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 PRB S 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 s hows the
payload sizes generated at various ra tes:
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 x5 + x4 + x2 + x1 + x0
PRBS 7 127 bits x7 + x6 + x0, inverted
PRBS 9 511 bits x9 + x5 + x0
PRBS 11 2,047 bits x11 + x9 + 1, not inverted as CCITT 0.152
PRBS 15 32,767 bitsax15 + x14 + 1, inverted, as CCITT 0.151
PRBS 20 1,048,575 bitsbx20 + x17 +1, not inverted as CCITT 0.151
PRBS 23 8 388,607 bitsc x23 + x18 +1, inverted, as CCITT 0.151
PRBS 31 2,147,483,657
bitsc
X31 + X28 + x0
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.