User guide

Canopy T1 / E1 Application Note
Issue 1, June 2005 9
Figure 4. BH20 RSSI and Jitter Display indicating no signal.
In actual operation the Canopy BH20 unit will display a RSSI value above -79dBm.
Motorola strongly recommends the use of passive reflectors at both ends as their narrow
beam characteristic means less multipath signal and better “rejection” of whatever actual
multipath signal there is.
5.2 Electrical Grounding of the TMUX
As stated in the Canopy T1/E1 Multiplexer User Guide, proper grounding (or “earthing”) is
essential for reliable circuit application. One of the Phillips screws on the back of the
TMUX unit should be loosened and connected to a sufficiently large gauge grounding
wire. This grounding should include any T1/E1 equipment as well, so the T1/E1 electrical
signal may be properly interpreted by the TMUX unit. Use local practices or refer to
standard electrical code.
5.3 TMUX and Canopy BH20 Ethernet Port Settings
The link between the TMUX and its associated Canopy backhaul unit is a 100Mbps full
duplex Ethernet link. No other Ethernet operational mode is allowed due to the
demanding aspects of circuit emulation.
Ethernet technology defines an “auto negotiation” process such that two Ethernet devices
may dynamically and automatically “agree” to operate in either 10Mbps half duplex,
10Mbps full duplex, 100Mbps half duplex, or 100Mbps full duplex. While this process is
defined by the Clause 28 of the 802.3u Fast Ethernet supplement to the IEEE 802.3
standard, in practice not all devices conform. Consequently a device having this
capability does not mean that all Ethernet interfaces will properly auto-negotiate.
Canopy and TMUX units do not auto-negotiate with each other, but with manual
configuration the required 100 Mbps full duplex operation can be guaranteed. If this
setting is not properly configured the circuit application will not operate properly, resulting
in T1/E1 circuit errors. This “problem” is thought to be responsible for the majority of the
field problems experienced with circuit emulation over Canopy.