Superior Bit Error Rate Performance Research Articles

Bit-island arrangement and signal processing in double-layer magnetic recording technology

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.

Single and Multi-Point Non-Orthogonal Multiple Access based Power Adaptive Design for Improving Bit Error Ratio

Abstract In the framework of next-generation communication systems, Non-Orthogonal Multiple Access (NOMA) has attracted considerable interest. The fundamental advantage is that it has greater spectrum utilization than its orthogonal equivalents. This proposed work integrates Single-Input Single-Output NOMA (SISO) with Coordinated Multi-Point (CoMP). It uses both systems based on Quadrature Phase-Shift Keying (QPSK). A power-tolerant NOMA reduces the system’s vulnerability to erroneous power allocation by adaptively modifying each user’s signal power. The transmitted data is used to modify the power in the Power-Adaptive NOMA (PANOMA). PANOMA helps improve the Bit Error ratio and also improves the computational complexity. The Bit Error Rate (BER) and the lower limit capacity efficiency across Rayleigh fading channels are determined in precise closure representations of more than two consumer situations to measure its capability. The proposed method PA-CoMP-NOMA improves the Bit Error ratio in both systems. It improves the average BER among all users. Compared to its orthogonal cousin, NOMA has higher spectral efficiency. Nevertheless, our proposed method retains this feature as well as superior BER performance, although its spectral effectiveness is lower than that of the classic sum-rate based power NOMA.

Toward Chaotic Secure Communications: An RIS Enabled M-Ary Differential Chaos Shift Keying System With Block Interleaving

Chaotic secure communication systems using chaotic waveforms as their spreading carriers can hide the transmitted information bits over a wide frequency range of chaotic waveform, which disguises the transmitted information waveform as noise. In this paper, a reconfigurable intelligent surface (RIS) enabled <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary differential chaos shift keying with block interleaving (RIS-MDCSK-BI) system is proposed for chaotic secure communications, where an RIS is deployed at the transmitter to assist communications and a pair of block interleaving patterns are used to interleave <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary information-bearing signals to enhance security performance. Moreover, we propose a chaotic merging sort algorithm to generate different block interleaving patterns, where these interleaving patterns are encrypted by using the non-periodic and noise-like properties of chaotic signals. To estimate information bits at the legitimate receiver, we propose a sequential detection algorithm and a joint detection algorithm. Then, theoretical bit error rate (BER) performances of the proposed RIS-MDCSK-BI system with the legitimate receiver and the eavesdropping receiver are derived. The security performance metrics, including information leakage and secrecy outage probability, are also analyzed. Monte Carlo simulations are performed to verify the superior BER performance and security performance of the proposed RIS-MDCSK-BI system compared to benchmark systems.

5G V2X Performance Comparison for Different Channel Coding Schemes and Propagation Models

Channel coding is a fundamental procedure in wireless telecommunication systems and has a strong impact on the data transmission quality. This effect becomes more important when the transmission must be characterised by low latency and low bit error rate, as in the case of vehicle-to-everything (V2X) services. Thus, V2X services must use powerful and efficient coding schemes. In this paper, we thoroughly examine the performance of the most important channel coding schemes in V2X services. More specifically, the impact of use of 4th-Generation Long-Term Evolution (4G-LTE) turbo codes, 5th-Generation New Radio (5G-NR) polar codes and low-density parity-check codes (LDPC) in V2X communication systems is researched. For this purpose, we employ stochastic propagation models that simulate the cases of line of sight (LOS), non-line of sight (NLOS) and line of sight with vehicle blockage (NLOSv) communication. Different communication scenarios are investigated in urban and highway environments using the 3rd-Generation Partnership Project (3GPP) parameters for the stochastic models. Based on these propagation models, we investigate the performance of the communication channels in terms of bit error rate (BER) and frame error rate (FER) performance for different levels of signal to noise ratio (SNR) for all the aforementioned coding schemes and three small V2X-compatible data frames. Our analysis shows that turbo-based coding schemes have superior BER and FER performance than 5G coding schemes for the vast majority of the considered simulation scenarios. This fact, combined with the low-complexity requirements of turbo schemes for small data frames, makes them more suitable for small-frame 5G V2X services.

Energy efficient data detection with low complexity for an uplink multi-user massive MIMO system

The current development of the Internet of Things (IoT) network in sixth-generation (6G) communication opens up various opportunities. When IoT devices with edge platforms connect to the telecommunication network, mobility, interferences, and intelligent device capacity issues might occur. The challenge with uplink MU-MIMO systems is data detection owing to noise, frequency allocations, and dense deployment of intelligent devices. The exponential complexity of extensive wireless networks makes optimal maximum likelihood detection impossible. Using MATLAB simulation-based analysis, we suggested an iterative data detection strategy based on a coordinate descent method (CDM) to reduce computing complexity while preserving an acceptable bit error rate (BER). Linear systems demand low co-channel interference (CCI) MU-MIMO uplink communications (CCI). A superior mean square error or BER performance is achieved using Maximum ratio combining with CDM. The proposed system outperforms the Richardson Method (RM), approximation message passing (AMP), and linear minimum mean square error (LMMSE) algorithms in terms of BER and complexity.

Optical Index-Coded Space Shift Keying (IC/SSK)

In this letter, a new channel coding technique is proposed for optical spatial shift keying (SSK)-based visible light communications (VLC) systems by introducing redundancy in the spatial domain. The information is encoded by the redundant indices of the light emitting diodes (LEDs), assuming full channel state information (CSI) at the transmitter. The efficient construction of index-coding (IC) is presented with low computational complexity. Depending on the number of LEDs and the PDs as well as the amount of redundancy, it is concluded that IC/SSK achieves excellent coding gains at full rate and given target bit error rate (BER), as contrasted to the conventional channel coding in bit-domain, and yields superior BER performance in the presence of the VLC <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">blockage channels</i> as compared to the uncoded SSK systems.

Design of Enhanced Permutation Differential Chaos Shift System Using Signal Reference With Dual Modulation

In this paper, a permutation-based chaos system, named as Single Reference Permutation Index with Dual Modulation Differential Chaos Shift Keying (SR-PIDM-DCSK), is developed and tested. The proposed system uses the chaotic segment and its reversed version to modulate two pairs of data sets simultaneously. It uses the same reference for multiple symbol modulation. This significantly reduces bit energy requirement and enhances the Bit Error Rate (BER). In addition, it reduces the complexity of the system. At the transmitter, the reference signal is sent first, then the same reference is delayed and permutated to send the first information set of bits, while the same version is time reversed and permutated to modulate the second set of bits. Both segments are added together on the same symbol duration slot for transmission. This process is repeated for multiple symbols in a frame. At the receiver, the incoming reference signal is delayed for several symbol durations for demodulation. The BER of the system is evaluated in various channel environments. Moreover, a theoretical prediction for BER formula is developed for the suggested model. Results show that the proposed system has superior BER performance compared with other standard chaos based systems by an average of 2 dB. It is evident that the BER performance is enhanced with the increase in the spreading factor and the number of symbols in a frame. The theoretical formula for BER prediction is validated by computer simulation. Excellent matching was found between the theoretical formula and simulation results.

Subcarrier-Wise Backscatter Communications Over Ambient OFDM for Low Power IoT

Ambient backscatter communication (AmBC) over orthogonal-frequency-division-multiplexing (OFDM) signals has recently been proposed as an appealing technique for low power Internet-of-Things (IoT) applications. The special spectrum structure of OFDM signals provides a range of flexibility in terms of bit-error-rate (BER) performance, data rate, and power consumption. In this paper, we study subcarrier-wise backscatter communication over ambient OFDM signals. This new AmBC is to exploit the special spectrum structure of OFDM to transmit data over its squeezed orthogonal subcarriers. We propose a basis transmission scheme and its two modifications to support a higher data rate with superior BER performance compared to existing methods. The basis scheme can transmit one bit per subcarrier using on-off keying (OOK) modulation in the frequency domain. In the first modification, interleaved subcarrier block transmission model is employed to improve the BER performance of the system in frequency-selective channels. It results in a trade-off between the size of the blocks and data rate. Thus, in the second modification, interleaved index modulation (IM) is employed to mitigate the data rate decrementation of the former modification. It also stabilizes and controls the power of the signal to result in interference reduction for a legacy receiver. Analytical and numerical evaluations provide a proof to see the performance of the proposed method in terms of BER, data rate, and interference.

Sparse-Encoded Codebook Index Modulation

Ultra-reliable and low-latency communications (URLLC) partakes a major role in 5 G networks for mission-critical applications. Sparse vector coding (SVC) appears as a strong candidate for future URLLC networks by enabling superior performance in terms of bit error rate (BER). SVC exploits the virtual digital domain (VDD) and compressed sensing (CS) algorithms to encode and decode its information through active symbol indices. In this paper, first, a clever encoding/decoding algorithm is proposed for the SVC scheme, which allows the use of all possible activation patterns (APs) resulting in increasing spectral efficiency. Second, a novel solution is proposed to convey additional information bits by further exploiting index modulation (IM) for the codebooks of the SVC scheme. Computer simulation results reveal that our low-complexity algorithm and novel IM solution provide not only a superior BER performance but also an increase in the number of bits conveyed by IM compared to the ordinary SVC approach.

Robust decoding strategy of MIMO-STBC using one source Kurtosis based GPSO algorithm

Most research papers have referred that the performance of bit error rate (BER) for a Multiple-Input Multipl-Output Space–Time Block Code (MIMO-STBC) decoder fundamentally relies on the number of pilot symbols. This paper proposes a new strategy for decoding a MIMO-STBC using blind source separation (BSS). First, the STBC decoder is modeled as a noisy linear mixing system, which is decomposed using the technique of real-imaginary (Re-Im). Then Kurtosis based BSS algorithm is applied to the decomposition model. The method of one source extraction is also used to reduce decoding time efficiently. Finally, a global particle swarm optimization method (GPSO) is combined with the one source extraction Kurtosis based BSS to obtain a high speed/low complexity MIMO-STBC decoder. The classical PSO algorithm in this paper is modified by innovating a new updating formula, which is the combination of the swarm behavior and BSS algorithm. Although the new decoder is more complicated as compared with the conventional one, it provides superior BER performance using a fewer number of pilot symbols. Computer simulation for QPSK STBC in a quasi-static flat fading MIMO channel was implemented using MATLAB2018. The new decoder algorithm was tested using only two receivers, worst case. The important point denoted through simulation is the BER performance of the proposed decoder was significantly got better when the length of frames gets longer. The proposed strategy was also used in decoding the $$8\times 8$$ MIMO-STBC system in an extreme noise environment. It was found the BER performance improved nine times as compared with the traditional decoder. Finally, the modified GPSO algorithm made the proposed decoder needs a very small number of iterations, even though the search space dimension is very high.

BER Performance Improvement of Alamouti MIMO-STBC Decoder Using Mutual Information Method

Bit error rate (BER) performance of multiple input multiple output (MIMO) space time block code (STBC) decoder depends on the channel estimator quality, where the quality of classical least square (LS) estimator depends mainly on the number of pilot symbols. The aims of this paper are to implement a new STBC decoder, measure the BER performance and make comparison with conventional one, without increasing the number of pilot symbols. Although the new strategy is more complex than a conventional decoder, it gives the opportunity to join estimation and decoding at the same time. Minimum mutual information (MMI)- independent component analysis (ICA) algorithm has been used for extracting source signals. MIMO-STBC systems were taken as a cases study with two transmitters. The simulation results show that MMI-ICA algorithm provides superior BER performance as compared with conventional maximum ratio combiner (MRC). The important point, which denoted during simulation, the performance of ICA algorithm with high frame length provides better BER performance than the conventional one.

Channel-Aware Adaptive Physical-Layer Network Coding Over Relay-Assisted OFDM-VLC Networks

In this article, we propose and experimentally demonstrate the full-duplex channel-aware adaptive physical-layer network (APNC) coding over orthogonal frequency division multiplexing (OFDM) based visible light communication (VLC) to boost the capacity of relay-assisted VLC networks. The network encoding is realized by detecting signals coming from different terminal nodes simultaneously with a single photodiode at the relay node, which then achieves the amplify-and-forward function. At the receiver of each terminal node, the desired signal can be reconstructed by applying the corresponding APNC decoding to the detected interfered signal from the relay node. The use of adaptively loaded OFDM not only addresses the inherent frequency fading issue in VLC systems but also relaxes the synchronization issue at the relay node. The detailed principles of the proposed full-duplex channel-aware APNC scheme are presented, and its performance is experimentally investigated in a two-way-relay (TWR) VLC network. Experimental results show that the proposed scheme exhibits superior BER performance to other existing network scheduling schemes. For a TWR-VLC network with a fixed 600-Mb/s throughput, we achieve around two orders of magnitude reductions in the bit-error-rate (BER) by using the proposed channel-aware APNC scheme compared to other schemes, and BERs of 3.96 × 10−4 and 5.32 × 10−4 are attained for the two transmission links in the TWR network, respectively.

Interference Mitigation Using Angular Diversity Receiver With Efficient Channel Estimation in MIMO VLC

Visible Light Communication (VLC) is a promising solution to meet the ever increasing demand for indoor data connectivity with high bit rates. VLC uses the license-free bands and provides high-speed connections unlike RF wireless communication. However; indoor VLC suffers from performance degradation due to either co-channel interference (CCI) or inter-symbol interference (ISI). In this paper, an interference management scheme is proposed for VLC Multi-Input Multi-Output (MIMO) based systems. The scheme reduces the number of interfered signals by using a constrained field-of-view angular diversity receiver CFOV-ADR and then uses least-square (LS) channel estimation with maximum-likelihood (ML) equalizer to resolve the interfered signals. The proposed interference mitigation scheme using constrained-FOV-ADR with channel estimation IM-CFOV-CE enables frequency reuse of one. The bit-error-rate (BER) is calculated at various room positions with different receiver’s heights and rotation angles. The performance evaluation results reveal that the proposed system can achieve a higher number of downlink channels and superior BER performance than that of without CCI management. Also, the proposed scheme has been compared with Time Division Multiple Access (TDMA) technique, and achieves enhanced performance at all positions and orientations of the ADR.

Optimal Array-Reader and Track Misregistration Mitigation Method in a Three-Reader/Four-Track Reading Bit-Patterned Magnetic Recording System

Track misregistration (TMR) is one of several problems in ultrahigh areal density bit-patterned magnetic recording (BPMR) systems, in which the distances between bit-islands are very narrow in both cross-track and down-track directions. Unfortunately, distance reduction leads to intersymbol interference and intertrack interference (ITI) effects, which cause system performance degradation. To deal with these effects, we develop the optimal position of an array-reader based on a three-reader/four-track reading BPMR system that is combined with a simple two-dimensional rate-3/4 modulation code and ITI subtraction technique, which delivers the best avoidance of the ITI effect from sidetracks. We model TMR estimation and mitigation methods using readback signals that are obtained from the optimal array-readers to improve bit error rate (BER) performance. The variance-ratio of these readback signals is used to estimating the TMR levels, whereas a pair of the target's and equalizer's coefficients, accordingly designed to the estimated TMR levels, is adopted for mitigating the TMR effect. Simulation results show that our methods provide a high TMR estimation accuracy and gain a superior BER performance compared with the recording system without these techniques under the same user density.

Performance Enhancement of an Orbital-Angular-Momentum-Multiplexed Free-Space Optical Link Under Atmospheric Turbulence Effects Using Spatial-Mode Multiplexing and Hybrid Diversity Based on Adaptive MIMO Equalization

In this paper, we propose an adaptive multiple-input–multiple-output (MIMO) free-space optical (FSO) links using an orbital-angular-momentum (OAM)-multiplexed based on the spatial-mode multiplexing (SMM) through the turbulent channel. We propose to use the SMM and spatial-mode diversity (SMD) combined with an adaptive MIMO technique to mitigate the atmospheric turbulence effects. In this paper, our objective is to design the adaptive MIMO–FSO links based on OAM–MIMO/SMM multiplexed and analyze its performance in the atmospheric turbulence conditions. The simulation results show four OAM modes-based MIMO/SMM and resulting in four OAM-multiplexed channels. Each OAM mode carries a 100-Gbit/s quadrature phase-shift keying signal (aggregate 400 Gbit/s) on a single wavelength channel ( $\lambda \sim 1550$ nm) and is transmitted for a 2-km link. The calculated received power and inter-channel crosstalk of an OAM–MIMO/SMM signal fluctuate by 4.5 −6 dB, respectively. The power penalties can be reduced by 1–4 dB for all channels after OAM–MIMO/SMM equalization at a bit-error rate (BER) of 10−9. The calculating results show that the system using an OAM-based MIMO/SMM and SMD multiplexing achieves superior BER performance using an adaptive MIMO/SMM equalization. The Numerical results show favorable transmission performance of OAM based on MIMO/SMM and the SMD multiplexing compared to the conventional-MIMO (CMIMO) of FSO transmission link. The Simulation models verified the superior BER performance of OAM–SMD-based MIMO/SMM. The SMM/MIMO–SMD technique performed better in the channel capacity and signal-to-noise ratios over other commonly used CMIMO algorithms. To sufficiently discuss the OAM–MIMO/SMM behavior-based SMD multiplexing, the performance of the novel SMM/MIMO–SMD technique is analyzed using simulations based on the Matlab/simulink program in order to verify the accuracy of the models and simulation results. This paper could be useful for the practical implementation of the SMM and the SMD using an adaptive MIMO equalization in the FSO systems.

Performance Analysis for Spatial Modulation With AF Relaying Over Spatially Correlated Rayleigh Channels

As a low-complexity and energy-efficient multiple input multiple output (MIMO) technique, spatial modulation (SM) has received much interest recently. Combining SM with cooperative relaying, the performance of SM systems can be significantly improved. Considering joint transmit-receive-correlated Rayleigh channels, the error performance and power allocation (PA) of the amplify-and-forward (AF) relaying aided cooperative SM system are presented in this paper. Based on the moment generating function (MGF), the probability density function (PDF) of effective signal-to-noise ratio (SNR) is derived. With this PDF, a closed-form expression of the pairwise error probability (PEP) is obtained. Utilizing the obtained PEP and the union bound of bit error rate (BER), the approximate average BER expression is further derived, which will benefit the performance analysis of the system in spatially correlated channels. According to the asymptotical performance analysis at high SNR, an asymptotic BER expression is also derived. By minimizing this asymptotic BER, a suboptimal power allocation scheme is developed, and the closed-form PA coefficients are attained. Besides, the diversity order of system is also analyzed and derived for the performance evaluation. Numerical results show that our theoretical analysis is valid, and can match the corresponding simulation well. Moreover, the proposed PA scheme can achieve superior BER performance over the conventional equal PA scheme since the powers are well allocated in terms of channel information.

Subcarrier and Power Allocations for Dimmable Enhanced ADO-OFDM With Iterative Interference Cancellation

In this paper, a novel modulation scheme called enhanced asymmetrically clipped DC-biased optical OFDM (eADO-OFDM) is proposed to accommodate different demands of multi-users in downlink multiple access for visible light communication systems. Meanwhile, to satisfy various dimming levels, enhanced negative ADO-OFDM (eNADO-OFDM) is investigated and combined with eADO-OFDM for multiplexing transmission. By adjusting the proportion of these two signals, the dimming control scheme can be achieved, while the entire dynamic range of light-emitting diodes is exploited. In order to achieve superior transmission performance, the optimal power allocation under the desired dimming level is studied to minimize the overall bit error rate (BER). Moreover, to obtain more accurate estimation, an iterative receiver with interference cancellation, in which the pairwise averaging and pairwise clipping are exploited, is proposed. The simulation results show that the proposed scheme can effectively carry out the dimming control with wide dimming range for illumination and achieve superior BER performance at the same signal-to-noise ratio compared to the conventional counterparts, while only a few iterations are required.

Analysis of Nyquist Pulse Shapes for Carrierless Amplitude and Phase Modulation in Visible Light Communications

This paper proposes and experimentally demonstrates, for the first time, two new candidate pulse shapes for carrierless amplitude and phase modulation in the context of visible light communications. It is commonly accepted that the pulse shape at the heart of the Hilbert pair used to generate the required orthogonal signal spaces should be the square-root raised cosine. In this paper, we introduce two additional candidate pulse shapes, namely the first csv pulse and the so-called better-than-Nyquist pulse. We demonstrate experimentally that the better-than-Nyquist pulse offers superior bit-error rate performance compared to the square-root raised cosine and Xia pulses under additive white Gaussian noise channel conditions, while offering lower computational complexity.

Adaptive Precoding-Based Detection Algorithm for Massive MIMO Visible Light Communication

Visible light communication (VLC) has emerged as a promising, green, and interference-free supplement to existing radio frequency-based communication systems. To enhance the capacity of existing VLC-based systems, using massive arrays of light emitting diodes (LEDs) at the transmitter and photodiodes at the receiver has been proposed recently, resulting in a massive multiple-input multiple-output (m-MIMO) VLC system. However, by increasing LED array pitch in m-MIMO, the VLC channel matrices are generally ill conditioned which makes them sensitive to small perturbations and degrades the overall bit error rate (BER) performance. To reduce the condition number of the overall channel matrix, a novel precoder using an exponent-based singular value decomposition is proposed for m-MIMO VLC system. Furthermore, a joint optimization problem is formulated to optimize the exponent and to detect symbols iteratively using the minimum symbol error rate criterion. Simulations show that the proposed adaptive precoding technique exhibits superior BER performance over existing techniques. Analytical upper bounds for BER are also derived and validated by simulations.

Symbol Detection of Ambient Backscatter Systems With Manchester Coding

Ambient backscatter communication is a newly emerged paradigm, which utilizes the ambient radio frequency signal as the carrier to reduce the system battery requirement, and is regarded as a promising solution for enabling large-scale deployment of future Internet of Things networks. The key issue of ambient backscatter communication systems is how to perform reliable detection. In this paper, we propose novel encoding methods at the information tag and devise the corresponding symbol detection methods at the reader. In particular, Manchester coding and differential Manchester coding are adopted at the information tag, and the corresponding semi-coherent Manchester (SeCoMC) and non-coherent Manchester (NoCoMC) detectors are developed. In addition, analytical bit-error-rate (BER) expressions are characterized for both detectors assuming either complex Gaussian or unknown deterministic ambient signal. Simulation results show that the BER performance of unknown deterministic ambient signal is better, and the SeCoMC detector outperforms the NoCoMC detector. Finally, compared with the prior detectors for ambient backscatter communications, the proposed detectors have the advantages of achieving superior BER performance with lower communication delay.