RE: what is a "valid SOH"?
Here are my comments about the "valid SOH "
In order to detect " Line AIS in a STS-N signal" bit 6,7,and 8 of K2 is
processed for value "111". In order to find the K2 byte in WIS frame the
frame allignment should be performed first.We need not to check whole 192 A1
and 192 A2 bytes of STS-192 frame.
Here is some other SONET standard cross reference for frame allignment and
related alarm detection criteria.
GR-253-CORE specify the conditions for preventing the false receive out of
frame detection against bit errors.
Severe errors frame defect is not detected more than an average of once
every 6 minutes with BER of rate 10^-3. Refer to section 5.5 R5-224 of
The probability for False frame recovery from OOF should be no more than 10
^-5 per 2 frames as per ETS 300 417-2-1.
In order to meet this criteria, We need to search for sub-set of A1 and A2
bytes for frame alignment. Once we have frame synchronization the other
overhead bytes are valid "valid SOH"
Please let me know if there is any feedback.
From: Frank Moore [mailto:fmoore@xxxxxxxxxxxx]
Sent: Monday, May 21, 2001 1:08 PM
Subject: what is a "valid SOH"?
I am working on the AIS-L detection logic of a WIS module. Clause
220.127.116.11.5 states "The AIS-L functionality implemented by the WIS is
described in 18.104.22.168 and defined fully in Section 7.4.1 of ANSI
ANSI T1.416-1999 states "Line AIS is a STS-N(c) signal containing a
valid SOH with bits 6,7 and 8 of the K2 byte set to 111, and a scrambled
all-ones pattern for the remainder of the signal"
My question is what consistutes a "valid SOH" for a WIS frame. Do I need
to verify 192 A1s followed by 192 A2s or do I just verify that the sync
point happened correctly (ie A1/A2 at byte 192/193). Do I need to verify
that the Z0s are all 0xcc? Do I need to check that all of the unused
bytes are 0x00?
I guess AIS-L doesn't seem so fully defined to me :)
Sr. Staff Engr.
Mitsubishi Electric & Electronics
Durham, NC 27713