Reliable design of radio relay links in complex propagation environments remains a significant challenge for mission-critical communication systems. This paper presents a propagation-aware link budget methodology that integrates terrain morphology, Fresnel zone clearance, atmospheric attenuation (including gaseous absorption and precipitation), and multipath propagation into a unified analytical framework in accordance with ITU-R recommendations. The main contribution lies in the systematic integration of multiple propagation mechanisms into a unified procedure for link availability estimation and propagation-aware radio-relay link assessment. A representative 15 GHz radio relay link between the Laz tunnel and the Ovcar site, designed for a capacity of 100 Mb/s within a TETRA system, is used as a case study for verification. Analytical calculations of received signal power, fade margin, and link availability are supported by simulation-based verification using Radio Mobile. Good agreement between analytical and simulation-based predictions was obtained, with a received signal level difference below 2 dB. Multipath propagation is identified as the dominant degradation mechanism, while rain attenuation has a secondary impact. The achieved link availability exceeds 99.99%, demonstrates practical applicability for the considered case study.
This paper presents a method for reconstructing the three-dimensional antenna radiation pattern from reduced sampled far-field measurements, thereby reducing the need for extensive mechanical probe scans. The sampling density is selected according to planar near-field measurement principles, enabling an initial plane-wave representation of the radiation field. An iterative interpolation procedure in the spectral domain is then used to recover the missing angular data while accounting for practical measurement resolution limits. The complete source code written in Julia programming language for the reconstruction algorithm is publicly available to support reproducibility and future research.
Accurate channel state information (CSI) is essential for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, yet fast time-varying channels pose significant prediction challenges. Traditional approaches fail under high mobility, while deep learning methods rely heavily on large labeled datasets, limiting generalization with scarce training data. Although large language models (LLMs) show promise, their massive parameter count hinders deployment on resource-constrained edge devices. This paper proposes a lightweight, end-to-end CSI prediction framework built upon a general LLM. A time-frequency dual-domain feature extraction module captures subcarrier correlations and temporal dynamics from historical CSI, overcoming single-domain limitations. The end-to-end design maps historical CSI directly to future states, avoiding error propagation inherent in explicit channel estimation. Parameter efficiency is achieved through low-rank adaptation (LoRA) combined with knowledge distillation from a pre-trained LLM, enabling effective few-shot learning at low computational cost. Simulations demonstrate that the proposed scheme delivers robust prediction accuracy across diverse mobility scenar-ios, maintains strong performance under limited training data, and exhibits zero-shot cross-scenario generalization, significantly outperforming both conventional and deep learning baselines in TDD and FDD modes.
Problem statement. The increasing attention to the electromagnetic environment of radioelectronic equipment (REE) in recent years is caused by the emergence of various types of electromagnetic interference. Among them, ultrashort pulses (USP) stand out, which are characterized by a fast rise time and large amplitude. Modal filters (MF) are proposed to protect against them. They decompose the USP into a sequence of pulses of lower amplitude due to the difference in the speed of modes in the line. MF are traditionally implemented in the form of strip structures, but a promising alternative is cable structures. Meanwhile, this requires a separate engineering approach and experimental verification. The purpose of the work is to develop a prototype MF based on a flat cable and measure its characteristics. Results. A methodology for prototyping and measuring MFs based on a flat cable is presented, and a prototype MF based on it is developed. The results of the MF measurements are compared with the results of computation-al experiments in the quasi-static and electrodynamic analysis systems. The nature of the dependences of the MF transmission coefficient modulus |S21| in the frequency band up to 2 GHz is similar for all types of analysis with a maximum deviation of 5.2 dB. The MF passband is within 75–310 MHz for measurements and two types of analysis. In the frequency range of 0–10 GHz, the measured modulus of the reflection coefficient |S11| of the MF does not exceed minus 7.4 dB. As a result, the developed MF (225 mm long) is capable of attenuating the influencing interference with a total duration of 200 ps (at the 0.5 level) by 7.03 times according to the measurement results, as well as by 4.3 and 7.45 times according to the simulation results in the quasi-static and electrodynamic analysis systems. Practical significance. The results of experimental studies expand the toolkit of engineers in-volved in the development and modification of protective devices (both based on flat cables and completely new ones). The developed MF is notable for its potential for practical application in protecting REE from USP in a variety of areas due to its compact size (225 mm) and low weight (up to 75 g), radiation resistance, reliability, and high protective characteristics.
Engineering solutions for determining the range to moving extended objects, as a rule, involve the use of a radar distance sensor. The main thing in this case is to obtain the minimum error in determining the distance to the object being localized. Note that digital signal processing introduces its own features in determining the methodological error of the distance sensor. The article proposes a solution based on the use of a method of local optimization of parameters of an arbitrary weight function used to smooth out measurement errors in distance sensors based on the principle of a frequency range finder. The methodological component of the error of the weight method is considered as one of the key factors determining the measurement accuracy. The purpose of the study is to optimize the parameters of the weight function, which makes it possible to ensure a minimum of the methodological error of the weight method for smoothing discreteness, and to assess the effect of noise from signal generation and processing equipment on the distance measurement result. Optimization of parameters significantly reduces measurement error, and the effect is the more pronounced, the larger the number of terms included in the decomposition of the weight function, that is, when its form is complicated. At short distances, the noise component of the measurement error has the same order of magnitude as the methodological error, while when the range increases, its value becomes much higher. The most pronounced effect of noise is observed in cases of using more complex weight functions. As the distance increases, the measurement error decreases. It has been shown that known weight functions provide the best results when measuring relatively long ranges. The effect of additive noise on the accuracy of determining the distance using the weight approach to reducing the sampling error was assessed. It has been found that at small measuring distances, the optimal weighting function coefficients provide effective suppression of the noise component. In the area of large distances, a monotonous decrease in noise error is observed, which, however, remains significantly higher than the methodological one. Analytical expression for measurement error variance obtained. The results obtained confirm the effectiveness and practical significance of optimizing the weight functions used in remote measurement systems based on frequency range finders. At the same time, the proposed solutions make it possible to determine the maximum permissible noise level that ensures the achievement of the required measurement accuracy in each specific case.
