Rayleigh Fading Research Articles

Performance analysis of two-way multi-users cooperative communication system based on GSPIM-DCSK scheme

Based on the Joint Grouping Subcarrier-Permutation Index Modulation-DCSK (GSPIM-DCSK) system, we provide a new two-way multi-user half-duplex cooperative communication system in this work. Given its many benefits, the GSPIM-DCSK modulation is specifically selected as a choice for network coding techniques. A permutation index is used in the GSPIM-DCSK system to incorporate additional data bits with the modulating and carrier index bits. Establishing a cooperative multiuser system where users attempt to make contact with one another over a common relay is the main goal of this effort. Multi-user nodes and a single relay with a cooperative operator on staff for decoding and forwarding make up this system. To avoid interference from other users, the user’s nodes multiplex across various time intervals. We derive analytical expressions for the average bit error rate (BER) of the GSPIM-DCSK multi-user cooperative communication system in the presence of additive white Gaussian noise (AWGN) and multiple paths Rayleigh fading channels. The analytical and simulated average BER findings have been contrasted to verify the accurateness of the average BER analysis. Additionally, a comparison is presented between the average bit error rate (BER) performance of a novel GSPIM-DCSK cooperative system and an established DCSK cooperative system. The throughput and link spectral efficiency of this novel cooperative system are analyzed and compared with those of existing traditional cooperative systems. For the two-way two-user cooperative system, this comparison is done with two-way two-user systems like DCSK-CC and one-way cooperative system based on CIM-SR-DCSK-CC; for the two-way three-user cooperative system, it is done with scheme1 and scheme2. To compare and assess the performance of various systems, simulation results are employed. Furthermore, an analysis demonstrates how the proposed cooperative system, when combined with GSPIM-DCSK techniques, improves the efficiency of conventional cooperative DCSK systems.

End-to-end learning of adaptive coded modulation schemes for resilient wireless communications

Adaptive modulation and coding schemes play a crucial role in ensuring robust data transfer in wireless communications, especially when faced with changes or interference in the transmission channel. These schemes involve the use of variable coding rates, which can be achieved normally through code puncturing or shortening, and have been adopted in 4G and 5G communication standards. In recent works, auto-encoders for wireless communications have demonstrated the ability to learn short code representations that achieve gains over conventional codes. Such a methodology is attractive as it can learn optimal representations under a variety of channel conditions. However, due to its structure the auto-encoder does not currently support multiple code rates with a single model. This article draws upon the discipline of multi-task learning, as it applies to deep learning and therefore devises a branching architecture for the auto-encoder and custom training algorithm in training transmitter and receiver for adaptive modulation and coding. In this article we aim to demonstrate improvements in Block Error Rate over conventional methods in the Additive White Gaussian Noise channel, and to analyse the performance of the model under Rayleigh fading channels without retraining the auto-encoder on the new channel. This article demonstrates a novel approach towards training auto-encoder models to jointly learn adaptive modulation and coding schemes framed as a multi-task learning problem. The research outcomes extend end-to-end learning approaches to the design of adaptive wireless communications systems.

Simulation and analysis of 5G waveforms to reduce BER for vehicular communications

In today's rapidly evolving world, wireless communication has become a pervasive force, profoundly impacting various facets of our daily lives. Wireless Vehicular Networks stand out as a captivating realm of research, with a key focus on fostering information exchange among autonomous vehicles. As researchers witness surging demand in this domain, there is a growing emphasis on devising advanced techniques to augment network performance, particularly within the context of Fifth-generation (5G) applications, such as vehicular communication. The concept of Vehicle-to-vehicle (V2V) communications is poised to play a pivotal role in the future, presenting formidable challenges for the air interface by accommodating asynchronous multiple access and high mobility. Within this dynamic landscape, security and privacy issues loom large for 5G-enabled vehicle networks, many of which remain largely unexplored. The conventional waveforms, including Orthogonal Frequency Division Multiplexing (OFDM), may fall short of meeting these evolving standards. In this paper, authors delve into a comparative exploration of two waveform families, namely Filter Bank Multicarrier (FBMC) and Universal Filtered Multi-Carrier (UFMC), concerning their design and performance trade-offs. authors also examine their compatibility with various digital modulation schemes like 4-Quadrature Amplitude Modulation (QAM), 16-QAM, Offset Quadrature Phase Shift Keying (OQPSK), and Shaped offset OQPSK (SOQPSK). Through MATLAB simulations, our research vividly demonstrates the superior performance of UFMC when juxtaposed with OFDM and FBMC, especially concerning Bit Error Rate (BER) in both Rayleigh and Nakagami fading channels. In particular, authors consider a Nakagami shape parameter of 10, which yields a remarkable minimum BER for UFMC.

On the Performance of MMSE Channel Estimation in Massive MIMO Systems over Spatially Correlated Rician Fading Channels

Massive multiple-input-multiple-output (M-MIMO) offers remarkable advantages in terms of spectral, energy, and hardware efficiency for future wireless systems. However, its performance relies on the accuracy of channel state information (CSI) available at the transceivers. This makes channel estimation pivotal in the context of M-MIMO systems. Prior research has focused on evaluating channel estimation methods under the assumption of spatially uncorrelated fading channel models. In this study, we evaluate the performance of the minimum-mean-square-error (MMSE) estimator in terms of the normalized mean square error (NMSE) in the uplink of M-MIMO systems over spatially correlated Rician fading. The NMSE allows for easy comparison of different M-MIMO configurations, serving as a relative performance indicator. Besides, it is an advantageous metric due to its normalization, scale invariance, and consistent performance indication across diverse scenarios. In the system model, we assume imperfections in channel estimation and that the random angles in the correlation model follow a Gaussian distribution. For this scenario, we derive an accurate closed-form expression for calculating the NMSE, which is validated via Monte-Carlo simulations. Our numerical results reveal that as the Rician K-factor decreases, approaching Rayleigh fading conditions, the NMSE improves. Additionally, spatial correlation and a reduction in the antenna array interelement spacing lead to a reduction in NMSE, further enhancing the overall system performance.

An Efficient Design for the DVB-S2 Forward Link System Outer Layer Encoding Based on PCC Turbo Coding Across Fading Channel

The most significant challenges wireless broadcasting systems face are channel effects and Inter Symbol Interference (ISI). Many different kinds of channel coding are employed to get around these issues. Digital Video Broadcasting for Satellite Telecommunication Second Generation (DVB-S2) uses a serial concatenation of Bose, Ray-Chaudhuri, and Hocquenghem (BCH) code and Low-Density Parity-Check (LDPC) code as a Forward Error Correction (FEC) for error detection purpose and correction. In this work, a MATLAB code (m-files) is constructed to simulate the standard DVB-S2 Bit-Interleaved Coded Modulation (BICM) system according to the ETSI Technical Report (EN 302 307 1). Then, the traditional design is redesigned with a Parallel Concatenation Convolutional (PCC) Turbo coding in concatenation with LDPC coding to enhance the (FEC). The two approaches have been tested under the official modulation types QPSK, 8PSK, 16APSK, and 32APSK with 2/3, 3/4, 3/5, 4/5, and 5/6 code rates (RC). Over a Rayleigh Fading channel, the two models are compared. The proposed model performed better than the standard model regarding bit error rate (BER) mitigation when operating at varying signal-to-noise ratio (SNR) levels, especially in 8PSK 3/5 MODCODE. The proposed model achieved (2.6272×10-3) BER mitigation value with power gain equal to 4 dB.

Enhancing Signal Space Diversity for SCMA Over Rayleigh Fading Channels

Enhancing Signal Space Diversity for SCMA Over Rayleigh Fading Channels

Outage Probability Analysis for Relay-Aided Self-Energy Recycling Wireless Sensor Networks Over INID Rayleigh Fading Channels

Outage Probability Analysis for Relay-Aided Self-Energy Recycling Wireless Sensor Networks Over INID Rayleigh Fading Channels

Closed-form BER expression for multi-user downlink NOMA

Massive machine-type communication (MMTC) is an essential element for realizing the Internet of Things (IoT). However, certain challenges arise because MMTC should support a massive number of users. Recently, non-orthogonal multiple access (NOMA) has been highlighted as a technology for MMTC in a limited frequency band. To design and operate a NOMA-based communication system for a massive number of users, an accurate performance analysis for an arbitrary number of users and a practical power assignment method for the channel condition of each user are required. In this study, the exact bit error rate (BER) expression for an arbitrary user number is derived in an explicit closed form for NOMA-based communication. In addition, for analytical purposes, an approximate expression with high accuracy is proposed. To achieve an extension to the fading channel, the average BER expressions for the Rayleigh and Nakagami-m fading channels are presented in closed forms. Based on the derived BER expression, a power assignment algorithm that can achieve the target performance is proposed when each user is associated with a different signal-to-noise ratio. The derived BER expressions and the power assignment algorithm were verified based on computer simulations.

A new derivation of the Nakagami-m distribution as a composite of the Rayleigh distribution

Mobile communications systems are affected by what is known as fading, which is a well-known problem largely studied for decades. The direct consequence of fading is the complete loss of signal (or a large decrease of the received power). Rayleigh fading is a reasonable model for wireless channels although, Nakagami-m distribution seems better suited to fitting experimental data. In this paper we obtain the Nakagami-m distribution as a composite (mixture) of the Rayleigh distribution, a result which as far as we know it has not been shown in the literature. This representation of the Nakagami-m distribution facilitates computations of the average BER (Bit Error Rate) for DPSK (Differential Phase Shift Keying) and MSK (Minimum-Shift Keying) modulations for this distribution and higher moments of them, which is of great applicability to modeling wireless fading channels. Furthermore, a simple, not depending on any special function, apart of the Gamma function, bivariate version of the Nakagami-m distribution is also proposed as a special case of the multivariate version which is also presented. The proposed composite distribution is simulated through the standard procedure of summation of phasors, and results for the new closed-form measures for the MSK modulation are also shown. From that it is clear that the alternative formulation of the Nakagami-m distribution allows for easier modeling of fading fading-shadowing wireless channels through the new explicit second order statistics metrics. is well suited for modelling fading-shadowing wireless channels.

Downlink Learning-aided Precoding for Cell-Free networks Specially D esigned for beyond 5G Communication System

Objectives: With increase in number of access points in Cell-Free Massive Multiple Input Multiple Output (CFMM) system, spatial complexity of calculating precoding vector increases with traditional precoding schemes. So, to reduce computational complexity, network cost, and run time, a new deep learning -aided precoder is specially designed for CFMM system. The performance of downlink (DL) Cell-Free Massive Multiple Input Multiple Output (CFMM) system operating under Rayleigh fading channel model is analyze using new deep learning-based precoding scheme. Methods: We introduce new deep learning-aided precoder and an improved version of basic scalable pilot assignment algorithm which enhances system performance. We derive closed- form expression for average DL spectral efficiency (SE) for the proposed scheme, which is then compared with Minimum Mean Square Error Successive Interference Cancellation (MMSESIC), Regularized Zero Forcing (RZF), Least Square (LS) and Maximum Ratio (MR) combining techniques. We analyze the proposed scheme with perfect channel state information (CSI), instantaneous CSI, coherent transmission, non-coherent transmission, different pilot configuration. Findings: The spectral efficiency obtained with CFMM-MMSESIC and the proposed scheme is 3 bits/s/Hz, and 2.5bits/s/Hz respectively, which clearly indicates the difference of 20 % only. So, the proposed scheme gives near optimal results, and we can use simple linear combining techniques instead of complex non-linear combining techniques. Also, the proposed scheme with coherent data transmission gives performance curve, which is very close to MMSESIC scheme as desired. The performance of the proposed system is improved by reducing run time and computational complexity as compared to conventional linear precoding schemes. Novelty: The proposed precoder improves performance by reducing run time and computational complexity. Advanced pilot assignment algorithm enhances performance by reducing pilot contamination. Keywords: Cell-Free Massive Multiple Input Multiple Output, Pilot Contamination, Precoding, Minimum Mean Square Error Successive Interference Cancellation, Maximum Ratio, Regularized Zero Forcing (RZF), Least Square (LS)

HE EFFICIENT PERFORMANCE OF GENERALIZED SELECTIVE COMBINING TECHNIQUES ON RAYLEIGH FADING CHANNEL USING HYBRIDIZED MODULATION SCHEME

This study concentrated on improving Generalized Selective Combining (GSC), one of the widely used diversity combining methods in telecommunications, by combining the modulation schemes of Quadrature Amplitude Modulation (QAM) and Orthogonal Frequency Division Multiplexing (OFDM) over a Rayleigh Fading channel. These were done with the intention of delivering strong Quality of Service (QoS) in mobile communication, particularly with the goal of lowering Bit Error Rate (BER) to improve reception on the receiving end. According to the findings, the communication system’s performance efficiency was increased through the hybridization of the modulation schemes, with QAM (4 and 16 constellation being taken into consideration for this research) and OFDM, even though a Rayleigh Fading channel was used, preventing line of sight (LOS). Compared to the BER values obtained when the modulation schemes were not hybridized, GSC was considerably improved with a low BER. In light of the fact that the channel under consideration did not experience severe fading, which is what caused the low BER observed, this article indicates that GSC might be improved through the hybridization of modulation schemes to provide a good Quality of Services.

Reliable relay assisted communications for IoT based fall detection

Robust wireless communication using relaying system and Non-Orthogonal Multiple Access (NOMA) will be extensively used for future IoT applications. In this paper, we consider a fall detection IoT application in which elderly patients are equipped with wearable motion sensors. Patient motion data is sent to fog data servers via a NOMA-based relaying system, thereby improving the communication reliability. We analyze the average signal-to-interference-plus-noise (SINR) performance of the NOMA-based relaying system, where the source node transmits two different symbols to the relay and destination node by employing superposition coding over Rayleigh fading channels. In the amplify-and-forward (AF) based relaying, the relay re-transmits the received signal after amplification, whereas, in the decode-and-forward (DF) based relaying, the relay only re-transmits the symbol having lower NOMA power coefficient. We derive closed-form average SINR expressions for AF and DF relaying systems using NOMA. The average SINR expressions for AF and DF relaying systems are derived in terms of computationally efficient functions, namely Tricomi confluent hypergeometric and Meijer’s G functions. Through simulations, it is shown that the average SINR values computed using the derived analytical expressions are in excellent agreement with the simulation-based average SINR results.

An integrative numerical method for evaluating Ergodic capacity of multi-user NOMA over faded channels with imperfect-CSI and SIC

With increased demand for the internet and the Internet of Things (IoT), future wireless communication networks are draw more attention to afford the massive connectivity, capacity, and extensive coverage requirements. Recently, multi-user (MU) NOMA was introduced as a potential technique to address these challenges. Owing to the wide applicability of MU-NOMA, precise expressions for Ergodic capacity under realistic scenarios are very much required to evaluate its performance. Hence, in this paper, we derive the ergodic capacity expressions for MU-NOMA for generalized fading channels. To achieve precision, we have taken imperfect-successive interference cancellation (SIC) and channel state information (CSI) into account. The impact of imperfect SIC and CSI and fading parameters is investigated over Nakagami-m, Rayleigh, and Rician fading channels. The proposed approach is valid for any type fading channels. The obtained expressions for the Ergodic capacity over various fading channels are validated through the simulation results.

A deep learning approach based on Richardson and Gauss–Seidel for massive MIMO detection

AbstractMassive multiple‐input multiple‐output (MIMO) systems can improve the spectrum utilization and the system capacity, but this also increases the computational complexity of the signal detection. The existing iterative algorithms can greatly reduce the computational complexity; however, the detection performance is limited. In order to achieve a better balance between the computational complexity and the detection performance, this article combines the model‐driven deep learning approached with Massive MIMO signal detection to construct RGNet (RIGS‐based deep learning Network). First, RIGS is proposed as a hybrid method of RI (Richardson) and GS (Gauss–Seidel). The RIGS algorithm combines these methods to achieve faster convergence. However, the performance of RIGS joint algorithm is limited to the spatially correlated channel scenarios. To improve robustness, we further extend RIGS, by adding learnable parameters in each iteration and introducing staircase activation functions to significantly improve detection performance. Simulation results show that the proposed RGNet has low computational complexity and a simple and fast training process. It can also achieve excellent detection performance in Rayleigh fading channel and spatially correlated channel.

Secrecy Analysis of Decode-and-Forward Relay Based Heterogeneous Terrestrial RF - Underwater Acoustic System

This study examines how well a heterogeneous dual-hop terrestrial radio frequency and underwater acoustic downlink system maintain confidentiality. It includes an RF source, an intermediate decode-and-forward relay, an underwater multi-hydrophone destination, and a nearby eavesdropper. Eavesdropper overhears underwater acoustic signal transmitted by the relay. RF and underwater acoustic links undergo Nakagami-m and Rayleigh fading, respectively. Due to the propagation delay of underwater scenario, both destination and eavesdropper links are associated with outdated channel state information which also employs maximal-ratio combining. The closed form expressions of secrecy outage probability, strictly positive secrecy capacity, and intercept probability are derived. Monte-Carlo simulations are obtained to certify the analytical expressions.

DESIGN OF SPACE TIME TRELLIS CODED OFDM

Space Time Trellis Code (STTC) is a technique that can be used to improve the performance ofthe Orthogonal Frequency Division Multiplexing (OFDM) system over wireless channels byproviding both coding gain and diversity gain. STTC is combined from two codes, Trellis CodeModulation (TCM) as an inner code and Space Time Block Code (STBC) as an outer code. TCMwhich combines the choice of a modulation scheme with that of a convolutional code provides thecoding gain, and the other code provides the diversity gain. Simulation is done over flat fading andfrequency selective Rayleigh fading channel for Eight Phase Shift Keying (8-PSK) TCM. It foundthat the best results are obtained for the case of two transmitters and three receivers which have again of about 18dB over that without STBC.

New Golay decoding method using auto-encoder and OSD

In this study, we explore the potential of leveraging machine learning techniques, specifically auto-encoders (AE), for the decoding of linear block codes. Our findings suggest that this approach can outperform the conventional ordered statistics decoding (OSD) method, especially in a Rayleigh fading channel environment. We have rigorously trained the AE under both additive white Gaussian noise and Rayleigh fading channel conditions to ensure robustness in its performance. The output of the AE is combined with the received vector in a suitable manner to perform OSD. Through our experiments, we demonstrate that this proposed decoding approach yields better results than the conventional OSD method in Rayleigh fading channel when we used (23,12) Golay code.

Secrecy and Throughput Performance of Cooperative Cognitive Decode-and-Forward Relaying Vehicular Networks with Direct Links and Poisson Distributed Eavesdroppers

Cooperative communication and cognitive radio can effectively improve spectrum utilization, coverage range, and system throughput of vehicular networks, whereas they also incur several security issues and wiretapping attacks. Thus, security and threat detection are vitally important for such networks. This paper investigates the secrecy and throughput performance of an underlay cooperative cognitive vehicular network, where a pair of secondary vehicles communicate through a direct link and the assistance of a decode-and-forward (DF) secondary relay in the presence of Poisson-distributed colluding eavesdroppers and under an interference constraint set by the primary receiver. Considering mixed Rayleigh and double-Rayleigh fading channels, we design a realistic relaying transmission scheme and derive the closed-form expressions of secrecy and throughput performance, such as the secrecy outage probability (SOP), the connection outage probability (COP), the secrecy and connection outage probability (SCOP), and the overall secrecy throughput, for traditional and proposed schemes, respectively. An asymptotic analysis is further presented in the high signal-to-noise ratio (SNR) regime. Numerical results illustrate the impacts of network parameters on secrecy and throughput and reveal that the advantages of the proposed scheme are closely related to the channel gain of the relay link compared to the direct link.

Performance Comparison of IRS-Assisted SSK Modulation Over Rayleigh and Nakagami-m Fading Channels

To meet the needs of society, the next generation of communication systems will have to learn to juggle multiple responsibilities effectively. This is leading to exponential growth in both circuit complexity and error rates. It is possible to solve these issues by using the intelligent reflecting surface (IRS)-Assisted space shift keying (SSK) modulation technique. IRS is a cutting-edge technology that shows promise for future networks due to its low mistake rates and low-energy consumption. Similarly, SSK modulation is favored due to its preference for simpler hardware. Therefore, integrating IRS with SSK is preferable for minimizing both error rates and circuit complexity. In this article, a new framework is developed to characterize the average bit error rate (ABER) with the help of the moment generating function (MGF) over Nakagami-m fading channels. The ABER is derived by factoring the direct path and IRS reflected path at the receiver and also comparing the performance analysis over the Rayleigh fading channel. The analytical results are validated through Monte-Carlo simulations.

Analysis of STC-GFDM with Walsh Hadamard in generalized η−μ fading channel

ABSTRACT This manuscript presents a comprehensive analytical framework for Walsh-Hadamard Transform (WHT) precoding in Space-Time Coded Generalized Frequency Division Multiplexing (STC-GFDM) systems. The investigation specifically targets the η - μ fading channel and employs the moment generating function (MGF) approach to establish an exact closed-form expression for the Symbol Error Rate (SER). The derived expression enables the examination of one-sided Gaussian, Rayleigh, Nakagami-m and Hoyt-q fading channels as specific cases of the η - μ fading channel. Additionally, the paper also delves into the impact of crucial system parameters, including modulation order, channel fading parameters ( η and μ ) and the number of transmit and receive antennas, on the WHT-STC-GFDM system’s performance. Furthermore, the paper conducts an in-depth complexity analysis of the WHT precoder, shedding light on the computational demands associated with its implementation. In summary, this research enhances the understanding of WHT precoding in STC-GFDM systems operating in η - μ fading channels, providing valuable insights for the design and optimisation of future communication systems. The numerical results are validated through Monte-Carlo simulations.