CDM-625 Advanced Satellite Modem
Revision 1
Clock Modes and Drop and Insert (D&I)
MN-0000036 (Ref MN/CDM625.IOM)
9–6
9.5
Drop and Insert
The Drop and Insert (D&I) multiplexer works in conjunction with the G.703 interfaces to enable
the modem to transmit or receive fractional parts of a T1 or E1 data stream.
The D&I option provides fully compliant baseband processing in accordance with Intelsat
IESS
-
309 for the terrestrial information rate of 2048 kbps (E1) and 1544 kbps (T1), using G.703
interfaces. The data rate sent over the satellite link is n x 64 kbps. See the Frame Formats diagram
for the permissible values of n. The modem provides the interface to transmission level framing
compliant to IESS
-
309 Data Type 2.
9.6
Frame Formats
The E1 and T1 frame formats that are supported are shown in
Figure 10-3
:
Figure 9-3. Supported T1 and E1 Framing formats
Note that, for D&I++, the smaller overhead frame structure does not support CAS signaling,
although E1 timeslot 16 may still be one of the channels transmitted.
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E1-CCS (Common Channel Signalling)
2048 kbps E1 Frame Maximum channels to drop = 30 = 1920 kbps n x 64 kbps, n = 1,2,3,4,5,6,8,10,12,15,16,20,24,30
Time
Slot
No.
Time
Slot
No.
Reserved for
Framing
Reserved for
Framing
May be reserved for Signalling. All signalling
information is common to all 30 TS and no signalling is
transmitted
.
Reserved for Signalling. All signalling is transmitted
for TS's dropped in IBS overhead (500Hz per TS)
Signalling information in TS 16 is associated to
specific TS's.
E1-CAS (Channel Associated Signalling)
2048 kbps E1 Frame Maximum channels to drop = 30 = 1920 kbps n x 64 kbps, n = 1,2,4,6,8,12,16,24,30
Time
Slot
No.
Time
Slot
No.
T1-ESF (Extended Super Frame)
1544 kbps T1 Frame 24-Frame multi-frame structure. No IBS multi-frame signalling will be transmitted.
Maximum channels to drop = 24 = 1536 kbps n x 64 kbps, n = 1,2,3,4,5,6,8,10,12,15,16,20,24
T1-D4 (D4 Framing)
1544 kbps T1 Frame 12-Frame multi-frame structure. No IBS multi-frame signalling will be transmitted.
Maximum channels to drop = 24 = 1536 kbps n x 64 kbps, n = 1,2,3,4,5,6,8,10,12,15,16,20,24
