CWNP CWNA-109 Dumps

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

The client drivers are faulty and should be upgraded is the likely problem for the laptop that can see and connect to 2.4 GHz APs, but does not even see 5 GHz APs. The client drivers are the software components that enable the wireless adapter of the laptop to communicate with the operating system and the network. The client drivers are responsible for scanning the available wireless channels, detecting and connecting to the access points, negotiating the security and data rate parameters, and transmitting and receiving data frames. If the client drivers are faulty, outdated, or incompatible, they may cause various issues with the wireless performance and functionality, such as low data rates, poor signal strength, frequent disconnections, or inability to see or connect to certain access points or channels.

One of the possible causes of faulty client drivers is that they do not support or recognize some of the features or standards of the 802.11ac technology, such as wider channel bandwidths, higher modulation schemes, or DFS (Dynamic Frequency Selection) channels. This could explain why the laptop can see and connect to 2.4 GHz APs, but not 5 GHz APs, as 802.11ac operates only in the 5 GHz band and uses channels that are wider (up to 160 MHz) and higher (up to channel 165) than those used by previous standards. Moreover, some of the 5 GHz channels are subject to DFS rules, which require the access points and client stations to monitor and avoid using channels that are occupied by radar systems or other primary users. If the client drivers do not support or comply with DFS rules, they may not be able to see or connect to access points that use DFS channels.

To solve this problem, the client drivers should be upgraded to the latest version that supports and is compatible with 802.11ac features and standards. This can be done by downloading and installing the updated driver software from the manufacturer’s website or using a device manager tool. Upgrading the client drivers may also improve other aspects of wireless performance and functionality, such as data rates, signal strength, security, and stability. References: 1, Chapter 12, page 493; 2, Section 8.1

a mesh portal is a device that connects a mesh BSS (MBSS) to an Ethernet network, such as the Internet. A mesh portal acts as a bridge between the wired and wireless domains, and allows the mesh stations to communicate with external networks. A mesh portal is also a mesh point, which means it can forward traffic within the MBSS.

The other options are not correct. Option A. Mesh Gate is a device that connects a mesh BSS (MBSS) to another mesh BSS or another wireless network, such as an infrastructure BSS or an ad hoc network2. A mesh gate acts as a gateway between different wireless domains, and allows the mesh stations to communicate with other wireless networks. A mesh gate is also a mesh point, which means it can forward traffic within the MBSS. Option B. Mesh Switch is not a valid term in the 802.11 standard. Option C. Mesh Router is also not a valid term in the 802.11 standard.

The solution that you recommend is an Overlay WLAN monitoring solution. An Overlay WLAN monitoring solution is a system that uses dedicated sensors or probes to monitor the WLAN performance over time. The sensors are deployed throughout the WLAN coverage area and collect data on various metrics such as signal strength, noise level, channel utilization, interference, throughput, latency, packet loss, and QoS. The sensors send the data to a centralized server or appliance that analyzes the data and provides a single pane of glass for administration and monitoring of the solution. An Overlay WLAN monitoring solution can help to detect and troubleshoot WLAN issues, optimize WLAN performance, and generate reports and alerts. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 538; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 508.

To calculate the EIRP at the antenna element, we need to add the transmitter output power, subtract the cable loss, and add the antenna gain. All these values need to be converted to dBm first, if they are not already given in that unit. In this case, we have:

Transmitter output power = 50 mW = 10 log (50) dBm = 16.99 dBm Cable loss = 3 dB Antenna gain = 9 dBi

EIRP = Transmitter output power - Cable loss + Antenna gain EIRP = 16.99 - 3 + 9 EIRP = 22.99 dBm

Rounding up to the nearest integer, we get 23 dBm as the EIRP at the antenna element12. References: CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 92; CWNA-109Study Guide, Chapter 2: Radio Frequency Fundamentals, page 88.

WPA2 (Wi-Fi Protected Access 2) is a security certification program developed by the Wi-Fi Alliance to secure wireless computer networks. It is important to understand the following:

• WPA2 and the 802.11 Standard: While WPA2 is based on elements of the 802.11i amendment to the 802.11 standard, it is not itself a standard but rather a certification to ensure devices comply with certain security criteria, including the correct implementation of CCMP (Counter Mode Cipher Block Chaining Message Authentication Code Protocol) and AES (Advanced Encryption Standard).
• CCMP/AES Implementation: WPA2 enhances the security of wireless networks by using CCMP for encryption, which is based on AES, a robust encryption algorithm. This represents a significant security improvement over WEP (Wired Equivalent Privacy) and WPA (Wi-Fi Protected Access) that used TKIP (Temporal Key Integrity Protocol).
• WPA vs. WPA2: WPA was the interim security enhancement over WEP, utilizing TKIP for encryption. WPA2, however, moved to the more secure AES-based encryption method. Contrary to option C, WPA2 does not enhance security by using TKIP; it uses CCMP/AES.

Therefore, option B correctly describes WPA2 as a certification program ensuring devices properly implement the more secure CCMP/AES encryption methods.

References:

• Wi-Fi Alliance website for WPA2 certification details.
• IEEE 802.11i-2004: Amendment for Enhanced Security.

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.

DHCP (Dynamic Host Configuration Protocol) is the network service where option 43 must be configured to allow access points to locate controllers. DHCP is a protocol that allows a device to obtain an IP address and other network configuration parameters from a server. In a wireless controller scenario, the access points can use DHCP to request an IP address from a DHCP server, which can also provide the IP address or hostname of the wireless controller as an option in the DHCP response. Option 43 is a vendor-specific option that can be used to encode custom information for different types of devices. For example, Cisco access points can use option 43 to receive the IP address of the wireless controller from the DHCP server, while Aruba access points can use option 43 to receive the hostname of the wireless controller from the DHCP server. This way, the access points can discover the wireless controller and establish a connection with it. References: 1, Chapter 8, page 309; 2, Section 5.2

The tool described is a WLAN (Wireless Local Area Network) scanner tool. WLAN scanner tools are designed to provide information about the wireless networks in a given area, including:

• Signal Strength: They show the signal strength of all access points (APs) in the vicinity, which is crucial for understanding the coverage area and potential interference.
• SSID Visualization: These tools display the SSIDs (Service Set Identifiers) of available networks, allowing users to identify different wireless networks easily.
• Security Settings Information: WLAN scanner tools often show the type of security implemented on each network, such as WPA2, WEP, etc.
• Frequency Band Filtering: They allow users to filter and view networks based on the frequency band (2.4 GHz or 5 GHz), which is useful for analyzing network distribution and planning.

While protocol analyzers, site survey utilities, and spectrum analyzers are also used in wireless networking, their functions are distinct from what is described:

• Protocol Analyzersare more sophisticated and are used to capture and analyze network traffic.
• Site Survey Utilitiesare used to map signal coverage and plan network layouts, often with more advanced features for detailed site surveys.
• Spectrum Analyzersprovide a detailed view of the frequency spectrum and non-Wi-Fi interference but don't typically focus on SSIDs or security settings.

Thus, the correct answer is D, a WLAN scanner tool, based on the functionalities described.

References:

• CWNA Certified Wireless Network Administrator Official Study Guide: Exam PW0-105, by David D. Coleman and David A. Westcott.
• Tools and techniques for wireless network analysis and troubleshooting.

 A Wi-Fi scanner is a basic tool that can be used to easily locate areas of high co-channel interference. A Wi-Fi scanner is a software application that can run on a laptop, tablet, smartphone, or other device that has a Wi-Fi adapter. A Wi-Fi scanner can scan the wireless environment and display information about the detected access points and client stations, such as their SSID, BSSID, channel, signal strength, security, and data rate. A Wi-Fi scanner can also show the channel utilization and overlap of different access points, which can indicate the level of co-channel interference. Co-channel interference is a type of interference that occurs when multiple access points use the same or adjacent channels within the same coverage area. Co-channel interference can reduce the throughput and performance of the WLAN, as the access points and client stations have to contend for the channel access and avoid collisions. To identify areas of high co-channel interference, a Wi-Fi scanner can be used to measure the signal strength and channel utilization of different access points and compare them with a threshold or a baseline. Alternatively, a Wi-Fi scanner can also use a color-coded heat map to visualize the co-channel interference level in different locations. References: 1, Chapter 7, page 279; 2, Section 4.3

The statement that the lowest voltage drop is achieved when using CAT6 cable instead of Cat5 or CAT5e is true about 802.3, Clause 33 Power over Ethernet. Power over Ethernet (PoE) is a technology that allows electrical power to be delivered over Ethernet cables along with data signals. PoE is defined by IEEE 802.3, Clause 33 and has several variants, such as PoE (802.3af), PoE+ (802.3at), and PoE++ (802.3bt). PoE works by using a device called PSE (Power Sourcing Equipment) that injects power into the Ethernet cable and a device called PD (Powered Device) that receives power from the Ethernet cable. The PSE can be either an endpoint device, such as a switch or a router, or a midspan device, such as an injector or a splitter, that is inserted between two Ethernet devices. The PD can be any device that requires power, such as an access point, a camera, or a phone.

One of the factors that affects PoE performance is voltage drop, which is the reduction of voltage that occurs as current flows through a cable due to its resistance. Voltage drop can cause power loss and inefficiency in PoE systems, as well as damage to PDs if the voltage falls below their minimum requirement. To minimize voltage drop, it is recommended to use high-quality cables with low resistance and short length. Among the common types of Ethernet cables, CAT6 has the lowest resistance and therefore the lowest voltage drop compared to Cat5 or CAT5e. CAT6 also has higher bandwidth and data rate than Cat5 or CAT5e, making it more suitable for PoE applications. References: 1, Chapter 7, page 263; 2, Section 4.4

The short guard interval is an optional feature of 802.11n and 802.11ac that reduces the time between OFDM symbols from 800 ns to 400 ns. This can increase the data rate by about 11%, but also requires more precise timing and synchronization between the transmitter and the receiver. The short guard interval is only used when both the AP and the client support it and agree to use it . References: [CWNA-109 Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page 163; [CWNA-109Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page 157.

The unit of measurement that is an absolute unit and is used to quantify received signal power levels on a logarithmic scale is dBm. dBm stands for decibel-milliwatt and represents the power level relative to 1 milliwatt (mW). dBm is an absolute unit because it has a fixed reference point and does not depend on the input power level. dBm is used to measure the received signal power levels on a logarithmic scale because it can express large variations in power levels with small numbers and make calculations easier. For example, a 10 dB increase in power level means a 10-fold increase in power, and a 20 dB increase means a 100-fold increase in power. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 66; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 56.

An access point is configured by a WLAN controller in the management plane of the three networking planes. The management plane is responsible for the configuration, administration, and monitoring of network devices, such as access points, switches, routers, and controllers. The WLAN controller communicates with the access point using a management protocol, such as CAPWAP or SNMP, to send configuration commands and receive status information. The control plane is responsible for the routing, switching, and forwarding of network traffic, such as data frames and control frames. The WLAN controller may also participate in the control plane by performing functions such as authentication, encryption, roaming, and load balancing. The security plane is responsible for the protection of network devices and data from unauthorized access, modification, or disclosure. The WLAN controller may also participate in the security plane by implementing features such as firewall, VPN, IDS/IPS, and WIPS. The data plane is responsible for the transmission and reception of user data, such as voice, video, or web traffic. The WLAN controller may or may not participate in the data plane depending on the architecture of the WLAN. In some cases, the access point forwards the user data directly to the wired network without involving the WLAN controller (distributed data forwarding). In other cases, the access point tunnels the user data to the WLAN controller before forwarding it to the wired network (centralized data forwarding). References: CWNA-109 Study Guide, Chapter 9: Wireless LAN Architecture, page 279

VoIP (Voice over Internet Protocol) is an application that is likely used that demands the requirements of unidirectional delays of less than 150 ms and the signal strength at all receivers can be no lower than -67 dBm. VoIP is an application that allows users to make and receive voice calls over a network, such as the Internet or a WLAN. VoIP is a real-time and interactive application that requires high quality of service (QoS) to ensure good user experience and satisfaction. One of the QoS metrics for VoIP is delay, which is the time it takes for a voice packet to travel from the sender to the receiver. Delay can affect the quality and intelligibility of the voice conversation, as well as the synchronization and naturalness of the dialogue. The ITU-T G.114 recommendation suggests that the maximum acceptable one-way delay for VoIP should be less than 150 ms, as anything higher than that can cause noticeable degradation and annoyance to the users. Another QoS metric for VoIP is signal strength, which is the measure of how strong the RF signal is at the receiver. Signal strength can affect the reliability and performance of the wireless connection, as well as the data rate and throughput of the VoIP traffic. The CWNA Official Study Guide recommends that the minimum signal strength for VoIP should be -67 dBm, as anything lower than that can cause packet loss, retries, jitter, and other issues that can impair the voice quality. References: 1, Chapter 10, page 398; 2, Section 6.1

Airtime Utilization is a per-channel statistic that defines what percentage of the channel is currently being used, and what percentage is therefore free. Airtime usage can come from: Data traffic to and from client devices. Interference from WiFi and non-WiFi sources. Management overhead from APs and client devices.

TWT is the feature of 802.11ax (HE) that is managed with beacon and trigger frames and is primarily a power management method, but also provides more efficient access to the channel used within a BSS. TWT stands for target wake time, which is a mechanism that allows an access point and a client device to negotiate and schedule specific times for data transmission and reception. This enables the client device to enter a low-power sleep mode when it is not expected to communicate with the access point, which saves battery life and reduces power consumption. TWT also reduces contention and interference on the channel used within a BSS, as it coordinates the transmissions of multiple client devices and avoids collisions. TWT is managed with beacon and trigger frames, which are two types of management frames that are used to announce and initiate data exchanges. A beacon frame is a frame that is periodically sent by an access point to advertise its presence, capabilities, and parameters to client devices. A trigger frame is a frame that is sent by an access point or a client device to request or initiate a data transmission with another device. BSS color, UL-MU-MIMO, and OFDMA are other features of 802.11ax (HE) that are not primarily power management methods, but rather performance enhancement methods. BSS color is a feature that assigns a color code to each BSS to differentiate it from other BSSs that use the same channel. This reduces interference and improves spatial reuse of the channel. UL-MU-MIMO is a feature that allows an access point to receive multiple simultaneous transmissions from different client devices using multiple spatial streams. This increases capacity and throughput of the uplink direction. OFDMA is a feature that divides a channel into smaller subchannels called resource units (RUs) that can be allocated to different devices for concurrent transmissions. This increases efficiency and flexibility of the channel utilization. References: CWNA-109 Study Guide, Chapter 10: Wireless LAN Operation, page 323

A 5 GHz channel should be used for this AP because channels 1 and 6 are 2.4 GHz channels and they have no impact on the decision. The 5 GHz frequency band offers more non-overlapping channels than the 2.4 GHz frequency band, which reduces interference and improves performance. The 5 GHz frequency band also supports higher data rates and wider channel bandwidths than the 2.4 GHz frequency band, which increases capacity and throughput. The 5 GHz frequency band also has less interference from other devices and sources than the 2.4 GHz frequency band, which enhances reliability and quality of service. Therefore, it is recommended to use the 5 GHz frequency band for WLANs whenever possible. Channels 1 and 6 are two of the three non-overlapping channels in the 2.4 GHz frequency band (the other one is channel 11). They are used by a neighbor network in this scenario, but they do not affect the channel selection for this AP because they operate in a different frequency band than the 5 GHz frequency band. Channel 6 is not always best to use; it depends on the interference and congestion level in the environment. Channel 1 is not best to use because it has a lower frequency than channel 6; frequency does not determine channel quality or performance. Channel 11 is not best to use because it is also a 2.4 GHz channel and it may interfere with channels 1 and 6. References: CWNA-109 Study Guide, Chapter 4: Antenna Systems and Radio Frequency (RF) Components, page 113

The center frequency of channel 4 in the 2.4 GHz band is 2.427 GHz (2427 MHz). The center frequency of a channel is the midpoint of its frequency range, where the signal strength is highest and most concentrated. The center frequency of channel 1 in the 2.4 GHz band is 2.412 GHz (2412 MHz), as given in the question. The center frequency of each subsequent channel is obtained by adding 5 MHz to the previous channel’s center frequency, since the channels are spaced 5 MHz apart from each other in this band. Therefore, to find the center frequency of channel 4, we need to add 15 MHz (5 MHz x 3) to the center frequency of channel 1:

2.412 GHz + 0.015 GHz = 2.427 GHz

Alternatively, we can use a formula to calculate the center frequency of any channel in the 2.4 GHz band:

Center frequency (GHz) = 2.407 + (0.005 x Channel number)

Using this formula for channel 4, we get:

Center frequency (GHz) = 2.407 + (0.005 x 4)

Center frequency (GHz) = 2.407 + 0.02

Center frequency (GHz) = 2.427 References: 1, Chapter 3, page 85; 2, Section 3.2

In addition to coverage analysis results, what should be included in a post-deployment site survey report to ensure WLAN users experience acceptable performance is Capacity analysis results. Capacity analysis is a method of testing the ability of the WLAN to support the expected number and type of users, devices, and applications. Capacity analysis can help to determine the optimal number and placement of access points, the appropriate channel and power settings, the required QoS policies, and the expected throughput and latency levels. Capacity analysis results can help to verify that the WLAN meets the performance requirements and service level agreements (SLAs) of the organization. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 548; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 518.

The response that you should give to your manager’s suggestion of implementing the security practices of disabling the broadcasting of the SSID in Beacons and configuring the access points not to respond to Probe Request frames that have a null SSID field is that any 802.11 protocol analyzer can see the SSID in clear text in frames other than Beacons frames. This negates any security benefit of trying to hide the SSID in Beacons and Probe Response frames. The SSID (Service Set Identifier) is a human-readable name that identifies a WLAN and allows users to connect to it. The SSID is transmitted in clear text in several types of 802.11 frames, such as Beacon frames, Probe Request frames, Probe Response frames, Association Request frames, Association Response frames, Reassociation Request frames, and Reassociation Response frames. Some people may think that hiding the SSID can improve the security of the WLAN by making it invisible to potential intruders. However, this is not true, as hiding the SSID only removes it from Beacon frames and Probe Response frames that have a null SSID field. The SSID is still present in other types of frames that can be easily captured and analyzed by any 802.11 protocol analyzer or wireless scanner tool. Therefore, hiding the SSID does not provide any real security benefit and may even cause some compatibility and performance issues for legitimate users. References: 1, Chapter 4, page 133; 2, Section 4.1

The HT (802.11n) physical layer (PHY) specification includes support for and compatibility with both ERP and HR/DSSS. ERP stands for Extended Rate PHY, which is an extension of the original DSSS (Direct Sequence Spread Spectrum) PHY that supports data rates up to 54 Mbps in the 2.4 GHz band. HR/DSSS stands for High Rate/Direct Sequence Spread Spectrum, which is another extension of DSSS that supports data rates up to 11 Mbps in the 2.4 GHz band. HT stands for High Throughput, which is a new PHY that supports data rates up to 600 Mbps in both the 2.4 GHz and 5 GHz bands. HT uses OFDM (Orthogonal Frequency Division Multiplexing) as its modulation scheme, but it also supports legacy DSSS and ERP devices by using a dual preamble and header structure that allows backward compatibility. References: , Chapter 3, page 103; , Section 3.1

Cellular/LTE/5G is the best method for implementing a network backhaul for communications across the Internet in a remote area that is affected by a natural disaster. This is because cellular/LTE/5G networks are wireless and do not depend on physical infrastructure that may be damaged or unavailable in such scenarios. Cellular/LTE/5G networks also offer high-speed data transmission and wide coverage area, which are essential for emergency response operations. 802.11 bridging to the response team headquarters is not feasible because it requires line-of-sight and has limited range. Turning up the output power of the WLAN at the response team headquarters is not effective because it may cause interference and does not guarantee reliable connectivity. Temporary wired DSL is not practical because it requires installing cables and equipment that may not be available or accessible in a remote area. References: CWNA-109 Study Guide, Chapter 7: Wireless LAN Topologies, page 2031

WLAN bridges must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally. A WLAN bridge is a device that connects two or more networks using the 802.11 protocol. A WLAN bridge must have a clear and strong signal between the two endpoints to ensure reliable and fast data transmission. The signal-to-noise ratio (SNR) is a measure of the quality of the signal, which depends on the distance, interference, obstacles, and antenna gain between the transceivers. A higher SNR means a better signal quality and a higher data rate. A lower SNR means a worse signal quality and a lower data rate. Therefore, a WLAN bridge must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally1.

The common spectrum analyzer view that you should use for this analysis is the Waterfall/Spectrogram view. The Waterfall/Spectrogram view shows the signal from the interfering device over time on a three-dimensional graph. The x-axis represents frequency, the y-axis represents time, and the z-axis represents amplitude or power. The color of each pixel indicates the signal strength at a given frequency and time. The Waterfall/Spectrogram view can help you identify the characteristics of the interference source, such as its frequency range, duty cycle, modulation type, and pattern. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 524; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 494.

VHT TXOP (Very High Throughput Transmit Opportunity) power save is a feature introduced with the 802.11ac amendment, which is designed to improve the power efficiency of devices connected to a WLAN. This feature enhances battery life in several ways, compared to the legacy Power Save mode:

• Enhanced Power Saving: VHT TXOP power save allows devices to disable more components of the WLAN transceiver when they are in a low power state. This reduces the power consumption during periods when the device is not actively transmitting or receiving data.
• Intelligent Wake-Up Mechanisms: It employs more sophisticated mechanisms for devices to determine when they need to wake up and listen to the channel, further reducing unnecessary power usage.
• Optimized Operation: This power save mode is optimized for the high-throughput environment of 802.11ac networks, allowing devices to efficiently manage power while maintaining high performance.

Legacy Power Save mode, introduced in earlier versions of the 802.11 standards, does not provide the same level of component disablement or the intelligent wake-up mechanisms found in VHT TXOP power save, making option B the correct answer.

References:

• IEEE 802.11ac-2013 Amendment: Enhancements for Very High Throughput for Operation in Bands below 6 GHz.
• CWNA Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109, by David D. Coleman and David A. Westcott.

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 thethroughput 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.

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

The string of characters and digits that is entered into an AP and a client STA for WPA2 security and is 8 characters long is called a passphrase. A passphrase is a human-readable text that is used to generate a Pre-Shared Key (PSK) for WPA2-Personal security. A passphrase can be between 8 and 63 characters long and can include any ASCII character. The PSK is a 256-bit key that is derived from the passphrase using a hashing algorithm called PBKDF2. The PSK is used to encrypt and decrypt the data frames between the AP and the client STA. A MSK is a Master Session Key that is generated by an authentication server for WPA2-Enterprise security. A WEP key is a 40-bit or 104-bit key that is used for Wired Equivalent Privacy (WEP) security, which is deprecated and insecure. A PSK is not a string of characters and digits, but a binary key. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 303; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 293.

PoE stands for Power over Ethernet, which is a technology that allows network devices to receive power and data over the same Ethernet cable. PoE eliminates the need for separate power adapters or outlets for devices such as IP phones, cameras, or APs. PoE requires two types of devices: PSE (Power Sourcing Equipment) and PD (Powered Device). A PSE is a device that provides power to the Ethernet cable, such as a switch, injector, or splitter. A PD is a device that receives power from the Ethernet cable, such as an IP phone, camera, or AP. When implementing PoE, a switch plays the role of a PSE910. References: CWNA-109 Study Guide, Chapter 7: Power over Ethernet (PoE), page 293; CWNA-109Study Guide, Chapter 7: Power over Ethernet (PoE), page 287.

The client STA can use Beacon frames transmitted by the AP to verify that an AP supports the same data rates that it supports. Beacon frames are management frames that are periodically broadcasted by the APs to announce their presence, capabilities, and parameters. Oneof the information elements contained in the Beacon frames is the Supported Rates or Extended Supported Rates, which lists the data rates that the AP can use for communication. The client STA can compare its own data rates with those advertised by the AP to determine if they are compatible. Data frames, authentication frames, and probe request frames do not contain information about data rates. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 133; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 123.

The power level at the Intentional Radiator (IR) is 250 mW. The IR is the point where the RF signal leaves the transmitter and enters the antenna system. To calculate the power level at the IR, we need to consider the output power level of the transmitter, the loss of the cable, and the gain of the antenna. The formula is:

Power level at IR (dBm) = Output power level (dBm) - Cable loss (dB) + Antenna gain (dBi)

We can convert the output power level of 50 mW to dBm by using the formula:

Power level (dBm) = 10 * log10(Power level (mW))

Therefore, 50 mW = 10 * log10(50) = 16.99 dBm

We can plug in the values into the formula:

Power level at IR (dBm) = 16.99 - 3 + 16 = 29.99 dBm

We can convert the power level at IR from dBm to mW by using the inverse formula:

Power level (mW) = 10^(Power level (dBm) / 10)

Therefore, 29.99 dBm = 10^(29.99 / 10) = 999.96 mW

However, since we need to round off the answer to the nearest integer value, we get:

Power level at IR (mW) = 1000 mW

References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 67; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 57.

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.

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

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 inthe 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 . References: [CWNA-109 Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page 163; [CWNA-109Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page 157.

 The data rate of a signal is the speed that the data bits in individual 802.11 data frames are sent, but it does not account for the actual amount of data that can be transmitted over time. The throughput of a connection is the flow of information over time, which is affected by various factors such as data encoding, modulation, encryption, airtime utilization, noise levels, interference, etc. Therefore, the throughput is always lower than the data rate. According to one of the web search results1, the actual throughput is normally 60-70 percent of the supported data rates. So, for a connection with a data rate of 150 Mbps, the expected throughput would be around 90-105 Mbps.

The feature of 802.11ax (HE) that provides this functionality is OFDMA. OFDMA stands for Orthogonal Frequency Division Multiple Access and is a technology that allows multiple devices to communicate simultaneously on the same channel in the same BSS. OFDMA works by dividing a channel into smaller subchannels called Resource Units (RUs), which are composed of groups of subcarriers or tones. Each RU can be assigned to a different device based on its bandwidth requirement and signal quality. This way, OFDMA can increase the efficiency and capacity of the channel by reducing overhead, contention, and latency. OFDMA can also support both uplink and downlink multi-user transmissions using trigger frames and buffer status reports. 6 GHz support, TWT, and Wi-Fi-LTE are not features of 802.11ax that provide this functionality. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 226; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 216.

 The most effective method for testing roaming in relation to 802.11 VoIP handsets is to place a call with the handset and move around the facility to test quality duringroaming. This method allows you to evaluate the actual performance and user experience of VoIP calls over wireless networks, as well as identify any potential issues such as signal strength, interference, latency, jitter, packet loss, or handoff delays. A spectrum analyzer can only show you the RF activity during a VoIP call, but not how it affects the voice quality or roaming behavior. A protocol analyzer can capture the traffic generated when a laptop roams, but it cannot simulate the characteristics of a VoIP handset such as battery life, antenna design, codec support, or QoS features. A built-in roaming monitor is not a common feature in all VoIP handsets, and it may not provide accurate or comprehensive information about the roaming process. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 487; [Voice over Wireless LAN 4.1 Design Guide], page 6-19.