Improving irregular turbo codes (original) (raw)
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Near Capacity Irregular Turbo Code
The purpose of this study is to construct a near capacity Irregular-Turbo Code (I-TC) and to evaluate its performance over Gaussian channel. The methodology used to evaluate and measure the performance of the new design is by simulating the system by developing a software platform using MATLAB. The simulation carried out by implementing the system over different modulation schemes, different frame sizes, and different code rates in order to achieve a fair comparison between irregular turbo code and regular Turbo Code (TC). The simulation results showed that the Irregular Turbo Code with 64QAM modulation is capable of achieving a coding gain of 1.29 dB over its corresponding Turbo Code for a low Bit Error Rate (BER) 10−5, when used in a Gaussian noisy channel. Also, the Irregular Turbo Code designed in this paper, utilizes a single recursive Convolution encoder with short frame size of 5012 bits. The new designed codec can play an important role in many commercial applications such as Third-Generation (3G) wireless phones, Digital Video Broadcasting (DVB) systems, or Wireless Metropolitan Area Networks (WMAN), etc.
Improving 3-dimensional turbo codes using 3GPP2 interleavers
2009 First International Conference on Communications and Networking, 2009
This paper deals with the performance improvement of a 3-dimensional turbo code based on the partial concatenation of the 3GPP2 code with a rate-1 post-encoder. First, we optimize the distance spectrum of the 3-dimensional 3GPP2 turbo code by means of the adoption of a non regular post-encoding pattern. This allows us to increase the minimum Hamming distance and thereby to improve the performance at very low error rates. Then, we propose a time varying construction of the postencoded parity in order to reduce the observable loss of convergence at high error rates. The different improvement stages are illustrated with simulation results, asymptotical bounds and EXIT charts.
A survey of three-dimensional turbo codes and recent performance enhancements
2013
This paper presents a survey of two techniques intended for improving the performance of conventional turbo codes (TCs). The first part of this work is dedicated to explore a hybrid concatenation structure combining both parallel and serial concatenation based on a three-dimensional (3D) code. The 3D structure, recently introduced by Berrou et al., is able to ensure large asymptotic gains at very low error rates at the expense of an increase in complexity and a loss in the convergence threshold. In order to reduce the loss in the convergence threshold, the authors consider first a time-varying construction of the post-encoded parity. Then, they investigate the association of the 3D TC with high-order modulations according to the bit-interleaved coded modulation approach. The second part of this study deals with irregular TCs. In contrast to 3D TCs, although irregular TCs can achieve performance closer to capacity, their asymptotic performance is very poor. Therefore, the authors propose irregular turbo coding schemes with suitable interleavers in order to improve their distance properties. Finally, a modified encoding procedure, inspired from the 3D TC, makes it possible to obtain irregular TCs which perform better than the corresponding regular codes in both the waterfall and the error floor regions.
Analysis of three-dimensional turbo codes
annals of telecommunications - annales des télécommunications, 2012
Our paper presents a detailed study of the 3-dimensional turbo code (3D TC). This code which combines both parallel and serial concatenation is derived from the classical TC by concatenating a rate-1 post-encoder at its output. The 3D TC provides very low error rates for a wide range of block lengths and coding rates, at the expense of an increase in complexity and a loss in convergence. This paper deals with the performance improvement of the 3D TC. First, we optimize the distance spectrum of the 3D TC by means of the adoption of a non regular postencoding pattern. This allows us to increase the Minimum Hamming Distance (MHD) and thereby to improve the performance at very low error rates. Then, we propose a time varying (TV) construction of the post-encoded parity in order to reduce the observable loss of convergence at high error rates. Performance comparisons are made between the 3GPP2 standardized TC and the corresponding 3D code. The different improvement stages are illustrated with simulation results, asymptotical bounds and EXIT charts.
A NOVEL APPROACH FOR DESIGNING HYBRID TURBO CODES USING DOUBLE STAGE INTERLEAVER
Interleaver being an integral component of the communication system. The interleavers tend to avoid the burst errors by splitting the signals and the turbo codes are used to reduce the BER.The paper will describes a new approach to design a new class of turbo codes that would reduce the decoder complexity, such turbo codes will be known as modified turbo codes taking Decoder complexity as the main parameter consideration for the design of modified turbo codes. The author presents the design of two types of modified turbo codes, the one would be called as Low Complexity Hybrid turbo codes (LCHTC) and the other one Improved Low Complexity Hybrid Turbo Codes (ILCHTC).
A proposed Improvement Model for Turbo Codes Performance by Using Additional Interleaver
2012
Iterative decoding in turbo code has very high decoding complexity. This paper adopts an improvement model for Turbo codes (parallel Concatenation Convolutional Codes (PCCCs) by using additional interleaver in the system. The proposed additional interleaver can achieve better error rate performance than standard system, makes the computation much easier and the operation of the hardware system much faster where the number of iteration can be decrease to a half. Simulation results show that the proposed model performs very closely to the Turbo Codes encoder - decoder system in AWGN, correlated and uncorrelated Rayleigh fading channels.
Performance Study of Turbo Code with Interleaver Design
2011
This paper begins with an investigation of the optimization of binary turbo code through good interleaver design. For this purpose, different types of interleaver have designed here and have evaluated their performance. Basically the performances of the turbo code using block interleaver, helical interleaver, random interleaver and odd-even interleaver have evaluated. From this investigation it has been seen that for small code length the performance of the block interleaver is superior in non-puncturing case and the performance of the odd-even interleaver is superior in puncturing case, but for large code length the performance of the random interleaver is better in both of puncturing and non-puncturing condition. In this paper, it has investigated that the performance of the odd-even interleaver (block interleaver with odd number of rows and columns) significantly increased in puncturing conditions. Index terms— Turbo encoder; Turbo decoder; Interleaver; code rate; Puncturing; Non...
Adding a rate-1 third dimension to turbo codes
2007
Thanks to the message passing principle, turbo decoding is able to provide strong error correction near the theoretical (Shannon) limit. However, the minimum Hamming distance (MHD) of a Turbo Code may not be sufficient to prevent a detrimental change in the error rate vs. signal to noise ratio curve, the so-called flattening. Increasing the MHD of a Turbo Code may involve using component encoders with a large number of states, devising more sophisticated internal permutations, or increasing the dimension of the Turbo Code, i.e. the number of component encoders. This paper addresses the latter option and proposes a modified Turbo Code, in which some of the parity bits stemming from the classical component encoders are encoded by a rate-1, third encoder. The result is a significantly increased MHD, which improves turbo decoder performance at low error rates, at the expense of a very small increase in complexity. In the paper, we compare the performance of the proposed Turbo Code with that of the DVB-RCS Turbo Code and the DVB-S2 LDPC code.
IEEE Transactions on Communications, 2009
Thanks to the probabilistic message passing performed between its component decoders, a turbo decoder is able to provide strong error correction close to the theoretical limit. However, the minimum Hamming distance (min) of a turbo code may not be sufficiently large to ensure large asymptotic gains at very low error rates (the so-called flattening effect). Increasing the min of a turbo code may involve using component encoders with a large number of states, devising more sophisticated internal permutations, or increasing the number of component encoders. This paper addresses the latter option and proposes a modified turbo code in which a fraction of the parity bits are encoded by a rate-1, third encoder. The result is a noticeably increased min, which improves turbo decoder performance at low error rates. Performance comparisons with turbo codes and serially concatenated convolutional codes are given.