# RE: [802.3ae] WIS test Pattern PRBS Generator Polynomial

Bruce,
The PRBS for the mixed-frequency test pattern indeed uses a 2**23 -1 polynomial. This is explicitly described in the WIS clause (see lines 39-41 and 47-48 of page 397, lines 9-13 of page 398, and Figure 50-13 (payload field) on page 398). All these refer to Draft 4.0.
Note that in the next draft of the WIS spec, there is a new (optional) additional test pattern introduced, as per the resolution of Comment #72 against Draft 4.0; this pattern uses a 2**31 -1 polynomial.
Thanks,
- Tom Alexander
WIS Scribe
-----Original Message-----
From: Nepple, Bruce [mailto:bnepple@xxxxxxxxxxxxxxxxxxx]
Sent: Friday, February 01, 2002 9:36 PM
To: stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
Subject: [802.3ae] WIS test Pattern PRBS Generator Polynomial
I could find no definition of the WIS test Pattern PRBS generator polynomial in Clause 50 (or any other clause, for that matter). I did find a reference to O.172 and in O.172 I found a reference to O.150, and in O.150 I found a definition for a 2**23 -1 length PRBS. (Section 5.6). Is that the required generator for WIS? Is there a reason that it is not specified? Or, did I just manage to overlook it in the specification? (wouldn't be the first time).
O.150 Section 5.6 specifies a 23 stage shift register with taps from stage 23 and stage 18 added (mod-2) and applied to the first stage. (I'd call it a x**23 + x**18 + 1 generator with input data = 0, but I'm not a math dude)
Bruce