Basic Node
start and short circuit protection, filter function, low voltage protection, DC/DC
converter and a pre-charge function.
3.5.3.2.5 Line Interface
This block provides the E1 line interfaces for external connection.
3.6 SDH Traffic
3.6.1 Overview
The SDH portfolio consists of the SDH modems MMU2 E/F 155 and the SDH
termination units LTU 155 and SXU3 B.
These modems and traffic termination units together support a variety of
applications:
• For a pure point-to-point SDH microwave connection the STM-1 can be
connected directly to the front of the modem.
• The LTU 155 Terminal Multiplexer terminates one STM-1 with 63xE1 (or
21xE1) mapped asynchronously into 63xVC-12 (or 21xVC-12) depending
on the type of LTU 155. The E1s are available at the TDM bus for traffic
routing to other plug-in units. See Section 3.6.2 on page 30.
At aggregation nodes the LTU 155 acts as an interface between the
optical domain and the microwave domain by providing an effective
optical northbound interface using one STM-1 connection instead of
nxE1 interfaces.
In ring configurations two LTU 155s can be connected “back-to-back”
to allow local add/drop of up to 63xE1.For ring configuration, see also
SXU3 B.
The LTU 155 is also used if all incoming SDH radio traffic on MMU2
E/F 155 shall be connected to the TDM bus as 63xE1s.
The LTU B 155 acts as an interface towards 3G radio base stations for
transmission of up to 21xE1 over channelized STM-1 interface.
• SXU3 B is an SDH Add-Drop Multiplexer and supports Ethernet over SDH
and PDH over SDH, see Section 3.6.3 on page 32.
SXU3 B supports SDH microwave rings with up to 21xE1 add/drop in
each node.
SXU3 B can aggregate partially filled STM-1s into one full northbound
STM-1
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