E1 MUX and GSM Base Station

We have the following transmission path to a GSM BTS

BSC <—> MW Link <—> E1 MUX (Loopback mode) <—> BH Master <—> BH Slave <—> E1 MUX (Reversed mode) <—> GSM Base Station

The GSM BTS is not properly synchronized (Alarm: No usable PCM reference). Everything is OK for some time, until the BTS eventually goes out of service or stops receiving calls.

What is the possible solution?

Is the end labled BSC the side that provides clock? Also, make sure that your Canopy BH’s are hard coded for 100/full (remove the check marks for the other speeds/duplex settings). On the MUX validate that AUTO is selected for the ethernet speed/duplex. Next under the E1 configuration parameter select the proper cable length between the MUX and the end device.

Are both MUX units grounded using the screws on the back of the unit and a ground wire?

Are you using encryption on the BH link? If you are then you must keep in mind that the BH’s do stop passing traffic once a day during a key exchange.

Yes, the BSC (Base Station Controler) is providing the clock. Thanks for the reply. I’ll check the setting tomorrow.

We have the canopy 5.7 bh20 and canopy 4 port E1’T1 muxs using the T1 setting to replace wired T1s and we are experiencing the same trouble. The circuit can run anywhere from 6 hours to 1 hour before the site begins to reject the signal and starts to recycle the radios, stopping all traffic. We are using Nokia base stations and don’t receive any errors when the site begins to recylce. Our bh20s have the latest release and are set to hardware schedule and according the release notes for the mux. We are working on the solution and I will update any progress.

Yesterday we integrated 2 BTSs in the same way as described in the first post of this thread with all the configurations applied in the second post. BH links are independent. Late in the night (around 23:00), both BTSs went out of service at the exactly same time (2 minutes drift due to different time settings of the BHs). Now, that is very strange thing. Both BTSs are Ericsson’s. When Motorola BTS is connected this way, Syncronization alarm appears. Any clue?