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How Frames are Generated How the Frame Generator Works
Agilent 81250 ParBERT SONET/SDH Frame Generator, November 2002 15
Payload Details
The payload choices are:
All 1s, all 0s, alternate 1s and 0s, various PRBS options, a binary file
and a pattern editor.
It is important to consider the possible lengths of the PRBS with
respect to the supported frame sizes. The following table shows the
payload sizes generated at various rates:
The PRBS have the following lengths and polynomials:
The PRBS generators are initialized to all ones. The ones are shifted to
the left by the number of bits expressed by the order of the polynomial
(for example, PRBS 7:
0xffffffff << 7
).
The PRBS runs continuously and bulk-fills all payload bytes.
The payload fill starts at channel 1, row 1, column 5.
Table 1 Rates and payload sizes
Rate Payload size
STS-768 4.755.456 bits
STS-192 1.188.864 bits
STS-48 297.216 bits
STS-12 74.304 bits
STS-3 18.576 bits
Table 2 PRBS lengths and polynomials
PRBS Length Polynomial
PRBS 5 31 bits x
5
+ x
4
+ x
2
+ x
1
+ x0
PRBS 7 127 bits x
7
+ x
6
+ x
0
, inverted
PRBS 9 511 bits x
9
+ x
5
+ x
0
PRBS 11 2,047 bits x
11
+ x
9
+ 1, not inverted as CCITT 0.152
PRBS 15 32,767 bits
a
x
15
+ x
14
+ 1, inverted, as CCITT 0.151
PRBS 20 1,048,575 bits
b
x
20
+ x
17
+1, not inverted as CCITT 0.151
PRBS 23 8 388,607 bits
c
x
23
+ x
18
+1, inverted, as CCITT 0.151
PRBS 31 2,147,483,657
bits
c
X
31
+ X
28
+ x
0
a
Fits within an STS-48 frame.
b
Fits within an STS-192 frame.
c
Exceeds the STS-768 frame size, but is included to provide some longer runs.