 Mbps.Therefore, the device must receive a signal with a strength greater than −82 dBm (i.e., closer to 0 dBm) to maintain that data rate.

For long-distance point-to-point wireless links, such as those spanning over 1000 yards, directional antennas are preferred due to their focused beamwidth and higher gain.Yagi antennas are a type of directional antenna known for their high gain and narrow beamwidth, making them suitable for such applications.While panel and patch antennas are also directional, Yagi antennas are specifically designed for long-range communications.

If QoS markings are correct from the client to the AP but incorrect from the AP to the client, it's likely that the QoS markings are being stripped or not trusted somewhere on the wired network between the controller and the AP. This misconfiguration can result in the AP transmitting frames without the appropriate QoS markings, affecting voice quality.

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.

A client-to-AP link imbalance occurs when the AP's transmit power is significantly higher than that of the client device.This disparity can lead to situations where the client can receive signals from the AP but cannot transmit signals back effectively.This imbalance is particularly problematic in environments where clients have limited transmit capabilities, such as battery-powered devices.To mitigate this issue, it's recommended to adjust the AP's transmit power to match the capabilities of the client devices, ensuring balanced communication.

Achieving a 450 Mbps data rate in 802.11n requires specific features:

Short Guard Interval (GI):Reduces the interval between symbols from 800 ns to 400 ns, increasing throughput.

40 MHz Channels:Doubles the channel width compared to 20 MHz, allowing more data to be transmitted.

3 Spatial Streams:Utilizes multiple antennas to transmit separate data streams simultaneously, significantly boosting data rates.

While frame aggregation and transmit beamforming enhance performance and reliability, they are not prerequisites for achieving the 450 Mbps MCS rate.

Comprehensive and Detailed Explanation:

Transitioning from a centralized to a distributed data forwarding model can introduce compatibility issues. Specifically:

C.Some APs designed for centralized architectures may lack the necessary hardware or firmware capabilities to support distributed forwarding features, such as local breakout or direct client-to-client communication, leading to potential limitations in functionality.

The Physical Installation Guide is developed during the design phase and delivered to the installation team. It contains detailed AP locations (including mounting heights and orientations), cabling instructions, hardware installation standards, and any specific AP configuration notes needed during physical deployment.

From CWDP-305:

“A Physical Installation Guide provides specific instructions to installers, such as mounting height, orientation, and any environmental considerations. This ensures that APs are installed correctly and according to the design.”

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

802.11 admission control mechanisms are employed to manage and regulate the bandwidth resources available in a WLAN.By controlling the admission of traffic into the network, these mechanisms ensure that high-priority traffic, such as voice or video, receives the necessary resources for optimal performance.Admission control settings are configured separately for each Access Category (AC), allowing granular control over different types of traffic.

Comprehensive and Detailed Explanation:

IEEE 802.3at, also known as PoE+, provides up to 30 watts of power per port. To calculate the minimum Power over Ethernet (PoE) budget required for 6 access points (APs):

30 W/AP × 6 APs = 180 W

Therefore, a switch must have a minimum PoE budget of180 wattsto support six 802.3at-powered APs.

Software-defined radios (SDRs) offer flexibility in RF operation. In dual-band APs, an SDR can be programmed to operate on either 2.4 GHz or 5 GHz, allowing dynamic optimization of the spectrum based on demand and interference.

From CWDP-305:

“Software-defined radios can be configured to operate in either band, allowing administrators to shift coverage based on band congestion or capacity requirements.”

This flexibility helps address issues in high-density deployments or when minimizing interference is critical.

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

In high-density venues such as stadiums or convention centers, the presence of large crowds significantly impacts Wi-Fi signal propagation. Human bodies consist mostly of water, which absorbs and attenuates radio frequency (RF) signals, especially in the 2.4 GHz and 5 GHz bands commonly used by Wi-Fi. This absorption leads to reduced signal strength and potential connectivity issues during events when the venue is filled with people.

Designing a WLAN for such environments requires careful consideration of crowd density and its impact on RF signals. Strategies may include increasing the number of APs, using directional antennas to focus coverage, and conducting site surveys during events to assess real-world performance.

To authenticate users against an LDAP database for WLAN access, a RADIUS (Remote Authentication Dial-In User Service) server must be implemented. RADIUS acts as an intermediary between the WLAN infrastructure and the LDAP directory, facilitating authentication requests. When a user attempts to connect to the WLAN, the access point forwards the authentication request to the RADIUS server, which then queries the LDAP directory to verify the user's credentials. This integration ensures centralized authentication and enhances security by leveraging existing directory services.

Channels 116-124 in the 5 GHz band fall under the Dynamic Frequency Selection (DFS) range. These channels are shared with radar systems, such as those used by airports. When radar activity is detected, Access Points (APs) operating on DFS channels must vacate the channel, leading to potential disruptions in service. In environments near airports, it's advisable to avoid using DFS channels to prevent such interruptions, ensuring a stable and reliable wireless experience for voice devices.

Comprehensive and Detailed Explanation:

RF fingerprinting is a method used in WLANs to determine the location of a device by comparing the current signal characteristics (like signal strength and quality) to a pre-recorded database of signal profiles (fingerprints) taken at various locations. This technique allows for accurate indoor positioning without relying solely on signal strength calculations.

Option A:Inverse cube law is not typically used in WLAN location algorithms.

Option B:Free Space Path Loss (FSPL) calculations are more theoretical and less effective in complex indoor environments.

Option D:Clause 16 of the 802.11 standard pertains to mesh networking, not location algorithms.

Once the WLAN is validated and operational, the next step is knowledge transfer. Support staff must be trained on monitoring, troubleshooting, and configuration, while end-users benefit from understanding basic usage and policies. Executives and guests are not directly involved in daily operations.

From CWDP-305:

“Training should be delivered to IT support staff responsible for WLAN operations, and optionally to end-users for user-side clarity. This ensures ongoing support, proper use, and reduced downtime.”

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

Upgrading access points (APs) from 802.11n to 802.11ac can offer higher throughput and improved performance. However, to realize these benefits, client devices must also support the newer standard. If the clients remain on 802.11n, they cannot take advantage of 802.11ac features such as wider channels, higher modulation schemes, and beamforming.

Therefore, the most likely reason for the unchanged throughput is that the clients were not upgraded to support 802.11ac.