The objective of this paper is to study the influence of the direction of polarization at the transmitter site on the characteristics of the propagation channel in a road tunnel, either empty or in presence of vehicles. The transmitting frequency being on the order of 1 GHz, the tunnel behaves as an oversized waveguide and a simulation based on ray propagation is well suited. To take vehicles into account, the ray-based software models vehicles as parallelepiped considering full polarimetric wave interaction. In the examples described in this paper, the polarization at the transmitter is either vertical, horizontal or making an angle of 45°, referred to the horizontal axis. This last orientation that is often practically encountered in mobile communication systems has, to our knowledge, not yet been studied for a road tunnel which strongly differs from urban or suburban areas due to its guiding effect. Path loss, cross-polarization discrimination factor and characteristics of the polarization ellipse at the receiving point are compared for different configurations.

The fading process in vehicular communications is inherently non-stationary. In this paper, vehicle-to-infrastructure (V2I) radio channel measurements are performed inside a tunnel for low and medium traffic conditions to estimate the stationarity time, in addition to the time-varying RMS delay and Doppler spreads. Furthermore, we show the good fit of the spreads to a lognormal distribution, as well as for the Rician K-factor of the fading amplitude. From our analysis we conclude that the traffic density has an impact on the large-scale parameters as it increases delay and Doppler spreads, while reducing the correlation between them as well as the average K-factor. Larger traffic densities may be required to impact the stationarity time.

Power line communication is envisaged for the future more electric aircraft and the scenario studied in this work deals with the cabin lighting system, since its tree‐shaped architecture is sufficiently complicated to be representative of many other aircraft harness configurations. The statistical characteristics of the propagation channels are deduced from the measurements made on a representative test bench, the experimental values of the insertion gain being also compared with those obtained from a theoretical model based on the multiconductor transmission line theory. Field‐programmable gate array‐based modems have been designed and the performance of links are described and compared with predicted values deduced from a software tool simulating the link.

Theoretical and experimental approaches of the propagation in tunnels have been widely described in the literature, mainly focusing on the possibility of using multiple-input multiple-output (MIMO) transmission schemes, despite the small angular spread both at the transmitting and at the receiving site. Nevertheless, all these studies assume that the fixed base station is situated inside the tunnel. The objective of this paper is to generalize this case by considering the excitation of a tunnel by an outside antenna in order to know if, inside the tunnel, the diversity remains rich enough to get profit from MIMO techniques. The modal theory of the electromagnetic wave propagation will be used for interpreting the variation of path loss, correlation between array elements and capacity, as a function of the offset angle characterizing the direction of the fixed antenna array referred to the tunnel axis.

To limit the electromagnetic interference due to in-house PLC communication, standards on the emission levels of mains cables are now under elaboration. However, another additional aspect, not yet taken into account, deals with the possibility of exploiting the compromising radiated field to extract some information on the transmitted data. This problem of eavesdropping is known in the Electromagnetic Compatibility community, under the code name Tempest. The compromising propagation channel thus corresponds to the transmission by a modem between two wires of the power line and a reception on a loop antenna placed in adjacent rooms, apartments or houses. To evaluate this risk, a number of configurations are studied to determine the statistical properties of this channel. The influence of either the distance between the transmitting modem and the receiving loop, or of the walls between them, is investigated.

Polarization diversity has already been considered for implementing a MIMO link in an indoor environment. However, the propagation characteristics play a leading role in the improvement of the channel performance. The objective of this paper is thus to study the possible application of this kind of diversity in a road or railway tunnel. Extensive measurement campaigns have been carried out in a straight arched tunnel and in a frequency band extending from 2.8 to 5 GHz. From the transfer functions between horizontally or vertically polarized elements of the transmitting and receiving virtual arrays, (4,4) MIMO matrices have been deduced. Different linear array architectures were studied, considering or not different polarizations within each array. Channel capacity was calculated assuming either a constant signal to noise ratio (SNR), whatever the array architecture, or a fixed transmitted power. Interpretation of the results is based on the correlation between elements and also on the variation of the SNR in the case of a fixed transmitted power

This paper analyses the space-time behavior of the propagation channel in macrocell Outdoor-to-Indoor (021) environment at 3.6 GHz. The study is based on a SIMO (Single Input Multiple Out) measurement campaign performed on the campus of the Technical University of Lille, France. The measurement equipment included a channel sounder and a 12*12 virtual antenna array at the mobile station (MS). One of the main drawbacks of virtual array is the delay shift and phase drift occurring during the measurement when there is no synchronization between the transmitter and the receiver. The paper thus first focuses on the correction method which has been developed to cope with this problem. Delay spread (DS) as well as azimuth spread at MS (MS-AS) were deduced from the Azimuth-Delay-Power Profiles and the results are detailed in the second part of this paper. The mean AS value is 66deg and the mean DS value varies from 75 ns to 160 ns depending on the line of sight conditions between the MS inside the building and the outdoor base station. Regarding the AS statistics, an acceptable agreement between our measurements and values reported in the literature was found.

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.

Extensive measurements have been carried out in a straight road tunnel to study co-polar and cross-polar field behaviour versus frequency and antenna positions. The tunnel has approximately a semi-circular shape cross section that is quite usual for road and railway tunnels. Since MIMO techniques can be used for improving communication performances, even in tunnels, polarization diversity must be carefully studied for optimizing the antenna array configuration.

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.

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

SCOPUS: cp.p

The purpose of this paper is to examine the possibilities of increasing the channel capacity in tunnels, and particularly in railway tunnels, due to the use of multiple-input-multiple-output techniques. Many measurement campaigns have been carried out, considering the complicated geometric structure of these tunnels. We determine the channel characteristics by making a statistical analysis of correlation matrices between antennas and singular values of the channel transfer matrix. A comparison between the theoretical and experimental results is also presented. A stochastic channel model is then proposed and validated.

Both a theoretical approach and measurements of channel characteristics have been carried out to determine the maximum capacity which can be expected when MIMO techniques are implemented in tunnels, and especially in subway tunnels. Emphasis is given to the influence of the position of the antennas inside the transmitting and receiving arrays on the correlation between paths and on the singular values of the transfer matrix. The channel capacity is given for various geometrical configurations and compared with the case of i.i.d. Rayleigh channels.

Extensive measurements have been carried out in Paris subway tunnels to determine the channel characteristics and to deduce the available channel capacity of a multiple input multiple output (MIMO) transmission system. An analysis of the power correlation coefficients of the antennas on the train and on the platform is also performed to optimize the position of the antennas.

Abstract In this paper, we investigate how to increase the capacity of GSM (Global System for Mobile communications) radio interfaces in subway tunnel environments by means of antenna arrays and Space–Time (ST) receivers. We address the modeling, both theoretically and experimentally, of the multiple‐antenna wireless channels encountered in subway tunnels. We demonstrate that propagation is conveniently modeled by a flat‐fading channel, but there exist strong spatial correlations among channel components that decrease capacity and affect receivers' performance. Different space–time GSM receiving strategies have also been investigated. We first consider ST equalization techniques that only account for the noise and the controlled Intersymbol Interference (ISI) introduced by the modulation format employed in GSM. Then, we analyze the performance of receivers that incorporate ST coding capabilities and show the superior performance of iterative MAP (Maximum a Posteriori) receivers that interchange soft information among the equalizer and the ST decoder. All receivers are evaluated with experimental channels measured in the subway of Paris. Copyright © 2002 John Wiley & Sons, Ltd.

After a brief description of the theoretical approach to compute the field radiated by a leaky coaxial cable, examples are given to point out the influence of the tunnel walls on the electric field variation along the cable. The time domain response is then described together with experimental results.>