Path Loss Exponent Research Articles

MEASUREMENTSBASEDEVALUATION OF PATHLOSSEXPONENTS IN URBAN OUTDOORENVIRONMENTS

In wireless networks, propagation models are used to assess the received power signal and estimate the propagation channel. These models depend on the pathloss exponent (PLE) which is one of the main parameters to characterize the propagation environment. Indeed, in the wireless channel, the path loss exponent has a strong impact on the quality of the links and must therefore be estimated with precision for an efficient design and operation of the wireless network. This paper addresses the issue of path loss exponents estimation for mobile networks in four outdoor environments. This study is based on measurements carried out in four outdoor environments at the frequency of 2600 MHz within a bandwidth of 70 MHz. It evaluates the path loss exponent, and the impact of obstacles present in the environments. The parameters of the propagation model determined from the measurements show that the average power of the received signal decreases logarithmically with the distance. We obtained path loss exponents values of 4.8, 3.53, 3.6 and 3.99 for the site 1, site 2, site 3 and site 4, respectively. Clearly the density of the obstacles has an impact on the path loss exponents and our study shows that the received signal decrease faster as the transmitter and receiver separation in the dense environments.

Wideband Channel Characterization for 6G Networks in Industrial Environments.

Wireless data traffic has increased significantly due to the rapid growth of smart terminals and evolving real-time technologies. With the dramatic growth of data traffic, the existing cellular networks including Fifth-Generation (5G) networks cannot fully meet the increasingly rising data rate requirements. The Sixth-Generation (6G) mobile network is expected to achieve the high data rate requirements of new transmission technologies and spectrum. This paper presents the radio channel measurements to study the channel characteristics of 6G networks in the 107–109 GHz band in three different industrial environments. The path loss, K-factor, and time dispersion parameters are investigated. Two popular path loss models for indoor environments, the close-in free space reference distance (CI) and floating intercept (FI), are used to examine the path loss. The mean excess delay (MED) and root mean squared delay spread (RMSDS) are used to investigate the time dispersion of the channel. The path loss results show that the CI and FI models fit the measured data well in all industrial settings with a path loss exponent (PLE) of 1.6–2. The results of the K-factor show that the high value in industrial environments at the sub-6 GHz band still holds well in our measured environments at a high frequency band above 100 GHz. For the time dispersion parameters, it is found that most of the received signal energy falls in the early delay bins. This work represents a first step to establish the feasibility of using 6G networks operating above 100 GHz for industrial applications.

Estimation of the Path-Loss Exponent by Bayesian Filtering Method.

Regarding wireless sensor network parameter estimation of the propagation model is a most important issue. Variations of the received signal strength indicator (RSSI) parameter are a fundamental problem of a system based on signal strength. In the present paper, we propose an algorithm based on Bayesian filtering techniques for estimating the path-loss exponent of the log-normal shadowing propagation model for outdoor RSSI measurements. Furthermore, in a series of experiments, we will demonstrate the usefulness of the particle filter for estimating the RSSI data. The stability of this algorithm and the differences in determined path-loss exponent for both method were also analysed. The proposed method of dynamic estimation results in significant improvements of the accuracy of RSSI values when compared with the experimental measurements. It should be emphasised that the path-loss exponent mainly depends on the RSSI data. Our results also indicate that increasing the number of inserted particles does not significantly raise the quality of the estimated parameters.

Developed channel propagation models and path loss measurements for wireless communication systems using regression analysis techniques

BackgroundThe development of powerful and flexible management addresses is due to the improvement of deeply reliable gadgets and the advancement of the concept of cellular. The cellular principle was a major way of solving the wavelength crowding problem and the user capacity. It offered high capacity without major technological changes with limited allocation in spectrum. Wireless communication is an innovation in media transmission that allows remote transmission in all types of terrain between convenient gadgets. For estimating a transmitter 's radio coverage area, propagation models that anticipate the mean signal strength for an arbitrary transmitter–receiver separation distance are crucial as they are called large-scale propagation models so even though they define the average signal strength over long periods of time and large distances from the transmitter.ResultsDeveloped propagation models are presented according to the measured path loss values in exemplary urban and suburban areas at the operating frequency of 3.5 ghz by using the regression analysis. The measurements are implemented by using a spectrum analyzer FSH6 to get the channel response as shown in the stated tables and graphs. Based on the obtained results, it was observed that the path loss could be calculated as a function of distance and during the practical measurements 32 m was precise as a presumption for the break point distance. The values of path loss exponent (n) are defined and calculated for both of urban and suburban regions. Measurements results are analyzed and compared in order to study their influence for every specific environment. It was noticed that any radio signal will suffer attenuation when it travels from the transmitter to the receiver as a variety of various phenomena give rise to this radio path loss.ConclusionsThe interaction between both the electromagnetic radiation and the environment tends to decrease the quality of the signal being sent from the transmitter to the destination which causes the loss of the path. Propagation models are the basis for channel estimation, as they attempt to identify how a radio transmission changes from the transmitter to the receiver throughout its path. The gained results from this research will be supportive for the arrangement of network planners and researchers as proof and directory materials before future location establishment.

Performance analysis on a cooperative transmission scheme of multicast and NOMA in cache‐enabled cellular networks

Caching popular contents at base stations (BSs) can effectively avoid redundant data traffic and improve backhaul capacity. Techniques such as multicast (MC) and non-orthogonal multiple access (NOMA) can significantly improve spectral efficiency by delivering popular contents to multiple users using a single channel. Therefore, we propose a cooperative transmission scheme of MC and NOMA in cache-enabled wireless cellular networks. First, we derive the probability mass function (PMF) of the number of channels in the MC mode as well as the joint PMF of the number of channels and number of NOMA users in the NOMA mode. Second, we analyse the successful transmission probabilities of the two modes by utilising tools from stochastic geometry. Finally, with the derived probabilities using the two modes, we obtain the total successful transmission probability based on probability theory. The quasi-closed form expression of the successful transmission probability is obtained in a special case, where the noise is neglected, and the path-loss exponent is set to be four. Simulation results validate the accuracy of the analysis and demonstrate the performance gain due to the proposed cooperative transmission scheme of MC and NOMA.

Radio Channel Modeling in a Ship Hull: Path Loss at 868 MHz and 2.4, 5.25, and 60 GHz

This letter presents the analysis of a channel sounding campaign in the hull of a bulk carrier vessel at sub-6 GHz frequencies 868 MHz and 2.4 and 5.25 GHz as well as millimeter-wave (mmWave) frequency 60.48 GHz. For the sub-6 GHz frequencies, path loss (PL) is measured using omnidirectional antennas. The measured PL is fitted to a one-slope PL model that takes into account attenuation due to engine room floor crossings, obstructions, and walls. The fitted model has a reference PL lower than free space and a PL exponent around 1.2. For mmWave wireless communication, high gain directive antennas are typically used. Therefore, the directive radio channel for line-of-sight (LOS) communication is measured using the Terragraph channel sounder and an antenna beamwidth dependent PL model is created. At mmWave frequencies, LOS PL in the vessel is close to PL in a free-space environment, but angular spread values are lower compared to other indoor scenarios.

Performance study of path loss models at 14, 18, and 22 GHz in an indoor corridor environment for wireless communications

The critical rule to achieve extremely high peaks of data transmission is the availability of a tremendous amount of bandwidth. The super high frequency (SHF) and the millimeter-wave (mmWave) frequency bands are the candidates for the deployment of the 5G cellular system and for satisfying future needs due to their massively available blocks of contiguous raw bandwidth that is capable of supporting additional data traffic for multimedia services. This research paper presents propagation measurements at three frequencies above 6 GHz, which are 14, 18, and 22 GHz frequency bands. The measurements were carried out or both line-of-sight (LOS) and non-line-of-sight (NLOS) communication scenarios in an indoor corridor environment to present frequency- and distance-dependent wireless channel models. Moreover, this study presents, investigates, and compares the performance of two well-known path loss prediction models; the single frequency close-in (CI) free space reference distance model and the single frequency floating intercept (FI) model. The LOS comparison study shows that the CI and FI models provide comparable and accurate estimates that fit the real measured data for the frequency bands selected. Furthermore, the study investigates the behavior of the path loss exponent (PLE) and the FI model parameters as a function of the reception angle of arrival (AoA) in the NLOS scenario. It is observed from this work that the path loss models' parameters exhibit symmetrical behavior around 180° AoA. The FI model provides the same standard deviation values as the CI model in the LOS scenario. In contrast, the FI model offers a notable reduction(up to 2.84 dB) compared to the CI model in the NLOS scenario. Finally, the LOS and NLOS results reveal that the CI and FI models can be trusted as good path loss models for corridor environments and exhibit stable behavior over measured distances and frequencies.

One‐to‐one non‐linear transformation for RSS‐based localization with unknown transmit power

For most of the positioning algorithms, based on the received signal strength, the objective function of the estimator is linearized so that the conventional least square algorithm can be executed. This would necessitate using a data model containing many noisy elements which implicitly violates the least squares assumptions. To avoid this violation, an optimized data modelling would have to be set up as shown in this paper. The authors then trivially provide the solution of this new least square problem which is still a primary coarse position estimation because of ignoring the non-linear relationships existing among parameters of the estimation. To extract quantitative information from these non-linear relationships, the authors also propose two new signal space points for using Taylor-series expansion as effectively as possible in accordance of the new data model. The proposed algorithms work without any knowledge about the transmit power. The performance evaluation of the proposed idea indicates that the new suggested estimators perform significantly better than the other existing linear position estimators for a large range of noise variance and path-loss exponent values.

Achievable Rate Characterization of NOMA-Aided Cell-Free Massive MIMO With Imperfect Successive Interference Cancellation

This paper investigates the throughput improvement of cell-free massive multiple-input multiple-output (MIMO) systems by non-orthogonal multiple access (NOMA) for future cellular networks under stochastic access point and user locations. In this context, the node locations are modeled with Poisson point processes. The time division duplexing mode is employed, and uplink channels are estimated locally using uplink pilots. Furthermore, unique pilot sequences are used between NOMA clusters, while pilot reuse occurs within each cluster to strike a balance between the training overhead and the number of clusters. Matched-filter-based precoding is utilized for downlink transmission. The aggregate received signal is analytically characterized by deriving the moment generating function and approximations via moment matching. Then, the asymptotic achievable rates of the NOMA users are derived, thereby quantifying the adverse impact of error propagation owing to imperfect successive interference cancellation. Special scenarios with prior downlink channel state information and log-distance power control are also considered. We show that NOMA greatly increases the achievable average rate, especially under low path loss exponents and dense networks, while user fairness may be boosted by the adoption of a log-distance transmit power control scheme with proper parameter selection (i.e. lower values for the power control parameter).

Dynamic optimized cooperation in multi‐source multi‐relay wireless networks with random linear network coding

The authors present a strategy that improves the reliability of data transmission from multiple sources towards a destination D via multiple relays over wireless channels. After the broadcast phase, the destination selects the best cooperative direct link sources with the highest instantaneous signal-to-noise ratio , then generates and sends the random linear network coding coefficient matrix to the relays. After receiving the random linear network coding–coded symbols (packets) from the relays, D completes the reception and decoding of all source nodes packets. Monte Carlo simulations are conducted with Galois field (GF) () symbols ( = 2, 4 and 8) and the results are compared with the scenario of static cooperative direct links. An important decrease of symbol error rate (SER) is achieved. Furthermore, the efficiency of this approach is confirmed for the whole range of possible values of path loss exponent on direct links, that is, all types of environment between source nodes and destination D.

Network Planning in Deep Fading Area is a Research Challenge

A modified path loss prediction model for deep fading area is presented and compared with standard indoor path loss model. An academician perspective, it may not be feasible to design a network for its maximum capacity & coverage under deep fading environment. The above facts reveals us to carry out real time analysis of network using advance set up and predict minimum detectable signal in deep fading area. In this paper, monitoring of signal at different frequency and power under deep fading condition is carried out to check and access the reality of signal variation. The temporal variation of signal is recorded continuously to check the minimum availability of signalfor mathematical analysis. The statistical analysis on recorded data provides large variation in standard deviation (13.16 to 17.25 dB) and the path loss exponent tends to a new value of 4.8. The received signal strength for LTE network goes beyond − 74 to − 103 dBm.Path loss at different frequency, power and distance is calculated using ITU model, Log Distance model and new model is proposed for fading area. The large variation in path loss (9 to 283 dB) for different networks is plotted for fading area under study.The improvement of signal strength was observed slightly by 10 dBm when base station antenna was down tilted by − 20. The change in signal strength after down tilting the antenna is also recorded and presented. Such small increment in signal strength may allow network to provide better connectivity in fading area with good quality of service (QoS).

Millimeter-Wave Propagation Measurement and Modeling in Indoor Corridor and Stairwell at 26 and 38 GHz

Accurate propagation characteristics are essential for future indoor millimeter-wave (mmWave) small cell network planning. This paper presents propagation measurements at 26 GHz and 38 GHz which are important candidate bands for fifth generation mmWave communication. Measurements are conducted in an indoor corridor, as well as a stairwell whose mmWave channel is seldom investigated before. In these measurements, an omnidirectional biconical antenna is used as transmitter and a steerable directional horn antenna is used as receiver. The directional and omnidirectional path loss exponents, shadow factors, cross-polarization discrimination ratios and root-mean-square delay spreads are analyzed for both line-of-sight and non-line-of-sight scenarios in both co-polarization and cross-polarization, and these characteristics are compared for different frequencies and environments. It is found obvious depolarization phenomenon in non-line-of-sight scenario for higher frequency. Compared to the corridor, the stairwell has larger path loss exponents and root-mean-square delay spreads, and the depolarization is also more evident in stairwell. The results in this paper are beneficial to building efficient and robust indoor mmWave communication systems.

A Multi-Frequency Investigation of Air-to-Ground Urban Propagation Using a GPU-Based Ray Launching Algorithm

Unmanned Aerial Vehicles (UAV), also known as “drones”, are attracting increasing attention as enablers for many technical applications and services, and this trend is likely to continue in the next future. When compared to conventional terrestrial communications, those making use of UAVs as base- or relay-stations can definitely be more useful and flexible in reaction to specific events, like natural disasters and terrorist attacks. Among the many and different fields, UAV enabled communications emerge as one of the most promising solutions for next-generation mobile networks, with a special focus on the extension of coverage and capacity of mobile radio networks. Motivated by the air-to-ground (A2G) propagation conditions which are likely to be different than those experienced by traditional ground communication systems, this paper aims at investigating the narrowband properties of the air-to-ground channel for 5G communications and beyond by means of GPU accelerated ray launching simulations. Line of sight probability as well as path loss exponent and shadowing standard deviations are analysed for different UAV flight levels, frequencies and dense urban scenarios, and for different types of on board antennas. Thanks to the flexibility of the ray approach, the role played by the different electromagnetic interactions, namely reflection, diffraction and diffuse scattering, in the air-to-ground propagation process is also investigated. Computation time is reported as well to show that designing UAV communication networks and optimising their performances in a fast and reliable manner, might avoid exhausting – multiple - measurement campaigns.

Performance Analysis of Sub-GHz System for IoT Applications

This article reports a sub-GHz, 868MHz, battery operated miniature sensor node with a fabricated helical Printed Circuit Board (PCB) and a third party whip antenna for Internet of Things (IoT) applications. CC1310 System on Chip (SoC), a sub-GHz family wireless microcontroller, is used to design the system. A HDC 1050 temperature and humidity sensor is interfaced with the microcontroller. The system has the desirable benefits of being small and inexpensive, long battery life and capable of long transmission range. The path loss exponent is calculated from Received Signal Strength Indicator (RSSI) values in two environments - free space and across concrete obstructions. A wireless sensor network is incorporated into a cloud platform for real time monitoring, and web application has been developed for data display and analysis. To validate the proposed IoT system, the measured data is compared with an independent meteorological data set from the Indian Meteorological Department, Cyclone Warning Centre, Visakhapatnam.

Deterministic 5G mmWave Large-Scale 3D Path Loss Model for Lagos Island, Nigeria

5G millimeter wave (mmWave) application in mobile connectivity to realize high-speed, reliable communication is attributed with high path loss. This paper presents a detailed 3D ray-tracing technique at 28 GHz for Lagos Island to investigate five unique path loss scenarios: path loss, free space path loss with antenna pattern, free space path loss without antenna pattern, excess path loss with antenna pattern, and the excess path loss without antenna pattern for an urban environment. The Close-In (CI) model, Floating Intercept (FI) path loss model, and a root mean square error (RMSE) are used to model and evaluate the best path loss model for Lagos Island. The average achieved FI ( $\alpha,\beta, \sigma $ ) parameters were 189.92352, 0.1654, and 0.66948, While the average CI ( $\eta,X\sigma $ ) parameters were 2.309355 and 56.236425. From all the scenarios evaluated, the lowest path loss exponent achieved was 0.45, while the highest path loss exponent was 3.8. We have established that the FI path loss model accurately characterizes path loss for the Lagos Island environment with the lowest RMSE of 0.0359 dB and the highest RSME of 0.0997 dB. In contrast, the CI model over-predict the path loss at 28 GHz with the lowest RMSE of 0.0495 dB and the highest RMSE of 2.2547 dB. This work opens up a new area of research on mm-Wave at 28 GHz in Lagos Island, and the results obtained from this work can be used to benchmark future studies on mmWave in a similar environment.

Channel Modeling and Over-the-Air Signal Quality at 3.5 GHz for 5G New Radio

With the next generation of mobile communication being trialled across the world, 5G New Radio (NR) promises to provide a flexible radio interface that fits a diverse range of use cases. As trials and pilots progress, propagation studies are required that evaluate electromagnetic (EM) propagation effects for 5G NR signals. In this article, 5G NR signals are used to evaluate the over-the-air (OTA) error vector magnitude (EVM) within a line-of-sight (LoS) rural/urban environment. For the same receiver locations, time dispersion and propagation loss were measured via the root mean square (RMS) delay spread and path loss. The transmitter−receiver distance investigated ranged from $\mathrm {60~m}$ to $\mathrm {450~m}$ . From the measurement campaign, the path loss exponent (PLE) using a directional antenna at the receiver was 1.98, and 1.82 with an omnidirectional antenna. The root mean square error (RMSE) of the floating intercept/close-in (FI/CI) models for the path loss was 4.96/4.74 and 3.84/3.23 for directional and omnidirectional receivers. The delay spread using a cross polar configuration showed significant increase and a dependency of the delay spread on the path loss was observed. For the measurement route, the mean delay spread was $\mathrm {24~ns}$ and $\mathrm {35~ns}$ for directional and omnidirectional measurements. With regards to the EVM, 16 and 64-QAM transmissions were robust along the entire route for directional and omnidirectional antennas, whereas 256-QAM worked in locations where there was minimal obstruction to the propagation path. The average EVM (%) for 16, 64 and 256-QAM measured along the route was 4.5/5.3/3.9 and 3.4/4.3/3.6 for omnidirectional and directional antennas. The OTA results also show that using a directional antenna (as the receiver) significantly improves the obtainable signal quality of 5G NR signals and also reduces outages for higher modulation schemes. With the measurement results presented, system designers can design efficient receivers, estimate coverage and adequately provision services using 5G NR on the sub-6 GHz frequency band.

Power-Location Optimization for Cooperative Nomadic Relay Systems Using Machine Learning Approach

The exact expressions and simple tight lower bounds for end-to-end average symbol error rate (ASER) and outage probability (OP) are derived in amplify-and-forward (AF) source-relay-destination cooperative link, provided that source-destination path is correlated with the source-relay path. Afterward, an optimum power allocation (PA) and relay location (RL) algorithm is presented. The effect of correlation factor and path-loss exponent (PLE) on the optimal nodes’ power and location is investigated. The results show that optimizing relay location is more efficient than power allocation. Furthermore, a machine learning (ML) implementation of the proposed convex optimization-based algorithm is investigated to cop the computational burden. Specifically, the data set is obtained by using the proposed algorithm. Given the data set, the optimization algorithm can be translated into a regression problem, and feed-forward neural networks (FNNs) are then employed to solve this problem efficiently. The simulation results represented a compromise between accuracy and computation times for the ML-based joint PA-RL optimization.

Measurement and Prediction of Short-Range Path Loss between 27 and 40 GHz in University Campus Scenarios

In this paper, we present the results of short-range path loss measurement in the microwave and millimetre wave bands, at frequencies between 27 and 40 GHz, obtained in a campaign inside a university campus in Rio de Janeiro, Brazil. Existing empirical path loss prediction models, including the alpha-beta-gamma (ABG) model and the close-in free space reference distance with frequency-dependent path loss exponent (CIF) model, are tested against the measured data, and an improved prediction method that includes the path loss dependence on the height difference between transmitter and receiver is proposed. The main contribution of this paper is the use of the Fuzzy technique to perform path loss predictions for short links in the millimetre wave range, from 27 to 40 GHz, providing lower errors when compared to the traditional ABG and CIF models. However, it should be noted that the Fuzzy technique uses a set of equations to perform the prediction and the attenuation coefficient is not explicit as in the classical models. Also, a non-negligible correlation between the difference in height between transmitter and receiver positions and the path loss in such short links (i.e., the path inclination) has been observed and requires further investigation. If confirmed, it could provide an additional parameter to improve the accuracy of the traditional ABG model.

Adaptive Mini-Batch Gradient-Ascent-Based Localization for Indoor IoT Networks Under Rayleigh Fading Conditions

Location estimation in an indoor Internet-of-Things (IoT) environment is a challenging task due to multipath signals and obstacles that cause shadowing and fading effects, and change the received signal power considerably. Most of the existing path-loss-based localization methods assume only a lognormal shadowing model and ignore small scale fading effects. This article considers a generic combined lognormal shadowing and Rayleigh fading model for efficient localization of smart devices in an indoor IoT environment. In particular, the maximum likelihood estimate of the location and path-loss exponent (PLE), and Cramer-Rao lower bound (CRLB) are derived. The localization parameters are estimated using a novel adaptive mini-batch gradient ascent method that maximizes the log-likelihood function with an appropriate batch size based on the convergence factor. Hence, the proposed method addresses the challenge of an arbitrary selection of a fixed batch size for a gradient ascent method by utilizing this convergence factor. Performance evaluation by a simulation study and real experiments from an indoor IoT testbed provide a more accurate joint estimation of model parameters and smart device localization.

Optimizing the Number of Fog Nodes for Finite Fog Radio Access Networks under Multi-Slope Path Loss Model

Fog Radio Access Network (F-RAN) is a promising technology to address the bandwidth bottlenecks and network latency problems, by providing cloud-like services to the end nodes (ENs) at the edge of the network. The network latency can further be decreased by minimizing the transmission delay, which can be achieved by optimizing the number of Fog Nodes (FNs). In this context, we propose a stochastic geometry model to optimize the number of FNs in a finite F-RAN by exploiting the multi-slope path loss model (MS-PLM), which can more precisely characterize the path loss dependency on the propagation environment. The proposed approach shows that the optimum probability of being a FN is determined by the real root of a polynomial equation of a degree determined by the far-field path loss exponent (PLE) of the MS-PLM. The results analyze the impact of the path loss parameters and the number of deployed nodes on the optimum number of FNs. The results show that the optimum number of FNs is less than 7% of the total number of deployed nodes for all the considered scenarios. It also shows that optimizing the number of FNs achieves a significant reduction in the average transmission delay over the unoptimized scenarios.