User guide

Canopy System User Guide Analyzing the RF Environment
pmp-0229 (Mar 2013)
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Noting Possible Obstructions in the Fresnel Zone
The Fresnel (pronounced fre·NEL) Zone is a three-dimensional volume around the line of sight of
an antenna transmission. Objects that penetrate this area can cause the received strength of the
transmitted signal to fade. Out-of-phase reflections and absorption of the signal result in signal
cancellation.
The foliage of trees and plants in the Fresnel Zone can cause signal loss. Seasonal density,
moisture content of the foliage, and other factors such as wind may change the amount of loss.
Plan to perform frequent and regular link tests if you must transmit though foliage.
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Radar Signature Detection and Shutdown
With Release 8.1, Cambium met ETSI EN 301 893 v1.2.3 for Dynamic Frequency Selection (DFS)
in slave as well as master radios. DFS is a requirement in certain countries and regions for systems
to detect interference from other systems, notably radar systems, and to avoid co-channel
operation with these systems. With Release 8.1, all 5.7-GHz connectorized modules and all 5.4-
GHz modules were ETSI DFS capable. These two products were sold only outside the U.S.A. and
Canada. No other products had a DFS option.
The Configuration => Radio web page in Release 8.1 allowed the operator to enable or disable
DFS. Operators in countries with regulatory requirements for DFS must not disable the feature and
must ensure that it is enabled after a module is reset to factory defaults. Operators in countries
without regulatory requirements for DFS should disable DFS to avoid the additional minute of
connection time for APs, BHMs, and SMs, and avoid the additional two minutes for BHSs.
With Release 8.2 and later, all of the 5.2-, 5.4-, and 5.7-GHz master and slave radios satisfy the
requirements that the FCC Report and Order 03-287, Industry Canada, and ETSI EN 301 893
v1.3.1 impose for DFS. These regulations differ on
• which radio frequency band(s) have DFS required.
• whether older radios must have DFS enabled.
• whether SMs and BHSs, in addition to APs and BHMs, must have DFS enabled.
Moreover in Release 8.2 and later, 5.4-GHz radios that are set for Canada or Australia omit center
channel frequencies from 5580 to 5670 MHz, inclusive, from their GUIs and cannot operate in
that range. This satisfies Canadian and Australian requirements that protect weather radio from
interference by co-channel operation. This leaves 6 instead of 9 channels at 25-MHz center
spacing
3
(or 7 instead of 11 at 20-MHz center spacing). Operators in the U.S.A. should avoid the
weather channels as well, but may be able to temporarily use them after spectrum analysis reveals
that no competition exists.
3
25-MHz center channel spacing is recommended for CAP 130 (Advantage AP) and 20-Mbps BH.