Chaoshi Cai
Communication University of China

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A NOVEL DECODING ALGORITHM FOR BICM-ID EMBEDDED TURBO CODES Wang, Jian; Li, Jianping; Cai, Chaoshi
Indonesian Journal of Electrical Engineering and Computer Science Vol 12, No 5: May 2014
Publisher : Institute of Advanced Engineering and Science

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Abstract

Bit-interleaved coded modulation iterative decoding (BICM-ID) embedded turbo code is widely used in wireless communication because of its excellent performance. This paper proposes an improved logarithmic maximum a posteriori (Log-MAP) algorithm for BICM-ID embedded turbo codes. It can yield excellent bit error rate (BER) performance with much lower complexity. The proposed algorithm exploits a linear interpolation and Least Squares approximation function to replace the logarithmic correction in the Jacobian logarithmic function, which avoids complicated logarithm look-up table operations in Log-MAP algorithm. Simulation results show that the novel algorithm can offer almost equivalent performance to the optimal algorithm with much less computation. Compared with the improved MAX-Log-MAP algorithm proposed by Talakoub, the proposed algorithm can reduce about 36% of computational complexity, meanwhile it achieves 0.1db-0.16db performance gains. In addition, it obtains 0.35-0.4db gains than MAX-Log-MAP algorithm. DOI : http://dx.doi.org/10.11591/telkomnika.v12i5.4596
AN IMPROVED TONE RESERVATION SCHEME IN OFDM SYSTEMS FOR ADAPTIVE AMPLITUDE CLIPPING Song, Yang; Cai, Chaoshi; Li, Jianping
Indonesian Journal of Electrical Engineering and Computer Science Vol 12, No 11: November 2014
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v12.i11.pp7758-7763

Abstract

Orthogonal frequency division multiplexing(OFDM) suffers from a high peak to average power ratio(PAPR).  Tone reservation (TR) technology is considered as one of the most promising methods because of no additional distortion, no side information, and low implementation cost. However, in all PAPR reduction schemes?determining the optimal target clipping level is difficult. In this paper, we consider an adaptive amplitude least squares approximation(AALAS-TR) algorithm. Adjust adaptive optimal convergence factor for initial clipping threshold. That is results an approximately PAPR reduction performance with a low computational complexity. Simulation results show that the proposed algorithm can achieve better PAPR reduction as that different clipping threshold .
TWO NOVEL DECODING ALGORITHMS FOR TURBO CODES BASED ON TAYLOR SERIES IN 3GPP LTE SYSTEM Wang, Jian; Li, Jianping; Cai, Chaoshi
Indonesian Journal of Electrical Engineering and Computer Science Vol 12, No 5: May 2014
Publisher : Institute of Advanced Engineering and Science

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Abstract

This paper proposes two novel methods to simply Logarithmic Maximum a posteriori (Log-MAP) algorithm for turbo codes in the Third Generation Partnership Project Long Term Evolution (3GPP LTE). Firstly, we exploit a new function to replace the logarithmic term in the Jacobian logarithmic function based on Taylor series, which has the best approximated accuracy compared with the existing methods. With this method, we get algorithm I. Secondly, to further simplify the complexity, we propose a new piece-wise ladder function to approximate the logarithmic term according to algorithm I. In this way, we obtain algorithm II.  Simulation results show that the performance of the algorithm I is most close to the optimal algorithm. Algorithm II owns the complexity which is similar to the MAX-Log-MAP algorithm, meanwhile it can offer 0.37-0.4db performance gains than MAX-Log-MAP algorithm. DOI : http://dx.doi.org/10.11591/telkomnika.v12i5.2547