7/8 LDPC channel decoding

[scnsRF]

Hi,

 I'm considering approaching my boss for a copy of the modulation toolbox but I need to determine if it will suit our needs before doing so.

 We have recently installed some receivers in support of a new satellite coming on line (proposed launch June,2013) that utilizes the CCSDS 131.1-O-2 recommendation for LDPC encoding and decoding. The RF-ICD specifies a base( 8160,7136) 7/8 rate code with a LDPC codeword message area of 892 octets and a 1024 octet parity.

Will the modulation toolbox allow me to assemble a simulator and decoder that will meet these parameters?

Thanks in advance,

 Mike  

[JVP]

Hello Mike,

To evaluate the NI Modulation Toolkit please see the following link:

http://digital.ni.com/demo.nsf/websearch/503ecadcb8968c96862579290053a7ef?opendocument

Best Regards,

Jignesh P

[andrewd220]

What did you end up doing with this if you don't mind me asking? =D

I'm downloading the modulation toolkit now but I'm guessing there isn't a 7/8 ldpc decoder contained in it.

[JVP]

Hello,

If you take a look at the Modulation Toolkit Shipping Examples Developer Zone article you will find all the encoding and decoding examples. LDPC is actually in the list of examples.

Best Regards,

Jignesh P

Applications Engineer

[KittF]

The LDPC in the Modulcation Toolkit does not allow for even weighting (j must be odd).  Many LDPC encoders are even weighted, with 4 being common (two 1's per row, two 1's per column). Standard CCSDS LDPC Encoding and Decoding, specifically the (8160, 7136) flavor in linked spec, is one of these. http://public.ccsds.org/publications/archive/131x1o2e2.pdf

Questions: Why must j be odd?  Is this a limitation in the algorithm NI has chosen? Is there an option for even?  Is there any means of implementing CCSDS LDPC (8160, 7136) using NI MT?

Thanks.

[lis@jiang]

Hi Nemo,

I've asked your questions to our R&D team and am waiting for an answer back.  I'm not sure that we can provide an answer for "Why must j be odd?" but we'll try to determine if even options are available.

Thanks,

Lisa

[scnsRF]

May be that the ratio (8160,7136) is a shortened code word to make up for the fact that the entire codeword ratio (8176,7156) is not an even divisible by 32?

it'll be interesting to see what the actual answer is going to be

[lis@jiang]

Just an update: Still waiting on some developers for an answer.  It's possible that the functionality for even will be incorporated in the future, but at this time, there is no timeline for such an event.

I will update with more information whenever I get that.

Thanks,
Lisa J 

[lis@jiang]

I'm still not sure why only odd values are supported, but as far as a workaround goes, can you create your own matrix rather than using the VI to generate one?

Lisa 

[andrewd220]

I've tried that and the Encode LDPC VI produces no output and no error. Just an empty data stream.