Wireless Fundamentals 3

Here you will answers to Wireless Fundamentals – Part 3

Question 1

What unit of measurement is used to represent the strength of an antenna’s radiation pattern?

A. dBi
B. dBm
C. mW
D. GHz

 

Answer: A

Explanation

+ dBi is a unit of sound that measures acoustical and electrical power. In particular, dBi is a measure of the increase in signal (gain) by your antenna compared to the hypothetical isotropic antenna (which uniformly distributes energy in all directions) -> It is a ratio. The greater the dBi value, the higher the gain and the more acute the angle of coverage.

+ dBm is a measure of signal power. It is the the power ratio in decibel (dB) of the measured power referenced to one milliwatt (mW). The “m” stands for “milliwatt”.

Question 2

What are the four types of wireless networks? (Choose four)

A. Wireless PAN
B. LAN
C. MAN
D. VLAN
E. WAN

 

Answer: A B C E

Question 3

What is the typical maximum range of a wireless PAN?

A. 45 feet
B. 50 feet
C. 55 feet
D. 60 feet

 

Answer: B

Explanation

A wireless personal area network (WPAN) is a network that exists within a relatively small area, connecting electronic devices such as desktop computers, printers, scanners, fax machines, personal digital assistants (PDAs) and notebook computers.

I am not sure about the maximum range of a wireless PAN but typically a wireless personal area network can communicate within a range of about 30 feet (10 meters). I can’t find any information saying that it can operate up to 50 feet but in the exam you should choose “50 feet”.

The main WPAN technology is Bluetooth. Some technologies are IrDA, UWB, Z-Wave and ZigBee…

Question 4

What is the general maximum coverage area of a wireless PAN?

A. within 30 feet
B. within 35 feet
C. within 40 feet
D. within 45 feet

 

Answer: A

Explanation

It is weird that Cisco thinks “maximum coverage area” is different from “maximum range”!  But this question has correct answer of 30 feet.

Question 5

What relatively new standard applies to wireless MANs?

A. IEEE 802.11
B. IEEE802.3Z
C. Wi-Fi
D. IEEE 802.16

 

Answer: D

Question 6

True or false: A computer device stores data in analog form.

A. true
B. false

 

Answer: B

Question 7

On what layers of the OSI reference model do wireless networks operate? (Choose two)

A. Physical layer
B. Network layer
C. data link layer
D. session layer

 

Answer: A C

Question 8

RF signals offer relatively short range as compared to light signals. True or false?

A. True
B. False

 

Answer: B

Explanation

First we need to explain about Line-of-sight & non-line-of-sight:

Line-of-sight (LOS) is a condition where a signal travels over the air directly from a wireless transmitter to a wireless receiver without passing an obstruction.

Conversely, non-line-of-sight (NLOS) is a condition where a signal from a wireless transmitter passes several obstructions before arriving at a wireless receiver. The signal may be reflected, refracted, diffracted, absorbed or scattered.

In most case RF signals are line-of-sight signal and “light” is a non-line-of-sight signal so FR signals offer longer range than light signals.

Question 9

Spread spectrum generally requires user licenses. True or false?

A. True
B. False

 

Answer: B

Explanation

Spread spectrum is a form of wireless communications in which the frequency of the transmitted signal is deliberately varied. This results in a much greater bandwidth than the signal would have if its frequency were not varied. For example, if you listen to an FM radio at 100 MHz, the signal stays at 100 MH and does not vary. But when you are talking to your friends via a cell phone then you are using spread spectrum technology as the mobile frequency varies from time to time (but within a specific range). This technology is called frequency hopping.

Spread-spectrum systems offer the flexibility of license-free operation in four distinct frequency bands (902-928 MHZ, 2400-2483.5 MHZ, 5150-5350 MHZ, and 5725-5825 GHz), and there are many other unlicensed ISM frequency bands, the two frequencies most commonly used for environmental monitoring and SCADA applications are 902 MHz-928 MHz and 2400 MHz-2483.5 MHz. Wireless LANs are common in the 2.4GHz band where a high data rate over short distance is required. Bluetooth and WiFi communications use the 2.4GHz band.

Question 10

Approximately up to what range do direct infrared systems operate?

A. 0.5 mile
B. 1 mile
C. 1.5 mile
D. 2.0 mile

 

Answer: B

Explanation

The range of an infrared light system can vary from a few feet with PDA applications to 1 mile with direct infrared systems. This is significantly less range than with RF systems.