The algorithm for channel test patterns like 2047 and 2E15-1

The algorithm for channel test patterns like 2047 and 2E15-1
NewsGroups | Search | Tools
User Password
Register Now! Lost Password?
 comp.dcom.telecom.tech  Post an article  get this group's latest topics as an RSS feed add this group's latest topics to your My MSN content add this group's latest topics to your My Yahoo content  add this group's latest topics to your Google content  YahooMyWeb Yahoo!  Google Google  Windows Live Favorites Windows Live  del.icio.us del.icio.us  digg digg  Add to Netscape Netscape
Subject Author Date
The algorithm for channel test patterns like 2047 and 2E15-1 Perdition 09-01-2005
Posted by Perdition on September 1, 2005, 9:46 am
If you were  Registered and logged in, you could reply and use other advanced thread options


I want to learn these patterns for BERT, thing is i'm told by a site
that they are pseudorandom sequences based on an 11 and 15 bit shift
register, respectively. That doesn't explain the actual algorithm
though :S could someone clear it up for me as well as explain what
sequence of bits is used and why? thanks alot in advance :)
oh and is the same algorithm also valid for 2E20-1, 2E23-1 and so on
for 20 and 23 bits?



Pure Networks
Posted by Bill Matern on September 7, 2005, 3:06 pm
If you were  Registered and logged in, you could reply and use other advanced thread options


Check out the ITU I.150 series.

Bill Matern
wtm at ncomm dot com

====
NComm provides complete software solutions, including the device driver, for
the physical layer requirements of T1, E1, T3, E3 and SONET/SDH including
APS.

> I want to learn these patterns for BERT, thing is i'm told by a site
> that they are pseudorandom sequences based on an 11 and 15 bit shift
> register, respectively. That doesn't explain the actual algorithm
> though :S could someone clear it up for me as well as explain what
> sequence of bits is used and why? thanks alot in advance :)
> oh and is the same algorithm also valid for 2E20-1, 2E23-1 and so on
> for 20 and 23 bits?
>




Posted by on September 8, 2005, 7:55 am
If you were  Registered and logged in, you could reply and use other advanced thread options



Perdition wrote:
> I want to learn these patterns for BERT, thing is i'm told by a site
> that they are pseudorandom sequences based on an 11 and 15 bit shift
> register, respectively. That doesn't explain the actual algorithm
> though :S could someone clear it up for me as well as explain what
> sequence of bits is used and why? thanks alot in advance :)
> oh and is the same algorithm also valid for 2E20-1, 2E23-1 and so on
> for 20 and 23 bits?

There is a bit of an explanation of a number of test code algorithms in
ATIS Technical Report # 25, although it's a little tough to get your
hands around, too.

The basic "Linear Feedback Shift Register" (LFSR) technique is used to
both generate AND detect all of these "PRBS" type patterns, which
differ from each other primarily in the number of stages used and the
feedback points.

Here's a simplified overview of LFSR operation:

http://en.wikipedia.org/wiki/Linear_feedback_shift_register

The "feedback" aspect means that a taps are taken from selected
flip-flops in the shift register, and Exclusive-ORed back to the input
of the first flip-flop.

To get an idea of the complexity that can be obtained with LFSRs, ATIS
TR #25 states that the commonly-used QRS pattern consists of a PRBS
with a 20-stage shift register with a constraint that forces the "put
to a one" when the next 14 bits in the sequence would be zeros. The QRS
generates every combination of 20-bit words, repeats every 1,048,575
bits, and contains high density sequences, low density sequences, and
sequences that change from low density to high density and vice versa.

- Steve Pinkston
Kentrox



Similar ThreadsPosted
Channel slot mapping uses three bytes or up to three bytes in Channel ID? September 19, 2005, 3:27 am
algorithm for handling outgoing calls February 21, 2005, 11:22 pm
Dialogic Cards Causing ISDN Channel Lockout? November 18, 2005, 11:56 am
AT&T AHG31 Asynchronous Serial Interface Card used in a D4 Channel Bank June 15, 2005, 12:07 pm
NEW TEST NUMBER :-) January 12, 2006, 9:50 am
homemade test set March 15, 2006, 10:16 pm
Test Simulator for GDI (SR-3389) April 12, 2006, 6:03 pm
isdn test set needed August 30, 2006, 10:01 pm
Test INNUA user group form November 2, 2005, 3:45 pm
Surplus Fiber optic and test equipment. May 7, 2008, 2:05 pm

other useful resources:
The Federal Communications Commission (FCC)
Telecommunications Industry Association
Electronic and Software Security Products and Services
International Telecommunication Union

Custom CGI Perl and PHP programming by 1-Script.com

Contact Us | Privacy Policy
The site map in XML format XML site map