User's Manual Part 1
Release8OverviewofCycloneNetworks
Issue2,November2007 Draft5forRegulatoryReview 94
For example, in Figure 23, AP4
• is not synchronized with any of the other APs.
• is transmitting nearby the other APs while they are expecting to receive SM
transmissions from a maximum distance.
Figure 23: 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 Cyclone 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 Cyclone link, sync should be derived from GPS timing.
NOTE:
The OFDM Series BHMs generate their own sync. For more information about
these modules, see the user guides that support them. Titles are listed under
Products Not Covered by This User Guide on Page 34.
Advantage of GPS Sync
Although the embedded timing generation capability of the Cyclone 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 Cyclone modules, except by
GPS timing (shown in
Figure 24).