Direct Sequence Spread Spectrum Research Articles

Serial Multicode Direct Sequence Spread Spectrum With Applications to Satellite Navigation Pilot Channels

Serial Multicode Direct Sequence Spread Spectrum With Applications to Satellite Navigation Pilot Channels

Research on a High-Dynamics Acquisition Algorithm for New Binary Offset Carrier Signal in UAV Communication

As unmanned aerial vehicles (UAVs) are widely used in various fields, there is an increasing demand for UAV anti-jamming, multipath mitigation, and covert secrecy. Frequency-hopping binary offset carrier (FH-BOC) signals possess higher anti-jamming and multipath mitigation capabilities than direct-sequence spread spectrum (DSSS) and binary offset carrier (BOC) signals. A prerequisite for constructing communication links between UAVs using FH-BOC signals is the design of efficient acquisition algorithms to capture the signals successfully. In this paper, the modulation and characteristics of the FH-BOC signal are introduced. The maximum relative velocity between UAVs is 5.5 km/s, the maximum acceleration is 50 g, and the maximum plus acceleration is 20 g/s. In this high dynamic environment, the parameters for the parallel code phase and Partial Matched Filter–Fast Fourier Transform (PMF-FFT) acquisition algorithms targeting FH-BOC(10,1) signals are designed, and the acquisition performance of these algorithms is comparatively analyzed. The acquisition time for the first and second algorithms is 4.3317 s and 6.137 s. The number of real additions required by the first and second algorithms is approximately 10.9×109 and 8.9×109, and the number of real multiplications is approximately 7.6×109 and 6.7×109. This helps in selecting the acquisition algorithm when FH-BOC signals are used to build inter-UAV communication links.

Anti-jamming for cognitive radio networks with Stackelberg game-assisted DSSS approach

The proposed study introduces a novel anti-jamming approach for cognitive radio networks (CRNs) by integrating the Stackelberg game model with direct sequence spread spectrum (DSSS) techniques. This innovative combination enhances the security and performance of CRNs by optimizing resource allocation and fortifying network resilience against jamming attacks. The Stackelberg game model provides a strategic framework where the Defender and Adversary dynamically adjust their strategies to achieve Nash equilibrium, ensuring strategic stability. The application of DSSS further improves signal robustness, mitigating interference from jamming attempts. Simulation results demonstrate significant improvements in network security, resource utilization, and overall performance, validating the efficacy and advantages of the proposed scheme in maintaining reliable communication in the presence of adversarial threats.

Is Direct Sequence Spread Spectrum Modulation Promising for AI-Based Design of 6G Networks?

Is Direct Sequence Spread Spectrum Modulation Promising for AI-Based Design of 6G Networks?

Data Communication Over Power-lines: A Review on Technical, and Applications Challenges

This paper presents a review study on the data communication over power-lines, commonly referred to as power-line carrier, power-line communication (PLC), mains communications, or power-line digital subscriber line (PDSL). This study examines the technical and application advantages and challenges associated with adopting PLC as a preferred alternative technology for wideband or broadband data communication. The broader coverage area of the PLC network gives it a distinct advantage over other communication network technologies. Additionally, implementing a communication system using the existing power-line network is more cost-effective and less time-consuming compared to constructing a new network from scratch. However, the primary challenge lies in the fact that the power-line network is primarily designed for the distribution of electrical power within the frequency range of 50-60 Hz including the harmonics. This poses various obstacles such as electrical noise from appliances, signal distortions caused by the unregulated nature of the wiring, transformer bypassing, interference from high-frequency modulation, and variations in characteristic impedances, among others. Despite these challenges, the emergence of robust modulation techniques like Orthogonal Frequency Division Multiplexing (OFDM) and Direct-Sequence Spread Spectrum (DSSS), along with the development of Application-Specific Integrated Circuit (ASIC) density with improved processing speeds, as well as advancements in signal processing and error control coding techniques, have made the PLC network the most promising telecommunications access network.

Methods of countering attacks and organizing the choice of channel protection tools when controlling aviation robotic devices

The purpose of the research is identification of organizational and technical methods of countering attacks on command and telemetry data transmission lines between aviation robotic devices and ground control points, as well as the formation of comprehensive information protection of the communication channels under consideration.Methods. The scientific article substantiates methods for mitigating and countering attacks at the physical level of the ISO/OSI open systems interaction model for organizing communication using the MAVLINK protocol for the purpose of controlling aviation robotic devices (noise-resistant coding with a high code rate (using the example of the most common code - Viterbi), extension method Frequency Hopping Spectrum (FHSS), Direct Sequence Spread Spectrum (DSSS), Multiple Input Multiple Output (MIMO) technology). A method for organizing the selection of protection and countermeasures when controlling aviation robotic devices is outlined, which consists of assessing the risks and consequences of the implementation of vulnerabilities in order to introduce countermeasures there and in such quantities that they have the greatest benefit.Results. The article discusses the main possibilities for intentional interference on the control and data transmission channels of consumer aviation robotic devices, an algorithm for assessing the risk of "leaving the route" is considered; a risk assessment option is provided in relation to the risk of an aircraft going off route, indicating the name of the attack, its likelihood, impact and resulting risk, as well as the acceptability of this risk and recommendations regarding the urgency of mitigating it; recommendations for countermeasures are presented in accordance with the acceptability of likelihood and impact; describes the relationship between risk and countermeasures used to reduce unauthorized exposure, in accordance with weighting coefficients.Conclusion. The scientific article discusses the main methods of countering attacks and unauthorized access when controlling autonomous robotic devices. The risk coefficients of attacks and countermeasures taken are considered.

Chaotic Phase Modulation Direct-Sequence Spread Spectrum-Assisted Adaptive Serial Cancellation List Decoding Method for Underwater Acoustic Communication

Addressing the challenges of high decoding latency, reduced spectral efficiency, and substantial storage requirements in a Cyclic Redundancy Check (CRC)Aided Successive Cancellation List (CA-SCL) polar decoder, this paper proposes a chaotic phase modulation direct-sequence spread spectrum (CPMDSSS)-assisted adaptive serial cancellation list decoding method for underwater acoustic communication. The method involves segmenting the information bits to be transmitted, computing CRC for each segment, and mapping all CRCs to a CPMDSSS, which is then modulated onto the pilot subcarriers of underwater acoustic orthogonal frequency-division multiplexing (OFDM) to increase spectral efficiency. At the receiving end, CRCs are obtained by demodulating the CPMDSSS to verify the segmented information and adaptively select the number of decoding paths. The theoretical analysis and simulation results demonstrate that compared to CA-SCL, the proposed method effectively reduces the required storage units and improves spectral efficiency, with an average reduction of approximately 80% in the decoding paths. Sea trials further indicate that the proposed method reduces the average decoding paths by approximately 71% and decreases the average decoding delay by approximately 64% compared to CA-SCL.

Structure of Spread Spectrum Telemetry Radio Link for LEO Small Satellite

The paper considers the design of telemetry radio link for low Earth orbit (LEO) satellites, particularly based on CubeSat format. A significant limitation of such spacecrafts are the available dimensions for antennas and the transmitting power, which leads to low energy level at the ground receiving point of transmitted signal. The article presents the physical level structure for data frame based on direct sequence spread spectrum technique, which allows for additional signal gain to achieve the required level of link performance. Using such principle also make possible to implement adaptive data rate control depending on dynamics in signal-to-noise ratio when the distance from the satellite to the ground point changes. For proposed data frame structure, an analysis of received information size during a communication session was carried out, which is parameterized on the maximum observable elevation angle of the satellite. The issue of datalink layer interaction between devices is also considered.

Chaotic Spread-Spectrum Communication: A Comparative Study between Chaotic Synchronization and Matched Filtering

This publication investigates the performance of demodulation methods utilized in spread spectrum chaotic communication systems in order to understand conditions at which advanced demodulation methods, such as chaotic synchronization, provide tangible benefits over classical, matched filtering-based approaches. We conduct simulations and comparisons of three different communication systems: classic direct sequence spread spectrum (DSSS), chaotic signal fragment-based pseudo-chaotic spread spectrum (PCSS), and chaotic synchronization-based antipodal chaos shift keying (ACSK). These systems possess similar spectral and time domain characteristics, allowing us to shed light on their fundamental differences and limitations in chaos-based communication. Additionally, we assess the impact of frequency modulation (FM) on these modulation methods, as FM allows the creation of simplified non-coherent modulation schemes. Our findings, based on the analysis of bit error ratio (BER) curves, demonstrate that in the case of a non-dispersive communication channel, the utilization of chaotic synchronization does not allow to achieve performance of correlation-based receivers. Additionally, the utilization of chaotic synchronization for multiple access poses certain challenges due to malicious synchronization between users. As a supplementary finding, we show that in systems with matched filter-based demodulation, discrete-time quantized spreading sequences confer an advantage over analogous, continuous-time spreading waveforms.

Direct sequence spread spectrum (DSSS) signal detection based on eigenvalues local binary pattern residual network (EL-ResNet)

Direct sequence spread spectrum (DSSS) signal detection based on eigenvalues local binary pattern residual network (EL-ResNet)

Performance of the Direct Sequence Spread Spectrum Underwater Acoustic Communication System with Differential Detection in Strong Multipath Propagation Conditions

The underwater acoustic communication (UAC) operating in very shallow-water should ensure reliable transmission in conditions of strong multipath propagation, significantly disturbing the received signal. One of the techniques to achieve this goal is the direct sequence spread spectrum (DSSS) technique, which consists in binary phase shift keying (BPSK) according to a pseudo-random spreading sequence. This paper describes the DSSS data transmission tests in the simulation and experimental environment, using different types of pseudo-noise sequences: m-sequences and Kasami codes of the order 6 and 8. The transmitted signals are of different bandwidth and the detection at the receiver side was performed using two detection methods: non-differential and differential. The performed experiments allowed to draw important conclusions for the designing of a physical layer of the shallow-water UAC system. Both, m-sequences and Kasami codes allow to achieve a similar bit error rate, which at best was less than 10 −3. At the same time, the 6th order sequences are not long enough to achieve an acceptable BER under strong multipath conditions. In the case of transmission of wideband signals the differential detection algorithm allows to achieve a significantly better BER (less than 10 −2) than nondifferential one (BER not less than 10 −1). In the case of narrowband signals the simulation tests have shown that the non-differential algorithm gives a better BER, but experimental tests under conditions of strong multipath propagation did not confirm it. The differential algorithm allowed to achieve a BER less than 10 −2 in experimental tests, while the second algorithm allowed to obtain, at best, a BER less than 10 −1. In addition, two indicators have been proposed for a rough assessment which of the detection algorithms under current propagation conditions in the channel will allow to obtain a better BER.

Implementation of Underwater Electric Field Communication Based on Direct Sequence Spread Spectrum (DSSS) and Binary Phase Shift Keying (BPSK) Modulation.

Stable communication technologies in complex waters are a prerequisite for underwater operations. Underwater acoustic communication is susceptible to multipath interference, while underwater optical communication is susceptible to environmental impact. The underwater electric field communication established based on the weak electric fish perception mechanism is not susceptible to environmental interference, and the communication is stable. It is a new type of underwater communication technology. To address issues like short communication distances and high bit error rates in existing underwater electric field communication systems, this study focuses on underwater electric field communication systems based on direct sequence spread spectrum (DSSS) and binary phase shift keying (BPSK) modulation techniques. To verify the feasibility of the established spread spectrum electric field communication system, static communication experiments were carried out in a swimming pool using the DSSS-based system. The experimental results show that in fresh water with a conductivity of 739 μS/cm, the system can achieve underwater current electric field communication within a 11.2 m range with 10-6 bit errors. This paper validates the feasibility of DSSS BPSK in short-range underwater communication, and compact communication devices are expected to be deployed on underwater robots for underwater operations.

Cyclostationarity of Communication Signals in Underwater Acoustic Channels

The effect of underwater acoustic propagation on the cyclostationary features of communication signals is modeled and analyzed. Two kinds of channels are considered: the multiscale-multilag channel, over which mobile and wideband acoustic systems usually communicate, and the dispersive channel resulting from low-frequency modal propagation in shallow water. It is shown that multiscale-multilag channels transform cyclostationary signals into a sum of velocity and acceleration-dependent time-warped cyclostationary processes. This time-warping is carefully taken into account to efficiently recover the cyclostationary features. On the other hand, it is found that low-frequency dispersive channels preserve the original periodicity but attenuate the shorter cycles and spread the correlations. To illustrate the theoretical results, applications with simulated and real data are also presented. Specifically, the problem of estimating time-varying Doppler scales is addressed for multiscale-multilag channels as well as the detection of signals with unique cyclostationary signatures. The example of blind symbol-rate estimation applied to covert communications in dispersive channels is also discussed. Special attention is paid to phase-shift keying (PSK), quadrature amplitude modulation (QAM), orthogonal frequency-division multiplexing (OFDM), and direct-sequence spread-spectrum (DSSS) signals. Accompanying supplementary material provides the MATLAB code used for the estimation and detection examples.

CBTC Security and Reliability Enhancements by a Key-Based Direct Sequence Spread Spectrum Technique

CBTC Security and Reliability Enhancements by a Key-Based Direct Sequence Spread Spectrum Technique

Integrating key generation and distribution with the quantum noise stream cipher system without compromising the transmission performance

We propose and experimentally demonstrate a secure quantum noise stream cipher transmission system that integrates key generation and distribution. At the stage of carrier phase recovery, the estimated phase noise is used to generate randomness keys without additional equipment. Based on direct sequence spread spectrum technology, we integrate the distributed keys with quantum noise stream cipher signals. The key distribution and encryption transmission can be completed simultaneously without occupying additional bandwidth or time slots. By changing the position of distributed keys in the encryption base, the BER performance of QAM/QNSC signals cannot be affected by the keys. Experimental results demonstrate that the 54.5 Mbps key distribution and 31 Gbps encryption transmission without OSNR penalty can be achieved simultaneously over a 120 km standard single-mode fiber.

The line-of-sight peak detection and tracking of underwater acoustic DSSS communications in the doubly spread channel

In the underwater acoustic (UWA) channel, the line-of-sight (LOS) path has the characteristics of stable magnitude and continuous phase, which is seldom affected by the surface/bottom reflection. Therefore, in the direct sequence spread spectrum (DSSS) communication systems, the receiver usually extracts the LOS path to recover the information bits and achieve the robust communication. However, the UWA channel is typically the doubly spread channel, i.e., multipath fast fading and non-uniform Doppler shifts, which seriously degrades the performance of extracting the LOS path by the conventional maximum energy method. Therefore, this paper proposes a LOS peak detection and tracking algorithm to extract the LOS path in the UWA DSSS communications. In the proposed algorithm, the candidate correlation peaks after de-spreading are firstly selected by the adaptive peak detection threshold. Then, according to the transmitter/receiver motion relationship, the Delay-Doppler joint state equation is established, and thus the nearest neighbor method adopting the Kalman filter is proposed to track the LOS path. Numerical simulation results demonstrate that the proposed algorithm has better processing performance in the doubly spread channels compared with the conventional method. Finally, the performance of the proposed algorithm is confirmed by the shallow water horizontal channel and deep sea vertical channel experiments.

Reducing Bit Error Rate in WiMAX using Spread Spectrum Techniques in Comparison with OFDM based Modulations

This research investigated the Bit Error Rate (BER) performance of the WiMAX(Worldwide Interoperability for Microwave Access), a wireless system which uses IEEE 802.16 standard. For the implementation of OFDM model and analyzing the performance of WiMAX system using the Bit Error Rate (BER) and Signal to Noise Ratio (SNR) MATLAB software tool is used. We have used different adaptive modulation techniques such as QPSK, 16-QAM and 64-QAM and spread spectrum techniques such as FHSS (Frequency Hopping Spread Spectrum) and DSSS (Direct Sequence Spread Spectrum). In the current research the Bit Error Rate is improved by using spreading signals. Spread spectrum enables a signal to be transmitted across a frequency band that is much wider than the minimum bandwidth required by the information signal. The simulation results of this research show that FHSS and DSSS have given low BER at low SNR as compared to other modulation techniques.

Complementary Coded Identical Code Cyclic Shift Multiple Access Under Asynchronous Frequency-Selective Fading Channels

A complementary coded code-division multiple-access (CC-CDMA) system is built on the direct sequence (DS) spread spectrum technique, which can suppress multipath interferences and multiple-access interferences due to the ideal correlation property of complementary codes (CCs). However, the DS spread spectrum technique will cause poor bandwidth efficiency; the CC-CDMA system suffers from serious interferences due to the ideal correlation of CCs may not be reconstructed at the receiver after passing through asynchronous frequency selective fading channels. In this paper, we propose a complementary coded identical code cyclic shift multiple access (CC-ICCSMA) system under asynchronous frequency selective fading channels, which allows multiple data streams to transmit in parallel by sharing one spreading code for improving the bandwidth efficiency. Considering the impact of interferences, we propose an ICCS matched filterbank to tackle the interferences, which can decode the data under all paths and achieve a high multipath diversity gain. Simulation results show that the proposed CC-ICCSMA system can achieve higher bandwidth efficiency than that of traditional CC-CDMA and can outperform the traditional DS-CDMA schemes in terms of bit-error rates and transmission rates.

Short-Block-Length Low-Density Parity-Check Codes-Based Underwater Acoustic Spread-Spectrum Communication System

Low-density parity-check (LDPC) codes are commonly used in communication systems to improve the system performance, but LDPC codes takes too long for decoding, making communication inefficient and unsuitable for short-frame data transmission methods. In underwater acoustic channels, spread-spectrum communication becomes an effective way to realize long-distance communication. This paper combines short-block LDPC codes with a direct sequence spread spectrum and soft spread spectrum in underwater acoustic communication, addressing the problem of the inapplicability of conventional LDPC codes. The applicability of the proposed method in this paper is verified through simulation tests and pool experiments. The results indicate that the proposed communication system achieves lower bit error rates compared to the classical coding methods used in underwater acoustic spread-spectrum communication systems under the same channel conditions.

Analytical Technique Leveraging Processing Gain for Evaluating the Anti-Jamming Potential of Underwater Acoustic Direct Sequence Spread Spectrum Communication Systems

This study proposes an analytical technique underpinned by processing gain to evaluate the anti-jamming potential of an underwater acoustic direct-sequence spread-spectrum (DSSS) communication system that employs a short-period pseudo-noise (PN) sequence. The processing gain comes from the symmetry of the coding, which provides a mechanism for separating desired signals from unwanted ones, and the apparent randomness of the coding, which suppresses interference and noise in the system. The robustness of such a system against wideband interference, partial-band jamming, and single-frequency interference is emulated. Outcomes suggest that, in comparison to a standard binary phase shift keying (BPSK) system, the DSSS system’s ability to resist wideband interference is limited, with only a marginal increase in immunity performance of approximately 0.5 dB. Contrarily, it suppresses partial-band jamming effectively, with the suppression level dependent on the interference bandwidth and its relative position concerning the signal carrier frequency. The influence of single-frequency interference on system performance depends similarly on its relative location relative to the signal carrier frequency. In all situations where the interference frequency offset is an integer multiple of the bit bandwidth, the system exhibits the worst performance when the frequency offset equals the bit bandwidth. Upon comparing resistance levels to identical power interferences targeted at the signal carrier frequency, our system demonstrates optimal resilience to single-frequency interference. In concordance with the empirical findings, the simulated results substantiate both the effectiveness and practicability of the proposed analytical method based on processing gain. Subsequently, this study contributes a novel perspective for evaluating the anti-jamming potential of DSSS systems.