The emerging applications in the 5th generation (5G) network, such as industrial control system and Machine-to-Machine (M2M) communication require high reliability and low latency communication at the same time. The retransmission scheme is one of the practical approaches to increase system reliability when other diversity techniques are avoided due to hardware complexity or significant transmission delay. In order to address such problems, in this paper, we propose a fast yet reliable retransmission scheme. The proposed retransmission scheme leverages the frequency diversity through simple channel selectivity. The channel selectivity is carried out by employing low complexity subcarrier allocation for selecting other channels in Orthogonal Frequency Division Multiplexing (OFDM) transmission. The evaluation results show that the proposed retransmission method outperforms the conventional scheme. The proposed method can reduce the number of retransmission by up to 30%, corresponding to a success rate of 0.9999 . In addition, it can be employed in an industrial Wireless Local Area Network (iWLAN) system with a large number of users. The achievable control duration is around 52-63 μs, an improvement of approximately 36% compared to the conventional system.

This paper proposes train radio communications for high-speed railways to achieve the following three items compared with the conventional systems: 1) higher frequency efficiency; 2) faster mobile speed; 3) larger cell radius. Comparing with Global System for Mobile Communications-Railway (GSM-R) and Terrestrial Trunked Radio (TETRA) in European train radio communications, although the conventional Japanese train radio communications have excellent frequency efficiency and communication quality, they have weakness on mobile speed and cell radius. This paper proposes train radio communications, which can achieve the same levels as GSM-R and TETRA for the items 2), and 3), maintaining the advantages of the conventional Japanese systems for the item 1). Finally, computer simulation results show the proposed systems can extend the cell radius of the base station comparable to GSM-R and TETRA at mobile speed of 300km/h while maintaining the same level of communication quality and frequency efficiency as the conventional Japanese train radio communications.

This paper discusses experimental and field evaluation results of differential multiple single carrier (MSC) modulation schemes for underwater acoustic communications (UWACs). UWACs suffer from severe doubly-selective channels and inter-carrier interference due to non-uniform frequency offset. In addition, assuming image data communications, UWACs have to improve frequency efficiency. In order to solve these issues, this paper proposes a wireless transmission scheme, which employ differential MSC modulation schemes. Next, this paper investigates parameters for 8kbps-UWACs and 64kbps-UWACs aiming at wireless control of autonomous underwater vehicle and image data communications, respectively. Finally, two experimental and field evaluation results in acoustic experimental pool and shallow-sea environment confirm that the UWAC MODEMs have excellent performance on severe doubly-selective channels.

Foreign-exchange (FX) brokers have some risk factors such as price fluctuation risk and latency of data transmission. To reduce these risks in FX brokerage services, we propose a short-term prediction of exchange rates quoted by counter-party banks. We consider that these exchange rates are generated by the knowledge of each counter-party bank, and therefore try to extract the knowledge by using a machine learning method. As a result, we could predict the direction of exchange rates with a prediction accuracy of about 80% if the prediction interval is 100[ms]. Furthermore, by integrating the knowledge of counterparty banks by the ensemble learning, we could improve not only prediction accuracy but also profitability of foreign-exchange brokers. These improvements can be considered as an effect of collective knowledge based on the diversity prediction theorem, but this effect might be limited by extremely short-term prediction of foreign-exchange rates after 100[ms]~200[ms].

The strong and weak interactions in quantum theory represent the physical phenomena that bind quanta. We attempt to apply impedance matching that represents the connection of circuit elements in analog circuit theory to these interactions. The interactions in quantum theory are related to the phase in gauge theory. The phase can be given to the connected state of circuit elements using cascade matrices, which can determine the phase of circuits. We show that asymmetric LC ladder circuits are suitable for representing the interactions of quanta in terms of the phase as well as the quantized wave equations. We also show that the equivalent circuits for the connection of quarks and gluons can be represented as LC ladder circuits.