Free Practice Questions for CWNP CWNA-109 Exam

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.

 The most effective method for testing roaming in relation to 802.11 VoIP handsets is to place a call with the handset and move around the facility to test quality during roaming. This method allows you to evaluate the actual performance and user experience of VoIP calls over wireless networks, as well as identify any potential issues such as signal strength, interference, latency, jitter, packet loss, or handoff delays. A spectrum analyzer can only show you the RF activity during a VoIP call, but not how it affects the voice quality or roaming behavior. A protocol analyzer can capture the traffic generated when a laptop roams, but it cannot simulate the characteristics of a VoIP handset such as battery life, antenna design, codec support, or QoS features. A built-in roaming monitor is not a common feature in all VoIP handsets, and it may not provide accurate or comprehensive information about the roaming process. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 487; [Voice over Wireless LAN 4.1 Design Guide], page 6-19.

An IEEE 802.11 amendment is a proposed change or addition to the existing 802.11 standard, which defines the specifications and protocols for wireless LANs. An amendment goes through several stages of development, such as draft, sponsor ballot, and final approval, before it is ratified by the IEEE Standards Association and becomes part of the standard. Until then, it has no official impact on the standard, although some vendors may release products based on draft amendments to gain a competitive edge or to influence the final outcome of the amendment . References: [CWNA-109 Study Guide], Chapter 1: Overview of Wireless Standards, Organizations, and Fundamentals, page 25; [CWNA-109 Study Guide], Chapter 1: Overview of Wireless Standards, Organizations, and Fundamentals, page 23; [IEEE website], IEEE-SA Standards Development Process.

PoE stands for Power over Ethernet, which is a technology that allows network devices to receive power and data over the same Ethernet cable. PoE eliminates the need for separate power adapters or outlets for devices such as IP phones, cameras, or APs. PoE requires two types of devices: PSE (Power Sourcing Equipment) and PD (Powered Device). A PSE is a device that provides power to the Ethernet cable, such as a switch, injector, or splitter. A PD is a device that receives power from the Ethernet cable, such as an IP phone, camera, or AP. When implementing PoE, a switch plays the role of a PSE910. References: CWNA-109 Study Guide, Chapter 7: Power over Ethernet (PoE), page 293; CWNA-109 Study Guide, Chapter 7: Power over Ethernet (PoE), page 287.

The HT (802.11n) physical layer (PHY) specification includes support for and compatibility with both ERP and HR/DSSS. ERP stands for Extended Rate PHY, which is an extension of the original DSSS (Direct Sequence Spread Spectrum) PHY that supports data rates up to 54 Mbps in the 2.4 GHz band. HR/DSSS stands for High Rate/Direct Sequence Spread Spectrum, which is another extension of DSSS that supports data rates up to 11 Mbps in the 2.4 GHz band. HT stands for High Throughput, which is a new PHY that supports data rates up to 600 Mbps in both the 2.4 GHz and 5 GHz bands. HT uses OFDM (Orthogonal Frequency Division Multiplexing) as its modulation scheme, but it also supports legacy DSSS and ERP devices by using a dual preamble and header structure that allows backward compatibility. References: , Chapter 3, page 103; , Section 3.1

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.

Shared Key Authentication is a security solution that was defined in the original 802.11 standard as an alternative to Open System Authentication, which does not provide any security at all. Shared Key Authentication uses WEP (Wired Equivalent Privacy) to encrypt and authenticate data frames between the client station and the AP. However, WEP has been proven to be extremely vulnerable to various attacks that can easily crack the encryption key and compromise the network security. Therefore, Shared Key Authentication is deprecated in the 802.11 standard and should never be used in any modern WLAN deployment . References: [CWNA-109 Study Guide], Chapter 10: Wireless LAN Security, page 401; [CWNA-109 Study Guide], Chapter 10: Wireless LAN Security, page 391; [Wikipedia], Wired Equivalent Privacy.