FlexDSL ORION 2 - AIS Generation (Alarm Indication Signal); CRC4 (Cyclic Redundancy Check); Transparent and ITU-T G.704

User Manual NTU Orion 2
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3.3.2.2.1 Transparent and ITU-T G.704
In the transparent mode, the E1 data will be transmitted over the DSL without any changes. The
transparent mode is only possible for transmission rates of no less than 2056 Kbit/s
when transmitting one E1 stream in this mode and of no less than 4104 Kbit/s when
transmitting both E1 streams in this mode.
In the G.704 mode (framing according to ITU-T G.704), the E1 data stream is processed by the
E1 framer, which is incorporated in the block of E1 network interfaces. In this case, from 1 to 32
time slots of the corresponding E1 stream can be transmitted over the DSL line.
The G704 OFF/ONN command (the Configuration management menu) is used to
enable/disable the Transparent/ITU-T G.704 modes.
3.3.2.2.2 CRC4 (cyclic redundancy check)
The CRC4 mode enables the error performance monitoring of the E1 network interface with the
help of a cyclic redundancy check.
If the mode is enabled, the modem synchronizes with CRC4 sub-multiframes at the E1 output
and displays information about CRC errors. In this case the modem regenerates E1 CRC4 sub-
multiframes and checksum words in the outgoing E1 stream.
If the mode is disabled, the modem transmits transparently CRC4 sub-multiframes and
checksum words in the case if the generation of the zero time slot is deactivated. If the TS0GEN
mode is activated, the zero time slot is generated without CRC4 sub-multiframes and checksum
words.
3.3.2.2.3 AIS Generation (alarm indication signal)
If this mode is enabled, AISs will be transmitted to the E1 side under the following conditions:
• the loss of the line signal from the remote device or loss of frame alignment on the DSL
side;
• the remote device receives an AIS over E1 interface, which is configured to transmit data
from E1 to DSL. This mode is enabled if only the AIS Detection mode is enabled on the
remote device (see below). If modems (A and B) transmit two E1 streams, then if AIS is
received over the first E1 channel of the A modem, in the B modem the AIS will be
generated over the first channel. And if AIS is received over the second E1 channel of the A
modem, in the B modem the AIS will be generated over the second channel.
The AISGEN ON/OFF command (the Configuration management menu) is used to
enable/disable the AIS Generation mode.
Warning! If the AIS Generation mode is disabled, the signal at the output of the E1 interface will
be absent in the case of losing communication in the DSL line (except for time slots of this
interface dedicated to carry Ethernet data).
Warning! If a part of time slots of one of E1 network interfaces is used to transmit Ethernet
data, AISs will not be generated for this interface.