CWNA-109 Certified Wireless Network Administrator Questions and Answers

A laptop-based spectrum analyzer with a directional antenna is the best solution for locating a non-802.11 device that is suspected of causing interference on the WLAN. A spectrum analyzer is a device or a software application that can measure and display the frequency spectrum of electromagnetic signals in a given range. A spectrum analyzer can show the amplitude, frequency, bandwidth, modulation, and other characteristics of different signals in the spectrum, which can help identify their sources and types. A spectrum analyzer can also detect non-802.11 devices that may cause interference on the WLAN, such as microwave ovens, cordless phones, Bluetooth devices, or radar systems. A laptop-based spectrum analyzer is a software application that runs on a laptop computer and uses an external USB adapter as its RF interface. A laptop-based spectrum analyzer has the advantage of being portable, flexible, and cost-effective compared to a hardware-based spectrum analyzer. A directional antenna is an antenna that radiates or receives RF signals more strongly in one direction than in others. A directional antenna has a high gain and a narrow beamwidth, which means it can focus the RF energy in a specific direction and reduce the interference from other directions. A directional antenna can also increase the range and sensitivity of the RF signal detection. To locate a non-802.11 device that is causing interference on the WLAN, a laptop-based spectrum analyzer with a directional antenna can be used to perform a technique called RF hunting or triangulation. This technique involves pointing the directional antenna in different directions and observing the signal strength and characteristics of the interfering device on the spectrum analyzer. By moving around and changing the direction of the antenna, the location of the interfering device can be estimated based on where the signal strength is highest and most consistent. References: 1, Chapter 7, page 282; 2, Section 4.3

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. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 549; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 519.

What prevents each station from using all the airtime when other client stations are actively communicating in the same BSS is CSMA/CA. CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance and is a media access control method used by WLAN devices to share the wireless medium. CSMA/CA works by having each station sense the medium before transmitting a frame. If the medium is busy (i.e., another station is transmitting), the station defers its transmission until the medium is idle. If the medium is idle, the station waits for a random backoff period before transmitting. This way, CSMA/CA reduces the chances of collisions and ensures fair access to the medium for all stations. CSMA/CA also uses positive acknowledgements to confirm successful transmissions and retransmissions to recover from errors. CSMA/CD, DOS prevention, and OFDMA are not used by WLAN devices in a BSS. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 108; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 98.

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.

Fade Margin is an additional pad of signal strength designed into the RF system to compensate for unpredictable signal fading. It is the difference between the receiver’s sensitivity and the actual received signal level. A higher Fade Margin indicates a more robust link that can withstand interference, attenuation, or other factors that may reduce the signal strength. A lower Fade Margin means that the link is more susceptible to failure or performance degradation. Fade Margin is usually expressed in decibels (dB) and can be calculated by subtracting the receiver sensitivity from the received signal level. References: 1, Chapter 2, page 51; 2, Section 2.1

In wireless communication, several factors influence the effective reception of RF signals, including the receiving station's radio sensitivity, the transmitting station's output power, and free space path loss. However, the receiving station's output power does not influence the distance at which an RF signal can be effectively received. The key factors that impact signal reception distance are:

• Receiving Station's Radio Sensitivity: This refers to the lowest signal strength at which the receiver can process a signal with an acceptableerror rate. Higher sensitivity allows for better reception at greater distances.
• Transmitting Station's Output Power: This is the power with which a transmitter sends out a signal. Higher output power can extend the range of transmission, making it easier for distant receivers to detect the signal.
• Free Space Path Loss (FSPL): FSPL represents the attenuation of radio energy as it travels through free space. It increases with distance and frequency, reducing the signal strength as the distance from the transmitter increases.

The output power of the receiving station is related to how strong a signal it sends out, not how well it can receive or process incoming signals. Therefore, it does not affect the reception distance of incoming RF signals.

References:

• CWNA Certified Wireless Network Administrator Official Study Guide: Exam PW0-105, by David D. Coleman and David A. Westcott.
• RF fundamentals and RF design considerations in wireless communication systems.

In the 2.4 GHz frequency band used for 802.11 wireless networks, the channel bandwidth is typically 20 MHz, but the actual frequency spread of each channel is about 22 MHz due to the modulation techniques used. This spread causes overlap between adjacent channels, which can lead to interference and degrade network performance. To avoid this, it's essential to use non-overlapping channels.

The three non-overlapping channels in the 2.4 GHz band are 1, 6, and 11. Each of these channels is spaced sufficiently apart to avoid interference with each other:

• Channel 1: Centered at 2.412 GHz.
• Channel 6: Centered at 2.437 GHz.
• Channel 11: Centered at 2.462 GHz.

Given the options provided, option C (1 and 5) is the closest to a pair of non-overlapping channels, although in practice, channel 5 would still cause some interference with channel 1 due to the 22 MHz spread. The ideal choice for non-overlapping channels would be any two channels among 1, 6, and 11, but this is not an option provided. Therefore, within the given options, 1 and 5 are the best choice, understanding that in a real-world scenario, 1 and 6 or 6 and 11 would be preferred to avoid overlap.

References:

• CWNA Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109, by David D. Coleman and David A. Westcott.
• Understanding 2.4 GHz channel arrangement and interference patterns in 802.11 wireless networks.

The final step in an effective troubleshooting process is to document the results. Documentation is essential for keeping track of the problem history, the actions taken, the solutions implemented, and the outcomes achieved. Documentation can also help to prevent future problems, improve best practices, and provide feedback for improvement. Documentation should include relevant information such as problem description, symptoms, root cause analysis, resolution steps, verification methods, and lessons learned. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 513; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 483.

Refraction is the bending of an RF signal as it passes through a medium with a different density than free space. This can cause the signal to change its direction and speed, which can affect the accuracy and reliability of wireless communication. Refraction is influenced by factors such as temperature, humidity, and atmospheric pressure12. References: CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 72; CWNA-109Study Guide, Chapter 2: Radio Frequency Fundamentals, page 67.

The fact that is true regarding controllers and APs in a Split MAC architecture is that an IP tunnel is established between the AP and controller for AP management and control functions. A Split MAC architecture is a WLAN architecture where some of the MAC layer functions are performed by the APs (such as encryption, decryption, and frame acknowledgement) and some are performed by the controllers (such as authentication, association, roaming, and QoS). To communicate with each other, the APs and controllers establish an IP tunnel that carries the management and control frames between them. The IP tunnel can use protocols such as Lightweight Access Point Protocol (LWAPP) or Control And Provisioning of Wireless Access Points (CAPWAP). References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 372; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 362.

FT (Fast Transition) is an IEEE 802.11 standard method for fast roaming. FT is defined in the IEEE 802.11r amendment and is also known as Fast BSS Transition (FBT) or Fast Secure Roaming. FT is a feature that allows a client station to quickly switch from one AP to another within the same ESS (Extended Service Set) without having to re-authenticate and re-associate with each AP. This reduces the latency and packet loss that may occur during roaming, thus improving the user experience and maintaining the security of the connection. FT works by using pre-authentication and key caching mechanisms that allow the client station and the APs to exchange security information before the actual roaming occurs. This way, when the client station decides to roam to a new AP, it can use a fast reassociation request and response that contain only a few fields, instead of a full authentication and association exchange that require more time and data. References: 1, Chapter 9, page 367; 2, Section 6.3

https://www.cablinginstall.com/articles/2012/08/cat-6a-vs-cat-5e-poe.html

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

Authenticated and Unassociated. According to one of the web search results1, a STA can be authenticated to multiple APs, but it can only be associated to one AP at a time. Association is the process of establishing a logical link between the STA and the AP, which allows the STA to send and receive data frames through the AP2. Therefore, when a STA has authenticated to an AP-1, but still maintains a connection with another AP-2, it means that the STA is authenticated to both APs, but only associated to AP-2. The state of the STA on AP-1 is authenticated and unassociated, which means that the STA can switch to AP-1 without repeating the authentication process, but it cannot send or receive data frames through AP-1 until it becomes associated.

The BSSID (Basic Service Set Identifier) is typically mapped to an AP’s MAC address if a single BSS is implemented. The BSSID is a unique identifier that distinguishes one BSS from another within the same RF medium. It is usually derived from the MAC address of the AP’s radio interface, but it can also be manually configured or randomly generated by some vendors. The BSSID is used by client stations to associate with an AP and to send and receive frames within a BSS. References: , Chapter 1, page 24; , Section 1.2

Implementing Fast BSS Transition (FT) for roaming is likely to cause the least impact on the application layer throughput of an 802.11n client station in a 2.4 GHz HT BSS. FT is a feature that allows a client station to quickly switch from one AP to another within the same ESS (Extended Service Set) without having to re-authenticate and re-associate with each AP. This reduces the latency and packet loss that may occur during roaming, thus improving the user experience and maintaining the application layer throughput. FT is defined in the IEEE 802.11r amendment and is also known as Fast Roaming or Fast Secure Roaming. References: , Chapter 9, page 367; , Section 6.3

Patch and panel antennas are directional antenna types that are commonly used by indoor Wi-Fi devices in a MIMO multiple spatial stream implementation. These antennas have a flat rectangular shape and can be mounted on walls or ceilings to provide coverage in a specific direction. They have a moderate gain and a relatively wide beamwidth, making them suitable for multipath environments where signals can reflect off different surfaces and create multiple spatial streams. Patch and panel antennas can also support polarization diversity, which means they can transmit and receive both horizontally and vertically polarized waves, increasing the MIMO performance. References: 1, Chapter 2, page 72; 2, Section 2.4

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

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.

The error in administration that could be the cause of this security concern is that HTTP is in use instead of HTTPS. HTTP is an unencrypted protocol that transfers data in plain text over the network. This means that anyone who captures the traffic can see the HTML code of the Web pages used for access point management, as well as any sensitive information such as passwords or configuration settings. HTTPS is an encrypted protocol that uses SSL/TLS to secure the data transmission between the Web browser and the Web server. HTTPS prevents anyone from snooping on or tampering with the Web traffic. Therefore, HTTPS should always be used for Web based management of wireless access points, especially in autonomous mode where there is no centralized controller to enforce security policies. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 431; [HTTP vs HTTPS: What’s The Difference And Why Should You Care?].

DHCP (Dynamic Host Configuration Protocol) is a commonly used method to locate the controllers by the APs in a WLAN that is implemented using wireless 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 APs 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. This way, the APs can discover the wireless controller and establish a connection with it. Alternatively, the APs can also use other methods to locate the wireless controller, such as DNS (Domain Name System), broadcast or multicast discovery, or manual configuration. References: 1, Chapter 8, page 309; 2, Section 5.2

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

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. References: , Chapter 1, page 23; , Section 1.1

OFDM (Orthogonal Frequency Division Multiplexing) is the physical layer specification (PHY) that VHT capable devices must be backward compatible with according to the IEEE 802.11-2012 standard. VHT (Very High Throughput) is aPHY and MAC enhancement that is defined in the IEEE 802.11ac amendment and is also known as Wi-Fi 5. VHT operates only in the 5 GHz band and uses features such as wider channel bandwidths (up to 160 MHz), higher modulation schemes (up to 256-QAM), more spatial streams (up to eight), multi-user MIMO (MU-MIMO), beamforming, and VHT PHY and MAC enhancements. VHT can achieve data rates up to 6.9 Gbps.

According to the IEEE 802.11-2012 standard, VHT capable devices must be backward compatible with devices using OFDM PHY, which is defined in the IEEE 802.11a amendment and is also used by IEEE 802.11g, IEEE 802.11n, and IEEE 802.11h amendments. OFDM operates in both the 2.4 GHz and 5 GHz bands and uses features such as subcarriers, symbols, guard intervals, and OFDM PHY and MAC enhancements. OFDM can achieve data rates up to 54 Mbps.

Backward compatibility means that VHT capable devices can interoperate with OFDM devices on the same network by using common features and parameters that are supported by both PHYs. For example, VHT capable devices can use a channel bandwidth of 20 MHz, a modulation scheme of BPSK, QPSK, or 16-QAM, one spatial stream, no beamforming, and OFDM PHY and MAC headers when communicating with OFDM devices. Backward compatibility also means that VHT capable devices can fall back to OFDMmode when the signal quality or SNR is too low for VHT mode. References: 1, Chapter 3, page 123; 2, Section 3.2

The WLAN feature that would allow the network administrator to control the network resources that can be accessed by each employee based on their department is Role-Based Access Control (RBAC). RBAC is a method of assigning different permissions and policies to users or groups based on their roles in the organization. RBAC can be implemented by using VLANs, ACLs, or firewalls to restrict access to certain network segments or resources. RBAC can also be integrated with 802.1X/EAP authentication to dynamically assign roles and VLANs to users based on their credentials. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 403; [Role-Based Access Control (RBAC) in Wireless Networks], page 1.

 VSWR stands for Voltage Standing Wave Ratio, which is a measure of how well the impedance of the RF cable and connectors matches the impedance of the transmitter and the antenna. Impedance is the opposition to the flow of alternating current in an RF circuit, and it depends on the frequency, resistance, capacitance, and inductance of the components. A perfect impedance match would have a VSWR of 1:1, meaning that all the power is transferred from the transmitter to the antenna, and none is reflected back. However, in reality, there is always some degree of mismatch, which causes some power to be reflected back to the transmitter, creating standing waves along the cable. This reduces the efficiency and performance of the wireless system, and can also damage the transmitter. Excessive VSWR can be caused by using poor quality or damaged cables and connectors, or by using components that have different impedance ratings123. References: CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 90; CWNA-109Study Guide, Chapter 2: Radio Frequency Fundamentals, page 86; CWNP website, CWNA Certification.

 The cipher suite specified by the 802.11-2016 standard and is not deprecated is Counter Mode with CBC-MAC Protocol (CCMP). CCMP is an encryption protocol that uses Advanced Encryption Standard (AES) as the underlying cipher and provides confidentiality, integrity, and origin authentication for wireless data. CCMP is the mandatory encryption protocol for WPA2 and WPA3. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 295; [IEEE Standard for Information technology–Telecommunications and information exchange between systems Local and metropolitan area networks–Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications], page 1560.

An isotropic radiator is a theoretical point source of electromagnetic radiation that radiates equally in all directions. It has no physical dimensions and no preferred direction of radiation. It is used as a reference for antenna gain because it represents the ideal case of a perfect omnidirectional antenna12

Antenna gain is a measure of how well an antenna concentrates its radiated power in a certain direction. It is expressed in decibels (dB) relative to a reference antenna. Whenthe reference antenna is an isotropic radiator, the antenna gain is denoted by dBi, which stands for decibels relative to isotropic12

For example, an antenna with a gain of 3 dBi means that it radiates 3 dB more power in its main direction than an isotropic radiator would. Conversely, an antenna with a gain of -3 dBi means that it radiates 3 dB less power in its main direction than an isotropic radiator would12

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.

MU-MIMO capabilities of the bridges are not a factor considered when calculating the Link Budget for an outdoor point-to-point WLAN bridge link. The Link Budget is acalculation of the expected signal strength at the receiver based on various factors that affect the RF transmission. Some of these factors are operating frequency, transmit power, receive antenna gain, free space path loss, cable loss, connector loss, and environmental loss. MU-MIMO stands for Multi-User Multiple Input Multiple Output, which is a technology that allows multiple devices to communicate simultaneously using multiple spatial streams. MU-MIMO is not relevant for a point-to-point link, where there are only two devices involved. References: 1, Chapter 2, page 59; 2, Section 2.2

The beamwidth of an RF antenna is the angular measure of how wide the main lobe of radiation is. The main lobe is the area where the signal strength is highest and most concentrated. The beamwidth is calculated at the points where the main lobe decreases power by 3 dB, which means it is half of the maximum power. The beamwidth can be measured in both horizontal and vertical planes, depending on how the antenna is oriented. The horizontal beamwidth is also called azimuth, while the vertical beamwidth is also called elevation. The beamwidth patterns on an antenna polar chart indicate how the RF energy is distributed in different directions. References: 1, Chapter 2, page 66; 2, Section 2.3

 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 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.

 This is because the passphrase for WPA2-Personal is case-sensitive and must match exactly on both the AP and the client. If the passphrase is entered incorrectly on the client, the client will not be able to authenticate with the AP and connect to the network. The AP that covers the problem area is not likely to require a firmware update, fail, or be improperly configured, as it is online and works with other clients that have the correct passphrase. To troubleshoot this issue, you can check the passphrase settings on the clients and make sure they matchwith the AP. You can also try to reconnect the clients to the network or reboot them if necessary. For more information on how to configure WPA2-Personal on your router