Navarat Lertsirisopon

Wideband Polarimetric Directional Propagation Channel Analysis Inside an Arched Tunnel

A wideband directional measurement campaign was managed inside an arched highway tunnel to analyze the radio propagation channel inside such tunnel for future cellular systems in terms of coverage, delay spread and dominant scatterers. Measurements were performed in 3 rounds with different transmitter positions. Using a wideband channel sounder equipped with a cylindrical dual polarized array at the receiver, the spatio-temporal characteristics of the received propagation paths could be estimated by means of a super-resolution estimation algorithm. The extracted paths using this super-resolution algorithm constitute 88% of the total received power. It was also observed that the line-of-sight component (53%) plus single-bounce scattering (26%) comprise up to 79% of the total received power. In other words, more than 90% (i.e. 79% in 88%) of the extracted paths consists of the line-of-sight component and single-bounce scatterings. The strong contribution from single-bounce scattering paths causes the path gain exponent along the tunnel to be larger than -2 which is the value for free space. This validates that there is wave guiding effect in the tunnel and coverage is extended relative to open space. The rms delay spreads are generally less than 20 ns and increase when influenced by scattering objects such as jetfans. The dominant scatterers are identified and classified into 6 classes based on the structure of the tunnel and existing objects such as ground, wall, light-frame, ceiling, jetfan and cleaner-parking. It was observed that scattering from ground was dominant among all classified scatterers in all scenarios.

Analysis of DSRC Service Over-Reach inside an Arched Tunnel

In this paper, the prediction of received power in the out-of-zone of a dedicated short range communications (DSRC) system operating inside a typical arched highway tunnel is discussed. By conducting wideband directional channel sounding inside the tunnel, the gain, angle-of-arrival and delay of each propagation path are estimated by means of a multidimensional maximum likelihood estimation algorithm from the measured data. Using these estimated parameters and by employing simulations of application antennas according to the DSRC standard, the received power in the out-of-zone is predicted for 2 roadside unit (RSU) antenna positions. The dominant scatterers causing the over-reach of radiated power to the out-of- zone were identified and attributed to the ground and sidewalk. These scatterers can affect the received power level in the out- of-zone by as much as 10 dB. It can therefore be concluded that suppressing ground and sidewalk scatterings in the vicinity of RSU by installing composite pavement materials are needed to increase the electromagnetic absorption in order to guarantee DSRC services.

Wideband Directional Radio Propagation Channel Analysis Inside an Arched Tunnel

To analyze the radio propagation channel inside a tunnel, a wideband directional measurement campaign was managed inside an arched tunnel which was constructed to be used for a highway. Using a wideband channel sounder equipped with a cylindrical dual polarized array at the receiver (Rx), the spatio-temporal characteristics of the received propagation paths could be estimated by means of a super-resolution estimation algorithm. The dominant scatterers are classified into 5 classes based on the structure of the tunnel as follows: ceiling, light-frames, walls, sidewalk or ground. The power contribution and cross polarization ratio for different Rx positions along the tunnel are compared

Effects of Bragg Scattering on Ultra-Wideband Signal Transmission from Periodic Surfaces

In this paper, the effects of Bragg scattering on ultra-wideband (UWB) signal transmission from periodic surfaces are reported. First, the frequency dispersive property of Bragg scattering is theoretically and experimentally confirmed. Next, the transfer function of both specular path and Bragg scattering are extracted. Then direct sequence UWB (DS-UWB) transmission simulations are conducted by using a raised cosine pulse that occupied 3.1 to 10.6GHz and a Gaussian pulse that occupied 8.75 to 9.25GHz. Finally, the effects of Bragg scattering on UWB systems are discussed.

Tunnel Propagation Channel Characterization for DSRC Applications

The propagation channel characteristics of a transportation tunnel for DSRC applications is discussed. One problem in DSRC applications is that the received power in the adjacent (non-coverage) zone can be higher than the maximum allowed threshold. To identify its cause, a wideband directional channel sounding was conducted inside the tunnel. From the sounding data, the propagation path parameters are estimated by a multidimensional maximum likelihood estimation algorithm and scatterers are identified based on the angle-of-arrival and delay information. These propagation paths together with simulated DSRC application antennas are then used to predict the probability of the received power in the adjacent zone. The power contribution of the scatterers are calculated and the dominant scatterers are found to be from ground and sidewalk scatterers.

Directional Channel Characteristics from Microcell Measurement and Simulation

In this paper, the channel predicted by using a ray- tracing simulator is presented and compared to microcellular measurement results performed inside a university campus. For data processing, the conventional beamforming is utilized to compare the directional wideband channel properties of both simulation and measurement results. Ray-tracing algorithm can investigate most of the radio propagation mechanisms. However, there are some scattering effects that are not included. Therefore, the objective of this study is to analyze and compare directional wideband channel characteristics such as azimuth-delay spectrum and azimuth-coelevation spectrum from the ray-tracing results with measurements to gain insights on the significant propagation mechanisms in microcell scenarios.