1. Modem description
The set of the Sigrand SG-16BVo and Sigrand SG-16BVs modems is
intended for corporate network applications. The modems allow to transmit
two voice channels and one data channel simultaneously using the single
pair only. The data channel of the modem features an Ethernet-bridge and
can be used to connect various Ethernet 10/100 Base-T devices.
The bridge can transmit VLAN IEEE 802.1Q tagged packets through the
DSL interface and the Ethernet interfaces.
The SHDSL interface of the modem conforms to ITU-T G.991.2.bis
standard and uses ТСРАМ (Trellis-Coded Pulse Amplitude Modulation) line
coding.
Features of the ТСРАМ line coding:
The ТСРАМ line coding used by G.991.2 (G.SHDSL) compatible modems
has a few modes. The modes differ in complexity of coding algorithm. The
modes with larger number of modulation positions (ТСРАМ16, ТСРАМ32)
are applicable for higher rates, the modes with less number of modulation
positions (ТСРАМ4, ТСРАМ8) are applied for lower rates. Respectively, the
more complicated the coding algorithm the worse the channel noise
immunity and vice versa.
So take special attention to the ТСРАМ line coding algorithm selection
while configuring the line rate. It may be necessary to change the line
coding to achieve the best result.
Table 1 shows the line coding options and respective data rate ranges.
Table 1
Line coding
Data rate range (kbps)
TCPAM32
256 – 6016
TCPAM16
192 – 3840
TCPAM8
192 – 1216
TCPAM4
64 – 704
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