Waveform distortion due to reflections in high-speed digital signaling is a classical issue of the signal integrity especially for the multi-drop transmission system. In general, the reflection characteristics and improvement measures of the multi-drop transmission strongly depend on the topology of the system in question, such as bus-configuration, star, ring, and so on. In this paper, we discuss a method of RCL (Reflection Compensation Line), formally reported in  as a reflection cancelling scheme, that can be applied to the bus-type multi-drop transmission system, whose length of main bus segments and stub lines are all isometric. Assuming practical application of our RCL technique to high-speed digital signaling, data rate of over 10Gbps, the optimal set of transmission parameters are deduced by means of numerical optimization algorithm, and the performance of the RCL is discussed.
In this paper, we investigate the signal bit error rate (BER) characteristics of a vehicle-borne weighted polarization maximum ratio combining adaptive array antenna for secure communications. The array comprises orthogonally arranged dipole elements, which are combined using weight functions determined by the cross-polarization power ratio in the propagation environment and the angle of inclination of the antenna. The experimental results show that the required signal-to-noise ratio for the proposed antenna to achieve the prescribed BER is lower than that for a conventional dipole array even in vehicle rollover accidents.
We demonstrated experimentally probabilistic shaping (PS) with a 5% increase in symbol rate for 400 Gb/s 16-ary quadrature amplitude modulation. Such a shallow PS enables significant improvement of the theoretical performance with limited incremental power consumption, peak-to-average power ratio (PAPR), and kurtosis. The PS signal was transmitted over a typical terrestrial link at a 0.8 dB larger Q margin than with uniform signaling. There were no excessive penalties such as transceiver and fiber nonlinearities because of the limited PAPR and kurtosis. Throughout an 8-hour nonlinear transmission test, there was no significant performance variation, and no residual errors after forward error correction decoding.
A Low-Density Code Structure (LDC) spread transmission for Non-Orthogonal Multiple Access (NOMA) system based on modified combinatorial design is studied in this letter. To mitigate the multiuser access interference, the NOMA frequently needs complicated signal processing, which is difficult to be applied in practical scenarios. One potential solution is to design sparse multiple access structure for leveraging detection complexity. The sparse pattern of Balanced Incomplete Block Designs (BIBDs) provide an inherent sparse mapping for this system allowing simultaneous and more efficient usage of given. It is also able to form a bijection mapping with lower complexity and be reconstrued to achieve further sparsity. This new scheme allows a larger number of users transmitting in the downlink.
In this paper, we derive a general non-vanishing expression of signal to inference and noise ratio (SINR) considering hybrid relaying processing (HRP) in a massive multiple-input multiple-output (MIMO) half-duplex amplify-and-forward (AF) two-way relaying networks with multi-pair users. Then the general asymptotic values of system spectral efficiency (SSE) and system energy efficiency (SEE) can be compared under different power scaling schemes, when the relaying antenna number M increases sufficiently large. Then we achieve the optimal power scaling scheme of SSE and SEE with the considerably large M. Finally, all comparison analyses of SSE and SEE are confirmed by simulation results.
A continuous formulation of a neural network based on a partial differential equation (PDE) is proposed. By assuming binary classification with cross-entropy, we formulate the neural network as an optimal control problem of a PDE. The existence of the optimal solution is theoretically proved. By finding the solution and optimal control in Hilbert spaces, we provide the explicit representation of the Fréchet derivative of the cost function at the solution. We also propose a gradient-descent-based algorithm that delivers a (sub-) optimal control.
In recent years, the finite-difference time-domain (FDTD) method has been widely employed for analyzing various electromagnetic problems, including low-frequency problems. It provides accurate results in most cases, but it requires relatively long calculation time for slow convergence problems, such as array antennas. For this reason, the autoregressive moving average (ARMA) model has been applied to the FDTD analysis to reduce calculation time. However, it has not been applied to FDTD radiation pattern analysis because the radiation patterns calculation requires multi-dimensional (time and space) data. In this letter, two-dimensional ARMA is applied to FDTD radiation pattern analysis to reduce the calculation time. We confirm effectiveness of the method by calculating the radiation pattern of Yagi-Uda antenna.
In recent years, a capsule endoscopy has been used as a medical device to diagnose small intestines painlessly. Wireless power transmission (WPT) to the capsule endoscopy has been studied. The efficiency of WPT can be improved by using location information of the capsule. In the previous research, a localization method for the WPT was developed in simulation. In the present paper, we evaluated the localization algorithm developed in the previous research by measurement, so that the effectiveness of the algorithm was demonstrated.
We present a theoretical model and propose a technique based on this model for measuring the mode field diameter, relative-index difference, and chromatic dispersion along a randomly-coupled multi-core fiber using an optical time domain reflectometer. Experimental investigations demonstrate the feasibility of the technique.
In our laboratory, we study “area estimation” by Finger Printing for indoor commercial facilities and buildings. We study a method for updating DBs with user-acquired AP information. There is a problem of lowering the estimation accuracy due to the bias of the updated DBs. In order to solve this problem, we proposed a method to create a large distribution by mixing multiple databases.
Deploying a large number of spatially distributed antennas (DAs) is a promising solution to improve the link capacity while keeping the coverage of 5G systems which utilize a high frequency band. And clustering is a promising method to mitigate the extremely high computational complexity due to a large-scale multi-user multiple-input multiple-output (MU-MIMO). User-clustering and antenna-clustering are two clustering approaches. In this paper, we utilize K-means algorithm in clustering and propose two cluster member assignment (CMA) methods to assign corresponding DAs or users into user-clusters or antenna-clusters. Then, we evaluate the achievable downlink and uplink capacities through computer simulation to find the optimum combination of clustering approach and CMA.
This paper proposes a subjective assessment method for video quality and sense of presence for 360° videos. Since it is necessary to view 360° videos with a wide field of view, we adopted a subjective assessment method that allows repeated viewing of 10 s long videos. First, by analysis of the subject’s observation behavior (i.e., head movement), it was clarified that the appropriate number of observation repetitions was 2. The relationship between the video quality and the sense of presence was then quantified using the proposed method. Finally, we determined the number of subjects necessary to derive stable evaluation results.
Multi-user MIMO multiplexing and spatial diversity are indispensable techniques to improve the link capacity in a fading environment. In this paper, user-wise joint transmit-receive diversity (JTRD) is proposed for zero-forcing (ZF)-based multi-user MIMO. Two types of user-wise JTRD are considered and the design of ZF precoder/postcoder, which takes into account the role of JTRD, is presented. The achievable received signal-to-noise ratio (SNR) is analyzed and a simple but useful expression for the received SNR is derived for a 2-user case. The link capacity achievable by ZF-based multi-user MIMO coordinated with user-wise JTRD in an uncorrelated Rayleigh fading environment is evaluated by Monte-Carlo numerical computation and is compared with ZF-based multi-user MIMO coordinated with user-wise maximal-ratio transmitting and combining diversity (MRTCD).