Trellis Codes Research Articles

Toward the Prediction of Irreducible Error Floor in Space Time Trellis Code

This letter presents a prediction algorithm that foresees the possibility of irreducible error floor for a particular design of a generator matrix G in space time trellis code. This is done without the need of complex and time-consuming simulation, which removes the demand of considerable computational resource. To note, the prediction achieves approximately 93% accuracy and reduces roughly 99% of the temporal cost of simulation. It capitalizes on error prone substructure, a well-known concept from low density parity check code to enable the predictive mechanism. This can be useful in code design where problematic generator matrices can be omitted from consideration.

Performance comparison of space-time block and trellis codes in the MIMO land mobile satellite channels

Due to the crowded orbits and shortage of frequency resources, the use of MIMO technology to improve spectrum efficiency and an increase of the capacity have become a necessary trend of broadband satellite communication. Firstly, we analyze the main influenced factors and compare the bit error rate (BER) performance of space-time block code (STBC) scheme and space-time trellis code (STTC) scheme. Then we build up the model of land mobile satellite (LMS) channel under different environments by using 3-state Markov chain. This paper emphatically studies the BER performance of STTC and STBC in the MIMO satellite channel. The main emphasis is placed on the effects of different factors, such as terminal environment and elevation angles, on the BER performance of STBC and STTC schemes. Simulation results indicate that performance of STTC in Rayleigh channel is obviously improved with the increasing number of transmitting and receiving antennas, but the encoder state has little impact on the performance. In the Rayleigh channel, the performance of Alamouti code is better than that of STTC. In the LMS channel, performance of these two kinds of space-time coding in open area is optimal, and in the urban area it is the worst. Nevertheless, performance of STTC is slightly superior to the performance of STBC under different circumstances. Under the same environmental conditions, BER of STBC and STTC reduces with the increase of the satellite altitude angle, and therefore, the BER curves of STTC fall faster.

Modified codewords design for space–time block coded spatial modulation

Two kinds of modified codewords for space–time block coded spatial modulation (STBC-SM) are presented in this study. The first modified codeword introduces a concept of flexible coefficients into the M-ary phase shift keying STBC-SM. A method is proposed to obtain the optimal flexible coefficients. Moreover, the first modified codewords can also be applied to the systems developed from the STBC-SM. In the second provided codewords, super-orthogonal space–time trellis codes are applied in STBC-SM. Therefore, a higher spectral efficiency is obtained compared with the original STBC-SM. Finally, the simulation results and theoretical analysis demonstrate these performance advantages of the two kinds of modified codewords for STBC-SM.

A Genetic Algorithm for Optimizing TCM Encoder

This article describes a genetic algorithm for the optimization of the Trellis Coded Modulation (TCM) schemes with a view to achieve a higher performance in the multipath fading channel. The use of genetic algorithms is motivated by the fact that they are capable of performing global searches to retrieve an approximate solution to an optimization problem and if the solution is unknown to provide one within a reasonable time lapse. The TCM schemes are indeed optimized by the Rouane and Costello algorithm but the latter has as major disadvantage high requirements in both computation time and memory storage. This is further exacerbated by an increase in the encoder rate, the number of memory piles and the depth of the trellis. We describe a genetic algorithm which is especially well suited to combinatorial optimization, in particular to the optimization of NP-complete problems for which the computation time grows with the complexity of the problem, in a non-polynomial way. Furthermore this opens up the possibility of using the method for the generation of codes for channel characteristics for which no optimization codes are yet known. Simulation results are presented, that show the evolutionary programming algorithm on several generations of populations which only exhibit a medium probability of exchanging genetic information.

Single Carrier Frequency Domain Equalization with Space-Time Trellis Codes

Orthogonal Frequency Division Multiplexing (OFDM) is readily employed in wireless communication to combat the intersymbol interference (ISI) effect with limited success because as the capacity of MIMO systems increases, other destructive effects affect the propagation channels and/or overall system performance. As such, research interest has increased, on how to improve performance in the mediums where fading and ISI permeate, working on several combinatorial techniques to achieving improved effective throughput. In this study, we propose a combined model of the Space-Time Trellis Code (STTC) and Single-Carrier Frequency Domain Equalization (SC-FDE) to mitigate multiple-fading and interference effects. We present analytical performance results for the combined model over spatially correlated Rayleigh fading channels. We also show that it is beneficial to combine coding with equalization at the system’s receiving-end ensuring overall performance: a better performance over the traditional space-time trellis codes.

Performance of STBC-MTCM/TCM Systems for High Rate Transmissions

본 논문에서는 무선통신 채널에서 STBC는 코딩이득을 얻기 위하여 연접코드를 사용해야하는 점을 고려하여, 2×1 MISO 시스템에서 외부 코드로 MTCM이나 TCM을 사용하여 빠르게 변화하는 리시안 페이딩채널에서 STBC-MTCM/TCM 구조의 FER 성능 개선을 위한 연구를 수행하였다. 외부 코드로 사용된 MTCM 코드로는 기존의 Divsalar의 MTCM 코드 외에, Periyalwar의 MTCM 코드 또한 사용하였다. 모의실험 결과에 의하면, 빠르게 변화하는 리시안 페이딩채널에서 외부 코드로 Periyalwar의 MTCM 코드를 고려하여 상태수와 대역폭 효율을 같게 하여 비교한 결과 기존의 STBC-MTCM에 비하여 아무런 손실없이 FER=10-5에서 0.4dB의 코딩이득을 얻을 수 있음을 확인하였다. 또한 이미 알려진 STTC 코드와 공정한 조건에서 FER 성능을 비교한 결과도 제시하였다.

The design of Viterbi decoder for low power consumption space time trellis code without adder architecture using RTL model

Purpose This paper aims to describe the real-time design and implementation of a Space Time Trellis Code decoder using Altera Complex Programmable Logic Devices (CPLD). Design/methodology/approach The code uses a generator matrix designed for four-state space time trellis code (STTC) that uses quadrature phase shift keying (QPSK) modulation scheme. The decoding process has been carried out using maximum likelihood sequences estimation through the Viterbi algorithm. Findings The results showed that the STTC decoder can successfully decipher the encoded symbols from the STTC encoder and can fully recover the original data. The data rate of the decoder is 50 Mbps. Originality/value It has been shown that 96 per cent improvement of the total logic elements in Max V CPLD is used compared to the previous literature review.

Adaptive Spatial Steganography Based on the Correlation of Wavelet Coefficients for Digital Images in Spatial Domain

How to define the pixel’s embedding distortion is a key problem of image adaptive steganography. This paper proposes an adaptive spatial steganography in spatial domain based on the correlation of wavelet coefficients for digital images according to the principle of minimizing a suitable defined distortion. Firstly, one-dimensional high-pass and low-pass filters are used to construct directional filters. Secondly, do direction filtering to images through the direction of horizontal, vertical and diagonal, and design the distortion cost function according to the correlation of wavelet coefficients. Finally, the secret message is embedded by STC (Syndrome Trellis Code) according to the pixel’s embedding distortion. The experiment results illustrate that the proposed method not only make the embedding region focus on the texture regions whose content is complex, but also can resist the common steganalysis detection effectively.

Analysing generator matrices G of similar state but varying minimum determinants

Since Tarokh discovered Space-Time Trellis Code (STTC) in 1998, a considerable effort has been done to improve the performance of the original STTC. One way of achieving enhancement is by focusing on the generator matrix G, which represents the encoder structure for STTC. Until now, researchers have only concentrated on STTCs of different states in analyzing the performance of generator matrix G. No effort has been made on different generator matrices G of similar state. The reason being, it is difficult to produce a wide variety of generator matrices G with diverse minimum determinants. In this paper a number of generator matrices G with minimum determinant of four (4), eight (8) and sixteen (16) of the same state (i.e., 4-PSK) have been successfully produced. The performance of different generator matrices G in term of their bit error rate and signal-to-noise ratio for a Rayleigh fading environment are compared and evaluated. It is found from the MATLAB simulation that at low SNR (<8), the BER of generator matrices G with smaller minimum determinant is comparatively lower than those of higher minimum determinant. However, at high SNR (>14) there is no significant difference between the BER of these generator matrices G.

A Novel Cooperative Diversity Technique Based on Multilevel Pseudo Space–Time Trellis Coding

Several multilevel space---time trellis coding (MLSTTC) techniques have been investigated in the past few years to attain the benefits of spectral efficiency, coding gain and diversity gain. Howeve...

On Code Design for Joint Energy and Information Transfer

Harvesting energy from radio frequency signals along with transmitting data through them is appealing for different wireless communication scenarios, such as radio frequency identification (RFID) systems and implantable devices. In this paper, we propose a technique to design nonlinear codes for the use in such systems taking into account both energy transmission and error rate requirements. In particular, we propose using concatenation of a nonlinear trellis code (NLTC) with an outer low-density parity-check (LDPC) code. We design the NLTC based on maximization of its free distance. We give necessary and sufficient conditions for its catastrophicity; in order to avoid catastrophic codes, we connect each designed NLTC to a corresponding linear convolutional code allowing for the use of simpler conditions for verification. Furthermore, we use EXIT charts to design the outer LDPC code while fixing the inner NLTC. Via examples, we demonstrate that our designed codes operate at $\sim 0.8$ dB away from the information theoretic limits, and they outperform both regular LDPC codes and optimized irregular LDPC codes for additive white Gaussian noise (AWGN) channels. In addition, we show that the proposed scheme outperforms the reference schemes of concatenating LDPC codes with nonlinear memoryless mappers and using classical linear block codes in a time switching mode.

Cooperative Transmission Through Signal-Superposition-Based Braid Coding

This paper investigates a cooperative transmission scheme for a multisource single-destination system through superposition modulation based on braid coding. The source nodes take turns transmitting, and each time, a source “overlays” its new data together with (some or all of) what it overhears from its partner(s), in a way similar to French braiding the hair. We show that the proposed “braid coding” cooperative scheme benefits not only from the cooperative diversity but from the bit error rate (BER) performance gain as well. We introduce two subclasses of braid coding, namely, the nonregenerative and regenerative cases, and, using the pairwise error probability (PEP) as a figure of merit, derive the optimal weight parameters for each one. By exploiting the structure relevance of braid codes with trellis codes, we propose a Viterbi maximum-likelihood (ML) decoding method of linear complexity for the regenerative case; we also investigate and compare several linear detectors for the nonregenerative case. We analyze the theoretical BER performance of the proposed scheme and prove that the full diversity order can be achieved using braid coding. Moreover, we discuss the memory size that strikes the best balance between performance and complexity by considering both the (Euclidean) free distance and the diversity order. The proposed braid coding can be viewed as a special case of network coding. Finally, we present soft-iterative joint channel–network decoding. The overall decoding process is divided into forward message passing and backward message passing, which makes effective use of the available reliability information from all the received signals. Simulation results confirm the efficacy and efficiency of the proposed scheme.

Cooperative multilevel dynamic space–time trellis coding scheme for improved system performance

This study proposes a system that employs multilevel coding scheme with dynamic space–time trellis codes (DSTTCs) as component codes in order to cooperatively transmit the information of mobile nodes to a common destination node. Perfect channel state information is available at both transmitter and receiver. Every mobile node has a DSTTC encoder at each information level, which receives feedback information from destination node and adapts to the current channel conditions by modifying its code set of generator sequences. The feedback information is in the form of an index of predefined channel profile with power gain in close proximity to the power gain of current channel profile at destination node. The proposed cooperative multilevel dynamic space–time trellis coding (CMLDSTTC) system has the potential of improving spectral efficiency, system throughput, diversity gain, coding gain with low decoding complexity. The CMLDSTTC system outperforms cooperative multilevel space–time trellis coding (CMLSTTC) system with predefined space–time trellis codes and non-cooperative multilevel dynamic space–time trellis coding system by ∼5 and ∼2.5 dB, respectively, at frame error rate of 10−2 using two transmit and two receive antennas. The performance of CMLDSTTC system improves further with an increase in the bits of feedback information.

Multilevel space–time trellis coded cooperation with channel state information at transmitter

SummaryIn this paper, the authors propose a system where a number of cooperating mobile nodes transmit information to a common destination node. Each cooperating node has a set of decoders to detect the information of other nodes and a set of encoders to further encode the decoded information as well as its own information using multilevel space–time trellis coding (MLSTTC) scheme. The coded information is mapped using multi‐resolution modulation partitioning to M‐ary quadrature amplitude modulation constellation. The mapped symbols are weighted based on the available channel state information at transmitting nodes. The weighting of transmitting symbols provides beamforming resulting in receive signal‐to‐noise ratio gain. The weighted symbols are sent to destination node through two transmit antennas. If the information of other nodes has been correctly decoded at the cooperating node, then the destination node receives the information of each node as many times as there are number of transmitting nodes, thus achieving full diversity order. A multistage Viterbi decoder is used at the destination node to extract information of each mobile node. The results indicate that the performance of proposed cooperative MLSTTC system is superior to non‐cooperative MLSTTC system. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Quality optimized medical image information hiding algorithm that employs edge detection and data coding

ObjectivesThe present work has the goal of developing a secure medical imaging information system based on a combined steganography and cryptography technique. It attempts to securely embed patient's confidential information into his/her medical images. MethodsThe proposed information security scheme conceals coded Electronic Patient Records (EPRs) into medical images in order to protect the EPRs’ confidentiality without affecting the image quality and particularly the Region of Interest (ROI), which is essential for diagnosis. The secret EPR data is converted into ciphertext using private symmetric encryption method. Since the Human Visual System (HVS) is less sensitive to alterations in sharp regions compared to uniform regions, a simple edge detection method has been introduced to identify and embed in edge pixels, which will lead to an improved stego image quality. In order to increase the embedding capacity, the algorithm embeds variable number of bits (up to 3) in edge pixels based on the strength of edges. Moreover, to increase the efficiency, two message coding mechanisms have been utilized to enhance the ±1 steganography. The first one, which is based on Hamming code, is simple and fast, while the other which is known as the Syndrome Trellis Code (STC), is more sophisticated as it attempts to find a stego image that is close to the cover image through minimizing the embedding impact. The proposed steganography algorithm embeds the secret data bits into the Region of Non Interest (RONI), where due to its importance; the ROI is preserved from modifications. ResultsThe experimental results demonstrate that the proposed method can embed large amount of secret data without leaving a noticeable distortion in the output image. The effectiveness of the proposed algorithm is also proven using one of the efficient steganalysis techniques. ConclusionThe proposed medical imaging information system proved to be capable of concealing EPR data and producing imperceptible stego images with minimal embedding distortions compared to other existing methods. In order to refrain from introducing any modifications to the ROI, the proposed system only utilizes the Region of Non Interest (RONI) in embedding the EPR data.

Low complex decoding algorithm for multilevel space time trellis codes over MIMO channel

It has been proved in literatures that the multilevel space time trellis codes MLSTTC provides higher order diversity with low complex component codes compared to single STTC. The throughput increases with manageable complexity compared to single space time trellis codes STTC. But the computational complexity increases with the number of levels in the MLSTTC system. And also the metric calculation is a complex equation which needs more multiply and accumulate operation compared to single STTC. In this paper, reduced complexity decoding algorithm for multilevel space time trellis code is proposed to reduce the decoding delay and computational power required at the receiver. The simulation results show that the proposed algorithm gives a BER performance nearer to that of the system with full complexity. Further, the impact of correlation between the antennas in the system is also analysed. The simulation results show that with correlated antennas we could maximise the performance.

Permutation Trellis Coded Multi-Level FSK Signaling to Mitigate Primary User Interference in Cognitive Radio Networks

In this paper, we propose a novel spectrum underlay approach for secondary users where a permutation trellis code (PTC) is employed in conjunction with multi-level frequency shift keying signaling in the presence of multiple narrowband primary users (PUs). The PUs are assumed to be dynamic in that they appear intermittently and stay active for an unknown duration. Our proposed approach derives its resilience to the interference caused by PUs and noise disturbances via dispersal of the information in SU’s messages over multiple frequencies and time intervals. Our proposed underlay-design improves the SU data rate by accumulating a large amount of spectrum from several PUs, while simultaneously operating at low power to minimize the interference caused at PUs’ receivers. We evaluate our system performance in terms of bit error rate (BER) and throughput by approximating the actual BER using properties of the Viterbi decoder. We corroborate our analytical results with simulation results and show that our proposed coded system is robust to heavy interference caused by multiple narrowband PUs.

Pseudo Distance for Trellis Coded Modulation in Overloaded MIMO OFDM with Sphere Decoding

Pseudo Distance for Trellis Coded Modulation in Overloaded MIMO OFDM with Sphere Decoding

ENGLISH

Steganography is the art of hidden inscription, used prominently to cover text, image, video and audio. The persistence of steganography is to hide the presence of a message from a third party. The intention of this paper is to achieve statistical security without degrading the stego image quality and to improve undetectability. This paper conceals the secret image behind the original image to obtain the stego image. The extraction of inversion pattern, rotation pattern and invariant local binary pattern is preceded to calculate the distortion of cover image. The obtained image is scrambled in order to distribute the pixels uniformly. To reduce the embedding impact of image and to improve the statistical security, Syndrome Trellis Code (STC) is employed which mainly uses the convolutional code with Viterbi algorithm. The steganography application is realized in STC technique by covering the binary image over the original image. The resultant stego image is obtained after proceeding with the STC technique. The proposed technique is simulated in MATLAB and implemented in Spartan 3 FPGA, interfaced with VGA controller to ensure in real time applications.

Space Time State Trellis Codes for MIMO Systems Using Reconfigurable Antennas

We present a novel class of space time trellis codes based on super quasi-orthogonal space time codes for a reconfigurable antenna system. We call them space time state trellis codes (STSTCs). We design for 4 trellis states and both 2 and 4 branch trellis structures for BPSK and QPSK constellations. The proposed codes take advantage of the additional degrees of diversity offered by reconfigurable antennas and changing propagation states. They achieve full rate, full diversity and high coding gain. Simulation results demonstrate their good performance. STSTCs achieve the diversity order expected of four transmit antennas while using only two reconfigurable transmit antennas. Our code out performs the existing super orthogonal space time trellis code, which fails to achieve full diversity in a reconfigurable antenna system. The proposed 4 trellis state STSTC is designed based on the following performance criteria: minimum coding gain distance of the minimum return path (CGD MRP), performance factor (PF), rank of the partial valid path (RPVP) on top of traditional minimum coding gain distance of parallel path (CGD PP). We show through analysis and simulations that minimum CGD PP is not a sufficient criteria and that additional performance gains are provided by considering the CGD MRP.