Fading Channel Model Research Articles

Performance Analysis of Dense Small Cell Networks With Practical Antenna Heights Under Rician Fading

In this paper, we examine the combined impacts of distance-dependent Rician fading channel model and the absolute difference between the heights of base station (BS) and user equipment (UE) antennas on the coverage probability and the area spectral efficiency in an interference-limited ultra-dense (UD) small cell network (SCN). Exploiting distance dependent models for both path loss and multi-path fading, we show that in interference-limited UD-SCNs, Rician fading with variant Rician $K$ factor aggravates the performance loss caused by the difference between the heights of the BS and UE antennas in comparison to Rayleigh fading. In particular, we demonstrate that due to presence of the specular line-of-sight component in the Rician fading, both the coverage probability and the area spectral efficiency experience a steeper decline towards zero as the BS density increases. Our performance analysis has a prominent impact on the deployment of UD-SCNs in the 5th-generation of mobile networks, as it indicates that the right modeling of multi-path fading makes a significant difference when assessing the performance of UD-SCNs with non-identical UE-BS antenna heights.

Performance Analysis of Distributed Single Carrier Systems With Distributed Cyclic Delay Diversity

This paper investigates a distributed cyclic delay diversity (CDD) transmission scheme for cyclic-prefixed single carrier systems in non-identically and identically distributed frequency selective fading channels. The distinguishable feature of the proposed scheme lies in providing a transmit diversity gain while reducing the burden of estimating the channel state information, which is a challenging task in distributed and cooperative systems. To effectively use the distributed CDD scheme at the transmitters, two sufficient conditions are derived to eliminate the intersymbol interference at the receiver and leveraged to convert the multi-input single-output channel into a single-input single-output channel. These conditions allow the system to achieve the maximum diversity for frequency selective fading channels at a full rate. To achieve this maximum diversity, a fixed number of CDD transmitters are selected based on the channel conditions, symbol block size, and maximum time dispersion of the channel, and a new two-stage transmission mode is proposed. Based on the distributed CDD and the proposed selection schemes, a new expression for the signal-to-noise ratio at the receiver is obtained with the aid of order statistics, and then closed-form expressions for the outage probability and average symbol error rate (ASER) are derived. As far as the identically distributed frequency selective fading channel model is concerned, the achievable maximum diversity gain is proved, with the aid of asymptotic analysis, to be equal to the product of the total number of transmitters in the system and the number of multipath components. Link-level simulations are also conducted to validate the analytical expressions for outage probability, ASER, and maximum achievable diversity gain.

Dual QR decomposition in K-best sphere detection for Internet of Things networks

Internet of Things (IoT) in 5G communications is becoming more popular due to its robust features. Multiple input multiple output (MIMO) in IoT is playing a vital role nowadays with large and massive concepts. At the same time detection in such scenario is becoming complex day by day. Sphere decoding algorithms is one of the MIMO detection schemes used for achieving near-optimal maximum likelihood detection (MLD) performance. Preprocessing algorithms such as lattice reduction and QR-decomposition (QRD) has been widely used along with the variants of MIMO detection for achieving better bit error rate (BER) performance. This research paper proposes a novel dual QRD (DQRD) algorithm to obtain a universal low complex-lattice reduction aided (UL-LRA)—K-best sphere detection (KSD) for MIMO networks. The proposed algorithm is evaluated under additive white Gaussian noise flat fading and indoor task group ac (TGac-channel D) channel model. The results proved that the BER performance was enhanced as well as the average runtime complexity of LRA–KSD was reduced by 45 and 39% in a flat faded and channel D respectively compared to the optimal MLD using 16-QAM.

Average Error Rates and Achievable Capacity in Large Office Indoor Wireless Environments

Performance of common digital modulation techniques is analyzed over indoor wireless environments modeled through the recently proposed joint fading and two-path shadowing (JFTS) channel model. Mathematically tractable expressions for the instantaneous signal-to-noise ratio statistics, average bit error rates, and achievable channel cutoff rates are derived. Analytical results are used to: 1) investigate the impact of different JFTS model parameters and different modulation techniques on bit error rates and cutoff rates and 2) demonstrate how the JFTS channel model affects system performance in comparison with conventional empirical channel models. Finally simulation results are used to corroborate this analysis and evaluate the usefulness of such an analysis.

Troposcatter array signal detection based on frequency and spatial fading correlation

Troposcatter propagation mechanism is valuable for beyond-line-of-sight surveillance. However, channel fading caused by multipath scattering limits the sensing performance of the existing equipment. Based on the troposcatter multipath channel fading model on frequency and spatial domain, a modified covariance-based detector is proposed. The captured array signals are first maximal ratio combined in frequency domain and then weighted in spatial domain before accumulation. The performance of the proposed detector is derived theoretically and verified through simulations, showing significant improvement in the troposcatter scenario.

Performance Analysis and Relay Location Research of OFDM Free-Space Optical Communication Systems Under Moderate and Strong Turbulence

In this paper, based on the Gamma–Gamma channel model for describing moderate and strong atmospheric turbulence, we study the relay location of serial decode-and-forward relay systems and parallel decode-and-forward relay systems in free-space optical (FSO) communication. According to the orthogonal frequency-division multiplexing modulation (OFDM) and coherent detection demodulation technology, we develop a novel statistical fading channel model for relay FSO systems by incorporating the atmospheric turbulence, pointing errors, and path loss effects. Based on this channel model, we derive the closed-form expression of the outage probability in the FSO serial relay system and parallel relay system, using the Meijer G-function. The serial decode-and-forward relay system with different relay locations and parallel decode-and-forward relay system, which consider different number of links and different relay locations, are simulation analyzed under moderate and strong atmospheric turbulence. The performance of serial relay systems and parallel relay systems in free-space optical communication can be improved by optimizing the relay location.

A Novel MIMO Channel Model for Vehicle-to-Vehicle Communication System on Narrow Curved-Road Environment

This paper presents a generalized statistical multiple-input multiple-output (MIMO) fading channel model for a vehicle-to-vehicle (V2V) non-line of sight mobile communication system on narrow curved-road environments. The MIMO channel model captures the propagation effect that occurs when vehicles move towards a junction with a side road and corner scatterings. In this paper, both single- and double-bounced scattering mechanisms are considered and it is assumed that the scatterers are uniformly distributed in the form of narrow arcs outside the annular road. Our geometry-based channel model takes the exact relationship between the angle-of-arrival and the angle-of-departure into account. Thereafter, the statistical properties of the model are studied under the assumption of non-isotropic scattering. Analytical expressions of different parameters, such as the space---time-frequency cross-correlation function, Doppler power spectral density, and MIMO channel capacity are provided. Furthermore, the influence of model parameters on the performance of V2V communication system has been analyzed. The study provides a design layout of MIMO V2V communication systems with a wide-band spatial channel model enabling the performance analysis of new high-data-rate transmission schemes for narrow curved-road propagations.

End-to-End Backlog and Delay Bound Analysis for Multi-Hop Vehicular Ad Hoc Networks

Vehicular ad hoc network (VANET) is able to facilitate data exchange among vehicles and provides diverse data services. Intuitively, end-to-end backlog and delay bounds are considered significant metrics to evaluate the quality of service in VANETs. In order to analyze how the multi-hop transmission impacts the delay performance, we model the multi-hop service process into a virtualized single service in a min-plus convolution form. To obtain multi-hop end-to-end backlog and delay bound, we consider the stochastic network traffic characteristics and the highly dynamic channel environment under the static priority, first in first out, and earliest deadline first scheduling policies by applying the martingale theory. The IEEE 802.11p enhanced distributed channel access mechanism is also adopted to analyze the access performance in the MAC sub-layer. With three kinds of real wireless data traces, i.e., VoIP, gaming, and UDP, we verify our algorithm by considering the double Nakagami- $m$ fading channel model among vehicles. From the simulation results, we can see that the supermartingale end-to-end backlog and delay bound are remarkably tight to the real simulation results when compared with the existing standard bounds. The effect of the number of vehicles on the highway on the end-to-end backlog and delay performance is also investigated.

Video quality assessment for inter-vehicular streaming with IEEE 802.11p, LTE, and LTE Direct networks over fading channels

Availability of real time video streams capturing surrounding road conditions can not only aid automobile drivers and autonomous vehicles, they can also enhance road safety and improve traffic efficiency. However, provisioning of such services is challenging due to the harsh operational environments and stringent resource requirements of the applications. Nevertheless, radio access technologies like IEEE 802.11p, LTE, and LTE Direct have provisions for supporting real time streams for inter-vehicular communications.In this paper, we present an emulation-based study to demonstrate to what extent these networks are able to sustain real-time video streaming for vehicle-to-vehicle communication. We model highways and congested urban road scenarios using Ricean and Rayleigh fading channel models respectively, that closely mimic the real-life environment. We use H.264 codec for transcoding 360p and 480p videos at the sender vehicle, and then stream the transport segments over a real-time transport protocol. The quality of the video received at the target vehicle is assessed using two metrics: PSNR and SSIM. The emulation is done for varying encoding rates, relative speeds between vehicles, and inter-vehicular distances. We also find the link layer throughput that these networks can support. The results reveal that LTE Direct performs better than 802.11p, which in turn performs better than LTE. This study also provides insights into how to configure the radio and network parameters for delivering streaming services to vehicular networks.

Performance Analysis of Rayleigh and Rician Fading Channel Model

Performance Analysis of Rayleigh and Rician Fading Channel Model

Performance analysis of different Sum-of-Sinusoids simulation models for Rayleigh fading wireless channels

In this paper, extensive computations are conducted to assess the performance of five of the most accepted sum-of-sinusoids (SOS) simulation models for Rayleigh fading channels in terms of both accuracy and complexity. The statistical properties of first-, second- and higher-order are investigated using appropriate quantitative measures. This study is carried out for various numbers of sinusoids in order to find the better trade-off between complexity and accuracy. Moreover, for the correlation statistics, different numbers of simulation trials are used to better conclude about the ergodicity property of the different models. Numerical results demonstrate that, a recently introduced non-ergodic stochastic model exhibits a “likely-ergodic” behavior and its correlation functions vary little over the simulation trials. The variances of the time-averaged correlation functions are used to investigate the convergence behavior of the stochastic non-ergodic models. In this connection, analytical expressions of the variances of these functions are derived and compared with the simulated ones. In addition, the accuracy of the models is inspected through the mean and variance of the level crossing rate (LCR) and the average fade duration (AFD) relative errors.

Performance study of multi‐hop communication systems with decode‐and‐forward relays over fading channels

In this study, we investigate the performance of multi-hop systems with decode-and-forward relaying over fading channels. Specifically, the authors derive closed-form expressions for the probability density function, cumulative distribution function, and moment generating function of the end-to-end signal-to-noise ratio. In addition, they derive closed-form expressions for the end-to-end capacity (ergodic and outage) and average symbol error rate (coherent and non-coherent) of the system. The derived expressions can be transformed to study the performance of multi-hop communication systems over other well-known fading channel models by using the proper values for the and parameters. Finally, the performance of multi-hop scenario is analysed and investigated using numerical evaluation. Results are provided to illustrate the system's performance and the impact of number of hops and fading parameters on network performance. The derived expressions, in this study, are very important for the prediction of the performance metrics and statistics such that efficient designs of multi-hop wireless systems can be realised.

Energy Saving With Network Coding Design Over Rayleigh Fading Channel

In this paper, we investigate the energy minimization problem with and without network coding (NC) while satisfying the transmission rate requirements in a bidirectional cellular relay network, where a group of mobile users communicate with a base station across a relay node. In particular, we consider the Rayleigh fading channel model and adopt a comprehensive power consumption model in the radio frequency transmission. We show that the problem of minimizing the energy consumption of the bidirectional cellular relay network in NC and non-NC (NNC) schemes can be formulated as a unified sum of fractional programming problem, which is of high complexity to solve in general. Fortunately, we derive the sufficient condition under which the problem is a convex optimization problem, and thus can be solved quite efficiently. In the case that the energy minimizing problem is not convex, we decompose it into two subproblems, and propose an iterative algorithm to solve it. Simulation results show that in NNC and NC schemes, under all configurations of power parameters, the performance of the iterative algorithm is close to the exhaustive search method; but its running time is much shorter than the exhaustive search method. Furthermore, compared with the maximum power transmission policy, the iterative algorithm achieves a maximum energy reduction of 75%–82%. Last but not least, we compare the energy performance of NNC and NC schemes and discuss the effect of the iteration number and the relay node placement.

Tobit Kalman filter with fading measurements

This paper is concerned with the Tobit Kalman filtering problem for a class of discrete time-varying systems with both censored and fading measurements. The censored measurements are described by the Tobit measurement model and the fading measurements are characterized by the Lth-order Rice fading channel model capable of accounting for not only the packet dropout but also the communication phenomenon. The measurement fading occurs in a random way where the fading probabilities are regulated by a set of mutually independent Gaussian random variables. By resorting to the state augmentation technique and the orthogonality projection principle, the Tobit Kalman filter (TKF) is designed in the presence of fading measurements. In the course of filter design, several state-augmentation-induced terms are introduced, all of which can be calculated recursively or off-line. A numerical example concerning the estimation of ballistic roll rates is provided to illustrate the usefulness of the proposed filter.

Turbo Codes Performance Optimization over Block Fading Channels

In this paper, the best achievable performance of a turbo coded system on a block fading channel is obtained, assuming binary antipodal modulation. A rate 1/3 turbo code is considered, obtained by concatenating, through a random interleaver, an 8-states rate 1/2 and a rate 1 convolutional codes (CC). The block fading channel model is motivated by the fact that in many wireless systems the coherence time of the channel is much longer than one symbol interval, resulting in adjacent symbols being affected by the same fading value. The fading blocks will experience independent fades, assuming a sufficient separation in time, in frequency, or both in time and in frequency. This channel model is suitable for analyzing, forinstance, wireless communication systems employing techniques such as slow frequency-hopping, as is done in the Global System for Mobile communications (GSM).In such systems, coded information is transmitted over a small number of fading channels in order to achieve diversity. The best coded information allocations over a certain number of fading channels are evaluated, using the Eades-McKay algorithm to generate distinct permutations of a multiset. Bounds on the achievable performance due to coding are derived using information-theoretic techniques. In particular, in the paper an analytical method is proposed, based on the sphere-packing bounding technique, to assess the achievable performance. Moreover, simulation results are obtained and compared with the theoretical ones.

Hybrid ARQ: Does Fading Diversity Help?

In the literature on hybrid automatic repeat request (HARQ), the quasi-static channel model and the independent identically distributed (i.i.d.) fading channel model are typically used to model slow varying channel and fast varying channel, respectively. Even though the i.i.d. fading channel results in lower outage probability thanks to the diversity from independent fading, somewhat surprisingly, we analytically show that fading diversity hurts throughput of Chase combining with a single retransmission, for all possible initial attempted rates. We show similar trends across a wide range of initial attempted rates for HARQ with incremental redundancy. The results provide a better understanding of the impact of channel correlation and fading diversity on the throughput of HARQ and offer guidance for designing HARQ with multiple parallel processes.

Doubly Selective Fading Channel Modeling and Data Comparison for OFDM System

The mathematical model and the equivalent matrix representation of the doubly selective fading channel is proposed, A MATLAB based simulation is used to perform data comparison with the results of the MATLAB channel toolbox , based on both:• Deterministic functions (System functions).• Stochastic functions (Autocorrelation functions).

Doubly Selective Fading Channel Modeling and Data Comparison for OFDM System

Doubly Selective Fading Channel Modeling and Data Comparison for OFDM System

Design and Implementation of Wireless Channel Simulator Based on Shaping Filter

Currently, the reliability of wireless channel simulation is poor, and it cannot provide the interface for the actual physical equipment. Rayleigh fading channel model is used as the theoretical model in this paper, proposed a model based on shaping filter method and easy to implement for FPGA hardware. The model uses a computer to realize the shaping filter to reduce the consumption of the FPGA chip resources; linear interpolation method to achieve the Doppler frequency shift, Rayleigh fading. Test results show that the output of the hardware simulator fading characteristics consistent with the theoretical value, it can be used for wireless communication system simulation test.

A Non-Stationary Mobile-to-Mobile Channel Model Allowing for Velocity and Trajectory Variations of the Mobile Stations

In mobile-to-mobile (M2M) communication systems, both the transmitter and the receiver are moving with a certain velocity, which is usually assumed to be constant over time. However, in realistic propagation scenarios, the velocity of the mobile stations (MSs) is subject to changes resulting in a non-stationary fading process. In this paper, we develop a non-stationary narrow-band M2M multipath fading channel model, where the transmitter and the receiver experience changes in their velocities and trajectories. For this model, we derive expressions for the local autocorrelation function (ACF), the Wigner–Ville spectrum, the local average Doppler shift, and the local Doppler spread under isotropic scattering conditions. In addition, we investigate the correlation properties of the proposed model assuming non-isotropic scattering around the MSs. By relaxing the standard assumption of constant velocities of the MSs, this paper shows that the local ACF and the Wigner–Ville spectrum differ completely from known expressions derived for wide-sense stationary M2M channel models. Furthermore, it is shown that our model provides consistent results with respect to the Doppler spread. The proposed channel model is useful for the performance analysis of M2M communication systems under non-stationary conditions caused by velocity variations of the MSs.