1. Modem description
The Sigrand SG-16B modem is a SНDSL-modem. It features an Ethernet-
bridge and is 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 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
Manual line coding selection is available only in the console
management mode – see chapter 3 of this Guide
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