User guide

8
5.0 T1/E1 Multiplexer Configuration Guidelines
These guidelines apply to the 20Mbps Backhaul configuration.
o The Canopy 20Mbps Backhaul operating margin should be at least 3dB above receiver
sensitivity; this is a received signal strength of better than -76dB.
o If Canopy 20Mbps Backhaul AES encryption (Release 7.2) is employed, be aware that
doing so will drop the T1/E1 circuit once every 24 hours for the setup of a new encryption
key.
o Enable Canopy 20Mbps Backhaul Hardware Scheduler on both units. (Release 7.2)
o Be aware of the difference between RJ45 Ethernet cable and RJ45 T1/E1 cable; these
cable types are not interchangeable.
o Ground (earth) the TMUX chassis units.
o Set the TMUX Ethernet port configuration to “auto-negotiation on.”
o Set the Canopy BH20 Ethernet configuration to 100 Mbps Full Duplex.
o Set the TMUX units’ T1/E1 cable lengths appropriately.
o If “outside” E1 devices employ 75ohm BNC ports, use a high quality conversion cable to
derive a 120ohm RJ45 E1 equivalent for the TMUX.
o Know the T1/E1 device configuration of the “outside” T1/E1 terminations, in particular
whether they are synchronized by Stratum clock or expect synchronization from the
T1/E1 line (See Section 5.6):
o Set the TMUX port facing a T1/E1 device having Stratum clock synchronization
to “loop timing”; this could be one or both TMUXs; these are typically Central
Office devices.
o Set the TMUX port facing a T1/E1 device expecting to receive synchronization to
“recovered timing”; this is typically a CPE device; the other TMUX unit should be
set to “loop timing”.
o Always install Canopy’s passive reflectors for better signal strength and interference
rejection.
5.1 Canopy System Operating Margin
A statistic concerning the successful operation of any Canopy system, whether in the
TMUX circuit emulation application context or not, is System Operating Margin (SOM).
By definition SOM is the difference in signal strength received and the receiver’s
sensitivity, expressed in dBm (decibels referenced per 1 milliwatt).
Note that a negative dBm value is a signal less than1mW, and a positive value means a
signal stronger than 1mW. In Figure 4 the -96dBm is extremely weak, and in fact
indicates no received signal at all, the circumstance of the “expand stats” screen capture
shown.
Note the Radio Transmit Gain setting is also shown; this is the power being sent into the
Canopy antenna. All Canopy units produce +23dBm (or 200mW). The integrated
antenna adds 7dB, and if the passive reflector is used it adds 18dB (or 8dB if 2.4GHz).
This implies that a Canopy BH20 unit transmits 23+7+18 or 48dB into “space”. The
intermediate “Free Space Loss” (FSL) is dependent upon frequency and range, and
when subtracted from 48dB (in this example) results in the Radio Power Level value
displayed. Other factors may further reduce actual Radio Power Level.