User guide

Understanding Canopy Networks March 2005
Through Software Release 6.1
Issue 1 Page 69 of 425
Canopy System User Guide
Figure 29: One unsynchronized AP in cluster
The result is self-interference. In this scenario, the self-interference can be avoided only
by synchronizing the TDD transmit cycles of all APs that operate in the same frequency
band.
An AP that is isolated by at least 5 miles (8 km) from any other Canopy equipment, or a
BHM in an isolated standalone BH link can generate and pass sync pulse without GPS
timing and not risk that interference will result from the generated sync. In any other type
of Canopy link, sync should be derived from GPS timing.
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NOTE:
The 45-Mbps BHM generates its own sync. For more information about
this module, see the Canopy 45-Mbps Backhaul User Guide.
Advantage of GPS Sync
Although the embedded timing generation capability of the Canopy AP and BHM keeps a
precise clock, no trigger exists to start the clock at the same moment in each AP of a
cluster. So, the individual AP can synchronize communications between itself and
registered SMs, but cannot synchronize itself with other Canopy modules, except by GPS
timing (shown in Figure 30).