Selection Combining Diversity Research Articles

Exploiting FAS for Cooperative NOMA-based Full-duplex mmWave Networks with Imperfections

The primary constraints inherent in the millimeter wave (mmWave) technology manifest as high path loss and limited range. As a result, a line-of-sight environment is necessary for a seamless connection between source and destination nodes. At the same time, the prevalence of intervening obstacles becomes increasingly pronounced, owing to the escalating densification of contemporary wireless networks. We address these inherent challenges by exploring the aid of non-orthogonal multiple access (NOMA) and fluid antenna system (FAS) technologies. Our proposed approach centers around deploying an N-user NOMA network for optimizing the base station’s resources and facilitating cooperative full-duplex communication. Furthermore, the integration of L-port FAS elevates the quality-of-service by designing a flexible and compact antenna tailored to meet the needs of mobile users. Most works ignore the imperfections of transceiver hardware that is critical for high-rate communication systems. In this work, we have considered both ideal and non-ideal transceiver hardware to analyze the importance of practical systems. The findings indicate that ten-port FAS performs better than the selection-combining diversity. Still, it necessitates approximately 600 ports to surpass the capabilities of a four-antenna maximum-ratio-combining scheme. Ultimately, we formulate the expressions for outage probability, considering residual self-interference, residual transceiver hardware impairment noise, and interference, and corroborate these expressions through Monte Carlo simulations.

UER of various modulation schemes over SC diversity with GGD noise for EMNC

ABSTRACT Electromagnetic nano communication (EMNC) is an evolving field of modern communication technology. Terahertz imaging, sensing, food safety and security, quality control and simultaneous localisation and mapping, which all together make it a suitable use case for 6 G, are the most lively applications of EMNC. This manuscript proposes unified expressions of error rate under different modulation schemes for EMNC. For this, mixture gamma (MG) fading distribution, including almost all the fading channels, under dual selection combining (SC) diversity is developed and employed. Also, generalised Gaussian distribution (GGD), which is appropriate for the EMNC system under an aqueous medium, is employed in the analysis. Specifically, analytical expressions for BER of BPSK, M-PAM and M-QAM schemes over MG fading under dual SC diversity are derived in the presence of GGD noise. Proposed analytical expressions are numerically compared with those available in the literature without SC diversity. Comparison shows that irrespective of the value of fading severity ‘’ and/or noise shaping parameter ‘’, dual SC offers a significant improvement in BER. It is most important to mention that proposed expressions are unified in nature because a variety of results can be reproduced for different values of ‘’ and ‘’.

Selection Combining Scheme Over Non-Identically Distributed Fisher-Snedecor F Fading Channels

In this letter, the performance of the selection combining (SC) scheme over independent and non-identically distributed (i.n.i.d.) Fisher-Snedecor <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> fading channels is analysed. Accordingly, the probability density function (PDF) and the moment generating function (MGF) of the maximum of i.n.i.d. Fisher-Snedecor <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> variates are derived first. Based on these statistics, the exact expression and the asymptotic behaviour at high average signal-to-noise ratio value of the average bit error probability (ABEP), the normalised average channel capacity (ACC), and the average area under the receiver operating characteristics curve (AUC) of the energy detection based spectrum sensing with i.n.i.d. SC diversity receivers are provided. To validate our analysis, the numerical results are compared with the Monte Carlo simulations.

Secrecy Outage Performance of Cognitive Radio Network with Selection Combining at Eavesdropper

Background: Based on the idea of cooperative communication, recently a lot of attention has been drawn to cooperative spectrum access for the secure information transmission in a Cognitive Radio Network (CRN). Security is one of the most important aspects of these networks, as due to their open and dynamic nature, they are extremely vulnerable to malicious behavior. Cooperative cognitive radio has emerged as a dynamic spectrum access technique, where an unlicensed (secondary) user is allowed to simultaneously access the licensed channels dedicated to a Primary User (PU), as long as the Quality of Service (QoS) of primary communication is not affected. Method: This paper investigates the secrecy outage performance of threshold-based cognitive decode-andforward relay network, with interference constraints from primary licensed user. Threshold-based relaying is considered where; the source message is successfully decoded by the relay, only if the received SNR satisfies the particular threshold. Outage probability expressions have been derived for the worst-case scenario, where only the eavesdropper can achieve the advantage of diversity. The Selection Combining (SC) diversity scheme is employed only at the secondary eavesdropper. Results: The system secrecy performance is better for SC diversity scheme at the eavesdropper than Maximal Ratio Combining (MRC) diversity scheme, as MRC has better diversity performance than SC. We have shown that the improvement in desired secrecy rate, predetermined threshold, eavesdropper channel quality and interference constraints affect the secrecy performance of the cognitive radio system. The outage probability decreases accordingly with an increase in the maximum tolerable interference level at primary destination. The outage probability of Optimal relay Selection (OS) scheme is derived for a multi-relay system, when either the Instantaneous Channel State Information (ICSI) or the Statistical Channel State Information (SCSI) is available. We have shown that the secrecy performance of the OS with ICSI of the system is better than with SCSI. Also, the OS improves the performance of the multi-relay system, when the number of relays is increased. Conclusion: The secrecy outage probability of threshold-based DF underlay cognitive relay network is evaluated. Both interference and maximum transmit power constraints are considered at secondary source and secondary relay. Also, the relay can successfully decode the message, only if it meets the pre-defined threshold. We have investigated the performance of MRC and SC diversity schemes at the secondary eavesdropper and have shown that the system secrecy performance is better for SC than MRC, as MRC has better diversity performance than SC. We have shown that the system secrecy performance is significantly affected by the required secrecy rate, pre-defined threshold, interference constraints and choice of diversity scheme (MRC/SC) at the eavesdropper. The outage probability of OS scheme is derived for a multi-relay system, when either the ICSI or the SCSI is available. We have shown that the secrecy performance of the OS with ICSI of the system is better than with SCSI. Also, the OS improves the performance of the multi-relay system, when the number of relays is increased.

Error probability and channel capacity analysis of wireless system over inverse gamma shadowed fading channel with selection diversity

SummaryIn this paper, we present an analytical framework to analyse the error probability and the channel capacity of the inverse gamma (I‐Gamma) shadowed fading channel. First, the work discusses the utility of the I‐Gamma over log‐normal (LN) and gamma fading models where the closeness of I‐Gamma with other existing shadowing models is carried out. Utilising the probability density function (PDF) of the I‐Gamma shadowed fading channel, various metrics of the communication system, namely, the average symbol error probability (SEP), the channel capacity under optimal rate adaptation (ORA), channel inversion with fixed rate (CIFR), and truncated CIFR (TIFR) are derived. Further, the work is extended to derive a novel selection combining (SC) PDF, and the analytical results for the SEP and the channel capacity of SC diversity are presented. Furthermore, we also provide simpler asymptotic expressions for the average SEP. In addition, the simplified high and low signal‐to‐noise‐ratio (SNR) solutions to channel capacity are also provided. The derived mathematical formulations have been endorsed by comparing with Monte Carlo simulations.

Performance analysis of repeated index modulation for OFDM with MRC and SC diversity under imperfect CSI

In this paper, we conduct the investigation into the performance of repeated index modulation-orthogonal frequency division multiplexing (RIM-OFDM) system with spatial diversity comprising the maximal ratio combining (MRC) and selection combining (SC). The considered systems, abbreviated as RIM-OFDM-MRC and RIM-OFDM-SC, are successful in exploiting both the frequency and spatial diversities to provide improvement in the error performance of the conventional IM-OFDM system with diversity reception. We find out the closed-form expressions for the index and symbol error probabilities of RIM-OFDM-MRC and RIM-OFDM-SC under a variety of different channel conditions. We also carry out asymptotic analysis in order to examine the system behavior under influences of system parameters and the imperfection in channel state information (CSI). Performance evaluation through both theoretical and simulation results demonstrates the significant performance improvement of our systems in comparison with the conventional IM-OFDM using MRC/SC even when channel estimation errors occur at the receiver.

Performance Analysis of a Selection Combining System That Uses the Minimal Interference Algorithm

In this paper, a new combining algorithm for selection combining (SC) receiver based on selection of diversity branch with the lowest interference is proposed. The system used for analysis consists of dual-branch SC diversity that operates over correlated Weibull fading channels. Closed-form expressions for joint probability density function (PDF) of desired signal and interference at the output and PDF of instantaneous signal-to-interference ratio (SIR) at the output are obtained and used to investigate important system performance indicators. System performance is analyzed using outage probability, average bit error probability (ABEP) and average output SIR. The obtained results are compared with the previously published for the SIR algorithm employed by the same system.

Impact of Interbranch Correlation on Multichannel Spectrum Sensing With SC and SSC Diversity Combining Schemes

Multiantenna receivers are often deployed in cognitive radio systems for accurate spectrum sensing. However, correlation among signals received by multiple antennas in these receivers is often ignored which yields unrealistic results. In this paper, the effect of this correlation is accurately quantified by deriving analytical expressions for the average probability of detection. Alternative simpler expressions are also derived. These are done for selection combining (SC) and switch and stay combining (SSC) diversity techniques in dual arbitrarily correlated Nakagami- $m$ fading channels. Then, it is repeated for triple exponentially and identically correlated Nakagami- $m$ fading channels with SC diversity technique. Analysis results show that the interbranch correlation impacts the detector performance significantly, especially in deep fading scenarios. Also, SC outperforms SSC as expected. However, the difference between them becomes very small in low fading and highly correlated scenarios, which indicates that the simpler SSC scheme can as well be deployed in such situations.

A new closed-form of ASEP and channel capacity with MRC and selection combining over Inverse Gaussian shadowing

This paper analyse and investigate the performance of communication system with maximal ratio combining (MRC) and selection combining (SC) over Inverse Gaussian (IG) fading distribution. All formats of coherent and non-coherent modulation schemes are considered and novel analytical expressions of average symbol error probability (ASEP) with diversity are derived. Gamma and IG fading distributions are popularly used as a mathematically less complex solution to lognormal in the open literature. Hence, we provide a comparative analysis between IG and gamma fading with the aim to provide a quantitative measure of the difference between the two distributions in the context of ASEP. Moreover, the novel closed-form expressions of channel capacity under transmission schemes such as optimal rate adaptation (ORA) and channel inversion fixed rate (CIFR) are derived and analysed with MRC and SC diversity over IG fading. The analytical results have been validated with the Monte Carlo simulations and the exact numerical results.

Ergodic Channel Capacity for Rayleigh Fading Channels with Impairments Due to Errors in M-Branch Hybrid Diversity Combining

Novel closed-form expressions are derived for Ergodic channel capacity for fading channels with impairments due to combining errors for M-branch Rayleigh fading with Generalized Diversity Combining. Four different adaptation policies are analyzed for (1) maximal ratio combining (MRC) diversity, (2) spread spectrum (SS) diversity with MRC and Antenna diversity with selection combining (SC), and (3) SS diversity with SC and Antenna diversity with MRC diversity reception cases. Correlation is defined physically as the similarity between the channel coefficients of the pilot and the message. If the pilot and the message are highly correlated, we have a high system performance. Optimal power and rate adaptation policy yields the best spectrum efficiency, while channel inversion with fixed rate policy suffers the highest penalty in comparison to other policies.

Performance Analysis of the Link-Adaptive Cooperative Amplify-and-Forward Relay Networks with Opportunistic Relaying Strategy

This paper analyzes the performance of cooperative amplify-and-forward (CAF) relay networks that employ adaptive M-ary quadrature amplitude modulation (M-QAM)/M-ary phase shift keying (M-PSK) digital modulation techniques in Nakagami-m fading channel. In particular, we present and compared the analysis of CAF relay networks with different cooperative diversity and opportunistic routing strategies such as regular Maximal Ratio Combining (MRC), Selection Diversity Combining (SDC), Opportunistic Relay Selection with Maximal Ratio Combining (ORS-MRC) and Opportunistic Relay Selection with Selection Diversity Combining (ORS-SDC). We advocate a simple yet unified numerical approach based on the marginal moment generating function (MGF) of the total received SNR to compute the average symbol error rate (ASER), mean achievable spectral efficiency, and outage probability performance metrics.

Spectral efficiency of dual diversity selection combining schemes under correlated Nakagami-0.5 fading with unequal average received SNR

The spectral efficiency results for different adaptive transmission schemes over correlated diversity branches with unequal average signal to noise ratio (SNR) obtained so far in literature are not applicable for Nakagami-0.5 fading channels. In this paper, we investigate the effect of fade correlation and level of imbalance in the branch average received SNR on the spectral efficiency of Nakagami-0.5 fading channels in conjunction with dual-branch selection combining (SC). This paper derived the expressions for the spectral efficiency over correlated Nakagami-0.5 fading channels with unequal average received SNR. This spectral efficiency is evaluated under different adaptive transmission schemes using dual-branch SC diversity scheme. The corresponding expressions for Nakagami-0.5 fading are considered to be the expressions under worst fading conditions. Finally, numerical results are provided to illustrate the spectral efficiency degradation due to channel correlation and unequal average received SNR between the different combined branches under different adaptive transmission schemes. It has been observed that optimal simultaneous power and rate adaptation (OPRA) scheme provides improved spectral efficiency as compared to truncated channel inversion with fixed rate (TIFR) and optimal rate adaptation with constant transmit power (ORA) schemes under worst case fading scenario. It is very interesting to observe that TIFR scheme is always a better choice over ORA scheme under correlated Nakagami-0.5 fading channels with unequal average received SNR.

Performance analysis of satellite‐to‐ground downlink optical communications with spatial diversity over Gamma–Gamma atmospheric turbulence

The performances of satellite‐to‐ground downlink optical communications over Gamma–Gamma distributed turbulence are studied for a multiple‐aperture receiver system. Equal gain‐combining (EGC) and selection‐combining (SC) techniques are considered as practical schemes to mitigate the atmospheric turbulence under thermal‐noise‐limited conditions. Bit‐error rate (BER) performances for on‐off keying‐modulated direct detection and outage probabilities are analyzed and compared for SC diversity receptions using analytical results and for EGC diversity receptions through an approximation method. To show the net diversity gain of a multiple‐aperture receiver system, BER performances and outage probabilities of EGC and SC receiver systems are compared with a single monolithic‐aperture receiver system with the same total aperture area (same average total incident optical power) for satellite‐to‐ground downlink optical communications. All the numerical results are also verified by Monte‐Carlo simulations.

Performance analysis of satellite-to-ground downlink coherent optical communications with spatial diversity over Gamma-Gamma atmospheric turbulence.

The performances of satellite-to-ground downlink optical communications over Gamma-Gamma distributed atmospheric turbulence are studied for a coherent detection receiving system with spatial diversity. Maximum ratio combining (MRC) and selection combining (SC) techniques are considered as practical schemes to mitigate the atmospheric turbulence. Bit-error rate (BER) performances for binary phase-shift keying modulated coherent detection and outage probabilities are analyzed and compared for SC diversity using analytical results and for MRC diversity through an approximation method with different numbers of receiving aperture each with the same aperture area. To show the net diversity gain of a multiple aperture receiver system, BER performances and outage probabilities of MRC and SC multiple aperture receiver systems are compared with a single monolithic aperture with the same total aperture area (same total average incident optical power) for satellite-to-ground downlink optical communications. All the numerical results are verified by Monte-Carlo simulations.

Optimal Detection Thresholds in Spectrum Sensing with Receiver Diversity

We investigate the performance of receiver diversity techniques by considering energy detector based optimal spectrum sensing in cognitive radio networks over Rayleigh fading channel for both non-cooperative and cooperative communication systems. The analysis is first focused on the non-cooperative spectrum sensing part, including the analyses of selection combining (SC), equal gain combining (EGC), and maximal ratio combining (MRC) receiver diversity systems. We derive exact closed-form expressions for the optimal detection thresholds for each diversity scheme. By using these expressions, we present their detection performance compared to the no-diversity case. Then in the second part of this paper, the performance analysis of the proposed system is investigated for amplify-and-forward relaying spectrum sensing with SC, EGC, and MRC diversity techniques in Rayleigh fading channels. Particularly, average detection probability of end-to-end signal-to-noise ratio for SC and EGC schemes and the exact closed-form expressions of the optimal detection threshold for SC, EGC, and MRC schemes are derived. We also present detection performance for the cooperative system compared to the non-cooperative one. The analyses are validated by simulated receiver operating characteristic curves.

Performance Analysis of Energy Detector Over $$\alpha -\mu $$ α - μ Fading Channels with Selection Combining

Energy detection is the most widely used technique in cognitive radio networks to enable opportunistic spectrum access. In this paper, the problem of energy detection of an unknown deterministic signal over fading channels is revisited. More particularly, a new closed-form mathematical expression is derived for the average probability of detection of the energy detector (ED) over $${\upalpha }-{\upmu }$$ ? - μ generalized fading channels with selection combining (SC) diversity reception. The derived expression is general and includes as special cases Nakagami-m, Weibull, Gamma, Rayleigh and Exponential distributions. This expression is useful to quantify the performance improvement of the ED with SC diversity reception.

Performance comparison of dual SC systems using different decision algorithms in the presence of interference

In this brief paper, we investigate selection combining (SC) technique, as one of the most efficient for upgrading transmission reliability and increasing channel capacity. Namely, dual SC diversity system operating over correlated Rician fading channels in the presence of Rayleigh cochannel interference (CCI) is studied. Desired signal power algorithm is explored by virtue of average bit error probability (ABEP), outage probability and average signal–to–interference ratio (SIR) at the output of the receiver. Presented numerical results aims to show effects of fading severity and level of correlation on considered performance metrics. Moreover, they are used for performance comparison of dual SC receivers applying two different decision algorithms, desired and SIR power algorithm, presenting the most significant contribution of this paper.

New Representations for the Gaussian Class Multivariate Weibull Distribution with Constant Correlation and Applications

Novel single-integral representations for the multivariate probability density functions (PDFs) and cumulative distribution functions (CDFs) of the Gaussian class Weibull distribution are derived. The solutions are expressed in terms of familiar mathematical functions which are available in common mathematical software. The well known equal (constant) correlation model is considered. A special linear transformation of independent Gaussian random variables is used to generate correlated Weibull random variables. The advantage of the new representation is that only a single integral computation is needed to compute a N-dimensional distribution. The new representation of the CDF is used for the performance evaluation of a selection diversity combiner operating in equally correlated Weibull fading channels. The new PDF representation is also used for an analysis of the moments of the output signal-to-noise ratio of an equal-gain diversity combiner operating in equally correlated Weibull fading channels.

Linear Diversity Combining on Nakagami-0.5 Fading Channels

The Nakagami-0.5 distribution is an important special case of the Nakagami distribution as it represents a worst case fading scenario. This scenario is of particular significance for wireless applications with high quality of service requirements. The bit error probability (BEP) performances of three basic diversity combining schemes in Nakagami-0.5 fading are considered. It is shown that the error rate performances of dual branch equal gain and selection combining (SC) diversity are identical regardless of modulation format. It is also shown that L-branch maximal ratio combining diversity in Nakagami-0.5 fading has the same BEP performance as single branch reception in Nakagami-L/2 fading with L times the transmission power of each branch. A useful upper bound for the BEP of L-branch SC diversity in Nakagami-0.5 fading is also derived. The performance degradation for the worst case Nakagami-0.5 fading relative to Rayleigh fading can be as much as 24.6 dB for a dual-diversity receiver at target BEP of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> . The additional resources required to restore a specified performance level, as increased channel signal-to-noise ratio and as number of additional diversity branches, are quantified. It is concluded that worst case Nakagami channels can result in dramatically poorer performance than Rayleigh channels, making proper system design and evaluation essential to achieve a required transmission quality.

On Wireless Channels With ${M}$-Antenna Eavesdroppers: Characterization of the Outage Probability and $\varepsilon $-Outage Secrecy Capacity

In this correspondence, we characterize the probability of secrecy-outage and the asymptotic high-signal-to-noise ratio (SNR) ε-outage secrecy-capacity for a single-input-single-output-multi-eavesdropper (SISOME) wireless system with eavesdroppers performing maximum ratio combining (MRC) or selection diversity combining (SDC) reception. We also consider the SISO2E case with eavesdropper antenna-correlation and finally, analyze the scenario where the eavesdropper has Rician fading links with the transmitter.