Yannis Pousset

Outdoor and indoor channel characterization by a 3D simulation software

This paper presents a 3D simulation software of radiowave propagation for mobile systems in outdoor and indoor environments. The software allows us to predict the coverage zone of a base station and the behaviour of the transmission channel. After a brief recall of the radio channel characteristics for narrowband and wideband signals, the theoretical basis of our model and applications are described. Different results provided by our software are proposed : the evolution of the received power on a mobile route, the delay spread and the correlation bandwidth. To evaluate the capability of our software for the prediction of the previous parameters, measurements in outdoor and indoor environments are considered as a reference.

Radio Wave Propagation in Arched Cross Section Tunnels – Simulations and Measurements

For several years, wireless communication systems have been developed for train to infrastructure communication needs related to railway or mass transit applications. The systems should be able to operate in specific environments, such as tunnels. In this context, specific radio planning tools have to be developed to optimize system deployment. Realistic tunnels geometries are generally of rectangular cross section or arch-shaped. Furthermore, they are mostly curved. In order to calculate electromagnetic wave propagation in such tunnels, specific models have to be developed. Several works have dealt with retransmission of GSM or UMTS. Few theoretical or experimental works have focused on 2.4 GHz or 5.8 GHz bands. In this paper, we propose an approach to model radio wave propagation in these frequency bands in straight arch-shaped tunnels using tessellation in multi-facets. The model is based on a Ray Tracing tool using the image method. The work reported in this paper shows the propagation loss variations according to the shape of tunnels. A parametric study on the facets size to model the cross section is conducted. The influence of tunnel dimensions and signal frequency is examined. Finally, some measurement results in a straight arch-shaped tunnel are presented and analyzed in terms of slow and fast fading.

Impacts of impulsive noise from partial discharges on wireless systems performance: application to MIMO precoders

To satisfy the smart grid electrical network, communication systems in high-voltage substations have to be installed in order to control equipments. Considering that those substations were not necessarily designed for adding communication networks, one of the most appropriate solutions is to use wireless sensor network (WSN). However, the high voltage transported through the station generates a strong and specific radio noise. In order to prepare for such a network, the electromagnetic environment has to be characterized and tests in laboratories have to be performed to estimate the communication performances. This paper presents a method for measuring the noise due to high voltage and more particularly the impulsive noise. In the laboratory, we generate the impulsive noise using two specimens, and we show that these laboratory measurements validate the field measurements of Pakala et al. For the two specimens, it aims to link the noise characteristics (magnitude and frequency) with the specimen parameters (power supply and geometric dimensions) to predict the environments where wireless communications can be troublesome. By using different sets of this measured noise, we show that the statistical model of Middleton Class A can be used to model the impulsive noise in high-voltage substations better than the Gaussian model. We consider a cooperative multiple-input-multiple-output (MIMO) system to achieve the wireless sensor communication. This system uses recent MIMO techniques based on precoding like max-dmin and P-OSM precoders. The MIMO precoder-based cooperative system is a potential candidate for energy saving in WSN since energy efficiency optimization is a very important critical issue. Since MIMO precoders are with Gaussian noise assumption, we evaluate the performance of several MIMO precoders in the presence of impulsive noise using estimated parameters from the measured noise.

On the Importance of the MIMO Channel Correlation in Underground Railway Tunnels

This paper deals with MIMO channel modeling according to the correlation level in underground railway tunnels for various antenna configurations for the transmitting and receiving arrays. MIMO channel matrices have been computed with a 3D ray-tracing based software at 2.4 GHz and 5.8 GHz in two different tunnel environments: 1) a 1-track empty tunnel with a square cross section, 2) a 1-track tunnel with a square cross section in which a train is parked between the transmitter and the receiver. In this paper, two different strategies are investigated to model the MIMO channel using the Kronecker and the Weichselberger correlation based channel models. The first one is to model the MIMO channel using a single model over the total tunnel length. The second one takes into account the correlation at the receiving side according to the transmitter-receiver distance. In the latter solution, it is possible to isolate specific areas in the tunnel with specific correlation properties and model them in an independent way to take them into account in a system simulation. In this paper, these two modeling strategies are compared in terms of channel capacity.

Impact of realistic MIMO physical layer on video transmission over mobile Ad Hoc network

In this paper we investigate the impact of a realistic physical layer on the H.264/AVC video transmission over Ad Hoc networks in urban environment. We propose a realistic Multiple Input Multiple Output (MIMO) physical layer which combines a determinist propagation model and a fine-grained model of wireless transmission errors. The determinist propagation model takes into account all the environmental characteristics (geometric and electric) and provides all the information of the multi-path channel (received power, complex impulse response). The wireless transmission errors model is based on a BER computation. The BER is calculated according to 802.11n standard to evaluate MIMO wireless links and, then, is compared to both SISO configuration and an existing wireless errors model using empirical propagation models. In the case of a SISO configuration, the BER is computed according to 802.11a standard. The simulation results show clearly a significant difference in term of QoS for the video transmission using realistic and empirical physical layer. In addition, the MIMO system, compared to a SISO one, improves the quality of links in the network and, thus, provides a better QoS for video transmission over Ad Hoc networks.

A solution to efficient power allocation for H.264/SVC video transmission over a realistic MIMO channel using precoder designs

In this paper we propose a novel scheme for real time SVC-based video transmission over MIMO channels in the context of Joint Source Channel Coding (JSCC). This scheme compares the transmission of the H.264/SVC video over four precoder solutions, namely Max-SNR, WF, QoS and E-dmin. We exploit the high flexibility of the QoS precoder to minimize the total distortion of the received video. The proposed adaptive QoS precoder takes into account the scalability of the H.264/SVC standard jointly with the instantaneous MIMO channel statue. Finally, the proposed scheme is evaluated over both statistical and time Optimal power allocation varying realistic MIMO channels. This study provides the performance of these four precoder designs in term of BER, ML decoder complexity and the quality of the received video. We show that the precoder solutions providing the best BER MIMO channels performance are not usually the most appropriate for real time video transmission. However, the adaptive QoS precoder which uses three configurations, by considering both the importance of the video bit-QoS precoder stream and the channel statue, provides the best Rate-Distortion performance regardless the channel conditions. We assess the accuracy of these four precoder solutions against channel estimation errors over time varying realistic MIMO channel. The results shows that the adaptive QoS precoder remains robust against channel estimation errors even at high mobility speed.

Ultra-Wideband Indoor Channel Modelling Using Ray-Tracing Software for through-the-Wall Imaging Radar

This paper presents a new software for design of through-the-wall imaging radars. The first part describes the evolution of a ray tracing simulator, originally designed for propagation of narrowband signals, and then for ultra-wideband signals. This simulator allows to obtain temporal channel response to a wide-band emitter (3 GHz to 10 GHz). An experimental method is also described to identify the propagation paths. Simulation results are compared to propagation experiments under the same conditions. Different configurations are tested and then discussed. Finally, a configuration of through-the-wall imaging radar is proposed, with different antennas patterns and different targets. Simulated images will be helpful for understanding the experiment obtained images.

Optimal resource allocation for Medium Grain Scalable video transmission over MIMO channels

In this paper we investigate an optimal solution for adaptive H.264/SVC video transmission over Multiple-Input Multiple-Output (MIMO) channels. We first write the end-to-end distortion of the H.264/SVC video transmission over a diagonal MIMO channel. The total distortion is expressed following three physical layer parameters: power allocation, modulation spectral efficiency and Error Code Correction (ECC) code rate. Minimizing the total distortion is considered as an optimization problem containing both discrete and continuous variables. We use the Lagrangian method associated with Karush-Kuhn and Tucker conditions to find out the optimal continuous physical layer parameters. Concerting the discrete modulation spectral efficiency and ECC code rate, we exploit information of the MIMO system to remove all suboptimal configurations. Therefore, the optimal power allocation is computed only for a reduced number of discrete configurations. The performance of the proposed solution is evaluated over both statistical and realistic MIMO channels. Results show that the proposed solution performs an optimal resource allocation to achieve the best QoS regardless the channel conditions.

Law recognitions by information criteria for the statistical modeling of small scale fading of the radio mobile channel

Information criteria based methods are proposed to select the best probability law to model the distribution of samples resulting from the small-scale fading of the propagation channel. The first is based on the estimation of an optimal histogram approximating the probability density function. The second one employs the direct use of an information criterion. Indeed, the modelling of the radio mobile channel small-scale fading is crucial in digital communications. It is the reason why several propagation models have been implemented to take into account the electromagnetic phenomena inherent in radio wave channels. Amongst these models is the family of statistical distributions which is rapid in computation time. In the context of this study our concern is to find, among different probability laws, the one which best coincides with radio channel behaviour. The experimental results show that the proposed methods are better than those methods already employed, such as the classical Kolmogorov-Smirnov test using cumulative distribution functions, or methods using different estimators of probability density functions, like the kernel density estimator and the Gaussian mixture model. Results are provided in supervised and unsupervised contexts. Highlights? Accurate results in supervised and unsupervised law recognition from samples. ? Histogram-based method using Information criterion in supervised case. ? Information criterion based method in unsupervised case. ? Comparison with other non-parametric and parametric methods. ? Samples with ground truth and simulated from LOS and NLOS communications.

Realistic SISO and MIMO physical layer implemented in two routing protocols for vehicular ad hoc network

In the most of ad hoc network simulators, the physical layer is considered with a simple approach. Moreover, the information routing is realized in order to only minimize the number of hops or the delay. In this paper, the authors propose two contributions: the first one consists in considering a 3D propagation model taking into account the characteristics of the propagation environment for SISO and MIMO physical layers; the second one allows to introduce the BER as a metric of quality of the radio link used in two routing protocols. The impact of these two contributions is evaluated in two environments.