In this study, we evaluated the relationship between the time variability of the transmission characteristics of multimode fiber (MMF) and laser linewidth. By varying the laser linewidth from 0.1kHz to 1.89THz, it is possible to grasp the tendency over a wide range, from narrow to ultra-wide linewidth. We were able to confirm that the time-varying characteristics of the frequency characteristics, which affect the MMF transmission characteristics, depend on the laser linewidth and time variability decreases with an increasing laser linewidth.

Detecting signals in areas where there are many obstacles, such as Non-Line-of-Sight (NLoS) is difficult, in conventional radar systems. In this study, we investigated a radar system for detecting pedestrians in NLoS using a secondary radar system and oversampling of the received waveform in an on-board device; then, measured the range and direction detection properties. We analyzed the results of these experiments that were measured in a large anechoic chamber with metal walls to emulate NLoS conditions. The direction of the target in the NLoS was successfully detected. The proposed scheme was able to measure the distance to the target within an error margin of 5m.

This paper proposes a platform for electromagnetic interference on Ethernet communication devices due to conducted noise from power conversion circuits, focusing on the electromagnetic near-field coupling between the DC bus and the communication line. The waveforms measured on the platform during switching transients reveal the mechanism of communication failure. The Ethernet performance evaluation by a network protocol analyzer shows that the converter switching frequency impacts the communication error rate.

Usage of higher frequency bands enable a new possibility for the exploitation of the physical properties of electromagnetic waves such as bended propagation, nondiffractive propagation, and orbital angular momentum. We characterize new concept that takes full advantage of such physical properties a “multishape radio.” As a representative case, we explore the Airy wave that has the unique feature of bended propagation with asymmetric sidelobe distribution. We experiment using sub-THz frequency bands to demonstrate that Airy waves can be used for parallel transmission of multiple streams without causing harmful interference.

We study about point-to-multi-point (PtMP) downlink transmission that simultaneously accommodates a high-capacity guaranteed backhaul-link and best-effort access-links using orbital angular momentum (OAM) multiplexing. OAM multiplexing is executed on the backhaul-link, and other pieces of user equipment use parts of the OAM modes that are not used in the backhaul-link. We propose a prioritized resource-control method that maximizes the capacity of the access-links while maintaining the capacity of the backhaul-link above the target value for PtMP downlink transmission using OAM multiplexing. We evaluated the performance of the proposed method through simulations and outdoor transmission experiments.

We propose a resource allocation method that considers the mode dependence of inter-core crosstalk (IC-XT) in space-division multiplexing elastic optical networks with few-mode multi-core fiber (FM-MCF). In FM-MCF environments, IC-XT tends to increase when higher-order modes or detour routes are used. It is not clear whether the IC-XT can be reduced more effectively by preferentially using detour routes or higher-order modes. To make IC-XT as small as possible, this paper proposes a route and mode selection scheme combined with the conventional core prioritization. Simulation results show that the proposed method reduces the lightpath blocking rate to a 50 times smaller value than that of a naïve benchmark.

This paper introduces a new acquisition technology, which can completely eliminate side peaks and obtain better acquisition performance. This method is effective for BOC(n,n) modulated signals. The basic idea of this method is to construct a special local auxiliary signal, cross-correlate it with BOC modulated signal, and use the cross-correlation function curve and autocorrelation function curve to do certain operations to eliminate the secondary peaks of autocorrelation function curve. Experimental results show that compared with other typical algorithms, this algorithm can better and thoroughly eliminate the secondary peaks of BOC signal.

As a simple method to simulate a dynamic indoor environment, we investigated a method to calculate the shielding effect of moving objects. In this method, the shielding effect is included in post-processing on the results of ray tracing calculations that does not include objects. The post-processing time of this method depends on the numbers of ray-traced paths. We applied a path clustering method for ray-traced paths in advance to reduce the post-processing time. As a result, the calculation time of the dynamic indoor propagation environment is reduced compared against conventional ray tracing.

This study investigates the effectiveness of orbital angular momentum (OAM)-MIMO with successive interference cancellation (SIC) in the presence of ground reflection using computer simulations. In OAM-MIMO with SIC, the effect of SIC is naturally enhanced using the specific property of OAM, where a significant difference in the received power occurs among different uniform circular arrays (UCAs). In this study, we assume a two-ray ground-reflection model as a radio channel model and evaluate the system capacity of OAM-MIMO with SIC considering inter-mode and inter-stream interferences due to ground reflection. Moreover, considering that the polarization planes affect the different reflection coefficients, we investigate the impact of polarization planes on the performance of OAM-MIMO with SIC.

Crowdsourcing can improve the accuracy of crime detection, which is difficult with a computer-based method. This study evaluates a crowdsourcing-based method’s accuracy, cost, and detection time using a task to discriminate whether the crime of shoplifting is occurring in surveillance camera video footage. This evaluation is made through a comparison with existing solutions.

A failure rate estimation method is proposed herein considering changes in the number of equipment. Failure rate is an important factor for evaluating the operational reliability of a telecommunication network; however, it requires calculation of the first-order derivative of the cumulative failure and number of equipment. The proposed failure rate approximation considers changes in the number of equipment without requiring derivative calculations. The proposed method was verified using actual failure data/number of equipment, and the results confirm that the failure rate can be evaluated quickly and accurately using the proposed method.