Rayleigh Fading Environments Research Articles

Performance Analysis of Big Model Transmission under Double Rayleigh Fading

The recent big model such as GPT-3.5 possesses an extensive understanding of natural language, and it can perform a wide range of tasks, making it a significant advancement in the field of artificial intelligence (AI). A critical challenge in the design and implementation of big model is that it imposes a heavy load on the wireless transmission due to a huge size of the network parameters, especially for the distributed implementation. To tackle this challenge, we investigate big model transmission under practical double Rayleigh fading environments, where the big model is simultaneously distributed to multiple training nodes. To evaluate the system performance, we study the system outage probability (OP) based on the transmission latency, where an analytical expression is derived for the OP. Finally, we present some simulations under double Rayleigh fading environments, in order to show the validity of the proposed big model transmission.

CSIN-assisted AF dual-hop relaying communication systems over imperfect Nagakami-[formula omitted] fading channels: Exact error performance

Relaying-based communication techniques are promising for current and future wireless systems. Amplify-and-forward (AF) relaying is more attractive due to the low cost and simplicity in its relay implementation. As compared to other AF schemes, the channel-state-information (CSI)-and-noise (CSIN)-assisted one is optimal and practically recommended. However, up to this moment, the exact symbol error rate (SER) performance of CSIN-assisted AF dual-hop relaying systems has been analytically derived only for Rayleigh fading environments, while for other more generic fading models, including Nakagami-m, it has been computed either approximately or via long-running time computer simulations. Thus, in this paper, we consider a CSIN-assisted AF dual-hop relaying system with independent and non-identical Nakagami-m fading channels and derive a new expression for its exact SER performance under the effect of imperfect channel estimation. The derived expression includes infinite series that can truncate quickly using a few terms, requires short computational time as compare to simulation, shows perfect matching with the simulation results, and offers remarkable accuracy enhancement over its approximate peer derived in literature. In addition, it helps in demonstrating some useful insights into the system’s realistic error performance considering different system and fading severity conditions. For example, results show that the system’s exact SER performance is dominated by the worse fading hop, does not change when the system’s two fading hops exchange their fading conditions, and improves faster with the per symbol average SNR when the fading severity conditions are better.

Cooperative Fusion Architecture-based Distributed Spectrum Sensing Under Rayleigh Fading Channel

Cognitive radio is one of the most promising technologies due to the spectrum scarcity, especially in the microwave band. Spectrum sensing forms an essential functionality for CR systems. However, such detection performance is usually compromised by shadowing and fading channel conditions. Cooperative sensing is one of the crucial solutions to overcome degraded detection performance. A distributed architecture for the processing and fusion of sensing information is proposed to improve sensing performance and reduce reporting error. The decision fusion for cooperated users could be complex in dense network scenarios and reported sensing traffic may require significant bandwidth. The paper presents a new cooperative distributed PUs detection and proposes dynamic threshold based on controlled probability of false alarm to enhance sensing efficiency and reliability in a Rayleigh fading environments. A cooperative distributed PUs detection is realized by fusion node (FNs) that dynamically selected from the group members. The adaptive detection threshold is computed dynamically using the link quality indicators (LQIs) of the sensing channels. Moreover, the proposed scheme can significantly minimize the typically transmitted bits in the reporting channels. This work also deliberated the design parameters of the CR on the performance of fusion values. The simulation evaluation presents that the adapted threshold considerably improves the performance of the distributed cooperative sensing (DCS) process. The simulation results verified that the error was minimized remarkably. The ROC graph is notably enhanced for the sensing process in term of probability of detection and probability of false alarm. Finally, it was presented that with the proposed scheme the sensitivity requirements could be significantly enhanced up to 0.95.

Source Enumeration Method using Eigenvalue Gap Ratio and Performance Comparison in Rayleigh Fading

In electronic warfare, source enumeration and direction-of-arrival estimation are important. The source enumeration method based on eigenvalues of covariance matrix from received is one of the most used methods. However, there are some drawbacks such as accuracy less than 100 % at high SNR, poor performance at low SNR and reduction of maximum number of estimating sources. We suggested new method based on eigenvalues gaps, which is named AREG(Accumulated Ratio of Eigenvalues Gaps). Meanwhile, FGML(Fast Gridless Maximum Likelihood) which reconstructs the covariance matrix was suggested by Wu et al., and it improves performance of the existing source enumeration methods without modification of algorithms. In this paper, first, we combine AREG with FGML to improve the performance. Second, we compare the performance of source enumeration and direction-of-arrival estimation methods in Rayleigh fading. Third, we suggest new method named REG(Ratio of Eigenvalues Gaps) to reduce performance degradation in Rayleigh Fading environment of AREG.

Performance Analysis of a Linear MMSE Receiver in Time-Variant Rayleigh Fading Channels

The performance of the uplink of single and multiuser multiple input multiple output (MIMO) systems depends crucially on the receiver architecture and the quality of channel state information at the receiver. Therefore, several previous works have developed minimum mean squared error (MMSE) receivers and proposed balancing the resources spent on acquiring channel state information and transmitting the payload of data packets. Somewhat surprisingly, the most popular MIMO linear MMSE receivers do not exploit the correlation structure that is present in autoregressive Rayleigh fading environments. Therefore, in this article we first develop a new linear receiver that not only takes channel state information errors into account in minimizing the MSE of the received data symbols, but it also utilizes that the subsequent noisy channel coefficients are correlated. For this new linear MMSE receiver, we derive the achieved MSE as a function of the number of receive antennas and the pilot-to-data power ratio. Interestingly, we find that the pilot power that minimizes the MSE of the data symbols does not depend on the number of antennas and that the new linear MMSE receiver outperforms previously proposed MIMO receivers when the autocorrelation coefficient of the channel is high.

Performance Analysis of Improved Self Cancellation Technique for Wavelet Based OFDM Through Simulink Model

As per the most recent literature, Orthogonal Frequency Division Multiplexing (OFDM), a multi access technique, is considered most suitable for the 3G, 4G and 5G techniques in high speed wireless communication. What made OFDM most popular is its ability to deliver high bandwidth efficiency and superior data rate. Besides it, high value of peak to average power ratio (PAPR) and Inter Carrier Interference (ICI) are the challenges to tackle down via appropriate mitigation scheme. As a research contribution in the present work, an improved self-cancellation (SC) technique is designed and simulated through Simulink to mitigate the effect of ICI. This novel proposed technique (Improved SC) is designed over discrete wavelet transform (DWT) based OFDM and compared with conventional SC scheme over different channel conditions i.e. AWGN and Rayleigh fading environments. It is found that proposed DWT-OFDM with Improved SC scheme outperforms conventional SC technique significantly, under both AWGN and Rayleigh channel conditions. Further, in order to justify the novelty in the research contribution, a Split-DWT based Simulink model for Improved SC scheme is investigated to analyse the BER performance. This Split-DWT based Simulink model presented here foretells the future research potential in wavelet hybridization of OFDM to side-line ICI effects more efficiently.

Threshold selection analysis of spectrum sensing for cognitive radio network with censoring based imperfect reporting channels

An appropriate threshold selection scheme is one of the main components to adjudicate the performance of energy detection spectrum sensing (EDSS) technique for cognitive radio network. In this paper, we have employed two different threshold selection approaches namely, the constant false-alarm rate (CFAR) and minimized error probability (MEP) and analyzed the threshold selection effects on the performance of cognitive user (CU) communication systems particularly, the total spectrum sensing error probability and throughput. We have derived the expressions and analyzed these performance parameters by considering an imperfect spectrum sensing and reporting channels in the cooperative spectrum sensing scenarios for additive white Gaussian noise (AWGN), Rayleigh and Nakagami-m fading environments. In addition, the censoring concept has been applied to the proposed system and compared its effect with that of the non-censoring based cognitive radio network (CRN) system under the perfect reporting (PR) and imperfect reporting (IR) channel. With the help of simulation, we have illustrated that the role of threshold selection approach is crucial to maximize the throughput and minimize the spectrum sensing error while considering the amount of error in the reporting channel. Further, from the results, the existence of trade-off between the spectrum sensing error probability and throughput is presented with threshold selection approaches. Moreover, it is also shown that there is need to switch among CFAR and MEP threshold selection approaches in the censoring scenario, to enhance the throughput and decrease the spectrum sensing error probability.

Power Distribution of Device-to-Device Communications Under Nakagami Fading Channel

Recently, device-to-device (D2D) communication was designated to work in cellular networks as a new standard to boost their performances. This kind of communication can occur either underlay to the existing cellular infrastructure, or overlay in the industrial scientific and medical (ISM) unused band. In this paper, we consider the case that D2D transmissions take place concurrently with the usual cellular players in the same spectrum band, and thus, controlling the interference caused by the cellular user equipments (UEs) is of crucial importance. In this work, we consider the uplink transmission of a tier of D2D users. Using network model based on stochastic geometry, we express the general cumulative distribution function (CDF) of the D2D transmit power under Nakagami fading channel. Special cases as CDF of the transmit power for Rayleigh fading and noiseless environment were derived. Besides, an upper bound of the general CDF expression is proposed. To deal with D2D lifetime, first, we express the expectation of the transmit power, then we determine the expectation of the devices lifetime and finally, we give an upper bound of this lifetime expectation. Through simulation, the obtained numerical results confirm the effectiveness of the proposed analytic schemes.

Error performance of QAM schemes for SIMO and MIMO networks

In this paper, we analyze the average symbol error rate (ASER) of single-input multiple-output (SIMO) networks for rectangular quadrature amplitude modulation (RQAM) and cross-QAM (XQAM) subject to Rayleigh fading. Then, we investigate the performance of RQAM for a SIMO system under κ-μ fading conditions. And also, we consider a multiple-input multiple-output with single transmit antenna selection and maximal ratio combining over Rayleigh fading environments. To analyze the key parameters on the network performances, we propose the analytical expressions of ASER for the considered networks. Assuming flat fading, the obtained exact and approximate expressions for ASER based on the probability density function approach. Furthermore, we present asymptotic expressions of RQAM and XQAM schemes for a SIMO system over Rayleigh fading at the high signal to noise ratio to evaluate the network performance in terms of diversity gain. Finally, simulations are ensured to confirm the correctness of our frameworks in this study.

A generalised antenna correlation model for accurate performance evaluation of 2D massive MIMO communication systems

ABSTRACT Massive multiple-input multiple-output (MIMO) is considered as a key component of the new fifth-generation (5 G) communication systems and beyond to meet the rapid explosion of global wireless data traffic. However, antenna correlation is well known to have a direct impact on the capacity of practical MIMO schemes. Therefore, research and industrial communities are still looking for novel techniques to employ a large number of antennas with minimum correlation for compact mobile devices and base stations. In this paper, a realistic and generalised correlation matrix (GCM) model is developed for the accurate performance evaluation of two-dimensional (2D) massive MIMO systems. Based on the proposed GCM model, a closed-form expression of the channel capacity is derived for spatially correlated Rayleigh-fading MIMO environment to assess the acceptable range of antenna correlation. Over different 2D antenna configurations, simulation results validate the accuracy of derived capacity expression and demonstrate that the proposed GCM model tends to provide a more realistic performance compared with the existing methods. This may help to implement a large number of antennas in a constrained-size ground plane with an efficient tradeoff between 2D array designs and required system performance.

LDPCC and OFDM based cooperative communication for wireless sensor networks

This paper investigates the low-density parity-check codes and orthogonal frequency division multiplexing technique effects on the relay assisted sensor networks. The investigation utilizes Rician and Rayleigh fading environments for the performance analysis. The investigation also considers two different types of information exchange processes, which are direct and relay assisted cases. In the relay assisted case, the relay terminal operates in amplify-and-forward and decode-and-forward modes. Monte-Carlo based computer simulations reveal that 10-5 bit error rate value is reached at 16.50 dB for low density parity check coded orthogonal frequency division multiplexing over Rician fading environment in decode-and-forward relay protocol. Similarly, 10-5 bit error rate value is reached at 0.36 dB for the low density parity check coded orthogonal frequency division multiplexing over Rician fading environment in amplify-and-forward relay protocol and finally 10-5 bit error rate value is reached at -5.30 dB for low density parity check coded orthogonal frequency division multiplexing over Rician fading environment without relay protocols.

Relay Outdatedness Under MRC Deployment

Using the distributions of bivariate exponential-correlated Nakagami-m, and Rician fading, this paper analyses opportunistic relay channel-state-information (CSI) outdatedness- written as “relay outdatedness” for brevity in this work-under two-degree-of-freedom (DoF) line-of-sight (LoS), and n-DoF nonline-of-sight (NLoS), utilising maximal-ratio-combining (MRC) deployment under Rayleigh fading environments. End-to-end system performance under NLoS outdated-CSI (oCSI) conditions are also examined. Under the proposed generalised-oCSI conditions, a conditional distribution of Rayleigh fading is first obtained, from which the corresponding distribution of Rayleigh fading under MRC deployment can be derived. Detailed discussions are given, from which MRC appears to outperform selection combining diversity under generalised-oCSI conditions. Trade-off between key parameters is identified, and explained. Monte Carlo simulation is given, which is shown to match the proposed theoretical findings.

Optimized cooperative spectrum sensing network analysis in nonfading and fading environments

SummaryThe proposed cooperative spectrum sensing (CSS) network is equipped with multiple antennas and an improved energy detector (IED) scheme at each cognitive radio (CR). Each CR in the network receives the information about the primary user (PU) in the form of binary decisions at multiple antennas. Diversity technique called selection combining (SC) scheme is used at multiple antennas to select the maximum value of sensing information present at multiple antennas. Finally, sensing information will be passed to the fusion center (FC) through reporting channel, and the final decision about PU is made at FC using fusion rules. Initially, we have derived the novel missed detection probability expressions for AWGN channel, Rayleigh, and Rician fading environments. Later, the closed form of optimized expressions for proposed CSS network parameters are derived to achieve an optimal performance. The closed form of optimized expressions such as number of CR users (Nopt), normalize threshold value (λn,opt), and an arbitrary power of the received signal (popt) are derived under various fading environments. The performance is evaluated using complementary receiver operating characteristics (CROC) and total error rate curves. The MATLAB‐based simulations are evaluated with the strong support of theoretical expressions. Finally, various simulation parameters such as sensing channel SNR, the error rate in reporting channel, threshold value, and number of antennas at each CR are considered in the simulation to show the effect on the performance of proposed CSS network.

ABEP Evaluation of Spatial Modulation Communication Systems: Improved Analytical Framework

Average bit error probability (ABEP) performance evaluation of spatial modulation (SM) over wireless fading channels has attracted huge interest in the literature. In general, the core step to analytically evaluate such ABEP performance is to theoretically derive the associated average pairwise error probabilities (average-PEPs). However, these average-PEPs have been derived so far in exact and closed-form expressions only for two cases: 1) SM systems with real-valued modulation regardless of the fading channel type, 2) SM systems with complex-valued modulation but only for Rayleigh fading channel type. In case of complex-valued modulation with non Rayleigh fading, such average-PEPs were derived either in exact but integral-form expressions or in closed-form but non-simplified and non-tight approximate expressions. Thus, here, we introduce a new analytical framework to fill this literature gap by deriving new exact and closed-form formulas for the SM system's average-PEPs. We first apply the proposed framework on SM system with perfect channel-state-information (CSI) considering Rayleigh and Rician fading environments as two separate scenarios. Then, in order to show the effectiveness of the proposed approach, we reapply it for the imperfect CSI estimation scenario, where more generic exact average-PEPs are derived. Numerical and simulation results are provided, which show that, as compared to the widely adopted conventional literature approximate method, the proposed framework offers much better accuracy over the whole signal-to-noise-ratio (SNR) region.

Power Beacon-Assisted Energy Harvesting in a Half-Duplex Communication Network under Co-Channel Interference over a Rayleigh Fading Environment: Energy Efficiency and Outage Probability Analysis

In this time, energy efficiency (EE), measured in bits per Watt, has been considered as an important emerging metric in energy-constrained wireless communication networks because of their energy shortage. In this paper, we investigate power beacon assisted (PB) energy harvesting (EH) in half-duplex (HD) communication network under co-channel Interferer over Rayleigh fading environment. In this work, we investigate the model system with the time switching (TS) protocol. Firstly, the exact and asymptotic form expressions of the outage probability (OP) are analyzed and derived. Then the system EE is investigated and the influence of the primary system parameters on the system performance. Finally, we verify the correctness of the analytical expressions using Monte Carlo simulation. Finally, we can state that the simulation and analytical results are the same.

On the Distribution of SINR for MMSE MIMO Systems

While the performance analysis of linear zero-forcing (ZF) and minimum mean-square error (MMSE) receivers has received much attention, there has been no exact closed-form distribution of signal-to-interference-plus-noise ratio (SINR) for MMSE multiple-input multiple-output (MIMO) systems in the arbitrary fading environments for over the past 20 years. In this paper, an exact and general distribution of SINR for MMSE MIMO systems is presented under uncorrelated Rayleigh fading environments. We start our analysis by finding regular patterns from the probability density function (PDF) of SINR for small dimensions, and using the regular patterns, we extend the PDF to arbitrary dimensions. From the exact and general PDF of SINR for MMSE MIMO systems, the cumulative distribution function and the moment-generating function are derived in terms of the incomplete gamma function and the confluent hypergeometric function of the second kind, respectively. As applications, the error probability, outage probability, and achievable sum rate are investigated by using the distribution of SINR for MMSE MIMO systems. Most notably, the achievable sum rates for ZF and MMSE MIMO systems are defined by using the Meijer $G$ -function, which are the first closed-form expressions in the literature.

Concatenation of polar codes with three‐dimensional parity check (3D‐PC) codes to improve error performance over fading channels

SummaryIn this paper, we concatenated of three‐dimensional parity check (3D‐PC) block and polar codes for improving error correction performance and bit error rate (BER). Three different sizes of 3D parity check blocks (4 × 4 × 4, 8 × 8 × 8, and 16 × 16 × 16) are used for polar code concatenation. The 4 × 4 × 4 block returns the best performance, but higher complexity of decoder is needed unlikely. The 8 × 8 × 8 has returned acceptable complexity and good performacne. The complexity of decoder is less in the case of 16 × 16 × 16 with slight performance. The performance of the 3D‐PC is reduced when the codewords length is increased. The experiment considered the presence of additive white Gaussian noise (AWGN) with Rayleigh and Rician fading environments. 3D‐PC and polar code concatenation is more precise with codewords of short length, whereas there is insufficient concatenation accuracy with longer codewords. The outcomes of this study contain comparison between AWGN, Rayleigh, and Rician environments. The AWGN is noticed to have a lesser negative impact on the performance of code. Furthermore, increasing the code length may slightly fill the gap of performance between the concatenated and none concatenated polar codes due to the impact of code length on parity check code performance. Simulation results showed the coding performance in case of the polar code with concatenation and without concatenation for different code lengths. Generally, the 3D‐PC polar code concatenation is drawn the optimal result in AWGN environments.

Opportunistic Outdated Relays Under Even-Degree-of-Freedom Generalized-Rician Fading

Using a distribution of a non-central chi-square random variable and selection combining, statistics of wireless systems employing decode-and-forward (DF) opportunistic relays (ORs) under outdated channel state information (CSI), and independent and identically distributed (i.i.d.) generalized-Rician fading environments are derived. By mathematically rewriting the Marcum $Q$ -function in its infinite-summation form, the distribution of non-central chi-square is mathematically simplified to its desirable form under different scenarios, which are then employed to compute average bit error rates for popular modulation schemes. Distributions of end-to-end system signal-to-noise ratio, useful for fifth-generation backhaul wireless communications, are also derived under integer and non-integer fading parameters. The new findings generalize existing findings employing DF ORs under i.i.d. Rayleigh fading environments. Mathematical predictions are shown to match simulation results.

Statistical Analysis of Modified Fading Simulator in Rayleigh Fading Environment

Statistical Analysis of Modified Fading Simulator in Rayleigh Fading Environment

Spatial Lattice Modulation for MIMO Systems

This paper proposes spatial lattice modulation (SLM), a spatial modulation method for multipleinput-multiple-output (MIMO) systems. The key idea of SLM is to jointly exploit spatial, in-phase, and quadrature dimensions to modulate information bits into a multi-dimensional signal set that consists oflattice points. One major finding is that SLM achieves a higher spectral efficiency than the existing spatial modulation and spatial multiplexing methods for the MIMO channel under the constraint ofM-ary pulseamplitude-modulation (PAM) input signaling per dimension. In particular, it is shown that when the SLM signal set is constructed by using dense lattices, a significant signal-to-noise-ratio (SNR) gain, i.e., a nominal coding gain, is attainable compared to the existing methods. In addition, closed-form expressions for both the average mutual information and average symbol-vector-error-probability (ASVEP) of generic SLM are derived under Rayleigh-fading environments. To reduce detection complexity, a low-complexity detection method for SLM, which is referred to as lattice sphere decoding, is developed by exploiting lattice theory. Simulation results verify the accuracy of the conducted analysis and demonstrate that the proposed SLM techniques achieve higher average mutual information and lower ASVEP than do existing methods.