Improved Bit Error Rate Performance Research Articles

Joint PAPR reduction with channel estimation for OFDM-based VLC systems

Abstract This paper presents a new combination of channel estimation (CE) methods and peak-to-average power ratio (PAPR) reduction techniques for orthogonal frequency division multiplexing (OFDM)-based visible light communication (VLC) systems. We first propose iterative clipping and filtering to minimize the PAPR of optical OFDM signals. Then, we introduce a computationally efficient, high-performance channel estimation approach using block-type pilots with modified clipped signals. The proposed method integrates clipping with three distinct CE techniques, resulting in both significant PAPR reduction and enhanced bit error rate (BER) performance. Among the CE methods evaluated, the expectation-maximization (EM) technique provides better BER results compared to other approaches. Simulation results confirm that the combined use of clipping and advanced CE methods leads to notable improvements in PAPR reduction and BER performance for OFDM-based VLC systems.

An intelligent impulsive noise mitigation with deep learning method

AbstractTo enable message transmission among sensors and equipment, power line communication (PLC) is a widely adopted smart grid. However, due to the occurrence of impulsive noise (IN), reliable transmissions over PLC channels in the smart grid are challenging. Therefore, in this paper, we propose an adaptive noise mitigation scheme to clip the IN with the sliding window‐based method, where the altitude of the received signal in the current time slots is obtained by computing the average altitude of signals in the previous and next time slots. To detect the states of IN and dynamically estimate the power threshold of signals for the IN mitigation scheme, we develop an intelligent algorithm based on the long short‐term memory network. To prevent the useful signals from being eliminated as IN signals, we propose the accelerated proximal gradient method (APGM) based on tone reservation to reduce the peak‐to‐average power ratio (PAPR) for the transmitting signals with low computational complexity. In addition, the closed‐form expression of the bit error rate (BER) is derived for the proposed sliding window‐based IN mitigation scheme according to the probability density function of the IN. Simulation results demonstrate that the proposed IN mitigation scheme achieves a better BER performance than the conventional IN mitigation schemes. In addition, the APGM aided by IN mitigation can further improve BER performance due to the PAPR reduction.

Clipping Noise in Visible Light Communication Systems with OFDM and PAPR Reduction

This paper presents an analytical study of signal clipping that leads to the noise/distortion in the waveform of DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM)-based visible light communication (VLC) systems. The pilot-assisted (PA) technique is used to reduce the high peak-to-average power ratio (PAPR) of the time-domain waveform of the DCO-OFDM system. The bit error rate (BER) performance of the PA DCO-OFDM system is investigated analytically at three different clipping levels as well as without any clipping. The analytical BER performance is verified through simulation and then compared to that of the conventional DCO-OFDM without PAPR reduction at the selected clipping levels. The PA DCO-OFDM system shows improved BER performance at all three clipping levels.

Implementation of companding scheme for performance enhancement of optical OFDM structure

Abstract Due to its great spectral efficiency and resistance to multi-path fading, OFDM, or orthogonal frequency division multiplexing, is commonly utilized in optical communication systems. However, because of nonlinear distortions in optical components, OFDM signals are prone to a high peak-to-average power ratio (PAPR), which can severely impair bit error rate (BER) performance. This paper introduces a companding scheme to address high PAPR in optical OFDM systems and improve BER performance. The proposed scheme uses a nonlinear transformation to compress signal peaks and expand valleys, effectively reducing PAPR. Specifically, we investigate the µ-law companding technique, known for its simplicity and effectiveness in handling the active range of OFDM signals in optical communication. The companded signals are transmitted through an optical link and demodulated at the receiver. Simulation results show that the µ-law companding technique substantially reduces PAPR, leading to a significant improvement in BER performance. The companding process maintains signal integrity and spectral efficiency with minimal computational complexity and implementation cost. By mitigating nonlinearities introduced by optical components, this companding scheme enhances the overall reliability and efficiency of the optical OFDM system. An SNR gain of 2 dB–3 dB was achieved at a BER of 10−3.

Improvement of post BER performance in computer communication on Viterbi algorithm

Computer communication is the pivotal exchange of information and data among computing devices, exerting substantial influence over network communication quality. The conventional approach has typically centred on enhancing Bit Error Rate (BER) performance to bolster information quality during the transmission process. However, our research pioneers a novel strategy, focusing on post-BER improvement. Our innovative method prioritizes enhancing information quality at the receiver's end by implementing a unique approach. We employ the Viterbi algorithm to elevate the quality of individual words, ensuring accurate word recognition and precise comprehension. The ultimate goal is to provide end-users with an unambiguous and accurate understanding of transmitted words. Our simulation results conclusively demonstrate the effectiveness of this approach. Following the reception of words, we successfully attain the correct word information with remarkable accuracy. This approach transforms word-level information processing, safeguarding against inaccuracies and ambiguities that may otherwise compromise the integrity of data transfer. In summary, our research introduces a paradigm shift in optimizing information quality within computer communication networks. By focusing on post-BER improvements and harnessing the power of the Viterbi algorithm, we enable the receiver to decode words with precision and clarity. This breakthrough promises to enhance the overall quality and reliability of information exchange, further solidifying the foundation of modern computer communication.

Coding techniques for diversity enhancement of dense wavelength division multiplexing MIMO‐FSO fault protection protocols systems over atmospheric turbulence channels

AbstractAn enhanced transmission is presented in a multiple‐input‐multiple‐output (MIMO) dense‐wavelength division multiplexed (DWDM) free‐space‐optical (FSO) communication link using diversity coding techniques under the effect of turbulent weather phenomenon. The findings show good performance with an (8 channels × 2.5 Gbps data rate/channel) 20 Gbps 1500 m transmission distance. The bit‐error‐rate (BER), outage probability (OP), and signal‐to‐noise ratio (SNR) of the diversity combining techniques using maximum‐ratio combining (MRC), selection combining (SC), and equal‐gain combining (EGC) technique are evaluated in this work. The obtained results illustrate that Alamouti, space‐time coding (STC), space‐time block coding (STBC), space‐time trellis code (STTC), orthogonal STBC (O‐STBC), and quasi‐orthogonal STBC (QO‐STBC) on the minimum mean‐square‐error, and MRC are worth implementing on the DWDM‐FSO wireless communication systems. The mitigation of atmospheric turbulence is achieved using MIMO diversity combining techniques coding. The simulation results for diversity coding techniques using QO‐STBC/STTC and SC/MRC in the MIMO‐DWDM FSO communication system can improve BER performance, OP, and SNR. The MRC exhibits the lowest OP and BER when compared with the SC and EGC. The numerical results demonstrate that the FSO communication link using DWDM QO‐STBC/STTC improves the power penalty at both BER values under varying atmospheric turbulence conditions for ST, MT, and WT, in comparison to FSO systems without DWDM QO‐STBC/STTC diversity coding techniques.

Performance analysis of OSSK-UWOC systems considering pointing errors and channel estimation errors.

In this paper, we present the bit error rate (BER) performance of the underwater wireless optical communication (UWOC) systems using the optical space shift keying (OSSK) on the gamma-gamma turbulent fading channel, which also considers pointing errors and channel estimation errors. Firstly, we develop the new expressions for the probability density function (PDF) based on the Gamma-Gamma distribution with error factors. Subsequently, we analyze the statistical characteristic of the difference in attenuation coefficients between two channels in the OSSK system, by which we provide analytical results for evaluating the average BER performance. The results show that the effective improvement of spectral efficiency (SE) and BER performance is achieved by rationally allocating the number of lasers and detectors in the system. The OSSK-UWOC system performs better when a narrow beam waist is used. Furthermore, the presence of channel estimation error brings the BER performance advantage to the system, and the system with a high channel estimation error (ρ = 0.7) shows a 4 dB improvement in signal-to-noise ratio (SNR) gain compared to the system with a low channel estimation error (ρ = 0.95). The findings in this paper can be used for the UWOC system design.

Multilayer perceptron-based array reader optimization for ultra-high density magnetic recording

We have previously presented a utilization of a long-short-term memory (LSTM) network to improve the reliability of the log-likelihood ratios (LLRs) in a coded three-head/three-track bit-patterned magnetic recording (BPMR) system. To continuously enhance a bit error rate (BER) performance; therefore, this article introduces a novel LLR flipper utilizing a multilayer perceptron (MLP), which operates under the optimization of input numbers of array reader positions. We first optimize an input number of MLP-based soft-information flippers with varying the number of recording bits in various data patterns. Then, the right positions of an array reader under the operation of our proposed MPL flipper are also optimized to obtain better BER performance. The simulation results demonstrate that the proposed MLP flipper significantly improves BER performance compared to the previous LSTM flipper using the same input number. Moreover, our proposed system still provides superior performance when it is operated under an optimal input number and can be higher when working with the right array reader positions.

Filter bank multi-carrier based offset ternary phase shift keying(FBMC/OTPSK)

Filter bank multi-carrier (FBMC) is a popular researched technique for wireless communications that offers several advantages over traditional orthogonal frequency-division multiplexing (OFDM) systems. In this paper, we propose a FBMC system using offset Triangle phase shift keying (TPSK) modulation (FBMC/OTPSK), analyze its bit error rate (BER) performance via additive white Gaussian noise (AWGN) channel, and compare it to that of conventional FBMC using offset quadrature amplitude modulation (FBMC/OQAM) system. Simulation results show that the proposed FBMC/OTPSK system considerably improves BER performance over FBMC/OQAM system. Additionally, we explore the impact of using ternary convolutional coding (TCC) with TPSK and binary convolutional coding (BCC) with QAM. The presented TPSK modulation encoded by TCC offers better error rate performance and minimum amplitude fluctuation compared to QAM encoded by BCC; therefore, TCC-coded OTPSK is proposed to be used with FBMC instead of BCC-coded OQAM to benefit from its lower error rates without bandwidth expansion, as well increase information carried by symbol, hence increases throughput.

K-Means Based Constellation Optimization for Index Modulated Reconfigurable Intelligent Surfaces

Reconfigurable intelligent surface (RIS) has recently emerged as a promising technology enabling next-generation wireless networks. In this letter, we develop an improved index modulation (IM) scheme by utilizing RIS to convey information. Specifically, we study an RIS-aided multiple-input single-output (MISO) system, in which the information bits are conveyed by reflection patterns of RIS rather than the conventional amplitude-phase constellation. Furthermore, the K-means algorithm is employed to optimize the reflection constellation to improve the error performance. Also, we propose a generalized Gray coding method for mapping information bits to an appropriate reflection constellation and analytically evaluate the error performance of the proposed scheme by deriving a tight upper bound of the average bit error rate (BER). Finally, numerical results verify the accuracy of our theoretical analysis as well as the substantially improved BER performance of the proposed RIS-based IM transmission scheme.

A Novel Maximum Distance Separable Coded OFDM-RIS for 6G Wireless Communications

The vision of the sixth generation mobile communication (6G) calls for extremely reliable data transmission over complex and diverse wireless channels. By combining the maximum distance separable (MDS) codes with the classic orthogonal frequency division multiplexing (OFDM), we present a new paradigm with the assistance of the reconfigurable intelligent surfaces (RIS). In our design, the RIS with limited phase shifts are adopted and the pairwise error probability (PEP) of the proposed system is first derived. Then, in order to further minimize the bit error rate (BER), we provide a novel method based on phase alignment to obtain the optimal solution for the discrete phase shifts. Our simulation results show that the proposed scheme provides considerable BER performance improvements compared to conventional OFDM systems. Moreover, the proposed discrete phase optimization algorithm is capable of achieving performance similar to that of the system with continuous phase shifts.

A QR Decomposition Algorithm with Partial Greedy Permutation for Zero-Forcing Block Diagonalization

A new zero-forcing block diagonalization (ZF-BD) scheme that enables both a more simplified ZF-BD and further increase in sum rate of MU-MIMO channels is proposed in this paper. The proposed scheme provides the improvement in BER performance for equivalent SU-MIMO channels. The proposed scheme consists of two components. First, a permuted channel matrix (PCM), which is given by moving the submatrix related to a target user to the bottom of a downlink MIMO channel matrix, is newly defined to obtain a precoding matrix for ZF-BD. Executing QR decomposition alone for a given PCM provides null space for the target user. Second, a partial MSQRD (PMSQRD) algorithm, which adopts MSQRD only for a target user to provide improvement in bit rate and BER performance for the user, is proposed. Some numerical simulations are performed, and the results show improvement in sum rate performance of the total system. In addition, appropriate bit allocation improves the bit error rate (BER) performance in each equivalent SU-MIMO channel. A successive interference cancellation is applied to achieve further improvement in BER performance of user terminals.

Recurrent Neural Network Based Joint Equalization and Decoding Method for Trellis Coded Modulated Optical Communication System

In this paper, a joint equalization and decoding method based on recurrent neural networks (RNNs) is proposed for trellis coded modulation (TCM) systems. For traditional methods based on concatenated equalizers and Viterbi decoder, the information may be lost between the equalization and decoding. However, our proposed joint method can obtain the information bits directly from the received symbols and the error also can be corrected in iterations. In two-dimensional eight-level pulse amplitude modulation (2D-PAM8) links, we experimentally demonstrate that, compared with the traditional method based on Volterra filter and Viterbi decoder, the proposed joint method based on RNNs with similar complexity can achieve bit-error rate (BER) performance improvements of 1 dB, 1 dB, and 2 dB in 87.5 Gb/s, 100 Gb/s, and 112.5 Gb/s transmissions at 7% hard-decision forward-error-correction (HD-FEC) limit, respectively. For the 10 km standard single-mode fiber (SSMF) link at 87.5 Gb/s, the traditional method cannot get the BER below the 7% HD-FEC limit whereas the joint RNNs method with similar complexity can get the BER below the 7% HD-FEC limit. As the nonlinearity increases, the proposed joint method can achieve greater improvement of BER performance.

Multicarrier M-ary Permuted Quasi-Orthogonal Chaotic Vector Shift Keying with Index Modulation

A novel multicarrier system based on chaotic sequences with permutation and index modulation to improve spectral efficiency is presented in this paper. In this design, the quasi-orthogonality property of the permuted versions of chaotic sequences is used for getting multiple reference signals, thereby reducing by the transmission overhead of reference chaotic signals over additional subcarriers. This helps in improving the spectral efficiency of the proposed system. Also, index modulation is applied to the permuted chaotic signals in all subcarriers to provide better efficiency in terms of spectrum utilization as well as energy consumption. Hence, the information bits are conveyed by both M-ary modulation symbols and the indices of the selected permutated signals. In addition, the analytical expressions for bit error rate (BER) of the proposed system over additive white gaussian noise (AWGN) is derived and simulation results are used to validate the analytical values. The performance of the proposed system is compared with the multicarrier chaotic system available in the literature, thereby proving that the proposed system outperforms the existing system with improved spectral efficiency and energy efficiency and also provides improvement in BER performance of about 2dB over AWGN channel with hardware complexity trade-off.

Orthogonal variable spreading factor encoded unmanned aerial vehicle‐assisted nonorthogonal multiple access system with hybrid physical layer security

AbstractPhysical layer security (PLS) can improve the security of both terrestrial and nonterrestrial wireless communication networks. This study proposes a simplified framework for nonterrestrial cyclic prefixed orthogonal variable spreading factor (OVSF)‐encoded multiple‐input and multiple‐output nonorthogonal multiple access (NOMA) systems to ensure complete network security. Various useful methods are implemented, where both improved sine map and multiple parameter‐weighted‐type fractional Fourier transform encryption schemes are combined to investigate the effects of hybrid PLS. In addition, OVSF coding with power domain NOMA for multi‐user interference reduction and peak‐to‐average power ratio (PAPR) reduction is introduced. The performance of ‐rated convolutional, turbo, and repeat and accumulate channel coding with regularized zero‐forcing signal detection for forward error correction and improved bit error rate (BER) are also investigated. Simulation results ratify the pertinence of the proposed system in terms of PLS and BER performance improvement with reasonable PAPR.

Pilot-based channel estimation in spatial modulated OFDM systems for mobile wireless applications

Spatial modulation Orthogonal Frequency Division Multiplexing (SM OFDM) is a newly developed transmission technique that has been proposed as an alternative for multiple input multiple output (MIMO)-OFDM transmission. Channel estimation is important for coherent data detection in practical scenarios. This paper investigates estimate power, Mean Square Error (MSE) and Bit Error Rate (BER) parameter metrics with channel estimation algorithm for Additive White Gaussian Noise (AWGN) and Rayleigh fading channel on three test environments proposed by International Telecommunication Union (ITU) specified standard model. Simulation output shows that for an AWGN channel, an improvement of approximately 1 dB and 0.3 dB power is obtained with Minimum Mean Square Error (MMSE) estimate and Least Square (LS)-linear/Spline using DFT. Additionally, for various interpolations employed, MSE decreases as Signal to Noise Ratio (SNR) rises, and performance improvement in BER when compared to traditional LS/MMSE estimators also occurs. For Rayleigh fading channel also there arises an enhanced performance in the parameter metrics with MMSE-DFT compared to conventional estimators. In summary, simulation output shows that incorporating DFT algorithm can provide better estimate power, BER and MSE by eliminating the effect of noise externally the extreme channel delay length.

Sub-column pixel neural network scheme for modulation format shifting based optical camera communications.

In this Letter, a sub-column pixel neural network (SCPNN) scheme is proposed to label the pixel patterns in modulation format shifting based optical camera communication (MFS-OCC) systems. The MFS scheme, by identifying on-off keying (OOK) and Manchester signal formats, can additionally harvest one-bit information without sacrificing the pixel width per bit, resulting in a higher transmission rate for OCC without multi-level modulation. Compared with the conventional multi-threshold decision (MTD) scheme, the proposed SCPNN can effectively mitigate the impact of inter-symbol interference (ISI) and noise on signal decision by making full use of all pixels in one-bit period. The experimental results show that, in the case of the illuminance as low as 300 lux, the SCPNN scheme can attain a data rate of 8.16 Kbps with an average bit-error-rate (BER) of 2.2 × 10-3 below the HD-FEC limitation of 3.8 × 10-3. Meanwhile, the SCPNN scheme achieves remarkable BER performance improvement compared to both MFS-OCC with MTD scheme and conventional OOK-OCC system.

HP-DF SSK Method for UAVs Communication in Cooperative Multi-Hop Rician Networks

This paper presents techniques that are expected to improve the bit error rate (BER) performance of Unmanned Aerial Vehicles (UAVs) communication systems. The decode-and-forward (DF)-based cooperative multi-hop Rician network using space shift keying (SSK) modulation is employed for this purpose. The SSK modulation and cooperative communication are merged and used together. This enhances the BER performance for multiple-input multiple-output (MIMO) channels, thus accentuating its significance as an important technique for consistently reliable communication methodology while, at the same time, eliminating wastage of energy. The new technique is named as high performance (HP) due to not only BER performance improvement but also increase of the diversity of the communication system. This new model is further used for multi-hop networks and the resulting BER characteristics are assessed for possible enhanced performance in Rician channels. The paper also showcases the generalized-n-hop BER equation for various multi-hop DF-based cooperative communication systems in diverse UAV models. The Monte Carlo simulations further confirm the theoretical results that already exist for transmit-receive antennas. This work also underlines the fact that the number of hops in a communication system has no bearing whatsoever on the BER performance diversity value.

Patterns Quantization With Noise Using Gaussian Features and Bayesian Learning in VLC Systems

Nonlinear impairments seriously affect the transmission performance of high-speed visible light communication (VLC) systems, which have become the bottleneck of VLC systems in practical applications. To compensate for the nonlinear impairments of VLC systems, we propose a Pattern quantization method (PQM) based on Gaussian feature inputs and Bayesian learning in the time-domain. First, we investigate the signal distribution of VLC systems in the presence of additive white Gaussian noise (AWGN) and nonlinear impairments. Second, probability statistics are used to quantify the noise. Finally, a nonlinear compensator for PAM-8 VLC systems is realized using the Bayesian machine learning principle. In the experiment, a PAM-8 VLC system with a maximum transmission data rate of 1 Gb/s and bit error rate (BER) below the threshold of hard decision forward error correction (HD-FEC) is successfully demonstrated. The results indicate that the PQM compensator can significantly reduce nonlinear impairment and improve BER performance while requiring little computational effort. The Q-Factor is improved by 2.1 dB, the transmission distance is increased by 1/3, and the BER is reduced by 90.05% when compared with conventional nonlinear Volterra equalizers. As far as we know, our study is the first to investigate the input features and quantify the white noise in VLC systems, thereby providing a novel approach to machine learning input data processing.

Coherent Optical OFDM With Index Modulation for Long-Haul Transmission in Optical Communication Systems

In this paper, it is proposed to enhance coherent optical orthogonal frequency-division multiplexing (OFDM) system by using index modulation in terms of bit error rate (BER) and spectral efficiency for different levels of the fiber nonlinearity. In the coherent optical OFDM with index modulation system (CO-OFDM-IM), the information is conveyed not only through activated subcarriers but also by indices of the active subcarrier that are dynamically updated at the transmitted symbol rates. Unlike the conventional coherent optical OFDM (CO-OFDM) system, adjusting the number of the active subcarriers in the CO-OFDM-IM system provides improved BER performance and reduction the signal peak-to-average-ratios, when the fiber nonlinearity becomes significant. The simulation results illustrate that the proposed CO-OFDM-IM system has better BER performance when the proposed CO-OFDM-IM system and the CO-OFDM system have similar spectral efficiency. Also, the CO-OFDM-IM system can provide better spectral efficiency than the CO-OFDM system at the low-to-medium order modulation such as BPSK, QPSK, and 16QAM.