An Introduction to the Ericsson Transport Network Architecture ...

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The control signals, which come from the
Vertical Control Board (VCB), are distributed
to all SMBs. In addition, HCB collects
external alarms, e.g. temperature, fans,
etc.
The VCB is the core of the control functions
in the AXD 4/1. Packet handling and
control of the Switch plane are the two
main tasks performed by the VCB, which
contains the Unit Processor (UP). The
packet handling is performed by a Router.
The Router continuously looks for a packet
to be routed and keeps track of the packet
load.
The UP handles the control of the entire
Switch plane by controlling the Device Processors
(DP) located on the respective
boards in the Switching Cabinet.
The Distribution Matrix Board (DMB) terminates
four incoming SNI-4s from Devices,
and separates the traffic part of the signal
from the control information carried in
the internal overhead of the SNI-4. The
traffic signals are distributed to all the
Switching Matrix Boards (SMB) in the cabinet.
The VCB handles the separated control
information for routing. One SWC can
be equipped with up to sixteen DMBs.
The SMB is the heart of the Switch. It contains
the Switch for four outgoing SNI-4
signals. In addition, four outputs used for
expansion are located at the SMB. These
ports are used to interconnect two SWCs
when expanding the switch. Each SMB is
connected to all DMBs in the cabinet. Up
to sixteen SMBs can be accommodated in
one SWC.
Each board is equipped with a microprocessor
for board supervision (DP).
Devices
TAU 140, Figs. 6 and 7, interfaces
140 Mbit/s plesiochronous line signals according
to CCITT G.703. TAU 140 can be
set to different modes, which allows for
branching at 2, 34, and 140 Mbit/s level
and makes switching at these levels possible.
TAU 140 contains five different types of
ASIC. Together they handle CMI-decoding
of 140 Mbit/s line signals, framing and
maintenance at the 140,34,8 and 2 Mbit/s
levels, buffering and frequency justification
between line signals, synchronisation,
generation of the synchronous IVC-4
frame and sending of SNI-4 to all three
switch planes. TAU 140 has the corresponding
functionality in the transmit direction,
completed with majority vote for data
and clock signals from three switch planes.
TAU 140 contains approximately 1.5 Million
used gates, processor block with
256 kWord-PROM, 512 kWord-RAM,
DC/DC converters and a number of analog
high speed blocks.
TAU STM-1E interfaces 155 Mbit/s electric
line signals belonging to the Synchronous
Digital Hierarchy, and performs demap-
Fig.6
TAU 140
ERICSSON REVIEW No. 3.1992