Equal Gain Combining Research Articles

Robust cooperative spectrum sensing in cognitive radio blockchain network using SHA-3 algorithm

Cognitive radio network (CRN) uses the available spectrum resources wisely. Spectrum sensing is the central element of a CRN. However, spectrum sensing is susceptible to multiple security breaches caused by malicious users (MUs). These attackers attempt to change the sensed result in order to decrease network performance. In our proposed approach, with the help of blockchain-based technology, the fusion center is able to detect and prevent such criminal activities. The method of our model makes use of blockchain-based MU detection with SHA-3 hashing and energy detection-based spectrum sensing. The detection strategy takes place in two stages: block updation phase and iron out phase. The simulation results of the proposed method demonstrate 3.125%, 6.5%, and 8.8% more detection probability at −5 dB signal-to-noise ratio (SNR) in the presence of MUs, when compared to other methods like equal gain combining (EGC), blockchain-based cooperative spectrum sensing (BCSS), and fault-tolerant cooperative spectrum sensing (FTCSS), respectively. Thus, the security of cognitive radio blockchain network is proved to be significantly improved.

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 Centralized Cooperative Schemes for Compressed Sensing.

This paper presents a performance analysis of centralized spectrum sensing based on compressed measurements. We assume cooperative sensing, where unlicensed users individually perform compressed sensing and send their results to a fusion center, which makes the final decision about the presence or absence of a licensed user signal. Several cooperation schemes are considered, such as and-rule, or-rule, majority voting, soft equal-gain combining (EGC). The proposed analysis provides simplified closed-form expressions that calculate the required number of sensors, the required number of samples, the required compression ratio, and the required signal-to-noise ratio (SNR) as a function of the probability of detection and the probability of the false alarm of the fusion center and of the sensors. The resulting expressions are derived by exploiting some accurate approximations of the test statistics of the fusion center and of the sensors, equipped with energy detectors. The obtained results are useful, especially for a low number of sensors and low sample sizes, where conventional closed-form expressions based on the central limit theorem (CLT) fail to provide accurate approximations. The proposed analysis also allows the self-computation of the performance of each sensor and of the fusion center with reduced complexity.

Gain of Spatial Diversity with Conjoint Signals in Arbitrarily Correlated Rayleigh Fading Channels

Coding gains for arbitrarily correlated signals in a spatial diversity system with conjoint signals are presented in this study. The basic form of the proposed signal synthesizer evenly produces phase changes in the output signals. The mixer is an orthogonal transformation matrix, which is energy preserving and blind to the channel correlation matrix. The idea is to synthesize additional conjoint signal copies from the received signals that would be received if there were more antennas. However, these conjoint signals contain a level of correlation with the received signals. With the assumption of flat Rayleigh fading channels, simulation results for symbol error probability (SEP) are presented for different numbers of receive branches and varying correlation conditions. It is shown that under binary phase shift keying (BPSK), the synthesizer achieves decorrelation coding gains of about 1 dB when selection combining (SC) or equal gain combining (EGC) is used. The synthesizer’s performance across M-ary quadrature amplitude modulation (MQAM) signals is also tested. In addition, analytical frameworks are derived for BPSK and MQAM, which are tightly bound by the Monte Carlo simulation results obtained using Matlab. The correlation analysis is performed for different numbers of antennas and varied antenna spacings.

Optimizing Nonlinear Distortion and Interference in MC-CDMA Receivers Employing Deep Neural Networks

Systems that employ multicarrier code division multiple access, commonly known as MC-CDMA, produce outstanding results in terms of both the performance of the system as a whole and the efficiency with which it uses the spectrum. However, multiple access strategies are susceptible to interference despite their high spectrum efficiency. This work aims to reduce multiple access interference (MAI) by developing an MC-CDMA receiver. When MC-CDMA deteriorates nonlinearly, standard receivers, namely, zero forcing (ZF), maximal ratio combining (MRC), minimum mean square error (MMSE), and equal gain combining (EGC), are unable to cancel MAI. Neural network (NN) receivers are a better option due to their nonlinear nature. Based on the simulation results, the suggested deep neural network- (DNN-)based schemes outperform the current baselines in terms of error handling and usability. This research explores the viability and effectiveness of a DNN-based receiver designed for MC-CDMA with nonlinearity degradations. The focus of this research is on MC-CDMA.

Utilizing double-shadowed Rician fading over energy detector-based spectrum sensing with diversity reception

This study explores the capabilities of an Energy Detector (ED)-based Cognitive Radio (CR) device in a double shadowed (DS) Rician distribution environment for spectrum sensing. The effectiveness of the ED is evaluated using metrics such as average probability of detection (PD) and average area under the receiver operating characteristics curve (AUC). The investigation extends to single-input-multiple-output (SIMO) channel conditions, considering maximal ratio combining (MRC) and square-law selection (SLS) diversity techniques. To provide a comprehensive understanding of the system, the study also includes the asymptotic performance analysis of diversity techniques, including MRC, equal gain combining (EGC), and selection combining (SC). The findings indicated a notable enhancement in detection performance through the application of diversity combining techniques. Among the evaluated schemes, MRC demonstrated the most favorable results, followed EGC, while SC yielded comparatively weaker outcomes. To further minimize error probability, the detection threshold is optimized, resulting in improved energy detection statistics, even in scenarios involving diversity. The formulations are additionally applied to cooperative spectrum sensing (CSS). It further noted that fading parameter directly influence the array gain, while diversity gain only depends on the number of diversity branches. The accuracy and validity of the proposed results are confirmed through Monte-Carlo simulation.

Deep learning based BER improvement for NOMA-VLC systems with perfect and imperfect successive interference cancellation

This paper focuses in the improvement of the BER performance of multiple-input multiple-output (MIMO) systems is investigated utilizing non-orthogonal multiple access-visible light communication (NOMA-VLC). Applying multi-user downlink MIMO-NOMA-VLC system within equal gain combiner at the receiver is used with two types of modulation; On–Off Keying (OOK) and L-Pulse Position Modulation, with L = 4 and 8. The perfect and imperfect successive interference cancellation scenario is used in this system, and the scenario is considered for two and three users. Our proposed framework is divided into two stages. First, data is collected using the MATLAB software. Second, two deep learning models (DLMs); ResNet50V2 and InceptionResNetV2 which are trained and tested. Python software is then used to develop and train the DLMs. The obtained results assures the superiority of ResNet50V2 over InceptionResNetV2, in different cases and for all users. The BER performance is also studied versus α for two and three users OOK modulation single-input single-output (SISO), (2 × 2) and (3 × 2) MIMO-NOMA-VLC systems based on the two DL techniques; ResNet50V2 and InceptionResNetV2. Again, ResNet50V2 achieves better results than InceptionResNetV2. The obtained results are compared with the previously published ones, showing that the proposed system and techniques achieve better results.

Comparison of the Combining Methods Used In Space Diversity

The basic concept of diversity; where two or more inputs at the receiver are used to get uncorrelated signals. The aim of this paper is an attempt to compare some possible combinations of diversity reception and MLSE detection techniques. Various diversity combining techniques can be distinguished: Equal Gain Combining (EGC), Maximal Ratio Combining (MRC), Selection Combining and Selection Switching Combining (SS).The simulation results shows that the MRC give better performance than the other types of combining (about 1 dB compare with EGC and 2.5~3 dB compare with selection and selection switching combining).

Identity-based attack detection using received signal strength in MIMO systems

This paper proposes RSS-based multiple-input multiple-output (MIMO) receiver diversity-combining techniques for identity-based attack detection. The diversity-combining techniques considered for identity-based attack detection using MIMO systems include selection combining (SLC), equal gain combining (EGC), and maximal ratio combining (MRC). First, we exploit the spatial correlation of the RSS hereditary from wireless nodes to detect identity-based attacks. Analytical expressions of the proposed method for the spatial correlation of the RSS hereditary using MIMO-combining diversities are provided and validated through simulation results. Second, we propose unsupervised machine learning (ML) algorithms such as k-means and k-medoids for the detection of identity-based attacks using RSS with different MIMO-combining diversities. Complete statistical derivations for the detection of identity-based attacks using k-means and k-medoids algorithms were performed. The simulation results confirm that the proposed techniques exploiting MIMO diversity-combining techniques for identity-based attack detection using unsupervised ML algorithms outperform the previously proposed techniques in terms of the false positive rate (FPR) and detection rate (DR). Furthermore, the simulation showed that the EGC-combining diversity with k-means and k-medoids outperformed the SLC- and MRC-combining techniques.

Secrecy outage probability and limiting threshold criteria in an optimal SNR regime by maximizing desired transfer rate

In this paper, the optimum secrecy probability has been calculated using a reduction function that optimizes the transfer rate of the user's signal for a given average broadcast power while minimizing the transfer rate of the eavesdropper's signal to ensure safe transmission. In this work, the signal-to-noise ratio (SNR) of the eavesdropper signal and the received signal are accurately estimated using matrix theory. These approximated SNRs have been studied in relation to the outage probability. By making three distinct assumptions about channel correlation, it has been possible to determine the precise secrecy outage probability. In correlated multi-antenna transmit and receive channels, this research investigates the secrecy performance of three popular diversity combining strategies—maximum ratio combining (MRC), selection combining (SC), and equal gain combining (EGC). In this research, we consider a Rayleigh fading channel with overhead communication between the transmitter and recipient. In this research, we also propose a limiting bounds condition to improve the limits on the outage probability for the Rayleigh fading environment using the three diversity combining methods. Our restricting distribution is threshold-based in order to generate precise limits on the probability of secrecy outage. An application case has been presented which discusses the impact of the proposed model for device to device communication application scenario. Our findings demonstrate that channel correlation substantially influences the probability of a secrecy outage.

On the Performance of LDPC-Coded Large Intelligent Antenna System

This article studies Large Intelligent Systems (LIS) along with Single Carrier with Frequency Domain Equalization (SC-FDE), utilizing Low-Density Parity-Check (LDPC). Four different receivers are studied in the scenarios described above, namely Equal Gain Combining (EGC), Maximum Ratio Combining (MRC), Zero Forcing (ZF), and Minimum Mean Squared Error (MMSE). The results of this article show that the use of LDPC codes leads to an improvement of performance by about 2 dB for a 4X25 LIS system and by 3 dB for a 4X225 LIS system, as compared to similar systems without LDPC codes. Moreover, for all simulations, the MMSE receiver achieves the best overall performance, while EGC performs the worst.

Reliability analysis of optical IRS-enabled FSO system with multiple detectors and PCB under composite turbulence fading channels considering the impact of GML

Free space optical (FSO) communication with optical intelligent reflecting surface (IRS) assistance is one promising and evolving technology that can relax the line-of-sight requirement and enable more efficient and reliable link performance in obstacles areas. In this work, an optical IRS-enabled FSO system is proposed with partially coherent beam (PCB) and multiple detectors. Specifically, for an end-to-end (e2e) IRS-assisted FSO link, the statistical model of optical signal fluctuations due to atmospheric turbulence is assumed to follow Fisher–Snedecor F-distribution, and the random movements of IRS, transmitter (Tx), and receiver (Rx) due to building sway is modeled by geometric and misalignment losses. Considering the Gaussian–Schell model and intensity modulation/direct detection, the analytical average bit error rate (ABER) expressions of the studied system are obtained for a single detector and multiple detectors, respectively, with selected combining (SC), equal gain combining (EGC) and maximum ratio combining (MRC) aperture diversity schemes over independent identically distributed composite fading channels. And the correctness of the analytical results is verified through the Monte-Carlo based statistical simulation method. Results show that the ABER and outage probability performance of IRS-assisted FSO link degrades with the increase in the strength of atmospheric turbulence and building sway. And even the position fluctuations variances of Tx, IRS, and Rx are the same, their impacts on the e2e IRS-assisted FSO link are not the same. Interestingly, aperture diversity techniques can significantly mitigate these adverse effects, especially in the case of MRC scheme. Besides, the studied system with PCB can achieve better system performance compared to that using coherent beam, and the performance gap would become more obvious as the spatial coherence radius decreases. This work could serve as a guide for the design and research of IRS-enabled FSO communication systems.

Error performance of an L-PPM modulated ADR-based MIMO-VLC system with and without channel estimation error.

In recent years, visible light communication (VLC) has emerged as a potential technique for beyond 5G communication networks. In this study, an angular diversity receiver (ADR) is used to propose a multiple-input multiple-output (MIMO) VLC system employing L-pulse position modulation (L-PPM). Repetition coding (RC) is used at the transmitter, while receiver diversity techniques such as maximum-ratio combining (MRC), selection best combining (SBC), and equal gain combining (EGC) are used at the receiver to improve performance. This study presents the exact probability of error expressions for the proposed system with and without channel estimation error (CEE). The analysis shows that the probability of error of the proposed system increases as the estimation error increases. Further, the study shows that the increase in signal-to-noise ratio is not enough to counter the impact of CEE, especially when the estimation error is large. The distribution of error probability of the proposed system using EGC, SBC, and MRC throughout the area of the room is presented. The simulation findings are compared to the analytical results.

On the Performance of Decode-and-Forward Equal-Gain-Combining Relay Systems over Weibull Fading Channels

Relay-assisted wireless communications, where both the relay and the final destiny employ diversity-combining techniques, represent a compelling strategy for improving the signal-to-noise ratio (SNR) for mobile terminals, mainly at millimeter-wave (mmWave) frequency bands. In this sense, this work considers a wireless network that employs a dual-hop decode-and-forward (DF) relaying protocol, in which the receivers at the relay and at the base station (BS) use an antenna array. Moreover, it is considered that the received signals are combined at reception using equal-gain-combining (EGC). Recent works have enthusiastically employed the Weibull distribution so as to emulate the small-scale fading behavior in mmWave frequencies, which also motivates its use in the present work. For this scenario, exact and asymptotic expressions for the system's outage probability (OP) and average bit error probability (ABEP) are derived in closed form. Useful insights are gained from these expressions. More precisely, they illustrate how the system and fading parameters affect the performance of the DF-EGC system. Monte Carlo simulations corroborate the accuracy and validity of the derived expressions. Furthermore, the mean achievable rate of the considered system is also evaluated via simulations. Useful insights regarding the system performance are obtained from these numerical results.

Performance analysis of coherent DPSK SIMO laser-based satellite-to-ground communication link over weak-to-strong turbulence channels considering Kolmogorov and non-Kolmogorov spectrum models

The performance of satellite-to-ground laser-based communication links is highly affected by atmospheric turbulence. Coherent detection with spatial diversity at the ground station receiver can mitigate the scintillation effects caused by atmospheric turbulence. Traditionally, the scintillation effects are modeled based on the Kolmogorov spectrum model. However, the experiments have indicated that scintillation effects on the laser beam propagation have non-Kolmogorov properties. Our goal in the present work is to analyze the average bit error rate (BER), outage probability (OP), and ergodic capacity of the satellite-to-ground heterodyne optical communication system with receiver spatial diversity. A differential phase-shift keying modulation technique is considered in this work. The propagated laser signal from the satellite to the ground station is assumed to be subjected to Málaga-distributed atmospheric turbulence. The atmospheric turbulence statistics are carried out based on the conventional Kolmogorov spectrum model and the three-layer altitude (TLA) non-Kolmogorov spectrum model. The performance of popular diversity combining techniques, namely, maximum ratio combining (MRC) and equal gain combining (EGC) techniques are analyzed. The statistical models of the MRC technique under the Málaga-distributed atmospheric channel model are obtained in analytical form expressions. The statistical models of the EGC technique under the Málaga-distributed atmospheric channel model are obtained via the fast Fourier transform representation of the characteristic function method. Based on these statistical models, average BER, OP, and ergodic capacity expressions for each type of diversity combining technique are derived. For the communication system under investigation, the performance of MRC and EGC multiple aperture receiver systems are compared to a single aperture receiver with the same total aperture area. These comparisons are carried out under the same conditions in terms of zenith angle and signal-to-noise ratio. The obtained results show that the performance of the optical communication system under investigation with MRC and EGC receivers can be improved by increasing the order of diversity. In addition, it is found that the difference in the performance between Kolmogorov and TLA non-Kolmogorov spectrum models is not significant at low zenith angles, while this difference increases as the zenith angle increases. All numerical results are verified by Monte-Carlo simulations.

A simplified mode diversity coherent receiver based on non-mode-selective photonic lantern and Kramers-Kronig detection

This paper proposes a mode-diversity space optical communication receiver for long-range space optical communication, which can compensate for the effect of atmospheric turbulence and be applied between 2 km and 16 km space optical communication with a low-cost, low-power and low-complexity feature. The receiver uses a non-mode selective photonic lantern as a mode demultiplexer, merging using an equal gain combining (EGC) algorithm and a Kramers-Kronig (KK) detection technique to accomplish the optical detection of high-dimensional modulated format signals. The performance of the receiver under different turbulent conditions is experimentally investigated, showing significant compensation for atmospheric turbulence. The experimental results show that the proposed scheme achieves a gain of 4–5 dB at BER = 3 × 10−3 compared to a single-mode fiber (SMF) receiver under moderately strong turbulent conditions.

Free-Space Optical Communication Based on Mode Diversity Reception Using a Nonmode Selective Photonic Lantern and Equal Gain Combining

This paper experimentally investigates the perform-ance of free-space optical (FSO) communication based on mode diversity reception (MDR) using nonmode selective photonic lantern (NSPL) and equal gain combining (EGC). By employing a mode demultiplexer and combining technology in the receiver, the bit error rate (BER) and outage performance of FSO communication system can be significantly improved. However, different from diversity system with multiple receive apertures, the branches in mode diversity system are non-independent fading signals, which are influenced by not only atmospheric but also the modal crosstalk of mode demultiplexer. Therefore, we take into consideration the difference of mode demultiplexer and study four schemes for FSO mode diversity reception system: 1) NSPL with equal gain combining (NSPL-EGC), 2) NSPL with maximal ratio combining (NSPL-MRC), 3) mode selective photonic lantern with equal gain combining (MSPL-EGC), and 4) mode selective photonic lantern with equal gain combining (MSPL-MRC). Experimental results show that NSPL-EGC is the most suitable scheme for MDR with low implementation complexity, and the performance difference is less than 1 dB compared with the one using MRC at BER = 3.8×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> under turbulence from weak to strong.

English

The spatial diversity techniques are broken down and explained systematically along with its combination which includes Maximum Ratio Combining (MRC), Equal Gain Combining (EGC) and Simple Selection Combining (SC) under the influence of atmospheric-induced turbulence fading in Free Space Optical (FSO) communication. Diversity is a technique used to prevent or reduce multipath. Multipath is a phenomenon describing propagation that results in the signals reaching the antenna by two or more paths. There is an extreme difficulty for a transmitted signal to be detected by a receiver in a case of increased turbulence. This research provides a forum for the receiver with some forms of diversity. The validation of the recommended simulation is through Additive White Gaussian Channel without combiner of the same process. The results display that Maximum Ratio Combining (MRC) has the greatest mitigation level of fading in comparison with others. Consequently, where fading is more dominant like on a terrestrial FSO link, Maximum Ratio Combining (MRC) can be used. Overall, the findings suggest the capability of the model in mitigating atmospheric turbulence especially for the 5G wireless networks in the terrestrial link. Key words: Free Space Optical Communication (FSO), Atmospheric Turbulence, Additive White Gaussian Channel (AWGC), Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), Selection Combining (SC) and Additive White Gaussian Noise (AWGN).

Performance Evaluation of Space Receive Diversity Techniques for Massive MIMO System

This paper presents performance evaluation of massive MIMO system in terms of signal to noise ratio (SNR) and system capacity with respect to increasing number of receive antennas at the base station for a wireless communication between a single transmit antenna of user terminal per time. The analysis performed in MATLAB simulation environment revealed that for M = 128, 256, and 512, the SNR improvement in dB achieved using selective combining (SC) was 7.31, 7.85, and 8.34 respectively, whereas for equal gain combining (EGC) and maximal ratio combining (MRC) the SNRs performance in dB were 19.79 and 20.83, 22.95 and 24, and 25.96 dB, and 27 respectively. Generally, the outcomes of simulations have proven that optimizing the number of receive antenna based on selection by changing the number of antennas at base station (BS) can provide improved SNR and system capacity.

Improvement of Multiple Antenna Sensing Technique for Detecting the White Space in a Spectrum Sharing System

Exact detection of White Space (WS) is one of the actions in a Spectrum Sharing System (SSS) to determine unused spectrum for proper utilization. However, exact detection of WS is being affected by channel impairments, resulting in harmful interference. The Existing Multiple Antenna Spectrum Sensing (EMASS) technique used in addressing this effect is characterized with noise uncertainty leading to low detection rate due to setting of thresholds that is based on noise variance. Hence, this paper proposes an Improved Multiple Antenna Spectrum Sensing (IMASS) for detecting the WS in a SSS. Various copies of licensed user’s signals are received through the unlicensed user antennas over different antenna configuration. The received signals are combined using a modified equal gain combiner and energy of the combined signal is determined using Parseval’s relation for a discrete time signal. The received signal is used to form a square matrix which is converted to covariance matrix. Characteristic equation is obtained from covariance matrix to determine the minimum eigenvalue. The ratio of energy to minimum eigenvalue of the received signal is obtained and used as test statistics. The IMASS technique is evaluated using Probability of Detection (PD) and Total Error Probability (TEP) by comparing with EMASS. The proposed IMASS technique gives better performance with higher PD and lower TEP values than EMASS at all different antenna configurations.