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Question 21.

Which RF measurement represents the power level of a received wireless signal as observed by a receiver?

1. RSSI
   2. EIRP
   3. Antenna gain
   4. Frequency deviation

Correct Answer: 1. RSSI

Explanation:

Received Signal Strength Indicator, or RSSI, represents the strength of a received radio signal as measured by the receiving device. Vendors may represent RSSI differently, so the exact scale is not always directly comparable across different client chipsets or devices. RSSI is useful for evaluating whether a client has adequate signal strength, but it should not be considered in isolation. Noise, interference, retry rates, data rates, and SNR also affect WLAN performance. EIRP represents effective transmitted power, while antenna gain describes how an antenna concentrates RF energy. A strong RSSI with a high noise floor can still result in poor performance because the receiver may struggle to distinguish the desired signal.

Question 22.

Which value is calculated by subtracting the noise floor from the received signal strength?

1. EIRP
   2. SNR
   3. dBi
   4. VSWR

Correct Answer: 2. SNR

Explanation:

Signal-to-noise ratio, or SNR, is commonly determined by comparing the desired received signal level with the surrounding noise floor. For example, if a signal is received at -60 dBm and the noise floor is -90 dBm, the SNR is approximately 30 dB. A higher SNR generally gives the receiver a better chance of decoding more complex modulation schemes and maintaining reliable communication. EIRP relates to transmitted power, dBi measures antenna gain relative to an isotropic radiator, and VSWR concerns impedance matching in RF systems. SNR is therefore one of the most useful measurements when assessing whether a wireless client has sufficient signal quality rather than merely sufficient signal strength.

Question 23.

Which term describes the total effective RF power radiated by a transmitter after accounting for transmit power, cable loss, and antenna gain?

1. RSSI
   2. Noise floor
   3. EIRP
   4. SNR

Correct Answer: 3. EIRP

Explanation:

Effective Isotropic Radiated Power, or EIRP, represents the effective RF power radiated in the direction of maximum antenna gain after considering transmitter output power, cable or connector losses, and antenna gain. A simplified link-budget expression is transmitter power minus system losses plus antenna gain. Regulatory authorities may impose EIRP limits in particular frequency bands, so WLAN designers must understand how antenna gain and transmitter settings affect legal operation. RSSI and SNR describe received signal conditions, while the noise floor represents background RF energy. EIRP is particularly important when designing outdoor links, using external antennas, or configuring access points close to regulatory transmit-power limits.

Question 24.

Which statement correctly describes a 3 dB increase in RF power?

1. Power decreases by about half
   2. Power increases tenfold
   3. Power is unchanged
   4. Power approximately doubles

Correct Answer: 4. Power approximately doubles

Explanation:

An increase of approximately 3 dB corresponds to roughly twice the RF power. Likewise, a decrease of about 3 dB represents approximately half the power. WLAN professionals often use this Rule of 3s together with the Rule of 10s for quick calculations. A 10 dB increase represents ten times the power, while a 10 dB decrease represents one-tenth. These logarithmic shortcuts help with link budgets, antenna changes, transmit-power adjustments, and cable-loss calculations. It is important to remember that doubling transmit power does not double communication distance because RF propagation and usable coverage depend on many additional factors, including path loss, antenna patterns, receive sensitivity, interference, and environmental conditions.

Question 25.

Which phenomenon describes multiple copies of the same RF signal arriving at a receiver at different times because they traveled along different paths?

1. Multipath
   2. Absorption
   3. Polarization
   4. Amplification

Correct Answer: 1. Multipath

Explanation:

Multipath occurs when RF energy reaches a receiver through multiple propagation paths. Reflections, diffraction, and scattering can cause different copies of the same transmission to arrive at slightly different times and phases. Historically, multipath could contribute to intersymbol interference and poor reception, but modern WLAN technologies such as MIMO can exploit multipath under suitable conditions to improve performance. Absorption removes energy from a wave, polarization describes antenna and wave orientation, and amplification increases signal magnitude. Understanding multipath is important because indoor WLAN environments often contain many reflective surfaces, including walls, metal structures, furniture, glass, and machinery that create numerous propagation paths between access points and clients.

Question 26.

Which RF behavior occurs when part of a wireless signal is absorbed by a material and converted into another form of energy, such as heat?

1. Reflection
   2. Absorption
   3. Diffraction
   4. Refraction

Correct Answer: 2. Absorption

Explanation:

Absorption occurs when RF energy passes into a material and some of that electromagnetic energy is converted into another form, commonly heat. Materials containing significant water content can absorb RF energy effectively, which is one reason people and certain building materials can affect Wi-Fi propagation. Reflection redirects signal energy, diffraction bends energy around obstacles, and refraction changes wave direction as it moves between propagation media. Absorption contributes to attenuation and can create coverage loss behind walls, floors, shelving, people, and other obstacles. Site surveys should therefore consider actual environmental materials rather than relying only on open-space distance calculations when predicting coverage and access point placement.

Question 27.

Which 802.11 management frame is periodically transmitted by an access point to advertise information about a wireless network?

1. ACK
   2. RTS
   3. Beacon
   4. CTS

Correct Answer: 3. Beacon

Explanation:

Beacon frames are 802.11 management frames transmitted periodically by access points to advertise the existence and characteristics of a Basic Service Set. They can contain information about the SSID, supported rates, capabilities, timing, security-related parameters, and other WLAN characteristics. ACK, RTS, and CTS are control frames rather than management frames. Clients use beacon information during scanning and network selection. Because beacons are transmitted regularly and consume airtime at a basic data rate, excessive SSIDs can increase management-frame overhead. WLAN designers should therefore avoid unnecessarily advertising large numbers of SSIDs because each additional BSS contributes periodic beacon traffic and other management overhead on the channel.

Question 28.

Which 802.11 management frame does a client transmit during active scanning to discover nearby wireless networks?

1. Association Response
   2. Deauthentication
   3. Beacon
   4. Probe Request

Correct Answer: 4. Probe Request

Explanation:

During active scanning, a client transmits Probe Request management frames in an attempt to discover nearby WLANs. Access points that satisfy the request may respond with Probe Response frames containing information about their BSS capabilities. Passive scanning, by contrast, involves listening for Beacon frames without actively transmitting discovery requests. Association Response and Deauthentication frames serve different management purposes. Understanding active and passive scanning is important because client scanning behavior affects roaming speed, channel discovery, battery consumption, and airtime utilization. Regulatory requirements can also influence whether active probing is allowed on specific channels, particularly in bands where dynamic frequency selection or other spectrum rules apply.

Question 29.

Which 802.11 management frame is normally sent by an access point in response to a valid client Probe Request?

1. Probe Response
   2. ACK
   3. RTS
   4. Block ACK

Correct Answer: 1. Probe Response

Explanation:

A Probe Response is a management frame transmitted by an access point in response to an applicable Probe Request from a client during active scanning. It contains information similar to that found in Beacon frames, allowing the client to evaluate the WLAN’s capabilities and decide whether to continue with authentication and association. ACK, RTS, and Block ACK are control-related mechanisms serving different purposes. Probe traffic is part of normal discovery behavior, but large numbers of clients repeatedly probing can add management overhead. WLAN professionals should understand probe behavior when analyzing packet captures or troubleshooting situations where clients fail to discover or select expected access points.

Question 30.

Which 802.11 process creates the logical relationship that allows a client station to become a member of an infrastructure BSS?

1. Encryption
   2. Association
   3. Fragmentation
   4. Aggregation

Correct Answer: 2. Association

Explanation:

Association establishes the logical relationship between a client station and an access point within an infrastructure BSS. Before normal data communication occurs, the client discovers the WLAN, performs required authentication procedures, and then requests association. The access point can respond by accepting or rejecting that request. Encryption protects data confidentiality, fragmentation divides frames into smaller pieces, and aggregation combines multiple frames or payloads for efficiency. Association status is important because an access point must track which clients are currently members of its BSS. When troubleshooting connectivity, packet analysis often examines Authentication, Association Request, and Association Response frames to determine exactly where a client connection process is failing.

Question 31.

Which term describes a group of two or more infrastructure BSSs connected through a distribution system and typically providing a common WLAN service?

1. IBSS
   2. BSSID
   3. ESS
   4. PHY

Correct Answer: 3. ESS

Explanation:

An Extended Service Set, or ESS, consists of multiple infrastructure BSSs connected through a distribution system. The BSSs typically advertise the same SSID and security settings so users can move throughout a larger coverage area while remaining on the same logical WLAN. A BSSID identifies a specific BSS, while an IBSS describes an older ad hoc peer-to-peer wireless topology. PHY refers to physical-layer technologies rather than a WLAN topology. Understanding the ESS concept is important for enterprise deployments because most corporate WLANs consist of many access points working together to provide continuous service across offices, campuses, warehouses, hospitals, schools, or other large environments.

Question 32.

Which device usually makes the decision to roam from one access point to another in an IEEE 802.11 WLAN?

1. Ethernet switch
   2. Client station
   3. DNS server
   4. DHCP server

Correct Answer: 2. Client station

Explanation:

In traditional IEEE 802.11 operation, the client station generally decides when and where to roam. Infrastructure features can provide information or assistance, but the client’s driver and roaming algorithms ultimately determine when the current connection is no longer preferred and which candidate access point should be selected. DHCP and DNS servers do not make radio roaming decisions, and Ethernet switches do not directly decide which AP a client associates with. Different client devices can behave very differently because vendors use different thresholds and roaming algorithms. This is why WLAN validation should include representative client devices rather than assuming all clients will roam identically under the same RF conditions.

Question 33.

Which 802.11 amendment introduced mechanisms such as BSS transition management that can help clients make better roaming decisions?

1. 802.11v
   2. 802.11b
   3. 802.11a
   4. 802.11d

Correct Answer: 1. 802.11v

Explanation:

IEEE 802.11v introduced wireless network management enhancements, including mechanisms such as BSS Transition Management. These features can allow network infrastructure to provide clients with information or recommendations about alternative BSSs, helping capable clients make more informed roaming decisions. The client still ultimately decides whether to roam. 802.11b and 802.11a define earlier PHY technologies, while 802.11d addressed regulatory-domain information. WLAN professionals often encounter 802.11v together with 802.11k and 802.11r when discussing enterprise roaming optimization. Support varies by client, so these mechanisms should be tested with the actual device population rather than assumed to function identically across all endpoints.

Question 34.

Which 802.11 amendment provides radio resource measurement capabilities that can help clients learn about neighboring access points?

1. 802.11i
   2. 802.11k
   3. 802.11w
   4. 802.11e

Correct Answer: 2. 802.11k

Explanation:

IEEE 802.11k provides radio resource measurement capabilities that can help clients gather information about the WLAN environment, including neighboring access points. Neighbor-related information can reduce the amount of time a client spends scanning every possible channel during roaming. 802.11i is associated with enhanced WLAN security, 802.11w introduced protection for selected management frames and was later incorporated into the base standard, and 802.11e introduced quality-of-service enhancements. In enterprise WLAN design, 802.11k is commonly discussed alongside 802.11r and 802.11v because the three technologies can collectively improve aspects of roaming and client decision-making when both infrastructure and clients support them.

Question 35.

Which 802.11 amendment introduced Fast BSS Transition to reduce authentication delay during roaming?

1. 802.11k
   2. 802.11v
   3. 802.11r
   4. 802.11h

Correct Answer: 3. 802.11r

Explanation:

IEEE 802.11r introduced Fast BSS Transition, commonly known as FT, to reduce the delay involved in moving between access points within an ESS. It is particularly useful for latency-sensitive applications such as voice because lengthy authentication during a roam can cause noticeable interruptions. 802.11k provides radio resource measurement capabilities, while 802.11v includes network-management enhancements such as BSS Transition Management. 802.11h introduced mechanisms related to spectrum management in certain bands. Client compatibility should always be verified before enabling roaming enhancements because some older or poorly implemented clients may have interoperability issues with features they do not fully support.

Question 36.

Which Wi-Fi quality-of-service mechanism provides differentiated access categories for traffic such as voice, video, best effort, and background?

1. WPA2
   2. DFS
   3. MIMO
   4. WMM

Correct Answer: 4. WMM

Explanation:

Wi-Fi Multimedia, or WMM, is a Wi-Fi Alliance certification based on 802.11e quality-of-service mechanisms. It defines access categories for voice, video, best effort, and background traffic. These categories receive different contention parameters so higher-priority traffic such as voice can generally gain access to the medium more quickly than lower-priority traffic. WPA2 is a security technology, DFS relates to radar avoidance in certain 5 GHz channels, and MIMO uses multiple antennas or spatial streams. WMM does not guarantee unlimited bandwidth, because Wi-Fi remains a shared medium, but it helps prioritize delay-sensitive traffic when multiple traffic classes are competing for airtime.

Question 37.

Which WMM access category generally receives the highest medium-access priority?

1. Voice
   2. Background
   3. Best effort
   4. Video

Correct Answer: 1. Voice

Explanation:

The WMM Voice access category generally receives the most favorable contention parameters because voice traffic is highly sensitive to delay, jitter, and packet loss. Video also receives elevated priority, while best-effort and background traffic receive less aggressive contention settings. WMM does not reserve a fixed portion of bandwidth for voice; instead, it changes how different traffic categories compete for medium access. Proper end-to-end quality of service also requires consistent traffic classification and treatment across the wired and wireless infrastructure. Simply enabling WMM cannot compensate for poor RF design, excessive contention, insufficient capacity, or improper application marking elsewhere in the network.

Question 38.

Which 802.11 mechanism allows a transmitter to combine multiple MAC protocol data units into a single larger transmission to reduce overhead?

1. Fragmentation
   2. A-MPDU aggregation
   3. Deauthentication
   4. Probe scanning

Correct Answer: 2. A-MPDU aggregation

Explanation:

A-MPDU aggregation combines multiple MAC Protocol Data Units into a larger transmission, reducing the amount of channel-access and PHY overhead required for each individual data unit. This can improve WLAN efficiency and throughput, particularly at higher PHY rates where overhead becomes a significant portion of airtime consumption. Fragmentation does the opposite by dividing data into smaller pieces, while deauthentication and probing are management processes unrelated to aggregation. Block acknowledgment is often associated with aggregated transmissions because it enables efficient acknowledgment of multiple MPDUs. Understanding aggregation is important when analyzing throughput because advertised PHY rates are always higher than actual application throughput due to protocol overhead.

Question 39.

Which acknowledgment mechanism is commonly used to efficiently acknowledge multiple frames instead of sending a separate ACK for every individual MPDU?

1. Block ACK
   2. Probe Response
   3. CTS-to-Self only
   4. Beacon acknowledgment

Correct Answer: 1. Block ACK

Explanation:

Block acknowledgment allows a receiver to acknowledge multiple MPDUs using a more efficient acknowledgment mechanism rather than transmitting a separate ACK after every individual frame. This works well with frame aggregation and helps reduce overhead, improving WLAN efficiency. Probe Responses are management frames used during active scanning, CTS-to-Self is a protection mechanism, and Beacons are not acknowledged in normal operation. Since wireless medium access itself consumes time, reducing the number of separate contention and acknowledgment exchanges can significantly increase useful throughput. Block ACK behavior is therefore an important part of modern high-throughput 802.11 operation.

Question 40.

Which approach is most appropriate when validating whether a newly installed voice-over-Wi-Fi network meets its design goals?

1. Verify only that every access point is powered on
   2. Check only the wired switch port speed
   3. Assume strong RSSI automatically guarantees good voice quality
   4. Perform an on-site validation using representative voice clients and measure coverage, SNR, roaming, loss, latency, and capacity-related behavior**

Correct Answer: 4. Perform an on-site validation using representative voice clients and measure coverage, SNR, roaming, loss, latency, and capacity-related behavior

Explanation:

Voice-over-Wi-Fi depends on more than basic AP availability or received signal strength. A useful post-deployment validation should use representative client devices and assess the metrics that matter to the application, including coverage, SNR, roaming behavior, packet loss, latency, jitter, contention, and capacity. Client behavior matters because roaming thresholds and feature support vary among device models. Strong RSSI alone cannot reveal interference, high channel utilization, poor SNR, or excessive retries. Validation should therefore test the actual deployed environment and compare measured results with the original WLAN requirements. This provides meaningful evidence that the design supports real-time voice rather than simply providing basic wireless connectivity.