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OmniAccess 5740 Unified Services Gateway CLI Configuration Guide
Alcatel-Lucent
MECHANISMS SUPPORTED BY THE E1 INTERFACE
In order to provide a reliable and accurate service, the E1 interface supports
several mechanisms for synchronization, error correction and detection,
management and performance messages and signaling.
These mechanisms and their way of operation are explained in the following
sections.
T
HE SYNCHRONIZATION MECHANISM
To verify that the received bits are mapped to the correct channels, a
synchronization mechanism is activated. This mechanism is independent of any
clock, and does not synchronize the clocks. Clock recovery is achieved by the
shape of the signal.
The synchronization information is carried in the TS0 of every even frame. Such a
frame is called "Frame Alignment Signal (FAS)”. An FAS carries the unique
pattern 0011011 (bits 1 - 7), that specifies the alignment of the frame.
T
HE SIGNALING MECHANISM
Signaling mechanisms provide a wide range of functions and their protocol is
application specific. Two modes of signaling are employed, namely:
• Common Channel Signaling (CCS) - In this mode of operation one or more
channels of 64 kbit/s are dedicated for signaling and the information carried in
them asynchronously serves all other channels. TS16 is usually used for this
purpose.
• Channel Associated Signaling (CAS) - In each Multiframe, each channel has a
predetermined frame. In this frame, half of TS16 is dedicated for this channel
signaling information.
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