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CDM-625 Advanced Satellite Modem
Clock Modes and Drop and Insert (D&I)
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
9.6
Frame Formats
The E1 and T1 frame formats that are supported are shown in Figure 10-3:
E1-CCS (Common Channel Signalling)
2048 kbps E1 Frame
1
2
3
4
Time
0
1
2
3
4
Slot
No.
Reserved for
Framing
E1-CAS (Channel Associated Signalling)
2048 kbps E1 Frame
1
2
3
4
Time
0
1
2
3
4
Slot
No.
Reserved for
Framing
T1-ESF (Extended Super Frame)
1544 kbps T1 Frame
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
1
2
3
4
5
Time
1
2
3
4
5
Slot
No.
T1-D4 (D4 Framing)
1544 kbps T1 Frame
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
Time
1
2
3
4
5
1
2
3
4
5
Slot
No.
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.
309 Data Type 2.
-
Maximum channels to drop = 30 = 1920 kbps
5
6
7
8
9
10 11 12
5
6
7
8
9
10 11 12
Maximum channels to drop = 30 = 1920 kbps
5
6
7
8
9
10 11 12
5
6
7
8
9
10 11 12
24-Frame multi-frame structure. No IBS multi-frame signalling will be transmitted.
6
7
8
9
10 11 12 13
6
7
8
9
10 11 12 13
12-Frame multi-frame structure. No IBS multi-frame signalling will be transmitted.
6
7
8
9
10 11 12 13
6
7
8
9
10 11 12 13
Figure 9-3. Supported T1 and E1 Framing formats
n x 64 kbps, n = 1,2,3,4,5,6,8,10,12,15,16,20,24,30
13
14
15
16
17
18 19 20 21
13
14
15
16
17
18
19 20 21 22
May be reserved for Signalling. All signalling
information is common to all 30 TS and no signalling is
transmitted.
n x 64 kbps, n = 1,2,4,6,8,12,16,24,30
13
14
15
16
17
18 19 20 21
13
14
15
16
17
18
19 20 21 22
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.
14
15
16
17
18
19
20 21 22 23
14
15
16
17
18
19
20 21 22 23
14
15
16
17
18
19
20 21 22 23
14
15
16
17
18
19
20 21 22 23
9–6
MN-0000036 (Ref MN/CDM625.IOM)
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23
24
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Revision 1
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