We propose a novel nonlinear distortion compensation technique using linear phase transition approximation for long haul optical communication system. Self-phase modulation (SPM) for phase change, and amplified spontaneous emission (ASE) from erbium-doped fiber amplifier (EDFA) are taken into consideration in simulation. It is confirmed that phase of 28Gbaud return to zero-quadrature phase shift keying (RZ-QPSK) signals compensated with split-step Fourier methods (SSFM) change almost linearly. They can be estimated using linear approximation with only two points of any span for low computational complexity. The performance of this technique is evaluated by bit error rate (BER) with numerical analysis. The achieved reduction of computational amount is 70.0% when transmission distance is 2500 km and input power is 0 dBm at a FEC limit of BER < 10⁻³.

Recently, the capsular endoscope that has extra function has been investigated. Although the power consumption tends to increase as the ability increases, it is difficult to increase the capacity of the battery due to the volumetric problem. In this study, we proposed an antenna for both wireless power transmission and image transmission to be mounted on a capsule endoscope. In this paper, we discussed the requirements desired to antennas to be mounted in capsular endoscope.

A dual-band coil antenna is proposed for MHz band on-body Wireless Body Area Network (WBAN) applications by near-field coupling, with relatively low attenuation from the human body. The proposed antenna has two operating frequencies at 48.2 and 57.6 MHz with the measured −10-dB bandwidth 47.9–48.6 MHz and 57.1–58.2 MHz, respectively. Matching circuits are used to reduce the antenna size and tune the resonant frequencies. A human phantom is used for the antenna simulation and measurement. Reflection and transmission coefficients and electric and magnetic field distributions of the proposed antenna are shown, and 1-g and 10-g average Specific Absorption Rate (SAR) and the maximum safety input power are calculated to evaluate the antenna’s radiation safety.

A low-profile antenna having four directional beam patterns using loop elements has been proposed. The proposed antenna is vertically polarized and has four directional beams for sensor nodes. The thickness of the antenna is only 3.2 mm (0.11 effective wavelength) resulting in a low-profile structure. Simulated and measured average gain of 8.0 dBi and 5.6 dBi are obtained, respectively.

Dual-carrier 400-Gbps channels in C+L-band are transmitted over dispersion shifted fiber (DSF) in field for the first time. Distributed Raman amplification not accompanied by EDFA (all-Raman amplification) is used to suppress the nonlinear distortions, which strongly occur in the zero-dispersion region in C-band. The transmitted distance is 200 km and the maximum distance is expected to be 480 km, while the Raman pump power is lower than a safety level for commercial use. The field experiment demonstrates that all-Raman amplification is feasible for effective use of existing DSF links in regional optical networks.

This study demonstrates precision non-destructive inspection of periodic linear targets using polarimetry technique used in radars with frequency bands from P to W (0.3 to 110 GHz) and broadband terahertz pulse. The polarimetry technique is effective to identify targets in radar field, and terahertz waves are effective for non-destructive inspection due to its broadband and special penetration characteristics. In this study, we combine the both techniques to enhance the inspection accuracy. Our analytical and experimental results confirmed that the combination of the polarimetry technique and the broadband terahertz pulse wave was effective for the precision inspection of the targets.

Higher-order modulation is promising technique of 5th-generation mobile systems to increase data rate within a limited bandwidth. This paper presents the transmission performance of the orthogonal frequency division multiplexing (OFDM)-based 1024-QAM in multipath fading propagation conditions by link-level simulation, as well as under static propagation condition. The BER performance is investigated for two types of propagation models, i.e., “extended pedestrian A” and “extended vehicular A” models, specified by 3GPP as parameters of the coding rates. The SNR penalties are also described with respect to the case of AWGN with phase error to meet a BER of 10⁻² for OFDM-based 1024-QAM. Using these results, we validate the application of OFDM-based 1024-QAM to mobile communication systems.

The wide spread of mobile communication devices has increased the opportunities to use wireless communication technologies, irrespective of one’s geographical location. However communication quality deteriorates due to factors such as competition for scarce radio resources and interference among nearby devices. Cognitive radio technologies have been developed recently to conquer such difficulties. In this paper, we propose a wireless network optimization method using learning algorithms based on a control model known as cognitive cycle. We implement the proposed optimization method in wireless LANs and evaluate the throughput performance. The experimental results show the effectiveness of the proposed approach in a real environment.

A small planar antenna composed of folded slots is proposed for mobile communications, especially for being mounted on unmanned aerial vehicles (UAVs). Bending slits are made rotationally symmetrically on top and bottom sides of a printed circuit board. The slits are joined in pairs via open edges of the printed board to form slots spanning over both the sides. The directivity is omni-directional and the polarization is dominantly horizontal. The antenna can be controllably miniaturized by being made of a thinner substrate because the resonant frequency decreases as the substrate thickness decreases. Influence of an adjacent conductor plate is examined for the actual usages of being mounted on UAVs and mobile terminals.