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. Reference: , Chapter 3, page 103; , Section 3.1

Return loss is a measure of how well the components of an RF system are matched in terms of their

impedance. Impedance is the opposition to the flow of alternating current in a circuit, and it depends

on the frequency, resistance, capacitance, and inductance of the components. When the impedance

of the source, the transmission line, and the load are not equal, some of the power is reflected back

to the source, causing a loss of forward power. This loss is expressed in decibels (dB) as return loss.

The higher the return loss, the lower the reflection and the better the impedance matching.

Conversely, the lower the return loss, the higher the reflection and the worse the impedance

matching.

VSWR (Voltage Standing Wave Ratio) is another way of expressing the same concept. It is the ratio of

the maximum voltage to the minimum voltage along a transmission line due to the interference of

the incident and reflected waves. A VSWR of 1:1 means that there is no reflection and perfect

impedance matching. A VSWR higher than 1:1 means that there is some reflection and impedance

mismatch. The higher the VSWR, the higher the reflection and the lower the return loss.

Therefore, a significant impedance mismatch between components in an RF system will cause high

reflection, high VSWR, and low return loss.

The two IEEE amendments that should be supported to provide the management frame protection

and fast secure roaming security features are 802.11r and 802.11w12.

802.11r (Fast BSS Transition): This amendment to the IEEE 802.11 standard permits continuous

connectivity aboard wireless devices in motion, with fast and secure client transitions from one Basic

Service Set to another1.

802.11w (Management Frame Protection): This amendment increases the security of its

management frames2.

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. Reference: [CWNP

Certified Wireless Network Administrator Official Study Guide: Exam CWNA-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.

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. Reference: [CWNP Certified

Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 66; [CWNA: Certified

Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 56.

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.

What prevents each station from using all the airtime when other client stations are actively

communicating in the same BSS is CSMA/C

A . 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. Reference: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-

109], page 108; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-

109], page 98.

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

CWNA-109], page 403; [Role-Based Access Control (RBAC) in Wireless Networks], page 1.

802.11 QoS is achieved by giving high priority queues a statistical advantage at winning contention.

802.11 QoS is based on the Enhanced Distributed Channel Access (EDCA) mechanism, which defines

four access categories (ACs) for different types of traffic: Voice, Video, Best Effort, and Background.

Each AC has its own transmit queue and contention parameters, such as Arbitration Interframe

Space (AIFS), Contention Window (CW), and Transmission Opportunity (TXOP). These parameters

determine how long a station has to wait before transmitting a frame and how long it can occupy the

channel. Higher priority ACs have shorter AIFS, smaller CW, and longer TXOP, which means they have

more chances to access the channel and send more data than lower priority ACs. However, this does

not guarantee that higher priority ACs will always win the contention, as there is still a random

backoff process involved. Therefore, 802.11 QoS is a statistical service that provides different levels

of service quality based on traffic categories. Reference: , Chapter 10, page 403; , Section 6.1

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. Reference: 1, Chapter

2, page 72; 2, Section 2.4