The "e-Czas Radio" is a relatively new Polish time dissemination service that utilizes a 225 kHz AM radio transmitter with additional carrier phase modulation to transmit time messages. This article presents a brief description of the e-Czas Radio message transmission method, along with sample receivers to assess the possible accuracy of end-device synchronization. The main part of the article presents the results of an analysis of time dissemination accuracy using three receivers placed at different distances from the LF transmitter. Although research has shown that time data messages are transmitted with slowly changing emission times (systematic drift), which clearly indicates certain problems with the transmitting devices that should be resolved by the system operator, appropriate compensation for the long-term drift allowed for achieving time synchronization accuracy two orders of magnitude better than that declared by the system operator: approximately 90% of time message detection measurements fall within an error range of +/- 100 mu s. Data obtained from a receiver located at a large distance from the transmitter (over 250 km) also showed a high variation in radio wave propagation conditions during the day and at night.

Modeling phenomena influencing radiocommunication networks, such as 5G-NR, is a key aspect during their development and further optimization. In this paper, one proposes a model, for three different scenario types in urban environments, for user localization accuracy. The model is supported by measurements of real 5G-NR downlink signals carried out in three different urban environments, corresponding to the typical user localization. The main goal of the paper is to present a model for estimating the relation between the environment type, i.e., its statistical parameters, and the estimated localization accuracy in outdoor, light-indoor and deep-indoor environments. Results show that the localization accuracy may degrade from 5 to 295 m when the localization process is performed, just by moving the terminal from outside a building to its inside. This can make the localization service invalid, not only from a user-related perspective but also as a method to adjust beamforming parameters in downlink.

The increasing availability and misuse of unmanned aerial vehicles (UAVs) pose significant security threats, requiring effective counter-unmanned aerial systems (C-UASs). The paper presents the concept of the mobile C-UAS dedicated to countering micro- and mini-class UAVs. The developed C-UAS is hybrid, i.e., its detectors and effectors are placed on the mobile ground station and the UAVs cooperate with it. We focus on the simulation-based assessment of safety zones created by a radio frequency (RF) subsystem of the C-UAS. Various operational scenarios are analyzed to evaluate system effectiveness and highlight the benefits of integrating RF-based countermeasures on UAVs. The results demonstrate the hybrid approach’s potential to enhance the security and efficiency of modern C-UAS applications.

This paper presents a simulation-based study on the characteristics of a 28 GHz Body Area Network antenna at different body sites. The main objective is to evaluate the influence of the antenna position on the body on the performance of the antenna, The importance of using realistic human body models for accurate evaluations is emphasized. The head, torso, and hand components of the CST human model with tissue average properties is used for the study. In addition, assessments are carried out with multilayer tissue head model for comparison. The antenna characteristics are evaluated with these body models, both with and without an antenna holder, which allows the antenna prototype to be attached to the body during measurements.The results show that the antenna location has a significant influence on the characteristics of the antenna, and the presence of the holder also has a significant effect on performance. These results emphases the need to simulate the antenna characteristics at specific intended locations in order to fully understand its performance.

In the article the preliminary analysis of the obtained dual-wideband radio signatures detection is presented. It is based on real, recorded complex radio signal samples using USRP X410 in for various operation modes of several unmanned aerial vehicles (UAVs) in operational conditions, including take-off procedure, flight, control and video transmission. The measurement testbed based on software defined radio (SDR), methodology and measurement scenarios are presented. In addition, the characteristic parameters of the received radio signals are analysed together with the determination of reference data for measuring detection efficiency and the methodology for determining decomposed radio signatures based on cyclostationarity properties, modified to implement a counter-uncrewed aerial systems (C-UAS).

Most small, commercial unmanned aerial vehicles (UAVs) maintain continuous two-way radio communication with the controller. Signals emitted by the UAVs can be used for detection of their presence, but as these drones use unlicensed frequency bands that are shared with many other wireless communication devices, UAV detection should rely on the unique characteristics of the transmitted signals. In this article, low-complexity methods for the detection of chirp symbols in downlink transmission from a UAV produced by DJI are proposed. The presented methods were developed with focus on the ability to detect presence of chirp symbols in radio transmission without a priori knowledge or need for center frequency estimation.

In this article a method for detecting the presence of trains on tracks by analyzing the changes in the cell-specific reference symbols parameters in the downlink signal from nearby LTE base station operating in transmit diversity mode is proposed. The signal processing method to obtain waveforms showing correlation with the presence of trains is described with experimental results on trains detection using real LTE downlink signals from commercial networks. The main outcome of the investigation is that even in case of signal reception using receiver with limited long term stability, which doesn’t allow to track absolute phase values of reference symbols, difference between received phases of symbols transmitted using different antenna ports in base station may be highly correlated with presence of trains on tracks. Proposed reference symbols analysis may be alternative to detection of objects in the environment using bistatic passive radar principle, which couldn’t be used in proposed measurement setup due to low performance of bistatic radar detection using single antenna receiver.

This paper presents measurements of the radio channel at the millimeter-wave band at 28 GHz with a bandwidth of 500 MHz for body-to-vehicle networks. The measurement stand, environment and scenarios are described. The analysis of the preliminary results of the power delay profile is presented. It has been initially shown, that the orientation of the antennas has the greatest impact on the characteristics of the radio channel, while the presence of passengers has has no significant effect.

Modern cellular wireless communication systems of the fourth (4G) and fifth generation (5G) face a problem of various types of interference or intentional jamming. Consequently, a degradation of the services provided and an incorrect network operation may occur. In this paper, configuration of the networks' physical layer is investigated, with the said investigation preceded by the measurement of parameters of commercial networks operating in two different environments, to assess their vulnerabilities to interference or intentional jamming. Finally, a method for analyzing the radio signal received with the use of 5G New Radio (NR), Long Term Evolution (LTE), and Narrowband Internet of Things (NB-IoT) radio interfaces is proposed, to detect and mitigate the negative impact of unwanted signals. Software-based implementation of the proposed method allows one to detect and mitigate co-channel interference, intentional jamming and maintain compatibility of user equipment (UE) with the 3rd Generation Partnership Project (3GPP) standard, as it does not affect operations performed, for instance, at the time and frequency synchronization or channel parameter estimation phases.

Fourth-generation (4G) mobile networks are successively replaced by fifth-generation (5G) ones, based on the new releases of the 3rd Generation Partnership Project (3GPP) standard. 5G generation is dedicated to civilian users and the conducted analytical work shows that it has numerous technological gaps that prevent its direct implementation in military communications systems. However, the recent armed world conflicts showed that closed or public mobile networks are willingly used by soldiers for both private and business communications, and to conduct defensive and offensive operations as well. From the military operation viewpoint, jamming both civil and military systems is one of the essential elements of electronic warfare. This paper focuses on the practical trial of low-energy and smart jamming on a 5G private network using narrowband signals, which facilitates the reduction of the available throughput, e.g. in the time division duplex - uplink (TDD-UL) by 99%, or by 82% in the frequency division duplex - downlink (FDD-DL). This type of jamming also allows for reaching up to 25 dB of energy gain comparing to barrage jamming. The authors moreover investigated jamming the Narrowband IoT radio interface using synchronized, selective jamming. The goal was to propose energy efficient methods that will allow the jammers to work longer and be mounted on a small unmanned aerial vehicle (UAV) that can operate near the gNB. The generation of low-power jamming signals in the gNB vicinity successfully hinders detecting the jammer by the enemy’s electronic reconnaissance systems. The proposed solutions are compared with the test results for other types of jamming methods.

The paper describes the results of a measurement verification of the effectiveness of an asynchronous method of locating an object on a plane using localization signals sent simultaneously from two transmitters placed on that object at a known distance from each other. The advantage of proposed solution is ability to estimate position of mobile object by set of reference receivers that can work asynchronously, which simplifies the construction of reference nodes.

In this paper, an experimental analysis of the localization accuracy in a 5G-NR network operating in various urban environments is presented. Measurements of 5G-NR downlink signals were performed in several environments to investigate the user terminal localization process. The main goal is to analyze the differences in the estimated positions accuracy in three different environments, i.e., outdoor, light-indoor and deep-indoor, when the terminal uses signals from the same gNodeBs and is in the same test area. Results show that the localization accuracy may degrade by 146 m to 273 m when the localization process is performed just by moving the terminal from outside a building to its inside.

Visibility conditions between antennas, i.e. Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) can be crucial in the context of indoor localization, for which detecting the NLOS condition and further correcting constant position estimation errors or allocating resources can reduce the negative influence of multipath propagation on wireless communication and positioning. In this paper a deep learning (DL) model to classify LOS/NLOS condition while analyzing two Channel Impulse Response (CIR) parameters: Total Power (TP) [dBm] and First Path Power (FP) [dBm] is proposed. The experiments were conducted using DWM1000 DecaWave radio module based on measurements collected in a real indoor environment and the proposed architecture provides LOS/NLOS identification with an accuracy of more than 100% and 95% in static and dynamic senarios, respectively. The proposed model improves the classification rate by 2-5% compared to other machine learning (ML) methods proposed in the literature.

In the article the method of user terminal position estimation using the broadcast signals transmitted in the downlink of the NB-IoT interface was presented, including the analysis of the radio channel influence on precision of position estimation as well as the eNodeB (Evolved Node B) synchronization. The practical ability to estimate the position in the test area has been verified in the laboratory conditions, using the reference signals with a variable signal-to-noise ratio and different radio channel profiles. Additionally, the method that allows increasing the precision of the terminal position estimation without the need of increasing the sampling frequency of the radio signal is presented.

In this paper, the measurements of the channel impulse response at mmWave band in office and conference rooms are described. The central frequency is 27 GHz with a bandwidth of 400 MHz. The description of the used measurement stand and considered environments are presented. The initial analysis of the power delay profile, mean delay, and RMS delay spread allows preliminary conclusions to be drawn that there is a significant impact of the dimensions of the rooms on these parameters.

There is a need for investigating radio channels for Body Area Networks considering the depolarisation phenomenon and new types of environments, since these aspects are becoming very important for systems design and deployment. This paper presents an analysis of cross-polarisation discrimination for off-body channels based on a measurement campaign performed in a passenger ferryboat, i.e., where all walls, floors and ceilings are made of metal. Firstly, the measurement campaign, including test-bench and scenarios, as well as the analysis approach, including classification of mutual antennas' orientation and definition of parameters are described. The analysis of results includes distance, on-body antennas location and several scenarios, addressing statistical parameters. Mean values for the cross-polarisation discrimination are in the range of [3.7, 6.8] dB while the standard deviation is around 10.0 dB. There is no dependence of the cross-polarisation discrimination on distance, within the measured range (up to 16 m). It is found that there is no correlation between radio signals received by vertically and horizontally polarised receiving antennas, hence, enabling the application of polarisation diversity in Body Area Networks. The Normal Distribution is the best fit for describing cross-polarisation discrimination, as shown by the analysis of goodness of fit parameters, since it passes many of the tests.

This paper presents jamming and jamming mitigation techniques, which can be used in relation to emerging military systems based on fifth-generation (5G) technology. Nowadays, 5G technology provides incremental improvements over Long Term Evolution (LTE) networks resulting in the enhancement of civilian communications. Considering enormous possible applications of this new technology, it is feasible to use them in military utilities. The authors want to introduce the most important aspects related to the 5G system vulnerability in the context of its use in military scenarios. We also present a quality analysis of adequate solutions for 5G to mitigate the jamming and improve the system immunity. The description of use case scenarios depicts how 5G applications can fit in typical use cases.