Experimental investigation of V2I radio channel in an arched tunnel

This paper describes the results of the experimental radio channel sounding campaign performed in an arched road tunnel in Le Havre, France. The co-polar and cross-polar channels measurements are carried out in the closed side lane, while the lane along the center of the tunnel is open to traffic. We investigate the channel characteristics in terms of: path loss, fading distribution, polarization power ratios and delay spread. All these parameters are essential for the deployment of vehicular communication systems inside tunnels. Our results indicate that, while the H-polar channel gain attenuates slower than the V-polar channel due to the geometry of the tunnel, the mean delay spread of the H-polar channel is larger than that of the V-polar channel

Influence of polarization on keyhole probability on a MIMO-OFDM train-to-wayside system on tunnels

This paper presents a deep insight on a real implementation of a train-to-wayside broadband radio on subway tunnels that makes use of a 2x2 MIMO-OFDM setup. A keyhole is a phenomenon that usually happens in tunnels and that seriously degrades channel?s capacity, even if both transmitter and receiver antennas are uncorrelated. The main purpose of this paper is to study in detail the influence of the polarization in the probability of having a keyhole on a MIMOOFDM train-to-wayside communication system on a tunnel. MIMO keyholes are studied in four different polarization setups, six different tunnels cross-sections and, finally, capacity results are provided

Multiple element antenna placement and structure studies in subway environments

Public subway transport networks require reliable high data reate wireless communication systems. One way to increase the maximum theoretical capacity in a certain environment is to apply the known MIMO techniques in order to maximize the presence of orthogonal sub-channels in a certain radio-channel. In this work the authors present a method to assess the impact of the position inside the tunnel and the diversity configuration of the antennas of the considered MIMO system on the maximum theoretical capacity of the radio-channel inside subway tunnels.Peer ReviewedPostprint (published version

MIMO channel measurement campaign in subway tunnels

Abstract—The recent construction of the new L9 subway line in Barcelona, Spain has provided the opportunity to study the impact of different antenna configurations on the maximum channel capacity inside subway tunnels. In this work the authors present the design tradeoffs inside different kind of tunnels in terms of antenna spacing and applied diversity technique for a 2x2 MIMO system at C-Band. These design tradeoffs are the conclusion of the measurement campaign carried out during last year at L9 subway tunnels.Peer ReviewedPostprint (published version

Measurements of a MIMO train-to-wayside communication system on tunnels

This paper presents a deep insight on a real implementation of a train-to-wayside radio on subway tunnels that makes use of a 2x2 MIMO-OFDM setup. The following parameters on the performance of such a system are investigated: polarization diversity, antenna separation, tunnel cross-section influence and MIMO capacity. Moreover, two different channel matrices have been calculated, assuming uniform power allocation and performing the waterfilling algorithm. Finally, the purpose of this paper is to evaluate the feasibility of a real MIMO-based train-to-wayside broadband radio. Measurements were carried out on Line 3 of Metro de Madrid, Spain

Millimeter-Wave Massive MU-MIMO Performance Analysis for Private Underground Mine Communications

In this article, a performance analysis of millimeter wave (mmWave) massive multiuser multiple-input and multiple-output (MU-MIMO) channel within an underground mine is performed. The analysis is based on channel measurements conducted at 28 GHz using a base station of 64 virtual antenna elements serving multiple users. Channel characteristics such as large-scale path loss, time dispersion, coherence bandwidth and sum-rate capacity are reported and evaluated. The results indicate that multislope path loss model is better suited for precise prediction of path loss across various propagation segments within the mining gallery. The time dispersion analysis reveals that the underground mine channel does not cause significant time dispersion, as 90% of the root-mean-square (rms) delay spreads are below 4 ns. In addition, it was found that the rms delay spread is not dependent on the propagation distance. The study on sum-rate capacity highlights the potential of employing massive MIMO technology to improve the channel’s spectral efficiency. The analysis reveals that the capacity, with eight active users, can reach up to 33.54 bit/s/Hz. The outcomes of this article offer valuable insights into the propagation properties of underground mine environment, which is characterized by rich-scattering and irregular topology

Experimental characterization of non-stationary V2I radio channel in tunnels

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

Experimental study on the impact of antenna characteristics on non-stationary V2I channel parameters in tunnels

This paper analyses the experimentally-assessed dual-polarized (DP) mobile channel in a tunnel environment at 1.35 GHz under traffic conditions. We investigate the impact of antenna polarization and radiation pattern on the non-stationary vehicle-to-infrastructure (V2I) channel. Basic channel evaluation metrics are examined including path gain, co-polarization ratio (CPR), and cross-polarization discrimination (XPD). In addition, the stationarity region is estimated using the channel correlation function approach, and used to calculate the time-varying delay and Doppler power profiles. Statistical models are presented for parameters like CPR, XPD, RMS delay and Doppler spreads, where the lognormal distribution provides the best fit. The polarization and the opening angle of the antennas into the propagation channel are found to strongly influence the observed non-stationarity of the channel. They impact the degree of multipath richness that is captured, thus providing different path gain, delay and Doppler spreads. Based on our analysis, the directional antenna with vertical polarization provides the longest stationarity time of 400 ms at 90 km/h, as well as the highest path gain and lowest dispersion. Furthermore, the DP channel capacity is calculated and its dependence on different normalization approaches is investigated. We propose a more accurate normalization for the DP channels that takes the conservation of energy into account. Moreover, the subchannels correlation coefficients are determined. While the condition number is found to be low on average, the correlation results show high correlation among the DP subchannels. As conclusion, we show how the CPR and XPD play the main role in providing multiplexing gain for DP tunnel channels

Channel Measurements and Models for High-Speed Train Wireless Communication Systems in Tunnel Scenarios: A Survey

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The rapid developments of high-speed trains (HSTs) introduce new challenges to HST wireless communication systems. Realistic HST channel models play a critical role in designing and evaluating HST communication systems. Due to the length limitation, bounding of tunnel itself, and waveguide effect, channel characteristics in tunnel scenarios are very different from those in other HST scenarios. Therefore, accurate tunnel channel models considering both large-scale and small-scale fading characteristics are essential for HST communication systems. Moreover, certain characteristics of tunnel channels have not been investigated sufficiently. This article provides a comprehensive review of the measurement campaigns in tunnels and presents some tunnel channel models using various modeling methods. Finally, future directions in HST tunnel channel measurements and modeling are discussed