CWNP CWAP-404 Exam With Confidence Using Practice Dumps

The function of the PHY layer is to convert PSDUs to PPDUs for transmissions and PPDUs to PSDUs for receptions. A PSDU (PHY Service Data Unit) is the data unit that is passed from the MAC layer to the PHY layer for transmission, or from the PHY layer to the MAC layer for reception. A PPDU (PHY Protocol Data Unit) is the data unit that is transmitted or received over the wireless medium by the PHY layer. A PPDU consists of a PSDU and a PHY header, which contains information such as modulation, coding, and data rate. The PHY layer adds or removes the PHY header to or from the PSDU during the conversion process. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 97-98

The most likely issue that can be identified from the spectrum analysis is a power mismatch between the APs and the clients. A power mismatch occurs when the APs transmit at a higher power level than the clients, or vice versa. This can cause asymmetric communication, where one side can hear the other, but not vice versa. This can result in poor performance, disconnections, or packet loss. A spectrum analysis can reveal a power mismatch by showing different signal amplitudes or RSSI values for the APs and the clients on the same channel or frequency. The other options are not correct, as they cannot be identified from the spectrum analysis alone. The tablets’ SSID, power save mode, and noise floor can be determined by using other tools or methods, such as protocol analysis, site survey, or device configuration. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 3: Spectrum Analysis, page 79-80

Before a retransmission, the CWmax (Contention Window maximum) value doubles and increases by 1. The CWmax is a parameter that determines the upper limit of the random backoff time that a STA (station) has to wait before attempting to access the medium. The random backoff time is chosen from a range of values between CWmin (Contention Window minimum) and CWmax. The CWmin and CWmax values depend on the AC (Access Category) of the traffic and the PHY type of the STA. If a transmission fails due to a collision or an error, the STA has to retransmit the frame after waiting for another random backoff time. However, to reduce the probability of another collision, the STA increases its CWmax value by doubling it and adding 1. This increases the range of possible backoff values and spreads out the STAs more evenly. The STA resets its CWmax value to its original value after a successful transmission or after reaching a predefined limit. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 7: QoS Analysis, page 196-197