Hi, I'm Manu, one of the 5 GSoC students. I am working on LDPC codes, in parallel with Tracie, mentored by Jens. Going on is the 4th week of GSoC.
*Given below is a description of current status of the project.* I'm glad to inform that I was successful in making an out of tree module (in python) gr-ldpc which which implements encoding and decoding of LDPC codes. Some performance statistics is available here<http://home.iitb.ac.in/~manu.ts/output.txt> . The codes are available here <https://github.com/manuts/ldpc>. The code used to generate the above mentioned performance statistics is available as an example in gr-ldpc/examples/ folder. Encoder operation. --------------------------------- Encoder takes an LDPC matrix as parameter, and reduces the matrix into form [I P]. The codewords is the set of x which satisfy [I P]x = 0. A vector of length = # of columns of P is taken as data-word. Entries of data-word form the systematic part of the codeword, filling the entries corresponding to the columns of P. The entries of x corresponding to I form the parity check matrix and are formed by back-substitution. Decoder operation -------------------------------- Decoder takes an LDPC matrix as parameter. Decoder implements sum product algorithm. A decoder with likelihood messages[1] is implemented. A decoder with log-likelihood messages[2] is also implemented. On testing against predefined codes available in good error correction is observed. LDPC Code construction ---------------------------------------- Option to read LDPC code defined as "alist" file[3] is provided. Thus many predefined codes can be used with the encoder and decoder. Construction of LDPC codes based on Reed Solomon codes[4] is implemented It did not produce similar performance as the predefined code. *Goals to be achieved before midterm evaluation*. --------------------------------------------------------------------------------- Next some algorithms for construction of LDPC codes will be implemented. Namely progressive edge growth algorithm will be implemented. References ------------------------------------------------------- [1]. http://www.cs.utoronto.ca/~radford/ftp/LDPC-2012-02-11/decoding.html [2]. "Modern Coding Theory" [3]. http://www.inference.phy.cam.ac.uk/mackay/codes/alist.html [4]. "A class of Low-Density Parity-Check codes constructed based on Reed-Solomon codes with Two information symbols", IEEE communications letters, July 2003. -- Manu T S PS. I very much want to talk to you all in the coming developers call, but the proxy in my university seems to be blocking hangout. I'm working on resolving this issue.
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