Eliminate Risk of Failure with CWNP CWNA-109 Exam Dumps

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.

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.

OFDMA is a new modulation scheme introduced in 802.11ax that allows multiple users to share the same channel by dividing it into smaller subchannels called resource units (RUs). This improves the efficiency and capacity of the WLAN by reducing contention and overhead. However, to use OFDMA, both the AP and the client must support 802.11ax and negotiate the parameters of the subchannel allocation.Therefore, the customer needs to upgrade the clients that require OFDMA to 802.11ax devices12.

The other options are not correct because they do not reflect the reality of OFDMA.Option B is incorrect because OFDMA is a mandatory feature of 802.11ax for both downlink and uplink transmissions, and all 802.11ax APs must support it1. Option C is incorrect because OFDM and OFDMA are different modulation schemes, and OFDM does not allow multiple users to share the same channel.Option D is incorrect because 802.11ac devices cannot support OFDMA through driver upgrades, as they lack the hardware and firmware capabilities to do so2.

The scenario described suggests that while the Access Point (AP) is capable of 802.11ax (Wi-Fi 6) with four spatial streams, the clients are only achieving data rates typical of 802.11n (Wi-Fi 4) devices, which indicates that the clients are likely 802.11n devices. Here's why this is the most plausible explanation:

802.11n Limitations: Devices that adhere to the 802.11n standard have lower maximum data rates compared to 802.11ax devices due to differences in technology such as modulation, spatial streams, and channel bandwidth. An 802.11n device with a single spatial stream operating on a 20 MHz channel can achieve a maximum data rate of 72.2 Mbps. Even with two spatial streams under ideal conditions, this would only double to approximately 144.4 Mbps, which is close to the 150 Mbps mentioned.

Spatial Stream Capability: The fact that the AP supports four spatial streams suggests it can achieve much higher data rates with 802.11ax clients that also support multiple spatial streams. However, if the clients are 802.11n devices, they may not be capable of using more than two spatial streams, and many earlier 802.11n devices were limited to just one.

The other options are less likely to be the primary cause based on the information provided:

B . Two Stream 802.11ax Clients: If the clients were 802.11ax with only two spatial streams, they would likely achieve higher data rates than 150 Mbps due to the efficiency improvements in 802.11ax.

C . Contention and D. Non-Wi-Fi Interference: While these could affect performance, they would not inherently limit clients to 150 Mbps, especially in the context of an 802.11ax environment where mechanisms to handle interference and contention are more advanced.

IEEE 802.11n-2009: Enhancements for Higher Throughput.

CWNA Certified Wireless Network Administrator Official Study Guide: Exam PW0-105, by David D. Coleman and David A. Westcott.

Impedance is the measure of opposition to the flow of alternating current (AC) in a circuit. Impedance mismatch occurs when the impedance of the radio does not match the impedance of the antenna or the cable. This causes some of the transmitted or received signal to be reflected back, resulting in a loss of power and efficiency. The voltage standing wave ratio (VSWR) is a metric that indicates the amount of impedance mismatch in a transmission line. A higher VSWR means a higher impedance mismatch and a lower signal quality. A VSWR of 1:1 is ideal, meaning there is no impedance mismatch and no reflected power.A VSWR of 2:1 means that for every 2 units of forward power, there is 1 unit of reflected power12.

The other options are not correct because they do not affect the VSWR in RF cables. A high gain yagi antenna or a high gain parabolic dish antenna can increase the signal strength and directionality, but they do not cause impedance mismatch in the cable.Radio output power above 100 mW but below 400 mW is within the acceptable range for most WLAN devices and does not cause excessive VSWR in the cable3.

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.Reference:1: CWNA-109 Official Study Guide, page 672:Refraction