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"Spread spectrum"
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Hedy's folly : the life and breakthrough inventions of Hedy Lamarr, the most beautiful woman in the world
Describes the lesser-known technological talents of actress Hedy Lamarr and the collaborative work with avant-garde composer George Antheil that eventually led to the development of spread-spectrum radio, cell phones, and GPS systems.
Book
DSSS Signal Detection Based on CNN
With the wide application of direct sequence spread spectrum (DSSS) signals, the comprehensive performance of DSSS communication systems has been continuously improved, making the electronic reconnaissance link in communication countermeasures more difficult. Electronic reconnaissance technology, as the fundamental means of modern electronic warfare, mainly includes signal detection, recognition, and parameter estimation. At present, research on DSSS detection algorithms is mostly based on the correlation characteristics of DSSS signals, and autocorrelation algorithm is the most mature and widely used method in practical engineering. With the continuous development of deep learning, deep-learning-based methods have gradually been introduced to replace traditional algorithms in the field of signal processing. This paper proposes a spread spectrum signal detection method based on convolutional neural network (CNN). Through experimental analysis, the detection performance of the CNN model proposed in this paper on DSSS signals in various situations has been compared and analyzed with traditional autocorrelation detection methods for different signal-to-noise ratios. The experiments verified the estimation performance of the model in this paper under different signal-to-noise ratios, different spreading code lengths, different spreading code types, and different modulation methods and compared it with the autocorrelation detection algorithm. It was found that the detection performance of the model in this paper was higher than that of the autocorrelation detection method, and the overall performance was improved by 4 dB.
Journal Article
The foundations of the digital wireless world : selected works of A J Viterbi
\"Professor Andrew J. Viterbi has been extremely influential in the communications field via his invention of the Viterbi Algorithm, and his championing of CDMA technology developed by his company Qualcomm Inc. This book presents a selection of papers personally selected by him to mark his key technical contributions and his thoughts on CDMA technology as it evolved.\"--Jacket.
Book
Research on a non-sensing measurement method for the G/T values of transparent satellite transponders in orbit
In the design of satellite communication systems based on transparent satellite transponders, satellite companies generally only provide a range of satellite G/T values. To ensure system availability, users use the minimum G/T value for link indicator allocation, resulting in low utilization efficiency of system equipment. The characteristics of transparent satellite transponders and the basic principles of direct sequence spread spectrum communication were studied and analyzed. A non-sensing in-orbit satellite G/T value measurement method based on the measurement signal and the original communication signal of the transponder being transmitted in the same frequency band was proposed. Compared with traditional satellite G/T value measurement methods, this detection method does not require the application of dedicated satellite resources, reduces the cost of satellite G/T value measurement, does not affect the normal communication of the original communication signal of the repeater, improves the utilization efficiency of the satellite repeater, and constructs an experimental testing environment for in-orbit satellite G/T value measurement. The experimental results show that the non-sensing satellite G/T value measurement method is consistent with the traditional satellite resource application G/T value measurement method. The test results can be used to guide the design of satellite communication system links.
Journal Article
Period Estimation of Spread Spectrum Codes Based on ResNet
In order to more effectively monitor and interfere with enemy signals, it is particularly important to accurately and efficiently identify the intercepted signals and estimate their parameters in the increasingly complex electromagnetic environment. Therefore, in non-cooperative situations, it is of great practical significance to study how to accurately detect direct sequence spread spectrum (DSSS) signals in real time and estimate their parameters. The traditional time-delay correlation algorithm encounters the challenges such as peak energy leakage and false peak interference. As an alternative, this paper introduces a Pseudo-Noise (PN) code period estimation method utilizing a one-dimensional (1D) convolutional neural network based on the residual network (CNN-ResNet). This method transforms the problem of spread spectrum code period estimation into a multi-classification problem of spread spectrum code length estimation. Firstly, the In-phase/Quadrature(I/Q) two-way of the received DSSS signals is directly input into the CNN-ResNet model, which will automatically learn the characteristics of the DSSS signal with different PN code lengths and then estimate the PN code length. Simulation experiments are conducted using a data set with DSSS signals ranging from −20 to 10 dB in terms of signal-to-noise ratios (SNRs). Upon training and verifying the model using BPSK modulation, it is then put to the test with QPSK-modulated signals, and the estimation performance was analyzed through metrics such as loss function, accuracy rate, recall rate, and confusion matrix. The results demonstrate that the 1D CNN-ResNet proposed in this paper is capable of effectively estimating the PN code period of the non-cooperative DSSS signal, exhibiting robust generalization abilities.
Journal Article
Spread Spectrum Modulation with Grassmannian Constellations for Mobile Multiple Access Underwater Acoustic Channels
The objective of this study is to evaluate Grassmannian constellations combined with a spread spectrum multiple access scheme for underwater acoustic mobile multiple access communication systems. These communication systems enable the coordination of a fleet of Autonomous Underwater Vehicles (AUVs) from a surface or bottom control unit, e.g., a boat. Due to its robustness against phase rotation, the demodulator of Grassmannian constellations uses non-coherent detection, and the main advantage of such modulation lies in the spectrum efficiency gain with respect to conventional differential modulation. The communication system under study in this paper consists of (i), at the transmitter side, a Grassmannian modulation used in an orthogonal spread spectrum multiple access scheme called Multiuser Hyperbolic Frequency Modulation (MU-HFM) and (ii), at the receiver side, a non-coherent array decoder. The modulation and demodulation are presented as well as the considered spreading sequences. Finally, performances of the proposed transmission scheme are evaluated over replayed underwater acoustic channel responses collected at sea by a multi-sensor acoustic acquisition system.
Journal Article
Electromagnetic Interference (EMI): Measurement and Reduction Techniques
Electromagnetic interference (EMI) is one of the biggest challenges faced during the production of any electronic device. The effect on the performance of the instrument due to these inevitable interferences must be carefully measured to understand and quantify the electromagnetic compatibility (EMC) of the instrument under test. If the EMI profile of the system does not meet the accepted standards, then it becomes necessary to take measures to reduce the influence of these unwanted interferences so that the equipment can be used in the real world. Unfortunately, research and studies on EMI and EMC have not received their due attention from the scientific community. Moreover, the literature available for this area of research is scattered where different sources provide information on one or more (but not all) aspects of EMI/EMC while ignoring the others. With the objective of encompassing this extremely significant area of research in its entirety, this review presents both EMI measurement techniques and EMI reduction techniques in detail. EMI measurement techniques are presented under two sections that deal with emission testing and immunity testing, respectively. Herein, EMI reduction techniques are presented under four sections, where electromagnetic shielding has been given special attention under which various methods used by the scientific community to measure the shielding effectiveness of a material or microwave absorber and its application in EMI reduction are illustrated. This is followed by EMI filters, circuit topology modification and spread spectrum. This review can help students and young scientists in this area to get an idea of the ways to conduct EMI tests as well as the ways that can be employed to reduce the EMI of the system, depending on the application.
Journal Article
Multiuser Chirp Spread Spectrum Transmission in an Underwater Acoustic Channel Applied to an AUV Fleet
The objective of this paper is to provide a multiuser transmission technique for underwater acoustic communication in the framework of an Autonomous Underwater Vehicle (AUV) fleet. By using a variant of a Hyperbolically Frequency-Modulated (HFM) signal, we describe a new family of transmission techniques called MultiUser Chirp Spread Spectrum (MU-CSS), which allows a very simple matched-filter-based decoding. These techniques are expected to provide good resilience against multiuser interference while keeping good robustness to Underwater Acoustic (UWA) channel impairments like Doppler shift. Their implementation for the UWA scenario is described, and the performance results over a simulated shallow-water UWA channel are analyzed and compared against conventional Code-Division Multiple Access (CDMA) and Time-Division Multiple Access (TDMA) transmission. Finally, the feasibility and robustness of the proposed methods are verified over the underWater AcousTic channEl Replay benchMARK (Watermark), fed by several channel responses from sounding experiments performed in a lake.
Journal Article
Selective Notch Frequency Technology for EMI Noise Reduction in DC–DC Converters: A Review
This review presents our band-selective frequency technology of Electromagnetic Interference (EMI) noise spread spectrum in the DC–DC switching converter for communication devices. The DC–DC switching converter generates electromagnetic interference (EMI) noise. To comply with EMI regulations and reduce the need for bulky filters and shielding, noise spread spectrum technology is commonly employed. However, conventional methods may allow noise to encroach upon the signal band. To address this issue, selective notch frequency technology has been developed. This technology creates notch characteristic spectrum bands, ensuring a low noise level within the received frequency range. It detects the received frequency and generates a notch band there using a switching pulse control technology. This technology employs pulse coding techniques, including pulse width coding, pulse phase coding, and a combination of pulse width and phase coding. Then, we demonstrate a technique that tunes the notch band frequency to the received signal one automatically. We review their underlying principles, theoretical analyses, and experimental results, which validate the effectiveness of the selective notch frequency technology. Also, possible applications of this technology to sensor systems are discussed.
Journal Article