Wireless Networks

Question 1

What are wireless Networks?

Answer 1

• Wireless local area networks (WLANs) use radio waves to connect devices, e.g. WI-FI
• Wireless signals can be intercepted more easily than wired signals as there is not physical connection to the network.

Question 2

Wireless Network Fundamentals

Answer 2

• WLAN is based around a central communication device called a wireless Access Point (WAP)
• In homes, it is commonly known as a router provided by ISP (internet service provider)
• Larger buildings have several discreet WAPs
• Each wireless network is configured with a service Set Identifier (SSID) - known as network name

Question 3

Connecting to a wireless Networks

Answer 3

• Can for networks within range on your devices

Question 4

Open Networks

Answer 4

• An open network is one that has been configured so that a password is not required
• not secure

Question 5

Interface with a wired Network

Answer 5

• most wireless networks are connected to a wired network
• this lets you run cables to some devices where you may want a reliable network performance

Question 6

Wi-Fi

Answer 6

• Wi-Fi Alliance grants certification to products than meet the wi-fi standard
• wireless networks use a specific range of radio wave frequencies to transmit data
• Most WLAN devices will be dual band: operate on 2.4GHZ or 5.0GHZ
• Channels

Question 7

What is a CSMA/CA protocol?

Answer 7

• Is a protocol used in wireless networking. It makes sure that network collisions are avoided

Question 8

what is a carrier-sense?

Answer 8

• check for presence of any other signals, a decision is made whether to sen the message or try again later

Question 9

what is a collision avoidance?

Answer 9

an end device, which is either sending or receiving data across the network — that wanted to send will wait for a period of time before trying again

Question 10

What is a hidden node problem?

Answer 10

hidden node problem - which interferes with the data transmission.

Question 11

How does a hidden node problem work?

Answer 11

• a device can be out of range from the broadcast of another device, but still be on the network connecting them
• both be sending data to the WAP at the same time, but ⇒ as a result, the WAP would not be able to receive any data due to the data collisions.

Question 12

How does Request to send/clear to send work?

Answer 12

• Once the channel is determined to be idle, a signal is sent called Request to Send (RTS).
• The answering device then sends a Clear to Send (CTS) reply.
• ensures that only that device will send its message, by not responding to further RTS signals until the original sender has finished.

Question 13

What is WI-FI?

Answer 13

Wi-Fi allows devices, such as smartphones, tablets and laptops to communicate wirelessly within a particular network area

Question 14

What is an Wireless Access Point?

Answer 14

A wireless access point is device that allows wireless devices to connect to a wired network using Wi-Fi.

Question 15

What is an Wireless adaptor?

Answer 15

A wireless adaptor performs a similar function to a network interface card (NIC) but wirelessly. The wireless adaptor can be built into the computer or it can be a portable device fitted into a USB port.

Question 16

How does a wireless router work at home?

Answer 16

In a home or office network a wireless router transmits a Wi-Fi signal that can be shared by more than one device. This approach is used to share an Internet connection between several devices using a mixture of Wi-Fi and Ethernet cable connectivity.

Question 17

What is a WPA/WPA2 (Wi-Fi Protected Access) ?

Answer 17

WPA/WPA2 (Wi-Fi Protected Access) are encryption protocols designed to protect a Wi-Fi connection.
This protocol is used whenever an attempt is made to connect to a secured wireless network, by prompting the user for a security key or passcode. This ensures that the connection is secured with encryption.

Question 18

What is an SSID?

Answer 18

SSID (service set identification) is a unique 32-character identifier that is used to name a wireless network.

Question 19

What is media access control?

Answer 19

A MAC (Media Access Control) address is the physical address of a networking device (for example a NIC). It is a unique identifier assigned by the manufacturer and is stored in the device’s read-only memory.

Question 20

What is Carrier Sense Multiple Access with Collision Avoidance?

Answer 20

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) operates by the computer sending a signal indicating that it is about to transmit data. Other computers can then avoid a collision by delaying when they will transmit data.

Question 21

CSMA/CA access methods can be used both with and without the Request to Send / Clear to Send (RTS/CTS) approach - With RTS/CTS?

Answer 21

1.RTS signal is sent by the sender of the package
2.then a CTS signal is sent by the intended receiver of the package
3.consequently the sender and receiver are aware of a data transmission and hold off for the duration of the main transmission

Question 22

CSMA/CA access methods can be used both with and without the Request to Send / Clear to Send (RTS/CTS) approach - Without RTS/CTS?

Answer 22

1.The computer wanting to send a data packet senses if the channel is ‘idle’
2.then it is able to send the data packet
3.if the channel is sensed as ‘busy’, the sender will wait and try again

Question 23

Where is the CSMA/CA method used?

Answer 23

The CSMA/CA method is widely used in WLANs although it has the disadvantage of reducing network performance since it increases the amount of network traffic.