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In the current context of global communications, HF (High Frequency) NVIS (Near Vertical Incidence Skywave) data networks can be of strategic importance, providing short- and medium-range communication capabilities independent of terrestrial configuration and existing conventional communications infrastructure. They are essential in critical conditions, such as natural disasters or conflicts, when terrestrial networks are unavailable. This paper investigates the development of such systems for HF NVIS data communications by introducing a customized Orthogonal Frequency Division Multiplexing (OFDM) protocol with parameters adapted to HF ionospheric propagation, implemented on Software-Defined Radio (SDR) systems, which provide extensive configurability and high adaptability to varying HF channel conditions. This work presents an innovative approach to the application of OFDM narrow-channel aggregation in the HF spectrum, a technique that significantly enhances system performance. The aggregation enables a more efficient utilization of the available spectrum and an increase in the data transmission rate, which represents a substantial advancement in NVIS communications. The implementation was realized using an SDR system, which allows flexible integration of the new OFDM protocol and dynamic adaptation of resources. The work also includes the development of a messaging application capable of using this enhanced HF communication system, taking advantage of the new features of channel aggregation and SDR flexibility. This application demonstrates the applicability of the protocol in real-world scenarios and provides a robust platform for data transmission under conditions of limited access to other means of communication. Thus, this study contributes to the technological advancement of NVIS communications and opens new research and deployment directions in HF communications. [ABSTRACT FROM AUTHOR]

Electromagnetic spectrum (EMS) superiority represents a prerequisite for resilient defence strategies, capable of effective and adequate response to our global security environment. Besides, quantum communications are being considered one of the most promising technologies with applications in security related domains. To this extent, the development of quantum communication infrastructures will significantly impact the architecture of the modern electromagnetic operational environment. Quantum technologies pave the way towards revolutionary technologies by exploiting physical phenomena from different angles and enabling extremely sensitive measurements of multiple parameters including electromagnetic fields. This paper aims to present a short description of quantum technologies with applications for electromagnetic spectrum monitoring and discusses their impact on future electromagnetic warfare operations.

This article investigates the evolving requirements and challenges of modern tactical communications systems, with a particular focus on military-specific waveforms. It is imperative that these systems integrate IP technology, provide sufficient bandwidth, and maintain reliable operation in harsh environments. In designing waveforms, the key criteria include data transmission rate, coverage area, robustness and protection against jamming and detection. However, the implementation of high data transmission rates can lead to reduced coverage area, thus necessitating the use of multiple waveforms that are tailored to different operational requirements. This paper examines a part of the characteristics of narrowband and wideband waveforms operating in the frequency range from 3 MHz to 5 GHz, with channel bandwidths from 3kHz to 50 MHz and supporting data rates of up to 300 Mbps. The analysis focuses on some critical parameters, including signal-to-noise ratio, bit error rate and modulation schemes, with the objective of optimizing long-distance communications and data rate between fixed and mobile points in tactical environments. [ABSTRACT FROM AUTHOR]

By applying a non-standardized methodology and by using electric- and magnetic-field probes of small dimensions (< 1cm), we experimentally characterized the electromagnetic shielding properties of a fabric containing ferromagnetic microwires weaved on a single direction. Electronic microscopy and X-ray spectroscopy revealed the structure, dimensions and chemical elements content of the amorphous magnetic material. Electric shielding factor proved to be very low in the investigated frequency range, but magnetic shielding factor was high, especially when the weaving direction of the magnetic wires corresponded to the polarization direction of the emitting antenna, and showed some resonances. The magnetic shielding efficiency, if checked against an increasing incident magnetic flux density, proved not to change up to 200 nT. The investigated fabric have been previously proved to be very efficient in shielding the field emitted by a mobile phone in its near field, but present results show that near and far field shielding properties are different.

The increase in channel bandwidth and peak-to-average power ratio (PAPR) of modern communication standards poses a serious challenge to performing channel power (CP) and complementary cumulative distribution function (CCDF) measurements in real-time using standard measurement solutions based on spectrum analyzers (SA). Recently, Software Defined Radio (SDR) technology has become a viable alternative to the conventional real-time spectrum monitoring approach based on SA due to its reduced cost. Therefore, in this paper, we propose a novel, innovative, agile and cost-effective solution to enable both CP and CCDF measurements on a state-of-the-art SDR platform. The proposed solution exploits the ability of the SDR equipment to access signal samples in the time domain and defines both CP and CCDF-type measurements. The two measurement functions are software implemented in GNU Radio by designing customized blocks and integrated into a graphical user interface. The proposed system was first tested and parameterized in a controlled environment using emitted signals specific to the IEEE 802.11ax family of wireless local area networks. After parameterization, the SDR-based system was used for over-the-air measurements of signals emitted in the 4G+, 5G and 802.11ax communication standards. By performing the measurement campaign, we have demonstrated the capabilities of the measurement system in performing real-time measurements on broadband channels (up to 160 MHz for IEEE 802.11ax). Altogether, we have proved the usability of CP and CCDF measurement functions in providing valuable insights into the power distribution characteristics of signals emitted by the latest communication standards. By exploiting the versatility of SDR technology, we have enabled a cost-effective solution for advanced real-time statistical measurements of modern broadband signals. [ABSTRACT FROM AUTHOR]

The spatial and temporal variability of the signals emitted by modern communication devices produced a paradigm shift in approaching the human exposure to electromagnetic fields (EMF). This inherent variability requires in situ, agile EMF measurement solutions capable of performing real-time isotropic measurements. The aim of this paper is to describe a new real-time, highly flexible multichannel EMF measurement system that consists of a sensor connected to state-of-the-art software-defined radio (SDR) equipment. In this paper an electric field sensor is proposed, but we also provide information on the extension of the probe to electric and magnetic fields. In the receiver section, the proposed solution is compared in terms of performances (sensitivity and accuracy), costs, and requirements, with standard solutions based on spectrum analyzers or a digital oscilloscope. Finally, the proposed solution was tested considering the signals emitted in various operating scenarios by a mobile device operating in the LTE-A and IEEE 802.11ax mobile communication standards. The results confirm the versatility and efficiency of the proposed solution for in situ EMF measurements of signals emitted by the new generation communication devices. [ABSTRACT FROM AUTHOR]

Present contribution introduces, for the first time, the description of human exposure dynamics to mobile phone radiation by implementing the use of in-air integrated energy density (IED) evolution in time. Using the amplitude probability density (APD) function capability of a real-time spectrum analyzer, we demonstrate the differences in exposure due to five different mobile applications running in Long Term Evolution (LTE) standard, based on energy deposited in air: voice call; voice over LTE (VoLTE); video call, file download and live streaming. This exposimetric method will be of great interest also for the new 5G communication standard. The superiority of the approach has three branches: a) integrated APD allows a sample rate of the order of 0.6 × 108/s which is equivalent to an extremely agile tracing of the power level change in LTE communication standard (happening at every 6.67 μs); b) momentary and mean IED accumulation rate can be computed, and minute differences between mobile applications may be observed during their running time; c) the superficial tissue temperature increase may be rapidly estimated after the period of use of one specific wireless application in the GHz frequency range. The method implemented here also provides the means for rapid usage profile expectancy assessment of a mobile phone user. [ABSTRACT FROM AUTHOR]

A portable radio transceiver with rubber ducky antenna emitting at 446MHz with an output power of 5W was considered as near-field source of electric (E) and magnetic (H) field components when being used in the proximity of the user's face. By taking into account the significant content of ferrimagnetic nanoparticles recently identified to reside in the human brain, we assessed the specific absorption rate (SAR) of energy deposition due to H-component penetrating a presumptive forebrain. H-component SAR contribution to the total SAR is for the first time estimated in such a case, based on an original idea inspired from knowledge on magnetic fluids hyperthermia. [ABSTRACT FROM AUTHOR]

The main challenge for high-frequency (HF) sky wave communication is the non-stationary behaviour of ionosphere parameters, which imposes constraints on choosing carrier frequency, signal bandwidth, modulation and receiver algorithms to overcome channel impairments. Short- to medium-range HF communication could be the most likely scenario for a European country due to the terrain and communication infrastructure spreading. The main aim of this work was to evaluate HF channels in Black Sea region for distances up to 600 km. Passive sounding and ray tracing were used in order to estimate attenuation and propagation modes. The measurement campaign lasted 9 months. The results proved that for evaluated channels, more than one propagation modes were recorded at the receiver site. Attenuation depends on frequency and time of the day. The outcomes of this research are useful for HF frequency management and HF waveform design. [ABSTRACT FROM AUTHOR]

The aim of present research was the experimental characterization of the radiated power and its dynamics in the near-field of mobile terminal during its use in various voice and data application services belonging to either Universal Mobile Telecommunications System (UMTS) or Long-term Evolution (LTE) communication technologies. The quantification of the realistic electromagnetic exposure of human user was done by offering a complementary, non-standardized method that enables a comprehensive dosimetric understanding of radiation impact. Statistical analysis was applied over the radiated power levels measured in different wireless communication situations followed by average and worst case exposure highlighting. Highest power levels were measured for uploading-type applications running under both UMTS and LTE networks. Among UMTS voice application services, VoIP-radiated power levels were on average 1.4 higher than those for VoCS services. The multiplication factor of the radiated power in LTE vs. UMTS was in average 15.3, ranging from 9.3 up to 31.6, depending on the considered application service. Present results demonstrate that highest exposure is expected for the same application type when running under LTE rather than under UMTS standard. [ABSTRACT FROM PUBLISHER]

Design and testing of a system able to characterize the quality of radio link in high frequency range are presented with the objective of providing a starting point for efficient planning of data communication over restricted areas belonging to the territory of Romania. A swept spectrum analyzer cored setup was used in parallel to a Software Defined Radio platform cored setup that enabled determination of capabilities and limitations in describing essential parameters of the momentary availability of data radio link. Ionospheric channels used in experimental session were chosen based on nowcasting data provided by the European Ionosondes System for a radio link 100 km long. The results confirm the necessity of real time description of the ionospheric channel for best performance and stable data rate communication in highly variable conditions of ionospheric behavior. [ABSTRACT FROM AUTHOR]

The paper presents a system designed for automatic measurement of signal level in ionospheric channels based on a spectrum analyzer controlled by a software application developed for fast and flexible sounding. It enables choosing of desired frequencies, bandwidths, times and duration of monitoring and customized recordings. The measured values of two ionospheric channels were compared against the ones provided by the prediction of the commercial application Voice of America Coverage Analysis Program (VOACAP). Sounding recordings proved that automatic measurement is able not only to assess realistic received power versus time continuously but also to distinguish fading periods. [ABSTRACT FROM AUTHOR]

With the development of radiofrequency technology, radiating quasi-stochastic signals like the wireless local area networks (WLAN), a proper procedure of exposure level assessment is needed. No standardised procedure exists at the moment. While channel power measurement proved to overestimate the field strength, weighting techniques were proposed. The paper compares the exposure levels determined by three different procedures, two of them correcting the field level by weighting. Twenty-three experimental cases of WLAN traffic load are analysed in an indoor environment in controlled conditions. The results show the differences obtained when the duty cycle (DC) method is applied comparatively with the application of weighting based on an amplitude–time correction. Significant exposure level reductions of 52.6–79.2 % from the field determined by frequency domain method and of 36.5–72.8 % from the field determined by the DC weighting method were obtained by time–amplitude method. Specificities of weighting factors probability density functions were investigated and regression analysis was applied for a detailed characterisation of this procedure. [ABSTRACT FROM AUTHOR]

Gaining dominance in the entire spectrum of activities, which is specific to the military environment, positions the informational component in the foreground, with a multiplying effect on all areas in which military actions occur. The Joint Vision 2020 concept argues that information, processing and communication networks are central components of any military activity . The paper falls within this context and follow s a characterization of the informational domain from the perspective of highly adaptive organizational structures in complex environments. [ABSTRACT FROM AUTHOR]

Interest for knowing long-term human exposure levels due to mobile communications has increased in the last years. It has been shown that short-term exposure assessment made under standard procedural restrictions is not reliable when it comes to conclusions on long-term exposure levels. The present work is the result of a several week analysis of time variability of electric field level inside traffic and control channels of the GSM900 mobile communication downlink band and it indicates that a temporal model to allow future predictions of exposure on the long run is obtainable. Collecting, processing and statistically analysing the data provide expression of the maximum and weighted field strengths and their evolution in time. Specific electromagnetic footprints of the channels have been extracted, differentiations between their characteristics have been emphasised and practical advice is provided, with the scope of contributing to the development of reliable procedures for long-term exposure assessment. [ABSTRACT FROM AUTHOR]

Assessment of human exposure to RF signals which are rapidly variable in time and wide-banded is not yet standardized. Signals in IEEE 802.11 standards are widespread among population use due to presence of wireless local area network in everyday life. Recently, with technological advancement of real-time vector signal analyzers, a more precise exposure evaluation became achievable. However, such instruments are prohibitive and not available for the majority of metrological laboratories. Therefore, it is of great value to improve accuracy obtained by using swept-spectrum analyzers through procedural adequacy. This paper contributes to the refinement of the measurement procedure of stochastic-like radio signals level by a solution of averaging which responds to the dual variability character of such signals: in time and in amplitude. [ABSTRACT FROM AUTHOR]

Transverse Electromagnetic Mode (TEM) cell is an expanded planar transmission line operated in the TEM mode to simulate a free space plane wave. Present work aimed at the characterisation of a TEM cell model IFI-CC104SEXX in the frequency band 600 MHz - 1.2 GHz for controlled exposure of liquid samples. Bioelectromagnetic experiments need proper dosimetric assessment and this can be done by using a TEM cell. The sample (water) was exposed inside the cell at continuous wave with input powers of 190 mW - 19W and the specific absorption rate of energy (SAR) was determined. Obtained SAR vales were in the limits 0.1-2.6 W/kg enabling low- and medium-power radiofrequency exposure. Calibration curves were obtained for the empty cell and efficiency calculations of absorbed energy in the sample were made. Results indicate the feasibility of using this TEM cell model for further biological effects investigation due to controlled exposure of the specimen. [ABSTRACT FROM AUTHOR]

Radio interception deals with detection, classification and monitoring of radio signals. Radio detection using time-frequency analysis is investigated in this paper. Detection capacity for these algorithms is evaluated using simulation and practical measurements. Tactical Frequency Hopping (FH) signals were used for testing the ability of detection algorithms. Energy detector and spectral estimation is tested against FH signals and results are compared with the ones obtained when using time-frequency analysis. The paper demonstrates that, for FH detection, time-frequency works better compared with classic detection (time domain or frequency domain). Gabor Transform is used for time frequency analysis. Parameters of Gaussian window are tuned according to the blanking time of intercepted FH signals. [ABSTRACT FROM AUTHOR]

Obtaining, analyzing and disseminating information are critical factors for the success of modern military actions. The accuracy and speed at which these operations can be performed may determine the success or the failure of the military actions on the battlefield. In these conditions, military communications systems need to support the rapid transport of information between the operational and tactical echelons. The dynamics of tactical military actions and the great mobility of the weapon platforms impose special conditions on the tactical communications systems. Therewith, the traffic volume exchanged in order to command and coordinate the military actions and to acquire and hit targets grew considerably. Therefore, designing tactical military systems becomes more and more difficult. Because of their lower costs and the need to fulfill interoperability requirements, the military tried to adapt civilian communication protocols (WLAN) for the tactical segment of military communications. Thus, the military tried to implement the Tactical Internet on the battlefield as far as each warfighter and weapon platform. The specifics of tactical military actions imposed the need of designing radio stations capable of transmitting data at high speeds (HCDR - High Capacity Data Radio) and to develop new TCP/IP or UDP compatible protocols. Consequently, the MANET (Mobile Ad-hoc Network) concept was designed, as well as a series of protocols which can operate in conditions characterizing the military environment [1]. [ABSTRACT FROM AUTHOR]

As a part of the management activity specified from modern frequency hopping radio systems, the study of interference includes the Adjacent Channel Interference (ACI) level and the Co-Channel Interference (CCI) level. The paper is focused on these levels of interference and draws some conclusions regarding the use of frequency hopping radio systems. We will compare the use of radio hopping systems in two representative operating modes: fixed secure frequency and frequency hopping. The final aim of the paper is to improve the electromagnetic compatibility in a complex radio network offering a guide to assign and allocate radio resources. [ABSTRACT FROM AUTHOR]

The article surveys the main notions regarding electromagnetic compatibility of JTRS-type systems: electromagnetic compatibility (EMC) specific terms, influence areas of disturbing factors, parameters. Another section identifies natural and artificial perturbations which can occur in the outdoor spaces the JTRS equipment is used in. A similar analysis is performed for indoor spaces, where perturbations occur due to the materials out of which the equipment is fabricated and the processing of the signal at different blocks. The last section identifies the conditions favouring the occurrence of radiofrequency interferences when collocating JTRS equipment. [ABSTRACT FROM AUTHOR]

The paper presents the design and implementation of an electromagnetic field monitoring sensor for the measurement of the Terrestrial Truncked Radio (TETRA) signals using low-cost software defined radio (SDR) platforms. The sensor includes: an SDR platform, a Global Positioning System (GPS) module and a hardware control module. Several SDR platforms having different resolutions of the analog–digital converters were tested in the first phase. The control module was implemented in two variants: a fixed one, using a laptop, and a mobile one, using a Raspberry Pi. The tests demonstrate the following achieved performances: instantaneous acquisition band of 5.12 MHz; dynamic range of the input signal level of (−100 to −30) dBm; frequency resolution of 2.5 kHz; portability and flexibility for use in outdoor environments. The sensor allows complete reporting through amplitude-time-frequency-location descriptors, and in the case of the mobile version, the system performs correctly even at a maximum speed of displacement of 120 km/h. The price of the mobile sensor system variant is approximately EUR 320. [ABSTRACT FROM AUTHOR]

A dual band mobile phone model was used to check the shielding properties of an amorphous ferromagnetic textile against the radiation emitted by the handset. Two frequencies belonging to the 2nd and 3r generation of mobile emission technologies were used, 897 MHz and 1950 MHz. The specific absorption rate (SAR) of energy deposition in a human head phantom was measured in standardized conditions. The textile contained micrometric-diameter wires of a ferromagnetic mixture embedded in a thin glass coat and weaved in a specific way. A set of fabric orientations and configurations (layering) were provided in the experiment in order to achieve a better shielding to the phone's radiation. Compared with the non-shielded handset, SAR deposited in the head while using the fabric-covered phone could be decreased up to 30 % of its initial value - in case of 2G technology and up to 24 % - in case of 3G technology. This type of material shows one of the highest shielding efficiencies of the electric-field component in near-field exposure conditions reported until now. A cubic curve of SAR decrease in depth of the head was revealed in both uncovered and covered handset, the effect of shielding being larger at the higher frequency. [ABSTRACT FROM AUTHOR]