Fine-Grained Frequencies Meet Synchronous Transmission

<div>Fine-grained frequencies have been used in several recent works to enhance network throughput as well as combat Cross Technology Interference (CTI) issues in licence free ISM bands. We observe that synchronous communication based strategies, due to the scope of inter-frequency capture-effect, are inherently more capable of supporting in-parallel communication over multiple channels even when the Center Frequency Distance (CFD) of the channels are very low (<5 MHz). In this work, we pursue an in-depth study of how fine-grained frequencies can be used in conjunction with synchronous communication to extract the maximum benefit from a very narrow band of available frequencies (e.g., 2- 5 MHz) for in-parallel intra-group communication. In this direction, we propose a simple and efficient group formation strategy to automatically define groups in a given WSN/IoT network to boost up in-parallel intra-group communication efficiency. Through extensive experimental evaluations in existing WSN/IoT testbeds, we show that in-parallel one-to-all dissemination in the groups formed through the proposed strategy can execute with upto 73% higher reliability while consuming upto 41% lower energy as compared to the same running among the groups formed through naive strategy with only 4 consecutive frequencies separated by 1 MHz and upto 20 groups.</div>

Fine-Grained Frequencies Meet Synchronous Transmission

<div>Fine-grained frequencies have been used in several recent works to enhance network throughput as well as combat Cross Technology Interference (CTI) issues in licence free ISM bands. We observe that synchronous communication based strategies, due to the scope of inter-frequency capture-effect, are inherently more capable of supporting in-parallel communication over multiple channels even when the Center Frequency Distance (CFD) of the channels are very low (<5 MHz). In this work, we pursue an in-depth study of how fine-grained frequencies can be used in conjunction with synchronous communication to extract the maximum benefit from a very narrow band of available frequencies (e.g., 2- 5 MHz) for in-parallel intra-group communication. In this direction, we propose a simple and efficient group formation strategy to automatically define groups in a given WSN/IoT network to boost up in-parallel intra-group communication efficiency. Through extensive experimental evaluations in existing WSN/IoT testbeds, we show that in-parallel one-to-all dissemination in the groups formed through the proposed strategy can execute with upto 73% higher reliability while consuming upto 41% lower energy as compared to the same running among the groups formed through naive strategy with only 4 consecutive frequencies separated by 1 MHz and upto 20 groups.</div>

Fine-Grained Frequencies Meet Synchronous Transmission

<div>Fine-grained frequencies have been used in several recent works to enhance network throughput as well as combat Cross Technology Interference (CTI) issues in licence free ISM bands. We observe that synchronous communication based strategies, due to the scope of inter-frequency capture-effect, are inherently more capable of supporting in-parallel communication over multiple channels even when the Center Frequency Distance (CFD) of the channels are very low (<5 MHz). In this work, we pursue an in-depth study of how fine-grained frequencies can be used in conjunction with synchronous communication to extract the maximum benefit from a very narrow band of available frequencies (e.g., 2- 5 MHz) for in-parallel intra-group communication. In this direction, we propose a simple and efficient group formation strategy to automatically define groups in a given WSN/IoT network to boost up in-parallel intra-group communication efficiency. Through extensive experimental evaluations in existing WSN/IoT testbeds, we show that in-parallel one-to-all dissemination in the groups formed through the proposed strategy can execute with upto 73% higher reliability while consuming upto 41% lower energy as compared to the same running among the groups formed through naive strategy with only 4 consecutive frequencies separated by 1 MHz and upto 20 groups.</div>

Algorithm for frequency capture and rectification in a low-orbit satellite IoT communication network

<abstract> <p>In satellite communication systems, due to relative motion between satellites and that between satellites and the ground, the resulting Doppler frequency offset adversely affects communication synchronization. In this research, Doppler frequency offset compensation and phase offset compensation method eliminate the influence of the Doppler effect on synchronization. The proposed algorithm divides frequency estimate into two steps, coarse and precision. Finally, the corresponding frequency offset and phase offset compensation are performed. The simulation results show that the demodulated output results after frequency offset and phase offset compensation agree well with the original modulation data, indicating that the algorithm is valid and accurate.</p> </abstract>

Numerical Simulation of Vortex-Induced Vibration of Two Tandem Cylinders With Different Diameters Under Uniform Flow

Vortex-induced vibrations (VIV) of two elastically mounted circular cylinders with different diameters in tandem arrangement are investigated in a two-dimensional (2D) numerical simulation. The fluid domain is simulated by solving 2D Reynold-Averaged Navier-Stokes equations. Meanwhile, the VIV response of the structures is obtained by solving the motion equation using the 4th Runge-Kutta method. The parameters of the cylinders are designed according to an experimental study of flexible risers. Simulation of an elastically mounted single cylinder is firstly carried out and compared with published experimental results to verify the method utilized in the paper. The results of single cylinder show the response frequencies of the bluff cylinders and the flexible cylinder are comparable. In the simulation of the tandem cylinders, a “frequency capture” phenomenon that the oscillation frequencies of downstream cylinder are locked on to that of the up-stream one although they are with different diameters is observed. It also occurs in the experimental study of flexible cylinders. The mechanism behind is analyzed in the paper.

The Phenomenon of Bistable Phase Difference Intervals in the Times-Frequency Vibration Synchronization System Driven by Two Homodromy Exciters

A vibration system with two homodromy exciters operated in different rotational speed is established to investigate whether the phenomenon of bistable phase difference intervals exists in the times-frequency vibration synchronization system. Some constructive conclusions are proposed. (1) By introducing an average angular velocity perturbation parameter ε0 and two sets of phase difference perturbation parameters and ε2, the frequency capture criterion and the necessary criteria for realizing the times-frequency vibration synchronization are derived. The corresponding stability analysis is carried out. (2) By the theoretical analysis and experiments, it is verified that the times-frequency vibration synchronization system exists the phenomena of bistable phase difference interval. That is, the phase differences between the two homodromy exciters are stable around 180 degrees when they are located at a short distance; the antiphase synchronization phenomenon appears. On the contrary, they are stable around 0 degrees at the in-phase synchronization state. (3) Because of the two homodromy exciters operating in the different rotational speed, the vibration system obtains relatively complex compound motion trajectories; the corresponding application is investigated by adding a feeding material chamber. The times-frequency vibration synchronization system can be used to design the vibration mill for reducing its low-energy zone and developing chaotic mixing equipment for obtaining a better mixing effect.

Selected synchronous state of the vibration system driven by three homodromy eccentric rotors

In order to verify that the vibration system driven by multi-eccentric rotors has multiple synchronous states, a model of three eccentric rotors horizontal installation of plane motion is established to study the coupling dynamic characteristics. Based on the average method of modified small parameters, the frequency capture equation is constructed to obtain the conditions of synchronous motion and vibration synchronization transmission. According to the synchronous conditions, the stability state of achieving synchronous motion is converted into the solution of balance equation of the synchronous torque. There are multiple solutions to the torque equation because of the non-linear characteristics of the vibration system driven by multi-eccentric rotors. Then the stability condition is used to estimate which of the solutions is stable. After substituting the parameters of the experimental machine into the above method, the curves of the phase difference and its stability coefficients of three eccentric rotors system are obtained numerically. Two experiments show that the selected synchronous state depends on the initial condition and external disturbance, and if the vibration synchronization transmission conditions are satisfied, three eccentric rotors can not only achieve vibration synchronization transmission of one motor with switching off the power but also that of two motors with switching off the power.

Экспериментальное исследование влияния внешнего сигнала на режим генерации гиротрона мегаваттного уровня мощности

The frequency capture of radiation by an external signal was experimentally studied for the first time for a megawatt-power gyrotron. An external signal from the magnetron at a frequency of 35 GHz entered the working space of the gyrotron through a synthesized two-mirror quasi-optical converter that allowed transforming the input signal into a working mode. This converter has been recently developed and implemented in the Institute of Applied Physics, Russian Academy of Sciences. The radiation spectra were experimentally obtained in modes of frequency capture and frequency beats. The dependence of the frequency capture bandwidth on the power of the external signal was found. Comparison of experimental results with the data of numerical modelling of gyrotron equations with an external signal showed their good agreement.