更新された2026年03月27日検証済み！CWNA-109問題集と解答で100%合格できる
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質問 # 52
What can an impedance mismatch in the RF cables and connectors cause?
- A. Increased amplitude of the RF signal
- B. Fewer MCS values in the MCS table
- C. Excessive VSWR
- D. Increased range of the RF signal
正解：C
解説：
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-109 Study Guide, Chapter 2:
Radio Frequency Fundamentals, page 86; CWNP website, CWNA Certification.
質問 # 53
You manage a WLAN with 100 802.11ac access points. All access points are configured to use 80 MHz channels. In a particular BSS, only 40 MHz communications are seen. What is the likely cause of this behavior?
- A. All clients implement single spatial stream radios
- B. The clients are all 802.11n STAs or lower
- C. The short guard interval is also enabled
- D. The AP is improperly configured to use only 40 MHz of the 80 MHz allocated bandwidth
正解：B
解説：
https://7signal.com/802-11ac-migration-part-2-whats-nobodys-telling-you-about-80mhz-and-160mhz-channel- bonding The clients are all 802.11n STAs or lower is the likely cause of this behavior. If a WLAN with 100 802.11ac access points is configured to use 80 MHz channels, but only 40 MHz communications are seen in a particular BSS, it means that the clients in that BSS do not support 80 MHz channels. This could be because they are using older standards, such as 802.11n or lower, that do not support 80 MHz channels. Alternatively, they could be using newer standards, such as 802.11ac or ax, but have their channel width settings limited to 40 MHz or lower due to device capabilities or configuration options. In either case, the AP will adapt to the client's channel width and use only 40 MHz of the 80 MHz allocated bandwidth to communicate with them.
This will reduce the potential throughput and efficiency of the WLAN. References: , Chapter 3, page 111; , Section 3.2
質問 # 54
When implementing PoE, what role is played by a switch?
- A. PD
- B. PSE
- C. Power splitter
- D. Midspan injector
正解：B
解説：
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.
質問 # 55
What is required when operating 802.11ax APS in the 6 GHz band using passphrase-based authentication?
* VHT PHY
- A. HT PHY
- B. CCMP
- C. SAE
正解：B
解説：
SAE (Simultaneous Authentication of Equals) is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication. SAE is a secure and robust authentication method that is defined in the IEEE 802.11s amendment and is also known as WPA3-Personal or WPA3-SAE. SAE is based on a cryptographic technique called Dragonfly Key Exchange, which allows two parties to establish a shared secret key using a passphrase, without revealing the passphrase or the key to an eavesdropper or an attacker. SAE also provides forward secrecy, which means that if the passphrase or the key is compromised in the future, it does not affect the security of past communications.
SAE is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication because of the new regulations and standards that apply to this band. The 6 GHz band is a new frequency band that was opened for unlicensed use by the FCC and other regulatory bodies in 2020. The 6 GHz band offers more spectrum and less interference than the existing 2.4 GHz and 5 GHz bands, which can enable higher performance and efficiency for Wi-Fi devices. However, the 6 GHz band also has some restrictions and requirements that are different from the other bands, such as:
* The 6 GHz band is divided into two sub-bands: U-NII-5 (5925-6425 MHz) and U-NII-7 (6525-6875 MHz). The U-NII-5 sub-band is subject to DFS (Dynamic Frequency Selection) rules, which require Wi-Fi devices to monitor and avoid using channels that are occupied by radar systems or other primary users. The U-NII-7 sub-band is not subject to DFS rules, but it has a lower maximum transmit power limit than the U-NII-5 sub-band.
* The Wi-Fi devices that operate in the 6 GHz band are called 6E devices, which stands for Extended Spectrum. 6E devices must support 802.11ax technology, which is also known as Wi-Fi 6 or High Efficiency (HE). 802.11ax is a new standard that improves the performance and efficiency of Wi-Fi networks by using features such as OFDMA (Orthogonal Frequency Division Multiple Access), MU-MIMO (Multi-User Multiple Input Multiple Output), BSS Coloring, TWT (Target Wake Time), and HE PHY and MAC enhancements.
* The 6E devices that operate in the 6 GHz band must also support WPA3 security, which is a new security protocol that replaces WPA2 and provides stronger encryption and authentication for Wi-Fi networks. WPA3 has two modes: WPA3-Personal and WPA3-Enterprise. WPA3-Personal uses SAE as its authentication method, which requires a passphrase to establish a secure connection between two devices. WPA3-Enterprise uses EAP (Extensible Authentication Protocol) as its authentication method, which requires a certificate or a credential to authenticate with a server.
Therefore, SAE is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication because it is part of WPA3-Personal security, which is mandatory for 6E devices in this band.
References: , Chapter 3, page 120; , Section 3.2
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質問 # 56
Which IEEE 802.11 physical layer (PHY) specification includes support for operation in the 2.4 GHz, 5 GHz, and 6 GHz bands?
- A. HE (802.11ax)
- B. HR/DSSS (802.11b)
- C. VHT (802.11ac).
- D. HT(802.11n)
正解：A
解説：
The IEEE 802.11ax standard, also known as High-Efficiency Wireless (HEW) or simply HE, includes support for operation across multiple frequency bands: 2.4 GHz, 5 GHz, and, with the appropriate regulatory approvals, the 6 GHz band. This makes option D the correct answer. Here's how it compares to the other options:
* HE (802.11ax): Introduced as an enhancement over previous standards, 802.11ax is designed to improve efficiency, especially in dense environments. It supports operation in the 2.4 GHz, 5 GHz, and
6 GHz bands (the latter pending regulatory approval in various regions), making it highly versatile and future-proof.
* VHT (802.11ac): Very High Throughput, or 802.11ac, operates exclusively in the 5 GHz band. It introduced significant speed improvements over its predecessor (802.11n) but does not support the 2.4 GHz or 6 GHz bands.
* HT (802.11n): High Throughput, or 802.11n, supports operation in both the 2.4 GHz and 5 GHz bands.
However, it does not include support for the 6 GHz band.
* HR/DSSS (802.11b): High-Rate Direct Sequence Spread Spectrum, or 802.11b, operates only in the 2.4 GHz band. It was one of the early Wi-Fi standards and does not support 5 GHz or 6 GHz bands.
Given these distinctions, only 802.11ax (option D) supports operation across all three mentioned bands, aligning with the requirements stated in the question.
References:
* IEEE 802.11ax-2021: High-Efficiency Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.
* Understanding the 802.11ax (Wi-Fi 6) standard and its implications for modern wireless networking.
質問 # 57
You are reconfiguring an AP to use the short guard interval. How long will the new guard interval duration be after the change?
- A. 10 ms
- B. 800 ns
- C. 400 ns
- D. 104 ms
正解：C
解説：
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.
質問 # 58
An IEEE 802.11 amendment is in the daft state. What impact does this draft amendment have on the 802.11 standard?
- A. No impact: Draft amendments do not become part of the standard until a working group is formed.
- B. Devices will be released based on the draft amendment and the draft amendment features are part of the standard.
- C. The standard is changed to reflect the new capabilities as soon as an amendment enters the draft stage.
- D. No impact: Until an amendment is ratified, it does not become part of the standard.
正解：D
解説：
An IEEE 802.11 amendment is a proposed change or addition to the existing 802.11 standard, which defines the specifications and protocols for wireless LANs. An amendment goes through several stages of development, such as draft, sponsor ballot, and final approval, before it is ratified by the IEEE Standards Association and becomes part of the standard. Until then, it has no official impact on the standard, although some vendors may release products based on draft amendments to gain a competitive edge or to influence the final outcome of the amendment . References: [CWNA-109 Study Guide], Chapter 1: Overview of Wireless Standards, Organizations, and Fundamentals, page 25; [CWNA-109Study Guide], Chapter 1: Overview of Wireless Standards, Organizations, and Fundamentals, page 23; [IEEE website], IEEE-SA Standards Development Process.
質問 # 59
What security option for 802.11 networks supports SAE and requires protected management frames?
* WPA
- A. WPA2
- B. OWE
- C. WPA3
正解：B
解説：
The security option for 802.11 networks that supports SAE and requires protected management frames is WPA3. WPA3 stands for Wi-Fi Protected Access version 3 and is the latest security standard for WLANs.
WPA3 supports two modes: WPA3-Personal and WPA3-Enterprise. WPA3-Personal uses Simultaneous Authentication of Equals (SAE) as the key exchange protocol, which provides stronger protection against offline dictionary attacks and password guessing than WPA2-Personal. WPA3 also requires protected management frames, which are encrypted frames that prevent spoofing, replay, or denial-of-service attacks on management frames such as deauthentication or disassociation frames. WPA, WPA2, and OWE do not support SAE or require protected management frames. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 307; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 297.
質問 # 60
Three access points are used within a facility. One access point is on channel 11 and the other two are on channel 1. The two access points using channel 1 are on either side of the access point using channel 11 and sufficiently apart so that they do not interfere with each other when they transmit frames. Assuming no other APs are in the vicinity, is CCI still a possibility in this network and why?
- A. No, because CCI only occurs in the 5 GHz frequency band.
- B. Yes, because the client devices connected to one of the channel 1 APs will transmit frames that reach the other channel 1 AP as well as clients connected to the other channel 1 AP.
- C. No, because the APs are far enough apart that no CCI will occur.
- D. Yes, because channel 11 loops around and causes CCI with channel 1.
正解：B
解説：
CCI is still a possibility in this network because the client devices connected to one of the channel 1 APs will transmit frames that reach the other channel 1 AP as well as clients connected to the other channel 1 AP. CCI stands for co-channel interference, which is a type of interference that occurs when two or more devices transmit on the same channel within range of each other. CCI reduces performance and capacity because it causes contention and collisions on the wireless medium, which leads to retransmissions and delays. CCI can be mitigated by increasing physical separation between devices using the same channel or by reducing transmit power levels to limit coverage area. In this scenario, three access points are used within a facility.
One access point is on channel 11 and the other two are on channel 1. The two access points using channel 1 are on either side of the access point using channel 11 and sufficiently apart so that they do not interfere with each other when they transmit frames. However, this does not prevent CCI from occurring between their client devices that are connected on channel 1. For example, if a client device connected to one of the channel
1 APs sends a frame to another device on the wired network or on another wireless network (such as an Internet server or a VoIP phone), that frame will be heard by both channel 1 APs as well as any other client devices connected to either of them on channel 1. This will cause CCI because these devices will have to wait for the channel to be clear before they can transmit their own frames. The answer that CCI only occurs in the
5 GHz frequency band is incorrect; CCI can occur in any frequency band where devices use the same channel.
The answer that channel 11 loops around and causes CCI with channel 1 is also incorrect; channel 11 does not loop around and it operates in a different frequency band than channel 1. References: CWNA-109 Study Guide, Chapter 5: Radio Frequency Signal and Antenna Concepts, page 147
質問 # 61
The requirements for a WLAN you are installing state that it must support unidirectional delays of less than
150 ms and the signal strength at all receivers can be no lower than -67 dBm. What application is likely used that demands these requirements?
- A. RTLS
- B. FTP
- C. VoIP
- D. E-Mail
正解：C
解説：
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
質問 # 62
You are troubleshooting a client issue on a Windows laptop. The laptop can see and connect to 2.4 GHz APs, but is does not even see 5 GHz APs. While evaluating the issue, you determine that this problem is happening for all of the laptops of this model in the organization. Several other tablets connect on channel 48 and channel
52 in the same work areas. What is the likely problem?
- A. The clients are configured to use WPA and 5 GHz channels only support WPA2.
- B. The antennas in the laptop have insufficient gain to detect the 5 GHz signals.
- C. The access points are configured to disallow 5 GHz.
- D. The client drivers are faulty and should be upgraded.
正解：D
解説：
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
質問 # 63
What factor 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?
- A. Implementing Fast BSS Transition (FT) for roaming
- B. RF interference from more than 10 nearby Bluetooth transmitters
- C. Increasing or decreasing the number of spatial streams in use by the client station and AP
- D. Implementation of several other clients in the same BSS using 802.11g radios
正解：A
解説：
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
質問 # 64
Your manager asked you to locate a solution that allows for centralized monitoring of WLAN performance over time. He wants a single pane of glass for administration and monitoring of the solution. What do you recommend?
- A. AP-based spectrum analysis
- B. Laptop-based spectrum analyzers
- C. Overlay WLAN monitoring solution
- D. Laptop-based protocol analyzers
正解：C
解説：
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: Exam CWNA-
109], page 538; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-
109], page 508.
質問 # 65
An RF signal sometimes bends as it passes through a material rather than around an obstacle. What is the RF behavior that this statement best describes?
- A. Scattering
- B. Reflection
- C. Diffraction
- D. Refraction
正解：D
解説：
Refraction is the bending of an RF signal as it passes through a material of different density. Refraction can cause the signal to change its direction and angle of arrival. For example, when a light beam passes from air to water, it bends because of the difference in the refractive index of the two mediums. Similarly, when an RF signal passes from one medium to another, such as from air to glass, it can bend due to the change in the dielectric constant of the materials12. References: 1:CWNA-109Official Study Guide, page 67 2: Refraction
質問 # 66
What statement is true concerning the use of Orthogonal Frequency Division Multiplexing (OFDM) modulation method in IEEE 802.11 WLANs?
- A. OFDM was used by Frequency Hopping Spread Spectrum (FHSS) PHY devices.
- B. OFDM modulation is used only in 5 GHz 802.11 transmissions.
- C. OFDM implements BPSK modulation to allow for data rates up to 7 Gbps.
- D. OFDM was first introduced in 802.11a and is used by the ERP, HT and VHT PHYs as well.
正解：D
解説：
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 . References: [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.
質問 # 67
In a long-distance RF link, what statement about Fade Margin is true?
- A. The Fade Margin of a long-distance radio link should be equivalent to the receiver's low noise filter gain.
- B. A Fade Margin is unnecessary on a long-distance RF link if more than 80% of the first Fresnel zone is clear of obstructions.
- C. Fade Margin is an additional pad of signal strength designed into the RF system to compensate for unpredictable signal fading.
- D. The Fade Margin is a measurement of signal loss through free space and is a function of frequency and distance.
正解：C
解説：
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
質問 # 68
You are implementing a multi-AP WLAN and fast secure roaming is essential. Which one of the following methods is an IEEE 802.11 standard method for fast roaming?
- A. Band steering
- B. OKC
- C. Load balancing
- D. FT
正解：D
解説：
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
質問 # 69
When replacing the antenna of a WLAN device with a similar antenna type that has a higher passive gain, what antenna characteristic will decrease?
- A. Range
- B. Active gain
- C. Beamwidth
- D. Receive sensitivity
正解：C
解説：
According to the CWNA Official Study Guide (CWNA-109), Chapter 4: Antennas and Accessories, antenna gain is a measure of how effectively an antenna focuses energy in a particular direction. When a passive antenna with a higher gain is used, it does not increase the transmitted power - instead, it focuses the RF energy more narrowly, creating a stronger signal in a smaller area.
"As the gain of an antenna increases, the beamwidth of the antenna decreases. This is because a higher gain antenna focuses energy more narrowly in one direction. While this increases range in that direction, it reduces coverage in other directions."
- CWNA-108 Study Guide, Chapter 4, Antenna Concepts and Beamwidth, p. 165-166 Thus, when you replace an antenna with one of higher passive gain, the beamwidth decreases while range in the direction of focus increases.
質問 # 70
An 802.11 WLAN transmitter that emits a 50 mW signal is connected to a cable with 3 dB of loss. The cable is connected to an antenna with 16 dBi of gain. What is the power level at the Intentional Radiator?
- A. 1000 mW
- B. 25 mW
- C. 500 mW
- D. 250 mW
正解：A
質問 # 71
Which directional antenna types are commonly used by indoor Wi-Fi devices in a MIMO multiple spatial stream implementation?
- A. Dipole and yagi
- B. Patch and panel
- C. Dish and grid
- D. Grid and sector
正解：B
解説：
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
質問 # 72
The center frequency of channel 1 in the 2.4 GHz band is 2.412 GHz (2412 MHz). What is the center frequency of channel 4?
- A. 2.422
- B. 2.417
- C. 2.413
- D. 2.427
正解：D
解説：
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
質問 # 73
A client STA must choose the best AP for connectivity. As part of the evaluation, it must verify compatible data rates. What can the client STA use to verify that an AP supports the same data rates that it supports?
- A. Data frames sent between the AP and current clients STAs
- B. Probe request frames transmitted by other client STAs
- C. Beacon frames transmitted by the AP
- D. Authentication frames transmitted by the other client STAs
正解：C
解説：
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.
質問 # 74
What authentication method is referenced in the 802.11-2016 and 802.11-2020 specifications and is recommended for robust WI-AN client security?
- A. 802.1X/EAP
- B. IPSec
- C. WEP
- D. SSL
正解：A
解説：
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. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 299; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 289.
質問 # 75
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