Joint application of radar visibility reduction and anti-radar masking technologies to protect aircraft from remote monitoring systems

Using spectral energy equations of transmission-reception of wave processes in radio channel with scattering on object and direct radio channel, analysis of energy ratios of information signals and active masking interference at inputs of receivers of remote monitoring systems is carried out. Measures to reduce visibility are aimed at changing the reflective signatures of objects in the interests of reducing the de-masking features contained in secondary electromagnetic radiation to limits that exclude the performance of radar monitoring tasks at established distances and time intervals. Active interference is designed to mask information signals in receiving channels of radar at power that does not allow detecting their designers by passive radar. In case of joint application of not iceability reducing devices and active jammers, radar range reducing coefficient is determined by product of coefficient characterizing possibility of autonomous masking of information signals and coefficient achievable due to reduction of secondary electromagnetic radiation power in the second degree. The laws of increase of aircraft stealth from radar observation with joint application of technologies of reduction of radar visibility and masking by intentional interference created from sides of protected objects and from assigned points have been investigated. In order to maintain the desired signal-to-noise ratio at the output of the receiver with a decrease in the duration of the probing signal, it is necessary to proportionally increase the density of the emitted energy. With given antenna sizes, the maximum signal transmission range is proportional to the root square of their cyclic carrier frequency; increase of this parameter leads to increase of partial coefficient of directional action and effective area of antenna. With a decrease in the cyclic frequency of the carrier of the probing signal, inorder to maintain the required directional properties of the antennas, it is necessary to increase their dimensions.

Localization of a Power-Modulated Jammer

Jamming is a malicious radio activity that represents a dreadful threat when employed in critical scenarios. Several techniques have been proposed to detect, locate, and mitigate jamming. Similarly, counter-counter-jamming techniques have been devised. This paper belongs to the latter thread. In particular, we propose a new jammer model: a power-modulated jammer that defies standard localization techniques. We provide several contributions: we first define a new mathematical model for the power-modulated jammer and then propose a throughout analysis of the localization error associated with the proposed power-modulated jammer, and we compare it with a standard power-constant jammer. Our results show that a power-modulated jammer can make the localization process completely ineffective—even under conservative assumptions of the shadowing process associated with the radio channel. Indeed, we prove that a constant-power jammer can be localized with high precision, even when coupled with a strong shadowing effect (σ ≈ 6 dBm). On the contrary, our power-modulated jammer, even in the presence of a very weak shadowing effect (σ < 2 dBm), presents a much wider localization error with respect to the constant-power jammer. In addition to being interesting on its own, we believe that our contribution also paves the way for further research in this area.

Anti-jamming Wireless Sensor Network Model

A wireless sensor network (WSN) of a tree-like topology is considered, which performs measurements and transmits their results to the consumer. Under the interference influence, the WSN nodes transmitters low power makes the transmitted information vulnerable, which leads to significant data loss. To reduce the data loss during transmission, a noise-immune WSN model is proposed. Such a WSN, having detected a stable connection absence between a pair of nodes, transfers the interaction between these nodes to a radio channel free from interference influence. For this, the model, in addition to forming a network and transferring application data, provides for checking the communication availability based on the keep-alive mechanism and restoring the network with a possible channel change. A feature point of the proposed approach is the ability to restore network connectivity when exposed to interference of significant power and duration, which makes it impossible to exchange service messages on the channel selected for the interaction of nodes. To support the model, work algorithms and data structures have been developed, indicators have been formalized to assess an anti-jamming system work quality.

Lightweight encryption for short-range wireless biometric authentication systems in Industry 4.0

Most recent solutions for users’ authentication in Industry 4.0 scenarios are based on unique biological characteristics that are captured from users and recognized using artificial intelligence and machine learning technologies. These biometric applications tend to be computationally heavy, so to monitor users in an unobtrusive manner, sensing and processing modules are physically separated and connected through point-to-point wireless communication technologies. However, in this approach, sensors are very resource constrained, and common cryptographic techniques to protect private users’ information while traveling in the radio channel cannot be implemented because their computational cost. Thus, new security solutions for those biometric authentication systems in their short-range wireless communications are needed. Therefore, in this paper, we propose a new cryptographic approach addressing this scenario. The proposed solution employs lightweight operations to create a secure symmetric encryption solution. This cipher includes a pseudo-random number generator based, also, on simple computationally low-cost operations in order to create the secret key. In order to preserve and provide good security properties, the key generation and the encryption processes are fed with a chaotic number sequence obtained through the numerical integration of a new four-order hyperchaotic dynamic. An experimental analysis and a performance evaluation are provided in the experimental section, showing the good behavior of the described solution.

HYBRID COMMUNICATION NETWORK FOR THE PURPOSE OF MARITIME APPLICA TIONS

The article presents the concept of the hybrid communication system for the purpose of maritime applications. The main idea of this system is that it will utilize the seamless roaming concept, which means the communication link at sea will be established automatically (and seamlessly for the user), using many possible communication techniques (cellular, LTE, Wi-Fi, VDES, etc.) which will be selected depending on the current conditions of the radio channel and the requirements and preferences of the user. The paper will introduce the general architecture of the system, the concept of the maritime cloud and the seamless roaming, including the way the latter will be implemented in the system. The authors will also briefly introduce the proposed test-bed of the system’s on-board device. The system presented in the article is one of the major topics of the EfficienSea 2 project (co-funded from the ‘Horizon 2020’ programme) in which the authors of the paper participate.

Radio Channel Capacity with Directivity Control of Antenna Beams in Multipath Propagation Environment

The basic technology that will determine the expansion of the technical capabilities of fifth generation cellular systems is a massive multiple-input-multiple-output. Therefore, assessing the influence of the antenna beam orientations on the radio channel capacity is very significant. In this case, the effects of mismatching the antenna beam directions are crucial. In this paper, the methodology for evaluating changes in the received signal power level due to beam misalignment for the transmitting and receiving antenna systems is presented. The quantitative assessment of this issue is presented based on simulation studies carried out for an exemplary propagation scenario. For non-line-of-sight (NLOS) conditions, it is shown that the optimal selection of the transmitting and receiving beam directions may ensure an increase in the level of the received signal by several decibels in relation to the coaxial position of the beams. The developed methodology makes it possible to analyze changes in the radio channel capacity versus the signal-to-noise ratio and distance between the transmitter and receiver at optimal and coaxial orientations of antenna beams for various propagation scenarios, considering NLOS conditions. In the paper, the influence of the directional antenna use and their direction choices on the channel capacity versus SNR and the distance between the transmitter and receiver is shown.

Optimal nonlinear filtering of M-PSK signals against a background of harmonic interference with a random initial phase

Objectives. The widespread use of radio data transmission systems using signals with multiposition phase shift keying (MPSK) is due to their high noise immunity and the simplicity of constructing the transmitting and receiving parts of the equipment. The conducted studies have shown that the presence of non-fluctuation interference, in particular, harmonic interference, in the radio channel significantly reduces the noise immunity of receiving discrete information. The energy loss in this case, depending on the interference intensity, can range from fractions of dB to 10 db or more. Therefore, interference suppression is an important task for such radio systems. The aim of the work is to synthesize and analyze an algorithm for optimal nonlinear filtering of MPSK signals against a background of harmonic interference with a random initial phase.Methods. The provisions of the theory of optimal nonlinear signal filtering and methods of statistical radio engineering are used.Results. The synthesis and analysis of the algorithm of optimal nonlinear filtering of MPSK signals against the background of harmonic interference with a random initial phase are carried out. The synthesized receiver contains a discrete symbol evaluation unit, two phase-locked frequency circuits of reference generators that form evaluation copies of the signal and interference, and cross-links between them. Analytical expressions are obtained that allow calculating the dependences of the bit error probability on the signal-to-noise ratio and the interference intensity µ. It is established that uncompensated fluctuations of the initial phase of the useful signal have a greater effect on the receiver noise immunity than similar fluctuations of the phase of harmonic interference, especially with low positional signals.Conclusions. Comparison of the obtained results with the results obtained in the case when there are no harmonic interference compensation circuits shows that the use of the obtained phase filtering algorithms allows for almost complete suppression of harmonic interference. Thus, if µ = 0.5 and the probability of error is 10−2, the energy gain at M = 2 is about 2.5 dB, at M = 4 – about 6 dB, at M = 8 and M = 16 – at least 10 dB.

On the assessment of the reliability of the train radio communication channel

The research purposeis to develop an approach to assessing the reliability of a train radio communication channel based on the representation of a radio communication network in the form of a model that includes both traditional elements (various types of equipment, a wire channel) and a radio channel, which is proposed to be described by the availability of radio coverage, which varies depending on the location of the mobile subscriber. In the research methods of the theory of reliability, and, in particular, the assessment of the availability factor of the elements of the radio communication system and communication channels, dynamically changing during the movement of the mobile radio station. In addition, to assess the energy of radio channels, the theory of radio wave propagation was applied, including on the basis of industry recommendations for calculating radio communication networks of JSC Russian Railways. As result of the research, a method was proposed for assessing the dependence of the reliability of a train radio communication channel (in terms of readiness) on the track coordinate. In this case, the radio communication channel dynamically changes the composition of the elements when the mobile subscriber moves along the railway section. Simultaneously, for each point of the section, the calculation formula is also dynamically changed, which makes it possible to find the value of the readiness of the communication channel. The proposed approach allows to identify the sections of technological radio communication networks that are weakest from the point of view of communication reliability and take this information into account when planning work to improve the reliability of communication networks.

Improved Efficiency of Data Transmission in Wireless Communication Systems with Orthogonal Frequency Multiplexing

The active introduction of Orthogonal Frequency Division Multiplexing (OFDM) technology is now beginning to be widely used in wireless transmission systems, television, radio communication, and radio broadcasting. The efficiency of using a dedicated frequency band at a constant high transmission rate allows you to combat interference arising from the transmission of a useful information on the radio channel. A method of improving quality of information transmission in communication systems with orthogonal frequency multiplexing is described. It is shown that with an increase in the number of receiving and transmitting antennas, the noise immunity increases significantly. An experiment was carried out to change the number of receiving-transmitting antennas and the signal-to-noise ratio, and the dependence of the appearance of an error on the number of transmitting antennas was obtained. The work investigated the software model of MIMO OFDM (modulators and demodulators). As a result of the analysis, the dependence of the appearance of the error frequency on the probability of the error was obtained. This showed that the use of OFDM and MIMO places increased demands on channel estimation.