Modèles de propagation pour les systèmes radio-mobiles

International audienceLa connaissance du canal de propagation est déterminante tout au long de la vie d'un système de communication. En phase de conception, les caractéristique du canal de propagation ainsi que les modèles statistiques orientent la définition de l'interface radio. En phase de déploiement, les modèles semi-déterministes prennent le relais pour l'organisation des réseaux opérationnels. Cet exposé, sans la prétention d'être exhaustif, a pour but d'introduire les principaux concepts utilisés en modélisation du canal de propagation bande étroite, large bande, ultra large bande et MIMO. Indissociable du processus de modélisation, les bases de données géographique et les technique de caractérisation du canal de propagation sont également évoquées

Frequency dependence of the UWB indoor propagation channel

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Typical MIMO propagation channels in urban macrocells at 2GHz

International audienceA directional wideband measurement campaign was performed in urban macrocells at 2 GHz using a channel sounder and a 8-sensor linear antenna array at the base station. Directions of arrival at the Base Station (BS) were estimated by beamforming using the antenna array. Directions of arrival at the Mobile Station (MS) were estimated by beamforming using parts of the measurement route. Global parameters (delay spread, azimuth spread at BS, maximum factor and street canyon factor) were processed from the Azimuth-Delay Power Profiles (ADPP) at BS and MS. In this paper, we compare the statistics of these four parameters with the statistics of those simulated by the 3GPP-SCM system-level model and the statistics of those reported in the literature. We find an acceptable agreement between our measurements and the SCM model except for the delay spread and the street canyon factor. The azimuth spread at BS mean Value (9.5°) and delay spread mean value (0.250 μs) are also in accordance with values reported in other references. Azimuth spreads are ranged from 7° to 11°, and delay spreads are ranged from 0.1 μs to 1 μs. From a statistical analysis of global parameters, we show that most of the measured propagation Channels can be classified in three main categories: low spatial diversity at MS and BS, high spatial diversity at MS and BS, low spatial diversity at BS and high spatial diversity at MS

Directional propagation channel estimation and analysis in urban environment with panoramic photography

International audienceThis article aims to provide readers with a physical understanding of the propagation channel that is complementary to mathematical channel modeling. It presents an analysis of the directional propagation channel based on radiophotos. Radiophotos are graphical objects where directions of arrival are superimposed on three-dimensional (3D) panoramic photographs.The interaction between electro magnetic waves and the environment is immediately identified with these representations. This paper focuses on the direction of arrival at mobile in an urban macrocell environment. The first radiophoto collection illustrates the major propagation phenomena such as reflection, diffraction, or street canyoning. The second collection illustrates typical propagation channel profiles that are classified according to delay, azimuth, and elevation spread values. The paper also describes an original panorama-based method for estimating noise level in the azimuth–elevation domain

Model for energy efficiency in radio over fiber distributed indoor antenna Wi-Fi network

International audienceDistributed antenna systems (DAS) are known to improve coverage and performance of wireless communications in indoor environments.In this paper, the power consumption and energy efficiency of a DAS using radio over fiber (RoF) are evaluated and compared with those in a centralized antenna system. The instantaneous power consumption curves of a Wi-Fi access point and dongle combination are physically measured for different transmission configurations, yielding a distance-dependent energy efficiency model. In a second step, computer simulations show that a distributed system with four antennas is 3.8 times more energy-efficient than a centralized antenna system, while the total radiated power is divided by a factor of two

Measurements clustering for robustness improvement of indoor WLAN propagation models

International audienceFor indoor Wireless Local Area Networks (WLANs) planning, an accurate propagation modelling is required. Semi-empirical models represent an efficient approach to the indoor channel coverage prediction. Their parameters are estimated from measurement results. In the case called ill-conditioned, the Least Square (LS) regression leads to a bad estimation of the model parameters and thus to numerical instability. In this paper, we present an approach based on the K-means clustering method which allows us to increase the estimation stability. Clustering is used to select tuning points for having a robust estimation

Effect of propagation phenomena on MIMO capacity of wireless systems between 3 and 10GHz

International audience— Multiple Input Multiple Output (MIMO) Antenna systems promise high spectral efficiency [1] over multipath channels. But accurate wideband MIMO channels models are required to optimize these new radio access schemes. This paper focuses on the MIMO channel capacity versus different propagation channel parameters such as frequency or antenna type. This study is based on both experimental and simulated results in a residential environment. The simulations have been computed with a full 3D ray tracing tool while measurements have been performed with a UWB MIMO channel sounder

Measurements and calibration method for WLAN indoor path loss modelling

International audienceFor indoor Wireless LAN systems planning, an accurate propagation modelling is required. Semi-empirical models represent an efficient approach to the coverage prediction. Based on measurement results, the model parameters are derived. In this paper we present the influence of the measurement point choice on the accuracy of the parameters estimation and thus on the model robustness

Utilisation des photos panoramiques pour la compréhension des phénomènes physiques du canal de propagation

International audienceCet article décrit une méthode du canal de propagation. Les directions d'arrivée sont juxtaposées sur des photos panoramiques 3D. L'ensemble appelé radiophoto permet la corrélation entre la mesure du canal et l'environnement. Les phénomènes physiques tels que la réflexion ou la dffraction sont facilement identifiés