Hironari Masui

Microwave path-loss modeling in urban line-of-sight environments

To model the path-loss characteristics in microwave urban line-of-sight (LOS) propagation, we performed measurements in metropolitan Tokyo at frequencies of 3.35, 8.45, and 15.75 GHz. The actual breakpoint distance was shorter than the theoretical one because of the influence of vehicles, pedestrians, and other objects on the road. This effect has been referred to as effective road height. We found that the breakpoint disappeared when the mobile-antenna height approached the effective road height. Based on these breakpoint characteristics, we propose new upper- and lower-bound formulas for LOS path loss in urban microcellular environments. They will be useful for the system and cell design of fourth-generation multimedia mobile communication systems using microwave bands.

LOS and NLOS path-loss and delay characteristics at 3.35 GHz in a residential environment

Measurement results are discussed for the path loss and delay characteristics of microwave transmissions from a low base station antenna for a LOS and multiple NLOS paths in a suburban residential area. While propagation corner losses of 30 to 35 dB occurred that increased abruptly for the NLOS courses, it was found that the distance path loss coefficient decreased at about the same rate as the LOS course, at a rate of the distance squared (/spl alpha/=2). Allowances must be made for the presence of different topological features such as open spaces or spaces between the rows of houses in the vicinity of the base station, which would cause the distance path loss coefficient to vary as /spl alpha/ becomes small to, for example, about 0.25. The delay spread was dependent on distance, and the NLOS delay spread was found to be several times larger than that of the LOS course. The standard deviation of delay spread for the NLOS courses ranged from 80 to 200 ns, which was an order of magnitude larger than that of the LOS course. The increase in the delay spread as a function of distance for the NLOS course was several ns/m, some one order of magnitude larger than that of the LOS course. The delay profile for the LOS course conformed with the power type model, but the exponents ranging from 1.9 to 2.9 were smaller than those obtained in urban environments. It was found that the models which have been proposed in the past do not account well for the NLOS data obtained in this work.

Microwave path-loss characteristics in urban LOS and NLOS environments

To model the path-loss characteristics of microwave propagation in urban environments, we performed measurements at frequencies of 3.35, 8.45, and 15.75 GHz in metropolitan Tokyo. The actual breakpoint (BP) distance was shorter than the theoretical one because of the influence of vehicles, pedestrians, and other objects on the road. This effect can be characterized in terms-of the effective road height. We also found that the BP disappeared when the mobile-antenna height approached the effective road height. In non-line-of-sight (NLOS) areas, the corner losses and attenuation coefficients were greater than those of the UHF band. The attenuation coefficients increased with LOS distance between the base station and the corner into NLOS area.

Spread spectrum slot reservation multiple access

A new method of data transmission is proposed for mobile communications. It is similar to the traditional split channel reservation multiple access (SRMA): a mobile user (MU) reserves transmission slots from a base station (BS) and then transmits according to the BS scheduling. However, in the proposed method a number of MUs can transmit concurrently using the direct sequence spread spectrum (DS-SS) technique. The DS-SS technique is also used at the reservation stage where a multiple-slotted-ALOHA (m-S-ALOHA) technique allows multiple users to simultaneously reserve service. Theoretical and simulation results show significant increases in throughput efficiency for the proposed method compared with the traditional SRMA technique.

Microwave spatial-temporal channel characteristics measured at base station in an urban environment

The propagation measurements were performed in an urban area at 8.45 GHz. We examined the characteristic of delay and angle spreads of main arrival waves at the base station receiving antenna. The delay spread tends to increase with the angle spread. Both angle and delay spreads in NLOS environments were larger than those in LOS environments. Delay spreads in NLOS environments are greater those at the points in LOS environments yielding the same angle spread.

Microwave propagation characteristics depending on base-station antenna height in an urban area

We have conducted propagation experiments assuming the environment of low base station antenna height and, hence, microcells in an urban area and have reported their results. In this report, we report the results of a propagation experiment in the microwave band that is conducted with transmission base station antennas installed at height sufficiently higher or lower than the surrounding building height. In particular, effects of the base station height on characteristics of path loss and delay spread are reported.

Microwave propagation characteristics in an urban LOS environment in different traffic conditions

In microcellular environments, the traffic condition on the streets greatly influences the propagation characteristics especially in the microwave bands. It is crucial for the blocking effect of traffic to be introduced to propagation models. This paper presents an experimental study of the effect of vehicular and pedestrian traffic on the path loss and delay spread characteristics.

Effects of road traffic on probability distributions of path loss in an urban microcellular environment

One of the key parameters of radiowave propagation characteristics is the temporal change in the surrounding environment. Here, we report the development of a system for measuring line-of-sight (LOS) centerline blocking and its use in measuring the path loss when the LOS centerline is blocked in LOS propagation in an urban environment with low base station antenna height. The results of statistical processing of path loss for when there is centerline blockage by vehicles and when there is no blockage are presented.

Performance of parallel transmission applied to broadband mobile communication systems in urban multipath environments

This paper describes a method of evaluating transmission performance of parallel transmission in multipath propagation environments. Delay profiles measured in metropolitan Tokyo at a microwave frequency were used to obtain radio channel impulse responses, and the characteristic function method was used to efficiently estimate transmission performance under the assumption that the impulse responses have uniform distribution phases. Results show that the performance to be obtained by applying the parallel transmission technique is 100 times better than that of bare transmission in an example of a source data rate of 10 Mb/s.

Performance prediction of digital mobile communication systems in urban multipath environments

Delay profiles were measured at three microwave frequencies (3.35 GHz, 8.45 GHz, 15.75 GHz) in order to predict transmission performance of digital mobile communication systems. The transmission performance was efficiently obtained by computer using a stochastic method based on the characteristic function method. The results showed that the transmission performance fluctuated even in the close vicinity of the transmission antenna and that megabit-per-second transmission rates was feasible in an urban multipath environment.