Spread Spectrum Method Research Articles

An All-Digital Spread Spectrum Method with Distortion Correction for Filterless Digital Class-D Amplifiers

An All-Digital Spread Spectrum Method with Distortion Correction for Filterless Digital Class-D Amplifiers

Metode Spread Spectrum untuk Penyisipan Pesan pada Citra Digital

Abstract The importance of the value of information in a message means that the message often does not reach the recipient, but instead falls into the hands of unwanted people. Various techniques are used to prevent access by unauthorized persons. One of the various techniques to protect this information is steganography, which is the hiding of a message inside another message to avoid suspicion that someone is trying to steal information. The initial stage of the insertion process is to perform a binary spread of the message characters with a scalar magnitude of 4 to produce a new segment followed by the generation of a random number (pseudonoise random number) using the steganography key and converted into binary form. Then proceed with modulation with XOR logic operation between the value of the binary segment and the line of random numbers that have been converted into binary to produce a new binary that will be inserted into the digital image object. The spread spectrum method produces quite good image quality after the insertion process, this can be proven by the PSNR test results which are more than 30 dB.

The Effect of Spread Spectrum Modulation on Power Line Communications

Interference in Power Line Communication (PLC) is examined in this paper. PLC is a wired communication technology that provides communication and data transmission over the existing electrical network. It uses the electrical wiring in buildings or the electrical grid to transmit data signals between devices, rather than using dedicated communication cables or wireless signals. Many applications employ PLC technologies, which have the benefit of leveraging existing power connections for both power and data transfer, reducing cost and complexity. These interactions may be observed in contemporary smart grids and automobile power networks, where lengthy cables, switching power supplies and communication links all work together but exacerbate Electromagnetic Interference (EMI) problems. This research examines the effects of spread spectrum methods used to reduce EMI from power converters on PLC systems. Spread Spectrum Modulation (SSM) and its three variants, Sine, Random and Sawtooth, are frequently employed to meet the requirements of electromagnetic compatibility, however, there are some repercussions that may be detrimental to the converter or the rest of the electrical network. These outcomes occur for various modulation algorithm settings and at various frequencies. Measurements are made utilising the Frame Error Rate (FER) value provided by the PLC link system to ascertain the interference produced by a Silicon Carbide (SiC)-based DC-DC converter in order to investigate these concerns and standardise an assessment approach. To examine the effect of SSM on reducing EMI in the frequency domain, the peak index of a CISPR-16 EMI receiver is used.

A Novel Parameter Estimation Method of FHSS Signal with Low SNR

A novel parameter estimation method of frequency hopping spread spectrum (FHSS) signal is proposed. The observed signal is divided into multiple segments and forms an observed matrix, performing FFT on the observed matrix with different segment lengths to obtain the corresponding spectrum matrix. By analyzing the convergence characteristics of the spectrum matrix, the estimation of the symbol period is realized, on this basis, the symbol‐frequency distribution is obtained and its projected spectrum in Frequency‐Amplitude plane is further obtained to select the candidate frequencies. The matrix composed of multiple single frequency signals is constructed according to the candidate frequencies and multiplied with the observed matrix under the segment length of symbol period, then the number of symbols per hopping duration is estimated according to the matrix multiplication result, so as to realize the estimation of the hopping duration, and finally the real hopping frequencies and hopping sequence can be found out from the candidate frequencies. Simulation results are presented to indicate that the proposed method has good estimation performance especially under the condition of low SNR. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

High-Reliability Underwater Acoustic Communication Using an M-ary Cyclic Spread Spectrum

Multipath propagation, frequency selective fading, low-propagation velocity, and narrow bandwidth are all characteristics of underwater acoustic channels. Doppler shifts and diffusions can occur as a result of the low transmission speed of an acoustic signal, which can be caused by the movement of ocean currents or the transceiver. Furthermore, frequency selective fading and excessive noise interference can disrupt underwater acoustic communication on a continual basis. Because of its high anti-interference ability and high confidentiality, spread spectrum technology is commonly adopted in underwater acoustic communications. Although the direct sequence spread spectrum method has a low data rate, it is advantageous in a multipath propagation channel environment or an environment with a low signal-to-noise ratio (SNR). This advantage is suitable for long-distance transmission or LPD (Low Probability of Detection) communication, and the direct sequence spread spectrum method is applied. In this paper, we propose a highly reliable M-ary cyclic spread spectrum technique by superimposing the M-ary spread spectrum, an extension of the direct sequence spread spectrum technique, and cyclic shift keying. Furthermore, by estimating the Doppler frequency using M-ary spread spectrum codes and performing synchronization correction of the ensuing symbol based on the estimation results, higher performance can be attained. Simulations and experiments showed that the M-ary cyclic spread spectrum method can reduce Doppler estimation and synchronization error accumulation while maintaining a high data rate. Furthermore, the MCSS method had a lower bit error rate than the standard spread spectrum method.

Long-range underwater acoustic communication of M-eyry spread spectrum with cyclic prefix

The Spread Spectrum is an effective transmission method for complex channels in underwater acoustic (UWA) communication because of the high correlation of pseudo-random noise (PN) sequence. In particular, the spread spectrum method is effective in an environment with a low signal-to-noise ratio. The bandwidth of UWA communication channel is limited due to the fact that sound wave attenuation in water is positively associated with frequency. The limited bandwidth directly leads to the low data rate of conventional direct-sequence spread spectrum UWA communication. M-ary spread spectrum (MSS) schemes using multiple orthogonal PN sequences were proposed as a solution to this problem. However, even in the MSS method, the performance may be limited by the delay spread characteristics in the multipath propagation channels. We propose a more robust communication method in the UWA channel by including Cyclic Prefix (CP) to achieve a more robust performance in the multipath channel. In the proposed method, a CP is inserted for every symbol. In the 160 km long-range UWA communication experiment conducted in the East Sea, the proposed method showed more reliable results than the conventional MSS method. [Work supported by the Agency for Defense Development, South Korea, Grant No. UD200010DD.]

Non-coherent turbo coded frequency shift keying for reliable covert underwater acoustic communications

This paper presented efficient receiver structure of non-coherent turbo coded FSK signals for maintaining covertness and performance in underwater communication. In aspect to covertness, direct sequence spread spectrum method, which used to hide the transmitted signal by transmitting it at low power and, thus, making it difficult for an unintended listener to detect the signal in the presence of background noise. In aspect to performance improvement in the underwater acoustic environment with multipath and Doppler spreading, non-coherent FSK which is not required phase information, weighted multiband technology, and turbo equalization model with rate of 1/3 were suggested. In order to analyze the performance by applying four bands and spreading chips with 8 and 32, the experiment was conducted on a lake by moving in the range of 300m to 500m. Through the experimental results, we confirmed the performance was improved as increasing number of bands, turbo iterations, and spreading chips. Furthermore, weighted multiband technology which allocates lower weight to inferior bands based on preamble error rates were applied for some failed packets, all packets were decoded successfully. [This research was funded by Agency for Defense Development, South Korea, Grant No. UD200010DD.]

Normalized Matched Filter for Blind Interference Suppression in Filter Bank Multicarrier Spread Spectrum Systems

This paper proposes and analyzes a modification to the standard matched filtering operation utilized in filter-bank multicarrier spread spectrum (FB-MC-SS) communications. This modification suppresses the impact of partial-band interferers without <i>a priori</i> knowledge of their location within the band of transmission and/or their power characteristics. A performance analysis of the proposed matched filter, which indicates its usefulness in environments where interference is likely to be experienced, is presented. It is shown that whereas the standard matched filter proves to be ineffective for packet detection and timing acquisition in such harsh environments, the modified matched filter successfully removes the harmful effects of interferers. This is found to be a unique feature of FB-MC-SS which is non-existent in other alternative spread spectrum methods.

Optimized Masking for MIMO Radar Signals

Electronic attack devices can interrupt a radar system by emitting jamming signals. This function typically depends on the support from electronic support measure (ESM) devices, which can capture and identify radar signals in the air. A radar system can avoid being interrupted by confusing adversarial ESM devices. In this article, at the background of colocated multiple-input multiple-output radar, we present an active antijamming method that aims at confusing adversarial ESM devices by masking radar signals with accompanying signals. Masking signals can be transmitted in either the pulsed mode or the periodic continuous-waveform mode. They can be either constant-modulus or with amplitude modulation. The masking signal will cover the radar signal in both time and frequency domains, in order to make adversarial ESM devices find it hard to determine whether an intercepted signal source is a spoofing device or an operating radar. We suppress the impact of masking signals on radar-matched filters, measured by the integrated sidelobe level and peak sidelobe level of their cross-correlation sidelobes, through optimization of masking signals. Masking signals whose chip duration is shorter than that of radar signals are considered for a lower cross-correlation sidelobe level. It is termed as the sequence spread spectrum method, and this method is found critical to obtain good cross-correlation sidelobes, as indicated in numerical results with several kinds of well-designed radar signals. In concerned simulation scenarios, a good masking signal tends to focus its power on frequency bands, where the radar signal power is low.

Study of the Performance of DSSS UAC System Depending on the System Bandwidth and the Spreading Sequence.

A signal transmitted in an Underwater Acoustic Communication (UAC) system operating in a shallow-water channel suffers from strong time dispersion due to multipath propagation. This causes the Inter-Symbol Interference (ISI) observed in the received signal, which significantly limits the communication system’s reliability and transmission rate. In such propagation conditions, the Direct-Sequence Spread Spectrum (DSSS) method is one of the solutions that make reliable data transmission possible. In systems with one-to-one communication, it ensures communication with a satisfactory Bit Error Rate (BER). Additionally, it makes it possible to implement the Code-Division Multiple Access (CDMA) protocol in underwater acoustic networks. This paper presents the results of simulation and experimental communication tests on a DSSS-based UAC system using three types of spreading sequence, namely m-sequences, Kasami codes and Gold codes, and occupying different bandwidths from 1 kHz to 8 kHz around a carrier frequency equal to 30 kHz. The UAC channel was simulated by impulse responses calculated by the virtual sources method and the UAC chanel models available in the Watermark simulator. The experimental tests were conducted in a model pool. Based on the obtained results, a transmission rate was estimated, which is possible to achieve in strong multipath propagation conditions, assuming reliability expressed as BER less than 0.001.

Multi-User Secure Receiving Algorithm Based on Blind Recovery in MIMO Network

In order to optimize the performance of data transmission in multiple input multiple output (MIMO) wireless communication systems, a spread spectrum self-interference system based on channel inverse matrix modulation is proposed. First of all, we improved the spread spectrum method and proposed the DIMMSS(channel inverse matrix modulation spread spectrum) spread spectrum method based on the channel inverse matrix. And a simulation comparison experiment was carried out for the anti-interference ability and anti-eavesdropping ability of this method. Secondly, this paper also proposes two blind despreading methods based on Walsh-hadamard algorithm and cluzeau algorithm. We studied the anti-jamming performance of these two algorithms, and optimized the blind despreading process according to their different characteristics of computational complexity. Experimental results show that compared with ordinary direct sequence spread spectrum, the spread spectrum self-interference system can not only improve the confidentiality and security of the transmitted signal, but also greatly simplify the receiving equipment. It has certain application value in the military and civilian fields.

СКРЫТИЕ ИНФОРМАЦИИ В АУДИОСИГНАЛАХ С ИСПОЛЬЗОВАНИЕМ ДЕТЕРМИНИРОВАННОГО ХАОСА

At present, the discovery of deterministic chaos is one of the significant subjects of research in various fields of science. In this work, deterministic chaos considered as a sequence with specific properties, which is used to transmit information in a stegosystem. The efficiency of the algorithm for steganographic embedding and extraction of digital information into audio containers by the method of spreading the spectrum using chaotic signals is analyzed. The spread spectrum method is characterized by the presence of a large number of errors on the receiving side when used in the classical version, without the original audio, i.e. there was no possibility of blind extraction. Errors arising when transmitting an audio signal over a communication channel made it impossible to extract the embedded information correctly. It proposed to use an algorithm that increases the efficiency of information signal extraction on the receiving side. The efficiency of the method is estimated by the amount of distortion in the original audio and by the reliability of extracted information, which is characterized by the value of the error probability. It showed that to extract embedded data with high reliability from stegoaudio, one should use an adaptive filtering algorithm - thresholding using discrete wavelet transform (DWT). The best filtering method, using various orthogonal mother wavelets (Haar, Daubechies, and Symlet) at different levels of signal decomposition, was determined. In the course of this study, recommendations were made on the use of mother wavelets, and was given preference to Daubechies and Symlet wavelets. Requirements for the numerical values of the embedding parameters and the parameters of the generators of chaotic processes used to expand the spectrum formulated.

Метод формирующего оператора для моделирования циклостационарных случайных процессов

The paper proposes the shaping operator technique for modelling cyclostationary random process (CSRP) which belong to the class of second-order processes being described by the parametric pulse train model. Generating CSRP is expressed as the propagation result of the specially chosen elementary CSRP through the linear time-invariant system with a known impulse response. The paper describes the approach to forming the elementary CSRP based on the train made of Dirac delta-function uniformly following in time domain with constant step and defining the desired structural periodicity of the process being modelled. The analytical expressions for the main characteristics used for describing cyclostationary properties of the elementary process, including two-dimensional, cyclic and spectral corelation functions, were obtained. In addition to the case of the elementary CSRP with correlated weighting coefficients of delta-functions, the case of statistically independent coefficients was considered. It was shown that utilization of the spectral correlation function (SCF) for describing the cyclic property reveals the explicit analytical relation between characteristics of the elementary and modelled CSRPs provided the filter frequency response is known. The paper presents the comparative example which describes the modelling of two CSRPs: one of them was chosen as the train of rectangle pulses which is pulse amplitude modulated by stationary random time series, while the other is considered as a signal formed by the method of direct sequence spread spectrum. The chosen short-length Barker sequence as the code allowed performing visual comparison between absolute value of SCF components taken at the cyclic frequencies multiple of the chip frequency and cyclic frequencies multiple of the symbol frequency. The future development of the methods proposed in the paper opens the road to improving the performance of modern radar and telecommunication systems by means of utilizing cyclic frequencies which are non-random parameters describing the structural properties of signals under processing.

Decoding and measurement of frequency‐hopping spread spectrum signals using an adaptive algorithm‐based compressive sensing

SummaryDecoding of frequency‐hopping spread spectrum (FHSS) methods to intercept the symbol content in signals and brilliant measurement is presented in this paper. The switching of the frequency channels rapidly using a pseudorandom code makes interception of FHSS signals very difficult. Therefore, a proposed adaptive compressive measurement for decoding the frequency‐hopping receivers that have no prior knowledge of the hopping sequence is the main focus of this work. The proposed methods rely on the instantaneous sparsity of the spectra of FHSS signals, and the transmitted symbols can be recovered from the proposed compressive measurements. Furthermore, the contribution of this work is the design of a proposed adaptive method that is used to design measurement kernels for compressive measurement and decoding based on knowledge enhancement, which includes both prior information enhanced and adaptive methods based on the properties of the intersignals. Simulation results on Gaussian frequency‐shift keying (GFSK) FHSS signals illustrate that the proposed compressive method enhances the detection performance of the received frequencies with acceptable decoding accuracy compared with other techniques such as enhanced orthogonal matching pursuit (EOMP) and an adaptive sampling kernels method with a random compressive ratio. Also, an enhancement of the proposed algorithm is achieved due to enhancement in both the normalized mean square error (NMSE) and the probability of correction error (Pce). The comparison between these algorithms is performed using simulation based on MATLAB and receiver operating characteristic (ROC) curves.

Three-frequency pseudo-random varying spread spectrum method for filterless digital class-D audio amplifiers

This paper presents a novel spread spectrum (SS) method with a pseudo-natural sampling technique for filterless digital class-D audio amplifiers. This method is proposed to reduce the electromagnetic interference (EMI) emissions of amplifiers by lowering the output out-of-band spectral amplitudes around the pulse width modulator carrier frequency and its multiples. The main idea of this method is that the sampling frequency of the modulating signal and the carrier frequency are varied synchronously and randomly among three different values. Since the carrier frequency is variable, the polynomial interpolation Newton–Raphson (PI-NR) algorithm is modified to correct the harmonic distortion caused by uniform-sampling pulse width modulation (UPWM). Based on a field programmable gate array (FPGA), an experimental system is established to analyze the performances of the proposed method and other six reported SS methods. Experimental results show that the proposed method features the lowest total harmonic distortion (THD) of 0.009% with a 6.6 kHz, 0 dBFS (full scale) input, a relatively high signal-to-noise ratio (SNR) of 52.68 dB and a relatively high output out-of-band peak spectral amplitude reduction of 17.75 dB.

A Family of Spread-Spectrum Modulation Schemes Based on Distribution Characteristics to Reduce Conducted EMI for Power Electronics Converters

Spread-spectrum modulation strategy is recognized as an effective solution to reduce conducted electromagnetic interference (EMI). This article proposes a family of spread-spectrum modulation strategies that can effectively reduce the conducted EMI for power electronics converters. The introduced modulation strategies eliminate the noise spikes in conducted EMI spectrum, reducing the harsh requirements for designing EMI filters. The proposed spread-spectrum methods are based on the distribution characteristic of switching frequency, which determine the waveform function of switching frequency. In addition, the design principles take reduced switching losses and fixed variation range of switching frequency into consideration. The differential equation that makes the switching frequency subject to arbitrary statistical distribution is derived in detail together with the corresponding solutions. Three typical statistical distributions represented by uniform distribution, exponential distribution and normal distribution are performed. Relevant experiments have verified that the proposed spread-spectrum modulation schemes can reduce the conducted EMI about 20 dB. Finally, several other typical spread-spectrum modulation schemes such as random pulsewidth modulation (PWM), periodic PWM, and programmed PWM are implemented in converters for comprehensive comparison to evaluate the proposed spread-spectrum modulation schemes.

IMPLEMENTASI ALGORITMA SPRITZ DAN SPREAD SPECTRUM UNTUK MENYEMBUYIKAN PESAN ENKRIPSI KEDALAM FILE AUDIO MP3

Optimizing the security of confidential text messages is very important to protect the contents of messages from those who want to use or damage the message. The use of cryptographic techniques in securing data can still raise suspicion of the message that has been secured. This study explores how to use steganography techniques to coat encrypted message security based on steganography techniques. The spritz algorithm is a cryptographic algorithm that is used to obtain the cipher from the original message, while the spread spectrum method is a method used to hide the original data password into an image. Based on testing done by combining these two techniques, it is quite reliable to optimize the security of secret messages because others cannot see the existence of the cipher of the original data in plain sight.Keywords: Cryptography, Steganography, Spritz, Spread Spectrum, mp3

A Comparison of Steganography in the GIF Image using LSB and Spread Spectrum Method

A Comparison of Steganography in the GIF Image using LSB and Spread Spectrum Method

Analysis of Steganography on TIFF Image using Spread Spectrum and Adaptive Method

Analysis of Steganography on TIFF Image using Spread Spectrum and Adaptive Method

A Survey on Spread Spectrum Methods for Image Watermarking in Noisy Environment

A Survey on Spread Spectrum Methods for Image Watermarking in Noisy Environment