A new approach to drift compensation in adaptive feedback communication systems

The paper considers the implementation of adaptive video communication systems. The analysis of the current state of models of color perception is presented on the basis of which conclusions are drawn and further ways of solving problems of correct color representation in adaptive systems are proposed. The results of using the mesopic and scotopic vision apparatus in the framework of one color perception model are presented. Recommendations for further modernization of the color perception model, as well as expansion of the functionality of adaptive video communication systems are given.

This paper evaluates at the various modulation and coding techniques suitable for adaptive data communication system. The techniques evaluated are applicable to HF spectrum. Examples of modulation and coding scheme that are evaluated include PACTOR I, PACTOR II, PACTOR III, GTOR and STANAG 4285. Analysis of system performance is made in the presence of AWGN with future extension for multipath fading conditions. Comparison will be made based on the bit-error rate (BER), packet-error rate (PER) and the throughput. In addition, the effective data rate for all the schemes is compared with the Shannon capacity limit to ensure the optimal utilization of the given channel bandwidth. The modulation and coding scheme that meets all of the above requirements will be used for future adaptive data communication system.

This paper presents capacity limits of novel position aware adaptive cellular communication systems exploiting channel state information (CSI) at the transmitter (CSIT). The position aware adaptive communication systems are benchmarked against state-of-the-art adaptive modulation and coding (AMC) systems that use only feedback or predict CSIT in addition to the feedback CSI. We analyze the position aware adaptive communication systems both with perfect and imperfect position information. Numerical results demonstrate that position aware adaptive systems operate close to the channel capacity over a large range of feedback delays and channel variability with perfect position information. Further, position aware adaptive communication systems can outperform state-of-the-art AMC systems for Gaussian distributed position errors with standard deviations smaller than 2.5 m by more than 0.6 bits/s/Hz.

An adaptive rate communication system based on the new DECT standard is evaluated. One of the three modulated signals, namely /spl pi//2-D2PSK, /spl pi//4-D4PSK and /spl pi//8-D8PSK, is chosen for transmission, according to the channel conditions estimated by the Euclidean distance between the received and detected signals. The simulations show that the adaptive rate DECT system tracks a slowly varying fading channel with Rayleigh distribution in the case of low mobile unit speed. The achieved data throughput is up to three times higher in comparison to the fixed rate DECT communication system. It is shown also that in the presence of cochannel interference, the Euclidean distance switching approach is superior to the RSSI approach.

Covert channels are secret communication paths, which existance is not expected in the original system design. Covert channels can be used as legimate tools of censorship resistance, anonimity and privacy preservation to address issues with rdquonationalrdquo firewalls, citizen profiling and other rdquounethicalrdquo uses of Information Technology. Current steganographic methods that implement covert channels within network traffic, are highly dependent on particular media data or network protocol to hide data. In this paper we investigate the methods and an algorithm for implementing adaptive covert communication system that works on real-world Internet, capable of using multiple application-level protocols as its communication media and can be implemented as network application, therefore requires no system modifications of communicating nodes. The key difference from previous solutions is the use of adaptive redundant mechanism, which allows real-time underlying protocol switching and adaptation to the dynamic network configuration changes. Further, covert channels can be extended with P2P architecture in order to improve channel ressistance.

The work presents a new approach to the concurrent optimization and design of transmitting and receiving parts of the adaptive communication systems (ACS). There is shown that optimal ACS used in the threshold mode provide, under given BER, a bit rate equal to the capacity of the forward channel.

Free-space optical communication is an effective alternative solution to address the “last mile” bottleneck in fiber-optic communication systems. However, its practical performance is significantly affected by phase perturbations and intensity scintillation induced by atmospheric turbulence effects. This paper proposes a multi-aperture adaptive fiber-coupled communication architecture, systematically investigating the optical transmission characteristics in turbulent channels through a combined approach of theoretical modeling and experimental validation. Utilizing the Gamma-Gamma turbulence channel model, quantitative analyses are conducted to elucidate the relationships between the scintillation index, the number of transmitting apertures, and the bit error rate. By establishing an outdoor 2.1 km experimental platform, we demonstrate that multi-aperture diversity transmission combined with closed-loop control reduces the scintillation index by 60% while achieving 10 Gbit/s error-free communication under weak turbulence conditions. Experimental results indicate that the proposed architecture enhances coupling power while maintaining high communication quality. Its modular design ensures high compatibility with mature fiber-optic communication components, providing a solution for constructing low-complexity, high-reliability hybrid optical communication systems in urban environments.

The paper presents an overview of design methodology and results of experiments with a Prototype of highly efficient optimal adaptive feedback communication systems (AFCS), transmitting low frequency analog signals without coding. The paper emphasizes the role of the forward transmitter saturation as the factor that blocked implementation of theoretical results of pioneer (1960-1970s) and later research on FCS. Deepened analysis of the role of statistical fitting condition in adequate formulation and solution of AFCS optimization task is given. Solution of the task – optimal transmission/reception algorithms is presented in the form useful for elaboration of the hardware/software Prototype. A notable particularity of the Prototype is absence of the encoding/decoding units, whose functions are realized by the adaptive pulse amplitude modulator (PAM) of the forward transmitter (FT) and estimating/controlling algorithm in the receiver of base station (BS). Experiments confirm that the Prototype transmits signals from FT to BS “perfectly”: with the bit rate equal to the capacity of the system, and with limit energy [J/bit] and spectral [bps/Hz] efficiency. Another, not less important and confirmed experimentally, particularity of AFCS is its capability to adjust parameters of FT and BS to the characteristics of scenario of application and maintain the ideal regime of transmission including spectralenergy efficiency. AFCS adjustment can be made using BS estimates of mean square error (MSE). The concluding part of the paper contains discussion of the presented results, stressing capability of AFCS to solve problems appearing in development of dense wireless networks.

The article deals with the issues of interference and intelligence protection of radio communication means of the mobile component of the tactical command and control link in the conditions of active use of electronic warfare. The problems arising from the use of standard radio communication means that do not provide a sufficient level of protection against intentional interference and interception of signals by the enemy are analysed. The necessity of developing a scientific and methodological apparatus for adapting the radio networks of the National Guard of Ukraine to the conditions of active interference is substantiated. An analysis of modern radio communication equipment used in the military, including portable radios, satellite communication systems, tactical Wi-Fi solutions and software-based radio networks, is carried out. It is determined that the existing communication systems do not provide effective counteraction to enemy radio jammers, especially in direct contact. A new method of spatial interference rejection based on the optimal location and direction of antenna systems of ground-based transmitters and receivers of UHF/VHF and Wi-Fi radio signals is proposed. The proposed method takes into account the tactical situation, the territorial location of radio network nodes and allows to increase the interference immunity of radio channels by changing the characteristics of antenna systems. A mathematical model of interaction between the elements of the radio communication system and active radio masking means is substantiated, which allows determining the optimal parameters of antenna systems and radiation power. The threshold values of the suppression coefficient are determined, at which the required quality of signal reception is guaranteed under the conditions of targeted concentrated interference. The concept of a stable radio communication zone is expanded, in particular, the dependence of its area on the shape of the radiation pattern and the distance between the elements of the communication system is substantiated. For the first time, a comprehensive analysis of the combined effect of intentional interference and active radio jamming on the stability of radio channels is carried out, which allows a reasonable approach to planning radio communications in the conditions of electronic warfare. An algorithm for determining the area of stable exchange for the points of the operational map of combat operations is proposed, which allows to effectively plan the location of communication means and active radio masking means. The practical significance of the obtained results lies in the possibility of applying the developed method in the creation of adaptive radio communication systems that take into account the real tactical situation, which can significantly increase the efficiency of troop management in the conditions of information influence of the enemy.

Adaptive Digital Satellite Transmission Ground Terminal Design Considerations

With the gradual improvement of the future wireless communication technology, the demand for high information capacity and reliable links in communication systems is also ever-increasing. Programmable topological plasmonic metasurfaces, consisting of artificially engineered structures with robust propagation pathways control, have emerged as a revolutionary technology for stable microwave and on-chip communication systems. Programmable topological plasmonic metasurfaces offer unprecedented flexibility and adaptability in managing multiple communication channels as the propagation paths can be easily reconfigured to meet specific communication requirements. Here, we have experimentally demonstrated the ability to dynamically manipulate electromagnetic waves along eight distinct topological pathways for a multichannel direct communication system. The simulation results of topological plasmonic metasurfaces with different coding schemes have showcased their excellent performance in multichannel wavefront control. Experimental results have consistently aligned with the simulation findings, validating the effectiveness of multichannel topological routes. Furthermore, an eight-channel direct communication system based on a programmable topological plasmonic metasurface is designed and implemented to transmit different information. The proposed multichannel communication system based on a programmable topological plasmonic metasurface opens up new possibilities for high-capacity, efficient, and adaptive communication systems, which hold great potential in transformative applications in areas such as 6G, Internet of Things, and beyond.

The requirements for the next generation wireless systems seek to provide reliable high data rate at low cost. Unfortunately the current wireless communication infrastructure is not fully equipped to cover this unprecedented quality of service. Major obstacles include: limited bandwidth availability, limited transmit power, and signal strength uctuations which are intrinsic to the multivariate wireless channel. Multiple Input Multiple Output (MIMO) antenna systems have emerged as one of the most significant technical breakthrough in modern wireless communications able to satisfy these stringent requirements. However the necessity of assuring a high data rate in a large variety of environments while reducing the antenna array space occupation on portable devices requires an improvement in current MIMO technology. To overcome these limitations, we propose in this thesis, the use of reconfigurable antennas that adaptively change, through RF switches, their radiation properties and frequency of operation according to wireless channel characteristics. The key idea of this work is to show that reconfigurable antennas, through their capability to dynamically change their electrical and radiation properties, can be used to change the propagation characteristics of the wireless channel existing between the transmitting and receiving antennas. The proposed MIMO system breaks from the conventional wisdom that the wireless propagation channel cannot be changed intentionally by the transceivers in the link. Three different novel classes of electrically multi element reconfigurable antennas are proposed as suitable candidates for reconfigurable MIMO systems: i ) a reconfigurable printed dipole antenna array that exploits inter element mutual coupling to achieve pattern reconfigurability, ii ) circular patches capable of exciting higher order modes to achieve pattern and polarization diversity, and iii ) a metamaterial leaky wave array that can be reconfigured in pattern to achieve unprecedented degrees of pattern reconfigurability. To effectively use such antennas with actual communication systems, a low power consumption method for selecting the array configuration is proposed. This technique exploits the close relationship between the environment that surrounds the antenna array and the antenna radiation characteristics in order to select optimal array radiation patterns without the need for intense channel sensing or excessive training. A complete reconfigurable antenna system composed of mutli-element reconfigurable antennas and a control unit capable of efficiently driving the antennas is proposed to deliver unprecedented system performance. Analytical models of the proposed system are used to fully characterize the functionality and performance of the technology. A complete evaluation of the proposed system is conducted through electromagnetic simulations and field measurements collected with a channel sounder specifically designed to measure the performance of multi element antenna systems. It is demonstrated that the novel multi element reconfigurable antenna system is capable of providing i ) increased data rate compared to common non reconfigurable antennas in single link communications as well as in multi-link ad hoc networks, ii ) reduced space occupation by the antenna on the communication device exploiting the principles of pattern and polarization diversity, iii ) reduced number of radio-frequency chains needed at the receiver/transmitter and iv ) reduced amount of transmit power for achieving performance comparable to that of standard non reconfigurable antenna systems.

The wireless communication has undergone a revolution due to advancements in technology. For each new user or application to be a part of communication network the preliminary requirement is the allocation of frequency spectrum band. This frequency band is a limited resource and it is impossible to expand its boundaries. So the need is to employ intelligent, adaptive and reconfigurable communication systems which can investigate the requiremenmts of the end user and assign the requisite resources in contrast to the traditional communication systems which allocate a fixed amount of resource to the user under adaptive, autonomic and opportunistic cognitive radio environment. Cognitive radio technology has emerged from software defined radios wherein the key parameters of interest are frequency, power and modulation technique adopted. The role of cognitive radio is to alter these parameters under ubiquitous situations. The spectrum sensing is an important task to determine the availability of the vacant channels to be utilised by the secondary users without posing any harmful interference to the primary users. In multi carrier communication using digital signal processing techniques, filter bank multi carrier has an edge over other technologies in terms of bandwidth and spectral efficiency. The present paper deals with the multi rate FIR decimation and interpolation filter approach for physical layer of cognitive radio under binary symmetric fading channel environment.

The integration of Deep Reinforcement Learning (DRL) for dynamic beamforming in millimeter-wave (mmWave) and terahertz (THz) communication systems represents a transformative approach to optimizing the performance of next-generation wireless networks. These high-frequency bands offer significant bandwidth advantages but present substantial challenges, including high propagation losses, rapid channel variations, and interference in densely populated environments. DRL, with its capability to learn optimal strategies through interaction with the environment, provides an effective solution to these challenges by adapting beamforming parameters in real time. This chapter delves into the application of DRL for dynamic beamforming, focusing on key aspects such as channel state estimation, interference mitigation, and energy-efficient power control. Through a comprehensive review of current advancements, this chapter highlights case studies, the impact of stochastic channel conditions, and the scalability of DRL models in large-scale wireless networks. Furthermore, the chapter explores the trade-offs between exploration and exploitation within the DRL framework, offering insights into overcoming critical obstacles like computational complexity and real-time decision-making in mmWave and THz systems. The potential of DRL to revolutionize beamforming strategies in these frequency bands is immense, paving the way for more reliable, adaptive, and efficient wireless communication systems.

Recently, multiple-input multiple-output (MIMO) technologies are adopted to wireless communication systems for high-speed, large capacity and high reliability communications. However, there can be variations of communication quality and throughput performance, because MIMO technologies depend on propagation channel environments, where communication property widely changes. An optimal wireless communication systems design which adaptively changes transmission systems depending on channel propagation is effective to realize stable wireless communications therefore, it is important that a transceiver knows propagation environment accurately. In this paper, we propose a new discrimination method for MIMO propagation scenarios by using channel state information (CSI), where azimuth spread (AS) and K-Factor estimation are considered. In addition, we evaluate discrimination performance by simulation, and then we get a discrimination result of high accuracy.