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This paper proposes and successfully demonstrates a high-speed optical signal coupling (HS-OSC) of 2x40Gbaud PAM8 with precoder-shaped multi-level polar codes (PS-MLPC) in a gain-oriented multiple-input single-output free space optical (MISO-FSO) system. With the pilot-based correction (PBC), the system gets a multi-path error (MPE) detecting and correcting module, which can minimize the MPE and achieve the gain-oriented HS-OSC. On the other hand, PS-MLPC is deployed in the MISO-FSO system to provide the non-uniform PAM-8 symbols and save the power budget. In the experiment, the PBC module is proven to ensure the HS-OSC process by comparing the captured waveforms. Results in the static FSO channel validate that the bit error rate (BER) of the MISO-FSO system is improved from 4.76 × 10 - 3 to below 10 - 5 and the PS-MLPC PAM-8 saves most 0.85 dB effective signal-to-noise ratio (ESNR). Under turbulent conditions, the gain-oriented MISO-FSO system not only enhances the mean ESNR of about 4.3–5.4 dB but also mitigates the standard deviation of ESNR by 40.6–61.4 %, on which the PS-MLPC provides a Q-factor gain of 1.17–1.64 dB. [ABSTRACT FROM AUTHOR]

The use of a static modulation coding scheme (MCS), such as 7, and resource keep probability ( P r k ) value, such as 0.8, was proven to be insufficient to achieve the best packet reception ratio (PRR) performance. Various adaptation techniques have been used in the following years. This work introduces a novel optimization algorithm approach called the fuzzy inference reinforcement learning (FIRL) sequence for adaptive parameter configuration in cellular vehicle-to-everything (C-V2X) mode-4 communication networks. This innovative method combines a Sugeno-type fuzzy inference system (FIS) control system with a Q-learning reinforcement learning algorithm to optimize the PRR as the key metric for overall network performance. The FIRL sequence generates adaptive configuration parameters for P r k and MCS index values each time the Long-Term Evolution (LTE) packet is generated. Simulation results demonstrate the effectiveness of this optimization algorithm approach, achieving up to a 169.83% improvement in performance compared to static baseline parameters. [ABSTRACT FROM AUTHOR]

We investigate the peak-power limited (PPL) Additive White Gaussian Noise (AWGN) channels in which the signal is band-limited, and its instantaneous power cannot exceed the power P. This model is relevant to many communication systems; however, its capacity is still unknown. We use a new geometry-based approach which evaluates the maximal entropy of the transmitted signal by assessing the volume of the body, in the space of Nyquist-rate samples, comprising all the points the transmitted signal can reach. This leads to lower bounds on capacity which are tight at high Signal to Noise Ratios (SNRs). We find lower bounds on capacity, expressed as power efficiency, that were higher than the known ones by a factor of 3.3 and 8.6 in the low-pass and the band-pass cases, respectively. The gap to the upper bounds is reduced to a power ratio of 1.5. The new bounds are numerically evaluated for FDMA-style signals with limited duration and also are derived in the general case as a conjecture. The penalty in power efficiency due to the peak power constraint is roughly 6 dB at high SNRs. Further research is needed to develop effective modulation and coding for this channel. [ABSTRACT FROM AUTHOR]

IEEE 802.11ah, primarily developed for Internet of things (IoT) applications. A restricted access window (RAW) mechanism is employed for channel access to minimize contention among the nodes in dense IoT networks. Here, we present an analytical model for IEEE 802.11ah RAW mechanism with unsaturated conditions. In IEEE 802.11ah, determination of optimal number of RAW slots/groups affects the network performance. Thus, choosing the optimal number of RAW slots according to network size, RAW duration and modulation coding scheme (MCS) can improve the performance of IEEE 802.11ah network. Recently, deep learning (DL) becomes a thriving field for communication and networking applications. In this research work, we propose a long short-term memory (LSTM) based DL-recurrent neural network (DL-RNN) to predict the optimal RAW slots. Using genetic algorithm, we obtain optimal RAW slots from the presented analytical model with unsaturated conditions for the IEEE 802.11ah IoT network. Further, the dataset with optimal number of RAW slots for each of the combinations (network sizes, RAW durations and MCSs) is used for training the LSTM based DL-RNN. Based on the optimal RAW slots, throughput and energy efficiency (EE) are computed for IEEE 802.11ah network. From results, we notice that optimal RAW slots generated by LSTM based DL-RNN model significantly improve throughput and EE of IEEE 802.11ah network comparison to existed machine learning and Fuzzy optimization techniques. [ABSTRACT FROM AUTHOR]

In this paper, a novel radar jamming method based on random phase modulation of digital coding metasurface was proposed. For typical radar system, the modulation model of coding metasurface and the echo model are deduced firstly. Then, the ordered statistics greatest of the constant false alarm rate (OSGO-CFAR) detection model was chosen to analyze the radar detection performance. Through serials of simulation, the influence of modulation modes, modulation switching interval, the number of coding elements and the signal-to-noise ratio (SNR) on radar detection performance is analyzed. Finally, the Monte Carlo simulation is performed. The result shows that as the modulation switching interval of metasurface decreases, the spectrum energy distribution of the target becomes more dispersed and the detection probability of the target decreases obviously. Traditional radar detectors will become ineffective, and the shielding of the target will be achieved. This implies a new radar jamming method which can realize target shielding instead of traditional stealth by reducing the radar cross section. [ABSTRACT FROM AUTHOR]

Compared with the amplitude modulation of conventional interrupted sampling repeater jamming (ISRJ), the image feature control method based on phase modulation exhibits greater energy efficiency and, therefore, has received wide attention recently. In this paper, an Inverse Synthetic Aperture Radar (ISAR) image feature suppression method based on arbitrary phase encoding (APE) is proposed. The parameter design criterion is further analyzed. Through the nonperiodic segmented coding and modulation of the imaging signal in fast and slow time domains, the modulated signal produces a two-dimensional suppression region with uniform energy distribution in the ISAR image. Simulations via the measured Yak-42 aircraft data have verified the effectiveness of the proposed method for target feature control. Compared to binary phase modulation jamming, the APE method with a phase modulation accuracy of 1 degree can achieve the same jamming effect while reducing the jamming power requirement by 3 dB. By optimizing with the proposed method, the image entropy of the interfered image increases by 1.1 to 1.5 compared to the original image. [ABSTRACT FROM AUTHOR]

The active materials-loaded reconfigurable metasurface is a potential platform for terahertz (THz) communication systems. However, the requirements of the modulation performance and the modulation rate put forward the opposite requirements on the excited conductivity of active materials. In this paper, we proposed a concept for a metal-doped active material switch that can produce an equivalent high excited conductivity while reducing the required threshold of the active material conductivity, thus balancing the conflict between the two mutual requirements. Based on it, we designed a reconfigurable electromagnetically induced transparency (EIT) metasurface driven by a low excited conductivity of vanadium dioxide  VO 2 , which can achieve the amplitude modulation and amplitude coding under the control of light and electric. Simulation results validate the role of the metal-doped  VO 2  switch on the metasurface. This work provides a new scheme to mediate the contradiction between the modulation performance and the modulation rate in the requirement of active material's excited conductivity, which facilitates the development of new terahertz modulators based on reconfigurable metasurfaces. In addition, the concept of a metal-doped active material switch will also provide a solution to the limitations of active material from the design layer. [ABSTRACT FROM AUTHOR]

The peak-to-average power ratio (PAPR), commonly used to describe the amplitude variations of an OFDM (orthogonal frequency-division multiplex) signal, does not accurately reflect its impact on the system performance. This paper applies the mutual information as a metric to assess the effects of nonlinear PAPR reduction schemes on the performance of OFDM systems. Evaluation of the achieved mutual information shows that a significant capacity loss from clipping occurs only at high SNR (signal-to-noise ratio) and a simple compression/expansion technique is proposed to achieve close to optimal performance in this regime. The effectiveness of this method is validated through WER (word error rate) simulations with several modulation and coding schemes. [ABSTRACT FROM AUTHOR]

This study has demonstrated the efficient employment of optical DPSK transmitter with linear multimode fibers and FSO channel under various duty cycle coding effects. The light signal power form variations after linear multimode fiber versus spectral wavelength based various RZ-percentage duty cycle coding is clarified. The light signal power form variations after linear multimode fiber versus spectral wavelength based various NRZ duty cycle coding is also clarified. The light power signal form variations after FSO channel versus spectral wavelength based different RZ percentage duty cycle coding is analyzed. Moreover the light power signal form variations after FSO channel versus spectral wavelength based NRZ percentage duty cycle coding is investigated. The light signal power form variations after linear multimode fiber versus spectral wavelength based various RZ percentage duty cycle coding and NRZ modulation code are indicated. [ABSTRACT FROM AUTHOR]

The rapid developments of 5G and B5G networks have posed higher demands on retransmission in certain scenarios. This article reviews classical finite-length coding performance prediction formulas and proposes rate prediction formulas for coded modulation retransmission scenarios. Specifically, we demonstrate that a recently proposed model for correcting these prediction formulas also exhibits high accuracy in coded modulation retransmissions. To enhance the generality of this model, we introduce a range variable P final to unify the predictions with different SNRs. Finally, based on simulation results, the article puts forth recommendations specific to retransmission with a high spectral efficiency. [ABSTRACT FROM AUTHOR]

The integration of information and communication technologies in the field of healthcare has generated a positive transformation in the traditional way of providing patient care, optimizing medical services, and streamlining healthcare operations. Traditionally, healthcare systems have relied on radio frequency (RF) signals for data transmission. However, the conventional RF wireless network faces ever-increasing challenges, such as spectrum shortage and a congested frequency spectrum. Moreover, issues such as interference, security vulnerabilities, and potential health risks associated with prolonged exposure to RF electromagnetic radiation complicate its application in healthcare environments. To address these challenges, visible light communication (VLC) systems, which offer dual functionalities, data transmission, and illumination, have emerged as a promising complementary solution to traditional RF-based options. VLC provides secure, high-speed data communication that is immune to RF interference, making it particularly suitable for healthcare settings. This research examines the advancements in e-health systems that utilize VLC technology, considering various modulation and channel coding techniques, with a focus on evaluating the effectiveness and limitations of these techniques to determine their impact on overall performance. [ABSTRACT FROM AUTHOR]

In response to the challenge of existing wireless communication anti-jamming methods in effectively handling unknown jamming, this paper proposes a multi-parameter control anti-jamming algorithm for wireless communication systems based on the Linear–Quadratic Regulator (LQR). First, the proposed algorithm models the wireless communication system as a linear switched system based on the modulation and coding scheme. Subsequently, a feedback controller design method based on the LQR is introduced. By utilizing the multiple Lyapunov function method combined with linear matrix inequalities, sufficient criteria for the asymptotic stability of the system under unknown jamming conditions are provided. Finally, theoretical analysis and simulation results indicate that the proposed algorithm can rapidly adjust modulation and coding schemes as well as transmission power in complex jamming environments, thereby maintaining bit error rate (BER) stability and enhancing the reliability of the communication system. [ABSTRACT FROM AUTHOR]

We study a most recent mechanism for reserving channel resources to deliver high-priority traffic in Wi-Fi networks, Restricted Target Wake Time (R-TWT). We develop an analytical model of a Wi-Fi network using the R-TWT mechanism, which allows us to estimate the throughput of users transmitting low-priority traffic, depending on the R-TWT reservation period, restrictions on the size of transmitted frames and modulation and coding schemes used. The model shows that the dependence of the user throughput on the R-TWT period is not monotonic, and a slight increase in the R-TWT period can lead to both an increase and a significant drop in the user throughput. [ABSTRACT FROM AUTHOR]

Short block length "block" codes are typically not used in wireless standards as soft decision decoding is computationally intensive and hard decision decoding results in performance loss. However, short block lengths are of interest to massive machine-type communications (mMTC) and ultra-reliable low-latency communications (URLLC). In this paper, we propose a diversity preserving enhanced hard-decision decoding scheme for parity check codes (PCC) over Rayleigh fading channels. The proposed flip decoding scheme has linear complexity in the block length. Theoretical analysis and simulation results verify the correctness of the proposed detection scheme. [ABSTRACT FROM AUTHOR]

The mammalian retina is considered an autonomous circuit, yet work dating back to Ramon y Cajal indicates that it receives inputs from the brain. How such inputs affect retinal processing has remained unknown. We confirmed brain-to-retina projections of histaminergic neurons from the mouse hypothalamus. Histamine application ex vivo altered the activity of various retinal ganglion cells (RGCs), including direction-selective RGCs that gained responses to high motion velocities. These results were reproduced in vivo with optic tract recordings where histaminergic retinopetal axons were activated chemogenetically. Such changes could improve vision of fast-moving objects (e.g., while running), which fits with the known increased activity of histaminergic neurons during arousal. An antihistamine drug reduced optomotor responses to high-speed moving stimuli in freely moving mice. In humans, the same antihistamine nonuniformly modulated visual sensitivity across the visual field, indicating an evolutionary conserved function of the histaminergic system. Our findings expose a previously unappreciated role for brain-to-retina projections in modulating retinal function. [ABSTRACT FROM AUTHOR]

To address the challenges posed by the diverse demands of mobile users and vertical industries, it is crucial for 5G-advanced (5G-A) networks to exhibit flexibility in system design across both the physical and higher layers. A single-frame structure alone cannot provide the necessary flexibility to accommodate multiple traffic modes. Therefore, we investigate a heterogeneous frame structure that meets the requirements. However, this structure will cause severe cross-link interference (CLI) and degrade the performance. To solve this problem, four CLI mitigation methods are proposed: slot level adaptive modulation and coding (AMC) scheduling (method 1), interference mitigation algorithm (method 2), adaptive slot turn-off (method 3), and edge user adaptive scheduling (method 4). The experimental results show that the CLI problem can be completely mitigated by deployed method 3 in a macro-base station (BS) with a low load scenario, the micro-BS uplink (UL) throughput was improved by 75.8%. Otherwise, with macro-BS in the high load scenario, when method 4 was implemented in macro-BS and methods 1 and 2 were deployed in micro-BS, a nearly complete CLI mitigation effect was obtained, reflecting that the micro-BS UL throughput increased to 57.4%. These methods are elaborated upon and evaluated within practical 5G-A networks, and the experimental results not only demonstrate the viability and efficacy of the above methods but also highlight their potential applications in future usage scenarios. [ABSTRACT FROM AUTHOR]

Waveform design for integrated radar and jamming is generally based on the concept of shared waveform, which uses jamming signals without typical radar signal characteristics for detection. Existing waveforms have shown limited design flexibility, high levels of sidelobe in detection results, and overall ordinary performance. We propose an integrated radar and jamming waveform based on smart modulation and complementary coding. Unlike traditional integrated radar and jamming waveform based on smart modulation, the phase angle of the binary phase-coded sequence is adjustable in this smart modulation method, allowing for a controllable jamming effect, achieving true smart modulation. However, this smart modulation waveform also suffers from high sidelobes in detection. To address this issue, we take a complementary coding approach and design a smart modulation waveform with complementary characteristics. This waveform can synthesize a complete linear frequency modulation (LFM) signal by adding two pulses together, thereby reducing the sidelobes in the smart modulation waveform and enhancing its detection performance. Theoretical analysis indicates that the detection and jamming effects of this integrated waveform can be flexibly controlled by adjusting the phase angles of the coding sequences. Simulation analysis and experimental results confirm the significant advantages of this waveform. [ABSTRACT FROM AUTHOR]

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5G NR is a wireless mobile communication system that supports ultra-high speed mobile communications, high reliability services, and large-scale Internet of Things. In a mobile communication environment, the Doppler effect, which is proportional to the speed of travel, causes channel changes over time, which can lead to communication performance degradation. In order to achieve optimal communication performance in a mobile communication environment, it is necessary to predict the Signal to Noise Ratio (SNR) between the base station and the terminal and select and transmit the most appropriate Modulation and Coding Scheme (MCS) accordingly. In this paper, we propose a method for selecting the MCS level of a single antenna based on Convolutional Neural Network (CNN) in 5G NR mobile communication systems. The proposed system assumes a time division duplex (TDD) scheme, measures the SNR at the time of reception, predicts the SNR at the time of future transmission using CNN based on the measured past channel information, and selects the MCS level based on the predicted SNR. Experimental results through computer simulation show that the proposed CNN-based MCS selection method has a lower probability of communication disconnection and higher transmission rate at all speeds compared to the existing average value method based on the average of SNR and the recent value method based on the most recently received SNR. In particular, the transmission speed of the proposed method is about 46% and 4.6% better than the existing average value method and recent value method, respectively, and can be utilized as a technology to increase the transmission speed in 5G mobile communication environment. [ABSTRACT FROM AUTHOR]

In this paper, a subset-optimized eight-dimensional trellis-coded quadrature amplitude modulation (SO-8DTCM-16QAM) format for higher-order constellations in high-speed optical communications is proposed. This scheme increases the number of subsets of base 2D constellation divisions. On this basis, it is further optimized by using 2D subsets for Cartesian product combinations to obtain 4D subsets and eliminate the combinations with small Euclidean distances. Finally, the 4D subsets are utilized to construct interrelated 8D subsets for trellis coding modulation and signal transmission. The proposed scheme can effectively reduce the decoding complexity and outperforms the conventional scheme at a high signal-to-noise ratio (SNR). Simulation verification of the proposed scheme is carried out, and the results show that the SO-8DTCM-16QAM achieves signal-to-noise ratio (SNR) gains of 1.60 dB, 1.56 dB, 1.51 dB, and 1.33 dB, respectively, compared with the conventional 8D-16QAM signals when BTB and 5/20/30 km optical signal transmission are performed. The SO-8DTCM-16QAM also achieves an SNR gain of 1.86 dB, 1.75 dB, and 1.22 dB at a net transmission rate of 14/21/28 GBaud. In addition, the SO-8DTCM-16/32/64QAM achieves an SNR gain of 1.27 dB, 0.80 dB, and 1.24 dB, respectively, when compared with the unoptimized 8DTCM-16/32/64QAM. Meanwhile, the proposed eight-subset SO-8DTCM-QAM scheme reduces the complexity of the decoding computation in the subset selection part and the constellation point selection part by 93.75% and 50%, respectively, compared with the unoptimized eight-subset and four-subset 8DTCM-QAM schemes. It can be seen that the proposed scheme simultaneously optimizes the transmission performance and complexity of high-speed optical communication systems and has practical application value. [ABSTRACT FROM AUTHOR]

Flying base stations, also known as aerial base stations, provide wireless connectivity to the user and utilize their aerial mobility to improve communication performance. Flying base stations depend on traditional stationary terrestrial base stations for connectivity, as stationary base stations act as the gateway to the backhaul/cloud via a wired connection. We introduce the flying base station channel capacity to build on the Shannon channel capacity, which quantifies the upper-bound limit of the rate at which information can be reliably transmitted using the communication channel regardless of the modulation and coding techniques used. The flying base station's channel capacity assumes aerial mobility and ideal positioning for maximum channel capacity. Therefore, the channel capacity limit holds for any digital and signal processing technique used and for any location or positioning of the flying base station. Because of its inherent reliance on the stationary terrestrial base station, the flying base station channel capacity depends on the stationary base station's parameters, such as its location and SNR performance to the user, in contrast to previous research, which focused on the link between the user and the flying base station without the stationary base station. For example, the beneficial region (where there is a positive flying base station capacity gain) depends on the stationary base station's power and channel SNR in addition to the flying base station's own transmission power and whether it has full duplex vs. half-duplex capability. We jointly study the mobility and the wireless communications of the flying base station to analyze its position, channel capacity, and beneficialness over the stationary terrestrial base station (capacity gain). As communication protocols and implementations for flying base stations undergo development for next-generation wireless networking, we focus on information-theoretical analyses and channel capacity to inform future research and development in flying base station networking. [ABSTRACT FROM AUTHOR]

In this paper, a novel data transmission scheme, interference perceptual multi-modulation (IP-MM), is proposed for full-duplex (FD) systems. In order to unlink the conventional uplink (UL) data transmission using a single modulation and coding scheme (MCS) over the entire assigned UL bandwidth, IP-MM enables the transmission of UL data channels based on multiple MCS levels, where a different MCS level is applied to each subband of UL transmission. In IP-MM, a deep convolutional neural network is used for MCS-level prediction for each UL subband by estimating the potential residual self-interference (SI) according to the downlink (DL) resource allocation pattern. In addition, a subband-based UL transmission procedure is introduced from a specification point of view to enable IP-MM-based UL transmission. The benefits of IP-MM are verified using simulations, and it is observed that IP-MM achieves approximately 20 % throughput gain compared to the conventional UL transmission scheme. [ABSTRACT FROM AUTHOR]

In recent years the increase of mobile devices and users of the internet has led to an increase in the burden on the network, low connectivity, low bandwidth, and less throughput. With many advantages of the 5G cellular network, this network suffers from signal interference which causes a massive problem for the network. There are many challenges in the cellular network related to energy consumption, and one of the leading and critical issues in 5G is interference management. There is poor voice quality during indoor communication, so interference management provides Quality of Service (QoS) to improve this communication. In indoor communication, there is low power compared to outdoor communication because there are many users, and due to users, there are low data rates and overhead on the base station. From this viewpoint, modulation schema and coding schemes achieve better channel conditions, a significant convergence area, and better QoS. This research proposes a scheme named multiple input multiple output (MIMO) technology for interference management in a 5G network. The evaluation of this scheme with a relay strategy has also been carried out to avoid interference and enhance the strength of the propagated signal. The simulation has revealed the performance of the proposed interference management scheme with a relay strategy based on performance evaluation parameters such as end-to-end delay, throughput, path loss, and energy consumption. [ABSTRACT FROM AUTHOR]

We study the High Throughput Modulation and Coding Schemes (HT-MCS) in IEEE 802.11n In networks in this paper. The HT-MCSs are designed to deal with various channel conditions in the networks. We used ns-3 simulations to study HT-MCS 0 to HT-MCS 31 under various radio propagation models. The simulation results are presented in this paper. In our simulations the HT-MCSs were tested in networks with Friis, Nakagami, and log-distance propagation models for studying their performance under various signal attenuation and fading effects. The HT-MCSs provided consistent performance under most channel conditions in our simulations. However, they showed significantly degraded performance under the log-distance propagation model when the communication distance was relatively long because of the high signal attenuation in such a case. Our simulations also showed that an increased number of radio beams increased the ability of the modulation and coding schemes in combating adverse channel conditions. [ABSTRACT FROM AUTHOR]

Overlapped Time Domain Multiplexing (OvTDM) is a high-rate transmission technology that employs the idea of superposition coded modulation (SCM) scheme for signal generation, aiming to achieve maximum channel capacity sharing. Meanwhile, it is also widely considered as a promising technique toward physical layer security. As a main drawback of such system, a high peak-to-average power ratio (PAPR) issue in this system, arising from multi-layer superposition, can be addressed through intentional clipping. However, the detection at the receiver side is vulnerable to nonlinear distortion caused by clipping, which can degrade the performance. To mitigate this distortion, this paper proposed an iterative scheme for estimating and partially canceling clipping distortion at the receiver. We managed to mitigate the impact of clipping noise as much as possible and minimize the cost of optimizing PAPR, thereby improving the transmission performance of OvTDM in the context of amplitude clipping. [ABSTRACT FROM AUTHOR]

With the rapid deployment of intelligent transportation systems in real-life applications, both dedicated short-range communications (DSRC) and cellular Vehicle-to-Everything (C-V2X), utilized to enable V2X communication, are undergoing extensive development to meet the quality of service (QoS) demands of advanced vehicular applications and scenarios. Compared to C-V2X, which lacks fully validated effective reliability, DSRC has undergone extensive field testing worldwide, ensuring its practicality. IEEE 802.11bd, as the next-generation V2X (NGV) standard within DSRC, is expected to greatly exceed the performance of its predecessor, 802.11p. However, existing studies mention that the ambient traffic environment will influence the performance of V2X due to the cyber-physical properties of V2X. To fully assess the advancements of NGV, this study presents a comparative analysis of IEEE 802.11bd and IEEE 802.11p, focusing on dynamic traffic conditions. Specifically, the technical advancements of the IEEE 802.11bd standard are first theoretically examined, emphasizing significant enhancements in aspects like modulation and coding schemes, coding rates, and channel coding. Subsequently, these critical technical enhancements are implemented in Veins, a simulation framework for the Internet of Vehicles (IoV), encompassing large-scale dynamic traffic scenarios. The simulation results indicate that the IEEE 802.11bd standard significantly enhances the data transfer rate compared to IEEE 802.11p, achieving a stable twofold increase. Furthermore, the data transmission latency is reduced by over half compared to IEEE 802.11p, while the data transmission reliability experiences a noteworthy 20% enhancement. Notably, the enhanced data transmission mode of the IEEE 802.11bd standard requires an increased signal-to-noise ratio (SNR). Additionally, this research evaluates the data dissemination properties in the IoV and finds that the traffic volume has a limited impact on the data propagation speed. [ABSTRACT FROM AUTHOR]

Concentrating on the joint recognition problem of modulation and space–time coding, algorithm for blind identification of modulation and space–time coding based upon fourth-order cyclic cumulant and feature parameter extraction in correlation matrix is proposed in this paper. The algorithm first uses the fourth-order cyclic cumulant to identify different modulation modes (4PSK, 8PSK, 16QAM, 32QAM, 64QAM). Different space–time block codes (Alamouti, OSTBC3, OSTBC4, NOSTBC2, and NOSTBC4) are identified by extracting feature parameters in the correlation matrix. The five recognized modulation modes and five space–time codes are sent to convolutional neural network, then 25 combination modes of modulation and space–time coding are recognized by using the Dropout layer, Gaussian noise layer, Flatten layer, dense layer, and fully connected layer successively by applying the Softmax activation function. The research results indicate that the emanated algorithm may effectively identify 5 modulation modes and 5 space–time codes, and can identify 25 combination modes of modulation and space–time coding. Under the condition that SNR is greater than or equal to 0 dB, the joint recognition rate of modulation and space–time coding can reach 100%. [ABSTRACT FROM AUTHOR]

Reducing the distance between magnetic islands is essential for increasing the areal density in bit-patterned media recording (BPMR). Consequently, significant two-dimensional (2D) interference emerges, encompassing inter-symbol interference (ISI) and inter-track interference (ITI) along the cross- and down-tracks, respectively. To address the 2D interference, modulation with non-isolated patterns can be employed to mitigate the interference from neighboring bits. In previous studies, authors relied on the Hamming code to propose a non-isolated modulation code with a minimum Hamming distance (MHD) of 3. However, for encoding, authors utilized a mapping method with a large look-up table, resulting in prolonged delay for the decoder. Therefore, in this paper, we proposed a generator matrix for creating the Hamming code with an MHD of 3, thereby generating reverse codewords in the look-up table. Consequently, only half of the look-up table needs to be stored, leading to reduced complexity and delay time in the decoder for non-isolated modulation code with an MHD of 3. Simulation results demonstrate that our proposed model can enhance bit error rate performance and decrease delay time compared to previous studies.

A novel multidimensional index modulation-based differential chaos shift keying (DCSK) technique, designated as Joint Subcarrier Time Reference Index Modulation-aided Differential Chaos Shift Keying (JSTRIM-DCSK), is proposed for efficient data transmission in chaotic communication systems. The JSTRIM-DCSK system integrates subcarrier, time slot, and reference signal indexing to transmit information and offers two variants: JSTRIM-DCSK-I and JSTRIM-DCSK-II. The data is organized into L subblocks, each containing $N_{s}$ subcarrier index bits $p_{s}$ and $N_{t}$ time slot index bits $p_{t}$ , reference index bits $p_{r}$ , and modulated bits $p_{m}$ . The subcarrier and time slot index bits jointly select an active or inactive subcarrier time slot combination from a total of $N_{s}N_{t}$ possibilities, categorizing the system as either JSTRIM-DCSK-I (active) or JSTRIM-DCSK-II (inactive). The reference indexed bits select a single chaotic reference signal from $N_{r}$ orthogonal chaotic vectors generated using the Gram-Schmidt orthogonalization process. The modulated bits are transmitted using a DCSK modulation scheme. Analytical expressions for the bit error rate (BER) performance of the JSTRIM-DCSK system are derived under both additive white Gaussian noise (AWGN) and multipath Rayleigh fading channel (MRFC) conditions. Furthermore, the potential for energy savings, bandwidth efficiency, and system complexity of the JSTRIM-DCSK system are thoroughly analyzed and compared with those of the existing techniques. The simulation results validate the analytical expressions and demonstrate the potential of JSTRIM-DCSK to achieve high data rates, efficient energy savings, and a competitive BER performance.

Spectrum conversion involves the movement of a signal from one frequency to another, and it is well-studied in materials interacting with electromagnetic waves from microwave to optical frequencies. In this paper, a time-modulated active frequency selective surface (AFSS) absorber/reflector is proposed to manipulate the spectral distribution of the echo signal. The discrete harmonics based on the period modulation and the continuous spectrum based on the random coding modulation are analyzed in detail. In addition, a simple digital-coding control network based on field programmable gate array (FPGA) in the time-modulated AFSS absorber/reflector (TMAAR) is used to switch between absorbing and reflecting states flexibly. By coding "0" and "1" elements with the controlled sequences, the TMAAR is able to achieve the predefined modulation function for spectrum conversion. On this basis, a prototype of the designed TMAAR is manufactured. The linear frequency modulation radar echo experiments are performed to verify the required function of spectrum conversion. [ABSTRACT FROM AUTHOR]

This paper discusses an extended modulation mapping technique to improve hybrid automatic repeat request (ARQ) protocols by reducing communication errors in wireless systems. The extended mapping (EM) hybrid ARQ (HARQ) protocol has been developed using irregular repetition code with turbo processing. This protocol uses EM and ARQ to improve efficiency, including retransmission for error correction. The existing hybrid ARQ technique uses a horizontal iterative decoding scheme to reduce error. The suggested method employs both serial and parallel iterative decoding schemes for error detection and correction. A bit error rate (BER) analysis evaluates the proposed model, EM-HARQ performance in the additive white Gaussian noise channel. The results show a significant gain in signal-to-noise ratio (SNR) from the theoretical limit of the irregular repetition coding using MATLAB simulation software. The adoption of EM in the proposed method improves the SNR to a 0.99 dB performance gap difference and 0.3 dB performance gain due to enhanced error detection. Even with low SNR channels, the proposed EM-HARQ system can achieve a low BER and close to the theoretical limit capacity. [ABSTRACT FROM AUTHOR]

The escalating demand for high-density storage of hard disk drives has prompted the innovation of advanced technologies to significantly boost an areal density (AD). Among these, three-dimensional magnetic recording systems incorporating double recording layers and bit-patterned magnetic recording (BPMR) have currently emerged as one promising solution. Therefore, this article investigates the integration of double-layer magnetic recording and BPMR technologies which is called double-layer BPMR, aiming for a substantial increase in AD. The primary focus lies on minimizing inter-layer interference and mitigating two-dimensional interferences by optimizing bit-island sizes for both upper and lower layers under the incorporation of staggered-like recording media arrangement and an array of magneto-resistive readers. Moreover, we also employ a rate-5/6 modulation code for compensating these effects. Detailed examinations reveal that our proposed system has a superior bit-error rate performance compared with conventional single-layer BPMR system. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) is the most emerging radio access scheme for fifth-generation (5G) cellular networks. However, the major drawbacks of present NOMA systems are limited channel feedback and the difficulty of combining them with other advanced adaptive modulation and coding systems. Thus, this paper proposes an optimized NOMA system using a stacked Bi-GRU-based deep learning method for estimating the channel. Initially, the messages are coded by utilizing hybrid polar low-density parity-check (LDPC) code for error-free and efficient coding. The coded messages are then adjusted for frame error rate reduction and data sub-block security using a rate optimization approach, and they are modulated with quadrature amplitude modulation (QAM). Finally, channel estimation is performed using a novel stacked bidirectional Gated recurrent unit (Bi-GRU) technique to manage long-term relationships in information. After transmitting the messages via the estimated channel, decoding is performed by a selective extended segment successive cancellation list (SES-SCL) method on the receiver side. For experimentation, the MATLAB platform is preferred, and the results are evaluated and compared with other existing methods. The comparison analysis demonstrates that the proposed method performs better in terms of outage probability, loss, root mean square error (RMSE), bit rate error (BER), and frame error rate (FER). The obtained findings demonstrate that the proposed mechanism is extremely useful for the NOMA system in providing effective services. [ABSTRACT FROM AUTHOR]

Spectral shaping codes are modulation codes widely used in communication and data storage systems. This research enhances the algorithms employed in constructing spectral shaping codes for hardware implementation. We present a parallel scrambling calculation with a time complexity of O(1). Second, in the minimum accumulated signal power (MASP) module, the sine-cosine accumulation needs to be determined by remainder with time complexity O(n²). We offer reduced MASP computations for short bit-width data, ROMstorage, and addition pipelines. It can remove the remainder operation, reducing accumulated complexity to O(1). In addition, we present a search algorithm to generate segmented lines to replace the square operations in the MASP module. By employing the search algorithm and shift operations, we can reduce the complexity of the square from O(n²) to O(1). The implementation results reveal that the original and proposed MASPs yield nearly identical spectrum nulls. The encoder-decoder of the spectral shaping codes with proposed approaches consumes just 6% of the hardware resources when carried out with a Spartan6 XC6SLX25. [ABSTRACT FROM AUTHOR]

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Summary: Communication systems that simultaneously combine orthogonal (OMA) and nonorthogonal multiple access (NOMA) are currently under research. Such systems are called hybrid and have more flexibility in user multiplexing, which allows for increased system capacity. One of the main focus areas of research in such systems is radio resource scheduling. The existing research works on scheduling approaches are based on the Shannon's formula, which can be used to obtain the limit capacity by ideal modulation and coding schemes (MCS). However, it is more correct to consider scheduling based on the real capacity. To get it, one should consider the performance of real MCSs with finite code length; however, they are very rarely taken into account in NOMA research. The reason is that one of the basic unresolved problems in NOMA is MCS selection for users. To solve it, we have presented a table of joint pairwise MCS combinations with their adaptive selection for NOMA. In this work, we propose a radio resource scheduling approach for the OMA/NOMA system based on real MCSs that uses our own method of joint MCS selection for two NOMA users. By performing the simulation of the proposed scheduling approach, we have obtained both total and user capacity in the OMA/NOMA system, as well as the distribution of traffic among users, demonstrating the execution of the scheduling strategies. [ABSTRACT FROM AUTHOR]

In two papers dated 1928 to 1929 in The Journal of Physiology, Edgar Adrian and Detlev Bronk described recordings from motor nerve and muscle fibres. The recordings from motor nerve fibres required progressive dissection of the nerve until a few fibres remained, from which isolated single fibre activity could be detected. The muscle fibre recordings were performed in humans during voluntary contractions with an intramuscular electrode – the concentric needle electrode – that they describe for the first time in the second paper. They recognised that muscle fibres would respond to each impulse sent by the innervating motor neurone and that therefore muscle fibre recordings provided information on the times of activation of the motor nerve fibres which were as accurate as a direct record from the nerve. These observations and the description of the concentric needle electrode opened the era of motor unit recordings in humans, which have continued for almost a century and have provided a comprehensive view of the neural control of movement at the motor unit level. Despite important advances in technology, many of the principles of motor unit behaviour that would be investigated in the subsequent decades were canvassed in the two papers by Adrian and Bronk. For example, they described the concomitant motor neurones' recruitment and rate coding for force modulation, synchronisation of motor unit discharges, and the dependence of discharge rate on motor unit recruitment threshold. Here, we summarise their observations and discuss the impact of their work. We highlight the advent of the concentric needle, and its subsequent influence on motor control research. [ABSTRACT FROM AUTHOR]

Labeling-Based Recipient Identification (LABRID) brings the possibility of representing the destination station address in a Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) system by a signal labeling rule. Low-order modulations, such as BPSK or QPSK, pose a general problem for BICM-ID due to a limited convergence of iterative decoding. In the context of LABRID, they have one more drawback—a small number of different labeling rules in general; the number of the optimal ones, which exhibit the maximal asymptotic coding gain, is reduced even further. Meanwhile, LABRID needs a sizable collection of different optimal labeling rules to serve many users in large wireless networks. In this paper, the author suggests the use of hypercube BPSK or QPSK labeling to overcome all these challenges. By means of the Reactive Tabu Search (RTS) algorithm, more than 1500 equivalent optimal hypercube labeling rules are found. Analytical error bounds of the system are developed and supported by simulation experiments. Then, the focus is moved to the criterion to determine the frame destination at the LABRID receiver; a simple threshold-based method is proposed to keep the incorrect decision probability below 10 − 5 . Finally, it is shown that LABRID outperforms a reference BICM-ID system in terms of computational complexity. [ABSTRACT FROM AUTHOR]

The growing demand for communication technology capable of providing high transmission rates in maritime environments has led to the exploration of the very high frequency (VHF) data exchange system (VDES) as a promising solution. The VDES, the integration of an automatic identification system (AIS), application-specific messaging (ASM), and VHF data exchange (VDE), offers improved transmission rates and stable connections compared with existing technologies. Although the VDES supports high transmission rates through various modulation and coding scheme (MCS) technologies, it lacks a standardized mechanism for controlling MCS parameters and relies on user algorithms for operation. In this paper, we introduce the maritime auto-rate fall-back (mARF) technology, designed to effectively address the challenges of maritime communication scenarios using the MCS framework provided by the VDES. mARF technology incorporates fast drop-out and recovery mechanisms to swiftly adapt to changing MCS types in the presence of deep nulls, a common occurrence in maritime communication environments. These adaptive thresholds for fast drop-out and recovery operations are dynamically learned using historical communication data. Through extensive simulations, we demonstrate the effectiveness of mARF in enhancing the MCS control capabilities of the VDES. Our results show a significant performance improvement of 18% compared to the existing model, validating the potential of mARF in optimizing maritime communication channels and supporting a high transmission rate. [ABSTRACT FROM AUTHOR]

In a previous work (Missaoui et al. in IEEE Wirel Commun Lett 6(2):150–153, 2017), we introduced a blind identification method of active users in multi-user MIMO systems, enabling to an estimation of their involved channels, with a resolution up to a discrete phase ambiguity. In this case, using exhaustive search algorithm, the phase ambiguity has been eliminated when both small numbers of colliding packets and receive antennas have been assumed. However, the exhaustive search is computationally infeasible for scenarios involving a relatively large number of receive antennas for MIMO and massive MIMO systems as one of the pivotal technologies for future wireless networks. To tackle this issue, in the current work, we propose an efficientt scheme to eliminate this phase ambiguity, based on both second-order cross-correlations of the signal flows received at the base station and blind channel estimates as obtained previously. Furthermore, to reduce the complexity of the proposed scheme, we use an iterative process to obtain a global phase ambiguity common to all receive antennas for each user. The aim is to make our solution applicable to practical systems with a large number of receive antennas and to easily eliminate this global phase ambiguity. Thus, we suggest two channel estimation and data detection approaches. In the first approach, which is blind, no pilot symbols are used, and the global phase ambiguity could be addressed using rotational-invariant coded modulations. In the second approach, which is semi-blind, only one pilot overhead symbol is needed to remove the common phase ambiguities. We show that our channel estimation and collision resolution scheme achieves a bit error rate (BER) performance which coincides with that of the single user with perfect channel state information knowledge. [ABSTRACT FROM AUTHOR]

A high-frequency surface wave radar (HFSWR) is the only sensor that provides inexpensive surveillance for up to 200 nautical miles (NM) of the exclusive economic zone in the 3–5 MHz band. However, because of its long wavelength, its angular resolution is low. Multiple-input multiple-output (MIMO) technology is an attractive method to improve angular resolution. This paper proposes MIMO waveforms and their processing that can be used in HFSWR systems. This dual modulation method applies linear frequency modulation to each pulse and orthogonal polyphase codes for a few consecutive pulses to enable MIMO processing. The proposed method can effectively remove the correlation of mutual interference and exhibits excellent performance in removing multiple-time-around echoes. [ABSTRACT FROM AUTHOR]

This paper proposes a novel machine learning (ML) assisted low‐latency low density parity check (LDPC) coded adaptive modulation (AM) system, where short block‐length LDPC codes are used. Conventional adaptive modulation and coding (AMC) system includes fixed look‐up table method, which is also called inner loop link adaptation (ILLA) and outer loop link adaptation (OLLA). For ILLA, the adaptive capability is achieved by switching the modulation and coding modes based on a look‐up table using signal‐to‐noise ratio (SNR) thresholds at the target bit error rate (BER), while OLLA builds upon the ILLA method by dynamically adjusting the SNR thresholds to further optimize the system performance. Although both improve the system overall throughput by switching between different transmission modes, there is still a gap to optimal performance as the BER is comparatively far away from the target BER. Machine learning (ML) is a promising solution in solving various classification problems. In this work, the supervised learning based k‐nearest neighbours (KNN) algorithm is invoked for choosing the optimum transmission mode based on the training data and the instantaneous SNR. This work focuses on the low‐latency communications scenarios, where short block‐length LDPC codes are utilized. On the other hand, given the short block‐length constraint, we propose to artificially generate the training data to train our ML assisted AMC scheme. The simulation results show that the proposed ML‐LDPC‐AMC scheme can achieve a higher throughput than the ILLA system while maintaining the target BER. Compared with OLLA, the proposed scheme can maintain the target BER while the OLLA fails to maintain the target BER when the block length is short. In addition, when considering the channel estimation errors, the performance of the proposed ML‐LDPC‐AMC maintains the target BER, while the ILLA system's BER performance can be higher than the target BER. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive bit-interleaved polar coded modulation (A-BIPCM) method based on minimum logarithmic upper bound weight (MLUW). It is designed to reduce the fading effects and long string of bit error interference caused by atmospheric turbulence in free-space optical communications (FSOC). To assess the effectiveness of this method across turbulent channels of varying intensities, we conducted an evaluation of the bit error rate (BER) performance of polar codes in turbulent channels. The results demonstrate significant performance improvements provided by the A-BIPCM method compared to conventional polar code encoding and decoding. Specifically, under weak, moderate, and strong turbulence conditions, the A-BIPCM method achieves performance gains of 0.96 dB, 1.66 dB, and 1.35 dB, respectively. Additionally, an experimental verification platform for FSOC employing intensity modulation direct detection (IM/DD) with an atmospheric turbulence simulation channel, is established in this work. When the optical power of the detector is −16 dBm, the traditional polar code encoding and decoding performance at BER = 2.36 × 10−5, whereas the A-BIPCM scheme exhibits a significantly higher performance at BER = 2.11 × 10−6. The BER has been improved by representing an order of magnitude. [ABSTRACT FROM AUTHOR]

This paper addresses the escalating threat of malicious jamming in next-generation communication systems, propelled by their continuous advancement in speed, latency, and connectivity. Recognizing the imperative for communication security, we propose an efficient jamming detection method with distinct innovations and contributions. Motivated by the growing sophistication of jamming techniques, we advocate the adoption of the error vector magnitude (EVM) metric, measured in IQ symbols, deviating from traditional received signal strength and bit error rate-based measurements. Our method achieves enhanced jamming detection sensitivity, surpassing existing approaches. Furthermore, it introduces low complexity, ensuring resource-effective detection. Crucially, our approach provides vital jammer frequency information, enhancing counteraction capabilities against jamming attacks. It demonstrates stable results against varying system parameters, such as modulation type and code rate, thereby contributing to adaptability. Emphasizing practicality, the method seamlessly integrates into 5G and LTE systems without imposing additional overhead. Versatility is demonstrated through successful operations in diverse scenarios that are run by extended simulation conditions. Theoretical analysis substantiates these advantages, reinforcing the validity of our methodology. The study's success is further validated through laboratory experiments, providing empirical evidence of its effectiveness. The proposed method represents a significant step toward fortifying next-generation communication systems against evolving jamming threats. [ABSTRACT FROM AUTHOR]

Nowadays, the rising demand for digital communication technologies has contributed to the increase in the volume of traffic. This continuous trend of internet traffic has led to the deterioration of the quality of service (QoS) with reduced throughput and increased latency. This also is due to the proliferation of new broadband applications which require low latency and high throughput such as virtual reality and real-time gaming. Therefore, considering the aforementioned challenge in QoS of wireless networks, a link adaptation method is suggested in this study, in order to enhance the performance of the QoS in IEEE 802.11ac amendment wireless local-area network (WLAN). The proposed technique adaptively changes the transmission data rate by increasing or decreasing the modulation and coding scheme (MCS) level according to the traffic conditions. With the use of an OMNeT++ computer-aided design (CAD)-based simulation model, the effectiveness of the suggested approach is examined. Simulated findings were compared with the link adaptation approach of the default condition. The results of the simulation demonstrate that the proposed technique significantly increases throughput (36.48%) and decreases latency in comparison to the default situation. These findings demonstrate the technique's potential to improve WLAN QoS efficiency, notably in regard to throughput and latency. [ABSTRACT FROM AUTHOR]

WiFi is a widely used wireless technology for data transmission. WiFi can also play a crucial role in simultaneously broadcasting content to multiple devices in multimedia transmission for venues such as classrooms, theaters, and stadiums, etc. Broadcasting allows for the efficient dissemination of information to all devices connected to the network, and it becomes crucial to ensure that the WiFi network has sufficient capacity to transmit broadcast multimedia content without interruptions or delays. However, using WiFi for broadcasting presents challenges that can impact user experience, specifically the difficulty of obtaining real-time feedback from potentially hundreds or thousands of users due to potential collisions of feedback messages. This work focuses on providing accurate feedback to the Access Point about the percentage of users not receiving broadcast traffic correctly so it can adjust its Modulation and Coding Scheme (MCS) while transmitting broadcast multimedia content to many users. The proposed method is comprised of two sequential algorithms. In order to reduce the probability of a collision after transmitting each message, an algorithm searches for the best probability value for users to transmit ACK/NACK messages, depending on whether messages are received correctly or not. This feedback allows the Access Point to estimate the number of STAs correctly/incorrectly receiving the messages being transmitted. A second algorithm uses this estimation so the Access Point can select the best MCS while maintaining the percentage of users not receiving broadcast content correctly within acceptable margins, thus providing users with the best possible content quality. We implemented the proposed method in the ns-3 simulator, and the results show it yields quick, reliable feedback to the Access Point that was then able to adjust to the best possible MCS in only a few seconds, regardless of the user density and dimensions of the scenario. [ABSTRACT FROM AUTHOR]

Recently, using iterative decoding algorithms to achieve an interesting bit error rate for spectrally efficient modulation become a necessity for optical transmission, in this paper, we propose a coded modulation scheme based on bit interleaving circular recursive systematic convolutional (CRSC) code and 16-QAM modulation. The proposal system considered as a serial concatenation of a channel encoder, a bit interleaver and M-ary modulator can be flexible easy to implement using a short code length. For a spectral efficiency η = 3 bit / s / H z , the coding gain at a bit error rate of 10−6 is about 8 dB. [ABSTRACT FROM AUTHOR]

Summary: The work focuses on the simultaneous improvement on the throughput and information freshness of the promising satellite‐based Internet of Things (S‐IoT). To this end, we first propose a method based on the adaptive modulation coding (AMC) and truncated layer‐coded hybrid automatic repeat request (L‐HARQ) strategies by especially considering the difference in the channel state information (CSI) between the transmitter and receiver. On account of the large signal delay of the S‐IoT systems, this paper establishes the channel model based on the correlation of the signal‐to‐noise ratio (SNR) under the outdated channel and the ideal channel. Secondly, considering the fact that the improved backtrack decoding is used in the L‐HARQ, the classical definition of age of information (AoI) is insufficient to quantify the status update freshness, we propose the age of error information (AoEI), which is defined as the elapsed time since the generation of the lastly successfully backtrack‐decoded status update. Thirdly, we characterize the statistical descriptions of the maximum wait time of the successfully recovered status updates and the interdeparture time between the two consecutive status update packets that are lastly successfully received. Then, the closed‐form expression of average AoEI is derived under the assumption of independent and identically distributed fading channels. Finally, the Markov decision process (MDP) framework is used to optimize the packet parameters in each round of L‐HARQ process under the general fading scenario. Thereby, the optimized transmission scheme that minimizes AoI with throughput constraint is solved. The simulations investigate the effect of system parameters on the average AoEI. [ABSTRACT FROM AUTHOR]