Codeword Structure Analysis for LDPC Convolutional Codes
Abstract
:1. Introduction
2. LDPC Convolutional Codes
3. Codewords Analysis
3.1. Structured Codewords
Submatrices | Permanent of the Submatrix |
---|---|
3.2. Non-Structured Codewords
Structured | Non-Structured | Structured |
- | non-structured | |
- | ||
- | - |
4. Eliminating the Low Weight Non-Structured Codewords
4.1. More Examples
4.2. Improved Distance Spectrum
4.3. Rules for Designing Practical LDPC-CCs
- ensuring that each super code does not contain any codewords with weight smaller than the minimum weight of the structured codewords calculated using Lemma 1;
- eliminating the low weight non-structured codewords of the super codes as many as possible.
- Step 1: Compute the enumerator for the structured codewords that the super code contains. In this paper, the structured codewords are calculated based on the formation of the unavoidable cycles [21]. For example, the weight matrix of the super code formed by the second and the third columns of Equation (12) is an all-one matrix of size . According to the result in [21], this weight matrix contains = 10 unavoidable cycles of length 12. If an all-one weight matrix contains only two columns or two rows, the structure of an unavoidable cycle of length n in the weight matrix forms a structured codeword of weight . Hence, we have for the super code formed by arbitrary two columns of Equation (12).
- Step 2: For each entry in the polynomial syndrome former matrix of the super code, we randomly choose a monomial with power smaller than the syndrome former memory and calculate the number of the codewords that the associated super code has. If it is larger than , this monomial is replaced by another one until a valid one is found. If all of the monomials with power smaller than have been tested, we simply increase the value of and repeat the process in Step 2.
5. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
Appendix
A. Proof of Lemma 1
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Zhou, H.; Feng, J.; Li, P.; Xia, J. Codeword Structure Analysis for LDPC Convolutional Codes. Information 2015, 6, 866-879. https://doi.org/10.3390/info6040866
Zhou H, Feng J, Li P, Xia J. Codeword Structure Analysis for LDPC Convolutional Codes. Information. 2015; 6(4):866-879. https://doi.org/10.3390/info6040866
Chicago/Turabian StyleZhou, Hua, Jiao Feng, Peng Li, and Jingming Xia. 2015. "Codeword Structure Analysis for LDPC Convolutional Codes" Information 6, no. 4: 866-879. https://doi.org/10.3390/info6040866
APA StyleZhou, H., Feng, J., Li, P., & Xia, J. (2015). Codeword Structure Analysis for LDPC Convolutional Codes. Information, 6(4), 866-879. https://doi.org/10.3390/info6040866