On The Optimal Puncturing Design Of PS-RCPT Codes And Efficient Algorithm For The Determination Of Turbo Codes Weight Spectrum

Turbo codes have become a hotspot due to their impressive performance to approach Shannon limit from1993to the present. With the rapid development of Wireless communication, there is a higher requirement on the performance for error-correcting code, and adaptive coding scheme is needed in some communication systems to use radio resources more efficient.The weight spectrum is the basis of optimized design and performance analysis for Turbo codes. However, for long block length, the computation of weight spectrum is time-consuming. It is extremely valuable to improve the calculation efficiency of the weight spectrum in terms of both the theoretical analysis as well as the practical applications. Rate-compatible puncturing provides an effective method to realize adaptive error control coding. Therefore, the RCPT code design plays an important role in the field of error-correcting code.The coding principle of Turbo codes and some key technologies for performance analysis are presented at first. Then, the constrained subcodes algorithm is reviewed and discussed, and its advantage and disadvantage are given. Base on the previous analysis, an improved algorithm for the determination of Turbo codes weight spectrum called Span-Span algorithm is proposed. As an example, the improved algorithm is applied to the determination LTE standard Turbo codes. It is validate that the Span-Span algorithm can obtain exactly the first three terms of weight spectrum for Turbo codes, and for the most long block length(lager than928), the searching time of Span-Span algorithm is only about half of the constrained subcode algorithm, that means Span-Span algorithm is more efficient than constrained subcode algorithm.Furthermore, in this paper, the key factor for optimized design of PS-RCPT codes is discussed. Two design constraints are proposed to avoid significant performance degradation in the decoding convergence for PS-RCPT codes. Two algorithms based on OWSS criterion are given respectively to determine the optimal periodic puncturing pattern and non-periodic puncturing pattern for PS-RCPT codes. It has been proved that the optimized PS-RCPT codes can achieve better error floor performance than S-RCPT codes at the cost of some degradation in the decoding convergence within waterfall region. In addition, the OWSS-criterion based PS-RCPT codes are superior to the pseudo-random puncturing (PRP) based PS-RCPT codes. Meanwhile, it is unveiled that, the puncturing ratio of information bits should be carefully determined in PS-RCPT codes generation to achieve reasonable tradeoff between the waterfall region and the error floor region performance. Furthermore, PS-RCPT codes with longer puncturing period can obtain better performance. In a word, the OWSS based puncturing pattern design provides an effective alternative of generating adaptive Turbo coding scheme to satisfy the performance requirement of diverse applications.