cx29600 Mindspeed Technologies, cx29600 Datasheet - Page 73

• Manufacturer Part Number: cx29600
• Description: Optiphytm - M155 Sts-3 Sonet/sdh Multiplexer
• Manufacturer: Mindspeed Technologies

CX29600
CX29600 Data Sheet
Table 2-16. Bit Error Rate Analysis for STS-3
29600-DSH-001-B
2.4.3.5 APS Threshold
10
BER
10
10
10
10
10
10
10
2.4.3.7 Minimum
-10
-3
-4
-5
-6
-7
-8
-9
2.4.3.8 Frames
2.4.3.6 BER
Observation
Observed
Observation
Minimum
10
10
10
10
10
10
10
10
10
11
4
5
6
7
8
9
The Bit Error Rate (BER) is monitored from the B2 BIP error count. If the
incoming error rate exceeds the thresholds programmed in the APSTHRESH
register, then signal degrade or signal fail status will be reported in RXAPS bits 0
or 1, respectively.
exponent into a control register. The circuitry configures observation window
lengths and error count thresholds directly from the programmed BER exponent.
As stated in Network node interface for the synchronous digital hierarchy (SDH),
ITU-T Recommendation G.707 (03/96) and Synchronous Optical Network
(SONET) Transport Systems: Common Generic Criteria, Bell Communications
Research, GR-253-CORE, to estimate a given BER, at least 10/BER bits need to
be observed to state with 95% confidence that the estimated BER is within a
factor of 2 of the actual BER. If more bits are observed, the estimate is closer for
the same confidence level or the confidence in the estimate is tighter for the same
estimate accuracy. This criteria is true if the BER is low or the number of bits
observed is large (because the binomial error distribution can be assumed to be
approximated by the Poisson distribution in this case). The observation windows
are set in terms of the number of STS-3 frames. The Line BIP (B2) byte covers
19,224 bits (2403 octets) per STS-3 frame. The table below shows the parameters
for each BER threshold.
This column lists the thresholds that can be programmed into the control register
(10
the table because the criteria for clearing an SD or SF alarm is that the BER must
drop to 1/10 of the set threshold.
This column shows the number of bits that must be observed to have a 95%
confidence that the estimated BER is within a factor of 2 of the actual BER.
This column shows the number of frames that the circuit observes based on the
BER threshold. This was picked as the power of 2 (for ease of counter
implementation) that gives a number of bits observed greater than the minimum
observation requirement. Substantially more bits are observed at the 10
threshold than are necessary to keep the Poisson distribution assumption intact.
8
16
128
1024
16384
131,072
1,048,576
8,388,608
-3
The CX29600 can detect BERs in the range 10
Observed
Frames
to 10
Mindspeed Technologies
-9
) for setting the SD or SF alarm. The 10
1.54 x 10
3.08 x 10
2.46 x 10
1.97 x 10
3.15 x 10
2.52 x 10
2.02 x 10
1.61 x 10
Actual Bits
Observed
5
5
6
7
8
9
10
11
Threshold
Error
150
30
23
18
30
24
18
16
2.4 SONET/SDH Framer and Overhead Processor
™
1 msec
2 msec
16 msec
128 msec
2.048 sec
16.384 sec
131.072 sec
1048 sec
Detect Time
Threshold
-3
-10
to 10
threshold is included in
2.0 Functional Description
-9
by programming the
8 msec
13 msec
100 msec
1 sec
10 sec
83 sec
667 sec
—
Requirement
APS Switch
-3
2-29