Adaptive Receiver Research Articles

Evaluating DNN and LSTM nonlinear compensators for enhanced performance in DCO-OFDM system

Abstract This study proposes a deep neural network (DNN) and long-short-term memory (LSTM) nonlinear compensators method for direct current (DC)-biased optical orthogonal frequency division multiplexing (DCO-OFDM) in indoor visible light communication (VLC) conventional to handle the nonlinearity and retrieve the high-fidelity signals, and compared in terms of performance and complexity. Unlike the data training after fast Fourier transform in existing deep neural network schemes, this study proposes a scheme that uses the time domain waveform data output by photodiodes for direct equalization. The OFDM signal at the receiving end is equalized, which can mitigate hybrid linear and nonlinear impairments and save spectrum resources without requiring the pilots’ assistance. Compared with conventional receivers based on different guide frequencies and existing DL-based reception methods, the proposed adaptive receiver approach yields better bit error rate performance at different signal-to-noise ratios. This research reveals the extreme sensitivity of the LSTM’s performance to system SNR. LSTM outperforms DNN in high signal-to-noise ratio (SNR) situations, but at low SNR, even with high complexity, LSTM falls short of DNN’s performance.

Mathematical models and algorithms for determining the modes of an intelligent stage control sensor

In article discusses models of unlimited track circuits with a receiver, adapting to different working conditions, applied double receiver with one power supply in the middle, which allows you to extend the length of the continuous rail circuit. For this, a goal is set, in which is the development of models of jointless track circuits with an adaptive receiver, in which the rail line must take into account the total stress distribution along the rail line and disturbing factors. The article presents the equivalent circuits of continuous welded rail circuits with an adaptive receiver, algorithmic expressions for determining currents and voltages at the ends of the rail circuit, the coefficients of rail lines with an adaptive receiver are developed, calculation algorithms are presented. In conclusion, a graph is given, according to which it is shown that a continuous rail circuit with an adaptive receiver can operate with an insulation resistance three times lower than the threshold value in any modes of the rail circuit, taking into account the fact that, minimum allowable insulation resistance for tone-on-tone continuous rail circuits is taken as Ri=0,7ohm*km. Derived for the theory and synthesis of solutions, and also proposed new approaches to ensure the operating modes of the rail circuit, taking into account the real and weather conditions of operation.

A Recursive Gaussian Newton Based Variable Parameter Adaptive Receiver for Single-Carrier Underwater Acoustic Communications

A Recursive Gaussian Newton Based Variable Parameter Adaptive Receiver for Single-Carrier Underwater Acoustic Communications

Performance analysis of a hybrid FSO/mmWave/THz system for short-range communication under rain and fog conditions

For fronthaul cellular networks, the suitability of a hybrid free space optical (FSO)/radio frequency (RF) high data rate communication systems such as millimeter wave (mmWave) and terahertz (THz) with reliable connectivity under weather conditions (rain and fog) is proposed and analyzed. The aim of this hybrid system is to suit short-range communication covering 5G/6G and beyond cellular networks. The 4 pulse amplitude modulation (PAM) scheme parallel transmission and adaptive receiver approach is considered for the work. The theoretical work on estimating the attenuation characteristics under various weather conditions is carried out followed by the simulation of a hybrid communication system for obtaining the received power at different link lengths. Based on the received power for a data rate of 1 Gbps signal-to-noise ratio (SNR) and bit error rate (BER) is calculated for a link length of 0.2 km, 0.5 km, and 1 km for 4 PAM. For varying fog conditions, mmWave/THz carrier is found to be suitable with a BER of 10−10 at a link length of 0.5 km. For varying rain rates, FSO performs well with a BER of 10−8. The link length and performance can be improved with increased transmit power in both communication systems. The THz carrier offers a high data rate, and a hybrid system is proposed with FSO/THz to have reliable connectivity in harsh weather scenarios.

BiGRU-Based Adaptive Receiver for Indoor DCO-OFDM Visible Light Communication

Nonlinear devices and channel interference can significantly impact the received signal in visible light communication (VLC). While recent research has explored receiver recovery using deep learning, existing approaches often involve replacing traditional channel estimation and equalization modules with neural network models. However, these models introduce additional data processing steps after fast Fourier transform (FFT), leading to increased complexity. To address these challenges, this study introduces a novel direct time-domain waveform equalization approach using a bidirectional gated recurrent unit (BiGRU) neural network for indoor VLC employing direct current (DC)-biased orthogonal frequency division multiplexing (DCO-OFDM). Unlike previous methods, our proposed scheme utilizes time-domain waveform data from photodiode outputs for direct balancing, harnessing the potent nonlinear processing capabilities of the BiGRU model. We first analyze the nonlinear processing capacity of the BiGRU model and subsequently compare the performance of different receiving methods on a constructed indoor visible-light communication platform. Experimental results demonstrate that the BiGRU-based approach exhibits low complexity and exceptional nonlinear channel learning capabilities. Notably, the proposed method outperforms other strategies in terms of bit error rate without the need for pilot signals. These findings validate the potential of the BiGRU-based DCO-OFDM receiving scheme as a promising solution for future VLC systems.

A deep learning-based adaptive receiver for full-duplex systems

To accommodate the growth of data traffic of 6G and beyond networks, achieving a significant improvement in spectrum efficiency is inevitable. Full-duplex systems are very promising since they have the potential of increasing the spectral efficiency compared to half-duplex systems. The main challenge facing the deployment of full-duplex systems is self-interference. Conventional receivers include series of processing blocks that recover the desired signal after removing the effect of self-interference. In the presence of noise and fading channels, the received signal becomes distorted and the recovery is thus challenging. Deep learning algorithms have shown great success in efficient parameter estimation, as well as adaptive decision making. In this study, a deep learning-based full-duplex receiver, namely FDDR, is proposed to replace the receiver’s entire information recovery process of the full-duplex system rather than optimizing each processing module of the receiver separately. Simulation results show that FDDR approaches the same Bit Error Rate performance as a conventional receiver that uses a Kalman Filter as a channel estimator with 80% less complexity. The Bit Error Rate performance of FDDR is also tested in the case of Doppler frequency mismatch between the training and testing phases, multiple self-interference reflections and cyclic prefix free scenarios and shows superior performance.

ARFA: Adaptive Reception Field Aggregation for 3-D Detection From LiDAR Point Cloud

ARFA: Adaptive Reception Field Aggregation for 3-D Detection From LiDAR Point Cloud

SFBC Recognition over Orthogonal Frequency Division Multiplexing Schemes in the Presence of Inphase and Quadrature Phase Discrepancies for Cognitive Radio Applications

A radio is adaptive if it can autonomously analyze the communications environment and instantly modify its settings to achieve the best possible efficiency. In orthogonal frequency division multiplexing (OFDM) transmissions, identifying the space frequency block coding (SFBC) category utilized is one of the most important tasks of an adaptive receiver. Previous approaches to this problem did not take into consideration the fact that real systems typically suffer from transmission defects. This study offers a novel maximum likelihood recognizer capable of distinguishing between SFBC OFDM waveforms in the context of inphase and quadrature phase differences (IQDs). The theoretical findings show that IQDs arising from the transmitter and recipient can be combined with channel paths to generate so-called effective channel paths. The conceptual examination demonstrates that the outlined maximum likelihood strategy of the SFBC recognition and effective channel estimation processes is implemented by an expectation maximization tool utilizing the error control decoders’ soft outputs. The simulations results reveal that the suggested strategy delivers a much greater recognition accuracy than the typical approaches outlined in the comparable literature. At a signal-to-noise ratio (SNR) of 14 dB, for example, the proposed approach achieves a bit error rate (BER) of 0.00002, which is very close to the case of perfect estimation and compensation for IQDs, outperforming the previous reported works which achieved BERs of 0.01 and 0.02.

Highly Sensitive SPAD-Based Receiver for Dimming Control in LiFi Networks

Visible light communication (VLC) is an emerging mode of wireless communication that supports both illumination and communication. One essential function of VLC systems is the dimming control, which requires a sensitive receiver for low-light conditions. The use of an array of single-photon avalanche diodes (SPADs) is one promising approach to enhancing receivers’ sensitivity in a VLC system. However, because of the non-linear effects brought on by the SPAD dead time, an increase in the brightness of the light might degrade its performance. In this paper, an adaptive SPAD receiver is proposed for VLC systems to ensure reliable operation under various dimming levels. In the proposed receiver, a variable optical attenuator (VOA) is used to adaptively control the SPAD’s incident photon rate according to the instantaneous received optical power so that SPAD operates in its optimal conditions. The application of the proposed receiver in systems with various modulation schemes is investigated. When binary on–off keying (OOK) modulation is employed due to its good power efficiency, two dimming control methods of the IEEE 802.15.7 standard based on analogue and digital dimming are considered. We also investigate the application of the proposed receiver in the spectral efficient VLC systems with multi-carrier modulation schemes, i.e., direct current (DCO) and asymmetrically clipped optical (ACO) orthogonal frequency division multiplexing (OFDM). Through extensive numerical results, it is demonstrated that the suggested adaptive receiver outperforms the conventional PIN PD and SPAD array receivers in terms of bit error rate (BER) and achievable data rate.

A preliminary exploration of the cross-cultural production, performance and dissemination models of contemporary Chinese adaptations of Shakespeare’s plays (1990-2020)

The cross-cultural performance of Chinese adaptations of Shakespeare’s plays abroad has gone through two stages: the ‘introduction’ of Shakespeare’s plays and the ‘going out’ of Chinese adaptations of Shakespeare’s plays. The paper aims to analyse the correlation between the two stages. By analysing the process of initiation, dissemination and reception of Chinese adaptations of Shakespeare’s plays [see Table 1], which have been invited to perform abroad for many times and have attracted a certain level of response from Western society, the paper attempts to build a network model for the performance and dissemination of Chinese cross-cultural theatre works carrying traditional Chinese culture in the West.

CONSIDERATION OF MULTIPATH IN MODELING THE FIELD OF SECONDARY ELECTROMAGNETIC RADIATION ON INFORMATIZATION OBJECTS

The paper considers the features of the formation of the resulting field of spurious electromagnetic radiation at informatization objects, taking into account the multipath propagation of radio waves, evaluates the achievable error values for determining the attenuation coefficient using known methods for determining the attenuation of the field of spurious electromagnetic radiation based on a deterministic model of radio wave propagation inside the building. The need for a significant refinement of the method for determining the attenuation coefficient is shown, since, in a known form, it is suitable only for measurements in free space and gives very significant errors in urban conditions and inside buildings, or the use of adaptive reception methods when receiving signals (for example, diversity reception), which allows to significantly reduce the level of interference dips in the resulting electromotive force.

Design and Validation of Lifetime Extension Low Latency MAC Protocol (LELLMAC) for Wireless Sensor Networks Using a Hybrid Algorithm

As the battery-operated power source of wireless sensor networks, energy consumption is a major concern. The medium-access protocol design solves the energy usage of sensor nodes while transmitting and receiving data, thereby improving the sensor network’s lifetime. The suggested work employs a hybrid algorithm to improve the energy efficiency of sensor networks with nodes that are regularly placed. Every node in this protocol has three operating modes, which are sleep mode, receive mode, and send mode. Every node enters a periodic sleep state in order to conserve energy, and after waking up, it waits for communication. During the sleep mode, the nodes turn off their radios in order to reduce the amount of energy they consume while not in use. As an added feature, this article offers a channel access mechanism in which the sensors can send data based on the Logical Link Decision (LLD) algorithm and receive data based on the adaptive reception method. It is meant to select acceptable intermediary nodes in order to identify the path from the source to the destination and to minimize data transmission delays among the nodes in the network scenario. Aside from that, both simulation and analytical findings are used to examine the activity of the suggested MAC, and the created models are evaluated depending on their performance. With regard to energy consumption, latency, throughput, and power efficiency, the result demonstrates that the suggested MAC protocol outperforms the corresponding set of rules. The extensive simulation and analytical analysis showed that the energy consumption of the proposed LELLMAC protocol is reduced by 22% and 76.9% the end-to-end latency is 84.7% and 87.4% percent shorter, and the throughput is 60.3% and 70.5% higher than the existing techniques when the number of node is 10 and 100 respectively.

The method of adaptive signal reception with adaptive antenna arrays from moving sources

Spatial signal processing in adaptive antenna arrays should provide optimal signal reception from some desired source, this requires maximizing the signal-to-noise ratio at the output of adaptive antenna arrays. This task is well studied for the case when the signal source is fixed and point, and for mobile objects often have to use complex algorithms for controlling adaptive antenna arrays. The relevance of this study is that one of the most promising approaches to solving the problem is to increase the efficiency of signal reception is the use of adaptive antenna arrays and appropriate methods of spatial signal processing.The angular dispersion of the signal is assumed to be due to its multipath propagation in the communication channel. The configuration of adaptive antenna arrays is assumed to be arbitrary. This method allows to reduce the amount of calculations compared to the method when the weight vector with adaptive antenna arrays is optimal and is selected as the eigenvector of the signal correlation matrix and it is possible to maintain the efficiency of the signal is quite high, which determines its novelty.The article analyzes the method of adaptive reception of signals from moving sources using adaptive antenna arrays which is also called the method of quasi-optimal signal processing received by adaptive antenna arrays from a moving source with unknown angular coordinates, the possibility of its reception by mobile subscribers in angular variance. quasi-optimal signal processing with other known methods of signal processing.

Separating arbitrary free-space beams with an integrated photonic processor

Free-space optics naturally offers multiple-channel communications and sensing exploitable in many applications. The different optical beams will, however, generally be overlapping at the receiver, and, especially with atmospheric turbulence or other scattering or aberrations, the arriving beam shapes may not even be known in advance. We show that such beams can be still separated in the optical domain, and simultaneously detected with negligible cross-talk, even if they share the same wavelength and polarization, and even with unknown arriving beam shapes. The kernel of the adaptive multibeam receiver presented in this work is a programmable integrated photonic processor that is coupled to free-space beams through a two-dimensional array of optical antennas. We demonstrate separation of beam pairs arriving from different directions, with overlapping spatial modes in the same direction, and even with mixing between the beams deliberately added in the path. With the circuit’s optical bandwidth of more than 40 nm, this approach offers an enabling technology for the evolution of FSO from single-beam to multibeam space-division multiplexed systems in a perturbed environment, which has been a game-changing transition in fiber-optic systems.

Statistical synthesis of aerospace radars structure with optimal spatio-temporal signal processing, extended observation area and high spatial resolution

Using the statistical theory of optimization of radio engineering systems the optimal method of coherent radar imaging of surfaces in airborne synthetic aperture radar with planar antenna arrays is developed. This method summarizes several modes of terrain observation and it is fully consistent with current trends in the development of cognitive radars with the possibilities of radiation pattern restructuring in space and adaptive reception of reflected signals. Possible modifications of the obtained optimal method for the operation of high-precision airborne radars with a wide swath are presented. The idea is to create a theoretical basis and lay the foundations for its practical application in solving a wide range of issues of statistical optimization of methods and algorithms for optimal spatiotemporal signal processing in cognitive radar systems for the formation of both high-precision and global radar images. To implement the idea, the article highlights the concept of statistical optimization of spatio-temporal processing of electromagnetic fields in on-board cognitive radar systems, which will be based on the synthesis and analysis of methods, algorithms and structures of radar devices for coherent imaging, the study of limiting errors in restoring the spatial distribution of the complex scattering coefficient, the synthesis of optimal feedback for receiver and transmitter adaptations in accordance with a priori information about the parameters of the objects of study, the area of observation and the existing sources of interference. Objective is to develop the theory and fundamentals of the technical implementation of airborne radar systems for the formation of high-precision radar images in an extended field of view from aerospace carriers. Tasks. To reach the objective it is necessary to solve following tasks:– formalize mathematical models of spatiotemporal stochastic radio signals and develop likelihood functional for observation equations in which the useful signal, receiver internal noise and interference radiation of anthropogenic objects are random processes;– to synthesize algorithms for optimal processing of spatio-temporal stochastic signals in multi-channel radar systems located on aerospace-based mobile platforms;- in accordance with the synthesized methods, to substantiate the block diagrams of their implementation;– obtain analytical expressions for the potential characteristics of the quality of radar imaging and determine the class of probing signals and space scanning methods necessary to perform various tasks of radar surveillance;‒ to confirm some of the theoretical results by simulation methods, in which to reveal the features of the technical implementation of aerospace remote sensing radar systems.

Seria powieści Erla Stanleya Gardnera o Perrym Masonie i ich ekranizacje: recepcja przez współczesnych odbiorców polsko- i anglojęzycznych

This paper offers an overview of the reception of Erle Stanley Gardner’s series of novels about lawyer Perry Mason and the numerous film adaptations based on that series. It seeks to analyze their reception by contemporary Polish- and English-speaking readers and viewers. Accordingly, the statistics of readership and viewership of books, films and series based on the novels by Gardner are presented and discussed. The article is divided into five sections that deal with the following: Gardner as author; Gardner’s contribution to the development of serialized novel; editions of Gardner’s Perry Mason novels in the United States and in Poland; reception of Gardner’s Perry Mason novel series by Polish- and English-speaking readers, and reception of TV and film adaptations of these novels.

METHOD DETERMINATION OF THE SENSORS CONTROL OF CONDITION TRACK SECTION WITH AN ADAPTIVE RECEIVER

The article presents one of the most promising methods for detecting a moving unit by a sensor for monitoring the condition of track sections, namely, rail circuits with an adaptive receiver. The scheme for realizing control sections using a computer is presented.

Mathematical model of the sensor for controling the condition of the track section with an adaptive receiver at the free condition of the controlled section

One of the promising areas of improvement of sensors for monitoring the condition of track sections is the development of controlling sensors, which are less dependent on changes in ballast resistance, longitudinal asymmetry and standard value of shunt sensitivity, such a direction is the development of adaptive track circuits [1-5]. The article proposes a control sensor with an adaptive receiver, principle of operation of which is that monitoring the state of the track section depends on the parameters of adjacent monitoring sensors, included in the common controlled zone CZ.Mathematical model and analytical expressions have been developed taking into account the resistance of the rails and the resistance of the insulation being carried out [6]. Proposed the coefficients of a rail fourpole with one of the choke-transformer, powered with one side. The calculated expressions of the fourpole and the criteria for the sensitivity of the rail circuit when one line is broken are presented and derived, and also the minimum transmission resistance [6].

Adaptive Receiver Control for Reliable High-Speed Underwater Wireless Optical Communication With Photomultiplier Tube Receiver

Photomultiplier tube (PMT) receiver is a promising solution for long-distance underwater wireless optical communication (UWOC) due to its characteristics of high gain, low noise, and large receiver area. However, the complex underwater environment leads to the dynamic change of the received optical intensity and impacts the stability and reliability of UWOC system using PMT. In this work, the bandwidth limitation and performance degradation of UWOC system caused by PMT saturation is experimentally observed and characterized for various optical intensity and PMT gain. A low-cost, high-integrated, and small-volume receiver control system and relevant adaptive control strategy are proposed to improve the stability and reliability of UWOC system by dynamically adjusting the received optical power and PMT gain according to the detected optical signal. The experiment results show that the dynamic range of UWOC received optical power can be extended to 68 dB (-63 dBm~5 dBm) for 100 Mbit/s OOK modulation based UWOC system.

A Rail line model with distributed parameters of track circuit

Models of continuous jointlesstrack circuits with an adaptive receiver are presented, where the power supply is connected to the beginning or middle of the rail circuit, and also to the locomotive receiver. The aim of the work is to develop models of rail lines, which take into account the actual current distribution along the track line and which may be used to research adaptive jointlesstrack circuits. The electric schemes of the jointlesstrack circuits are given, equations, connecting currents and voltages at the ends of the rail line, coefficient of four-pole rail lines, algorithms for calculating track circuits. In conclusion, that the track circuit can operate at an insulation resistance four times lower than the permissible value, where the permissible insulation resistance is Ri = 1om*km. New approaches and tools for analyzing and synthesizing solutions are considered, with considering account real operating conditions and disturbing factors.