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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.

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).

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.

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.

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.

Spin transfer magnetization switching is studied in nano-pillars with a synthetic antiferromagnetic free layer (SyAF), CoFe/Ru/CoFe, under an external magnetic field. The resistance change for the conventional type nano-pillar (CoFe) and SyAF type sample is almost the same, demonstrating full reversal of the magnetization. On the other hand, the critical current as a function of magnetic field for the SyAF type is found to behave in the opposite way with that of the conventional type.

We measured path loss in a macro cellular environment in 5 GHz band. In this paper, existing propagation models for path loss prediction in UHF band are applied to 5 GHz band, and the estimates are compared with the measured data. From the results of the comparison, we describe the differences between the measured and the estimated data.

In office buildings, the requirement is that the room air-conditioning control system has to provide comfortable thermal feeling for the working people. While energy saving may sometimes conflict with comfort, it is possible to eliminate the wasteful use of energy associated with its overuse without prejudicing the comfort. The basic concept is that the target set values for the room temperature should be changed dynamically so as to suit the constantly changing room environment. The paper shows that the well-known comfort index PMV is useful for air-conditioning control systems aimed at both energy-saving and comfort.

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.

In buildings such as offices and department stores, the requirement is that the room air-conditioning control system has to provide a comfortable thermal feeling for the inhabitant. While energy saving may sometime conflict with comfort, it is possible to eliminate the wasteful use of energy associated its overuse without prejudice to comfort. The basic concept is that the target set values for the room temperature should be changed dynamically so as to suit the constantly changing room environment. This paper shows that the well-known comfort index PMV is useful to air-conditioning control systems aimed at both energy-saving and comfort.

Power transmission lines in the USA face to the problems like: (1) antiquated and overworked; (2) objection from inhabitants to construct new transmission; (3) lack of coordination with IPPs on the grid efficiency; and (4) unexpected growth in electricity consumption. One way to solve these kinds of problem is to increase the current capacity of existing transmission lines by re-stringing the conductor, which have higher current capacity. In this paper, the authors examine the application of gap conductors for such uprating schemes.