A Study on Propagation Characteristics of Spread Spectrum Sound Waves Using a Band-Limited Ultrasonic Transducer

2004 ◽  
Vol 16 (3) ◽  
pp. 333-341 ◽  
Author(s):  
Akio Yamane ◽  
◽  
Taketoshi Iyota ◽  
Yongwoon Choi ◽  
Yuzuru Kubota ◽  
...  
Keyword(s):  
Spread Spectrum ◽  
Ultrasonic Transducer ◽  
Ultrasonic Waves ◽  
Sequence Length ◽  
High Signal ◽  
Propagation Characteristics ◽  
Positioning Systems ◽  
Signal Discrimination ◽  
Band Limited ◽  
Code Division Multiple

Propagation characteristics and range experiments of spread spectrum 40kHz ultrasonic waves have been explored under band-limited frequency. Comparative experiments were conducted using two arrangements combining a broadband speaker and a microphone for the broadband case, and an all-purpose receiving transducer and the broadband speaker for the band-limited case. Under the broadband condition, range accuracy measurements and evaluation of signal discrimination in a code division multiple transmission were made demonstrating 0.034% (corresponding to about 7mm in range distance) of range accuracy for a full-scale distance of 21.6m, demonstrating high signal discrimination. The severely band-limited experiment improved accuracy from 0.084% for a distance of 8.4m to 0.063% for a greater distance of 14.4m using a longer M-sequence length by extending shift registers from 10-bit to 15-bit. These experimental results show promise in the intended application of ultrasonic spread spectra to local positioning systems.

scholarly journals Incremental gradient algorithm for multiuser detection in multi-carrier DS-CDMA system under modulation schemes

2018 ◽  
Vol 7 (2.6) ◽  
pp. 311
Author(s):  
Sumitra N. Motade ◽  
Anju V. Kulkarni
Keyword(s):  
Spread Spectrum ◽  
Multiple Access ◽  
Minimum Mean Square Error ◽  
Multiple Access Interference ◽  
Gradient Algorithm ◽  
Channel Noise ◽  
Cdma System ◽  
Communication Performance ◽  
Optimum Performance ◽  
Code Division Multiple

Nowadays, Multicarrier Direct sequence code division multiple access (MC DS-CDMA) systems are used in mobile communication. Performance of these systems are limited by multiple access interference (MAI) created by spread-spectrum users in the channel as well as background channel noise. This paper proposes an incremental gradient descent (IGD) multi-user detection (MUD) for MC DS-CDMA system that can achieve near-optimum performance while the number of users is linear in its implementation complexity.  The IGD algorithm make an effort to perform optimum MUD by updating one user's bit decision each iteration in the best way. This algorithm accelerates the gradient algorithm convergence by averaging. When a minimum mean square error (MMSE) MUD is employed to initialize the proposed algorithm, in all cases tested the gradient search converges to a solution with optimum performance. Further, the iterative tests denote that the proposed IGD algorithm provides significant performance for cases where other suboptimum algorithms perform poorly. Simulation compares the proposed IGD algorithm with the conventional detectors. 

scholarly journals Accuracy on Indoor Position Measurement by Using Spread Spectrum Ultrasonic Waves

2008 ◽  
Vol 44 (6) ◽  
pp. 465-473 ◽  
Author(s):  
Akimasa SUZUKI ◽  
Taketoshi IYOTA ◽  
Akio YAMANE ◽  
Yuzuru KUBOTA ◽  
Kazuhiro WATANABE
Keyword(s):  
Spread Spectrum ◽  
Ultrasonic Waves ◽  
Position Measurement

scholarly journals A Fuzzy Controlled Image Watermarking Based on a Dual Transform Technique

2016 ◽  
Vol 5 (1) ◽  
pp. 83-92
Author(s):  
Bander Albarakati, Abdullah Basuhail, Gibrael Abo Samra Bander Albarakati, Abdullah Basuhail, Gibrael Abo Samra
Keyword(s):  
Fuzzy Logic ◽  
Spread Spectrum ◽  
Image Watermarking ◽  
Error Correcting Code ◽  
Recovery Process ◽  
Discrete Wavelet ◽  
Hybrid Watermarking ◽  
High Level ◽  
Code Division Multiple

This paper presents a new watermarking technique using hybrid image transforms that aims to be very robust against attacks. It also aims to reduce the amount of distortion created from embedding the watermark as much as possible, and have good capacity. The proposed system uses a hybrid watermarking technique that is based on Non-Subsampled Contourlet Transform and Discrete Wavelet Transform. In addition, the proposed system makes use of the fuzzy logic to automatically choose the strength of the embedded watermark. Furthermore, the system uses Spread Spectrum Code Division Multiple Access to embed and recover the watermark after transforming the image. To enhance recoverability of the watermarks, the system uses a high level of redundancy in the embedding process, which allows a powerful Error Correcting Code to be used in the recovery process. The fuzzy logic is used to help the system in producing watermarked images that reserve their quality and not be heavily altered after embedding the watermark. Experiments were performed to measure the quality of the proposed system using JPEG compression attacks. The results showed that the proposed system is robust and has good capacity and imperceptibly although it suffers from being computationally complex.

Effects of Briquettes with Different Crack Structures on Propagation Characteristics of Ultrasonic Waves under Wetting Conditions

2020 ◽  
Author(s):  
Gang Wang ◽  
Jinzhou Li ◽  
Huaixing Li ◽  
Zhiyuan Liu ◽  
Yanpei Guo ◽  
...  
Keyword(s):  
Particle Size ◽  
Ultrasonic Velocity ◽  
Bituminous Coal ◽  
Ultrasonic Attenuation ◽  
Crack Size ◽  
Ultrasonic Waves ◽  
Ultrasonic Frequency ◽  
Propagation Characteristics ◽  
Sample Mass ◽  
Velocity Increase

Abstract In order to examine the effect of briquettes with different crack structures on ultrasonic characteristics under different wetting conditions, a series of ultrasonic testing are carried out on briquettes at different wetting heights and the ultrasonic characteristics in these coal samples are explored. The results show that ultrasonic amplitude is positively correlated with the emission voltage, whereas ultrasonic frequency is negatively correlated with the emission voltage. Changes in both are closely related to the particle size and density. The ultrasonic velocity is positively correlated with the wetting degree. Sample mass has the greatest effect on the ultrasonic velocity, followed by particle size, and pressure has the smallest effect. At dry stage, ultrasonic velocity in gas coal is less than that in bituminous coal. The opposite is true in the fully wet state. The influence of crack thickness on ultrasonic velocity gradually increases with the wetting degree increasing. At dry stage, the velocity gradually increases with the crack dip increasing, while as the wetting height increasing, magnitude of velocity increase gradually decreases with the dip increasing. The ultrasonic attenuation in the briquettes reduces with the emission voltage enhancing. The attenuation decreases with sample particle size, crack thickness and crack size decreasing and with sample mass, pressure and crack dip increasing. The ultrasonic attenuation shows a trend of increase before decrease with the wetting height increasing. The attenuation of ultrasonic wave increases with wave velocity increasing for intact samples and shows a trend of increase before decrease for cracked samples.

Design of Logistic Map-Based Spreading Sequence Generation for Use in Wireless Communication

2015 ◽  
pp. 81-121 ◽  
Author(s):  
Katyayani Kashayp ◽  
Kandarpa Kumar Sarma ◽  
Manash Pratim Sarma
Keyword(s):  
Wireless Communication ◽  
Spread Spectrum ◽  
Logistic Map ◽  
Chaotic Sequence ◽  
Wireless Channel ◽  
Computational Time ◽  
Spreading Sequence ◽  
Sequence Generation ◽  
Critical Issues ◽  
Code Division Multiple

Spread spectrum modulation (SSM) finds important place in wireless communication primarily due to its application in Code Division Multiple Access (CDMA) and its effectiveness in channels fill with noise like signals. One of the critical issues in such modulation is the generation of spreading sequence. This chapter presents a design of chaotic spreading sequence for application in a Direct Sequence Spread Spectrum (DS SS) system configured for a faded wireless channel. Enhancing the security of data transmission is a prime issue which can better be addressed with a chaotic sequence. Generation and application of chaotic sequence is done and a comparison with Gold sequence is presented which clearly indicates achieving better performance with simplicity of design. Again a multiplierless logistic map sequence is generated for lower power requirements than the existing one. The primary blocks of the system are implemented using Verilog and the performances noted. Experimental results show that the proposed system is an efficient sequence generator suitable for wideband systems demonstrating lower BER levels, computational time and power requirements compared to traditional LFSR based approaches.

scholarly journals Analysis of Multiple-Access Discrimination Techniques for the Development of a PSD-Based VLP System

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1717 ◽  
Author(s):  
Álvaro De-La-Llana-Calvo ◽  
José-Luis Lázaro-Galilea ◽  
Alfredo Gardel-Vicente ◽  
David Rodríguez-Navarro ◽  
Borja Rubiano-Muriel ◽  
...  
Keyword(s):  
Visible Light ◽  
Multiple Access ◽  
Error Rates ◽  
Integration Time ◽  
Optical Signals ◽  
Positioning Systems ◽  
Advantages And Disadvantages ◽  
Positioning Errors ◽  
High Measurement ◽  
Code Division Multiple

There are several technologies and techniques available when developing indoor positioning systems (IPS). Recently, the development of positioning systems based on optical signals has aroused great interest, mainly those using visible light from the lighting infrastructure. In this work, we analyze which techniques give better results to lay the foundations for the development of a Visible Light Positioning system (VLP). Working only with a receiver, it is analyzed what the result of determining the position of different emitters is when they emit simultaneously and without any synchronism. The results obtained by Frequency Division Multiple Access (FDMA) (with digital bandpass filters, I/Q demodulation, and FFT) and Code Division Multiple Access (CDMA) are compared. The interference between signals when emitted simultaneously from multiple emitters is analyzed as well as the errors they cause and how these effects can be mitigated. As a result of the research, the advantages and disadvantages using different multiple-access determination techniques are determined. In addition, advantages and disadvantages of using FDMA and CDMA techniques as well as hardware requirements that make one more feasible than the other are presented. The system behavior, in terms of errors, is established using FDMA and different configurations such as: I/Q, RMS, or FFT. The work also determines the error rates that can be obtained with the different FDMA and CDMA configurations, considering different error scenarios and integration time. Synthetic emulations and empirical tests were performed, which concluded that IPS systems based on optical signals and PSD sensors can achieve very high measurement accuracies and a high measurement rate. Obtained positioning errors in a room of 3 m height are less than 1 cm when working in noisy environments.

scholarly journals Easily-Deployable Acoustic Local Positioning System Based on Auto-Calibrated Wireless Beacons

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1385 ◽  
Author(s):  
José Moreno ◽  
Fernando Álvarez ◽  
Teodoro Aguilera ◽  
José Paredes
Keyword(s):  
Spread Spectrum ◽  
Low Cost ◽  
Experimental Tests ◽  
Real Time System ◽  
Positioning Systems ◽  
Local Positioning System ◽  
Update Rate ◽  
Positioning Algorithm ◽  
Node Position

Self-calibrated Acoustic Local Positioning Systems (ALPS) generally require a high consumption of hardware and software resources to obtain the user’s position at an acceptable update rate. To address this limitation, this work proposes a self-calibrated ALPS based on a software/hardware co-design approach. This working architecture allows for efficient communications, signal processing tasks, and the running of the positioning algorithm on low-cost devices. This fact also enables the real-time system operation. The proposed system is composed of a minimum of four RF-synchronized active acoustic beacons, which emit spread-spectrum modulated signals to position an unlimited number of receiver nodes. Each receiver node estimates the beacons’ position by means of an auto-calibration process and then computes its own position by means of a 3D multilateration algorithm. A set of experimental tests has been carried out where the feasibility of the proposed system is demonstrated. In these experiments, accuracies below 0.1 m are obtained in the determination of the receptor node position with respect to the set of previously-calibrated beacons.

Resolving Precise Temporal Processing Properties of the Auditory System Using Continuous Stimuli

2009 ◽  
Vol 102 (1) ◽  
pp. 349-359 ◽  
Author(s):  
Edmund C. Lalor ◽  
Alan J. Power ◽  
Richard B. Reilly ◽  
John J. Foxe
Keyword(s):  
Auditory System ◽  
Temporal Processing ◽  
Spread Spectrum ◽  
Auditory Evoked Potentials ◽  
Frequency Component ◽  
Broadband Noise ◽  
Event Related Potential ◽  
High Signal ◽  
Natural Environments ◽  
Processing Properties

In natural environments complex and continuous auditory stimulation is virtually ubiquitous. The human auditory system has evolved to efficiently process an infinitude of everyday sounds, which range from short, simple bursts of noise to signals with a much higher order of information such as speech. Investigation of temporal processing in this system using the event-related potential (ERP) technique has led to great advances in our knowledge. However, this method is restricted by the need to present simple, discrete, repeated stimuli to obtain a useful response. Alternatively the continuous auditory steady-state response is used, although this method reduces the evoked response to its fundamental frequency component at the expense of useful information on the timing of response transmission through the auditory system. In this report, we describe a method for eliciting a novel ERP, which circumvents these limitations, known as the AESPA (auditory-evoked spread spectrum analysis). This method uses rapid amplitude modulation of audio carrier signals to estimate the impulse response of the auditory system. We show AESPA responses with high signal-to-noise ratios obtained using two types of carrier wave: a 1-kHz tone and broadband noise. To characterize these responses, they are compared with auditory-evoked potentials elicited using standard techniques. A number of similarities and differences between the responses are noted and these are discussed in light of the differing stimulation and analysis methods used. Data are presented that demonstrate the generalizability of the AESPA method and a number of applications are proposed.

Dynamic Logistic Map Based Spread Spectrum Modulation in Wireless Channels

2018 ◽  
Vol 9 (2) ◽  
pp. 52-65
Author(s):  
Katyayani Kashyap ◽  
Tarun Kumar Sharma
Keyword(s):  
Spread Spectrum ◽  
Wireless Channels ◽  
Logistic Map ◽  
Chaotic Sequence ◽  
Direct Sequence Spread Spectrum ◽  
Computational Time ◽  
Sequence Length ◽  
Spreading Sequence ◽  
Nonlinear Channels ◽  
Spread Spectrum Modulation

Generation of an efficient spreading code in Spread Spectrum Modulation (SSM) is always challenging due to considerations like optimum sequence length, physical layout of registers and power requirements. In this article, a design of a dynamic chaotic spreading sequence for application in a Direct Sequence Spread Spectrum (DS SS) based system with the considerations of wireless channels (Rayleigh and Rician) are presented. Generation of dynamic chaotic sequence for application in linear and nonlinear channels is done and a comparison with static chaotic sequence is presented. Evaluation of performance is done in terms of bit error rate (BER), computational time, mutual information and signal power for faded channel taking into considerations of different modulation schemes, which finally dictates the efficiency of the generated code. The performance of the generated dynamic logistic map-based sequence is compared to that obtained from Gold code under equivalent conditions.

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