Siemens S30810-Q2235-X100 VCM

Integrated Voice Compression at 16 Kbps allows up to 4 calls per channel simultaneously. Compressed voice connections can be switched to various destinations without decompressing and without loss of transmission quality.

In networks with S2M nailed connections, each S2 highway offers up to 30 B-channels, all of which can be used for compressed conmnections. At a compression factor of 1:4, this offers a theoretical maximum of 120 connections. In practise, up to 112 connections are possible.

Each VCM board (Q2235-X) can be used for compressing and decompressing voice connections on up to 15 channels. This means that 8 VCM boards are necessary to obtain the maximum number of compressed connections on one S2 highway. A separate VCM board variant (Q2235-X100) exists for S0 connections, which can serve up to 7 channels.

The compression/decompression of the voice channels is carried out by a new peripheral board type, the VCM. This board emulates a DIU-S2 board on the Hicom side.

The new board is assigned a separate trunk group for compressed voice connections. All connections routed through this board are compressed to 16 Kbps outgoing and decompressed to 64 Kbps incoming.

Since the VCM board emulates a DIU-S2, an appropriate signalling channel (D-channel) is also set up as the first modulated channel subset in a 64 Kbps timeslot. The signalling information is transmitted with the 16 Kbps HDLC protocol.

On the network side, the compressed connections are routed to a "real" DIU-S2 board or STMD board via a nailed connection, where they are "transparently" switched through to the appropriate S2 or S0 highway channel.

• A VCM board has only one D-channel and can therefore only connect to one DIU-S2 or STMD board at a time. However, it is possible for several VCM boards to connect to a DIU-S2 or STMD at the same time (DIU-S2 = > max. 16 VCM15 boards; STMD = > max. 8 VCM7 boards).
• When the compressed trunk group is configured (nailed connection), you will be cautioned to ensure the correct symmetry of the configuration. A symmetrical configuration for two Hicom nodes simply means that the configured VCM B-channels in one node must lead to a corresponding number of switchable VCM B-channels in the partner node.The correct symmetry is the responsibility of the system administrator!!
• Any B-channels of the DIU-S2 / STMD can be assigned. The sequence in which they are seized is not important. However, the VCM B-channels must be assigned to the channels of the DIU-S2 / STMD in sequence.
• The VCM B-channels can also be individually enabled and disabled. However, you must ensure that the subset or "quarter-channel" used for signalling is disabled last (or, conversely, enabled first). The B-channels must always be enabled or disabled symmetrically, i.e. in the home node AND in the partner node.
• The VCM board does not require loadware parameterization.
• The downloading parameter sets of the DIU-S2 are not affected by the voice compression utility.
• The VCM board must not be defined as a reference clock supplier.
• "Partial" failures of the VCM cannot be signalled to the partner node. Channel-specific dependability blocking of the VCM B-channels would lead to an "asymmetrical" situation, i.e. outgoing VC calls from the partner node could lead to blocked B-channels in the home node. For this reaon, dependability always reacts to defective VCM channels by putting the entire board out of service. The loss of the signalling channel can be detected by the partner node, which can then react accordingly and block its own appropriate VCM board.
• The possibility of outgoing connections leading to blocked B-channels in a partner node cannot be avoided elegantly. For this reason, you must always deactivate the entire S0 or S2 highway before reconfiguring the channel compression ratio.
• Routing is carried out with the LCR system, exclusively.
• In the LDAT AMO, the LCR route elements concerned must be assigned the attribute >COMPRESSED<.A threshold value for the maximum number of compression/decompression cycles must also be assigned.
• The VCM circuit data must also contain the >COMPRESSED< attribute (necessary for incoming seizures)
• The LCOSV (LCR class of service for voice connections) of a station line defines whether or not a compressed connection is permitted (appropriate attribute is defined with the LAUTH parameter of the AMO).
• For call data recording purposes, no special "compressed" connection attribute is necessary. The current CDR functionality is sufficient for compressed voice connections (e.g.: ZONE / CARRIER).
• Parallel seizure of the S2M / S0 for non-compressed connections such as data (64 Kbps), analog fax, modem or 64 Kbps voice connections (for higher-grade transmissions) is possible, due to the exclusive assignment of the B-channels for compressed or non-compressed connections.
• DIU-S2 / STMD / VCM boards for compressed connections must not be configured in a remote shelf (RMS), and must not occupy an LTU quarter or LTU half in which a SIUP is configured.
• Echo compensation is not necessary with voice compression, since the G.728 method used has extremely short processing periods (1-2 msecs.).However, in networks which require echo compensation for other reasons, this must take place on the network side of the compressed connections, i.e. voice compression must not take place between two echo compensation units.
• Route optimization can be deactivated for voice compression connections per system.

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