Paradyne COMSPHERE 3920Plus Technical Reference Manual page 327

Synchronous Data Compression
Overview
The Paradyne proprietary Synchronous Data Compression (SDC) feature allows an increase of
throughput in data transmission, and has an error correcting procedure so that transmitted data is
less sensitive to channel disturbances.
The ITU-T recommendations, V.42bis, and V.42 have data compression and error correcting (EC)
procedures for DCEs connected to asynchronous DTEs. These procedures form the basis for
Paradyne's SDC feature.
Within the SDC feature, two DTEs can exchange data via a synchronous protocol (Figure H-1)
while the DCE provides the new synchronous data compression and error correction functions
(Figure H-2). The synchronous data from the local DTE, after compression, is inserted into DCE
frames which are sent to the remote DCE. Inverse operations then occur at the remote DCE.
SYNCHRONOUS
DTE
Figure H-1. Sample DTE Exchange of Data via Synchronous Protocol and SDC
3920-A2-GH30-40
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Synchronous Data Format
SDC Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTE and DCE Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SDC User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Flow Control Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tuning SDC Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTE Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Modem Configuration
SDC Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SYNCHRONOUS PROTOCOL
19.2 kb/s 9.6 kb/s
DCE
October 1998
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2 kb/s
DCE
H
H-1
H-2
H-2
H-3
H-3
H-4
H-5
H-6
H-6
H-6
H-7
SYNCHRONOUS
DTE
495-14784-01
H-1