Rician Fading Research Articles

Static output feedback sliding mode control under rice fading channel: an interval type‐2 fuzzy modelling method

This work investigates the static output feedback sliding mode control (SMC) design problem of uncertain non-linear systems with Rice fading channels. The interval type-2 Takagi-Sugeno fuzzy modelling approach is exploited to express non-linear dynamics with uncertain parameters. As the wireless network between the sensor and the controller may be subject to channel fading, the premise variables are probably altered during their propagations. In such cases, a key issue is to synthesise a desired SMC law for stabilising the controlled non-linear systems. To this end, new membership functions are constructed via employing the fading measurements and the desired SMC law are subsequently synthesised. To deal with the disturbances in communication channels, the notion of input-to-state stable in probability (ISSiP) is utilised and sufficient criteria are deduced to guarantee the ISSiP of the resultant closed-loop systems and the reachability of the prescribed sliding surface. Finally, a simulation example illustrates the designed control strategy.

NOMA Receiver Design for Delay-Sensitive Systems

Successive interference cancelation (SIC) has been considered widely for the detection of downlink nonorthogonal multiple access (NOMA) signals. However, the sequential detection inherent to SIC process may introduce additional time delay for certain users, making the SIC unsuitable for communication systems with time delay constraints such as wireless networks that utilize unmanned aerial vehicles or low earth orbit satellites. Therefore, this article considers the performance of NOMA systems using a joint multiuser detector (JMuD), which can detect the signals of all users simultaneously and, hence, reduce the detection time requirements. The performance of the JMuD is evaluated in terms of bit error rate (BER), computational complexity, and processing time and compared to the SIC detector (SICD). The exact BER of the JMuD is derived analytically using quadrature phase shift keying modulation where closed-form expressions are derived for the two- and three-user scenarios for the air-to-ground channel, which is modeled as a Rician fading channels with order statistics. The obtained analytical results corroborated by Monte Carlo simulation confirm that the BERs of the JMuD and SICD are identical; however, the processing time of the SICD is 51% more than the JMuD for several cases of interest.

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.

Modeling and Analysis of Reconfigurable Intelligent Surfaces for Indoor and Outdoor Applications in Future Wireless Networks

Reconfigurable intelligent surface (RIS)-empowered communication is one of the promising 6G technologies that allows the conversion of the wireless channel into an intelligent transmit entity by manipulating the impinging waves using man-made surfaces. In this paper, the potential benefits of using RISs are investigated for indoor/outdoor setups and various frequency bands (from sub 6 GHz to millimeter-waves). First, a general system model with a single RIS is considered and the effect of the total number of reflecting elements on the probabilistic distribution of the received signal-to-noise ratio and error performance is investigated under Rician fading. Also for this case, the path loss exponent is analyzed by considering empirical path loss models. Furthermore, transmission models with multiple RISs are developed and analyzed for indoor and outdoor non line-of-sight (NLOS) scenarios. The conventional RIS selection strategies are also integrated for systems equipped with multiple RISs for the first time. Through extensive simulations, it is demonstrated that the RIS-assisted systems provide promising solutions for indoor/outdoor scenarios at various operating frequencies and exhibit significant results in error performance and achievable data rates even in the presence of system imperfections such as limited range phase adjustment and imperfect channel phase estimation at RISs.

Flexible OFDM Transceiver for Underwater Acoustic Channel: Modeling, Implementation and Parameter Tuning

Acoustic signals are a first choice in underwater communication since sound waves face very low attenuation in water compared to radio frequency (RF). However, the tendency of receiver to detect multipath signals (due to signals bouncing off surface or the bottom) induces large delay spreads and thus strong channel frequency selectivity. Additionally, rapid spatial and temporal variations in underwater acoustic (UWA) channel makes it hostile for communication systems based on single carrier modulation. Multicarrier modulation techniques, on the other hand, can greatly improve bandwidth utilization and help deal with time dispersal effects. Orthogonal frequency division multiplexing (OFDM) is a proven multicarrier communication system having capabilities to cope with frequency selectivity and delay spreads effectively. OFDM has started to get attention for being a simpler alternative to high complexity and high maintenance single carrier systems in UWA communication systems. This work proposes a Matlab model of an OFDM transceiver along with UWA channel characterization based on Rician shadowed fading model as it perfectly characterizes the way in which a shallow UWA channel behaves. Eventually, the proposed design allows implementation of various OFDM modulation methods and to perform Monte Carlo simulations for bit error rate comparisons together with the ability to tune multiple UWA channel parameters.

Channel Estimation Performance Analysis of Massive MIMO IoT Systems With Ricean Fading

This article analyzes the channel estimation performance of massive multiple-input–multiple-output (MIMO) Internet-of-Things (IoT) systems with Ricean fading. First, by utilizing the least squares (LSs) and minimum mean squared error (MMSE) estimation methods, we consider the relative channel estimation error (RCEE) between the IoT device and base-station, and provide the approximations of the expectation of RCEE ( ${\text {Exp}}_{\textrm {rcee}}$ ). Then, it is found that when the number of antennas $M$ becomes infinite, pilot contamination (PC) exists in both cases. However, for MMSE case, ${\text {Exp}}_{\textrm {rcee}}$ scales down by the inverse of Ricean $K$ -factor, and hence PC phenomenon disappears with a large Ricean $K$ -factor. Moreover, as $M\rightarrow \infty $ , the power scaling laws show that the pilot sequence power can be scaled down proportionally to $1/M^{\alpha }$ ( $\alpha >0$ ) with the MMSE case, where the performance is determined only by the Ricean $K$ -factor. Next, the channel hardening and favorable propagation effects are examined via analyzing the approximations of the variance of RCEE ( ${\text {Var}}_{\textrm {rcee}}$ ). Analysis implies that ${\text {Var}}_{\textrm {rcee}}$ decreases by $1/M$ when $M\rightarrow \infty $ . For a large Ricean $K$ -factor, ${\text {Var}}_{\textrm {rcee}}$ approaches a nonzero constant for the LS case and scales down by the inverse of the square of Ricean $K$ -factor for the MMSE case. Finally, all results are verified via Monte Carlo simulations.

Joint Power Control and LSFD for Wireless-Powered Cell-Free Massive MIMO

This paper considers wireless uplink information and downlink power transfer in cell-free massive multiple-input multiple-output systems. The single-antenna user equipments (UEs) utilize the energy harvested in the downlink to transmit uplink pilot and information signals to the multiple-antenna access points (APs). We consider Rician fading and maximum ratio processing based on either linear minimum mean-squared error (LMMSE) or least-squares (LS) channel estimation. We derive the average harvested energy by using a practical non-linear energy harvesting circuit model for both coherent and non-coherent transmission schemes. Furthermore, the uplink spectral efficiency (SE) is derived for all the considered methods and the max-min fairness problem is cast where the optimization variables are the AP and UE power control coefficients together with the large-scale fading decoding vectors. The objective is to maximize the minimum SE of the UEs’ under APs’ and UEs’ transmission power constraints. A novel alternating optimization algorithm with guaranteed convergence and improvement at each step is proposed to solve the highly-coupled non-convex problem.

Statistical CSI based design for intelligent reflecting surface assisted MISO systems

This paper considers an intelligent reflecting surface (IRS) aided multiple-input single-output communication system, where statistical channel state information (CSI) is exploited for transmit beamforming and IRS beamforming. A tight upper bound is derived for the ergodic capacity of the system. Based on which, the joint optimization of transmit beam and IRS beam are studied. Depending on whether a line-of-sight path exists between the access point and user, two different cases, namely, Rician fading and Rayleigh fading, are separately treated. Specifically, for the Rician fading case, an iterative algorithm is proposed, which is guaranteed to converge. For the Rayleigh fading case, closed-form designs are obtained for the transmit beam and IRS beam. Simulation results show the proposed beamforming scheme achieves similar performance as the benchmark algorithm requiring instantaneous CSI.

ICI and BEP analysis of hyperbolic FRFT based systems for satellite internet of things

In this paper, calculations of intercarrier interference (ICI) and bit error probability (BEP) of hyperbolic fractional Fourier transform (FRFT) based systems for the satellite internet of things applications, has been considered. Analysis of ICI power and BEP in Rician flat fading channels has been done, mathematically. Simulations approve that the systems based on the hyperbolic FRFT are resistant against carrier frequency offset in high-speed moving conditions. Also, in severely deep fade conditions, the hyperbolic FRFT based systems have an acceptable performance in the achieved bit error probability.

Performance analysis of smart grid dynamic HAN over Rician fading channel

In smart grid (SG) communications, the home area network (HAN) plays a vital role in managing data transmission among communicating devices through a smart meter (SM). Rician fading distribution closely replicates an indoor communication channel in SG HAN system. Thus, channel link is modeled as a Rician fading channel in this paper and Multi‐user selection scheme is employed in SM. Further, a closed‐form expression for average bit error probability (ABEP) performance of indoor dynamic HANs with communicating devices using phase‐shift keying (PSK) modulation is derived and analyzed the effect of traffic intensity, the total number of devices and Rician factor for the considered system. The expression for average channel capacity (ACC) of the SG HAN system is also derived and analyzed by varying the parameters of interest.

Outage Probability and Normalized SINR-Based Power Allocation over Rician Fading Channels

This paper considers power allocation in cellular networks over Rician fading channels. The goal is to improve the power consumption and energy efficiency as well as satisfy as many users as possible subject to user outage probability and normalized signal to interference plus noise ratio (SINR) constraints. The exact outage probability over Rician fading channels is determined using the moment-generating function (MGF). Further, upper and lower bounds on the outage probability are derived. These are used to characterize the relationship between outage probability and normalized SINR in Rician fading channels. Power allocation algorithms for power minimization and energy efficiency are proposed. Simulation results are presented to compare the performance of the proposed schemes with existing methods in terms of power consumption, throughput, energy efficiency, outage probability, and number of unsatisfied users.

Reconfigurable Intelligent Surfaces With Reflection Pattern Modulation: Beamforming Design and Performance Analysis

Recent research on reconfigurable intelligent surfaces (RISs) suggests that RISs can perform passive beamforming and information transfer (PBIT) simultaneously via smart reflections. In this paper, we propose an RIS-enhanced multiple-input single-output system with reflection pattern modulation (RPM) to achieve PBIT, where the joint active and passive beamforming is carefully designed by taking into account the communication outage probability. We formulate an optimization problem to maximize the average received signal power by jointly optimizing the active beamforming at the access point (AP) and passive beamforming at the RIS under the assumption that the RIS's state information is statistically known by the AP, and propose a high-quality suboptimal solution based on the alternating optimization technique. Moreover, a closed-form expression for the asymptotic outage probability of the proposed scheme in Rician fading is derived. The achievable rate of the proposed scheme is also investigated under the assumption that the transmitted symbols are drawn from a finite constellation. Simulation results validate the effectiveness of the proposed scheme and reveal the effect of various system parameters on the achievable rate. It is shown that the proposed scheme outperforms, in terms of achievable rate, the conventional RIS-assisted system without information transfer.

Outage Analysis for Terrestrial-Satellite Spectrum Sharing

This letter investigates the effect of the interference due to spectrum sharing between terrestrial and satellite systems. Based on a realistic coexistence model, we provide an exact closed-form outage probability expression of the satellite link in the presence of the terrestrial interference. We assume Nakagami fading both for terrestrial and satellite links, with an additional consideration for the shadowed Rician fading satellite link. Numerical results show that uncontrolled terrestrial interference can significantly degrade the outage performance of the satellite link. The obtained formulas are useful in predicting and preventing harmful interference when designing coexistence mechanisms for terrestrial and satellite systems.

Linear angular momentum multiplexing-conceptualization and experimental evaluation with antenna arrays.

Linear angular momentum multiplexing is a new method for providing highly spectrally efficient short-range communication between a transmitter and receiver, where one may move at speed transverse to the propagation. Such applications include rail, vehicle and hyperloop transport systems communicating with fixed infrastructure on the ground. This paper describes how the scientific concept of linear angular momentum multiplexing evolves from orbital angular momentum multiplexing. The essential parameters for implementing this concept are a long array at least at one of the ends of the link; antenna element radiation characteristics and the array element spacing relative to the propagation distance. These parameters are also backed by short-range measurements carried out at 2.4 GHz used to model the Rice fading channel and determine resilience to multipath fading.

Binary Orthogonal-Division Dual-Carrier Modulation for Hypersonic Vehicle Downlink Massive 2 ×MMIMO Systems With Noncoherent ML Detection

For reentry communication, the constellation rotation caused by high-dynamic plasma sheaths leads to unacceptable demodulation performances degradation for the quadrature amplitude modulation (QAM) signal. In this article, a noncoherent downlink $2\times M$ MIMO system over hypersonic vehicle integrated channel cascading the plasma sheath channel and the Rice fading channel is introduced, where each of the two transmitters has an antenna and a ground base station is equipped with a large number of antennas. For this system, a binary orthogonal-division dual-carrier modulation (BODM) method is proposed and an efficient noncoherent maximum likelihood (ML) receiver is developed without knowing the instantaneous channel state information (CSI). If the channel parameters are available to transmitters, the optimal power allocation can be achieved by using the minimum Euclidean distance (MED) criterion. A brief discussion on how to extend these results to the multiple-carrier system is presented. Simulations demonstrate that the new system significantly reduces the average bit error rate (BER), the optimal power allocation scheme is far superior to an equal power allocation scheme, and the system is robust against the plasma sheath attenuation with moderate received antennas or large line-of-sight (LOS) components.

H∞ control for a class of two-dimensional linear systems with fading measurements

In this paper, the [Formula: see text] control problem for a class of two-dimensional (2-D) linear discrete-time systems with fading measurements is investigated, where the 2-D systems are described by a Roesser model. The Rice fading model is applied to describe the fading phenomenon and the coefficients of the model satisfy the independent identical Gaussian distributions. The main objective of this paper is to design a controller such that both the 2-D closed-loop system is exponentially mean-square stable and the prescribed [Formula: see text] performance is guaranteed under the condition of applying the attenuation signals. By utilizing the Lyapunov stability theory and the linear matrix inequalities (LMIs) techniques, sufficient conditions are conducted to guarantee the desired tracking performance. Based on such conditions, the gain matrix of the proposed controller is obtained. Finally, the effectiveness of the proposed control schemes is illustrated with a numerical example and a Darboux equation example.

A WPT-Enabled UAV-Assisted Condition Monitoring Scheme for Wireless Sensor Networks

In this paper, a resource allocation and data gathering scenario of an unmanned aerial vehicle (UAV) assisted wireless powered sensor network is investigated, in which the sensor nodes (SNs) are remotely powered by power beacons (PBs) via radio-frequency wireless power transmission (RF-WPT). A time-block structure with two phases is proposed to accommodate operations in the proposed system. During Phase-I, SNs harvest energy from PBs and periodically send its sensed data to the selected cluster heads (CHs). In Phase-II, an UAV collects the data from CHs to be delivered to the data sink for further processing avoiding the need for long range transmission and multi hop communication to the data sink. Then, a closed-form expression for outage probability of the proposed system over Rayleigh and Rician fading channels is derived. Next, outage probability minimization problem is formulated to obtain optimal time allocation for RF-WPT energy harvesting to improve the system performance. Due to the complexity of the problem, Lagrangian duality method is used to develop an asymptotic optimal solution with less execution complexity avoiding complex brute force/ exhaustive search approach. Furthermore, a heuristic method is presented to further lower the computation complexity. Simulation results reveal the superiority of the proposed methods compare to brute force/ exhaustive search approach via analysis, comparison and insights of the system performance results. Finally, the performance superiority of the proposed system is demonstrated with compare to identified baseline WSNs.

Fuzzy Model-Based Asynchronous Control for Markov Switching Systems with Stochastic Fading Channels

This work investigates the asynchronous control for fuzzy Markov switching systems (MSSs) with randomly occurring fading channel. By resorting to a T-S fuzzy model, the nonlinear MSSs can be handled. Meanwhile, in the unreliable network, the Rice fading model is proposed to capture the randomly occurring channel fading, which covers packet dropouts and network-induced delays as special cases. In light of the hidden Markov model, the asynchronous phenomenon of controller is taken into consideration, and asynchronous fuzzy controller is obtained. In the end, a numerical example and a single-link robotic arm model are applied to demonstrate the validity of the derived results.

Task offloading and resource allocation for UAV-assisted mobile edge computing with imperfect channel estimation over Rician fading channels

In this paper, we develop task offloading and resource allocation scheme for unmanned aerial vehicle (UAV)-assisted mobile edge computing (MEC) system with channel estimation errors over Rician fading channels. The objective is to maximize the system utility with constrained network stability, transmit power, and data arrival rate. We consider a general multi-user UAV-assisted MEC system based on frequency division multiple access (FDMA), and we assume that the computation tasks are split into separate tasks and offloaded to the server for computing. We study stochastic computational resource management based on the Lyapunov optimization algorithm. The optimal transmit power and bandwidth allocation for computation offloading are obtained alternately, and the optimal computation task admission at each time slot and the optimal value of the auxiliary variable are derived. Simulation results verify the effectiveness of the proposed scheme in the paper and evaluate the influence of various parameters to the system performance.

Analysis and Optimization of an Intelligent Reflecting Surface-Assisted System With Interference

In this paper, we study an intelligent reflecting surface (IRS)-assisted system where a multi-antenna base station (BS) serves a single-antenna user with the help of a multi-element IRS in the presence of interference generated by a multi-antenna BS serving its own single-antenna user. The signal and interference links via the IRS are modeled with Rician fading. To reduce phase adjustment cost, we adopt quasi-static phase shift design where the phase shifts do not change with the instantaneous channel state information (CSI). We investigate two cases of CSI at the BSs, namely, the instantaneous CSI case and the statistical CSI case, and apply Maximum Ratio Transmission (MRT) based on the complete CSI and the CSI of the Line-of-sight (LoS) components, respectively. Different costs on channel estimation and beamforming adjustment are incurred in the two CSI cases. First, we obtain a tractable expression of the average rate in the instantaneous CSI case and a tractable expression of the ergodic rate in the statistical CSI case. We also provide sufficient conditions for the average rate in the instantaneous CSI case to surpass the ergodic rate in the statistical CSI case, at any phase shifts. Then, we maximize the average rate and ergodic rate, both with respect to the phase shifts, leading to two non-convex optimization problems. For each problem, we obtain a globally optimal solution under certain system parameters, and propose an iterative algorithm based on parallel coordinate descent (PCD) to obtain a stationary point under arbitrary system parameters. Next, in each CSI case, we provide sufficient conditions under which the optimal quasi-static phase shift design is beneficial, compared to the system without IRS. Finally, we numerically verify the analytical results and demonstrate notable gains of the proposal solutions over existing ones.