Comparative statistical study of mid-latitude MSTIDs over two latitudinal regions using dense GNSS network

This work is devoted to potential sources and mechanisms of the mid-latitude MSTIDs formation based on the analysis and comparison of statistical data in two regions: 1 region near Samara ( 55 N. 50 E), 2 region near Sevastopol ( 45 N, 35 E). The data obtained using a dense GNSS receivers network (> 150 pcs.) in the European part of the Russian Federation. The study was carried out using a new statistical method for determining the vertical slopes of the MSTIDs phase front. It was found that summer nighttime MSTIDs over the region near Samara ( 55 N, 50 E) have the traditional southwest directions of propagation and sloping forward phase fronts, while near Sevastopol ( 45 N, 35 E) northwest directions with sloping backward phase fronts. We suggest that the influence of Mid-latitude Summer Nighttime Anomaly may be a trigger for the northwestward MSTIDs, as unlike the southwestern MSTIDs, they are observed 10 degrees south and only in the summer months and September. We do not propose the exact mechanism of their formation in this article, however, we note that sloping backward phase fronts of MSTIDs couldn't be form by the GWs with sources in troposphere. The propagation directions of the southwestward MSTIDs near Samara ( 55 N, 50 E) are consistent with those that are expected for the growth of Perkins instability

Simulation of periodic synchronization of UAV's clock

Unmanned aerial vehicles (UAVs) is one of the most fast progressing technologies. High space-time flexibility of UAV networks along with the ability to payload sensitive measuring equipment allows establishing aerial wireless sensor networks (AWSNs) with new qualities. However, establishing a rapidly reconfigurable phased antenna array system for precise spatially distributed measurements requires a high-quality frequency-phase synchronization of the AWSN drones. Particularly, this paper relates to the problem of designing a synchronized AWSN with a centralized architecture. By a computer simulation, we assess an accuracy of the periodic synchronization of two crystal oscillators installed at the AWSN drones as onboard clocks. Two synchronization methods are considered: based on the total phase of a single carrier frequency and based on the differential phase of two carrier frequencies. It is shown that for most practical tasks it is sufficient to transmit a synchronizing signal with a period ranging from 1 to 20 seconds. The corresponding synchronization error of two onboard clocks can be held under 1.5 ns in the case of using of OCXO-oscillators and under 10.5 ns when using TCXO-oscillators, respectively

Hardware-software implementation of the compression and transmission of seismic data

A real-time wireless network architecture for seismic data ac-quisition system based on multi-level radio network is proposed. The sin-gle-chip programmable transceiver Si446x that allows creating the first level of the network is considered. Physical layer with GFSK modulation in the sub-gigahertz band is considered. Data link layer implementation with generic frame structure for a network, operating in synchronous mode, is presented. An algorithm for seismic data accumulating and com-pressing is presented. The comparison of existing and proposed solutions is given

Predictability Assess of Multipath Phase Using ARIMA Model

© 2020 IEEE. Physical Layer Security is a promising technique for establishing a secret encryption key in wireless communications. The secret key is distilled from the Channel State Information under conditions of its random fast fading. However, random channel variations are quite smooth on short-term intervals and can be predicted using previous samples. This is a serious threat to secrecy of the generated encryption key. In this study, we assess both prediction error and prediction horizon for real data set of a fast fading carrier phase using the ARIMA model. Influence of the autoregressive model order on the prediction accuracy is considered, optimum ARIMA parameters for forecasting the experimental data are found. We also compare prediction accuracy of the ARIMA that uses fixed model parameters versus accuracy of the auto-ARIMA that employs adaptive estimation of model parameters in different timeframes of the data. Our results showed that effective prediction of real samples of multipath phase was possible only at intervals shorter than 150 ms, and maximum prediction gain did not exceed 40 degrees compared to prediction based on the last known sample

Simulation of short-term instability of UAV's clock

Unmanned aerial vehicles (UAVs) is one of the most fast progressing technologies. High space-time flexibility of UAV networks along with the ability to payload sensitive measuring equipment allows establishing aerial wireless sensor networks (AWSNs) with new qualities. However, establishing a rapidly reconfigurable phased antenna array system for precise spatially distributed measurements requires a high-quality frequency-phase synchronization of the AWSN drones. In particular, this paper relates to the problem of designing a synchronized AWSN with a centralized architecture. A model for simulating random frequency offset of two TCXO or OCXO crystal oscillators used as onboard frequency standards installed at the AWSN drones is presented. Our simulation results show that under continuous real-time synchronization, the synchronization error of the master and slave drones can be held under 1.5 ns for at least 100-second intervals

Amplitude variations of the reflected signal during vertical sounding of the ionosphere at middle latitudes

© 2020 Academic Publishing Center INFRA - M. All rights reserved. In this paper, we discuss the main types of quasiperiodic variations in amplitudes of a reflected signal during vertical sounding of the ionosphere at middle latitudes. The initial experimental data is verti-cal sounding ionograms obtained by the Cyclone iono-sonde. The ionosonde is located in Kazan (59°, 49°) and in standard mode allows us to receive one iono-gram per minute. In the analysis, methods are used to visualize a large flow of ionograms in the form of final summary maps of the state of the ionosphere (A-, H-, As-maps). We give typical examples of quasiperiodic vari-ations in amplitudes of a reflected signal in ionograms and on A-maps for various types of multipath beatings (polarization and due to signal scattering by ionospher-ic irregularities). Frequency properties of such beatings are used to estimate the difference in virtual reflection heights between modes of different polarizations with high accuracy, which makes it possible to refine the form of the electron density profile of the lower iono-sphere. We have detected a phenomenon rare for the mid-latitude Es layer - beatings of two O modes with different virtual reflection heights. We also present features of quasiperiodic variations in amplitudes of a reflected signal on traces of the transient Es layer. We study possible causes of the appearance of such beatings