The authentication method that is referenced in the 802.11-2016 and 802.11-2020 specifications and

is recommended for robust WLAN client security is 802.1X/EAP. 802.1X/EAP stands for IEEE 802.1X

Port-Based Network Access Control with Extensible Authentication Protocol and is a framework that

provides strong authentication and dynamic encryption key generation for WLAN clients. 802.1X/EAP

involves three parties: the supplicant (the client), the authenticator (the AP or the controller), and

the authentication server (usually a RADIUS server). The supplicant sends its credentials (such as

username and password, certificate, or token) to the authenticator, which forwards them to the

authentication server. The authentication server verifies the credentials and sends a response to the

authenticator, which grants or denies access to the supplicant. The authentication server also

generates a master key that is used to derive encryption keys for the data frames between the

supplicant and the authenticator. 802.1X/EAP supports various EAP methods that offer different

levels of security and flexibility, such as EAP-TLS, EAP-PEAP, EAP-TTLS, EAP-FAST, and EAP-SIM. SSL,

IPSec, and WEP are not authentication methods, but rather encryption or security protocols that are

not specific to WLANs or referenced in the 802.11 specifications. Reference: [CWNP Certified

Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 299; [CWNA: Certified

Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 289.

When performing a post-deployment validation survey for voice over Wi-Fi (VoWiFi), an action that

must be performed is Application analysis with an active phone call on a VoWiFi handset. Application

analysis is a method of testing the performance of a specific application over the WLAN by

measuring parameters such as throughput, latency, jitter, packet loss, MOS score, and R-value.

Application analysis with an active phone call on a VoWiFi handset can help to evaluate the quality of

service (QoS) and user experience of VoWiFi calls over the WLAN. It can also help to identify any

issues or bottlenecks that may affect VoWiFi calls such as interference, roaming delays, or insufficient

coverage. Reference: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam

CWNA-109], page 549; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam

CWNA-109], page 519.

A high-density deployment is a wireless network that is designed to support a large number of users

and devices in a relatively small area. This type of deployment is often used in enterprise

environments, such as offices, schools, and hospitals.

The use of semi-directional antennas in the deployment described in the question is a good

indication that it is a high-density deployment. Semi-directional antennas can be used to focus the

signal from an access point in a specific direction. This can help to reduce interference and improve

performance in high-density environments.

The other answer choices are less likely to be correct for the following reasons:

SOHO (small office/home office) deployments are typically smaller and less complex than high-

density deployments.

Residential deployments are typically even smaller and less complex than SOHO deployments.

Standard office deployments may be high-density, but they may also be lower-density.

It is important to note that the type of deployment is not determined solely by the output power of

the access points. However, the use of 10 mW of output power on the 2.4 GHz radios and 20 mW of

output power on the 5GHz radios is also consistent with a high-density deployment.

Here are some additional tips for deploying a high-density wireless network:

Use a site survey to determine the optimal placement of access points.

Configure the access points to use non-overlapping channels.

Use semi-directional or directional antennas to focus the signal and reduce interference.

Implement a wireless intrusion prevention system (WIPS) to detect and mitigate rogue access points

and other security threats.

A BSS (Basic Service Set) is a WLAN use case that represents an 802.11-based network that uses an

AP (Access Point) and has several connecting clients. The AP acts as a central point of coordination

and communication for the clients, which can include iPhones, iPads, laptops, desktops, or any other

devices that have Wi-Fi capabilities. A BSS can be identified by a unique BSSID (Basic Service Set

Identifier), which is usually the MAC address of the AP’s radio interface. A BSS can also be associated

with an SSID (Service Set Identifier), which is a human-readable name that identifies the

network. Reference: , Chapter 1, page 23; , Section 1.1

The inverse square law states that the signal strength of an RF wave is inversely proportional to the

square of the distance from the source. This means that as the distance from the transmitter

increases, the signal strength decreases rapidly.

Reference: Wireless Network Administrator Official Study Guide, Chapter 3, page 64.

The factors that will have the most significant impact on the amount of wireless bandwidth available

to each station within a BSS are:

The number of client stations associated to the BSS

The presence of co-located (10m away) access points on non-overlapping channels

The number of client stations associated to the BSS affects the wireless bandwidth because each

station shares the same channel and medium with other stations in the same BSS. The more stations

there are, the more contention and collision there will be for the channel access, which reduces the

throughput and efficiency of the wireless communication. The wireless bandwidth available to each

station depends on how the access point allocates the channel resources and how the stations use

the channel time. For example, if the access point uses a round-robin scheduling algorithm, each

station will get an equal share of the channel time regardless of its data rate or traffic demand.

However, if the access point uses a proportional fair scheduling algorithm, each station will get a

share of the channel time that is proportional to its data rate and traffic demand, which may result in

higher or lower bandwidth for different stations.

The presence of co-located (10m away) access points on non-overlapping channels affects the

wireless bandwidth because even though they use different channels, they may still cause

interference and noise to each other due to channel leakage or imperfect filtering. The interference

and noise can degrade the signal quality and SNR of the wireless communication, which reduces the

data rate and throughput of the wireless communication. The wireless bandwidth available to each

station depends on how well the access point and the station can cope with the interference and

noise from other channels. For example, if the access point and the station support dynamic

frequency selection (DFS) or adaptive radio management (ARM), they can switch to a less congested

channel or adjust their output power or antenna gain to avoid or minimize interference from other

channels.

Reference: 1, Chapter 3, page 94; 2, Section 3.2

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.

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

page 81

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.

Reference:

CWNA Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109, by David D.

Coleman and David

A . Westcott.

Best practices for conducting pre-design site visits in wireless network planning.

An ACK (Acknowledgement) frame is a short control frame that is sent by the receiver of a data or

management frame to confirm that the frame was received correctly. The ACK frame is sent after a

SIFS (Short Interframe Space) interval, which is the shortest time gap between frames in 802.11. If

the transmitter does not receive an ACK frame within a specified time, it assumes that the frame was

not delivered and must be retransmitted. This is part of the 802.11 reliability mechanism that

ensures reliable data delivery over an unreliable wireless medium . Reference: [CWNA-109 Study

Guide], Chapter 5: IEEE 802.11 Medium Access, page 209; [CWNA-109 Study Guide], Chapter 5: IEEE

802.11 Medium Access, page 203.

OFDM is a modulation method that divides the channel bandwidth into multiple subcarriers, each

carrying a single data symbol. This allows for higher data rates and more robust transmissions in

multipath environments. OFDM was first introduced in the 802.11a standard, which operates in the 5

GHz band and supports data rates up to 54 Mbps. Later, the 802.11g standard adopted OFDM for the

2.4 GHz band, and the 802.11n and 802.11ac standards enhanced OFDM with features such as MIMO

(Multiple Input Multiple Output), channel bonding, and higher-order modulation schemes to achieve

data rates up to 600 Mbps and 6.9 Gbps, respectively. These standards are collectively known as the

ERP (Extended Rate PHY), HT (High Throughput), and VHT (Very High Throughput) PHYs

. Reference: [CWNA-109 Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts,

page 163; [CWNA-109 Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page

157.