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Chapter 13
Appendix E: Hub Site
Synchronization
When several units are collocated at a common hub site, interference
may occur from one unit to another. ODU units are supplied with
special hardware for the collocation of up to eight units from a central
site.
Using a method called Hub Site Synchronization (HSS) an external
cable is connected from the master to all collocated ODUs; this cable
carries pulses sent to each ODU, which synchronize their transmission
with each other. The pulse synchronization ensures that the
transmission of packets occurs at the same time for all collocated units.
This also results in all of the hub units receiving data at the same time,
eliminating the possibility of interference that could result if some units
transmit while other units at the same location receive.
Figure
13-1 shows interference caused by non-synchronized collocated
units.
Figure
13-1: Interference caused by collocated units
