scholarly journals High Order Differential Frequency Hopping: Design and Analysis

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Yong Li ◽  
Fuqiang Yao ◽  
Ba Xu
Keyword(s):  
High Speed ◽  
Phase Relationship ◽  
Frequency Hopping ◽  
Higher Order ◽  
High Order ◽  
System Capacity ◽  
Frequency Diversity ◽  
System Efficiency ◽  
Time Frequency ◽  
Differential Coding

This paper considers spectrally efficient differential frequency hopping (DFH) system design. Relying on time-frequency diversity over large spectrum and high speed frequency hopping, DFH systems are robust against hostile jamming interference. However, the spectral efficiency of conventional DFH systems is very low due to only using the frequency of each channel. To improve the system capacity, in this paper, we propose an innovative high order differential frequency hopping (HODFH) scheme. Unlike in traditional DFH where the message is carried by the frequency relationship between the adjacent hops using one order differential coding, in HODFH, the message is carried by the frequency and phase relationship using two-order or higher order differential coding. As a result, system efficiency is increased significantly since the additional information transmission is achieved by the higher order differential coding at no extra cost on either bandwidth or power. Quantitative performance analysis on the proposed scheme demonstrates that transmission through the frequency and phase relationship using two-order or higher order differential coding essentially introduces another dimension to the signal space, and the corresponding coding gain can increase the system efficiency.

scholarly journals Ultrafast and Wideband Microwave Photonic Frequency-Hopping Systems: A Review

2020 ◽  
Vol 10 (2) ◽  
pp. 521
Author(s):  
Qidi Liu ◽  
Mable P. Fok
Keyword(s):  
High Speed ◽  
Satellite Communication ◽  
Microwave Photonics ◽  
Frequency Hopping ◽  
Frequency Bandwidth ◽  
Time Frequency ◽  
Data Capacity ◽  
Military Applications ◽  
Microwave Signals ◽  
Electronic Frequency

The increasing demands to enhance information security in data transmission, providing countermeasures against jamming in military applications, as well as boosting data capacity in mobile and satellite communication, have led to a critical need for high-speed frequency-hopping systems. Conventional electronics-based frequency-hopping systems suffer from low data rate, low hopping speed, and narrow hopping-frequency bandwidth. Unfortunately, those are important aspects to facilitate frequency-hopping in emerging microwave systems. The recent advancement of microwave photonics—the use of light to process microwave signals—provides promising solutions to tackle the challenges faced by electronic frequency-hopping systems. In this paper, the challenges of achieving real-time frequency-hopping systems are examined. The operation principles and results of various microwave photonics-enabled frequency-hopping systems are comprehensively discussed, which have wide hopping-frequency bandwidth and frequency-hopping speed from nanoseconds to tens of picoseconds. Lastly, a bio-inspired jamming-avoidance system that could potentially be used for adaptive frequency-hopping is also introduced.

scholarly journals Efficiency of application of error-correcting coding in digital information transmission systems with wideband signals.

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
A.A. Paramonov ◽  
◽  
Zung Hoang Van ◽  
Keyword(s):  
Information Transmission ◽  
Communication Systems ◽  
Noise Immunity ◽  
Frequency Hopping ◽  
Digital Information ◽  
Frequency Diversity ◽  
Interference Immunity ◽  
Transmission Method ◽  
Transmission Systems ◽  
Time Frequency

The method of transmitting information using broadband signals is recognized as an effective way to combat various types of organized intentional and unintentional interference. Among them, methods for transmitting digital information with frequency-hopping spread spectrum (FHSS) have found wide application. Due to its frequency and energy efficiency, the transmission method with frequency hopping is widely used in information transmission systems for various purposes, including military radio communication systems (RCS), where high interference immunity is required. Both when transmitting digital information under the conditions of the destructive effect of electronic suppression means, and without this effect, the received data sequence contains errors. To detect and correct them, noise-correcting coding is effective. The article considers the case when at the input of the receiver, in addition to its own noise, there is also a deliberate concentrated partial-band noise jamming, occupied by the RCS. An analysis is made of the noise immunity of a RCS with a frequency hopping and DBPSK with the combined use of error-correcting coding and time-frequency diversity of the code symbol. The application in the analyzed RCS of the algorithm of incoherent reception of diversity signals with weight processing and subsequent decoding is considered. It’s shown that the noise immunity of the RCS under the considered conditions turns out to be significantly higher than the RCS, in which the frequency diversity of the code symbol and the noise-immune coding are not used.

Improving Space-Time-Frequency MIMO-OFDM with ICI Self-Cancellation Scheme using Least Square Error Estimator

2015 ◽  
Vol 12 (1) ◽  
pp. 25
Author(s):  
Nur Farahiah Ibrahim ◽  
Zahari Abu Bakar ◽  
Azlina Idris
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Symbol Error Rate ◽  
Space Time ◽  
Least Square ◽  
Error Estimator ◽  
Frequency Diversity ◽  
Time Frequency ◽  
Mimo Ofdm ◽  
Subcarrier Mapping

Channel estimation techniques for Multiple-input Multiple-output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) based on comb type pilot arrangement with least-square error (LSE) estimator was investigated with space-time-frequency (STF) diversity implementation. The frequency offset in OFDM effected its performance. This was mitigated with the implementation of the presented inter-carrier interference self-cancellation (ICI-SC) techniques and different space-time subcarrier mapping. STF block coding in the system exploits the spatial, temporal and frequency diversity to improve performance. Estimated channel was fed into a decoder which combined the STF decoding together with the estimated channel coefficients using LSE estimator for equalization. The performance of the system was compared by measuring the symbol error rate with a PSK-16 and PSK-32. The results show that subcarrier mapping together with ICI-SC were able to increase the system performance. Introduction of channel estimation was also able to estimate the channel coefficient at only 5dB difference with a perfectly known channel.

scholarly journals Time-frequency representations of high order harmonics

2001 ◽  
Vol 8 (10) ◽  
pp. 529 ◽  
Author(s):  
Mette Gaarde
Keyword(s):  
High Order ◽  
Time Frequency

scholarly journals Comparative Study between Healthy Young and Elderly Subjects: Higher-Order Statistical Parameters as Indices of Vocal Aging and Sex

2021 ◽  
Vol 11 (15) ◽  
pp. 6966
Author(s):  
Hee-Jin Choi ◽  
Ji-Yeoun Lee
Keyword(s):  
Higher Order ◽  
Elderly Subjects ◽  
Sex And Gender ◽  
Gender Analysis ◽  
Elderly Male ◽  
Statistical Parameters ◽  
Time Frequency ◽  
Age Related ◽  
Gender And Age ◽  
Vocal Aging

The objective of this study was to test higher-order statistical (HOS) parameters for the classification of young and elderly voice signals and identify gender- and age-related differences through HOS analysis. This study was based on data from 116 subjects (58 females and 58 males) extracted from the Saarbruecken voice database. In the gender analysis, the same number of voice samples were analyzed for each sex. Further, we conducted experiments on the voices of elderly people using gender analysis. Finally, we reviewed the standards and reference models to reduce sex and gender bias. The acoustic parameters were extracted from young and elderly voice signals using Praat and a time–frequency analysis program (TF32). Additionally, we investigated the gender- and age-related differences in HOS parameters. Young and elderly voice signals significantly differed in normalized skewness (p = 0.005) in women and normalized kurtosis (p = 0.011) in men. Therefore, normalized skewness is a useful parameter for distinguishing between young and elderly female voices, and normalized kurtosis is essential for distinguishing between young and elderly male voices. We will continue to investigate parameters that represent important information in elderly voice signals.

scholarly journals Fully Automated Cultivation of Adipose-Derived Stem Cells in the StemCellDiscovery—A Robotic Laboratory for Small-Scale, High-Throughput Cell Production Including Deep Learning-Based Confluence Estimation

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 575
Author(s):  
Jelena Ochs ◽  
Ferdinand Biermann ◽  
Tobias Piotrowski ◽  
Frederik Erkens ◽  
Bastian Nießing ◽  
...  
Keyword(s):  
Stem Cells ◽  
Deep Learning ◽  
High Throughput ◽  
High Speed ◽  
New Technologies ◽  
Human Mesenchymal Stem Cells ◽  
Simulation Software ◽  
System Capacity ◽  
Small Scale ◽  
Production Environment

Laboratory automation is a key driver in biotechnology and an enabler for powerful new technologies and applications. In particular, in the field of personalized therapies, automation in research and production is a prerequisite for achieving cost efficiency and broad availability of tailored treatments. For this reason, we present the StemCellDiscovery, a fully automated robotic laboratory for the cultivation of human mesenchymal stem cells (hMSCs) in small scale and in parallel. While the system can handle different kinds of adherent cells, here, we focus on the cultivation of adipose-derived hMSCs. The StemCellDiscovery provides an in-line visual quality control for automated confluence estimation, which is realized by combining high-speed microscopy with deep learning-based image processing. We demonstrate the feasibility of the algorithm to detect hMSCs in culture at different densities and calculate confluences based on the resulting image. Furthermore, we show that the StemCellDiscovery is capable of expanding adipose-derived hMSCs in a fully automated manner using the confluence estimation algorithm. In order to estimate the system capacity under high-throughput conditions, we modeled the production environment in a simulation software. The simulations of the production process indicate that the robotic laboratory is capable of handling more than 95 cell culture plates per day.

VERY HIGH-ORDER SPATIALLY IMPLICIT SCHEMES FOR COMPUTATIONAL ACOUSTICS ON CURVILINEAR MESHES

2001 ◽  
Vol 09 (04) ◽  
pp. 1259-1286 ◽  
Author(s):  
MIGUEL R. VISBAL ◽  
DATTA V. GAITONDE
Keyword(s):  
Three Dimensional ◽  
Radiation Condition ◽  
Higher Order ◽  
High Order ◽  
High Frequencies ◽  
Decomposition Strategies ◽  
The Impact ◽  
Spurious Modes ◽  
Very High ◽  
Computational Strategy

A high-order compact-differencing and filtering algorithm, coupled with the classical fourth-order Runge–Kutta scheme, is developed and implemented to simulate aeroacoustic phenomena on curvilinear geometries. Several issues pertinent to the use of such schemes are addressed. The impact of mesh stretching in the generation of high-frequency spurious modes is examined and the need for a discriminating higher-order filter procedure is established and resolved. The incorporation of these filtering techniques also permits a robust treatment of outflow radiation condition by taking advantage of energy transfer to high-frequencies caused by rapid mesh stretching. For conditions on the scatterer, higher-order one-sided filter treatments are shown to be superior in terms of accuracy and stability compared to standard explicit variations. Computations demonstrate that these algorithmic components are also crucial to the success of interface treatments created in multi-domain and domain-decomposition strategies. For three-dimensional computations, special metric relations are employed to assure the fidelity of the scheme in highly curvilinear meshes. A variety of problems, including several benchmark computations, demonstrate the success of the overall computational strategy.

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