Olivier Delangre

Modeling in-Vehicle Wideband Wireless Channels Using Reverberation Chamber Theory

In this paper, the wideband channel is studied inside a vehicle. Propagation inside a recent car (model bought in 2006) is investigated and the power delay profile is measured for three different scenarios. Two kinds of transmission bandwidths are studied, 200 MHz around 5 Ghz and an ultra-wideband bandwidth of 3 Ghz around 4.5 GHz. The ultra-wideband measurements allow to clearly identify the propagation mechanism in this kind of environment. For each scenario, an exponential model for the power delay profile is shown to be in good agreement. A theoretical model based on reverberation chamber theory is proposed. It allows to predict the rms delay spread inside the car. A comparison with measurements inside a reverberation chamber is presented.

Wideband Analysis of Coupled Reverberation Chambers for Testing MIMO Systems

In this paper, a wideband characterization of coupled reverberation chambers is presented. This testbed allows to model dense multipath environments and to control the channel by means of a waveguide connecting the two chambers. A wideband model is first proposed. This model emphasizes the presence of different independent paths between the emitter and the receiver. Some measurements of impulse response are then presented. Very high values of rms delay spread are obtained between the chambers leading to inadequacy with indoor environments for example. A modification of the testbed by means of absorbing materials is proposed. Measurements results are presented showing that the best position for placing absorbing materials is in the transmitter chamber. The values of rms delays spread obtained pave the way to a new testbed for MIMO systems

Reverberation Chamber Environment for Testing Communication Systems: Applications to OFDM and SC-FDE

The impulse response in a reverberation chamber is investigated from an experimental and theoretical point of view. A full description is thus proposed based on measurements and confirmed by means of theoretical insights. In particular, the K factor of each tap is emphasized. BER simulations for OFDM and single carrier frequency domain equalization (SC-FDE) systems are applied on this channel model and compared to the 802.11n channel model showing some differences mainly for the OFDM transmission.

Adaptable measurement testbed for wireless systems applied to mimo channel modeling

A new experimental way of testing MIMO systems is proposed by means of two reverberation chambers coupled through a waveguide. The modularity of this experimental setup is emphasized and some theoretical and experimental results are presented. The effect of the waveguide on the propagation channel is pointed out. I. INTRODUCTION MIMO systems have gained a lot of attention since they promise an increase of the capacity with a very high spectral efficiency. The knowledge of the propagation mechanisms is crucial in order to define reliable, precise and adaptive channel models. Theoretical researches have been carried out in order to obtain such a channel model (1). However, a model must be supported by measurements campaigns. Those measurements are highly environment dependent and it is difficult to reproduce or to control the environment. In this paper, a new measurement system is proposed which allows to control and to reproduce different specific environments. This measurement testbed is composed of two reverberation chambers coupled through a waveguide. First, the theoretical modeling of the chambers is presented. To model accurately the channel we have to deepen the understanding of the propagation in the waveguide. The basics of waveguide modal analysis are presented. Then, the power weight of each mode is computed. From this result, we are able to understand intu- itively the propagation mechanism in waveguide like systems and the notion of independent paths with different amount of power. To fulfill the understanding of the waveguide, the radiation of each mode in the receiving chamber is deduced. Some numerical results are provided. A channel model is then presented in order to take into account all the parameters of our system. Measurement results are finally provided, pointing out the ability to obtain different propagation conditions. A discussion about the benefits and the drawbacks of this system concludes the paper. II. THE COUPLED REVERBERATION CHAMBERS The proposed testbed is composed of two mode stirred reverberation chambers (MSRC) of about 16m 3 each. MSRC have first been developed for susceptibility testing of electronic devices. Since they allow to produce a dense and isotropic multipath environment, they are now also used for testing antenna characteristics (such as correlation between antennas, mutual coupling or embedded element pattern) and wireless communications systems (2), (3). By means of the movement of the mechanical stirrer, the boundary conditions are changed and a new distribution of the propagating plane waves in the chamber is obtained. The originality in this paper is the use of two chambers to model separate environments for the emitter and the receiver. Those chambers are coupled through a waveguide (cf. Fig. 1) whose transverse dimensions can be changed in order to modify the channel characteristics between the emitter and the receiver. The waveguide allows to obtain independent propagation paths, and to control the degrees of freedom of the channel.

Testing MIMO systems with coupled reverberation chambers: A wideband channel model

In this paper, a new testbed composed of two reverberation chambers coupled through a waveguide is presented. A new wideband channel model for this testbed is emphasized. The theory about the waveguide coupling the two chambers is first reminded leading to a full description of the channel model. This model includes all the characteristics of the environment like the possibility to reproduce the number of degrees of freedom in the channel and the correlation between antennas. Some simulation results are presented showing a good agreement with theoretical and measurements results.

Characterization of a confined environment based on acoustic and reverberation chamber theory. Comparison with the case of a car

The study of propagation inside confined environments leads to very specific results. Specular reflections are not dominant and the result is more comparable with diffuse scattering. Evaluating this channel can be done using acoustic theory. However, this theory is described by a parameter, eta whose physical meaning lacks of description. Reverberation chamber theory can therefore be applied to estimate for example the delay spread inside a confined environment. This theory also suffers of some drawbacks. The most important is that it is only valide for sufficiently high Q factor. A car is a classical confined environment. Therefore, measurements inside a car are presented showing some common characteristics with a reverberation chamber.