Direct Sequence Spread Spectrum Modulation Research Articles

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.

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?

A Method for Underwater Wireless Data Transmission in a Hydroacoustic Channel under NLOS Conditions

Wireless data transmission in the hydroacoustic channel under non-line-of-sight (NLOS) propagation conditions, for example, during a wreck penetration, is difficult to implement reliably. This is mostly due to the multipath propagation, which causes a reduction in the quality of data reception. Therefore, in this work an attempt has been made to develop a reliable method of wireless underwater communication test it under the NLOS conditions. In our method, we used multiple frequency-shift keying (MFSK) modulation, sending a single bit on two carriers, and diversity combining. The method was tested in laboratory conditions which simulated underwater signal propagation during the penetration of the wreck. The propagation conditions were investigated by determining the impulse responses at selected measurement points using the correlation method. Additionally, for comparison, the data transmission quality was determined by the bit error rate (BER) under the same conditions using direct sequence spread spectrum (DSSS) and binary phase shift keying (BPSK) modulation. The obtained results confirmed the usefulness of the application of the developed method for wireless data transmission in a hydroacoustic channel under NLOS conditions.

Suppression of EMI Using Cost-Effective FPGA-Based Digital Communication Modulation Techniques in Power Converters

ABSTRACT Direct-sequence spread-spectrum (DSSS) and frequency-hopping spread-spectrum (FHSS) modulation techniques have been proposed for the operation of three-phase voltage-source rectifiers (VSR) for the mitigation of EMI in AC Grid. For the first time, in the DSSS modulation technique, binary phase shift keying and quadrature phase shift keying (QPSK) techniques have been adopted for the mitigation of electro-magnetic interference (EMI) in three-phase VSR. A cost-effective field programmable gate array (FPGA) has been employed for carrying out these proposed modulation techniques. A VHDL coding for each modulation technique is written in ISE Xilinx, verified by Model-Sim tool and then implemented using FPGA to produce gate pulses for the rectifier. Rather than building a modulator physically, the control logic is implemented using low-cost FPGA, resulting in the cost and size reduction of the control circuit. The modulation techniques recommended in this paper are compared with the traditional sinusoidal pulse width modulation (SPWM). It is shown that the FHSS and QPSK techniques proposed in this paper result in improved power quality and the conducted EMI levels are reduced by 22.1 and 12.4 dBµV, respectively, when compared with SPWM.

An Adaptive Multi-Mode Underwater Acoustic Communication System Using OSDM and Direct Sequence Spread Spectrum Modulation

Dynamic underwater acoustic network is a research hotspot. Due to the complexity and time-varying of underwater acoustic channel, the performance of single-mode underwater acoustic communication system is often limited by the worst channel situation. Orthogonal signal division multiplexing (OSDM) is a new signal modulation technology, which can be regarded as a bridge between single carrier modulation and orthogonal frequency division multiplexing (OFDM) modulation. In order to improve the channel adaptive ability of underwater acoustic communication system and obtain a unified architecture of different carrier modulation, an adaptive multi-mode underwater acoustic communication system based on OSDM and direct sequence spread spectrum modulation (AMMUAC/OS) is proposed in this paper. Combined with spread spectrum modulation, the system can realize single carrier time domain spread spectrum (SC-TDSS), single carrier system with cyclic prefix (SC-CP), OSDM, multicarrier frequency domain spread spectrum (MC-FDSS), and OFDM communication system by adjusting the vector length M of OSDM. The addition of a variety of digital mapping methods enables the system to achieve multi-mode communication with a unified architecture. Based on the relationship between the OSDM vector length M and the underwater acoustic channel delay, a joint adaptive decision criterion based on the maximum channel delay and the channel signal-to-noise ratio (SNR) is proposed. Firstly, the OSDM vector length M is determined according to the maximum channel delay, and then the system communication mode is selected according to the channel SNR. Orthogonal matching pursuit (OMP) channel estimation algorithm is used to obtain channel information and minimum mean square error (MMSE) channel equalization algorithm is used for channel compensation. An adaptive multi-mode data frame structure is designed for the interaction between the sender and the receiver. The simulation results show that the proposed AMMUAC/OS can adapt to underwater acoustic channels with different channel delay and SNR.

Sensitivity analysis of a PLC-based DSSS anti-islanding system in power distribution grids

As smart grid applications, distributed generation, and microgrid technologies have become more widespread, new safety-related issues have arisen. Unintentional islanding is an example of a grid fault that may result in damage to electrical equipment and severe personal injuries. In this paper, an anti-islanding system employing power line communication (PLC) and direct-sequence spread spectrum (DSSS) modulation implemented with software-defined radios for continuous signaling is tested in a laboratory test setup. A concept of a fault detection algorithm is evaluated. A DSSS sensitivity analysis is carried out to investigate system’s performance against variation of a signal-to-noise ratio, and define optimal DSSS settings. The results of the analysis are interpreted, and conclusions are drawn. A transformer bypassing scheme allowing to increase the fault detection speed and throughput is introduced and tested, and the conditions of applicability are described. As a result of the study, recommendations for the system development are presented.

Ultrasonic Communication Using Consumer Hardware

We have implemented a near-ultrasonic communication protocol in the 18.5–20 kHz band, which is inaudible to most humans, using commodity smartphone speakers and microphones to transmit and receive signals. The protocol described in this paper is a component of Google's Nearby platform, where near-ultrasound signals are used to establish copresence between nearby devices by transmitting a short token. High-frequency sound does not pass through walls (most energy is reflected), so identified devices are constrained to approximately the same room, “within earshot” of one another. Our protocol has a raw data rate of 94.5 b/s, and we find in real indoor environments that transmission between mobile devices is reliable at 2 m distance and often works at 10 m. We use direct-sequence spread spectrum modulation, which makes it highly robust to multipath, motion, and narrowband noise. We use a 127-chip pseudorandom code, repeating once per data symbol, and modulate its amplitude with orthogonal sine waveforms encoding 4-bit symbol values. We add the orthogonal sines to a constant “pedestal,” which is inefficient in an information-theoretic sense, but makes synchronization easier. We describe a robust and computationally efficient transmitter and receiver implementations and show experiments on real and simulated data.

Research and Simulation of GPS Navigation Signals

There are most important strategic significance in our country as well as the carrier rocket, ballistic missiles, the development of the manned space engineering that GPS signal simulation of satellite navigation system has. The structure and principle of GPS navigation and positioning signal were discussed in detail in this paper, with practicality as the starting point, the navigation message is transmitted by the use of pseudo random noise code phase-modulated signal, and the method of direct sequence spread spectrum modulation system is used to simulate the signal of GPS satellite orbit based on the MATLAB/Simulink platform. Then the simulation research and analysis of C/A code and P code in the frequency domain and time domain with it`s correlation is carried on, at the same time, the C/A code frequency domain is captured by using the fast Fourier transform method (FFT).finally the space transmission characteristics of GPS signal is simulated under Gaussian noise.it is show that the simulation result is close to the theoretical value, and the accuracy is better.

A New Synchronization Method for Direct Sequence Spectrum Spread Based Systems

Abstract For precise indoor localization accurate synchronization is necessary. In this paper we propose a new synchronization method for direct sequence spread spectrum modulation based systems, which enables a more accurate correlation peak detection. We provide comprehensive statistical analysis and numerical results for the decision error probability assuming both coherent and non-coherent receiving via an AWGN channel. The essence of the proposed method is the two overlapping correlators, which allows taking into account the statistically not independent noise components to reduce the error probability of the correlation peak detection.

Plc Based Monitoring and Controlling System Using Wi-Fi Device

A system for controlling electrical appliances using power line communication and monitoring data. Control messages are sent over Wi-Fi network from Wi-Fi device to personal computer which then couples the message to power line using micro controller with serial port interface. Power lines which are present in all infrastructures are used as physical media to transmit data over 220/50Hz signal to control electrical appliances and to monitor. Here we are monitoring temperature. The data from the micro controller is coupled onto power line using power line communication modem and DSSS( direct sequence spread spectrum ) modulation technique is employed to transmit data. The receiver unit consists of PLC modem, micro controller and can be connected in any power line network. The receiver unit controls the flow of electricity to the socket.

Performance simulation and implementation of gold sequences in underwater acoustic CDMA

Underwater Acoustic Network (UAN) is becoming a hotter research area of underwater acoustic communication recently. Underwater acoustic channels are restricted by narrow bandwidth, long delay and high ambient noise, so Code Division Multiple Access (CDMA) appears to be a promising multiple access technique for UAN. However, due to low underwater data rate, only short pseudo-random sequences are available. Comparing to m sequences, Gold sequences with the same length show the same cross-correlation properties but enable networks to support more users. This paper examines the performance of short Gold sequence in underwater acoustic channel, to determine whether it is a good choice for UAN. Specifically, the paper makes contributions on the following fronts: (1) Based on a Rayleigh fading shallow water acoustic channel model, the performance of bit error rate (BER) of a 63-bit Gold-sequence up to 65 users CDMA is simulated and evaluated in MATLAB platform. (2) Underwater CDMA nodes using Gold-sequence Direct Sequence Spread Spectrum (DSSS) modulation is implemented with National Instruments' new embedded device (cRIO9076). An experiment at sea will be conducted at Xiamen Port to confirm the better performance of short Gold sequences in underwater CDMA.

Experimental demonstration of weak-light laser ranging and data communication for LISA

Interferometric gravitational wave detectors with an unequal and time-varying arm length configuration like the Laser Interferometer Space Antenna rely on time-delay interferometry (TDI) for laser frequency noise subtraction. However, the TDI algorithm requires a laser ranging scheme with meter accuracy over a five million kilometer arm length. At the end of each arm only about 100 pW of light power will be detected for gravitational wave measurements and only 1% of this power can be used for laser ranging in order to avoid degradation in the phase stability of the science measurements. Here, we present the first experimental demonstration of such a ranging scheme at 1 pW power levels using a Direct Sequence Spread Spectrum (DS/SS) modulation. This type of modulation also enables optical communication by encoding data with ranging signals and provides significant noise reduction against spurious interfering signals for bidirectional ranging. Experimental results show ranging measurements of 42 cm at 3 Hz and the viability of highly reliable data transfer at several kilobits per second.

Binary De Bruijn sequences for DS-CDMA systems: analysis and results

Code division multiple access (CDMA) using direct sequence (DS) spread spectrum modulation provides multiple access capability essentially thanks to the adoption of proper sequences as spreading codes. The ability of a DS-CDMA receiver to detect the desired signal relies to a great extent on the auto-correlation properties of the spreading code associated to each user; on the other hand, multi-user interference rejection depends on the cross-correlation properties of all the spreading codes in the considered set. As a consequence, the analysis of new families of spreading codes to be adopted in DS-CDMA is of great interest. This article provides results about the evaluation of specific full-length binary sequences, the De Bruijn ones, when applied as spreading codes in DS-CDMA schemes, and compares their performance to other families of spreading codes commonly used, such as m-sequences, Gold, OVSF, and Kasami sequences. While the latter sets of sequences have been specifically designed for application in multi-user communication contexts, De Bruijn sequences come from combinatorial mathematics, and have been applied in completely different scenarios. Considering the similarity of De Bruijn sequences to random sequences, we investigate the performance resulting by applying them as spreading codes. The results herein presented suggest that binary De Bruijn sequences, when properly selected, may compete with more consolidated options, and encourage further investigation activities, specifically focused on the generation of longer sequences, and the definition of correlation-based selection criteria.

Pseudo-Random Binary Sequence Selection for Delay and Add Direct Sequence Spread Spectrum Modulation Scheme

Recently, correlation delay shift keying (CDSK) has been proposed as a modulation scheme for noncoherent detection which inherits the advantages of conventional spread-spectrum communications using a chaotic reference signal. The CDSK modulation scheme transmits the sum of a chaotic reference signal with its delayed modulated version. In this paper, we consider the utilisation of pseudo-random binary sequences (PRBS) instead of chaotic reference signals. This new modulation scheme is defined as the delay and add direct sequence (DADS) modulation scheme. DADS offers some interesting properties compared to CDSK, mainly the possibility to select some PRBS which improves the BER performance. To this end, a new criterion for PRBS selection is proposed. Theoretical analysis and simulation results show that the BER performance of CDSK is comparable to DADS with arbitrary PRBS, however the DADS performance can be improved by 3 dB with PRBS selection.

A co-operative beamforming solution for eliminating multi-hop communications in wireless sensor networks

This paper proposes a new system architecture for continuous monitoring wireless sensor networks, utilizing recent developments in the areas of cooperative beam-forming, radio frequency integrated circuit technology, and spread-spectrum techniques. In the proposed system, nodes are activated only when they are triggered to send their own data to the fusion center directly, without burdening the network with MAC layer collisions and energy-consuming routing algorithms, thus guaranteeing long lifetime cycles. The nodes consist of a simple active reflector circuit which is synchronized by an incident wave transmitted by a distant base station. Since the nodes can be deployed in large numbers, the network acts as a single antenna array with high directive gain pointing towards the direction of the fusion center. At the receiver, data from each node can be de-multiplexed with the use of a frequency shift keying direct sequence spread spectrum modulation scheme that enables multiple access without destroying the beamforming characteristics of the network.

Immediate neighbor scheduling (INS): An adaptive protocol for mobile ad hoc networks using direct-sequence spread-spectrum modulation

We investigate a new approach for scheduling transmissions in a mobile ad hoc network employing direct-sequence spread-spectrum (DSSS). Multiple-access interference may be better tolerated in these systems, allowing higher levels of spatial reuse and a reduction in the overhead required to schedule transmissions. We present a protocol which leverages these features of DSSS to support greater end-to-end throughput and terminal mobility rates. A protocol extension allows terminals to adjust protocol overhead in order to preserve network connectivity in sparse networks. For each transmission, terminals use a combination of common and transmitter-oriented spreading sequences in a format which allows for discovery of nearby terminals and adaptation of transmission rates to maximize throughput. The protocol does not operate over an artificial network graph, nor does it require an initialization phase or two-way exchange of information during a transmission slot. Through simulations, we evaluate the performance of the transmission scheduling protocol in a variety of static and mobile scenarios. For comparison, we also simulate a centralized transmission scheduling protocol with perfect knowledge of topology.

Ranging and phase measurement for LISA

The LISA phase measurement system (PMS) will provide interferometric phase readout of the primary heterodyne signal at microcycle sensitivity, ranging measurements at sub-meter accuracy and data communication at rates of several kilobits per seconds. Our investigations are focused on inter-spacecraft laser ranging and data transfer for LISA using Direct Sequence Spread Spectrum (DS/SS) modulation onto the laser links. We present the setup of an optical experimental to test the levels of performance achievable with a single laser link as well as a new hardware prototype based on FPGA (Field Programmable Gate Array) processing to perform high-accuracy phase readout of the optical signal, ranging measurements, data communication and is suitable for clock noise demodulation and digital laser-phase locking.

An effective defensive node against jamming attacks in sensor networks

AbstractJamming is defined as the act of intentionally directing electromagnetic energy towards a communication system to disrupt or prevent signal transmission. In the context of wireless sensor networks (WSNs), jamming is the type of attack which interferes with the radio frequencies used by sensor nodes and may be viewed as a special case of denial of service (DoS) attacks. Herein, we outline the possible jamming attacks a WSN may encounter. The main contribution of this paper is the outline of the design specifications of a prototype node ‘Ares’ that effectively defends jamming attacks. Our focus is on frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS), two of the most effective countermeasures against jamming. The main novel aspect of Ares is that it uses a hybrid FHSS–DSSS approach to defend jamming attacks. We suggest the use of a specific FHSS technique in 5 GHz band with 51 frequency channels wherein the channel sequence is generated using a key (which derives from a secret word), known only to the sink and the sensor nodes, as a seed. Each channel uses DSSS modulation with 16‐bit pseudo noise (PN) code. The PN code derives from the same key used for FHSS channel generation. The pre‐eminence of our method against alternative anti‐jamming techniques is demonstrated through extensive simulation tests. Copyright © 2008 John Wiley & Sons, Ltd.

Noise Analysis of Power-Line Communications Using Spread-Spectrum Modulation

Ergodic chaotic parameter modulation (ECPM), based on a spreading chaotic dynamic system, has shown promise for power-line communications (PLC) due to its simplicity in receiver design. Alternatively, direct sequence spread-spectrum modulation is known for its strengths in its resistance to multipath fading and some inherent narrowband interference suppression capability and thus is a logical choice for the difficult power-line environment. Previous work has evaluated the general analytical solution for the signal-to-noise ratio (SNR) for these techniques assuming an idealized implementation. This study provides a more detailed evaluation of the SNR as a function of gain factor, individual noise components and other issues that could reduce the overall effectiveness of the PLC technique. Improvements in symbol error probability with an increase in respective gain factors for various SNR conditions are shown. This study facilitates a direct SNR comparison of two modern PLC techniques in a noise-limited channel not previously performed.

Effective Communication Strategies for Noise-Limited Power-Line Channels

Ergodic chaotic parameter modulation (ECPM) has recently been proposed as a viable modulation technique for power-line communications (PLC) due to its robustness to multipath conditions and low complexity in receiver design. While performance of ECPM has been found to be satisfactory in limited noise conditions, performance issues for other hostile challenges in the power-line environment, such as narrowband and impulsive noise, have not been extensively studied for this technique. Numerous studies have been performed on direct-sequence spread-spectrum (DSSS) modulation used in a wireless channel. The technique has been found to be well suited for a mobile environment due to its resistance to multipath fading and inherent narrowband interference suppression capability. For this study, PLC performance is investigated for both the DSSS and ECPM receiver for PLC. A signal-to-noise ratio (SNR) analysis is presented which investigates the noise-limiting properties of the power-line channel. This work provides a detailed insight to communication system performance in a power-line environment that includes the presence of significant narrowband and impulsive noise. It is concluded that while DSSS significantly outperforms ECPM in terms of bit-error rate for a Gaussian white noise-limited channel, the performance of the two techniques is similar for low SNR communication dominated by narrowband or impulsive noise. While the implementation of DSSS is more complex, ECPM is found to be less robust to low-frequency interference