The aim of this study is to develop an accurate and reliable method for estimating the propagation characteristics inside and outside aircraft cabins so as to advance the radio link design techniques for WAIC systems. This paper uses the FDTD method and large-scale parallel computing to conduct the world’s first study on the propagation characteristics of signals emitted by a transmit antenna above the wing tip to WAIC antennas installed inside and outside the aircraft cabin (Airbus 320-200). EMF distributions created by a 4.4 GHz wireless transmitter inside the cabin are analyzed and propagation characteristics are determined from the analysis results.

In Vehicular Ad Hoc Network (VANET), it is important to detect false information. The previously published scheme detects the false information by utilizing vehicle density to verify validity of the information. However, this scheme cannot verify validity of the density. We propose a false density information attack detection scheme using overlap of communication range of vehicles. Since a vehicle can calculate the number of vehicles in neighbor’s communication range using a received density, the density can be detected as false if there are too much vehicles outside of the overlapped range. Simulation results show that the proposed scheme improves the true positive rate of false information detection.

Our recently proposed adaptive space-time block coded transmit diversity (STBC-TD) jointly used with frequency-domain equalization and decision-feedback linear prediction (DFLP) provides a good bit-error rate (BER) performance in a high-mobility environment. However, in a low-mobility environment, the achievable BER performance degrades. In this paper, we propose an improved adaptive STBC-TD, in which the use of DFLP is adaptively decided based on the minimum mean square error (MMSE) criterion of the soft-decision symbol output. Computer simulation results show that the improved adaptive STBC-TD achieves a good BER performance over wide ranges of the transmit symbol energy-to-noise power spectrum density ratio (E_s/N₀) and the normalized maximum Doppler frequency (f_DT).

This paper proposes double decision-feedback multiple differential detection (DDFMDD) of double differential encoding (DDE) for fast time-varying Rayleigh fading. DDE can improve tracking capability at a large modulation alphabet size. In order to improve performance in the required signal to noise power ratio (SNR) and tracking capability aiming at higher frequency efficiency, the proposed DDFMDD employs decision-feedback multiple differential detection (DFMDD) with channel averaging and DFMDD with channel prediction. Finally, computer simulation results confirm that the proposed DDFMDD has excellent bit error rate (BER) performance for fast time-varying Rayleigh fading at a larger modulation alphabet size.

Spatial diversity is still remaining as a powerful means to improve the transmission performance in a multipath fading environment. Various spatial diversity schemes have been proposed such as maximal-ratio transmit and combining (MRTC), selective MRTC, and space-time block coded transmit diversity (STBC-TD). In this paper, we derive a closed form expression for the received signal-to-noise ratio (SNR) achievable with MRTC for the case of base station (BS) having an arbitrary number of antennas and user-equipment (UE) having 2 antennas. Using the derived SNR expression, the average bit error rate (BER) performance of quaternary phase shift keying (QPSK) transmission in a Rayleigh fading environment is numerically evaluated. It is shown that MRTC provides the BER performance superior to STBC-TD and selective MRTC.

Multi-user multiple-input multiple-output (MU-MIMO) using a large number of spatially distributed antennas (DAs) is a promising technique to achieve high link capacity uniformly over a macro-cell area. To reduce the computational complexity of MU-MIMO processing, the UE clustering can be used. However, this produces the inter-cluster interference (ICI) and degrades the link capacity of a user equipment (UE) especially near the cluster boundary. In this paper, to solve the ICI problem, we propose a dynamic UE clustering in which UEs in a macro-cell area are grouped into non-overlapped UE cluster-sets and they are activated in a time-division manner. We evaluate, by computer simulation, the UE link capacity of OFDM downlink achievable by the use of the proposed dynamic UE clustering.

We demonstrate 2^nd-order forward-pumped distributed Raman amplification (DRA) in PDM-16QAM 25-GHz-spaced 11-channel WDM transmission system in L-band. Our forward-pumped DRA consists of semiconductor-optical-amplifier-based incoherent light source for signal amplification and two coherent light sources for incoherent light amplification. After 1,760 km single-mode-fiber transmission, 1.2-dB Q-improvement is experimentally achieved by our DRA scheme compared with that of in the case of amplification with EDFA only. And we also show the low RIN-transfer-induced Q-penalty of our pumping scheme at the Raman on/off gain of up to 10 dB.

Recently, a channel estimation method using channel sparsity in beam space has been studied. This method, which is called beam space channel estimation (BSCE), is effective for massive multiple-input multiple-output (MIMO) systems because a larger number of antennas makes channel responses in beam space sparser. However, each of previous studies has used a specific channel model for evaluating the performance of BSCE although the channel model affects the performance. In this paper, we compare the performance of BSCE between line-of-sight (LOS) and non-LOS (NLOS) environments and clarify the effect of the difference in the channel sparsity on the performance.

The relation between maximum common mode current and maximum radiated magnetic field strength was experimentally studied using a simple power distribution line model. The common mode current was measured along the cable and the radiated magnetic field strength was measured around the model. They were evaluated using the S₂₁ parameter. The frequency characteristic of both the maximum current and the maximum strength showed a closely similar pattern. Our evaluation of their correlation indicated that the relation between the maximum common mode current and the maximum radiated magnetic field strength could be represented by a straight line, and that 80% of the measured data was contained within 2 dB of the regression line.

5th generation mobile communications system (5G) is being actively researched and developed. We focus on “Ultra-Reliable and Low-Latency Communications”, with the goal of V2V communications in platooning; a highly anticipated function for autonomous driving. V2V direct communications play a very important role in realizing platooning. Studies of V2V direct communications in platooning have found spectrum spreading in excess of the maximum Doppler frequency which depends on frequency and moving speed. This studies the characteristics and phenomena unique to platooning; we find that the direct wave basically has no Doppler shift. However, we show that Doppler shift of up of twice the maximum Doppler frequency is observed although at a weak level, and we clarify the communication environment by various experiments.

Microstrip patch antenna (MPA) with loading of shorting pins expressed as a high gain and planar structure. The inductive effect of shorting pin tunes up the resonant frequency leading to increase the electrical size of antenna and, in consequence, its radiation directivity is enhanced. This work proposes a new configuration of MPA with loading of via holes to achieve gain enhancement. The field distribution is analyzed to optimize position of via holes. A prototype of proposed MPA is fabricated and shows excellent realized gain of 11.3 dBi that enhance about by 1.3 dB in comparison to the previous work.

This letter presents a robust blind multiband detection (BMD) scheme for cognitive radio (CR). In the proposed scheme, the BMD problem is firstly transformed into a model order selection (MOS) problem, and then an effective clustering method is proposed to determine the subband state. Our scheme is easy to implement and has high computational efficiency. Most importantly, unlike the classical BMD schemes based on the information theoretic criteria, our scheme can be used in both the nonuniform and the uniform noise powers scenarios. Simulation results verify its effectiveness.