Error Performance Of System Research Articles

An efficient non-binary QC-LDPC coded modulation scheme for long-haul optical systems

Abstract Coded modulation (CM), which combines channel codes with high-dimensional modulation schemes, is an attractive technique to improve the spectral efficiency in high-speed optical transmission systems. Non-binary low-density parity check (NB LDPC) codes can provide larger coding gains with smaller codeword lengths compared to their binary counterpart, in addition to reducing the latency of the system. The majority of works based on NB LDPC CM focus on bit-interleaved CM (BICM) and the widely used additive white Gaussian noise (AWGN) channel model. However, the Gaussian channel model is not a realistic model for long-haul intensity-modulated direct-detection (IM/DD) optical systems using erbium-doped fiber amplifiers. In this paper, it is mathematically proved that noise in the received signals after photodetection can be more accurately represented using chi-squared distribution. The efficiency of CM depends on the mapping between coded symbols and the constellation signal points of the modulation scheme. Hence, a symbol interleaved CM with subcarrier modulation for NB LDPC codes based on the proposed channel model is presented in this paper to improve the bit-error rate (BER) performance. The simulation results show that the proposed CM for NB LDPC codes with M-ary quadrature amplitude modulation schemes provides better performance than BICM. The analysis of the error performance of the proposed system gives a coding gain of 1 dB at a BER of 10−7 compared to that of the AWGN channel model. The performance improvement of the system is also evaluated in terms of spectral efficiency and link distance.

Error Performance of NOMA System With Outdated, Imperfect CSI, and RHI Over $\alpha-\mu$ Fading Channels

Error Performance of NOMA System With Outdated, Imperfect CSI, and RHI Over $\alpha-\mu$ Fading Channels

On the error performance and channel capacity of a uniquely decodable coded FSO system over Malaga turbulence with pointing errors.

Our previous work has proved that the uniquely decodable code (UDC) has the ability of enhancing the throughput of a free space optical communication (FSO) system. This paper quantitatively analyzes the error performance and channel capacity of the UDC-FSO system under Malaga turbulence and pointing errors. We first propose the minimum distance of the superimposed patterns (MDSP) approximation to reveal the universal symbol error rate (SER) for UDC-FSO systems. A closed form expression of SER is further deduced for a special case of 2 TXs. Based on the deduced SER, the upper and lower bounds of bit error rate (BER) can be obtained. Additionally, the discrete channel capacity of the UDC-FSO system is defined and deduced according to different superposition patterns, as well as the channel capacity gain. Both simulation and experiment verify the accuracy of the MDSP and SER's expressions. It's also discovered that the channel capacity of the UDC-FSO system is superior to the conventional end-to-end (E2E) link, where maximal channel capacity is limited by the UDC codebooks.

Double Reconfigurable Intelligent Surface to Improve Error Performance and Coverage Probability of Wireless Communication System

This paper investigates the symbol error rate (SER) and coverage probability of single reconfigurable intelligent surface (S-RIS) and double reconfigurable intelligent surface (D-RIS) systems operating over Weibull fading channels. In the S-RIS system, the RIS is positioned between the base station and user link, while in the D-RIS system, RIS-1 and RIS-2 are placed near the base station and user respectively. By leveraging the central limit theorem, we derive the statistical parameters of the received signal-to-noise ratio (SNR) and subsequently closed-form expressions for SER and coverage probability of both systems using the moment-generating function. Also, we determine the optimal location of the RISs in D-RIS system from the simulations of SER. Comparative analysis reveals that the D-RIS system exhibits superior error performance and provides better coverage than the S-RIS system, despite having an equal number of reflecting elements. In addition, we provide an energy consumption gain analysis of the D-RIS system.

Indexed-channel estimation under frequency and time-selective fading channels in high-mobility systems

<p><span lang="EN-US">Index modulation (IM) techniques have been employed in different communication systems to improve bandwidth efficiency by carrying additional information bits. In high-mobility communication systems and under both time-selective and frequency-selective fading channels with Doppler spread, channel variations can be tracked by employing pilot-aided channel estimation with minimum mean-squared error estimation. However, inserting pilot symbols among information symbols reduces the system's spectral efficiency in pilot-aided channel estimation schemes. We propose pilot-aided channel estimation with zero-pilot symbols and an energy detection scheme to tackle this issue. Part of the information bit-stream is conveyed by the indices of zero-pilot symbols leading to an increase in the system's spectral efficiency. We used an energy detector at the receiver to detect the transmitted zero-pilot symbols. This paper examines the impacts of diversity order on the zero-pilot symbol detection error probability and the mean-squared of error estimation. The impacts of pilot symbols number and the zero-pilot symbol number on the mean-squared error of the minimum mean-squared error (MMSE) estimator and the system error performance are also investigated in this paper.</span></p>

Performance Analysis of Channel Imbalance Control and Azimuth Ambiguity Suppression in Azimuth Dual Receiving Antenna Mode of LT-1 Spaceborne SAR System

The LuTan-1(LT-1), known as the L-band differential interferometric synthetic aperture radar (SAR) satellite system, is an essential piece of civil infrastructure in China, providing extensive applications such as surface deformation monitoring and topographic mapping. To achieve high-resolution and wide-swath (HRWS) observation abilities, the LT-1 takes the dual receiving antenna (DRA) imaging mode as its working mode. However, amplitude and phase errors between channels lead to a mismatch between the reconstruction filter and the multichannel echo signal, worsen the reconstructed azimuth spectrum, and introduce ambiguity targets in the final imaging results, seriously affecting the final imaging quality. In order to better evaluate the channel error and azimuth ambiguity performance of the LT-1 system, this paper proposed an advanced channel consistency correction method and conducted many measured data experiments. The experimental results show that the proposed method is effective, and the LT-1 system has excellent channel error control and azimuth ambiguity performance.

Vehicular visible light communications noise analysis and modeling.

Vehicular visible light communications (VVLC) is promising intelligent transportation systems technology with the utilization of light-emitting diodes. The main degrading factor for the performance of VVLC systems is noise. Traditional VVLC systems noise modeling is based on the additive white Gaussian noise assumption in the form of shot and thermal noise. In this paper, to investigate both time correlated and white noise components of the VVLC channel noise, we propose a noise analysis based on Allan variance, which provides a time-series analysis method to identify noise from the data. The results show that white noise and random walk are observed in the VVLC systems. We also propose a motion detection algorithm based on the adaptive Gaussian mixture (GM) model to generate a double Gaussian model of VVLC channel noise. We further present a study on the error performance of a VVLC system considering channel noise to be a mixture of Gaussian components. We derive the analytical expressions of probability of error for binary phase-shift keying and quadrature phase-shift keying constellations. It has been observed that, in the presence of GM noise, the system performance degrades significantly from the usual one expected in a Gaussian noise environment and becomes a function of the mixing coefficients of the GM distribution.

Design and Implementation of an Enterprise Credit Risk Assessment Model Based on Improved Fuzzy Neural Network

ABSTRACT In order to improve the effect of enterprise credit risk assessment, this paper combines the improved fuzzy neural network to construct the enterprise credit risk assessment model. The various jamming patterns that can threaten the credit data transmission system include various blocking jamming and tracking jamming. Moreover, this paper analyzes the bit error performance of the credit data transmission system against various interferences, and obtains the bit error curves against various interferences through program simulation. In addition, this paper builds a variable-speed credit data transmission system based on Simulink, analyzes the key technologies in variable-speed credit data transmission, and simulates the anti-interference performance of variable-speed credit data transmission technology. The simulation study verifies that the enterprise credit risk assessment model proposed in this paper has good risk assessment effect and risk response strategy effect.

UOWC performance based on GMSK modulation

Abstract This paper studies and investigates the performance of Gaussian minimum shift keying (GMSK) for underwater optical wireless communication (UOWC). Various scatterings may result in inter-symbol interference (ISI) and degrade system error performance in UWOC links. Bit-error rate (BER) is evaluated using different water environment models such as clear seawater, coastal, and harbor for a 20 m link range. Simulation results indicate the BER performance is degraded due to the temporal dispersion of impulse response for high data rates in turbid water. In addition, the bandwidth-symbol time product (BT) is an essential parameter in GMSK, affecting BER performance and power efficiency. Therefore, BT must be chosen with a value that balances BER and power efficiency. The results show that GMSK with BT = 0.5 is a good choice that satisfies BER = 10−5 for SNR = 10 dB with an efficient power spectrum due to constant envelope and low out-of-band radiation.

Research on uplink performance of MIMO terrestrial-satellite laser communication based on OSM-MBM joint modulation

This paper proposes a multiple-input multiple-output (MIMO) terrestrial-satellite laser communication uplink system based on optical spatial modulation with medium-based modulation (OSM-MBM) joint modulation. The Málaga(M) distribution is used to describe the combined effects of near-ground turbulent light intensity scintillation, beam wander and angle of arrival fluctuation. The closed expression of the bit error rate (BER) of the OSM-MBM joint modulation MIMO terrestrial-satellite laser communication uplink is derived. The simulation analyzes the influence of transmitting radius, receiving aperture, beam divergence, zenith angle and signal-to-noise ratio on the system error performance, and compares it with traditional modulation, media-based modulation and optical space modulation. Finally, the experiment is verified by Monte Carlo. This research provides a theoretical reference for the engineering realization of the modulation technology for the MIMO terrestrial-satellite laser communication uplink system.

A Pulse Position-Based Spatio-Temporal Coded Modulation for Molecular MIMO Systems

Multiple-input multiple-output (MIMO) technology is helpful with improving the communication throughput and performance of molecular communication (MC) systems. Though index modulation (IM) approaches aid to alleviate intersymbol interference (ISI) and interlink interference (ILI) issues in molecular MIMO systems by encoding the information in the antenna index, ISI and ILI problems still exist in such environments. Coded modulation strategies show promising results in terms of system error performance due to their better ISI and ILI combating capability. In this letter, a novel coded modulation scheme is proposed where the pulse position constellation is incorporated with the coded antenna indices. The proposed scheme is shown to yield an improved error performance owing to its better ILI mitigating strength.

Performance analysis and experimental verification of SPAD receivers without photon counting for optical wireless communications

Single photon avalanche diode (SPAD) attracts increasing interests to realize photon-sensitive receivers for optical wireless communications (OWC). In SPAD receivers, the bit information is extracted by photon counting process, which will increase the burden of data processing and storage. To remove complex photon counting process, we propose a scheme of letting recording pulses pass through low-pass finite impulse response (FIR) filter to realize a SPAD receiver without photon counting. Based on the SPAD operation principles, the Monte-Carlo model of SPAD-based OWC system is built and verified with experimental results. Moreover, based on the signal-dependent noise model, a simple and accurate signal estimation and decision algorithm is developed to demodulate the low-pass signal. On this basis, the system error performance under different operation conditions is investigated. The results indicate that utilizing the proposed algorithm, the system error performance is improved 1- to 3-orders of magnitude better than conventional algorithm, which depends on additive Gaussian noise model.

Performance estimation of image transmission in indoor visible light communication system based on variable pulse position modulation

SummaryThe dimming control feature of light‐emitting diode (LED) makes it a viable candidate for indoor lighting applications. In this study, the performance of variable pulse position modulation (VPPM) based visible light communication (VLC) system is investigated in detail for an office room of 5 × 5 × 3‐m3 dimensions. A total of four LED lamps having Lambertian radiation patterns are mounted over the ceiling of the room. Several receiver locations are chosen over the three different trajectories to evaluate the error performance of the proposed system. The height of the receiver plane is also varied to find the optimum height where error‐free data reception is achieved. Moreover, an effort is made to optimize the dimming percentage of the transmitted signal using VPPM in terms of bit error rate (BER), where the illumination requirements over the receiver plane are also as per the International Standards of Organization (ISO). The results show that the duty cycle of 50% is optimum for efficient system performance. Furthermore, a colored image is transmitted through the proposed system and the computed results reveal that satisfactory BER performance and good quality of the image is received at receiver heights ranging from 0.85 to 1.7 m, that is, approximately 2.75 to 5.6 ft above the ground plane.

Transformer-Based Detector for OFDM With Index Modulation

A deep learning (DL)-based detector utilizing the Transformer framework is proposed for orthogonal frequency-division multiplexing with index modulation (OFDM-IM) systems, termed as TransIM. Concretely, TransIM adopts a two-step detection method. First, the neural networks with the Transformer block as the core provide soft probabilities of different transmitted symbols. Then, conventional signal detection methods are performed based on those probabilities to make final decisions. This method is verified to improve system error performance significantly, albeit at the cost of slightly increased complexity. Simulation results indicate that the proposed TransIM detector fares better than existing DL-based ones regarding bit error rate (BER) performance.

Orthogonal frequency division multiplexing system with an indexed-pilot channel estimation

In this paper, we examine an orthogonal frequency division multiplexing (OFDM) system under imperfect channel conditions and pilot-insertion- based channel estimation. However, unlike conventional pilot-insertion-based channel estimation, some inserted pilot symbols are set to zero where the index of the zero-pilot symbols is employed to transmit extra data bits. In this paper, we employ a minimum mean squared error (MMSE) to detect transmitted pilot symbols; these symbols are then used to estimate channel coefficients. Furthermore, the impact of zero-pilot symbols on the mean-squared error of channel estimation and on system error performance is examined. Our findings show that the index of zero-pilot symbols can be used to improve system throughput by carrying extra information bits without harming channel estimation accuracy or degrading system error performance. Simulation results show that, at a high signal-to-noise ratio, the bit error rate for data bits transmitted via zero-pilot symbols index selection is lower than that of data bits transmitted over data subcarriers.

Two‐way decode and forward quadrature media‐based modulation for single‐input multiple‐output scheme

SummaryThe recently proposed quadrature spatial modulation aided single‐input multiple‐output media‐based modulation (QSM aided SIMO‐MBM) improves the spectral efficiency and achieves a high data rate and overall system error performance when compared with conventional SIMO‐MBM and SIMO schemes. Cooperative network (CN) involves collaboration among nodes to improve wireless network reliability, link quality, and spectral efficiency. This paper investigates the performance of QSM aided SIMO‐MBM in CN by employing the decode and forward relaying technique, which utilizes two source nodes that simultaneously transmit a unique message block on the same time slot to the relay node; the relay node decodes the received message block from both transmitting nodes, before re‐encoding and re‐transmitting the decoded message block in the next time slot to the destinations in order to enhance the error performance of the QSM aided SIMO‐MBM further. Each node can decode the data of the other node using network coding (NC) techniques. Algebraic algorithms are applied to the detected message to accumulate the various transmissions. The theoretical average error probability of the proposed scheme was formulated using a lower bound technique, and the Monte Carlo simulation (MCS) results obtained validated the result. The MCS results achieved exhibit a significant improvement of 8 dB at 6 b/s/Hz for a BER of and 12 dB at 8 b/s/Hz for a BER of over the conventional QSM aided SIMO‐MBM scheme. Consequently, the obtained results show that the system configuration with outperforms the system configuration with for the proposed scheme.

Application of Error Correction Codes RS and LDPC to Enhance the Dicode Pulse Position Modulation

Dicode Pulse Position Modulation (DiPPM) has been presented as a new coding technique with several improvements over earlier PPM formats. Few analyses and experimental results have been published because it is a new coding scheme. To overcome the problem of bandwidth utilization in current PPM formats, DiPPM can be employed. The line rate is twice as fast as the original data rate. In order to increase DiPPM's error performance, two types of Forward Error Correction (FEC) codes, Reed-Solomon (RS) code and low-density parity-check (LDPC) code, are investigated in this article. When RS and LDPC function at their optimal parameters, the results show an improvement in DiPPM system error performance. The error performance of an uncoded DiPPM system was compared to that of a DiPPM-encoded LDPC system and a system utilizing the Reed-Solomon algorithm. Transmission efficiency is measured by the number of photons per pulse and bandwidth widening. When the bandwidth is 1x103 times or more than the initial data rate, DiPPM with LDPC code exceeds uncoded DiPPM and DiPPM with RS, using 1.821 x 103 photons per pulse, with a codeword length of 27 and code rate of 0.75.

A novel orthogonal frequency division multiplexing with index modulation waveform with carrier frequency offset resistance and low peak‐to‐average power ratio

SummaryIn this paper, we propose a novel orthogonal frequency division multiplexing (OFDM) scheme with high carrier frequency offset (CFO) resistance and low peak‐to‐average power ratio (PAPR). In this scheme, we consider a hybrid model with two subblock types, namely, pilot subblocks and standard subblocks. In pilot subblocks, active subcarriers are utilized for PAPR reduction while inactive carriers generated by the index modulation (IM) are utilized for the coarse CFO estimation. For standard subblocks, we consider unique subcarrier activation patterns (SAPs) with high‐diversity IM to enhance the bit error performance of the overall system. Additionally, the inactive data tones in standard subblocks are utilized for fine CFO estimation, which enhances the CFO estimation quite significantly. Furthermore, in this paper, we show that proposed hybrid OFDM‐IM (H‐OFDM‐IM) scheme can outperform conventional OFDM‐IM and classical OFDM both in CFO estimation and PAPR reduction without requiring transmission of any side information. Finally, we show both mathematically and through computer simulations that proposed H‐OFDM‐IM can achieve a satisfactory bit error rate (BER) performance under high CFO scenarios.

Space Shift Keying MIMO System for Underwater Acoustic Communication

This paper proposes a space shift keying (SSK) multiple-input multiple-output (MIMO) system for underwater acoustic communication (UWAC). Designing a competent wireless communication for underwater applications is a rebellious task in terms of energy, cost and channel propagation. SSK is considered in RF communication as a very resourceful technique that promises low energy consumption, high data rate, robustness to channel imperfections, and low receiver computational complexity. As well, SSK is implemented without any acoustic modulation chain while relying mainly on audio de–multiplexer for UWAC, which is very simple and basic component. As such, considering SSK for UWAC is envisaged to provide several benefits that will be explored here. The theoretical error performance of the proposed system is analyzed and corroborated through Monte-Carlo simulation results, while considering a κ-μ shadowed fading channel, which is shown in literature to accurately model underwater acoustic propagation. The impact of different system and channel parameters on the SSK-MIMO system performance is investigated. It is revealed that shadowing reduces channel correlation and enhances system performance assuming fixed signal-to-noise ratio values. As well, the considered SSK-MIMO system is shown to achieve a coverage length of around 10km while maintaining an of 10-4.

Pilot-Assisted OFDM for Underwater Acoustic Communication

Multicarrier techniques have made it possible to wirelessly transmit data at higher rates for underwater acoustic (UWA) communication. Several multicarrier techniques have been explored in the past for wireless data transmission. OFDM is known to fight off inter-symbol interference due to the orthogonality of its subcarriers. However, due to time variations, OFDM suffers from intercarrier interference. As the UWA channel is both a time and frequency variant, channel estimation becomes complex. We propose a pilot-based channel estimation technique and explore two equalizers for improving the error performance of an OFDM-based UWA system. Both the equalizers employ pilot subcarriers to estimate the UWA channel. One equalizer is a least squares (LS) equalizer and the other is a zero forcing (ZF) equalizer. Using computer simulations, it is observed that, for an acceptable error performance, the number of pilots should be one-fourth the number of subcarriers. Moreover, if the energy of the pilots is increased without changing the overall symbol energy, the error performance degrades. It is also noted that both the LS and ZF equalizers give an acceptable error performance with the ZF performing marginally better than the LS. Furthermore, the error performance of the proposed system is evaluated as a function of the transmitter-receiver distance and an acceptable error performance is observed even at 1250 m.