# LabVIEW

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## 511 pseudorandom generator

I'm kinda new to pseudorandom generator.  Just wondering how do I generate a 511 pattern based on the V.52 specification:

511 (2^9-1) which is a PN 9

Primitive Polynomial: x^9+x^4+x^1=0

Shift Register Taps: Q9 xor Q5

How do I translate the polynomial and shift register taps to Seed or initial input state?  Are there any examples out there I can loook at?

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## Re: 511 pseudorandom generator

Hi lavalava,

I’m also new to the concept of pseudorandom generation, but, I might be able to help you if I can understand completely what you are trying to do. I understand that pseudorandom generation is related to the generation of “random” numbers that follows a specific sequence, I would be more than happy to  help you with a more detailed information of your algorithm and your specific goal, and we can work in a code that actually works as you expect it to work.

I looked at ni.com/code and I found this example, this is for LabVIEW FPGA so I’m not sure if this will work for your application but maybe this could be a start.

Regards,

steve.bm
AE | NI
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## Re: 511 pseudorandom generator

Thanks, Steve.

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Solution
Accepted by topic author lavalava

## Re: 511 pseudorandom generator

I don't know what standard you're refering to (v.52) and cannot open Steve link so this may be redondant (and should be validate with the standard). Hope this help.

note, i did not find any sequence to validate this and it might need a bit of tweeking.

Ben64

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## Re: 511 pseudorandom generator

Thanks, Ben.  I'm more farmilar with it now.  It turns out, this isn't so bad afterall.  It's actually pretty easy to comprehend.  As a matter of fact, the modulation toolkit even comes with a primitive polynomial driven generator too.  My only issue at this point is trying to figure out the seed or the initial condition of the PN generator.  And that V.52 is based on some ancient commercial specifications that Acterna uses (please take a look at the attachment).  Anyone who uses the Fireberd or any communication analyzer products at the greater level would probably know more about it than I do.  I just use them to run tests but that's about it.  Now, I would like to explore it at a greater level.  I really need to figure out the initial PN sequence or I won't be able to decode the data pattern properly.  Acterna is pretty helpful most of the time, except for this subject.

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## Re: 511 pseudorandom generator

V.52 has been superceeded by O.153. Look at paragraph 2.1 the explanation is pretty clear. Attached is the modified version of my vi.

Ben64

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## Re: 511 pseudorandom generator

Here is the Fireberd 6000A 511 pattern:

This appears to be repeating every 7x511 bytes, then the pattern starts all over again instead of at every 511 like it stated in o.153 spec.

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## Re: 511 pseudorandom generator

The sequence you're showing must be wrong, by definition a PN9 sequence has a lenght of 511 bit (not byte). Are you sure your setting the Fireberd correctly?

Ben64

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## Re: 511 pseudorandom generator

Yes, if you send this pattern back into the fireberd it will show it as no bit error.

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## Re: 511 pseudorandom generator

@lavalava wrote:

Yes, if you send this pattern back into the fireberd it will show it as no bit error.

That doesn't mean that the sequence sent was the 511 pattern. It just mean that the received sequece match the sent sequence.

The Fireberd manual specify that the 511 pattern has a maximum of 10 sequential zeroes and 11 sequential ones. In the hex data you posted you can find the following sequence 7FF E (end of first line beginning of second one) which contains 14 consecutive ones and 800 2 which contains 13 consecutive zeroes so this definatly cannot be a 511 pattern.

Ben64

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