User's Guide

User’s Guide CSC Operation
2110059 Rev 1.0 Proprietary and Confidential Page 59
S52=15 This does the same as S51 but for the V.34 receive side.
S55=37 V.34 options are set to enable asymmetric bit rates, and non-linear encoding. It
disables asymmetric rates, constellation expansion and receiver pre-encoding.
S70=20 This extends the maximum number of retransmissions from the default 12 up to
20. Higher values are possible if needed.
S106=32 The frame size for error correction protocols is set to the minimum 32. The
default is the maximum of 128. Use of a small frame size does reduce direct
throughput, but gives a more robust connection. This leads to fewer
retransmissions and can improve overall throughput in noisy connections that
require frequent retransmissions.
S108=3 Signal Quality is selected to high, meaning that automatic re-training is activated
at the most sensitive setting. This means that the modem will re-train on slight
changes in line quality. This is intended to keep the rate as high as practical.
The data rate discussion in Section 6.5.1.1 also applies to this type of connection.
6.5.4. Connections to Modem Pools
This scenario is also a best case scenario and it should again be possible to achieve speeds of
19200 – 9600 bps in most circumstances. Modem pools are discussed in Section 6.1.3 above.
The SB320 connection is a cellular one and therefore its pool counterpart will be an ETC-capable
modem. This means that the SB320 should be configured in its factory default ETC mode using
AT&F5 as described earlier.
The destination modem’s connection to the pool is a standard landline connection and the remote
modem must be configured as such. In this case the destination modem should be configured to
support the full array of protocols to give it the best possible options for connecting to the cellular
carrier’s modem pool on the landline side.
If any configuration adjustments are to be made, understand that you are either optimizing the
connection from the SB320 to the pool modem or from the destination modem to the pool and not
directly between the SB320 and the destination.