Channel Modeling

In the advent of becoming reality, the era of autonomous vehicles is closer than ever, and with it, the need for faster and reliable wireless connections. The propagation channel determines the performance limits of wireless communications, and with the aid of empirical measurements, channel modeling is the best approach to predict and recreate how signal propagation conditions may perform. To this end, many different approaches and techniques have been implemented, from specific applications to general models, considering the characteristics of the environment (geometry-based or non-geometry-based) as well as seeking high performance algorithms in order to achieve good balance between accuracy and computational cost. This paper provides an updated overview of propagation channel models for vehicular communications, beginning with some specific propagation characteristics of these complex heterogeneous environments in terms of diverse communication scenarios, different combinations of link types, antenna placement/diversity, potentially high Doppler shifts, or non-stationarity, among others. The presented channel models are classified in four categories: empirical, non-geometry-based stochastic, geometry-based stochastic, and deterministic models, following the classical approach. The features and key concepts of the different vehicular communications channel models are presented, from sub 6 GHz to millimeter wave (mmWave) frequency bands. The advantages and disadvantages of the main works in the area are discussed and compared in a comprehensive way, outlining their contributions. Finally, future critical challenges and research directions for modeling reliable vehicular communications are introduced, such as the effects of vegetation, pedestrians, common scatterers, micro-mobility or spherical wavefront, which in the context of the near future are presented as research opportunities. INDEX TERMS Vehicular communications, channel modeling, propagation, mmWave.

Channel sounding of dense or complex environments, such as industrial or factory spaces, is an important consideration when increasing the deployment of current and next-generation wireless technologies. The deployment of machine-to-machine or vehicle-to-vehicle communications is of particular interest in the factory space as the dense environment provides a challenging test case. Here, we present results from a mobile channel sounder operating near the ISM (industrial, scientific, and medical) radio bands at 2.245 GHz and 5.400 GHz within a large factory space. We consider the possibility of both fast and slow fading effects due to our mobile receiver cart and due to other moving equipment in the space. Of critical importance to the validity of these measurements is the synchronization of the tether-less channel sounder using rubidium (Rb) clocks. The root mean squared (RMS) delay spread, Doppler spread, and fading results are presented for various experimental configurations, including different transmitter antenna locations, straight-line receiver cart paths, and stationary measurements collected in the presence of moving equipment.

Underwater Acoustic (UWA) networks are vital for remote sensing and ocean exploration but face inherent challenges such as limited bandwidth, long propagation delays, and highly dynamic channels. These constraints hinder realtime communication and degrade overall system performance. To address these challenges, this paper proposes a bilevel Multi-Armed Bandit (MAB) framework. At the fast inner level, a Contextual Delayed MAB (CD-MAB) jointly optimizes adaptive modulation and transmission power based on both channel state feedback and its Age of Information (AoI), thereby maximizing throughput. At the slower outer level, a Feedback Scheduling MAB dynamically adjusts the channel-state feedback interval according to throughput dynamics: stable throughput allows longer update intervals, while throughput drops trigger more frequent updates. This adaptive mechanism reduces feedback overhead and enhances responsiveness to varying network conditions. The proposed bilevel framework is computationally efficient and wellsuited to resource-constrained UWA networks. Simulation results using the DESERT Underwater Network Simulator demonstrate throughput gains of up to 20.61% and energy savings of up to 36.60% compared with Deep Reinforcement Learning (DRL) baselines reported in the existing literature.

directeur de mémoire Génie électrique à l'École de technologie supérieure M. Jean-Marc Robert président du jury Génie électrique à l'École de technologie supérieure M. Michel Kadoch membre de jury Département de génie logiciel et des TI à l'École de technologie supérieure IL A FAIT L'OBJET D'UNE SOUTENANCE DEVANT JURY ET PUBLIC LE 07 DÉCEMBRE 2009 À L'ÉCOLE DE TECHNOLOGIE SUPÉRIEURE REMERCIEMENTS Je voudrais remercier: M. M. Jean-Marc Robert, d'avoir présidé le jury de mon mémoire, Michel Kadoch pour sa participation dans la commission de Texamination. Mes remerciements et reconnaissances vont particulièrement à mon directeur, M. Dziong Zbigniew, pour la proposition du sujet, pour son aide ainsi que pour ses critiques constructives. La question qui se pose constamment dans la communauté des chercheurs est l'intégration de la qualité de service dans le réseau Intemet. Plusieurs solutions ont été proposées à savoir la réservation dédiée de la largeur de bande, la différentiation de service, l'ingénierie du trafic, etc. Les réseaux dédiés de service sont appams récemment pour répondre aux limites d'Intemet. Ce sont des réseaux qu'on implante par-dessus Intemet, et donc utilisent Intemet comme réseau de transport, pour supporter des besoins spécifiques des applications en termes de qualité et de fiabilité de service. Nous nous sommes intéressés au problème de routage avec qualité de service dans les réseaux dédiés de service. Nous avons développé un routage préventif de détérioration de service (BProb) basé sur la mesure de la largeur de bande disponible. Celui-ci recherche le chemin qui minimise la probabilité que la largeur de bande disponible soit inférieure à la largeur de bande requise par la connexion. En plus de la moyenne, notre routage requiert la variance de la largeur de bande disponible afin de favoriser davantage les chemins les plus stables affectant ainsi le moins la perte de paquets, le délai et la gigue. Notre routage est soutenu par la surveillance des états des liens à travers la mesure continue de la largeur de bande disponible. Une analyse de la performance de Bprob a été faite comparativement à celle du routage qui choisit le chemin qui maximise la largeur de bande disponible (Bmax). Nous avons implémenté et simulé les deux routages avec l'outil NS2(Network Simulator version 2.29). Plusieurs simulations ont été menées avec différents scénarios de trafic paramétrés par la moyerme et la variance de la largeur de bande disponible. Nous avons constaté que le routage Bprob offre une performance meilleure sur le routage Bmax par rapport aux métriques de QoS.

Une des problematiques les plus importantes pour les reseaux locaux sans fil est l'acces et le partage du medium radio sans fil. Plusieurs protocoles MAC mono-canal ont ete proposes et abordent cette problematique avec des solutions interessantes, mais certains problemes majeurs lies a l'acces au canal (noeud cache, synchronisation, propagation des RDV) pour un contexte de transmission multi-saut, persistent encore et font toujours l'objet d'intenses etudes de la communaute scientifique, surtout lorsqu'il s'agit de reseaux de capteurs sans fil distribues sur des topologies etendues. Afin de trouver des solutions plus efficaces, certains travaux de recherches ont propose des protocoles MAC multi-canal, traitant souvent le cas ideal, ou tous les noeuds dans le reseau sont a portee les uns des autres, ou lorsque les emissions et receptions des trames de donnees sont precedees de trames des controles pour l'etablissement de rendez-vous (RDV) entre les noeuds ...

The error characteristics of a free-space optical (FSO) channel are significantly different from the fiber based optical links and thus require a deep physical understanding of the propagation channel. In particular different fog conditions greatly influence the optical transmissions and thus a channel model is required to estimate the detrimental fog effects. In this paper we shall present the probabilistic model for radiation fog from the measured data over a 80 m FSO link installed at Graz, Austria. The fog events are classified into thick fog, moderate fog, light fog and general fog based on the international code of visibility range. We applied some probability distribution functions (PDFs) such as Kumaraswamy, Johnson S B and Logistic distribution, to the actual measured optical attenuations. The performance of each distribution is evaluated by Q-Q and P-P plots. It is found that Kumaraswamy distribution is the best fit for general fog, while Logistic distribution is the optimum choice for thick fog. On the other hand, Johnson S B distribution best fits the moderate and light fog related measured attenuation data. The difference in these probabilistic models and the resultant variation in the received signal strength under different fog types needs to be considered in designing an efficient FSO system.

This paper investigates the influence of the inter carrier interference on a vehicle to infrastructure (V2X) communication system, which has been defined in the IEEE 802.lIp standard. The frequency shift due to high speed of cars destroys the orthogonality between subcarriers in OFDM signals and rises the inter-carrier interference (leI). The main contributions of this paper are proposed analytic formulas and simulation results of the signal to interference power ratio (SIR) by considering the statistical effects of leI and evaluation of symbol error rate (SER) for several types of fading and Doppler spread in time domain approach. The results show that for the Rayleigh fading model, SIR decreases when the maximum Doppler spread increases. On the other hand, in the Rician channel, SIR depends not only on maximum Doppler spread but also on the angle of arrival (AoA) and Rician factor of the LOS component. Moreover, the simulation result in terms of SER is obtained for different channel models. It shows an excellent agreement between the theoretical calculation of SIR and the simulation results of SER. Keyword-leI and SIR analysis for OFDM-based vehicle X system, V2X channel models.

The demands for higher throughput, data rate, low latency, and capacity in 5G communication systems prompt the use of millimeter-wave frequencies that range from 3–300 GHz with spatial multiplexing and beamforming. To get the maximum benefit from this technology, it’s important to study all the challenges of using mm-wave for 5G and beyond. One of the most important impacts is weather conditions such as humidity, temperature, dust, and sand storms. This study investigates the parameters of the channel model and its statistical behavior with the effect of dust and sand storms. The latter effects can be considered the main challenges these days, especially in middle-eastern countries. A 128 x 128 massive MIMO with URA (uniformly spaced rectangular antenna arrays) uniformly spaced has been considered in the simulation assessment with mm-wave channels operating at 28 GHz and 73GHz are examined by using NYUSIM (New York University Wireless Simulator) software. The simulation results show...

The wireless communications channel constitutes the basic physical link between the transmitter and the receiver antennas. Its modelling has been and continues to be a tantalizing issue, while being one of the most fundamental components based on which transmitters and receivers are designed and optimized. The ultimate performance limits of any communication system are determined by the channel and their operating environment like fading, multipath propagation, type of terrains, and mobility (Doppler shift). Realistic channel models are thus of utmost importance for system design and testing. In this paper an effort has been made to evaluate the performance of mobile wireless communication channel in terms of number of taps mobile Velocity and Doppler Spectrum.

The growing use of Unmanned Aerial Vehicles (UAVs) for various applications requires ubiquitous and reliable connectivity for safe control and data exchange between these devices and ground terminals. Depending on the application, UAV-mounted wireless equipment can either be an aerial user equipment (AUE) that co-exists with the terrestrial users, or it can be a part of wireless infrastructure providing a range of services to the ground users. For instance, AUE can be used for real-time search and rescue and/or video streaming (surveillance, broadcasting) and Aerial Base Station (ABS) can enhance coverage, capacity and energy efficiency of wireless networks. In both cases, UAV-based solutions are scalable, mobile, easy and fast to deploy. However, several technical challenges have to be addressed before such solutions will become widely used. In this work, we present a tutorial on wireless communication with UAVs, taking into account a wide range of potential applications. The main goal of this work is to provide a complete overview of the main scenarios (AUE and ABS), channel and performance models, compare them, and discuss open research points. This work is intended to serve as a tutorial for wireless communication with UAVs, which gives a comprehensive overview of the research done until now and depicts a comprehensive picture to foster new ideas and solutions while avoiding duplication of past work. We start by discussing the open challenges of wireless communication with UAVs. To give answers to the posed questions, we focus on the UAV communication basics, mainly providing the necessary channel modeling background and giving guidelines on how various channel models should be used. Next, theoretical, simulation-and measurement-based approaches, to address the key challenges for AUE usage, are presented. Moreover, in this work, we aim to provide a comprehensive overview on how UAV-mounted equipment can be used as a part of a communication network. Based on the theoretical analysis, we show how various network parameters (for example coverage area , power efficiency, or user localization error of ABSs) can be optimized.

Optical Wireless Communication (OWC) refers to transmission in unguided propagation media through the use of optical carriers, i.e., visible, Infrared (IR), and Ultraviolet (UV) bands. In this paper, we focus on indoor Visible Light Communication (VLC)-based Medical Body Sensor Networks (MBSNs) which allow the Light Emitting Diodes (LEDs) to communicate between on-body sensors/subdermal implants and on-body central hubs/monitoring devices while also serving as a luminaire. Since the Quality-of-Service (QoS) of the communication systems depends heavily on realistic channel modeling and characterization, this paper aims at presenting an up-to-date survey of works on channel modeling activities for MBSNs. The first part reviews existing IR-based MBSNs channel models based on which VLC channel models are derived. The second part of this review provides details on existing VLC-based MBSNs channel models according to the mobility of the MBSNs on the patient's body. We also present a realistic channel modeling approach called site-specific ray tracing that considers the skin tissue for the MBSNs channel modeling for realistic hospital scenarios. Channel modeling, medical body sensor networks (MBSNs), optical communication, transdermal communication (TC), visible light communication (VLC).

The demands for higher throughput, data rate, low latency, and capacity in 5G communication systems prompt the use of millimeter-wave frequencies that range from 3–300 GHz with spatial multiplexing and beamforming. To get the maximum benefit from this technology, it’s important to study all the challenges of using mm-wave for 5G and beyond. One of the most important impacts is weather conditions such as humidity, temperature, dust, and sand storms. This study investigates the parameters of the channel model and its statistical behavior with the effect of dust and sand storms. The latter effects can be considered the main challenges these days, especially in middle-eastern countries. A 128 x 128 massive MIMO with URA (uniformly spaced rectangular antenna arrays) uniformly spaced has been considered in the simulation assessment with mm-wave channels operating at 28 GHz and 73GHz are examined by using NYUSIM (New York University Wireless Simulator) software. The simulation results show...

L'optimisation d'un récepteur utilisant un décodage source-canal conjoint (DSCC) impliquant un code LDPC sera considérée pour les systèmes itératifs suivant : (a) récepteur source-canal conjoint optimal, (b) récepteurs compatibles avec des applications non conjointes, (c) le récepteur tandem optimal supposant une compression de source parfaite. Des résultats d'optimisation et de simulation seront fournis pour différents rendements et longueurs de mots de code.

__ In this paper we propose a new shadowed Rice model for land mobile satellite channels. In this model, the amplitude of the line-of-sight is characterized by the Nakagami distribution. The major advantage of the model is that it leads to closed-form and mathematically-tractable expressions for the fundamental channel statistics such as the envelope probability density function, moment generating function of the instantaneous power, and the level crossing rate. The model is very convenient for analytical and numerical performance prediction of complicated narrowband and wideband land mobile satellite systems, with different types of uncoded/coded modulations, with or without diversity. Comparison of the first-and the second-order statistics of the proposed model with different sets of published channel data demonstrates the flexibility of the new model in characterizing a variety of channel conditions and propagation mechanisms over satellite links. Interestingly, the proposed model provides a similar fit to the experimental data as the well-accepted Loo's model, but with significantly less computational burden.

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Channel modeling plays a vital role in wireless communication today. To meet the demand for an extensive high data rate, the only effective way is to shift from lower to higher carrier frequencies in the Terahertz (THz) band. Wireless data traffic has been growing exponentially in recent years, and this has also been accompanied by the increasing demand for speedy wireless communication networks. In particular, wireless data rates have been doubling every 18 months for the last three decades and are almost approaching the last capacity level of communication systems. Advanced physical layer solutions and, more importantly, new spectral bands will be required to support the high data rate for future wireless communications. Among others, the terahertz (0.3-3 THz) band is one of the key promising spectral bands to enable high data rate communications for fifth-generation (5G) and beyond. In general, the channel model is very essential in designing and simulating the realistic techniques for communication in THz band. The vital points for which channel modeling is deemed to be necessary are given as under:
1. To design devices, antennas, radio and signal processing elements, protocols, and networks according to system requirements.
2. To evaluate link- and network-level performance in realistic propagation conditions.
3. Helps in comparing different protocols for standardization.
After realizing the importance of channel modeling in wireless communication, it becomes evident that a lot of work needs to be done for the sake of ever-growing next-generation wireless networks. The study and research in this particular THz channel modeling will help uncover the critical areas in higher-order wireless communication networks.

Today's advanced simulators facilitate thorough studies on Vehicular Ad-hoc NETworks (VANETs). However the choice of the physical layer and the mobility models in such simulators is a crucial issue that greatly impacts the results. Realistic simulation of routing protocols in VANETs is still an open question. Indeed, only a few works address routing protocols comparison performed under realistic conditions. This paper compares common reactive, pro-active, hybrid and geographic routing protocols by using a simulation platform integrating a realistic physical layer and mobility models. It also presents and analyzes several reactive protocols enhancements propositions dedicated to the VANETs context such as multi-path routing, but also protocols tuning which allows it to adapt faster. They have all received a lot of attention and are typically proposed to increase the reliability of data transmission. This paper study the behavior of each protocol in different situations and analized their advantages and drawbacks. Results presented in this paper gives an important explanation on the contradictory results found in similar works. Finally, our realistic simulations show that reactive protocols are the best suited for VANETs, and more especially the DYMO protocol.

As compared to traditional terrestrial links, underwater channels suffer for the limited bandwidth and long propagation delays. To cope with these issues, transmissions should be reliable and the relevant parameters dynamically tunable based on the channel conditions. To this aim, availability of a realistic channel model for the specific physical settings considered is a key element. Accordingly, in this paper we derive an underwater acoustic channel model based on field test measurements carried out in the Tyrrhenian sea. Specifically two models are obtained, one based on a Markov channel modeling with multiple possible states and another based on Kalman filter design. We compare their accuracy in predicting channel status and show that, based on the specific channel setting and application scenario, different channel models can be chosen to identify a trade-off between good prediction accuracy and affordable complexity.

Unlike traditional terrestrial scenarios, communication channels in underwater environments face severe limitations in bandwidth and experience long propagation delay. In order to address these issues, reliable techniques capable to dynamically adapt transmission parameters to time-varying channel conditions are necessary. Actually, their effectiveness primarily relies on an accurate characterization of the underwater communication channels, which is often obtained through predictive models. In this paper, we compare the performance of different types of SNR-based predictive models (i.e., Markov models, Hidden Markov models) in terms of balance between accuracy and complexity. We also provide a Kalman filter-based prediction of SNR values and compare this prediction with the performance achieved with the Markov models above mentioned. The models we have considered to carry out the comparison analysis have been developed based on real shallow water traces taken over the Tyrrhenian Sea, Italy.

Underwater communications suffer from numerous challenges typically associated with relevant signal attenuation, long propagation delay, limited available bandwidth, and high error rates that severely affect underwater transmission performance. Therefore, it is crucial to apply adaptive or predictive techniques to ensure the best possible performance and guarantee reliability in underwater communication, especially in rapidly changing environments. Using adaptive (i.e., reactive) or predictive (i.e., proactive) methods, it is possible to avoid data retransmission, improve the lifetime of underwater nodes, reduce maintenance frequency and the necessary equipment replacement and recharge, and consequently optimize performance in general. In this regard, many works in the literature propose various adaptive or predictive techniques for UnderWater Acoustic (UWA) networks, which we critically classify and discuss in this qualitative survey.

Due to the recent surge in the proliferation of smart wireless devices that feature higher data speeds, there has been a rise in demand for faster indoor data communication services. Moreover, there is a sharp increase in the amount of mobile data being generated worldwide, and much of this data comes from residential wireless applications like high-definition TV, device-to-device communication, and high data rate indoor networks (i.e., local and cellular). These technologies need large capacity, high data rate indoor wireless networks with huge bandwidth. Consequently, a greater interest exists in implementing an effective and trustworthy indoor propagation model for next-generation wireless systems operating in the massively bandwidth-rich millimeter wave (mm-wave) frequency range. The analysis of mm-wave propagation characteristics in an indoor environment using the ray tracing approach is proposed in this paper. Propagation modeling for 60 GHz bands is included. The aspects of wideband propagation characteristics such as angular spread, path loss, delay spread, and power delay profile are modeled in this paper.  The position of transceivers, antenna effect, and attenuation, in the hallways, and stairwells will all be considered while determining the propagation parameters. This includes wave propagation characteristics like absorption, reflection, and diffraction by building structures and furniture. The specifications for propagation characteristics are included in the article for developing indoor local and cellular networks. In this paper, the IRT model has been tested at 60 GHz for potential mobile communication and is identified as the best method for predicting signal attenuation caused by objects, barriers, or humans within buildings in internal millimeter wave transmission.