Руководство По Устранению Ошибки для Cisco Cisco Aironet 340 Ethernet Bridges
important, and you need to consider these zones before the implementation of any wireless bridged network.
Any objects in the Fresnel Zone can interfere with the RF signal, which affects the signal, and causes a change
in the LoS. These objects include trees, hills, and buildings.
Any objects in the Fresnel Zone can interfere with the RF signal, which affects the signal, and causes a change
in the LoS. These objects include trees, hills, and buildings.
Fresnel zones are frequency dependent. A frequency of 5.8GHz is used in the bridge utility calculations. Refer
to the Fresnel Zone section of the Cisco Aironet 1400 Series Wireless Bridge Deployment Guide for technical
details on fresnel zone clearance.
to the Fresnel Zone section of the Cisco Aironet 1400 Series Wireless Bridge Deployment Guide for technical
details on fresnel zone clearance.
Figure 2 Fresnel Zone
In order to resolve these issues, make sure that there is visual and radio LoS between the root and non−root
bridges. Check to ensure that nothing obstructs the Fresnel Zone. Sometimes, you need to raise the antenna
height in order to clear the Fresnel Zone. If the bridges are more than six miles apart, the curvature of the
earth encroaches on the Fresnel Zone. Refer to the Outdoor Bridge Range Calculation Utility for additional
assistance.
bridges. Check to ensure that nothing obstructs the Fresnel Zone. Sometimes, you need to raise the antenna
height in order to clear the Fresnel Zone. If the bridges are more than six miles apart, the curvature of the
earth encroaches on the Fresnel Zone. Refer to the Outdoor Bridge Range Calculation Utility for additional
assistance.
Problems with Antenna Alignment
Antenna alignment directly relates to the proper LoS between the two bridges. In case of proper alignment of
the antennas, the RF LoS between the devices is clear and connectivity problems do not occur. When you use
directional antennas to communicate between two bridges, you must manually align the antennas for proper
bridge operation. Directional antennas have greatly reduced radiation angles. The radiation angle for yagi
antennas is approximately 25 to 30 degrees, and for parabolic dish antennas, the radiation angle is
approximately 12.5 degrees. You can use the bridge link test to help measure the alignment of two antennas
after the bridges are associated. The association indicates the antennas point in the general vicinity of each
other, but does not indicate proper alignment of antennas. The link test provides information you can use to
gauge the alignment.
the antennas, the RF LoS between the devices is clear and connectivity problems do not occur. When you use
directional antennas to communicate between two bridges, you must manually align the antennas for proper
bridge operation. Directional antennas have greatly reduced radiation angles. The radiation angle for yagi
antennas is approximately 25 to 30 degrees, and for parabolic dish antennas, the radiation angle is
approximately 12.5 degrees. You can use the bridge link test to help measure the alignment of two antennas
after the bridges are associated. The association indicates the antennas point in the general vicinity of each
other, but does not indicate proper alignment of antennas. The link test provides information you can use to
gauge the alignment.
Typically, when two antennas are aligned to the edges of their radiation patterns, communication can be
marginal, as packets are lost, retry counts are high, and signal strength is low. However, when two antennas
are properly aligned, communication improves, and all packets are received, retry counts are lower, and signal
strength is high. Refer to the Basic Antenna Alignment section of Antenna Basics for information on basic
antenna alignment, and for instructions on how to perform link tests.
marginal, as packets are lost, retry counts are high, and signal strength is low. However, when two antennas
are properly aligned, communication improves, and all packets are received, retry counts are lower, and signal
strength is high. Refer to the Basic Antenna Alignment section of Antenna Basics for information on basic
antenna alignment, and for instructions on how to perform link tests.
Clear Channel Assessment Parameter (CCA)
CCA is essentially the establishment of a noise floor below which it ignores RF inputs, in search of a good,
solid signal. With the programmable CCA feature, wireless bridges can be configured to a particular
solid signal. With the programmable CCA feature, wireless bridges can be configured to a particular