Examination of a method of increasing the spectral and energy efficiency of the nonorthogonal multifrequency spectrally efficient frequency division multiplexing (SEFDM) signals is considered. This method consists in the application of optimal envelopes of signals increased duration on each subcarrier frequency under intersignal interference for fix data rate. Multistep optimization problem for the determination of the set of envelopes of these SEFDM signals was proposed and numerically solved. The proposed optimal SEFDM signals allow to increase spectral efficiency and to reduce the frequency bandwidth up to 32% with respect to orthogonal frequency division multiplexing (OFDM) signals.

The achievement of the boundary values of spectral efficiency is associated with the development of methods for generating and receiving signals with a compact spectrum. The reason is a constant increase in the capacity of existing communication channels caused by an increase in the volume of transmitted information. Moreover, the allocated frequency bandwidths have natural limitations, and they are almost all reached. The effective way to approach the boundary values of spectral efficiency is the application of spectrally efficient signals, such as FTN (Faster-Than-Nyquist) signals. This article proposes to synthesize optimal FTN signals that are more compact in the spectrum than RRC (root raised cosine) pulses-based signals. The criterion of maximum energy concentration in the occupied frequency bandwidth and the constraint on the cross-correlation coefficient are used to solve the optimization problem. The contribution of this work is the optimization of FTN signal shape. The obtained optimal FTN signals provide a 24% increase in spectral efficiency compared to the RRC pulses-based signals. At the same time, the energy loss stays almost unchanged. To the best of authors’ knowledge, this is the first case when the frequency bandwidth reduction is achieved at practically no energy loss. The simulation modeling in channels with additive white Gaussian noise and fading channels is done with regard to the FTN-SC-FDE (Faster-Than-Nyquist - Single Carrier system with Frequency Domain Equalization) structure. The optimal FTN signals presented in this work can be used to increase the spectral efficiency of satellite broadcasting systems, such as DVB-S2/S2X.

We present a review of modeling techniques of thermoelectric generators (TEGs) with the use of the finite element method based on the software of the ANSYS Workbench platform. Comparative analysis of different models and with the experiment is presented. The development direction of methods for studying the properties of promising TEGs, including generators based on MEMS technology, as well as segmented and coaxial types, is discussed. It has been shown that an important step in the design is to calculate the geometric parameters of the thermoelements (TEs) carried out with the help of numerical methods for solving the optimization problem by the criterion of maximizing the power output. The use of modeling techniques makes it possible to determine the activation modes of TEGs, operating temperature range, load resistance, and the output power.

In this paper the research on realization of transmitter for optimal signals which provide high spectral efficiency without significant energy losses is done. HackRF One is chosen as a transmitter. Experiments showed that peak-to-average power ratio (PAPR) of transmitted sequence is higher than theoretical both in case of “classic” signals with rectangular envelope form and optimal ones (with and without restriction on peak-to-average power ratio). It is caused by parasitic amplitude modulation. However, experimental values of PAPR of optimal signals are less than ones of “classic” signals due to absence of transient processes. In future works BER performance of implemented transmitter will be estimated.

The freeze of the 5th generation new radio (5G NR) Release 16 indicates that 5G development has stepped into a new stage. The application of a dedicated low-density parity-check (LDPC) code for channel coding is an important technical advance that distinguishes 5G NR from the 4th generation (4G) long-term evolution (LTE) and LTE-advanced. Although LDPC codes have been used in many different systems, the newly developed LDPC code in 5G NR integrates many cutting-edge technologies to provide better performance and attractive features. Thus, it can be a good reference for channel coding in other evolving systems headed by digital terrestrial television broadcasting (DTTB). In emerging applications, the DTTB system needs to carry information with higher density, while meeting the high requirements for real-time, coverage, and bit error rate of broadcasting. To provide a reference for DTTB channel coding that improves its performance and supports new services, a review of 5G NR LDPC code implementation is carried out from three aspects: code analysis and design, decoding algorithm, and decoder architecture. We thoroughly evaluate each solution and highlight some candidates for existing implementations or directions for further development of the DTTB system.

Determination of the concentration and size of the circulating immune complexes in the blood is an essential part of diagnostics of immune diseases. In this work, we suggest using the dynamic light scattering method to determine the sizes of circulating immune complexes in blood serum. By the dynamic light scattering spectrometer, we found that for healthy and sick donors, the size and concentration of circulating immune complexes differed significantly. The dynamics of formation of these complexes were also examined in this work. It was shown that the formation of immune complexes in the blood of healthy donors is faster than the same reactions in the blood serum of donors with diseases. The results can be used in the diagnostics of the immune status and detection of chronic inflammation. We can recommend the dynamic light scattering method for implementation in biomedical diagnostics.