
PM5317 SPECTRA-9953 Telecom Standard Product Data Sheet
Release
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2000741, Issue 5
90
14.5 Receive Regenerator and Multiplexer Processor (RRMP)
The Receive Regenerator and Multiplexer Processor (RRMP) block extracts and process the
transport overhead of the received data stream.
The RRMP frames to the data stream by operating with an upstream pattern detector (SRLI) that
searches for occurrences of the A1/A2 framing pattern. Once the SRLI has found an A1/A2
framing pattern, the RRMP monitors for the next occurrence of the framing pattern 125 μs later.
Two framing pattern algorithms are provided to improve performance in the presence of bit
errors. In algorithm 1, the RRMP declares frame alignment (removes OOF defect) when the 12
A1 and the 12 A2 bytes are seen error-free. In algorithm 2, the RRMP declares frame alignment
(removes OOF defect) when only the first A1 byte and the first four bits of the last A2 byte are
seen error-free. In single STS-192 (STM-64) mode, the RRMP frames only on the first STS-48
(STM-16) stream. Once in frame, the RRMP monitors the framing pattern and declares OOF
when one or more bit errors in the framing pattern are detected for four consecutive frames.
Again, depending upon the algorithm either 24 framing bytes or 12 framing bits are examined
for bit errors in the framing pattern. Table 4 and Table 5 summarize these algorithms.
Table 4 A1/A2 Bytes Used for Out Of Frame Detection
SONET/SDH
Algorithm 1
Algorithm 2
STS-48/STM-16
STM-4 #1 All A1 bytes
STM-4 #4 All A2 bytes
STM-4 #1 First A1 byte
STM-4 #4 Last A2 byte
(first four bits only)
STS-192/STM-64
STM-4 #1 All A1 bytes
STM-4 #16 All A2 bytes
STM-4 #1 First A1 byte
STM-4 #16 Last A2 byte
(first four bits only)
Table 5 A1/A2 Bytes Used for In Frame Detection
SONET/SDH
Algorithm 1
Algorithm 2
STS-48/STM-16
STM-4 #1 All A1 bytes
STM-4 #1 All A2 bytes
STM-4 #1 First A1 byte
STM-4 #1 Last A2 byte
(first four bits only)
STS-192/STM-64
STM-4 #1 All A1 bytes
STM-4 #1 All A2 bytes
STM-4 #1 First A1 byte
STM-4 #1 Last A2 byte
(first four bits only)
The performance of these framing algorithms in the presence of bit errors and random data is
robust. When looking for frame alignment the performance of each algorithm is dominated by
the alignment algorithm used in the SRLI, which always examines three A1 and three A2
framing bytes. The probability of falsely framing to random data is less than 0.00001% for
either algorithm. Once in frame alignment, the RRMP continuously monitors the framing
pattern. When the incoming stream contains a 10
-3
BER, the first algorithm provides a 99.75%
probability that the mean time between OOF occurrences is 0.13 seconds and the second
algorithm provides a 99.75% probability that the mean time between OOF occurrences is 7
minutes.