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1. It is preliminarily inferred that the configuration of the switching device on the service side is incorrect.
2. In general, the transmission device regards the
3. Connect the
4. Check the E1 configurations of the switching devices at both ends to see whether the settings of the PCM30 and PCM31 formats are the same at both ends. If inconsistent, the out-of-multiframe alarm is generated when the PCM30 format is set at the peer end. The reason is that the PCM31 format does not involve multiframes and thus does not carry the multiframe signal octet on timeslot 16 of F0.Note: In general, for the switching devices provided by the vendors including Huawei in
The 2 Mbit/s link usually supports five frame formats: PCM30, PCM31, PCM30 CRC, PCM31 CRC, and non-frame structure.
The PCM30 and PCM30CRC formats are usually used in channel associated signaling. In these formats, timeslot 0 serves as the synchronization timeslot, and timeslot 16 serves as the signaling timeslot and is used to transmit multiframe signals. For voice channels, only timeslots 1 to 15 and 17 to 31 can be used. Such a frame format is called the PCM30.
The PCM31 and PCM31CRC formats are usually used in common signaling and involve no multiframes. Therefore, the signaling can be transmitted on the timeslots other than timeslot 16. Timeslots 1 to 31 can be all used for voice channels or signaling. Such a frame format is called the PCM31.
The PCM30 format involves multiframes, which is different from the PCM31 format and the non-frame structure. A multiframe consists of 16 sub frames named F0 to F15. Each sub frame has 32 timeslots named TS0 to TS31. For F0, TS16 is used to transmit multiframe synchronization alarms and out-of-frame alarms. The first four bits (that is, four zeros) indicate the multiframe location signal. Bits 5, 7, and 8 are service bits and are set to 1 when they are not used. Bit 6 indicates an out-of-multiframe alarm. Bit 6 is set to 1 when the multiframe is out of synchronization and to 0 when the multiframe is synchronized.
Therefore, if the out-of-multiframe alarm is generated on the switching device on the service side, the multiframe synchronization octets are usually mismatched at both ends during interconnection.If the out-of-multiframe alarm and out-of-frame alarm are generated on the switching device on the service side at the same time, the transmission side may be faulty.