Asymmetric Turbo Research Articles

Two-Source Asymmetric Turbo-Coded Cooperative Spatial Modulation Scheme with Code Matched Interleaver

This paper proposes, for the first time, a two-source asymmetric turbo-coded-cooperative spatial modulation (SM) scheme over the slow Rayleigh fading channel. As in any coded cooperative communication, the interleaver plays a vital role in mitigating the harsh effect of the wireless channel. Therefore, the code matched interleaver (CMI) is effectively used in the proposed design. The simulated results reveal that the bit error rate (BER) performance of the proposed coded cooperative communication system outperforms the asymmetric turbo-coded non-cooperative scheme under identical conditions. This prominent performance improvement has been made possible due to the joint asymmetric turbo decoding at the destination node. Furthermore, to check the effectiveness of the proposed scheme, we have also developed a two-source asymmetric turbo-coded cooperative scheme based on the vertical bell labs layered space-time (VBLAST), incorporating the CMI as the suitable benchmark. It is observed that the proposed scheme employing SM has a better BER performance than the VBLAST scheme under identical conditions.

Asymmetric Turbo Code for Coded-Cooperative Wireless Communication Based on Matched Interleaver with Channel Estimation and Multi-Receive Antennas at the Destination

Asymmetric Turbo Code for Coded-Cooperative Wireless Communication Based on Matched Interleaver with Channel Estimation and Multi-Receive Antennas at the Destination

Optimized BER Performance of Asymmetric Turbo Codes over AWGN Channel

The performance of the turbo codes can be improved by varying parameters such as block size, code polynomial structure and constraint length. This paper proposes a new asymmetric turbo codes that consists of parallel concatenated component codes with mixed type generator polynomials and also different constraint lengths. This scheme optimizes the BER performance of asymmetric turbo codes of both Waterfall region at lower SNR’s and error-floor region at higher SNR’s. The simulation results shows better BER performance of asymmetric turbo codes for block size of 128, 512 bits, code-rate of 1/2 and Maximum-A-Posteriori (MAP) decoding algorithm over AWGN channel with BPSK modulation by using MATLAB.

Turbo codes with symmetric and asymmetric component codes defined over finite fields of integers

Binary asymmetric turbo codes and non-binary turbo codes have been proposed to improve the bit error rate (BER) performance of parallel concatenated coding schemes. Both strategies have certain advantages that can be exploited when they are put together. This paper investigates turbo codes based on two component recursive systematic convolutional (RSC) codes defined over a finite field of integers. Symmetric and asymmetric non-binary turbo codes are obtained and their BER performance in both the ‘waterfall’ and the ‘error-floor’ regions is analysed. The results show good performance improvements when compared to binary and quaternary turbo codes with same throughput.

A New Unequal Power Allocation Scheme for Asymmetric Turbo Code System

In this paper, a modified unequal power allocation scheme for the different bits of asymmetric turbo encoder has been investigated to enhance the performance. The simulation results and performance bound for the asymmetric turbo code with modified Unequal Power Allocation (UPA) scheme are obtained and compared with the system with typical UPA and without UPA. From the performance results, it is observed that the proposed asymmetric turbo code with modified UPA performs better than the system without UPA and with typical UPA and it provides a coding gain of 0.4---0.52 dB.

Optimal power allocation for the proposed asymmetric turbo code for 3G systems

We proposed a new class of asymmetric turbo encoder for 3G systems that performs well in both “water fall” and “error floor” regions in Ramasamy et al. [Weight distribution analysis of proposed asymmetric turbo code for improved performance, Int J Electron Commun 60(7) 479–93]. In this paper, a modified (optimal) power allocation scheme for the different bits of new class of asymmetric turbo encoder has been investigated to enhance the performance. The simulation results and performance bound for proposed asymmetric turbo code with modified unequal power allocation (UPA) scheme for the frame length, N = 400 , code rate, r = 1 / 3 with log-MAP decoder over additive white Gaussian noise (AWGN) channel are obtained and compared with the system with typical UPA and without UPA. The performance tests are extended over AWGN channel for different frame size to verify the possibility of implementation of the modified UPA scheme for the proposed asymmetric turbo code. From the performance results, it is observed that the proposed asymmetric turbo code with modified UPA performs better than the system without UPA, and with typical UPA and it provides a coding gain of 0.4–0.52 dB.

Optimal Power Allocation for the Proposed Asymmetric Turbo Code for 3G Systems

Abstract We proposed a new class of asymmetric turbo encoder for 3G systems that performs well in both “water fall” and “error floor” regions in Ramasamy et al. [Weight distribution analysis of proposed asymmetric turbo code for improved performance, Int J Electron Commun 60(7) 479–93]. In this paper, a modified (optimal) power allocation scheme for the different bits of new class of asymmetric turbo encoder has been investigated to enhance the performance. The simulation results and performance bound for proposed asymmetric turbo code with modified unequal power allocation (UPA) scheme for the frame length, N = 400 , code rate, r = 1 / 3 with log-MAP decoder over additive white Gaussian noise (AWGN) channel are obtained and compared with the system with typical UPA and without UPA. The performance tests are extended over AWGN channel for different frame size to verify the possibility of implementation of the modified UPA scheme for the proposed asymmetric turbo code. From the performance results, it is observed that the proposed asymmetric turbo code with modified UPA performs better than the system without UPA, and with typical UPA and it provides a coding gain of 0.4–0.52 dB.

Optimal Power Allocation for the Proposed Asymmetric Turbo Code for 3G Systems

Optimal Power Allocation for the Proposed Asymmetric Turbo Code for 3G Systems

Cross-entropy-based method to analyse iterative decoding

Cross-entropy (CE) in information theory is introduced as a method to analyse iterative decoding. The maximum a posteriori probability decoding algorithm is shown to minimise the CE between the a priori and the extrinsic information under given code constraints. The error-correcting ability of the constituent decoders is evaluated in terms of CE. Analysis on turbo decoding is carried out based on theoretical findings from several aspects, including analysis of convergence rate, derivation of the Eb/N0 threshold for convergence, evaluation of error performance in the ‘error-floor’ region and a design example of asymmetric turbo codes. Compared with conventional methods, the new technique provides stricter prediction on the Eb/N0 threshold for convergence and quicker error performance evaluation. An asymmetric turbo code designed with the guidance of our new method exhibits more than 0.1 dB of gain over that guided by classical bounding techniques in both high and low bit error rate regions. Particularly, since no information on the source is required and the density of the a priori/extrinsic information can be arbitrary, the new technique is valuable for both offline design and online evaluation in practical systems.

Performance of JPEG Image Transmission Using Proposed Asymmetric Turbo Code

This paper gives the results of a simulation study on the performance of JPEG image transmission over AWGN and Rayleigh fading channels using typical and proposed asymmetric turbo codes for error control coding. The baseline JPEG algorithm is used to compress a QCIF ( ) "Suzie" image. The recursive systematic convolutional (RSC) encoder with generator polynomials , that is, (13/11) in decimal, and 3G interleaver are used for the typical WCDMA and CDMA2000 turbo codes. The proposed asymmetric turbo code uses generator polynomials , that is, (13/11; 13/9) in decimal, and a code-matched interleaver. The effect of interleaver in the proposed asymmetric turbo code is studied using weight distribution and simulation. The simulation results and performance bound for proposed asymmetric turbo code for the frame length , code rate with Log-MAP decoder over AWGN channel are compared with the typical system. From the simulation results, it is observed that the image transmission using proposed asymmetric turbo code performs better than that with the typical system.

Asymmetric rate compatible turbo codes in hybrid automatic repeat request schemes

The authors present asymmetric turbo hybrid automatic-repeat-request (ATH-ARQ) schemes that employ component code selection and asymmetric rate compatible punctured turbo codes (ARCPT) for enhanced performance in fading channels. The paper also presents a novel low-rate ARCPT encoder structure. An analysis is presented for efficient ARCPT puncture schemes for improved throughput performance at low and high SNR values. It is shown that in certain instances, the use of conventional turbo code structures results in the best performance.

A new class of asymmetric turbo code for 3G systems

In this paper, we propose a new asymmetric turbo encoder for 3G systems that performs well in both “water fall” and “error floor” regions. The Recursive Systematic Convolutional (RSC) encoder with generator polynomials (1, D 3+ D 2+1/ D 3+ D+1), i.e. (13/11) in decimal and 3G interleaver are used for the typical Wideband Code-Divison Multiple Access (WCDMA) and Code-Divison Multiple Access 2000 (CDMA2000) turbo codes. The proposed asymmetric turbo code uses generator polynomials (1, D 3+ D 2+1/ D 3+ D+1; D 3+ D 2+1/ D 3+1), i.e. (13/11;13/9) and a code-matched interleaver. The effect of interleaver in the proposed asymmetric turbo code is studied using weight distribution and simulation. The simulation results and performance bound for proposed asymmetric turbo code for the frame length, N = 400 , code rate, r = 1 / 3 with Log-MAP decoder over additive white Gaussian noise (AWGN) channel are obtained and compared with the typical system. The performance tests are extended over both AWGN and Rayleigh fading channels for different frame size to verify the possibility of implementation of the proposed asymmetric turbo code. From the performance results, it is observed that the proposed asymmetric turbo code performs better than the typical system at both low and high SNR and it provides a coding gain of 0.5–0.8 dB.

Weight distribution analysis of proposed asymmetric turbo code for improved performance

In this paper, we analyze the distance spectrum of proposed asymmetric turbo code [Ramasamy K, Balamuralithara alias Balakrishnan, Mohammad Umar Siddiqi. A new class of asymmetric turbo code for 3G systems. International Journal of Electronics and Communications, accepted for publication] with generator polynomials (1, D 3+D 2+1/D 3+D+1; D 3+D 2+1/D 3+1), i.e. (13/11;13/9) in decimal for its improved performance. The weight distribution of the turbo code with various generator polynomials are obtained using the algorithm described in [Roberto Garello. Computing the free distance of turbo codes and serially concatenated codes with interleavers: algorithms and applications. IEEE Journal on Selected Areas of Communications 2001;19(5):800–12] to analyze the error performance. We also investigate what secondary factors contribute to a good code when the minimum distance is poor. The probability distribution function and cumulative distribution function of weight of the code are obtained and plotted for several short bock length codes using various generator polynomials. It is observed that as the block length increases, weight distribution of the turbo code is approximately Gaussian rather than providing a higher minimum Hamming distance.

An Efficient SF-ISF Approach for the Slepian-Wolf Source Coding Problem

A simple but powerful scheme exploiting the binning concept for asymmetric lossless distributed source coding is proposed. The novelty in the proposed scheme is the introduction of a syndrome former (SF) in the source encoder and an inverse syndrome former (ISF) in the source decoder to efficiently exploit an existing linear channel code without the need to modify the code structure or the decoding strategy. For most channel codes, the construction of SF-ISF pairs is a light task. For parallelly and serially concatenated codes and particularly parallel and serial turbo codes where this appear less obvious, an efficient way for constructing linear complexity SF-ISF pairs is demonstrated. It is shown that the proposed SF-ISF approach is simple, provenly optimal, and generally applicable to any linear channel code. Simulation using conventional and asymmetric turbo codes demonstrates a compression rate that is only 0.06 bit/symbol from the theoretical limit, which is among the best results reported so far.