Turbo Codes Research Articles

EBP-GEXIT Charts for M-Ary AWGN Channel for Generalized LDPC and Turbo Codes

The maximum a posteriori (MAP) threshold corresponds to the fundamental limit that one can hope to achieve with the given channel code ensemble. Apart from theoretical interests, finding this limit is also desirable since <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">spatial-coupled</i> code ensembles approach this MAP threshold due to phenomenon termed as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">threshold saturation</i> . However finding this MAP threshold, in general, is known to be computationally prohibitive. This work proposes a tractable method for estimating the MAP threshold for various families of sparse-graph code ensembles over non-binary complex-input additive white Gaussian noise (AWGN) channel. Towards this, we provide a method to approximate the extended belief propagation generalized extrinsic information transfer (EBP-GEXIT) chart and estimate the MAP threshold by applying the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Maxwell construction</i> to it. To illustrate the validity of our method, we study spatial coupling for serially-concatenated turbo-codes and numerically observe threshold saturation of these codes to the MAP thresholds estimated via our method.

Enhancement of code division multiple access system performance using raptor codes

Some kinds of communication systems work in very low signal-to-noise (LSNR) environments. For these systems to function reliably, &lt;span&gt;specific techniques and methodologies have to be used to mitigate the degrading effects of the channel. The channel coding method is the key element in most LSNR communication systems, but emphasizing the code division multiple access (CDMA) is a new transmission technique in these channels. To enhance the CDMA scheme's system capacity and reach unprecedented ranges of LSNR values in wireless sensor network. This paper suggests combining CDMA with certain types of channel coding algorithms, such as the raptor codes. The raptor channel encoding technique has improved the CDMA system's performance when using binary phase-shift keying (BPSK) modulation in additive white gaussian noise (AWGN) channels. It has achieved a low bit error rate in range of 10-7 at Eb/No value of (-3) dB and about 10-6 at shannon's limit. The Raptor-coded CDMA scheme works well for channel signal to noise ration (SNR) values of greater than -9 dB, showing an improvement of about 7 dB compared with turbo/convolutional channel coding methods used with the CDMA system bit error rate (BER) and throughput. On the other hand, it has been shown that the convolutional encoder presents the weakest performance compared to both the turbo and raptor codes.&lt;/span&gt;

A Delay-Efficient Deep Learning Approach for Lossless Turbo Source Coding

Lossless turbo source coding with decremental/incremental redundancy is a variable-length source coding scheme which employs turbo codes for data compression. Although the scheme offers low compression rates and lends itself to joint source-channel coding, it suffers from a large delay in the encoding phase. The delay is imposed by several tentative encoding-decoding procedures performed at the encoder to search for the minimum compression length. In this work, we apply machine learning to provide a highly accurate estimate of the proper compression length. The encoder starts its search from this estimated length, thus the delay of turbo source coding will decrease considerably. The preliminary results show a four-fold reduction in the encoding delay at the expense of a negligible increase in the compression rate.

Developing method for constructing modular turbo code for anti-jam satellite authentication system

Low-earth orbit (LEO) satellite communication systems must have anti-jam property, which is based on information, structural and energy secrecy as well as immunity to jamming. One of the directions associated with increasing information secrecy is based on the use of a satellite identification system. This system is designed to prevent the imposition of foreign content on the subscriber through the use of an authentication protocol built on proof with zero knowledge. To reduce the time of applicant identification, a number of works propose to use modular codes (MC), which allow parallelizing the computational process in the protocol. It is known that MCs can improve the fault tolerance of the identification system since they are able to eliminate the consequences of faults and failures during operation. However, they can also be used to improve the immunity of LEO satellite communication systems to jamming. Thus, the use of a unified algebraic system when constructing MCs capable of correcting errors caused not only by faults and failures during the operation of the identification system but also by interference in the communication channel will enable to abandon concatenated codes. Therefore, the development of a method for constructing a modular turbo code for an anti-jam satellite authentication system is an urgent task.

PAPR and BER analysis of coded FBMC-OQAM system with non-linear companding techniques

Filter Bank Multicarrier with offset QAM (OQAM) is a suitable multicarrier waveform technique for 5 G and future wireless networks and standards. Being a multicarrier technique, it suffers from high peak-to-average-power ratio (PAPR) problem. In this paper we have used some non-linear companding transforms such as μ-law, A-law, rooting, tangent rooting, and logarithmic rooting to overcome the PAPR problem. Since non-linear companding techniques degrade bit-error-rate (BER) performance of a system. Hence, some channel coding techniques such as convolutional codes and turbo codes are employed to enhance the BER performance of non-linearly companded FBMC-OQAM system. It was observed that the combination of convolutional coding with logarithmic rooting companding provides PAPR reduction gain of about 4.896 dB and coding gain of about 2 dB as compared to conventional FBMC-OQAM system and is an appropriate choice for applications requiring reduced system complexity. It was observed that the combination of turbo coding with logarithmic rooting companding provides PAPR reduction gain of about 4.922 dB and a sufficiently high coding gain of about 7 dB as compared to conventional FBMC-OQAM system and is suitable for applications requiring improved data reliability at the expense of increased system complexity and latency.

Irregular Vector Turbo Codes with low complexity

The term Block Turbo Code typically refers to the iterative decoding of a serially concatenated two-dimensional systematic block code. This paper introduces a Vector Turbo Code that is irregular but with code rates comparable to those of a Block Turbo Code (BTC) when the Bahl Cocke Jelinek Raviv algorithm is used. In BTC’s, the horizontal (or vertical) blocks are encoded first and the vertical (or horizontal) blocks second. The irregular Vector Turbo Code (iVTC) uses information bits that participate in varying numbers of trellis sections, which are organized into blocks that are encoded horizontally (or vertical) without vertical (or horizontal) encoding. The decoding requires only one soft-input soft-output decoder. In general, a reduction in complexity, in comparison to a BTC was achieved for the same very low probability of bit error (10^{-5}). Performance in the AWGN channel shows that iVTC is capable of achieving a significant coding gain of 1.28dB for a 64QAM modulation scheme, at a bit error rate of 10^{-5}over its corresponding BTC. Simulation results also show that some of these codes perform within 0.49dB of capacity for binary transmission over an AWGN channel.

Data Transmission Enhancement Using Optimal Coding Technique Over In Vivo Channel for Interbody Communication.

Wireless in vivo actuators and sensors are examples of sophisticated technologies. Another breakthrough is the use of in vivo wireless medical devices, which provide scalable and cost-effective solutions for wearable device integration. In vivo wireless body area networks devices reduce surgery invasiveness and provide continuous health monitoring. Also, patient data may be collected over a long period of time. Given the large fading in in vivo channels due to the signal path going through flesh, bones, skins, and blood, channel coding is considered a solution for increasing the efficiency and overcoming inter-symbol interference in wireless communications. Simulations are performed by using 50 MHz bandwidth at Ultra-Wideband frequencies (3.10-10.60 GHz). Optimal channel coding (Turbo codes, Convolutional codes, with the help of polar codes) improves data transmission performance over the in vivo channel in this research. Moreover, the results reveal that turbo codes outperform polar and convolutional codes in terms of bit error rate. Other approaches perform similarly when the information block length is increased. The simulation in this work indicates that the in vivo channel shows less performance than the Rayleigh channel due to the dense structure of the human body (flesh, skins, blood, bones, muscles, and fat).

Nonbinary I-Polar Coded Modulation

Polar codes were shown to be weak at finite block lengths even under maximum-likelihood (ML) decoding. To enhance polar codes, CRC-aided polar codes were proposed. It has been shown that CRC-aided polar codes under the successive cancellation list (SCL) decoder outperform LDPC codes and turbo codes. Recently, interleaved polar (i-polar) codes were proposed. By using a new bit channel selection algorithm, i-polar codes without CRC were shown to outperform the 5G LDPC codes. However, most research on polar codes focuses on the binary case. In this paper, a new family of nonbinary i-polar codes with random constellation mapping is proposed. A recursive form for calculating the average weight enumerating function (WEF) of the nonbinary i-polar code is derived. With the random constellation mapping, the upper bound on the BLER under ML decoding depends on the WEF of the nonbinary i-polar code. Then a new channel selection algorithm is proposed based on the polarization effect and the BLER upper bound. The algorithm generates a sequence, termed the i-polar sequence (IPS). Simulation results show that the nonbinary i-polar codes with the IPS outperform the 5G LDPC codes.

Verilog HDL using LTE Implementation MAP Algorithm

In many communication systems, turbo coding Techniques for Encoding and Decoding are employed to repair errors. As compared to other error correction codes, turbo codes provide great error correcting capabilities. For the implementation of the Turbo decoder, a Very Large Scale Integration (VLSI) architecture is suggested in this study. The Maximum-a-Posteriori (MAP) algorithm is employed at the decoder side, where soft-in-soft-out decoders, interleaves, and deinterleavers are all used. The usage of the MAP algorithm reduces the quantity of iterations necessary to decode the information bits being transferred. This research employs a system for the encoder component that consists of two recursive convolutional encoders and a pseudorandom interleaver on the encoder side. Tools from Octave and Xilinx Vivado are used for the Turbo encoding and decoding. The system is synthesised and implemented using a specialised integrated circuit.

Design of Robust Video Transmission System by Using Efficient Forward Error Correction Scheme

The advent of modern digital technologies has made multimedia communication systems one of the most demanding technologies of the time. The use of available bandwidth for efficient and errorless multimedia communication is the key challenge for the wireless communication research community. However, a wireless network has the disadvantage of being prone to random channel noise and data contamination. This paper proposes a robust video transmission framework by using an efficient forward error correction technique. In this work, the experimental performance of widely used forward error correction codes i.e., Convolution codes, LDPC codes, Turbo codes, and Concatenated codes, are compared based on their capability to compensate the channel noise and distortion. An efficient encoding scheme is devised for the transmission of YUV encoded frames by using the selected FEC codes in a noisy channel environment. The retrieved video is analysed by using the Peak Signal-to-Noise ratio and bit error rate as performance metrics. The results and cross comparison shows that concatenated codes have a handsome improvement in avoiding channel contamination and distortion.

A Generic Reliability Based Direct Decoding Algorithm for Turbo Codes

A Generic Reliability Based Direct Decoding Algorithm for Turbo Codes

Research and Implementation of Turbo Coding Technology in High-Speed Underwater Acoustic OFDM Communication

It is demonstrated that the fully parallel turbo decoding algorithm can achieve an approximate error correction decoding performance when 36 iterations are used and when the log-map algorithm with 6 iterations is used. By comparison, it is shown that it can achieve much higher decoding rates than the log-map algorithm for various frame lengths of LTE standard turbo codes at the cost of higher hardware resource requirements. According to the fully parallel turbo decoding algorithm, this paper proposes a scheme for implementing a fully parallel turbo decoder on FPGA, detailing the overall structure and processing of the decoder hardware implementation, the design of the algorithm block processing unit, and the interleaving module. The performance of the decoder is tested by fixed-point simulation for different frame lengths of turbo coding in LTE standard, and it is proved that the fully parallel turbo decoder can be applied to turbo coding of various frame lengths. Both simulation and experimental results show that the distributed cancellation method and the joint estimation cancellation method have good results for both time-domain impulse noise and large-amplitude single frequency noise cancellation, while the joint estimation cancellation method of large-amplitude single frequency noise cancellation first has better performance.

A Comprehensive Review of Low Density Parity Check Encoder Techniques

This paper presents a survey on various technologies of low density parity check encoder. LDPC codes are capable to handle high speed communication channel, by reducing attenuation, hazards and efficiently rectifying the linear error correction. Various coding technologies used in new generation communication system, such as turbo code, hamming code, low-density parity check (LDPC) code and Bose–Chaudhuri–Hocquenghem (BHC) code, are widely used in recent communication system. The LDPC has technical remarkable advantages and better performance in high speed communication process compared to turbo code. This paper deals with study of LDPC encoding techniques with various methods of detecting error and its correction. Here classification and performance analysis of LDPC encoding techniques on the basis of resources utilization, systematic, non-systematic approaches and consumer data right etc. have been analyzed in this paper. Apart from above mentioned criteria, this study deals with hardware and software architecture of LDPC encoder in rectification of forward error correction, parallel execution of instruction set. This study and analysis could offer scalability, the future scope of improving the performance of LDPC encoder in all aspects of the next generation communication process. This paper gives overview of various LDPC encoder applications, drawbacks and solution to overcome it.

Design and Implementation of Shared Memory for Turbo and LDPC Code Interleaver

In 4G turbo and 5G LDPC, in order to realize a flexible, low-power, low-cost shared general-purpose block interleaving hardware module, it faces the challenges of interleaving structure integration, fewer gate circuits, parallel multistream operation, and switching between standards. Facing these challenges, after studying 3GPP TS 36.212 V15.4.0 and 3GPP TS 38.212 V15.4.0 protocols, common part of two major interleaving module standards is found. For the block interleave module in the rate matching of the 4G downlink turbo code and the bit interleave module after the rate matching of the 5G NR downlink LDPC code, this paper first designs a memory and implements the two codes interleaving on it. Then, based on the Altera Quartus prime platform and ModelSim for functional verification. Experimental results show that under SMIC 28 nm, operating frequency 50MHz, after synopsys synthesis, the memory module area is 0.17 μ m 2 , and the power consumption is 6.45 mW. Through the shared design, 32 bits parallel access, and switching between standards, the proposed scheme reduces the hardware cost, power consumption, and clock overhead, and improves the flexibility of 4G LTE and 5G NR communication downlink hardware implementation.

Adaptive Demodulation in Impulse Noise Channels

Electromagnetic interference causes considerable performance degradation on wireless communication systems. The performance degradation is largely affected by the characteristics of the interference. Impulse interference commonly occurs in industrial and automotive environments, where many closely located systems and electronic equipment coexist. In this work, we propose two novel algorithms for adaptive demodulation in impulse noise. The proposed methods compute appropriate log-likelihood ratios based on interference classification and estimation of Middleton’s Class A noise model as well as the symmetric <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> -Stable (S <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> S) model. The analytical complexity and intractability of the S <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> S probability density function (PDF) makes real-time applications unfeasible. Therefore, the proposed algorithms are developed using two different techniques for approximating the S <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> S PDF. The approximations are achieved through interpolation via <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i)</i> approximate closed-form expressions of the PDF for a specific parameter set and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ii)</i> via numerically pre-calculated look-up tables of the PDF for arbitrary parameter choices. The proposed adaptive techniques are shown to provide a performance gain in terms of bit error rate (BER) of up to 20 dB energy per bit to noise power ratio (Eb/N0), in comparison to traditional, non-adaptive, methods for varying levels of impulse interference. The performance loss of approximating the PDF in comparison to exact calculations amount to less than 8 dB Eb/N0, which is small in relation to the performance gain achieved in comparison to traditional methods. However, the complexity in terms of simulation execution time of the proposed approximate algorithms is reduced by up to a factor 250, compared to methods based on exact computation. The algorithms are validated using regular low density parity check (LDPC) codes, in addition to quasi-cyclic (QC)-LDPC and turbo codes. The proposed adaptive demodulation techniques can be used to improve decoding and demodulation performance in many real-life situations where non-Gaussian interference commonly occurs.

Performance Analysis of Error Control Codes for Underwater Wireless Acoustic Communication

In underwater acoustic communication, the information transmitted from 1 sensor node to another is corrupted due to errors persuaded by the noisy channel and other issues. To reduce the bit error rate, it is essential to propose suitable error regulator structure. In this paper, we simulate the performance analysis of Orthogonal Frequency Division Multiplexing Interleaver Division Multiple Access Multiple Input Multiple Output scheme with different channel codes to improve bit error rate performance. Bit error rate and consumed power are measured by communicating arbitrarily generated information through AWGN network. From the simulation results and assessment of the 2 divergent channel coding, 2 interleavers and 3 modulation techniques. We conclude that turbo codes with random interleaver and binary phase shift keying are best suitable to improve reliability performance for underwater wireless acoustic communication. To reduce the burst error in underwater acostic communication we propose an hybrid approach IDMA OFDM MIMO. BER performance is improved upto 10−6.&#x0D; HIGHLIGHTS&#x0D; &#x0D; In underwater acoustic communication to reduce bit error rate, we simulate the performance analysis of Orthogonal Frequency Division Multiplexing Interleaver Division Multiple Access Multiple Input Multiple Output scheme&#x0D; We propose a hybrid approach with 2 divergent channel coding, 2 interleavers and 3 modulation techniques&#x0D; Finally, we observe from simulation results that turbo code with binary phase shift keying and random interleaving improves bit error rate performance&#x0D; &#x0D; GRAPHICAL ABSTRACT

Performance Analysis of FS-FBMC/OQAM System Using Turbo and LDPC Codes

Filter Bank Multicarrier (FBMC) with offset QAM (OQAM) is a possible waveform candidate for 5G and future wireless systems and standards. FBMC is realized using either polyphase network (PPN)-FFT or Frequency Spread (FS)-FBMC. In this paper, channel coding schemes such as turbo codes and low-density parity check (LDPC) codes were investigated in terms of their peak-to-average power ratio (PAPR) and bit-error-rate (BER) reduction performances for FS-FBMC/OQAM and Orthogonal Frequency Division Multiplexing (OFDM) systems in additive white Gaussian noise (AWGN) channel. Simulation results show that turbo coded and LDPC coded FS-FBMC/OQAM systems performed better than turbo coded and LDPC coded OFDM systems in terms of BER performance. Also, LDPC coded FS-FBMC/OQAM system because of its adequate BER performance, reasonable PAPR performance, and reduced computational complexity was found to be an appropriate choice among other systems for 5G and future wireless networks. It was also found that incorporating channel coding resulted in a very large coding gain with only a minor rise in the system's PAPR value.

Hybrid turbo code for information security and reliability

Wireless communication channels are highly vulnerable to security attacks and channel noise. Most wireless communication systems deploy advanced encryption standard (AES) and turbo code for security and reliability. However, the sequential process of encryption and encoding increases the resources, computational cost and reduces the overall error correction performance. A hybrid turbo code (HTC) for encryption and error correction is proposed. The HTC deploys a proposed Weierstrass elliptic curve interleaver (WECI) for random shuffling of the input bits. The difficulty of solving the elliptic curve discrete logarithm makes the WECI cryptographically strong. The simulation results of HTC depict a bit error rate of almost 10-3.8 at a signal-to-noise ratio of 2 dB similar to the conventional turbo code. Moreover, it provides security and reliability to the transmitted data at a reduced computational cost and memory as compared to the conventional system using AES followed by turbo code.

A Novel Scheme for Joint Error Control and Dynamic Security Coding Using Puncturing Mechanism

Reliability and confidentiality are two crucial aspects of digital wireless communications. Due to open-air communication, wireless communication is easy to be eavesdropped on. This paper proposes a scheme allowing a joint error control and dynamic security coding. This scheme consists of combining encryption and Turbo coding in only one step. The secret key derived from channel parameters between legitimate users is used as a seed for Data Encryption Standard (DES) generator and Advanced Encryption Standard (AES) generators with different key lengths to generate a pseudo-random bit sequence. The pseudo-random bit sequence is used to control the puncturing mechanism in the Turbo code. The simulations are carried out in Additive White Gaussian Noise (AWGN) and Rayleigh channels. The simulation results show that the proposed scheme in the AES generator with a high key length outperforms the conventional Turbo code in error correction capability. Moreover, the proposed scheme allows dynamic security coding without changing the hardware structure of the transceiver devices.

Embedded Coded Relay System for Molecular Communications

With the emergence of the COVID-19 pandemic, the World Health Organization (WHO) has urged scientists and industrialists to explore modern information and communication technology (ICT) as a means to reduce or even eliminate it. The World Health Organization recently reported that the virus may infect the organism through any organ in the living body, such as the respiratory, the immunity, the nervous, the digestive, or the cardiovascular system. Targeting the abovementioned goal, we envision an implanted nanosystem embedded in the intra living-body network. The main function of the nanosystem is either to perform diagnosis and mitigation of infectious diseases or to implement a targeted drug delivery system (i.e., delivery of the therapeutic drug to the diseased tissue or targeted cell). The communication among the nanomachines is accomplished via communication-based molecular diffusion. The control/interconnection of the nanosystem is accomplished through the utilization of Internet of bio-nano things (IoBNT). The proposed nanosystem is designed to employ a coded relay nanomachine disciplined by the decode and forward (DF) principle to ensure reliable drug delivery to the targeted cell. Notably, both the sensitivity of the drug dose and the phenomenon of drug molecules loss before delivery to the target cell site in long-distance due to the molecules diffusion process are taken into account. In this paper, a coded relay NM with conventional coding techniques such as RS and Turbo codes is selected to achieve minimum bit error rate (BER) performance and high signal-to-noise ratio (SNR), while the detection process is based on maximum likelihood (ML) probability and minimum error probability (MEP). The performance analysis of the proposed scheme is evaluated in terms of channel capacity and bit error rate by varying system parameters such as relay position, number of released molecules, relay and receiver size. Analysis results are validated through simulation and demonstrate that the proposed scheme can significantly improve delivery performance of the desirable drugs in the molecular communication system.