Structured Mode (Cesopsn) - Alcatel-Lucent 7210 SAS M Service Manual

the bit sequence and TDM structure in order to transport the entire signal over a PSN as a
pseudowire.

Structured Mode (CESoPSN)

Structure-aware circuit emulation is used for the transport of structured TDM, taking at least some
level of the structure into account. By selecting only the necessary n ?64 kb/s timeslots to
transport, bandwidth utilization is reduced or optimized (compared to a full DS1 or E1). Full DS1s
or E1s can be transported by selecting all the timeslots in the DS1 or E1 circuit. Framing bits
(DS1) or FAS (E1) are terminated at the near end and reproduced at the far end.
When CESoPSN with Channel Associated Signaling (CAS) is selected, the ABCD bits are coded
into the T1 or E1 multi-frame packets, transported within the TDM PW, and reconstructed in the
T1 or E1 multi-frame at the far end for each timeslot. CAS includes four signaling bits (A, B, C,
and D) in the messages sent over a voice trunk. These messages provide information such as the
dialed digits and the call state (whether on-hook or off-hook).
The mechanism for E1 CAS is described in ITU-T G.732. When configured for E1 CAS, timeslot
17 carries the signaling information for the timeslots used for voice trunking. Each channel
requires four signaling bits, so grouping 16 E1 frames into a multi-frame allows the signaling bits
for all 30 channels to be trunked.
As shown in
alignment, alarm indication, and CRC. For Frame 0, timeslot 17 is reserved for multi-frame
alignment bits. For the remaining 15 frames, timeslot 17 contains ABCD bits for two channels.
Note: For E1 CAS, timeslots are numbered 1 to 32 on the 7210 SAS.
For T1 CAS, the signaling bits are transferred using Robbed Bit Signaling (RBS), where the least
significant bit in the channel is used periodically to transport these bits instead of voice data.
T1 CAS is supported when ESF or SF framing is configured. ESF framing uses a 24-frame multi-
frame and transfers all four signaling bits (ABCD). SF framing uses a 12-frame multi-frame and
transfers only the AB bits. The signaling bits are carried in the least significant bit of the following
frames:
•
•
•
•
Table 7
multi-frame is based on 12 frames and only the A and B bits are available.
7210 SAS M Services Guide
Figure 15, timeslot 1 of all frames within the E1 multi-frame is reserved for
A bit in frame 6
B bit in frame 12
C bit in frame 18
D bit in frame 24
shows the structure of a T1 ESF multi-frame that uses RBS. The structure of a T1 SF
Virtual Leased Line Services
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