1. Modem description
The Sigrand SG-16BG modem is a SНDSL-modem. It is able to exchange
heterogeneous IP and TDM tra ic through Ethernet inter aces and an E1
port.
LAN inter aces 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 inter ace.
The bridge can transmit VLAN IEEE 802.1Q tags through the DSL inter ace
and the Ethernet inter aces.
Connection o TDM-based communication equipment such as telco
equipment, routers and access servers is provided through the Е1 inter ace
(G.703/G.704, 2048 kbps).
The SHDSL inter ace o the modem con orms to ITU-T G.991.2.bis
standard and uses ТСРАМ (Trellis-Coded Pulse Amplitude Modulation) line
coding.
Features o the ТСРАМ line coding:
The ТСРАМ line coding used by G.991.2 (G.SHDSL) compatible modems
has a ew modes. The modes di er in complexity o coding algorithm. The
modes with larger number o modulation positions (ТСРАМ16, ТСРАМ32)
are applicable or higher rates, the modes with less number o modulation
positions (ТСРАМ4, ТСРАМ8) are applied or 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 con iguring 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.
able 1
Line coding Data rate range (kbps)
TCPAM32 256 – 6016
7
