ZyXEL Communications B-2000 User Manual
ZyAIR B-2000 Wireless LAN Gateway with 4-Port Switch
Antenna Selection and Positioning Recommendation
G
Appendix C
Antenna Selection and Positioning
Recommendation
The access points in a wireless LAN send a radio frequency (RF) signal to the antennas, which propagate
and capture the RF signal. Choosing the right antennas and positioning them properly increases the range
and coverage area of a wireless LAN.
and capture the RF signal. Choosing the right antennas and positioning them properly increases the range
and coverage area of a wireless LAN.
Antenna Characteristics
•
Frequency
An antenna in the frequency of 2.4GHz (IEEE 802.11b) or 5GHz(IEEE 802.11a) is needed to
communicate efficiently in a wireless LAN.
communicate efficiently in a wireless LAN.
•
Radiation Pattern
A radiation pattern is a diagram that allows you to visualize the shape of the antenna’s coverage area.
•
Antenna Gain
Antenna gain, measured in dB (decibel), is the increase in coverage within the RF beam width. Higher
antenna gain improves the range of the signal for better communications.
For an indoor site, each 1 dB increase in antenna gain results in a range increase of approximately
2.5%. For an unobstructed outdoor site, each 1dB increase in gain results in a range increase of
approximately 5%. Actual results may vary depending on the network environment.
Antenna gain is sometimes specified in dBi, which is how much the antenna increases the signal power
compared to using an isotropic antenna. An isotropic antenna is a theoretical perfect antenna that sends
out radio signals equally well in all directions. dBi represents the true gain that the antenna provides.
Antenna gain, measured in dB (decibel), is the increase in coverage within the RF beam width. Higher
antenna gain improves the range of the signal for better communications.
For an indoor site, each 1 dB increase in antenna gain results in a range increase of approximately
2.5%. For an unobstructed outdoor site, each 1dB increase in gain results in a range increase of
approximately 5%. Actual results may vary depending on the network environment.
Antenna gain is sometimes specified in dBi, which is how much the antenna increases the signal power
compared to using an isotropic antenna. An isotropic antenna is a theoretical perfect antenna that sends
out radio signals equally well in all directions. dBi represents the true gain that the antenna provides.
Types of Antennas For WLAN
There are two types of antennas used for wireless LAN applications.
• Omni-directional antennas send the RF signal out in all directions on a horizontal plane. The
coverage area is torus-shaped (like a donut) which makes these antennas ideal for a room
environment. With a wide coverage area, it is possible to make circular overlapping coverage areas
with multiple access points.
environment. With a wide coverage area, it is possible to make circular overlapping coverage areas
with multiple access points.
• Directional antennas concentrate the RF signal in a beam, like a flashlight. The angle of the beam
width determines the direction of the coverage pattern; typically ranges from 20 degrees (less