Specifications

Chapter 1 Introduction Installation and Operation Manual
1-8 Functional Description ASMi-54C LRS-102 Ver. 2.0
• Ethernet subsystem, including the following functions:
 Main Ethernet switch
 Ethernet switch for access to the SHDSL subsystem
 External Ethernet port interfaces (transceivers)
• Timing subsystem, including the internal timing generator
• Local management subsystem.
SHDSL Subsystems
ASMi-54C includes two identical, independently-operating SHDSL subsystems,
each handling four lines: one for lines 1 to 4, and the other for lines 5 to 8.
The SHDSL subsystems comply with the applicable SHDSL.bis sections of ITU-T
Rec. G.991.2 (2004). See the
SHDSL Transport section on page 1-2 for a
description of SHDSL subsystem characteristics and capabilities. The type of
SHDSL interfaces provided by the module, central (STU-C) or remote (STU-R), is
user-selectable:
• In the STU-C mode, the SHDSL subsystem handles the SHDSL link activation,
which includes the handshaking and synchronization processes needed to
set up a link between the STU-C and the STU-R in accordance with the SHDSL
parameters selected by the user. The subsystem operating in the STU-C
mode also provides the timing reference for the generation of SHDSL line
signals.
• In the STU-R mode, the SHDSL subsystem performs similar activities, except
that its operation is coordinated by the STU-C, and the SHDSL subsystem
timing is locked to the clock recovered from the line signal.
An ASMi-54C module can operate as STU-R only if the far-end equipment is
another LRS-102 (which must include an ASMi-54C module serving as STU-C).
SHDSL Modems
Each SHDSL modem includes two main sections: a digital processor that prepares
the transmit data stream sent to the line and demultiplexes the data stream
received from the line, and an SHDSL line interface that generates the transmit
line signal and regenerates the received line signal.
• The transmit path of the digital processor accepts the transmit payload
stream from the payload multiplexer, and then adds the SHDSL overhead to
form a standard SHDSL.bis signal with variable rate, from a minimum of
200 kbps to a maximum of 5700 kbps.
The main types of SHDSL overhead are: framing data, error detection and
correction data (also used for performance monitoring), and an embedded
operations channel (
eoc ) that enables the STU-C function to control the
STU-R function of the remote equipment connected to the corresponding
port. The SHDSL line interface section of the modem then encodes the
resulting data stream in accordance with the user-specified parameters (line
data rate and regional characteristics), and transmits the resulting signal to
the external line.
Note