Since data obtained by Internet of Things devices is correlated with their locations, location-based services of exploiting such locality are promising. An example service is that a driver, i.e., a collector of data, asks cars on the road 2 km ahead of her or him how many cars are driving there. Since such a service requires low latency multicasting communication, this paper designs a low latency publish/subscribe mechanism by leveraging name-based communication like Named Data Networking.

This paper presents a user throughput performance analysis of a coordinated radio-resource scheduler with a hardware accelerator for the fifth generation of mobile communications systems (5G). To ensure fairness among mobile terminals (MTs) in 5G ultra-high-density distributed antenna systems, the transmission weight matrixes for a huge number of possible combinations of antennas and MTs have to be computed in a coordinated radio-resource scheduling process. To accelerate the computation, we devised a scheduler that executes the computation on dedicated hardware. System-level simulations reveal that the scheduler with a hardware accelerator composed of 5.3 Mgates obtains around 20 Mbps at the 5th percentile of average user throughput for 256 MTs. Computational resources are hence the critical factor in obtaining high average user throughput and ensuring fairness among MTs.

This paper proposes a low latency incremental redundancy hybrid ARQ (IR-HARQ) scheme for a multiband wireless local area network (WLAN) system. The proposed scheme can reduce a retransmission delay and ensure backward compatibility with WLAN devices by using a clear to send (CTS) frame of a current WLAN system and rate compatible low-density parity-check (RC-LDPC) codes. Additionally, it can minimize the retransmission delay by selecting an optimal retransmission data length on the basis of the accumulated mutual information (ACMI) for available frequency bands. The results of computer simulations show that the multiband WLAN system using the proposed scheme has shorter retransmission delay and higher system throughput than the current WLAN system.

In this paper, we propose an adaptive minimum mean square error filtering combined with singular value decomposition (MMSE-SVD) for OFDM downlink multi-user multi-input multi-output (MU-MIMO) transmission. During data transmission, base station (BS) updates the multi-user MMSE transmit filter by using linear channel prediction, while user equipments (UEs) update their eigenmode receive filters, constructed by SVD, by using decision feedback adaptive channel estimation. The uncoded BER performance achievable by adaptive MMSE-SVD is evaluated by computer simulation. It is shown that proposed adaptive MMSE-SVD can increase an allowable maximum Doppler frequency (f_DT) for keeping BER < 10⁻² by about 4 times.

There are various types of AC/coaxial adapter for line impedance stabilization network (LISN) calibration because the AC plug used differs among countries. The difference in the characteristics of the adapters may be large at a high frequency such as 1 GHz; thus, their characteristics should be compared. In this paper, the transmission characteristics of one-phase AC/coaxial adapters for Japan (A-type) and UK and some Asian countries (BF and B3-types, respectively) are compared using their equivalent circuit models. The following two results are obtained: (1) the BF-type most strongly affects the LISN calibration, and (2) the transmission coefficient of the A-type is the least affected by the reference ground.

We propose an interferometric technique for directly measuring the chromatic dispersion of the high-order mode in a few-mode fiber (FMF) by using a mode converter (MC). We successfully estimate the chromatic dispersion of the LP₁₁ mode in the test fiber by using the proposed technique.

Nowadays, mobile communication technology has become essential; thus, it is important to consider the effect of electromagnetic radiation from mobile terminals such as smartphones on the human body. In this study, we calculated the specific absorption rate (SAR) and temperature increase in pregnant women exposed to a smartphone’s radiation at 13, 18, and 26 weeks of gestation. The results indicate that the SARs were much lower in fetuses than in pregnant women under all of the calculation settings in this study. Moreover, the maximum temperature increases in fetuses were half of those in pregnant women.

While Quality of Service (QoS) is a service quality indicator that is used as objective evaluation by service providers, Quality of Experience (QoE) is a quality indicator subjectively evaluated by users. However, subjective evaluation of QoE for every service imposes the users a great load. Therefore, it is needed to estimate QoE from a physiological index without every subjective evaluation. In this research, we focus on skin conductance activity (SCA) as a physiological index and develop an experimental scheme to clarify the relationship between QoE and SCA when abrupt playback pause degrades the video quality. As the results of experiment and data analysis, QoE and SCA are correlated differently according to the video categories such as sport and news.

A novel multilayer structure of a direction-of-arrival (DOA) estimation antenna is proposed in this paper. This antenna provides dual-axis DOA estimation, while conventional monopulse DOA estimation antennas determine arrival angle in a single plane. The proposed antenna has a multilayer structure and consists of four ring-slot antennas and four magic-Ts. The proposed antenna provides both xz- and yz-plane dual-axis DOA estimation by using the monopulse mechanism.

An evaluation reveals the feasibility of a high-gain and low-fabrication-cost reflectarray antenna for W-band millimeter-wave radar applications. This reflectarray antenna offers the advantage of a simple, flat structure, and can be fabricated at low cost by three-dimensional (3D) printing. This paper describes the fabrication of a 3D-printed reflectarray antenna, whose gain is more than 30 dBi in the W-band. Firstly, the reflection-signal phases of dielectric plates of different thicknesses are evaluated using finite-difference time-domain (FDTD) analysis to obtain the characteristics of the reflectarray design. Then, an eight-zone Fresnel reflectarray, in which a phase difference of 45° separated each zone, is analyzed and fabricated. The results of the FDTD analysis shows a 31.6 dBi antenna gain at 78.5 GHz. Finally, the designed reflectarray is fabricated using a 3D printer. Measurements indicate that the achieved 30.4 dBi antenna gain nearly equaled the FDTD analysis value of 31.6 dBi at 78.5 GHz.