Fading Channel Model Research Articles

Modelos de canal de desvanecimiento para comunicaciones Millimeter-Wave

A realistic performance assessment of any wireless communication system requires the use of a fading channel model that reflects its main characteristics. The traditional Rayleigh and Nakagami-m models have been (and still are) the basis of most theoretical research on wireless technologies today, even for emerging technologies, such as millimeter-wave communications (mm-Wave). In this article, through the use of the mean square error statistical test, we show that the FMR and κ-μ shadowed models fit better to field measurements in outdoor environments at 28 GHz than the conventional channel models. Therefore, these generalized models are introduced as a physically feasible alternative that can be used as a benchmark when evaluating communications performance in mm-Wave scenarios.

Improving the Performance of MIMO Fading Channel Simulators Using New Parameterization Method

The research aims to modeling and simulation of fading channels for providing necessary tool to develop communication systems. The modeling and simulation of MIMO fading channels is studied for both isotropic- and non-isotropic scattering cases for one-ring model, so in this context, three methods for MIMO simulation channel models are studied: Extended Method of Exact Doppler Spread (EMEDS), Modified Method of Equal Areas (MMEA) and Method Lp-Norm (LPNM). Three new methods are also suggested to design the simulation model of MIMO channel: Modified Extended Method of Exact Doppler Spread (MEMEDS), New Modified Method of Equal Areas (NMMEA) and Modified Lp-Norm method (MLPNM). The performance of each proposed method is compared with the original method by comparing the statistical properties ACF, 2D-CCF and CF of both reference and simulation models.

Rayleigh Fading Modeling and Channel Hardening for Reconfigurable Intelligent Surfaces

A realistic performance assessment of any wireless technology requires the use of a channel model that reflects its main characteristics. The independent and identically distributed Rayleigh fading channel model has been (and still is) the basis of most theoretical research on multiple antenna technologies in scattering environments. This letter shows that such a model is not physically appearing when using a reconfigurable intelligent surface (RIS) with rectangular geometry and provides an alternative physically feasible Rayleigh fading model that can be used as a baseline when evaluating RIS-aided communications. The model is used to revisit the basic RIS properties, e.g., the rank of spatial correlation matrices and channel hardening.

Multiple-Relay Slotted ALOHA: Performance Analysis and Bounds

Wireless random access protocols are attracting a revived research interest as a simple yet effective solution for machine-type communications. In the quest to improve reliability and spectral efficiency of such schemes, the use of multiple receivers has recently emerged as a promising option. We study the potential of this approach considering a population of users that transmit data packets following a simple slotted ALOHA policy to a set of uncoordinated relays (phase-1). These, in turn, independently forward - part of - what decoded towards a collecting sink (phase-2). For an on-off fading channel model, we provide exact expressions for phase-1 throughput and packet loss rate for an arbitrary number of relays, characterising the benefits of multi-receiver schemes. Moreover, a lower bound on the minimum amount of phase-2 resources needed to deliver all information collected at the relays is provided. The bound is proven to be achievable via random linear coding when no constraints in terms of latency are set, with an overhead that approaches zero with the inverse of the packet length. We complement our study discussing a family of simple forwarding policies that require no packet-level coding, and optimising their performance based on the amount of available phase-2 resources. The behaviour of both random linear coding and simplified policies is also characterised when receivers are equipped with finite buffers, revealing non-trivial tradeoffs.

Stochastic stability analysis for Vehicular Networked Systems with State-dependent bursty fading channels: A self-triggered approach

Vehicular Networked Systems (VNS) are mobile ad hoc networks where vehicles exchange information over wireless communication networks to ensure safe and efficient operation. It is, however, challenging to ensure system safety and efficiency as the wireless channels in VNS are often subject to state-dependent deep fades where the data rate suffers a severe drop and changes as a function of vehicle states. Such couplings between vehicle states and channel states in VNS thereby invalidate the use of separation principle to design event-based control strategies. By adopting a state-dependent fading channel model, this paper presents a novel self-triggered scheme under which the VNS ensures efficient use of communication bandwidth while preserving stochastic stability. Under the proposed self-triggered scheme, this paper presents a novel source coding scheme that tracks vehicle’s states with performance guarantee in the presence of state-dependent fading channels. The efficacy and advantages of the proposed scheme over other event-based strategies are verified by a leader–follower example.

Short-Term Power Constrained Cell-Free Massive-MIMO Over Spatially Correlated Ricean Fading

This paper considers short-term power constrained cell-free massive multiple-input multiple-output (MIMO) scenarios where a large set of multi-antenna access points (APs) provide service to a group of single-antenna mobile stations (MSs) on a spatially correlated multipath environment. Based on a probabilistic approach, the spatially correlated propagation links are modeled using either Ricean or Rayleigh fading channel models that combine a deterministic line-of-sight (LOS) propagation path with a small-scale fading caused by non-line-of-sight (NLOS) multipath propagation. Assuming the use of minimum mean square error (MMSE) channel estimates, closed-form expressions for the downlink (DL) achievable spectral efficiency of a cellfree massive MIMO network with short-term power constraints (i.e., a vector normalized conjugate beamformer (NCB)) are derived and benchmarked against that provided by the conventional cell-free massive MIMO network with long-term power constraints (i.e., the conventional conjugate beamforming (CB)). These expressions, encompassing the effects of spatial antenna correlation, Ricean/Rayleigh fading and pilot contamination, are then used to derive both pragmatic and optimal max-min peruser power allocation strategies and to gain theoretical insight on the performance advantage provided by the use of short-term power constraints instead of the conventional long-term power constrained approach.

Superimposed Pilot Code-Domain NOMA Scheme for Satellite-Based Internet of Things

Satellite-based Internet of Things (S-IoT) is regarded as an effective solution to enable ubiquitous connectivity in a global coverage and cost-effective manner for massive machine type communications (mMTC) in the future Internet of Things. In this article, we propose a superimposed pilots code domain nonorthogonal multiple access over a shadowed-Rician fading and path loss satellite-ground channel model in uplink mMTC S-IoT system. First, we analyze the interference due to the collision in the random access scenario, and propose an iteration channel estimation based on ridge regression algorithm to attain a more precise channel state information. Moreover, we utilize successive interference cancellation (SIC) and successive joint decoding (SJD) to recover the singleton user equipments. Then, we derive the expressions of the outage probability and maximum system throughput of SP scheme, and compared with the regular orthogonal pilot (RP) scheme under SIC and SJD, respectively. Simulations validate our analytical results and show that the achievable system throughput of the SP scheme under SJD can outperform that of the RP scheme in a S-IoT system for short packet transmission.

Transceiver Design for GFDM with Hexagonal Time–Frequency Allocation Using the Polyphase Decomposition

Generalized frequency division multiplexing (GFDM) is a waveform for the next-generation communication systems to succeed in the drawbacks of orthogonal frequency division multiplexing (OFDM). The symbols of users are transmitted with the time- and frequency-shifted versions of a prototype filter. According to filtering operation, the computational complexity and processing load are high for the devices that suffer from energy consumption. The communication systems are required to support the new generation devices that need low energy consumption and low latency issues. Motivated by such demands of the next-generation communication system, we propose a novel GFDM waveform that we call hexagonal GFDM. The contributions of the hexagonal GFDM are that it: (i) supports short transmission time based on its hexagonal time–frequency allocations; and (ii) provides low latency communication with low computational complexity manner. Furthermore, we design a transmitter and receiver structure in a less complicated way with mathematical derivation by using polyphase decomposition and Fourier transform (FT) transformation. The proposed systems are realized analytically and investigated over Rayleigh fading channel model through computer simulations.

Channel Measurements and Modeling for 400–600-MHz Bands in Urban and Suburban Scenarios

Sub-1 GHz bands have been used for many years and now some of them will be reallocated for new applications, including the fifth generation (5G) wireless communication systems and beyond, Internet of Things (IoT), smart grid, etc. As the well-known path-loss (PL) models are mainly applicable in 2-6-GHz frequency range, a new channel measurement campaign is needed to study the propagation characteristics at sub-1 GHz bands. In this article, we conduct fixed-to-mobile wideband channel measurements at 400-600-MHz bands in urban and suburban scenarios using the time domain channel sounder. As the interference and noise signals are severe, the transmitted waveform is carefully designed to enlarge the system dynamic range. Meanwhile, ray tracing simulation is applied to construct the measurement environments and do the mutual verification with measurement results. The two-slope PL model and lognormal shadowing fading model are proposed for large-scale fading channel modeling. The root mean square (RMS) delay spread (DS), number of paths, and diffraction characteristics are also analyzed. The results will have great importance for the coming new applications at sub-1 GHz bands.

BER performance analysis of OFDM‐based integrated PLC and MIMO‐VLC system

In the present paper, the bit error rate (BER) performance of hybrid power line communication (PLC) and multiple-input multiple-output (MIMO) visible light communication (VLC) system (HPMV) has been investigated using line-of-sight (LOS) and LOS plus first reflection (L-R1) signals for room size of 5 m × 5 m × 3 m (configuration A) and 7.5 m × 7.5 m × 3.5 m (configuration B). In the work, Rayleigh fading and Barry channel models have been considered for PLC and VLC channels respectively. The BER has been analysed by varying separations between LEDs as 0.2 m, 0.6m and 1m for both configurations. The results show that the BER for LOS and L-R1 signals decreases upto optimal separation of 0.6 m for configuration A. However, the result indicates that the required optimal separation for configuration B is more than configuration A. The channel frequency response of MIMO-VLC and HPMV system has been inspected and it supports the results of BER simulation. It has been found that, with increase in spatial separation between LEDs, the deep notches and attenuation in the frequency response of MIMO-VLC system decrease. The overall investigation shows that even though OFDM is resilient to frequency selective fading, an optimum separation between LEDs must be chosen according to the room size for the HPMV system.

Performance Analysis of Cellular Downlink With Fluctuating Two-Ray Channels Under Inter-Cell Interference

To alleviate the extremely high area spectral efficiency requirement challenge in next generations of cellular networks, dense heterogeneous type networks where base stations transmit with different power levels are been considered operating at new frequencies in millimeter-wave (mm-Wave) band. The high density of the aforementioned networks, unfold with small area cells that even with higher attenuation of mm-Wave signals encounter inter-cell interference. In this work, heterogeneous, and homogeneous downlink cellular networks operating in mm-Wave frequencies are considered, in which all wireless channels are modeled by fluctuating two-ray (FTR); a mm-Wave channel model recently proposed, and shown to fit well with experimental data. Analytical expressions for coverage probability, average rate, and bit error probability under inter-cell interference are obtained. Simulation results show the accuracy of the analytical derivations. Moreover, in some scenarios, FTR channel model exhibits a significant performance degradation over Nakagami, and Rayleigh fading channel models. Finally, one of the auxiliary fading parameters of FTR model, defined as power of line of sight components to that of diffuse component, has the most significant effect on the system performance.

A Novel Application of Pattern Search Algorithm for Efficient Estimation of Channel State Information in MIMO Network

A novel intelligent computation mechanism is proposed for the estimation of channel state information in MIMO architecture. In this computing technique, the global optimizer Pattern Search algorithm is used to find the accurate channel state information which is based on coefficients of the channel matrix. The pattern search algorithm is exploited for the square channel matrix which consists of an equal number of array elements at both transmitter and receiver end of the communication system. Rayleigh fading channel modeling is explored in this work for evaluating the response of received signal over channel matrix of different dimensions. Also, two cases of measured white Gaussian noise are applied for evaluating the trend of algorithm which are without noise and 20 dB of noise. A Mean Square Error based evaluation function is formulated for assessing the true response of channel coefficients with the estimated one. This error function is effective enough to reach the best coefficient with only one symbol. The efficiency and performance of the pattern search algorithm are examined with different types of analysis like accuracy, convergence, and computational complexity on the bases of statistical parameters. A sufficient number of absolute Monte-Carlo simulations are practiced for the extensive statistical study of the proposed algorithm.

Stability analysis and output feedback control for stochastic networked systems with multiple communication delays and nonlinearities using fuzzy control technique

This paper addresses the H-infinity Takagi-Sugeno (T-S) fuzzy control for a class of T-S fuzzy discrete networked control systems with random interval communication delays and random sector nonlinearities. Firstly, the T-S fuzzy model is employed to approximate the discrete networked control system and the ℓth-order Rice fading channels model is introduced in the system model. Secondly, the T-S fuzzy dynamic output feedback controller with ℓth-order Rice fading channels output is designed for the T-S fuzzy discrete networked control system. Thirdly, the discrete delay-dependent Lyapunov-Krasovskii functional, stochastic system theory and Bernoulli probability distribution are employed to derive the stability conditions in terms of linear matrix inequalities (LMIs). Compared with previous works, the fading channels in the signal transmission are described clearly by setting the different channels coefficients of the ℓth-order Rice fading channels model. The closed-loop system is exponentially mean-square stable and prescribed H-infinity performance is guaranteed by designing the T-S fuzzy dynamic output feedback controller. The factorizations in the polynomial and the congruence transformation matrices are introduced to solve the LMIs, such that the controller gain matrices are determined. Finally, simulation examples are presented to show the effectiveness of proposed methods.

A 3-D Geometry-Based Stochastic Model for Unmanned Aerial Vehicle MIMO Ricean Fading Channels

In this article, we propose a novel 3-D geometry-based stochastic model (GBSM), i.e., a two-cylinder model, for unmanned aerial vehicle (UAV) multiple-input–multiple-output (MIMO) Ricean fading channels. The received signal is a sum of the Line-of-Sight (LoS) component, single-bounced (SB) rays at the UAV side, SB rays at the ground station side, SB rays on the ground, and double-bounced rays. This makes our model adaptable to a wide variety of UAV communication scenarios. More importantly, the proposed UAV model is the first two-cylinder model that considers ground reflections. Moreover, our model has the ability to investigate the impact of some unique UAV-related parameters (e.g., the UAV’s moving direction, UAV’s altitude, and antenna orientation) on channel characteristics in a 3-D nonisotropic propagation environment. From the proposed model, we derive and study some significant statistical properties, including the space-time correlation function (CF), Doppler power spectral density (PSD), envelope level crossing rate (LCR), and average fade duration (AFD). Some numerical results and interesting observations are provided, which can be considered useful guidance for the design of UAV-MIMO communication systems. Finally, the utility of our model is verified by the close agreement between the theoretical results and some example measurement data.

On Resource Allocation of Cooperative Multiple Access Strategy in Energy-Efficient Industrial Internet of Things

In this article, we investigate the jointly optimized resource allocation with hybrid multiple access in energy-efficient industrial Internet of Things (IIoT), where some devices (e.g., those for critical control devices) have higher transmission priority and stable energy supply while some devices (e.g., those for comprehensive sensors) may not. We consider a system model supporting wireless powered IIoT devices, with certain user terminal as a potential relay for the transmission between a hybrid access point and another user terminal. Constrained by the limited energy storage, the user needs to harvest energy before relaying and only the harvested energy is utilized for the following transmission. We propose a collaborative orthogonal and nonorthogonal multiple access protocol where two cooperation schemes with and without decoding the relay message are applied. Jointly considering time sharing in the transmission process, power splitting for simultaneous wireless information and power transfer, and transmit power allocation at the cooperative user, the achievable rate regions under the Rayleigh fading channel model are derived. Based on which, an optimization problem on resource allocation strategies is formulated and discussed. Both analytical and numerical results are provided, illustrating the impact of user geometry on the achievable rates as well as the optimal resource allocation with different cooperative strategies applied in different use cases. Aiming to enhance resource utilization, energy-efficient cooperation enables the combination of various transmission modes and networking classes in large scale networks, as well as a better use of ambient radio frequency signals for wireless powered transmissions.

Broad Coverage Precoder Design for 3D Massive MIMO System Synchronization

In this paper, we investigate broad coverage precoder design for 3D massive multi-input multi-output (MIMO) systems, where the base station (BS) is equipped with a uniform rectangular array (URA). We focus on the synchronization performance in the cell coverage. The flat fading channel model is formulated. The synchronization performance can be characterized by the missed detection (MD) probability. By considering the MD probability fairness in the cell, we formulate a criterion for the precoder design. Moreover, we consider the equal transmit power constraint on each antenna to efficiently utilize the power amplifier (PA) capacity of the BS. By using the manifold optimization framework, we design the precoder under the aforementioned criterion and constraint. Simulation results show that the fairness among all the users in this cell can be ensured. Compared with the precoders designed by half power beam-width (HPBW), the proposed scheme causes much less inter-cell interference and has a better synchronization performance.

Analysis and Design of Rateless Two-way Relay Networks Based on a Multiply-and-Forward Scheme

In this paper, we propose a rateless, three-stage, two-way multiply-and-forward (MF) relaying system over the Rayleigh flat fading channel, where two source nodes communicate with each other through a relay node and all nodes work on half-duplex and time-division mode. We thoroughly analyze the signals during all three stages in the proposed MF system and derive the closed-form symbol error rate (SER) expressions for an uncoded MF-two-way relay network (MF-TWRN). Furthermore, we provide the equivalent point-to-point fading channel model, which is employed to carry out the asymptotic performance analysis. We finally put forth an optimization model for the MF-TWRN with fountain codes. Simulation results show that our optimized degree distribution can provide outstanding performance for the MF-TWRN compared to those in the literature.

Genetic-Algorithm-Assisted Sliding-Mode Control for Networked State-Saturated Systems Over Hidden Markov Fading Channels.

The sliding-mode control (SMC) problem is studied in this article for state-saturated systems over a class of time-varying fading channels. The underlying fading channels, whose channel fading amplitudes (characterized by the expectation and variance) are allowed to be different, are modeled as a finite-state Markov process. A key feature of the problem addressed is to use a hidden Markov mode detector to estimate the actual network mode. The novel model of hidden Markov fading channels (HMFCs) is shown to be more general yet practical than the existing fading channel models. Based on a linear sliding surface, a switching-type SMC law is dedicatedly constructed by just using the estimated network mode. By exploiting the concept of stochastic Lyapunov stability and the approach of hidden Markov models, sufficient conditions are obtained for the resultant SMC systems that ensure both the mean-square stability and the reachability with a sliding region. With the aid of the Hadamard product, a binary genetic algorithm (GA) is developed to solve the proposed SMC design problem subject to some nonconvex constraints induced by the state saturations and the fading channels, where the proposed GA is based on the objective function for optimal reachability. Finally, a numerical example is employed to verify the proposed GA-assisted SMC scheme over the HMFCs.

Fading Channel Signal-to-Noise Ratio Limitation for Closed-Loop Stabilizability

Explicit communication channels in the feedback loop introduce new key elements such as channel input power, channel variable gain, channel bandwidth, additive channel noise, transmission rate, quantization, packet losses, etc. In this article, we propose a stationary signal-to-noise ratio (SNR) analysis for the fading channel model. The channel SNR can be connected with most communication issues such as channel input power, additive channel noise, and quantization noise. Recently, a power analysis has also been used to characterize for every instant the effect of packet losses and channel fading. Here, we propose an equivalent average channel model that preserves the first and second moments of a fading channel output in steady state. The proposed equivalency is stated initially in an open loop, and then, with the assumption of a plant model with a relative degree greater or equal to one, extended to the closed-loop feedback allowing a stationary SNR analysis. As a result, we can compute the fading channel SNR for closed-loop stabilizability limitation, and then consider the presence of disturbance and setpoint signals.

Performance evaluation of ED based spectrum sensing over fluctuating two ray fading channel

With the advancement in technologies like 5G and Internet of things (IOT), communication over non-traditional channel environment is growing. These technology enables large number of diverse devices to communicate in a given frequency band, hence high spectrum efficiency is desirable. Use of cognitive radio along with aforesaid technology is an obvious solution to achieve high spectrum efficiency. These communication scenarios are heavily affected by small scale fading and their behaviour could not be tracked accurately using conventional fading models. However recently developed fluctuating two ray fading (FTR) channel model can be used to model the behavior of mm wave in aforesaid fading environments. This paper investigates the performance of energy detection (ED) based spectrum sensing over FTR fading environments. To quantify the performance of ED, expression for Probability of detection and Area under the curve (AUC) have been derived. Then derived performance measures are studied in context with classical fading models, and a comprehensive analysis exhibits a degraded performance of ED based spectrum sensing in FTR fading environment, however improvements are shown by employing cooperative detection based spectrum sensing. At the end Monte Carlo simulations have been carried out to verify the validity of theoretically derived expressions.