CWNP CWNA-109 Dumps Questions Answers

Weak signal strength is the likely cause of the low data rate issue for the client that has a signal strength of -84 dBm and a noise floor of -96 dBm. The client is an 802.11ac client and connects to an 802.11ac AP. Both the client and AP are 2x2:2 devices. Signal strength is the measure of how strong the RF signal is at the receiver. Signal strength can affect the reliability and performance of the wireless connection, as well as the data rate and throughput of the traffic. The higher the signal strength, the better the signal quality and the higher the data rate. The lower the signal strength, the worse the signal quality and the lower the data rate.

The data rate of an 802.11ac connection depends on several factors, such as channel bandwidth, modulation and coding scheme (MCS), spatial streams, guard interval, and beamforming. However, these factors are also influenced by the signal strength, as they require a certain signal-to-noise ratio (SNR) to operate properly. SNR is the ratio of the signal strength to the noise floor, which is the measure of the background noise or interference in the RF environment. The higher the SNR, the more robust and efficient the communication. The lower the SNR, the more prone and vulnerable to errors and retries.

According to the CWNA Official Study Guide , Table 3.7, page 112, an 802.11ac connection with a channel bandwidth of 80 MHz, an MCS of 9, two spatial streams, a short guard interval, and no beamforming can achieve a maximum data rate of 867 Mbps. However, this data rate requires a minimum SNR of 30 dB to maintain a sufficient signal quality. If the signal strength is -84 dBm and the noise floor is -96 dBm, then the SNR is only 12 dB (-84 dBm - (-96 dBm) = 12 dB), which is far below the required SNR for this data rate. Therefore, the data rate will drop significantly to match the lower SNR and signal quality.

To solve this problem, the signal strength should be increased to improve the SNR and data rate. This can be done by adjusting the output power or channel assignment of the AP or client, relocating or reorienting some APs or antennas to reduce attenuation or interference, updating or replacing some faulty or outdated hardware or software components, etc. References: , Chapter 3, page 112; , Section 3.2

A laptop-based spectrum analyzer with a directional antenna is the best solution for locating a non-802.11 device that is suspected of causing interference on the WLAN. A spectrum analyzer is a device or a software application that can measure and display the frequency spectrum of electromagnetic signals in a given range. A spectrum analyzer can show the amplitude, frequency, bandwidth, modulation, and other characteristics of different signals in the spectrum, which can help identify their sources and types. A spectrum analyzer can also detect non-802.11 devices that may cause interference on the WLAN, such as microwave ovens, cordless phones, Bluetooth devices, or radar systems. A laptop-based spectrum analyzer is a software application that runs on a laptop computer and uses an external USB adapter as its RF interface. A laptop-based spectrum analyzer has the advantage of being portable, flexible, and cost-effective compared to a hardware-based spectrum analyzer. A directional antenna is an antenna that radiates or receives RF signals more strongly in one direction than in others. A directional antenna has a high gain and a narrow beamwidth, which means it can focus the RF energy in a specific direction and reduce the interference from other directions. A directional antenna can also increase the range and sensitivity of the RF signal detection. To locate a non-802.11 device that is causing interference on the WLAN, a laptop-based spectrum analyzer with a directional antenna can be used to perform a technique called RF hunting or triangulation. This technique involves pointing the directional antenna in different directions and observing the signal strength and characteristics of the interfering device on the spectrum analyzer. By moving around and changing the direction of the antenna, the location of the interfering device can be estimated based on where the signal strength is highest and most consistent. References: 1, Chapter 7, page 282; 2, Section 4.3