CWNP CWNA-109 Practice Test - Questions Answers, Page 3

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 acceptable error 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.

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.

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

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

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

Rounding up to the nearest integer, we get23 dBmas the EIRP at the antenna element12.Reference:CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 92;CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 88.

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.Reference:1, Chapter 2, page 51;2, Section 2.1

Passive Gain is the increase of RF energy in an intentional direction with the use of an antenna. It is achieved by focusing the same amount of power into a smaller area, resulting in a higher power density and a stronger signal. Passive Gain does not require any additional power or amplification, but rather depends on the antenna's physical characteristics, such as size, shape, and orientation.Passive Gain is also expressed in decibels (dB) and is related to the antenna's beamwidth and directivity.Reference:1, Chapter 2, page 63;2, Section 2.3

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.Reference:1, Chapter 2, page 72;2, Section 2.4

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.Reference:1, Chapter 2, page 66;2, Section 2.3

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 a calculation 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.Reference:1, Chapter 2, page 59;2, Section 2.2

The inverse square law states that the signal strength of an RF wave is inversely proportional to the square of the distance from the source. This means that as the distance from the transmitter increases, the signal strength decreases rapidly.

Channel 144 is a new channel that was added to the 5 GHz band by the 802.11ac amendment, which defines the VHT (Very High Throughput) PHY for WLANs. Channel 144 has a center frequency of 5720 MHz and a bandwidth of 20 MHz. It can also be combined with adjacent channels to form wider channels of 40 MHz, 80 MHz, or 160 MHz. Channel 144 is available in some regions, such as North America and Europe, but not in others, such as Japan and China .Reference:[CWNA-109 Study Guide], Chapter 3: Antennas and Accessories, page 121; [CWNA-109 Study Guide], Chapter 3: Antennas and Accessories, page 115; [Wikipedia], List of WLAN channels.