The article presents the requirements for the bandwidth of the tactical communication network of Armed Forces of Ukraine in the conditions of repelling open armed aggression of the Russian Federation. Some of the modern broadband access stations and the technical basis of their effective functioning are considered. It is emphasized that with limited spatial-frequency-energy resources, an extremely important task is to improve known and develop new methods of information transmission in order to bring the efficiency of using a wireless channel closer to theoretical limits. A family of Index Modulation methods of signals is analyzed, which allow increasing the speed of digital information transmission and / or improving noise immunity due to the introduction of additional signal measurements that ensure the formation and transmission of a certain part of information bits by implementing an implicit information-controlled mechanism for switching the activity state of auxiliary transmission units. Attention is focused on the methods of spatial and index orthogonal frequency modulation of signals. An improved method of Dual-Mode Spatial-Polarization Modulation is proposed, which is based on the combination into a single Signal-Code Construction of the known methods of Spatial-Polarization and Dual-Mode OFDM modulation with modified Constellations of BPSK, QPSK and 16-QAM signals. Analytical expressions for calculating the spectral efficiency of the mentioned Signal-Code Construction are given. It is demonstrated that the proposed Signal Construction retains the advantages of its components – the methods of Generalized Spatial Modulation, Spatial-Polarization Modulation and Dual-Mode OFDM-IM. The limitations of the method in terms of choosing the number of antennas, the size of subcarrier subunits and signal modulation types are shown. The computational complexity of implementing the Maximum Likelihood detector is given and the need to develop suboptimal signal decoding methods is emphasized.
V. Solodovnyk (Fri,) studied this question.