Shadow Fading Research Articles

Average quality description of energy detection for generalised multipath shadowed κ – μ fading channels

The research addresses the problem of analytical description of energy detection procedure being one of the most favourable mechanism of white-space detection for cognitive radio and Internet-of-Things as well as unknown signal detection in radars and Unmanned Ground/Aerial Vehicle applications. A novel closed-form analytic solutions for average quality metrics (average receiver operating characteristic and area under the AROC curve) are derived for a generic shadowed fading channel model. Numerical simulations verify the computational effectiveness of the derived expressions compared to straightforward numerical integration and analytical treatment demonstrated their consistency with the several specific simplified cases widely used in engineering practice. The results enable one to estimate signal detection quality on the stage of wireless communications' system design.

On the Performance Analysis of Switched Diversity Combining Receivers over Fisher–Snedecor ℱ Composite Fading Channels

In some emerging wireless applications, such as wearable communication and low-power sensor network applications, wireless devices or nodes not only require simple physical implementation approaches but also require certain reliable receiver techniques to overcome the effects of multipath or shadowed fading. Switched diversity combining (SDC) systems could be a simple and promising solution to the above requirements. Recently, a Fisher–Snedecor composited fading model has gained much interest because of its modeling accuracy and calculation tractability. However, the performance of SDC systems over fading channels has not yet been analyzed in the open literature. To this end, this paper presents a systematic analysis of SDC systems over fading channels, including dual-branch switch-and-stay combining (SSC), multibranch switch-and examine combining (SEC), and SEC with post-examining selection (SECps) systems. We first investigate the statistical characteristics of univariate and bivariate distributions. Then, these statistical expressions are introduced into the above SDC systems and the statistical metrics of the output signal-to-noise ratio (SNR) for these systems are deduced in different fading scenarios. Thirdly, certain exact and novel expressions of performance criteria, such as the outage probability, the average bit error probability and average symbol error probability, as well as the average channel capacity for SSC, SEC, and SECps are derived. To find the optimum performance, optimal analysis is performed for the independent and identically distributed cases. Finally, numerical evaluation and simulations are carried out to demonstrate the validity of the theoretical analysis under various fading scenarios. According to the obtained results, the multipath fading parameter has more influence on the performance of SDC systems than the shadowing parameter, the correlation coefficient, or the average SNR. Importantly, the SDC systems can provide switched diversity gains only when the switching threshold is not too large or too small compared to the average SNR.

Network coverage using MI waves for underwater wireless sensor network in shadowing environment

In high permittivity media, such as underground, underwater, and biological tissues the electromagnetic (EM) wave fails to provide reliable communication due to high path loss. On the other hand, magnetic induction (MI) waves have the permeability similar to air in high permittivity medium. Unlike EM wave, in MI-based communication the effect of shadow fading on the obtainable transmission distance is not much pronounced. However, it may not be realistic to ignore the fading effect at higher frequencies considering a constant path loss while designing the link model. A channel model for underwater MI communication is proposed in this research work. The proposed channel considers the fading effect due to presence of large obstacles such as large underwater structures or seamounts, and old sunken ship on the coverage performance of an underwater wireless sensor network (UWSN).

Channel Characterization and Capacity Analysis for THz Communication Enabled Smart Rail Mobility

As a vital vertical industry empowered by the sixth-generation mobile communication system (6G), the vision of “smart rail mobility” requires a seamless wireless connectivity with the ultra high-data rate on the order of 100 Gbps or even more. This forms a strong driving force for exploiting the terahertz (THz) band where the available spectrum is massively abundant. In this paper, the smart rail mobility channel is characterized through ultra-wideband (UWB) channel sounding and ray tracing (RT) at 300 GHz band with an 8 GHz bandwidth in the five scenarios - Train-to-infrastructure (T2I), Inside station, Train-to-train (T2T), Infrastructure-to-infrastructure (I2I), and Intra-wagon. Corresponding channel characteristics such as path loss, shadow fading, Rician K-factor, root-mean-square delay spread, azimuth/elevation angular spread of arrival/departure, and cross-polarization ratio are extracted and analyzed. Based on realistic channel information, the performance of THz communication is investigated in terms of channel capacity for all above five scenarios with various antenna patterns and weather conditions (except Intra-wagon) - sunny, rainy, and snowy. The results provide valuable insights into the system design and evaluation for THz communication enabled Smart Rail Mobility.

Achievable Rate of NOMA-Based DF Relaying System With Imperfect SIC Over Imperfect Estimation of κ-μ Shadowed Fading Channels

A cooperative relaying system based on non-orthogonal multiple access (NOMA) is considered a promising technique in next-generation wireless communications. In this letter, we investigate the performance of a dual-hop decode-and-forward based on the NOMA relaying system in terms of achievable rate and power allocation coefficient over imperfect estimation of $\kappa $ - $\mu $ shadowed fading channels. Moreover, we consider imperfect successive interference cancellation at the relay in the first phase of transmission. Specifically, we derive the closed expressions for the average achievable rate and power allocation coefficient in terms of hypergeometric function. Finally, the numerical results confirm that our derived analytical results fit well the Monte Carlo simulations.

Performance of Relay Selection for NOMA Based Cooperative Networks Over Shadowed Fading Channels

In this work, a non-orthogonal multiple access (NOMA) based transmission between a source and two end users is examined over slow Generalized-K distributed (GKD) fading channels, where a single relay using decode-and-forward (DF) protocol is selected out of a set of full-duplex/half-duplex (FD/HD) multiple relays with the quality of service requirements. Two stage relay selection (RS), selecting a relay out of a set of relays providing service quality for user 1 to maximize data rate of user 2, is analyzed. Additionally, not only perfect successive interference cancellation (pSIC) but also imperfect SIC (ipSIC) is considered. Self-interference (SI) and ipSIC are assumed to be Nakagami-m distributed, additionally, Gaussian and channel gain dependent modelling of ipSIC are also considered. A new expression for cumulative distribution function (CDF) of GKD is provided, thereafter, robust approximated probability density function (PDF) and CDF for GKD based on generalized Gauss-Laguerre quadrature are derived. Since outage probability (OP) analysis with exact CDF is found to be unstable, approximated and asymptotic OP expressions are derived and validated via Monte Carlo simulation technique. Approximated CDF, in turn OP, expression is almost excellent. Unlike existing works, our expressions are unique and valid for all cases such as FD and HD together with pSIC and ipSIC, i.e. expressions are not given separately but in a single compact form. Effects of SI, ipSIC, fading and shadowing parameters on OP are demonstrated and it is also shown that RS can significantly reduce OP. Finally, nonzero diversity order is asserted and details are provided.

ANALISIS PERBANDINGAN NILAI SHADOW FADING PADA MODEL PROPAGASI STANFORD UNIVERSITY INTERIM (SUI) DENGAN METODE SIMULASI DAN DRIVE TEST

Stanford University Interim (SUI) is a propagation model developed by the institute ofElectrical and Electronic Engineers (IEEE). SUI propagation is divided into three conditions,namely conditions A, B and C. Of the three conditions, there is a correction factor (shadowfading) caused by buildings and trees whose values are 8.2 - 10.6 dB. This research willanalyze the comparison of the shadow fading value in the SUI propagation model. The methodused is a simulation using radio atoll planning and drive test measurements on the BTSLTE_Kampus_Udayana, LTE_Jimbaran and LTE_GapuraUdayanaRoad in the Bukit Jimbaranarea. The results of the drive test will be compared with the simulation in Conditions A, B and Cand look for the shadow fading value. The results obtained are for BTS LTE_Kampus_Udayana,LTE_Jimbaran and LTE_GapuraUdayanaRoad closer to condition A with an average differenceof -6.45 dBm, this is supported by the conditions in the three BTS settings where the contoursare hilly and the intensity of the trees and the buildings are high to moderate. As for the shadowfading value, the simulation results were obtained at 8.31 dB and the drive test was 11.47 dB.

Analysis on the vehicle‐induced path loss for millimetre‐wave V2V communication

Millimetre wave (mmWave) has great potential in vehicle-to-vehicle (V2V) communication to provide wide bandwidth and low latency. However, the biggest challenge for the use of mmWave is the high propagation path loss and susceptibility to blockage among vehicles, especially in urban streets. Vehicle shadow fading is quite common in the actual V2V communication. The non-line-of-sight scenarios are considered and the impacts of blocking vehicles on the characteristics of the V2V wireless channels are studied. The measurements are conducted for two scenarios. For the first scenario, a blocking truck is placed between transmitting and receiving cars. For the second scenario, a car is added as a reflector beside the truck. Based on the measurement results, a path loss model for the V2V communication is developed. In order to further verify the effects of building scattering, a simulation is setup and the results are consistent with the measured results.

Composite Fading Models Based on Inverse Gamma Shadowing: Theory and Validation

We introduce a general approach to characterize composite fading models based on inverse gamma (IG) shadowing. We first determine to what extent the IG distribution is an adequate choice for modeling shadow fading, by means of a comprehensive test with field measurements and other distributions conventionally used for this purpose. Then, we prove that the probability density function and cumulative distribution function of any IG-based composite fading model are directly expressed in terms of a Laplace-domain statistic of the underlying fast fading model and, in some relevant cases, as a mixture of well-known state-of-the-art distributions. Also, exact and asymptotic expressions for the outage probability are provided, which are valid for any choice of baseline fading distribution. Finally, we exemplify our approach by presenting several application examples for IG-based composite fading models, for which their statistical characterization is directly obtained in a simple form.

A Theoretical Analysis of Mobility Detection in Connectivity-Based Localization for Short-Range Networks

This paper presents a theoretical analysis of mobility detection in connectivity-based localization, which exploits connectivity information as range measurements to anchors at a known location, to investigate how well and how precise mobility can be detected with connectivity in short-range networks. We derive mobility detection, miss detection, and false alarm probabilities in terms of a mobility detection threshold, defined as the minimum distance to detect the mobility, under the shadow fading channel and arbitrary mobility models to take into account practical and general scenarios. Based on the derivations, we address the threshold determination with the criteria in the sense of the minimum average error from miss detection and false alarm. Numerical and simulation evaluations are performed to verify our theoretical derivations, to show that increasing anchor numbers can improve the mobility detection probability with a smaller detection threshold, and that the probabilities are bounded by the weights of miss detection and false alarm. This work is the first attempt at addressing the performance of mobility detection using connectivity, and it can be utilized as a baseline for connectivity-based mobility tracking.

Performance analysis of uplink massive spatial modulation MIMO systems in transmit-correlated Rayleigh channels

In this paper, the performance of uplink multiuser massive multiple-input multiple-output (MIMO) system with spatial modulation over transmit-correlated Rayleigh fading channel is investigated, where a large number of antennas are deployed at the base station and linear zero-forcing (ZF) receiveris employed for detection. By taking the transmit correlation and the randomness of shadow fading in to account, the bit error rate (BER) performance of the system is analyzed. According to the performance analysis, an approximated expression of overall average BER of the system is attained. Besides, asymptotic performance is studied and the corresponding BER expression at high signal-to-noise ratio is derived. On this basis, the diversity gain of the system can be obtained for performance evaluation. Simulation results show that the derived theoretical expressions matchthe simulated values well, which verifies the correctness of our analysis.

An Efficient Approach of Improving Path Loss Models for Future Mobile Networks in Enclosed Indoor Environments

Path loss is the primary factor that determines the overall coverage of networks. Designing reliable wireless communication systems requires accurate path loss prediction models. Future wireless mobile systems will rely mainly on the super-high frequency (SHF) and the millimeter-wave (mmWave) frequency bands due to the massive available bandwidths that will meet projected users’ demand, such as the needs of the fifth-generation ( $5G$ ) wireless systems and other high-speed multimedia services. However, these bands are more sensitive and exhibit a different propagation behavior compared to the frequency bands below $6~GHz$ . Hence, improving the existing models and developing new models are vital for characterizing the wireless communication channel in both indoor and outdoor environments for future SHF and mmWave services. This paper proposes an efficient improvement of the well-known close-in (CI) free space reference distance model and the floating-intercept (FI) model. Real measured data was taken for both line-of-sight (LOS) and non-line-of-sight (NLOS) communication scenarios in a typical indoor corridor environment at three selected frequencies within the SHF band, namely $14~GHz$ , $18~GHz$ , and $22~GHz$ . The research finding of this work reveals that the proposed models have better performance in terms of their accuracy of fitting real measured data collected from measurement campaigns. In addition, this work studies the impact of the angle of arrival and the antenna heights on the current and improved CI and FI models. The results show that the improved models provide better stability and sensitivity to the change of these parameters. Furthermore, the mean square error between the models and their improved versions were presented. Finally, this paper shows that shadow fading’s standard deviation can have a notable reduction in both the LOS and NLOS scenarios (especially in the NLOS), which means higher precision in predicting the path loss.

Enhancing Network Coverage Using Sensing Models in Wireless Sensor Network

WSN is a wireless network made of wireless sensors that is used to monitor the system, environmental or physical conditions. Network coverage is a critical Quality of Service parameter in the design of WSN. The sensing model used to design the network decides the coverage. In this paper, the effects on sensing coverage by multi-path fading and shadowing effects have been studied. A model for calculating coverage probability has been derived for an environment in presence of shadowing effect combined with multi-path fading. Deployment scheme directly influences the performance of the WSN. A multiple deployment scheme is proposed for shadowed and non-shadowed environments using Rayleigh and shadow fading. For the same value of sensing coverage, a significant depreciation in the required number of nodes is shown.

On Second-Order Statistics of the Composite Channel Models for UAV-to-Ground Communications With UAV Selection

Unmanned-aerial-vehicles (UAVs) are intended to be a vital part of beyond 5G (B5G) and 6G communication networks. UAV-to-ground communications in urban and populated areas are usually exposed to highly variable propagation conditions that can be often characterized by composite fading channels. This paper provides mathematical framework for the performance evaluation of UAV-to-ground communications over double-scattered single-shadowed (DS-SS), and double scattered double shadowed (DS-DS) fading channels. To analyse in details we provide probability density function (PDF), cumulative distribution function (CDF), average fade duration (AFD) and level crossing rate (LCR) of the product of double Nakagami-m (DN) and single inverse Gamma (SIG) random processes (RPs), as well as the product of DN and double inverse Gamma (DIG) RPs. Furthermore, the derived integral-form formulas for the second order (SO) statistical measures are approximated by Laplace integration (LI) and exponential LI in order to provide closed-form expressions. The impact of DS-SS and DS-DS fading types on the SO statistics of UAV-to-ground propagation scenario are thoroughly examined. Moreover, the impact of different values of DS-SS and DS-DS fading severities on the SO statistics are also taken into investigation. Lastly, the proposed UAV-to-ground model is extended to include the SO performance analysis of L-number of UAVs. All the analytical results for the SO statistics are confirmed by Monte-Carlo simulations.

Opportunistic Relay in Multicast Channels With Generalized Shadowed Fading Effects: A Physical Layer Security Perspective

Through ordinary transmissions over wireless multicast networks are greatly hampered due to the simultaneous presence of fading and shadowing of wireless channels, secure transmissions can be enhanced by properly exploiting random attributes of the propagation medium. This study focuses on the utilization of those attributes to enhance the physical layer security (PLS) performance of a dual-hop wireless multicast network over κ - μ shadow-fading channel under the wiretapping attempts of multiple eavesdroppers. In order to improve the secrecy level, the best relay selection strategy among multiple relays is employed. Performance analysis is carried out based on the mathematical modeling in terms of analytical expressions of non-zero secrecy capacity probability, secure outage probability, and ergodic secrecy capacity over multicast relay networks. Capitalizing on those expressions, the effects of system parameters, i.e., fading, shadowing, the number of antennas, destination receivers, eavesdroppers, and relays, on the secrecy performance are investigated. Numerical results show that the detrimental impacts caused by fading and shadowing can be remarkably mitigated using the well-known opportunistic relaying technique. Moreover, the proposed model unifies secrecy analysis of several classical models, thereby exhibiting enormous versatility than the existing works.

A Green Downlink Power Allocation Scheme for Cell-Free Massive MIMO Systems

In this article, we consider the problem of downlink power allocation in a cell-free massive multiple-input multiple-output (m-MIMO) communication system under spectral efficiency (SE) constraints for the users. From the perspective of green communications, the power allocation is formulated as an optimization problem where the aim is to maximize the sum SE as the objective function, while limiting the transmission power of each access point (AP) and imposing lower and upper bounds on the achievable SEs of different users. The resulting optimization problem is non-convex since the objective function is non-concave and the upper bounding constraints on user SEs are non-convex. To address these difficulties, we first derive a closed-form lower bound on the sum SE (objective function) and prove that it is a quasi-concave function. Then, we relax the unwieldy upper bounding constraints on the user SEs by replacing them with linear functions, which renders the optimization problem convex. An optimal solution to the relaxed problem is finally obtained by solving a sequence of convex feasibility programs. We evaluate the performance of the proposed downlink power allocation scheme through Monte Carlo simulations under the uncorrelated and correlated shadow fading models. The results show that for both models, the proposed algorithm can lead to a significant reduction in total power consumption compared to a benchmark approach, while accurately allocating power to the APs so that the SE constraint of each user is satisfied within the imposed bounds.

Performance Analysis of Multimedia Communications Hard Handoff over Fading Channel (Dept.E)

Handoff is an essential element of cellular communication systems. Efficient handoff algorithms can be considered as a cost-effective way of enhancing the capacity and the quality of service (QoS) of cellular systems. In this paper, the performance of no priority schemes and first- in- first -out (FIFO) handoff queuing schemes are considered. The performance of signal power multimedia communications (SPMC) is studied for multimedia communications queuing over a shadow and ricean fading channel. Computer simulations are performed to calculate the probability of new call blocking (Pb) and probability of handoff dropping (Pd) using different types of handoff strategies. Results indicate that the developed scheme reduce the probability of multimedia handoff call dropping as compared to no priority schemes with 18% in case of no fading, while it provides about 8% - 18% improvement in case of shadow fading channel, and it provides about 4% -14% improvement in case of ricean fading channel.

Problematic Issues of Intellectualizing the Control System of Autonomous Underwater Vehicles

The paper considers ways of intellectualizing the control processes of autonomous underwater vehicles (AUVs) by the example of solving three problems, on which the successful use of AUVs largely depends. The first problem is to create an AUV control system (CS), which ensures the achievement of the mission’s objective in the event of emergencies caused by both external and internal reasons, as well as deliberate and unintentional counteraction. It is shown that for the construction of the AUV’s CS the decentralized multi-agent structure is most suitable, in which each AUV system is an independent intellectual agent with its own control system. The control system must be equipped with a set of adaptive algorithms that ensure: control of AUV in the event of emergency situations, taking into account restrictions on the supply of electric energy, speed, accuracy of autonomous underwater navigation, range of hydro-acoustic communication; rational distribution of energy resources by AUV systems in accordance with the current situation; maintaining the functional stability of the AUV with a partial malfunction of technical means. The second problem is to create an underwater navigation system that ensures the accomplishment of AUV missions at great distances from the base point. Since AUV navigation using only on-board means (inertial navigation system and lag) does not provide the necessary accuracy, a prerequisite for AUV navigation over long distances is to conduct an observation using external sources, the choice of which in the circumstances is a non-trivial task. The third problem is to create a network underwater communication system (NUCS), which provides for the group application of AUVs. The ground analogue of NUCS is network radio communication. But if the latter is fairly well developed, then the former only takes the initial steps. This is due to both the later practical relevance of NUCS, and many fundamental physical factors that impede the development of NUCS, which include: a substantially limited frequency band that can be used in practice for signal transmission; a large propagation time of the hydroacoustic signal compared to the radio signal; the formation of extended shadow zones and fading of the connected signal due to its multipath propagation; significant Doppler distortions, fast variability of the characteristics of the hydroacoustic medium.

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.

Energy-efficient forwarding strategies for wireless sensor networks in fading channels

In the context of geographic routing in wireless sensor networks linked by fading communication channels, energy-efficient transmission is important to extend the network lifetime. To this end, we propose a novel method to minimize the energy consumed by one bit of information per meter and per second toward the destination in fading channels. Using the outage probability as a measure to maximize the amount of information delivered within a given time interval we decide energy-efficient geographic routing between admissible nodes in a wireless sensor network. We present three different approaches, the first is optimal and is obtained by varying both transmission rate and power, the other two are sub-optimal since only one of them is tuned. Simulation examples comparing the energy costs for the different strategies illustrate the theoretical analysis in the cases of log-normal and Nakagami shadow fading. With the method proposed it is possible to obtain significant energy savings (up to ten times) with respect to fixed transmission rate and power.