Free CWNP CWNA-109 Exam Dumps April 2026

In the 2.4 GHz frequency band used for 802.11 wireless networks, the channel bandwidth is typically 20 MHz, but the actual frequency spread of each channel is about 22 MHz due to the modulation techniques used. This spread causes overlap between adjacent channels, which can lead to interference and degrade network performance. To avoid this, it's essential to use non-overlapping channels.

The three non-overlapping channels in the 2.4 GHz band are 1, 6, and 11. Each of these channels is spaced sufficiently apart to avoid interference with each other:

Channel 1: Centered at 2.412 GHz.

Channel 6: Centered at 2.437 GHz.

Channel 11: Centered at 2.462 GHz.

Given the options provided, option C (1 and 5) is the closest to a pair of non-overlapping channels, although in practice, channel 5 would still cause some interference with channel 1 due to the 22 MHz spread. The ideal choice for non-overlapping channels would be any two channels among 1, 6, and 11, but this is not an option provided. Therefore, within the given options, 1 and 5 are the best choice, understanding that in a real-world scenario, 1 and 6 or 6 and 11 would be preferred to avoid overlap.

CWNA Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109, by David D. Coleman and David A. Westcott.

Understanding 2.4 GHz channel arrangement and interference patterns in 802.11 wireless networks.

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 guard interval is a short period of time inserted between the symbols of an OFDM signal to prevent inter-symbol interference and improve the robustness of the transmission1. The guard interval can have different values depending on the 802.11 standard and the configuration of the device.For example, 802.11n supports two guard intervals: 800 ns (normal) and 400 ns (short)2.802.11ac supports the same guard intervals as 802.11n, plus an optional 200 ns guard interval for 80 MHz and 160 MHz channels3.802.11ax supports three guard intervals: 800 ns, 1600 ns, and 3200 ns4.

The guard interval affects the data rate because it determines the duration of each symbol. A shorter guard interval means more symbols can be transmitted in a given time, resulting in a higher data rate. However, a shorter guard interval also means less protection against inter-symbol interference, which may degrade the signal quality and increase the error rate. Therefore, there is a trade-off between data rate and reliability when choosing the guard interval.

The MCS tables for HT and VHT PHY devices show the data rates for different combinations of modulation, coding, channel width, spatial streams, and guard intervals.For example, for a VHT device using MCS 9 with QAM-256 modulation, 5/6 coding rate, 80 MHz channel width, and one spatial stream, the data rate is 433.3 Mbps with a normal guard interval (800 ns) and 486.7 Mbps with a short guard interval (400 ns)2. Therefore, the guard interval impacts the data rate according to the MCS tables.