1. Modem description
The Sigrand SG-16B modem is a SНDSL-modem. It eatures an Ethernet-
bridge and is 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 tagged packets through the DSL
inter ace and the Ethernet inter aces.
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
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
6
