This paper proposes a cloud provider selection scheme for cloud storage services to minimize the total cost of usage. The proposed scheme satisfies the user’s requirements using multiple cloud providers. The proposed scheme considers the time-dependent unavailability and multiple-user environment. The cloud provider selection problem is formulated as a linear programming problem. We evaluate the total cost of usage of our scheme for the various allowable numbers of cloud providers. Numerical results show that the proposed scheme with multiple cloud providers reduces the total cost of usage, compared to that with only one cloud provider. The total cost of usage is more reduced if the time-dependent scheme is used.

This paper proposes an efficient design method of multiuser multiple input multiple output (MIMO) downlink system assuming use of a large array antenna in transmitter side. To reduce the heavy computational load required for transmit weight design, the large antenna is first divided into several subarrays, and block diagonalization method is applied to each of them. Then subarrays are again synthesized to a large array with the original size based on the concept of the maximum ratio combining (MRC), where two kinds of strategies, the transmitter first design and the receiver first approach are considered. Computer simulations show that the performance is degraded from the original method, but it can be achieved with significantly low computations so that it is utilizable even when the conventional block diagonalization is computationally impractical.

An in-phase/anti-phase triple-feed array antenna employing two types of magic-Ts is proposed. The proposed array antenna effectively provides three radiation patterns in both E- and H-planes with a simple structure. In this paper, design and operating principles of the proposed array antenna is presented with simulation results to highlight its features. The proposed array antenna can be used for many kinds of advanced antennas such as direction-of-arrival estimation antennas, beam steering antennas and wide-angle rectennas.

This paper proposes a new dynamic bandwidth allocation (DBA) method with low latency for campus area networks (Campus-LANs) and mobile fronthaul (MFH) based on time division multiplexing passive optical network (TDM-PON). These network systems require low latency of under 100 µs and priority control. The proposed method involves only two steps for allocation. The DBA cycle value, which is proportional to the latency, can be minimized because this method is very simple and appropriate for hardware (H/W) implementation. We implemented the proposed DBA on 10G-EPON MAC SoC and evaluated the allocation results and the latency on the 10G-EPON system. Our DBA offers ultra-low latency of 60 µs with priority control.

Frequency identification for the mobile communication system in 275–450 GHz was started in the World Radiocommunication Conference 2015. Therefore, propagation model is required to enable sharing and compatibility studies between the land-mobile, fixed and passive services. In this study, indoor propagation characteristics at 300 GHz is measured and analyzed to develop path loss models. Measurements have been carried out in office and corridor environments in line-of-sight situation, and the path loss coefficients are extracted. The coefficient of office environment is roughly identical with the free space loss of N = 20, and the coefficient of corridor environment was slightly decreased to N = 19.5.

We propose a mode-dependent transmission-loss measurement technique for a two-mode fiber (TMF) using nonlinear least-squares regression of the data obtained by a conventional optical time-domain reflectometer (OTDR). The transmission loss of a 15-km-long TMF is successfully estimated by neglecting mode-coupling during propagation.