1. Modem description
The Sigrand SG-16BG modem is a SНDSL-modem. It is able to exchange
heterogeneous IP and TDM traffic through Ethernet interfaces and an E1
port.
LAN interfaces work through a built-in Ethernet-bridge and are designed to
connect distributed local area networks as well as remote computers and
other devices equipped with an Ethernet interface.
The bridge can transmit VLAN IEEE 802.1Q tags through the DSL interface
and the Ethernet interfaces.
Connection of TDM-based communication equipment such as telco
equipment, routers and access servers is provided through the Е1 interface
(G.703/G.704, 2048 kbps).
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
7
