ComStream CM601, Инструкция по установке и эксплуатации

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B-8 Internal BERT
Advanced BERT
Verification and Error
Analysis
For advanced BERT verification and troubleshooting, the CM601 BERT provides
the most reliable error analysis data when a ComStream modem is at both the
transmit and the receive ends. With ComStream modems at both ends of the
communications link, both modems are put into BERT mode. In this mode the
BERT performs a two-way error analysis in which modem A sources data to
modem B, while modem B sources data to modem A.
Troubleshooting Random Errors
For troubleshooting hard-to-find, seemingly random errors:
1. Set up a single modem to generate the 511-bit (2
9
-1) pattern while two or
more modems receive and analyze the identical IF or RF signal.
2. Determine the probable source of the errors.
If both receive modems have identical BERs, the problem probably exists
in the transmit equipment.
Different results on the receive modems indicate a potential problem with
the receive equipment.
3. Localize the problems to the appropriate equipment.
Troubleshooting External DCE Equipment
The BERT can be used to generate a known 8-bit pattern for troubleshooting DCE
equipment external to the modem. To do this, operate the modem with the BERT
generating a repeating 8-bit pattern. The resulting receive pattern can be used by a
technician performing oscilloscope or logic analyzer measurements.
Time-Based Error Analysis Measurements
To provide time-based error analysis measurements, the BERT is operated in one-
second block mode. During this test procedure, the block error rate is equivalent
to the percentage of erred seconds measurement required by many specifications.
Pattern Slip Analysis
The CM601 BERT recognizes a pattern slip as a complete loss of BERT
synchronization. If an modem loses BERT synchronization but has no other
associated faults, the most likely cause of synchronization loss is a clocking
problem.
Since the 2
9
-1 pattern in the CM601 BERT is compatible with most commercially
available error analysis equipment, a ComStream modem can generate a pattern
that can be transmitted to any compatible open network modem. The output of
this modem can then be analyzed using external error analysis devices. The
reverse setup is also a valid testing procedure.
ComStream makes no claims for equipment compatibility with any individual test
equipment manufacturer. Individual compatibility tests should be performed with
your particular test devices.