Wireless Fundamentals Flashcards
Wireless LAN standards are defined in:
IEEE 802.11
What organization certifies wireless devices as 802.11 compliant, but is not directly connected with the IEEE
Wi-Fi Alliance
T/F: When a wireless device transmits a frame, all devices within range receive the frame, similar to devices connected to an ethernet hub
T
T/F: When a wireless device transmits a frame, only the target destination device receives the frame, similar to devices connected to an ethernet switch
F
All devices receive all frames, like an ethernet hub
Which of these methods is used to facilitate half-duplex connections in wireless networks?
a) CSMA/CD
b) CSMA/CA
b) CSMA/CA
CSMA/CD is used for wired networks
What does CSMA/CA stand for?
Carrier Sense Multiple Access with Collision Avoidance
Explain how CSMA/CA prevents collisions on a wireless network
A device will wait for other devices to stop transmitting before it transmits data itself.
If the channel isn’t free, it will wait a random period of time before sending the frame. After the wait, it will check the channel again, and send the frame if it is free.
What is signal absorption
When a wireless signal passes through a material and is converted into heat, weakening the signal
What is signal reflection
When a wireless signal bounces off a material, for example, metal. Think of elevators
What is signal refraction
When a wireless signal is bent when entering a medium where the signal travels at a different speed
What is signal diffraction
When a wireless signal encounters an obstacle and travels around it. Can result in signal blind spots
What is signal scattering
When a material causes a signal to scatter in all directions. Can result from uneven/porous surfaces, etc
The RF range is from _____ to _____
30 Hz to 300 GHz
What RF bands are Wireless LANs used for?
- 2.4 GHz (really 2.400 GHz to 2.4835 GHz)
- 5 GHz (really 5.150 GHz to 5.825 GHz)
Which wireless band provides better range in open space and better wall penetration
2.4 GHz
How many channels are there in the 2.4 GHz band?
11 in North America. Can vary by country
T/F: In larger WLANs with multiple APs, it’s important that adjacent APs don’t use overlapping channels in order to avoid interference
T
T/F: In larger WLANs with multiple APs, it’s important that adjacent APs all use the same channel in order to avoid interference
F
In the 2.4 GHz band, it is recommended to use channels ____, ____, and ____
Channels 1, 6, and 11
This ensures that each channel has no overlap with each other
T/F: The 5 GHz band consists of non-overlapping channels
T
T/F: The 5 GHz band consists of overlapping channels
F
T/F: The 2.4 GHz band consists of overlapping channels
T
T/F: The 2.4 GHz band consists of non-overlapping channels
F
A ____ AP placement pattern is recommended to avoid channel interference
Honeycomb
802.11 specifies wireless frequencies in the ___ band
2.4 GHz
802.11 wireless has a max data rate of ____
2 Mbps
802.11b specifies wireless frequencies in the ____ band
2.4 GHz
802.11b wireless has a max data rate of ___
11 Mbps
802.11a specifies wireless frequencies in the ___ band
5 GHz
802.11a wireless has a max data rate of ___
54 Mbps
802.11g specifies wireless frequencies in the ____ band
2.4 GHz
802.11g wireless has a max data rate of ____
54 Mbps
802.11n specifies wireless frequencies in the ____ band
2.4 GHz and 5 GHz
802.11n has a max data rate of ___
600 Mbps