Tokio Taga

Time-Varying Path-Shadowing Model for Indoor Populated Environments

This paper presents a path-shadowing model for indoor populated environments that has been developed based on computer simulations. The propagation paths between the transmitting and receiving points in an empty rectangular space are determined using the ray-tracing method, in which moving quasi-human bodies that are modeled as cylinders with a finite height are generated in the space, and intersections of the paths with the bodies are counted. From the results, the shadowing probabilities, durations, and intervals are evaluated for each propagation path, and this shadowing process is characterized as a Markov process. This paper proposes a method that individually generates the shadowing effects on each propagation path. The measurement results of the path-shadowing characteristics using a 5.2-GHz high-resolution channel sounder are presented, and the validity of this model is confirmed. Similar measurement results using a photoelectric sensor are also presented to reinforce the channel-sounding measurement results.

Multipath propagation model for line-of-sight street microcells in urban area

This paper proposes a multipath propagation model for line-of-sight (LOS) street microcells with building roof base sites (BS) in urban areas, Multipath propagation characteristics are of great importance in evaluating the performance of digital systems and designing wireless links. Typical delay profiles are measured to clarify their statistical characteristics in LOS street microcells. The channel sounder used is a sliding correlator with 30-Mb/s PN code and a center frequency of 2.6 GHz. The measurements clarify the features of delay profile and mean RMS delay spread. The proposed delay profile model explains one plausible mechanism of multipath propagation. The delay profiles calculated using the model agreed well with the measured profiles. Furthermore, the factors influencing the RMSs delay spread are investigated, and the regression equation of medium RMS delay spread on a sidewalk is established. The proposed model can evaluate the transmission characteristics of wireless digital communication systems in multipath propagation environments.

Outdoor-to-indoor propagation modelling with the identification of path passing through wall openings

This paper proposes a new propagation model to accurately predict outdoor-to-indoor propagation loss. Account is taken of the structural openings along the paths; it is assumed that outdoor-to-indoor paths are possible only through wall openings such as doors and windows. Introducing the angle dependency of the losses with the paths that penetrate the indoor area makes it possible to accurately predict outdoor-to-indoor propagation loss. Measurements in a microcellular environment show that the proposed model can predict outdoor-to-indoor propagation loss more accurately than the COST231 model.

Mean Effective Gain of Mobile Antennas in Line-of-Sight Street Microcells With Low Base Station Antennas

A method for evaluating the mean effective gain (MEG) of mobile antennas in line-of-sight (LOS) street microcells with low base station antennas is investigated. The received power patterns of incident radio waves along typical streets measured in actual street microcells in urban areas of Tokyo are presented to clarify the proper distribution model for the incident radio waves. A two-dimensional statistical distribution model is proposed based on the measured received power patterns for the incident radio waves that follow a Gaussian distribution in the azimuth angle, but are concentrated in the horizontal plane in the elevation angle. The two-dimensional theoretical expression of the MEG that consists of the incident distribution model function and the radiation patterns in the horizontal plane of the mobile antennas is derived to evaluate easily the MEG. We show that the MEG values in street microcells are not defined as only one value and form the MEG pattern because the MEG values are changed by the relative direction of the radio waves arriving at the mobile station antennas. The measured and calculated MEG values (MEG patterns) of the whip antennas used in the experiments are in good agreement. The average error between the measured and calculated MEG values is within approximately 4.5 dB at maximum. The results show that the MEG degradation of the mobile station antennas due to the effect of the human body is properly evaluated by the proposed distribution model. The proposed statistical distribution model is valid and effective in both estimating the MEG values of mobile antennas and designing the LOS street microcell systems with low base station antennas.

Statistical scattering model in urban propagation environment

A statistical scattering model for mobile radio channels that has the following three features is proposed: 1) the effective scattering area (ESA) is expressed by an ellipse, the center of which is the mobile station (MS) location; 2) the major axis of the ellipse runs parallel along the street where the MS is located; and 3) the scattering power density function around the MS is expressed by a combination of two Laplacian distributions in which the standard deviations are different. To verify the proposed model and obtain realistic values for the model parameters, the spatiotemporal path data observed at a base station (BS) were measured using a 2.2-GHz band in a macrocell scenario (BS antenna height is 60 m) in a typical urban area. The scattering positions are detected from the path information such as the azimuth arrival angle and path length, assuming a single bounce. The spatial distribution of the scattering power is analyzed using principal component analysis. The results showed the ESA to be the anticipated ellipse with the major and minor axes of approximately 210 and 120 m, respectively (axis ratio: approximately 1.7). Furthermore, the power profiles that are projected for each axis of the ellipse can be approximated as Laplacian distributions. Finally, simplification of the proposed model is discussed

Channel modeling for 2-GHz-band urban line-of-sight street microcells

A channel model is presented for line-of-sight (LOS) street microcells with low-antenna-height base sites. This channel model assumes some virtual reflection points (VRPs) located at the intersection points along the LOS street and at building walls under the LOS condition. The VRP locations can be specified for the street structure, so this channel model behaves as a location-specific model. Using this VRP model, the delay profile can be predicted under nonfading and nonshadowing conditions for all propagation paths, and in laboratory experiments the bit error rate (BER) performance of /spl pi//4-shift DQPSK transmission can be evaluated. A comparison with 2-GHz-band field experiments shows that the best result for BER evaluation is obtained when the VRP attenuation parameter is 0.08. This channel model is a very useful means of predicting the signal transmission performance of LOS street microcellular systems.

Clustering of local scattered multipath components in urban mobile environments

This paper presents the clustering mechanism of multipath components in urban environments. A cluster in an urban area originates from a scattering point located atop a building or on a wall. The degrees of visibility both between the base station and the scattering point, and between mobile station and the scattering point determine the incoming scattering waves. Shadowing caused by surrounding buildings determines the degree of visibility, and this depends on the base station height and the arrangement and irregularity in height of the surrounding buildings. Vector channel measurements at 5.2 GHz in an urban area in Tokyo verify the clustering mechanism.

Prediction of Line-of-Sight Propagation Loss in Inter-Vehicle Communication Environments

This paper presents a prediction formula of propagation loss for low antenna height scenarios on a line-of-sight (LOS) straight-line road having an intersection, for modeling the propagation loss characteristic in inter-vehicle communications (IVCs). The regression analysis is applied to the propagation loss data generated by computer simulation based on the geometrical optics theory, and the regression formula is established as a dual-slope model having variables of propagation distance, frequency, road width, and antenna height. In this analysis, the position of breakpoint is determined so that the RMS error of the regression becomes the smallest on both slope regions because its position is an important factor for good prediction accuracy. Furthermore, the comparison between predicted and measured propagation losses is performed in 2 GHz and 5 GHz bands, and the effectiveness of the prediction formula is confirmed by evaluating the prediction errors.

Channel modeling for 2 GHz band urban line-of-sight street microcells

The paper proposes a channel model for LOS street microcells with low antenna height base sites. This channel model assumes some virtual source point (VSP) and locates then at the intersection points along the LOS street and building walls under the LOS condition, and so is developed as a location-specific model. The predicted delay spread has excellent agreement with experimental results when the VSP attenuation constant is 0.07. Using the proposed model, the bit error rate (BER) performance of /spl pi//4-shift DQPSK transmission with and without diversity reception can be evaluated. Its effectiveness is confirmed by field experiments.

Directional measurement and analysis of propagation path variations in a street micro-cell scenario

We present results from field experiments in a street-micro scenario downtown Tokyo, which have been carried out to explore the main mechanisms leading to path parameter variations. The measurements have been carried out using a wideband-vector-channel-sounder. The transmitter (mobile station) was equipped with an omni-directional antenna whereas at the receiver (base station) a uniform linear array has been used. The parameters of the dominant propagation paths have been estimated using high-resolution parameter estimation algorithms (joint unitary ESPRIT and SAGE). From these parameter estimation results three main mechanisms leading to propagation path parameter variations have been discovered. The observed channel characteristics are useful for the development of realistic directional urban multi path propagation models.