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MGX8850 using SRME for bulk distribution and VISM-PR cards

My customer has a BPX/MGX backbone. They are a GSM mobile operator using VISM-PR cards in AAL2 trunking mode. At most of the MGX sites we use the E1 backcards on the VISM cards for connectivity into the Ericsson MSC. We have just deployed a new site where the MSC has STM-1 connectivity instead of E1 connectivity (hence the use of SRME cards)

We are experiencing crackling or static on the voice bearer channels. The speech quality is good, but the crackling appears in the background and in one direction only. We have set up a test to simulate the voice connectivity where we use an E1 tester tos end a test tone on a speciffic timeslot. What we have found is that if we increase the frequency from about 1000HZ to 1400HZ the crackling appears. If we decrease the frequency it goes away. In addition if we attenuate the signal to about -19db the crackling goes away. Any ideas


Re: MGX8850 using SRME for bulk distribution and VISM-PR cards

Have you seen bug CSCuk44700. Looks similar to your problem. Do you have VAD enabled? If so turn off VAD. Here is a document on troubleshooting Hissing and Static. This should help.

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