Kenya Yonezawa

Estimation of high frequency NLOS path loss in street-cell environment

A study of how street width effects to street-cell NLOS path loss is presented in this paper. Street cell models with various street widths are composed by statistically generated building layouts. Then path loss in the cells is calculated by shooting and bouncing rays (SBR) method. Numerically simulated results are then compared with measurement data, obtained at Iwaki city, Japan. Our statistically derived path loss lines have found to have slightly larger loss than that of International Telecommunication Union Radiocommunication section (ITU-R).

Performance Evaluation of Centralized Control Algorithm for Channel Allocation in Pico-Cell System

In a pico-cell architecture, co-channel interference between adjacent cells can cause serious problems. With a centralized control approach based on interference information reported by each subscriber station (SS), we propose a novel channel allocation algorithm applying the graph theory. This method directly determines the optimal channel allocation and minimizes inter-cell co-channel interference. Both computer simulations and experiments based on the implementation demonstrate that our proposed algorithm is effective.

Propagation Characteristics Measurements for Multi-Site MIMO Systems in Urban Micro-Cellular Environment

Multi-site MIMO (MS-MIMO) technology, where multiple base stations cooperate on the transmission for a user, is expected to improve user throughput at the cell edges. We conducted a propagation measurement campaign assuming MSMIMO systems in an urban city using three synchronized transmitters. In this paper, several results of measured characteristics are reported, and the performances of MSMIMO systems are evaluated using the measured data. KeywordsMS-MIMO, BS cooperation, MIMO, propagation measurements, Eigenvalue, micro-celullar systems, high BS antenna

NLOS path loss evaluation for street-cell environment

Non line of sight (NLOS) path loss has been investigated by using the Shooting and Bouncing Rays (SBR) method. Two building layouts; continuously connected and non-connected building layouts, are used to check the street propagation characteristics and leakage effect due to the building gaps. Based on the statistical data numerically generated buildings are placed along the streets and path loss are evaluated along them. It is found that the predictions by ITU-R model give us somewhat less path loss for our street- cell models.

Street-Cell NLOS Path Loss Estimation Using SBR Method

The effect of building layout in street-cell model on path loss is investigated by using shooting and bouncing rays (SBR) method. A comparison of path loss between measurement and simulations of two different models confirms that only buildings along measurement path contribute mainly, while the others can be neglected. Our prediction results have been found to match well with the measurement results.

A Novel Frequency Channel Allocation Method for 2.4 GHz Wireless LAN

In this paper, we propose a novel frequency channel allocation method for 2.4 GHz WLAN. Because several WLAN systems are concurrently operated in the 2.4 GHz band, the interference from other systems needs to be considered. The proposed method mitigates interference both in own system and that from other WLAN systems. The method is based on a measurement result obtained with a survey tool. A technique for reducing the number of channel allocation patterns is introduced to search for adequate channel allocation, and it was confirmed that the computation time could be reduced to less than hundredth that required for the simple exhaustive search method. Both computer simulations and actual measurements demonstrate that the proposed method is effective.

Variable beam tilt microstrip array for 5 GHz wireless access system

This paper presents a variable beam tilt array using electromagnetically coupled patch elements. Two antenna elements are excited with the phase difference of 90/spl deg/ and the spacing is adjusted around quarter wavelength to change the beam tilt. The antenna element is coupled electromagnetically to the feeding stub, which is easy to move for variable beam tilt. Numerical simulation shows the beam tilt angle is adjusted from 30 to 60/spl deg/. This variable beam tilt is effective in changing the coverage area of indoor base station antennas for 5 GHz wireless access systems.