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For information on testing E3 links
The E3 interface operates at 34.368 Mbps
over coax cables, compliant with ATM Forum UNI specifications.
It supports both PLCP and direct cell mapping and complies with
the following standards: G.751, G.832. The interface has BNC
connectors.
Direct Mapping
The E3 frame structure when direct mapping
is employed is illustrated in the following diagram. The 530
octet payload consists of 59 columns and 9 rows. The 53 byte
ATM cell wraps around the 59 bytes of the E3 frame. There is
no relationship between the start of a direct mapping frame
and the start of the ATM cell.
FA1 |
FA2 |
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EM |
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TR |
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MA |
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NR |
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GC |
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<---------------------------------------------------------------------------------> |
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530 Payload bytes |
| The 53 byte ATM cell is
represented as follows: |
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| <--------------------------------------------------------------------------------------------> |
| 53 bytes |
E3
frame structure - direct mapping |
FA1
Frame Alignment 1.
FA2
Frame Alignment 2.
EM
Error Monitor, BIP-8.
TR
Trail Trace.
MA
Maintenance and Adaptation.
NR
Network Operator.
GC
General Purpose Communications Channel.
PLCP Cell Mapping
The E3 PLCP frame provides the transmission
of 9 ATM cells every 125 m sec. The net transmission rate is
thus 3.456 Mbytes/sec. The PLCP frame is octet aligned to the
16 overhead bits in the ITU-T Recommendation G.751 E1 frame.
There is no relationship between the start of the PLCP frame
and the start of the E3 frame. A trailer is inserted at the
end of each PLCP frame.
| A1 |
A2 |
P8 |
Z3 |
ATM Cell |
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| A1 |
A2 |
P7 |
Z2 |
ATM Cell |
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| A1 |
A2 |
P6 |
Z1 |
ATM Cell |
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| A1 |
A2 |
P5 |
F1 |
ATM Cell |
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| A1 |
A2 |
P4 |
B1 |
ATM Cell |
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| A1 |
A2 |
P3 |
G1 |
ATM Cell |
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| A1 |
A2 |
P2 |
M1 |
ATM Cell |
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| A1 |
A2 |
P1 |
M2 |
ATM Cell |
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| A1 |
A2 |
P0 |
C1 |
ATM Cell |
Trailer |
| <---> |
<---> |
<---> |
<---> |
<--------------------------> |
<------------------------> |
1 |
1 |
1 |
1 |
53 bytes |
17-21 bytes |
| E3
frame structure - PLCP cell mapping |
A-bits
Framing pattern octet.
P-bits
Path overhead identifier.
C1
Pad bit counter.
M-bits
SIP layer 1 management information.
G1
PLCP path status.
B1
Bit-interleaved parity 8 (BIP-8).
F1
PLCP path user channel.
Z-bits
For future use.
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