PTP 450 Configuration and User Guide
Diagramming Network Layouts
4-22
pmp-0815 (August 2015)
Diagramming Network Layouts
Avoiding Self Interference
The following section includes information maximizing tower performance by minimizing
self-interference.
Physical Proximity
Two BHM clusters located on the same tower requires uGPS. The uGPS properly
synchronizes the transmit start times of all modules to prevent interference and de-sensing
of the modules. At closer distances without GPS synchronization, the frame structures
cause self-interference. Non-synchronized deployments are highly discouraged.
Furthermore, non-synchronized BHMs on the same tower require that the effects of their
differing receive start times be mitigated by either
100 vertical feet (30 meters) or more and as much spectral separation as possible
within the same frequency band range
the use of the frame calculator to tune the
Downlink Data
parameter in each, so that
the receive start time in each is the same
The constraints for collocated modules in the same frequency band range are to avoid self-
interference that would occur between them. Specifically, unless the uplink and downlink
data percentages match, intervals exist when one is transmitting while the other is
receiving, such that the receiving module cannot receive the signal from the far end.
The interference is less a problem during low throughput periods and intolerable during
high. Typically, during low throughput periods, sufficient time exists for the far end to
retransmit packets lost because of interference from the collocated module.
Spectrum Analysis
BHM or BHS can be used as a spectrum analyzer. See
Mapping RF Neighbor Frequencies
on Page
