Previous works withM-ary differential chaos shift keying (MDCSK) schemes are designed for resisting the impulsive noise of power line communication (PLC). However, real PLC channel environments are complex, existing schemes primarily address impulsive noise but do not effectively reflect the advantages of the system in a real PLC environment. This paper first discusses the bit-error-rate (BER) performance of the MDCSK system in Katayama PLC environments, and designs a derivation scheme of time slots-dependent BER. Then, based on the characteristics of periodic changes in the Katayama PLC channel environment, an adaptive-MDCSK (AD-MDCSK) is proposed to obtain better BER performance in such environments, which eliminates the need for a device to pre-check the BER. In the proposed scheme, the two types of MDCSK schemes are switched with the time slots period changing, where two categories of detectors are also changed correspondingly at the receiver. The BER of the AD-MDCSK is derived and analyzed regarding its effectiveness over Katayama PLC channel. The simulation results verify the accuracy of the design and show the superior performance of the proposed scheme. The BER performances of the proposed system are compared to other existing schemes, demonstrating its better BER performance.

A protograph low-density parity-check (P-LDPC) code-based lossy coding system is proposed for compressing the Gaussian mixture model source, as a particular case of shipping transportation systems. The compression performance is benchmarked against the rate-distortion bounds for this source. Some effective methods are developed to improve both the encoder and the decoder to reduce the compression distortion. Experimental results demonstrate that the proposed methods achieve good performance while maintaining low complexity.

Abstract This paper proposes a multilevel cyclic shift index modulation aided differential chaotic shift keying (MCSI‐DCSK) system to improve data rate and energy efficiency. In the MCSI‐DCSK system, the bit stream is divided into blocks with bits which are further divided into N groups equally. In each group, the first M bits are mapped into an index of cyclic shift in the chaotic reference sequence, while the last bit is used to modulate the shifted chaotic reference sequence. Finally, the all modulated shifted chaotic reference sequences are superimposed to form the information‐bearing signal. So the proposed system improves the data rate. The analytical bit‐error‐rate (BER) expressions of the MCSI‐DCSK system are derived over additive white Gaussian noise and multipath Rayleigh fading channels and validated via simulations. In addition, the BER performance of the proposed system is compared with other non‐coherent, chaotic communication systems. Simulation results indicate that the MCSI‐DCSK system has better performance in data rate and BER.

Device-to-device (D2D) communications can allow different devices to communicate in short range, which greatly meets the demand of effective transmissions. In this paper, a spectral and energy-efficient carrier index keying-aided$M$-ary differential chaos cyclic shift keying (CIK-MDCCSK) system is proposed for D2D communications, where multiple cyclic-shifted$M$-ary information-bearing signals are superimposed and transmitted by a subcarrier, and extra keying bits are transmitted by indices of the selected subcarriers. Furthermore, a carrier keying detection and$M$-ary de-mapping algorithm is proposed to retrieve the information bits transmitted by$M$-ary symbols and indices of carrier keying. The bit error rate (BER) expressions of the proposed CIK-MDCCSK system are derived over the additive white Gaussian noise (AWGN) and D2D channels, and the optimal power coefficient is deduced for performance enhancement. Then, the spectral efficiency, energy efficiency, and complexity of CIK-MDCCSK are analyzed and compared to benchmark systems to show its superiority. Next, the proposed CIK-MDCCSK system is expanded into its enhanced version for more effective transmission without degrading the BER performance. It is demonstrated by performance comparisons that the proposed CIK-MDCCSK system can achieve more than twice energy efficiency and up to 3 dB gain in BER performance compared to state-of-the-art benchmarks.

Chaotic secure communication systems using chaotic waveforms as their spreading carriers can hide the transmitted information bits over a wide frequency range of chaotic waveform, which disguises the transmitted information waveform as noise. In this paper, a reconfigurable intelligent surface (RIS) enabled$M$-ary differential chaos shift keying with block interleaving (RIS-MDCSK-BI) system is proposed for chaotic secure communications, where an RIS is deployed at the transmitter to assist communications and a pair of block interleaving patterns are used to interleave$M$-ary information-bearing signals to enhance security performance. Moreover, we propose a chaotic merging sort algorithm to generate different block interleaving patterns, where these interleaving patterns are encrypted by using the non-periodic and noise-like properties of chaotic signals. To estimate information bits at the legitimate receiver, we propose a sequential detection algorithm and a joint detection algorithm. Then, theoretical bit error rate (BER) performances of the proposed RIS-MDCSK-BI system with the legitimate receiver and the eavesdropping receiver are derived. The security performance metrics, including information leakage and secrecy outage probability, are also analyzed. Monte Carlo simulations are performed to verify the superior BER performance and security performance of the proposed RIS-MDCSK-BI system compared to benchmark systems.

A lossy source coding system based on the protograph low-density parity-check (P-LDPC) code is proposed for Gaussian source compression. In the proposed system, the conventional belief propagation (BP) algorithm is modified to be a concatenated BP-inverse BP (BP-$i$BP) for encoding and decoding, where the$i$BP is constructed by a fully-connected layer of a neural network. Compared to the existing approximate message passing algorithm, the proposed BP-$i$BP realizes a float-to-bit compression with low complexity for arbitrary Gaussian sources. The BP-$i$BP is implemented based on the linking relation of the protograph; therefore, it is necessary to optimally design the protograph to obtain better rate-distortion function (RDF) performance. Regarding the coding optimal procedure, a mutual information iteration convergence (MIIC) algorithm is designed as the optimal criterion to determine the source P-LDPC code with minimum distortion. Inspired by the plane construction of quantum stabilizer code, a lattice topological splicing (LTS) algorithm is proposed for regularly building the protograph to reduce the code searching complexity. By using the MIIC and the LTS algorithms, the BP-$i$BP based on the designed P-LDPC code maintains good distortion performance close to the RDF limit.

For the double protograph low-density parity-check (DP-LDPC) code pair, indicating the source and channel codes utilized in the joint source channel coding, the coding optimization is generally implemented by the differential evolution searching with high complexity. In this paper, a new structured design of the DP-LDPC code pair is proposed based on Graph theory to reduce the searching complexity, namely mesh model-based merging (M3) method. Firstly, four basic mesh models are designed to merge the protographs at any dimension. According to the different structures of the source and channel codes, the merging boundary constraint is statistically established to limit the using number of basic models. Then, a prior sorting algorithm is proposed to arrange the selection priorities of basic models for source and channel codes, respectively, which greatly refines the merging accuracy. Since most of the degrees are symmetric and predetermined in the merged protographs, the searching complexity is significantly reduced when the merged protographs are used as the initial input. Finally, simulation results demonstrate that the merging DP-LDPC code pairs show better performances compared to the existing code pairs. Furthermore, the proposed M3 method is hardware-friendly in Internet of Things because of its simple structure.

The automatic identification system (AIS) is the automatic tracking system for automatic traffic control and collision avoidance services, which plays an important role in maritime traffic safety. However, it faces a possible security threat when the maritime mobile service identity (MMSI) that specifies the vessels’ identity in AIS is illegally counterfeited. To guarantee the communication security of AIS for preventing fraudulent devices, we design a novel lightweight Transformer-based network GLFormer for specific emitter identification (SEI) to provide an extra security layer for AIS terminal emitters. Concretely, the gated local attention unit (GLAU) and the gated sliding local attention unit (GSLAU) modules that combine a simplified gated attention unit (GAU) and a sliding local self-attention (SLA) are developed in GLFormer to extract the radio frequency fingerprint (RFF) features automatically from the raw in-phase signals. Especially, the simplified GAU focuses on more critical RFF features and filters out the irrelevant information from the raw signal to improve performance, which is also a single-head self-attention module with fewer parameters for lightweight. Meanwhile, the SLA limits self-attention operation to a window, introducing the inductive bias of local information to enhance performance further and reducing the quadratic computational complexity to linearity for efficiency. Experimental results demonstrate that the GLFormer achieves 96.31% and 89.38% identification accuracy in the constructed AIS transient and AIS steady-state datasets with 50 vessels, respectively. The 99.90% identification accuracy is achieved in the universal software radio peripheral (USRP) dataset with ten devices. It is not only better than the existing methods but requires much fewer parameters and lower computational complexity; besides, it is also suitable for working with long signal sequences.

In reconfigurable intelligent surface (RIS)-aided coherent communications, channel state information (CSI) is often assumed to be perfectly estimated at the receiver. However, perfect CSI cannot be available in practice. Furthermore, the complex and ever-changing channel makes the acquisition of accurate CSI often unaffordable because of the large overhead in transmitting pilot signals. Motivated by these considerations, a novel non-coherent RIS-aided joint index keying$M$-ary differential chaos shift keying (RIS-JIK-MDCSK) system is proposed in this paper, where the receiver can retrieve information bits by performing non-coherent correlation demodulation without requiring CSI, thereby reducing the system complexity. In RIS-JIK-MDCSK, the states of the reference signal, RIS elements, and information-bearing subcarriers are jointly optimized to devise a joint index keying mechanism, where additional information bits are implicitly transmitted by these state indices, thus increasing the throughput and spectral efficiency. Furthermore, an effective joint index keying detection algorithm is proposed to recover the information bits. The analytical bit error rate (BER) of RIS-JIK-MDCSK is derived over a Rayleigh fading channel. Other evaluation metrics, including the throughput, spectral efficiency, and system complexity are also analyzed and compared against benchmark systems. Numerical simulations are performed to evaluate the superiority of RIS-JIK-MDCSK compared to existing systems.

In the multiple sequences spread spectrum (MSSS) system, multiple cyclic shifted spreading sequences are superimposed to increase the data rate. This paper proposes a dual-mode MSSS system with index modulation aided by a secondary pilot symbol (DM-MSSS-IM) for underwater acoustic communication. The proposed system divides the bit stream into index bits and modulated bits. The modulated bits are mapped to dual-mode constellations. The index bits are used to select a place for the first modulation mode symbol. The unselected place is used to carry the second mode symbols, which is regarded as the secondary pilot symbol (SPS) to enhance channel estimation. The simulation results show that the proposed system achieves a higher data rate than the existing MSSS system over time-frequency doubly selective fading channels and underwater acoustic channels as the cost of a slight BER performance loss. Additionally, the field experiment verifies the superiority of the proposed scheme.

A Noise Suppression aided Multi-Carrier$M$-ary Differential Chaos Shift Keying (NS-MC-MDCSK) system is proposed here where each information subcarrier transmits an$M$-ary information-bearing signal and the$M$-ary constellation symbols are constructed by orthogonal Walsh codes to improve the energy efficiency. Exploiting the redundant information available in the received signal, we propose a noise suppression algorithm to suppress channel noise in the reference and$M$-ary information-bearing signals. In the proposed algorithm, correlation coefficients detected between the received reference and information-bearing signals are fed back to suppress the noise corrupting the signal received. This method reduces the channel noise significantly and provides an outstanding Bit Error Rate (BER) performance. A performance analysis is performed for the NS-MC-MDCSK system over Additive White Gaussian Noise (AWGN) and multipath fading channels. Finally, the BER performance of the NS-MC-MDCSK system is compared to that of other chaotic communications systems. It is shown that the NS-MC-MDCSK system offers better BER performance than its competitors.

A joint energy and correlation detection aided orthogonal frequency division multiplexing differential chaos shift keying (JECD-OFDM-DCSK) system is presented in this paper, where the reference and information-bearing signals of JECD-OFDM-DCSK are superimposed in the same time slot so that the phase offset between the reference and information-bearing signals is addressed. In JECD-OFDM-DCSK, only some subcarriers are activated and additional information bits are transmitted by the indices of these activated subcarriers, thereby improving the data rate while reducing the energy consumption. The energy efficiency, peak to average power ratio (PAPR) performance and system complexity of JECD-OFDM-DCSK are analyzed and then compared to other systems. The comparison results show JECD-OFDM-DCSK can obtain higher energy efficiency and better PAPR performance compared to its competitors at the cost of higher system complexity. Furthermore, the bit error rate (BER) expressions of JECD-OFDM-DCSK are derived in additive white Gaussian noise (AWGN) and multipath fading channels. Simulation results show that the BER performance of JECD-OFDM-DCSK outperforms that of other OFDM-based DCSK systems. Finally, JECD-OFDM-DCSK performs much better than other systems over the underwater acoustic (UWA) channel, which validates the robustness of JECD-OFDM-DCSK.

A CM2-S3 transmission link in wireless body area networks (WBAN) is implemented with a joint source channel coding (JSCC) system based on double protograph low-density parity-check (DP-LDPC) code pairs with high reliability and low power consumption. For the practicality and suitability considerations, the$M$-ary differential chaos shift keying scheme is introduced to modulate the CM2-S3 channel with better performance than the standard modulations in WBAN. Due to the non-Gaussian-like distribution of the CM2-S3 channel model, the initial joint protograph extrinsic information transfer (JPEXIT) algorithm does not work as a coding analysis tool. To solve this problem, a numerical Gaussian approximation is employed to modify the iterative mutual information function of the JPEXIT for achieving more precise output. Then, a joint code rate compatible (JCRC) method, designed with compatibility in resisting variable channel variances and adapting different source statistics, is proposed for optimizing the DP-LDPC code pairs. Based on the JCRC method, the code searching algorithm is simplified with lower complexity because of the reduced cycle-index. The simulation results show that optimized code pairs have better bit-error ratio performances compared to existing codes, which provides a strong technical support to promote high-quality data transmission in eHealthcare on the physical layer.

The joint source channel coding (JSCC) system is sensitive to the changing channel characteristics, because the optimally designed source-channel code pair always needs to be redesigned when the transmission environment is updated. A solution is to seek a common code pair for variable channels. Channel model 3 (CM3) is a variable on-body channel following the Weibull distribution, which is analyzed in four conditions due to varying shape factors, namely with exponential, Rayleigh, log-normal and normal distributions. The JSCC system is considered in this paper based on double protograph low-density parity-check (DP-LDPC) code pair over the variable CM3 channel. Firstly, four DP-LDPC code pairs are searched by the conventional differential evolution (DE) algorithm with four distributions of the Weibull model, respectively. However, these four code pairs only present good bit-error ratio performance in their own distribution, and have error floors in the other three. To resolve the problem, an artificial intelligence method based on principle component analysis (PCA) algorithm is designed to extract the common code pair. It is demonstrated that the common code pair performs well in noise-varying and practical-parameter transmissions. Instead of four DE code pairs, the designed one PCA code pair provides a strong technical support to low-complexity manufacturing such as eHealthcare.

Given the high transmission loss, severe Doppler spread and large multipath delay in the underwater acoustic (UWA) channel, the channel estimation and tracking in the conventional orthogonal frequency division multiplexing (OFDM) based UWA systems are severely unaffordable. In this paper, we propose a low-complexity and cost-friendly OFDM-based differential cyclic-shifted differential chaos shift keying (OFDM-DCS-DCSK) system which offers a high data rate, superior robustness and enhanced system security for UWA communications without the need for channel state information (CSI). In the system, the information bits are carried by different step lengths of the cyclic shifts. At the receiver, a low-complexity detection method is used to search the position of maximum from the cyclic correlation values and therefore estimate the information bits. Finally, simulation results demonstrate the proposed OFDM-DCS-DCSK system outperforms its competitors both in bit error rate (BER) performance and in system security.

Probabilistic amplitude shaping (PAS) has proved to be a promising way to achieve the shaping gain for an additive white Gaussian noise channel with a distribution matcher (DM). However, the DM schemes may suffer a rate loss and increase both complexity and latency, when they are not suited for the input bit stream with redundancy. In this paper, a novel PAS strategy is proposed for a joint source and channel coded modulation system, where the residual source redundancy after source coding can be exploited to obtain both shaping and coding gains. It is shown that the residual source redundancy can be controlled by choosing the row weight distribution for source code, thus making the probability distribution of the modulated symbols be optimized under an appropriate interleaver design. To guarantee the error-floor performance, the source code is constrained by predicting the probability distribution of source bits within target finite-length frames. By jointly designing source and channel codes, the residual source redundancy can also be exploited to achieve the coding gain. Compared with the state-of-the-art code pairs, the proposed code pairs have better error-floor performance, and achieve higher coding and shaping gains without suffering from the rate-loss and the latency caused by DM.

In this paper, we propose a Sparse Code Spreading-aided Multi-Carrier Differential Chaos Shift Keying (SCS-MC-DCSK) transceiver to improve the efficiency and reliability performances for multiuser transmissions. With the aim to improve the spectrum efficiency and enhance the reliability, we construct a multi-dimension codebook based on a factor graph matrix to spread information bits in a non orthogonal way, thus the signals could overlap and multiple users are allowed to share all sub-carrier resources via the non orthogonal spreading. The information bits using the same codebook are regarded as a layer, while each user could choose to use one or multiple layers. Then the resultant symbols are spread by the reference chaotic sequence and its quadrature version generated by Hilbert transform in the time domain. At the receiver, reverse operations are conducted, and we propose the Minimum Distance (MD) detection method to retrieve the estimates. Furthermore, theoretical performances, including the Symbol Error Rate (SER), capacity, energy efficiency, spectrum efficiency and computational complexity, are analyzed and compared among the proposed design and benchmarks. Simulation results are then provided to validate the theoretical analysis. Moreover, the Bit Error Rate (BER) performances under different channel conditions demonstrate the superior reliability and efficiency to benchmarks.

In this paper, we focus on designing a high-data-rate noncoherent chaotic communication scheme to satisfy the demand of the explosive growth in data traffic. To achieve this goal, a joint time-frequency index modulation assisted multiple-mode DCSK (JTFIM-MM-DCSK) system is proposed, where a pair of distinguished signal modes are modulated into the selected subcarriers and another signal mode is transmitted by the unselected subcarriers. In this configuration, besides the modulated bits used for physical transmission, the carrier index bits and time slot index bits, conveyed by the state of whether subcarriers and time slots are selected or not, are also transmitted implicitly to achieve higher data rate. Moreover, the design of multiple-mode signals ensures that it is taking full advantage of all subcarriers and time slots to transmit the information bits, thereby improving the data rate significantly. The bit error rate (BER) expressions of the JTFIM-MM-DCSK system are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels, which are checked by computer simulations. Finally, the advantage of the JTFIM-MM-DCSK system over other up-to-date noncoherent chaotic communication systems is demonstrated in terms of BER performance through extensive computer simulations.

It has been demonstrated that the cubic convolution spline interpolation (CCSI) scheme is one of the best algorithms for image resampling or compression. In this paper, a new simple direct computation of CCSI is proposed, where the sampled data are directly calculated by the use of the original data. Moreover, the proposed algorithm provides a regular and simple structure based on linear correlation and thus is naturally suitable for VLSI implementation. Computer simulations on several standard images indicate that the proposed simple direct computation of CCSI scheme can achieve almost the same objective and subjective performance with lower complexity.

A new multicarrier M-ary orthogonal chaotic vector shift keying with index modulation (MC-MOCVSK-IM) is presented in this paper. In this design, information bits are conveyed not only by the multiple groups of M-ary information bearing signals, but also by the specific indices of the selected reference signals which depend on the incoming mapped bits. Benefiting from the favorable features of multicarrier modulation, M-ary modulation and index modulation, MC-MOCVSK-IM system is capable to offer higher energy efficiency and spectral efficiency at some expense of hardware complexity. In addition, the analytical bit error rate (BER) expressions of MC-MOCVSK-IM system are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. The BER performance comparison between MC-MOCVSK-IM system and other non-coherent chaotic communication systems is carried out to highlight the superiority of MC-MOCVSK-IM system in terms of BER performance. Considering the dramatically increased demand for high-data-rate transmission and the harsh environment of future wireless communication, MC-MOCVSK-IM system shows strong robustness and offers competitive solutions for high-data-rate non-coherent chaotic communication systems.

The joint base matrix BJof the joint source-channel coding (JSCC) system based on double protograph low-density parity-check (DP-LDPC) codes consists of four components, namely, the source code Bs, the channel code Bc, the type1 connection edge BL1and the type-2 connection edge BL2, each having a non-negligible influence on the system performance. Different from the traditional component-specific design approach, we propose a joint design and optimization algorithm based on the idea of multi-objective differential evolution (MODE). Specifically, we consider the optimization of the DP-LDPC JSCC system through joint design of three components Bs, Bc, BL1and all four components Bs, Bc, BL1, BL2, respectively. The proposed algorithm has low search complexity due to the reduction in size and element value of base matrices. The joint protograph extrinsic information transfer (JPEXIT) analyses and the simulation results demonstrate that the resulting JSCC system is free from a high error floor, requires fewer number of iterations for reaching the same bit error rate (BER) and achieves significant coding gains as compared to the state-of-the-art. Our DP-LDPC JSCC system is also shown to outperform its separation-based counterpart by a wide margin.

A new M-ary differential chaos shift keying with index modulation (IM-MDCSK), which has the advantages of high data rate and low energy consumption, is proposed in this paper. In the proposed scheme, each data frame is divided into several time slots where the reference signal is placed in the first time slot and the rest time slots with specific indices are provided for information bearing signals. More exactly, the information bearing signals with active indices are modulated by M-ary DCSK symbols, and the active indices are determined by mapped bits via the combination number mapping method. At the receiver, the absolute values of decision variables in all branches are used to find the indices of active time slots, while M-ary DCSK demodulation is applied to recover the modulated bits. Moreover, we derive the analytical bit-error-rate (BER) expressions for the proposed scheme over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels, and then simulation results verify our theoretical derivations. Finally, the performance of IM-MDCSK scheme is compared with M-ary DCSK and other up-to-date chaotic modulation schemes based on index modulation (IM). IM-MDCSK scheme is proved to be competitive and preeminent.

A novel near lossless image compression method is proposed in this paper. In the proposed method, a redundant representation of the image is firstly obtained by pixel level shifting and then partitioned into image blocks with the same size. Next, the image blocks are classified into smooth image blocks and non-smooth image blocks. For the smooth image blocks, improved block coding which includes mean residual error is utilized for pixel rectangles with the same pixel value in each to remove the redundancy. Lastly, the whole image is scanned by efficient image scanning that only one pixel is scanned for each pixel rectangle and then compressed by Huffman coding. Simulation results indicate that the proposed method has good performance compared with traditional lossless/near lossless image compression methods.

In this study, an M ‐ary code‐shifted differential chaos shift keying system with in‐phase and quadrature code index modulation (I/Q‐CIM‐CS‐MDCSK) is presented. In the proposed system, the information bits are conveyed not only by the M ‐ary constellation symbols, but also by the specific Walsh codes indices corresponding to the in‐phase and quadrature branches of M ‐ary information bearing signals. Since the reference signal and the multiple M ‐ary information bearing signals are overlapped and transmitted within the identical time slot in a parallel manner, the spectral efficiency of the I/Q‐CIM‐CS‐MDCSK system is enhanced significantly. In addition, the analytical bit error rate (BER) expressions for the presented system are derived under the additive white Gaussian noise and multipath Rayleigh fading channels. Finally, the BER performance of the proposed system is compared to other chaotic communication systems. The results manifest that the I/Q‐CIM‐CS‐MDCSK system is a promising and competitive chaotic communication scheme.

Multi‐carrier (MC) and spread‐spectrum (SS) are two good technologies for underwater acoustic (UWA) communications. In this study, the authors propose a novel MC chaos modulation scheme, which combines code‐shifted differential chaos shift keying (CS‐DCSK) with orthogonal frequency division multiplexing (OFDM), namely MC‐CS‐DCSK. The proposed scheme exploits the orthogonal characteristic of the Walsh code to superimpose the chaotic reference chips and the information bearing chips in the same time/frequency unit. Besides, a cyclic‐shift interleaver is used on chips to harvest frequency diversity. To the in‐depth understanding of the proposed system, the bit error rate (BER) of the proposed system under Gaussian channels and multipath Rayleigh fading channels are derived and verified by simulation. Furthermore, the spectral efficiency of the proposed system is analysed and compared with some existing chaos‐based communication systems. Finally, they study BER performance of the system under UWA channels and compare it with traditional MC direct sequence SS and OFDM‐based MC‐DCSK systems. Simulation results show that the system has good robustness under time‐varying UWA channels.

In this study, a new chaos modulation scheme which combines M ‐ary differential chaos shift keying (DCSK) with code‐index modulation (CIM‐MDCSK) is proposed. In the CIM‐MDCSK scheme, the two Walsh codes that are used to generate two orthogonal chaos components are selected from the candidate codes, whose code indices are determined by information symbols. Thus, the information bits are conveyed not only by M ‐ary DCSK signal but also by the indices of the Walsh codes. Theoretical symbol error rate (SER) and bit error rate (BER) of the proposed scheme are derived and confirmed by simulations. Furthermore, by applying the noise‐reduction to reference signals of CIM‐MDCSK, the SER/BER expressions are also derived. Simulation results show that the proposed CIM‐MDCSK outperforms DCSK and M ‐ary DCSK based on Hilbert transform. Especially, the CIM‐MDCSK with noise‐reduction shows significant advantages. Moreover, the performance of CIM‐MDCSK scheme is compared with direct sequences spread‐spectrum system with code‐index modulation over flat and frequency selective fading channel. The proposed CIM‐MDCSK can offer good performance over frequency selective fading channel with a low complexity non‐coherent receiver which does not require any channel state information and channel equalisation.

Sparse signal reconstruction algorithms in compressive sensing mainly focus on greedy algorithms, which are short-sighted. In this letter, an optimization-oriented algorithm using global optimization method is proposed to reconstruct the sparse signal. First, a pre-selection is made to estimate the most likely support of the sparse signal. Second, a backtracking strategy is introduced to avoid the over-fitting problem. Last, an optimization-oriented search strategy is designed to refine the pre-selected support toward the best estimate of the signal support. Numerical results demonstrate that the proposed algorithm performs better for sparse signal reconstruction with moderate computational complexity compared with the existing algorithms.

Joint-sparse signal reconstruction is a key issue in distributed compressed sensing based on the mixed support set model. In this letter, a novel joint-sparse signal reconstruction algorithm is proposed based on the common support set refinement. The common support set is first roughly estimated by greedy pursuit algorithms. The roughly estimated common support set is then refined by pruning the incorrect elements. With the refined common support set, greedy pursuit is utilized to reconstruct the joint-sparse signals. The complexity analysis and simulation results indicate that the proposed algorithm achieves better estimates of the support sets and finally reduces the reconstruction error for the joint-sparse signals with a moderate complexity compared with the state-of-the-art algorithms.

In this paper, a dual-mode differential chaos shift keying with index modulation (DM-DCSK-IM) is proposed. In the proposed system, the bit stream is partitioned into two subblocks, where the first subblock is the mapped bits used to select the active time slot, which presents the time slot's constellation mode, and the second subblock is the modulated bits, which are further divided into two groups and modulated by a pair of distinguishable modem-mode constellations, respectively. Unlike the recently proposed pulse-position-modulation differential chaos shift keying (PPM-DCSK), since both the active and inactive time slots are applied to convey the information bits, the data rate of the proposed system can be promoted significantly. In order to detect the active time slots and recover the mapped bits as well as modulated bits correctly, we propose an effective detection algorithm for the proposed system. Furthermore, the theoretical bit error rate (BER) expressions are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels, and the simulation results validate the accuracy of our derivations. Finally, the BER performance of the proposed system is compared with the other non-coherent chaotic communication systems, and the results indicate that the proposed system can offer competitive and satisfactory BER performance.

In this paper, an M -ary orthogonal multilevel differential chaos shift keying system with code index modulation (CIM-OM-MDCSK) is proposed. In the proposed system, the multiple information bearing signals are modulated by the selected Walsh codes with specific indices and the M -ary information signals which are composed of modulated bits, chaotic signals, and their Hilbert transform. Since the reference signal along with the information bearing signals are overlapping in time domain and orthogonal in code domain by using Walsh code sequences, the spectral efficiency of the CIM-OM-MDCSK system is improved largely. By combining the M -ary modulation, orthogonal multilevel modulation, and code index modulation, the proposed CIM-OM-MDCSK system can achieve high data rate and superior bit error rate (BER) performance compared to its rivals. Moreover, we derive the BER expressions of the proposed system over additive white Gaussian noise and multipath Rayleigh fading channels. Finally, we make a performance comparison between the proposed system and other state-of-the-art non-coherent chaotic communication systems. The results confirm the competitive benefits of the proposed system.

Cubic-spline interpolation (CSI) scheme is known to resample the discrete image data based on the least-square method with the cubic convolution interpolation (CCI) function. It is superior in performance to other interpolation functions for digital image processing. In this paper, an improved approach to the CSI scheme is proposed for the decimation and interpolation of image data. The proposed CSI scheme combines the least-square method with six-point CCI function to improve performance. Moreover, a novel low-complexity implementation algorithm is proposed to simplify the decimation and achieve improvement of the computational efficiency. Computer simulations indicate that the proposed CSI scheme can achieve better performance without increasing the computational complexity compared with the four-point CSI scheme.

In this paper, we propose a method for fusion of low-resolution multispectral (LRM) image and high-resolution panchromatic (HRP) image to obtain high-resolution multispectral (HRM) image based on distributed compressed sensing (DCS). In the proposed method, HRP image is firstly used to obtain approximation and detail dictionary. Then, joint-sparsity-model-1 (JSM-1) is applied directly to both LRM bands and HRM bands. Each band in LRM image is decomposed into common component and innovation component which can be sparsely represented over the approximation dictionary. Based on Orthogonal Matching Pursuit (OMP) algorithm, the sparse coefficients are calculated from JSM-1 of the LRM image. Lastly, each band in HRM image is modeled as the fusion of the corresponding LRM band and detail band over the detail dictionary. Two datasets are used in the experiments to validate the proposed method and the results show that the proposed method has better performance than the traditional methods.

In this paper, we propose a constellation-based differential chaotic bit-interleaved coded modulation system with iterative receiver (DC-BICM-IR) over power line channels (PLCs) and then design a new protograph-based low density parity check (P-LDPC) code for the system.

In this paper, we develop a novel serial concatenated trellis-coded differential chaotic modulation (SCTC-DCM) system, which combines serial concatenated trellis-coded modulation (SCTCM) with M-ary differential chaotic shift keying (M-ary DCSK). The proposed system has lower error floor than turbo trellis-coded differential chaotic modulation (TTC-DCM). At the same time, when the signal to noise ratio (SNR) is relatively high, SCTC-DCM scheme achieves better bit error rate (BER) performance. Moreover, simulation results show that the proposed scheme can obtain considerable coding gain compared with uncoded M-ary differential chaotic shift keying over AWGN channel. Furthermore, SCTC-DCM system inherits the advantages of chaos-based modulation system and does not require channel state information (CSI) at the receiver. Therefore, the proposed system can be applied to band-limited communication scenes with poor channel condition.

In this study, two generalised carrier index M ‐ary differential chaos shift keying (CI‐MDCSK) schemes are proposed, which combine index modulation with multicarrier M ‐ary DCSK (MC‐MDCSK). At the transmitter, two different index selectors based on two different mapping rulers are employed to select active carriers, where the modulated bits are transmitted by the active carriers through M ‐ary DCSK modulation, which is based on the Hilbert transform and constellation theory. At receiver, maximum or minimum energy detection is employed to determine the active carriers, where the bits carried on these active carriers are demodulated. The analytical bit error rate (BER) expressions over additive white Gaussian noise as well as multipath Rayleigh fading channels are derived. Simulations are performed with different numbers of carriers and different constellation sizes. Both analytical and simulation results show the superiority of the new schemes in BER performance or spectral efficiency (SE) compared with the MC‐MDCSK scheme. Moreover, compared with conventional DCSK, CI‐MDCSK schemes owns both better BER performance and SE in some cases, where the constellation is not greater than 8.

For a joint source–channel coding system based on double protograph low‐density parity‐check codes, the exchange of extrinsic information through edge connection between the source code and channel code is essential for good performance. In this study, the relationship between the performance and edge connection in the tanner graph is analysed and it has never been seen in the literature to the authors' knowledge. Both the joint protograph extrinsic information transfer and simulation results indicate that the edge connection should be optimised in practical applications since it plays an important role in the bit error rate performance and an optimisation scheme for the edge connection is put forward to enhance performance.

Coded modulation (CM) is a bandwidth efficient framework to approach the capacity limit of the differential chaos shift keying (DCSK) systems. In this paper, we propose an M-ary DCSK system operated with CM based on nonbinary protograph low-density parity-check (LDPC) codes over Rayleigh fading channels. First, we investigate the performance of the proposed nonbinary channel coded DCSK (CM-DCSK) and bit-interleaved coded DCSK (BICM-DCSK). In particular, we show that CM-DCSK outperforms BICM-DCSK over Rayleigh fading channels in terms of capacity limit. Compared with BICM-DCSK, CM-DCSK can simplify the receiver structure, since it does not require turbo iteration between the noncoherent detector and channel decoder. Second, guided by the modified extrinsic information transfer (EXIT) analysis, we put forth two new types of nonbinary protograph LDPC codes to approach the capacity limit of CM-DCSK. Both EXIT analysis and simulation results demonstrate that the proposed protograph-coded CM-DCSK achieves a better error performance than BICM-DCSK even with iterative decoding. Furthermore, we show the performance superiority of nonbinary protograph-coded CM-DCSK over a practical ultra-wideband channel. Hence, we conclude that this proposed scheme offers a good alternative for wireless local area network applications.

Double protograph low-density parity-check code has been shown to be a good solution for joint source-channel coding. Moreover, the source code and channel code (as one code pair) can be jointly optimized to achieve a good bit error rate (BER) performance. In this paper, first, an optimal design criterion of this code pair based on an extended curve-fitting algorithm is proposed. Second, a joint optimization procedure which searches for both the optimal decoding threshold and the optimal code pair is presented. In addition, for short-to-moderate-length codewords, the finite-length effect cannot be ignored and the procedure has to be modified with a new notion named length-N decoding threshold. The protograph extrinsic information transfer analysis and the BER simulation have shown that our optimized code pairs acquire lower decoding thresholds than conventional code pairs. Moreover, the optimized code pairs with short-to-moderate-length codewords can mitigate the finite-length effect and obtain low length-N decoding thresholds.

In this paper, a novel chaos modulation scheme, which combines code-shifted differential chaos shift keying (CS-DCSK) with orthogonal frequency division multiplexing (OFDM) is presented, namely OFDM-CS-DCSK. In the proposed scheme, the reference signal and the information bearing signal of CS-DCSK are firstly formed by Walsh code sequences, then different chips of the CS-DCSK signal are mapped onto different subcarriers of OFDM. Utilizing the characteristics of OFDM and CS-DCSK, the proposed scheme has robust performance over time-frequency doubly selective fading channel. In addition, the proposed system has low complexity because channel estimation, channel equalizer and the radio frequency (RF) delay circuits are not required at its receiver. By the computer simulations, bit error rate (BER) performances of the proposed scheme are compared with OFDM-DCSK and CS-DCSK under various channel parameters. Simulation results indicate that the proposed scheme has significant performance advantages over OFDM-DCSK and CS-DCSK in time-frequency doubly selective fading channel.

With the rapid development of narrow band power-line communications (NPLC) in recent years, many effective modulation schemes have been proposed for it. In this paper, we propose M-ary differential chaotic shift keying (M-DCSK) for Narrow Band (NB) PLC. Firstly, which improves the bandwidth efficiency compared with DCSK scheme. The performance of M-DCSK scheme is analyzed over PLC channels where background, impulsive and phase noise exist. Simulation results verifiy the accuracy of the derived theoretic performance. Due to the inner properties of chaotic carrier, M-DCSK shows good robustness against multipath fadings and phase noises, which are very common in PLC channels. Besides, comparing with the traditional direct sequence M-ary differential phase shift keying (DS-MDPSK) scheme, M-DCSK can achieve better bit error rate (BER) performances.

The turbo trellis-coded differential chaotic modulation (TTC-DCM) is a newly proposed scheme, which is very suitable for bandlimited communication applications with poor channel conditions due to the merits of high bandwidth efficiency, robustness to multipath fading and easy-to-implement property. In this paper, in-phase and quadrature-phase (IQ) interleaved turbo trellis-coded differential chaotic modulation (IQ-TTC-DCM) scheme is proposed, which is capable of increasing the diversity order of conventional TTC-DCM. The IQ-TTC-DCM can obtain significant gains while communicating over fading environment, compared with TTC-DCM scheme. Besides, a code search algorithm utilizing the Extrinsic Information Transfer (EXIT) charts is proposed, aiming to find the component code with the best convergence behavior. The searched codes for different channels are presented for 8-state 8-DCSK TTC-DCM scheme and simulations are carried out to testify their superiorities.

The cubic‐spline interpolation (CSI) scheme is known to be designed to resample the discrete image data based on the least‐square method in conjunction with the cubic convolution interpolation (CCI) function. In this CSI scheme, the improved quality of resampling can be achieved as the interpolation kernel size increases. However, the improvement of the performance gets less and less. This means that the performance of the CSI scheme has not been significantly improved and converges toward a constant value when the interpolation kernel size exceeds a certain value. A proof of this result is given in this study and has never been seen in the literature to the authors' knowledge. Moreover, this study analyses the relationship between the performance and computational complexity of the CSI schemes with different interpolation kernel sizes and compares them from a structural point of view. Simulation results indicate that it is in agreement with the theoretic derivations. Since the arithmetic operations required are increasing linearly with the increment of the interpolation kernel size, selecting an interpolation kernel size gives the best trade‐off between the performance and computational complexity in practical applications. However, the optimum choice of the interpolation kernel size depends crucially on effective demand.

In the general code-shifted differential chaos shift keying (GCS-DCSK) system, multiple bit-streams are simultaneously carried by CS-DCSK signal using Walsh codes. However, its data rate is limited by the available Walsh codes in the Walsh code matrix due to orthogonality constraint of GCS-DCSK signal. In this paper, we propose a new GCS-DCSK scheme with code index modulation (CIM-CS-DCSK), which can achieve higher spectrum efficiency using code index modulation to carry additional bits. In the proposed scheme, the reference chaotic signal is the same as that of GCS-DCSK, and the multiple information bearing signals are simultaneously modulated by the information symbols and the selected Walsh codes with specific indices, which are determined by an integer sequence mapped from information symbols via the natural numbers to k-combinations mapping method. We derive bit error rate of the proposed scheme over the additive white Gaussian noise channel. The numerical results not only verify our analysis but also show the advantage of the proposed scheme over GCS-DCSK. Through analyzing and comparing the numbers of carried bits per transmitted symbol of CIM-CS-DCSK and GCS-DCSK, it is shown that the proposed scheme can obtain higher data rate than GCS-DCSK with the same resource constraints.

In this paper, a novel differential chaotic bit-interleaved coded modulation (DC-BICM) system is proposed for band-limited transmission. This system combines protograph-based low density parity check codes with constellation-based M-ary differential chaos shift keying (DCSK) modulation by one bitwise interleaving. Bit error rate simulation results show that the system has higher coding gain compared with the constellation-based M-ary DCSK modulation system with the same spectral efficiency over multipath Rayleigh fading channels. At the same time, several simulations and P-EXIT analysis are used to analyze the performance of the proposed system. It is found that there is a lot of room for optimization of the system by comparing decoding thresholds and simulation results. Moreover, the system with only partial channel state information has better performance and lower complexity compared with the traditional bit-interleaved coded modulation (BICM) directsequence-spread-spectrum system. As a result, the DC-BICM system is a good candidate for band-limited transmission.

In this paper, we deal with the problem of maximum likelihood (ML) estimation of the signal-to-noise ratio (SNR) parameter for frequency modulated differential chaos shift key (FM-DCSK) system over multipath Rayleigh fading channels. The ML estimators are derived for various scenarios including data-aided (DA), non-data aided (NDA) and joint DA-NDA estimation by using both the data and pilot symbols. For comparison purposes, the Cramér- Rao lower bounds (CRLBs) for the SNR estimators are derived. The performance of the estimators is evaluated by simulations and comparing with CRLBs in terms of the mean-square-error. Simulated results show that for a large spreading factor the proposed scheme performs well over a wide SNR range in comparisons with CRLBs

In this paper, we investigate the secrecy performance of the multiple-input multiple-output (MIMO) wiretap channels in the presence of an active full-duplex eavesdropper with consideration of channel estimation error at the legitimate destination and eavesdropper. For this purpose, the probability density functions (PDFs) and cumulative density functions (CDFs) of the receive signal-to-interference-plus-noise ratio (SINR) at the destination and eavesdropper are given by conducting the singular value decomposition (SVD) on the estimated channel coefficient matrices. Consequently, the closed- form expressions for the probability of positive secrecy capacity and secrecy outage probability over Rayleigh fading channels are derived. Finally, the Monte-Carlo simulation results are presented to validate the accuracy of our theoretical analysis.

In order to improve the error performance of M-ary differential chaotic shift keying (DCSK) systems over multi-path fading channel, two types of iterative structures have been employed in receiver design. One is joint source-channel decoder (JSCD), the other is iterative receiver (IR). Although several works have separately addressed the advantages of IR and JSCD, it is not clear which design provides more iterative gain for M-ary DCSK systems over multi-path fading channels. In this work, we employ the extrinsic information transfer (EXIT) chart technique to analyze the iteration behavior of JSCD and IR. Simulation results suggest that with enough source redundancy, JSCD outperforms IR under M-ary DCSK systems over multi-paths fading channels.

A novel spectrum sensing approach based on distribution discontinuity estimation facilitated by change-point (CP) detection algorithm has been presented in this work. Specifically, a Markov Chain Monte Carlo (MCMC) based CP detection algorithm to estimate the variations in the distribution over the received signal is developed. Primary User (PU) activity, autonomous classification of modulation and detection of PU emulation attempts are detected using the CP- Maximum Likelihood Estimation (MLE) framework. Specifically, the CP based approach facilitates PU activity detection and initiates the MLE based mechanism to discern or reveal the underlying modulation scheme within the received signal. Thus, the proposed joint CP-MLE framework not only aims at detecting the discontinuity or the variations in the underlying distribution over the sensed signal, but also helps in attributing those variations to distinct modulation schemes, in an effort to identify PU emulation attempts. This CP- MLE framework has been extensively validated using the Universal Software Radio Peripheral (USRP) devices for various types of scenarios involving real-time modulation classification and identification of PU emulation type attacks.

Capacity bounds are calculated for the differential chaos shift keying (DCSK) system with non‐coherent detectors, including differentially coherent detector and energy detector, over additive white Gaussian noise (AWGN) and Rayleigh fading channels. Through theoretical analysis and numerical simulations, it is found that the capacity characteristics of the non‐coherent DCSK system are significantly different from those of the coherent case. It is shown that there are different capacity bounds corresponding to different spreading factor values. Optimal code rates are found, which minimise the required bit signal‐to‐noise ratio for a reliable communication system, and they are increasing with the increase of the spreading factor value over an AWGN channel while decreasing over a Rayleigh fading channel. As compared with the AWGN channel, the performance over a Rayleigh fading channel is much more sensitive to the code rate. The new results are useful as benchmark for designing capacity‐approaching codes for the non‐coherent DCSK system.

The M ‐ary differential‐chaos‐shift‐keying ( M ‐ary DCSK) system offers a good noise performance over an additive white Gaussian noise (AWGN) channel in the category of non‐coherent detection chaotic systems. However, the way that the M ‐ary DCSK system utilises the available Walsh codes results in a relatively low bandwidth efficiency (BE). Moreover, the number of delay elements required at the transmitter and receiver increases exponentially with the number of bits per symbol. To overcome the aforementioned problems, the authors propose a multilevel code‐shifted DCSK (MCS‐DCSK) system in this study. In the proposed MCS‐DCSK system, the reference chaotic signal and the information‐bearing chaotic signals are orthogonal and are transmitted in the same time slot. They show that the MCS‐DCSK system significantly outperforms the M ‐ary DCSK system in terms of BE and complexity. They also derive analytical bit‐error‐rate expressions for the MCS‐DCSK system over additive white Gaussian noise and multipath fading channels, and verify them with simulation results.

Presents comments on the paper, "On decoding of the quadratic residue code,” (Wang, L., et al) IEEE Trans. Commun., vol. 61, no. 3, pp. 832–841, Mar. 2013.

Although the performance of a differential chaos shift keying (DCSK) system can be improved by designing appropriate channel codes, it is still a great challenge to do so for various channel models through transmitter and receiver designs, particularly with short frame length transmissions. Alternatively, to bypass the difficult task of designing a good channel code, an iterative receiver (IR) DCSK system is proposed in this paper. A soft demapper suitable for non-coherent M-ary DCSK system is presented, which can work either with or without fading amplitude information. Bit error rate (BER) performance shows its advantages over the non-IR DCSK system in different channel models. The achievable rate curves also indicate that gains relative to non-iterative DCSK system can be achieved with the iterative receiver.

A new multiresolution M-ary differential chaos shift keying (DCSK) modulation scheme is proposed in this paper. It is a promising technique for providing a different quality of service for transmitted bits within a symbol according to their different bit error rate (BER) requirements based on the principle of nonuniformly spaced constellations. The new system not only is simple but also provides better antimultipath fading performance against various spreading factors, inheriting the advantages of the conventional DCSK system. Furthermore, the proposed scheme and its multicarrier version further increase spectral efficiency and use lower energy consumption at the same bandwidth as compared with the conventional DCSK and its multicarrier system. Explicit BER expressions of the new system are derived and analyzed over additive white Gaussian noise and multipath Rayleigh fading channels. All simulation results verify the prominent advantages of the new scheme and the accuracy of the new analytical approach.

It is still an open challenge in coding theory how to design a systematic linear ( n , k ) − code C over GF(2) with maximal minimum distance d . In this study, based on matroid theory (MT), a limited class of good systematic binary linear codes ( n , k , d ) is constructed, where n = 2 k − 1 + · · · + 2 k − δ and d = 2 k − 2 + · · · + 2 k − δ − 1 for k ≥ 4, 1 ≤ δ < k . These codes are well known as special cases of codes constructed by Solomon and Stiffler (SS) back in 1960s. Furthermore, a new shortening method is presented. By shortening the optimal codes, we can design new kinds of good systematic binary linear codes with parameters n = 2 k − 1 + · · · + 2 k − δ − 3 u and d = 2 k − 2 + · · · + 2 k − δ − 1 − 2 u for 2 ≤ u ≤ 4, 2 ≤ δ < k . The advantage of MT over the original SS construction is that it has an advantage in yielding generator matrix on systematic form. In addition, the dual code C ⊥ with relative high rate and optimal minimum distance can be obtained easily in this study.

In this paper1, we propose a novel cooperative scheme to enhance the performance of multiple-access (MA) differential-chaos-shift-keying (DCSK) systems. We provide the bit-error-rate (BER) performance and throughput analyses for the new system with a decode-and-forward (DF) protocol over Nakagami-m fading channels. Our simulated results not only show that this system significantly improves the BER performance as compared to the existing DCSK non-cooperative (DCSK-NC) system and the multiple-input multiple-output DCSK (MIMO-DCSK) system, but also verify the theoretical analyses. Furthermore, we show that the throughput of this system approximately equals that of the DCSK-NC system, both of which have prominent improvements over the MIMO-DCSK system. We thus believe that the proposed system can be a good framework for chaos-modulation-based wireless communications.

In this study, the authors investigate the error performance of the protograph (low‐density parity check) codes over Nakagami‐ m fading relay channels. The authors first calculate the decoding thresholds of the protograph codes over such channels with different fading depths (i.e. different values of m ) by exploiting the modified protograph extrinsic information transfer (PEXIT) algorithm. Furthermore, based on the PEXIT analysis and using Gaussian approximation, the authors derive the bit‐error‐rate (BER) expressions for the error‐free (EF) relaying protocol and decode‐and‐forward (DF) relaying protocol. The authors finally compare the threshold with the theoretical BER and the simulated BER results of the protograph codes. It reveals that the performance of DF protocol is approximately the same as that of EF protocol. Moreover, the theoretical BER expressions, which are shown to be reasonably consistent with the decoding thresholds and the simulated BERs, are able to evaluate the system performance and predict the decoding threshold with lower complexity as compared with the modified PEXIT algorithm. As a result, this work can facilitate the design of the protograph codes for the wireless communication systems.

This letter develops a log-likelihood-ratio-based decoder for a generalized joint channel-coding-and-physical-network coding used in a two-way relay system. Assuming that the same low-density parity-check codes are used at the source nodes, the proposed decoder shows identical error performance as the probability-domain-based decoder but with a much lower computational complexity.

This work investigates the joint detection and decoding of MIMO-OFDM signals. Traditional receivers either utilize disjoint serial detector and decoder or require turbo message passing between the two functional blocks of detection and decoding. We present a novel approach that can jointly achieve detection and decoding of low density parity check (LDPC) coded multiple-input-multiple-output (MIMO) orthogonal-frequency-division-multiplexing (OFDM) signals as a unified optimization algorithm. Our receiver integrates the MIMO-OFDM signal detection and the decoding of LDPC coded data by formulating a linear programming problem regardless of affine or nonaffine quadrature amplitude modulation (QAM) mapping. The proposed joint MIMO-OFDM detector and decoder achieves substantial performance gain over existing joint detection receivers of comparable computational complexity. Furthermore, the proposed receiver also substantially outperforms the more traditional turbo receiver with only modest cost in complexity.

In this paper, Three decoding methods of the (89, 45, 17) binary quadratic residue (QR) code to be presented are hard, soft and linear programming decoding algorithms. Firstly, a new hybrid algebraic decoding algorithm for the (89, 45, 17) QR code is proposed. It uses the Laplace formula to obtain the primary unknown syndromes, as done in Lin et al.'s algorithm when the number of errors v is less than or equal to 5, whereas Gaussian elimination is adopted to compute the unknown syndromes when v ≥ 6. Secondly, an appropriate modification to the algorithm developed by Chase is also given in this paper. Therefore, combining the proposed algebraic decoding algorithm with the modified Chase-II algorithm, called a new soft-decision decoding algorithm, becomes a complete soft decoding of QR codes. Thirdly, in order to further improve the error-correcting performance of the code, linear programming (LP) is utilized to decode the (89, 45, 17) QR code. Simulation results show that the proposed algebraic decoding algorithm reduces the decoding time when compared with Lin et al.'s hard decoding algorithm, and thus significantly reduces the decoding complexity of soft decoding while maintaining the same bit error rate (BER) performance. Moreover, the LP-based decoding improves the error-rate performance almost without increasing the decoding complexity, when compared with the new soft-decision decoding algorithm. It provides a coding gain of 0.2 dB at BER = 2 × 10-6.

The cubic-spline interpolation (CSI) scheme can be utilized to obtain a better quality reconstructed image. It is based on the least-squares method with cubic convolution interpolation (CCI) function. Within the parametric CSI scheme, it is difficult to determine the optimal parameter for various target images. In this paper, a novel method involving the concept of opportunity costs is proposed to identify the most suitable parameter for the CCI function needed in the CSI scheme. It is shown that such an optimal four-point CCI function in conjunction with the least-squares method can achieve a better performance with the same arithmetic operations in comparison with the existing CSI algorithm. In addition, experimental results show that the optimal six-point CSI scheme together with cross-zonal filter is superior in performance to the optimal four-point CSI scheme without increasing the computational complexity.

In this work1, we present a new multiple-input-multiple-output (MIMO) receiver that integrates the MIMO signal detection and the decoding of low density parity check coded data. This joint MIMO detector and decoder utilizes linear programming and achieves about 9.0 dB gain over existing works in terms of bit error rate (BER) of 4 × 10−5with comparable computational complexity. The proposed detector also outperforms the classic turbo equalizer by achieving up to 4.0 dB improvement over turbo equalizer at frame error rate (FER) of 1 × 104. In fact, we can achieve further gain by improving the proposed joint detector through the use of redundant parity checks.

This paper evaluates the bit error rate (BER) performance of a code-shifted differential chaos shift keying (CS-DCSK) ultra-wide bandwidth (UWB) system over indoor communication channels under the impact of both single and multiple narrow band interference (NBI) signals. We analyze the BERs both in single NB interferer and multiple NB interferes. The analytic results and simulation results show that NBI signal has a noticeable impact on the performance of UWB systems which are independent of the carrier frequency.

In this paper, a differential chaos shift keying (DCSK) opportunistic relaying scheme is proposed and the system performance is analyzed over multipath Rayleigh fading channel, where all the relays adopt decode-and-forward (DF) strategy. Considering the effect of the path loss, the best relay is chosen by max-min selection criterion. We derive the probability density function (PDF) of the signal noise ratio (SNR) in each hop, and give the expression of the end-to-end bit error rate (BER). The effects of the number of relays, the propagation distance and the spread-spectrum factor on the system performance are investigated. It is shown that the BER performances are proportional to the number of relays and the propagation distance, while they are inverse ratio to the spread-spectrum factor. Numerical results prove an excellent match between simulations and our analysis expressions.

As the demand for e-Health care increases quickly, the transmission of medical images has been a crucial problem which needs to be solved as soon as possible. In the last decade, joint source-channel coding (JSCC), which combines the source coding with the channel coding reasonably to build an integral system so as to obtain significant improvement of system performance has attracted much attention. A framework of transmitting medical images by a P-JSCC scheme constructed from protograph low-density parity-check (P-LDPC) codes is proposed in this paper. Without loss of generality, we exploit a typical radiography image for simulation, and experimental results show that the receiver can recover the transmitted radiography image with good quality even at a very low signal-to-noise ratio (SNR); the P-JSCC scheme outperforms irregular-JSCC and regular-JSCC.

In wireless communications, spatial diversity techniques, such as space-time block code and single-input multiple-output (SIMO), are employed to strengthen the robustness of the transmitted signal against channel fading. This article studies the performance of protograph-based low-density parity-check (LDPC) codes with receive antenna diversity. The authors first propose a modified version of the protograph extrinsic information transfer algorithm and use it for deriving the threshold of the protograph codes in a SIMO system. The authors then calculate the decoding threshold and simulate the bit-error rate (BER) of two protograph codes (accumulate-repeat-by-3-accumulate (AR3A) code and accumulate-repeat-by-4-jagged-accumulate (AR4JA) code), a regular (3,6) LDPC code and two optimised irregular LDPC codes. The results reveal that the irregular codes achieve the best error performance in the low signal-to-noise-ratio (SNR) region and the AR3A code outperforms all other codes in the high-SNR region. Utilising the theoretical analyses and the simulated results, the authors further discuss the effect of the diversity order on the performance of the protograph codes. Accordingly, the AR3A code stands out as a good candidate for wireless communication systems with multiple receive antennas.

We investigate the performance of the protograph low-density parity-check (LDPC) codes, which have been shown to possess simple structures and outstanding error performance over additive white Gaussian noise (AWGN) channels, over partial response (PR) channels using the finite-length extrinsic information transfer (EXIT) algorithm. Due to the intersymbol interference (ISI) caused by the PR channels, we observe that the conventional protograph LDPC codes do not perform well in terms of error rates. We further propose a new design scheme and construct three new types of protograph LDPC codes. Unlike conventional protograph LDPC codes in which the highest-degree variable nodes are punctured, the new protograph LDPC codes have their lowest-degree variable nodes punctured. Moreover, some edge re-connections are made in one of the proposed codes. The EXIT-chart analysis, the convergence analysis and the bit-error-rate simulation have shown that all three new codes outperform the conventional protograph LDPC codes. Moreover, two of the proposed codes are superior to the regular column-weight-3 LDPC code and thus they are good alternatives compared to other error-correction codes for use in data storage systems.

A new decoder is proposed to decode the (23, 12, 7) binary Golay-code up to five errors. It is based on the algorithm that can correct up to four errors for the (24, 12, 8) extended Golay-code proposed by Lin et al., thereby achieving the soft decoding in the real sense for the Golay-code. For a weight-2 or weight-3 error pattern decoded by the hard decoder for correcting up to three errors, one can find the corresponding 21 weight-4 or weight-5 error patterns and choose the one with the maximum emblematic probability value, which is defined as the product of individual bit-error probabilities corresponding to the non-zero locations of the error pattern as the ultimate choice. Finally, simulation results of this decoder over additive white Gaussian noise (AWGN) channels show that the proposed method provides 0.9 dB coding gain than that of Lin et al.'s algorithm at bit-error rate of 10−5.

Designing a non-ideal delay line (DL) with phase distortion in a transmitted-reference ultra-wideband system with an autocorrelation receiver is a great technical challenge. Differing from the currently empirical design method of DL, a semi-analytic approach is proposed through Gaussian approximation of the expression for conditional bit error rate (BER), based on investigation on the degradation of average BER caused by a group delay ripple range (GDRR) over independent Nakagami-m fading channels. This GDRR-based design method can directly evaluate its effects on the system performance and determine the acceptable phase distortion level to trade-off the BER performance and system complexity.

Frequency modulated differential chaos shift keying (DCSK/FM-DCSK), a joint modulation and spread spectrum technique, is a promising modulation technique for low-cost and low-complexity wireless transmission applications. The noise performance of DCSK/FM-DCSK is superior to most conventional modulation schemes in multipath-channel environment. Cooperative communication, on the other hand, is receiving increasing attention due to its efficiency in sharing single-antenna mobiles or network nodes with other antennas to achieve combating fading via transmitting diversity. By combining these two aspects of advantages, a novel chaotic communication system is proposed in this paper, aiming to achieve combating multipath and fading effects. Simulation results show that significant performance improvement can be achieved by the proposed system in comparison with non-cooperative systems. It is found that the choice of some key parameters, such as the spread spectrum factor and the relay selective strategy, affect the system performance prominently. It reveals that the combination of the DCSK/FM-DCSK framework with a cooperative strategy is of great practical value for certain wireless communication networks.

In this study, the performance of the frequency-modulated differential chaos shift keying (FM-DCSK) ultra-wideband (UWB) system is evaluated through two important system parameters, the guard interval and the integration interval of the integrator, over indoor communication channels. It is found that the existing FM-DCSK UWB system suffers severe performance degradation in the IEEE 802.15.4a low-rate application. To resolve this problem, a new optimising scheme for the integration interval is presented. Simulation results show that the performance of the proposed scheme is significantly improved and becomes insensitive to the data rate. In addition, some notable advantages are evident in the proposed system, such as moderate multiple-access capability and feasible cross-layer optimisation.

Both exponential stability and periodic oscillatory solution of bidirectional associative memory (BAM) networks with axonal signal transmission delays are considered by constructing suitable Lyapunov functional and some analysis techniques. Some simple sufficient conditions are given ensuring the global exponential stability and the existence of periodic oscillatory solutions of BAM with delays. These conditions are presented in terms of system parameters and have important leading significance in the design and applications of globally exponentially stable and periodic oscillatory neural circuits for BAM with delays. In addition, two examples are given to illustrate the results.