Wireless Network Technologies

Question 1

802.11 technologies

Answer 1

• Frequency
  
  • 2.4 GHz or 5 GHz
  • And sometimes both
• Channels
  
  • Groups of frequencies, numbered by the IEEE
  • Non-overlapping channels would be necessary
• Bandwidth
  
  • Amount of frequency in use
  • 20 MHz, 40 MHz, 80 MHz, 160 MHz

Question 2

Counting antennas

Answer 2

• New technologies were added to 802.11n and802.11ac
• Send multiple streams of information over the same
frequency at the same time
• 802.11n - MIMO - Multiple-Input and Multiple-Output
• 802.11ac - MU-MIMO - Multi-user MIMO

• Number of antennas (802.11n and 802.11ac)
• Used to determine the number of available streams
• (Antennas on the access point) x (antennas on the
client): number of streams
• 2x2:2, 3x3:2, 4x4:4

Question 3

802.11 channel bandwidths

Answer 3

• 802.11a - 20 MHz
• 802.11b - 22 MHz
• 802.11g - 20 MHz

• 802.11n
• 20 MHz or 40 MHz (two contiguous 20 MHz
bonded channels)
• In 2.4 GHz, a 40 MHz channel uses over 80% of the
available bandwidth

• 802.11ac
• 40 MHz for 802.11n stations
• 80 MHz required for 802.11ac stations
• 160 MHz optional (contiguous channels or non-
contiguous bonded channels)

Question 4

2.4 GHz Spectrum for 802.11 - North America

Answer 4

IEEE Channel # 1 6 11

20 MHz

Question 5

Power level controls

Answer 5

• Usually a wireless configuration
  
  • Set it as low as you can
• How low is low?
  
  • This might require some additional site surveys
  • Maintain speeds across required distances
• Consider the receiver
  
  • High-gain antennas can hear a lot
  • Location, location, location

Question 6

Omnidirectional antennas

Answer 6

• One of the most common
  
  • Included on most access points
• Signal is evenly distributed on all sides
  
  • Omni=all
• Good choice for most environments
  
  • You need coverage in all directions
• No ability to focus the signal
  
  • A different antenna will be required

Question 7

Directional antennas

Answer 7

• Focus the signal
  
  • Increased distances
• Send and receive in a single direction
  
  • Focused transmission and listening
• Antenna performance is measured in dB
  
  • Double power every 3dB of gain
• Yagi antenna
  
  • Very directional and high gain
• Parabolic antenna
  
  • Focus the signal to a single point

Question 8

Wireless survey tools

Answer 8

• Signal coverage
• Potential interference
• Built-in tools
• 3rd-party tools
• Spectrum analyzer