In this paper, we investigate a signal detection technique for wireless nanosensor communications in THz band. Due to a limitation of battery size in nanosensor terminal, the wireless nanosensor communication is highly energy-constrained. Therefore, on-off-keying (OOK) modulation with an energy efficient prefix code is a promising approach for achieving energy efficient communications. Energy detector (ED) is employed for symbol detection since it is a simple technique. We propose an Enhancing ED (EED) with adaptive threshold setting that is suitable for THz usage. We evaluated the EED in THz channel in which an effect of molecular absorption is considered. The numerical evaluation showed the advantages of the proposed scheme.

This paper focuses on a spectrum sharing cellular system primarily used by noncellular, stand-alone wireless systems. Geographically deployed base stations (BSs) that cover the service area to continuously provide spectrum sharing act as a secondary system, where the sharing condition is provided to the total interference power at the primary system. In this case, how much transmission power from each BS is allowed on the shared spectrum? By applying the propagation model originally used to evaluate cellular systems, this paper numerically and theoretically reveals the relation between the protection distance (PD) and allowable transmission power.

Local 5G system is widely used for industrial application, it is important to ensure redundancy to recover quickly in the event of failure for providing highly reliable services. On the other hand, the cost reduction of the mobile system becomes a problem in terms of having functions only for the cases of failure. We propose cost-effective redundant mobile fronthaul (MFH) system that uses only short-reach transceivers for the first time. Numerical simulations indicate that this system can provide 20-km redundant-line transmission with 8% redundancy by Reed-Solomon coding function.

We proposed sandwich structure as a wireless power transmission system. The structure is more robust than a conventional type, where a pair of transmission receiving coils is employed, because in the present structure two receiving coils were placed between two transmission coils. The analysis revealed that the leakage magnetic field of the structure depends on the direction of currents flowing in the coils. In this paper, we report the intensity of the leakage magnetic field and the radiation pattern obtained for measurement results associated with an oscillation frequency of 85kHz. The results showed that the leakage magnetic field was suppressed when the coils are coupled in different directions.

This paper proposes 32kbps terrestrial acoustic communications (TRACs) and confirms their effectiveness by means of experimental results. TRACs suffer from low transmission information bit rate due to their narrow frequency band-width and severe double selectivity due to slow propagation speed of sound. The proposed TRACs have the following three features: 1) they employ single carrier block transmission with frequency domain equalization; 2) they compensate distortion of frequency response due to a speaker thanks to transmit precoding; 3) they improve tracking capability of mobile environments thanks to channel interpolation. Finally, experimental results confirm that the proposed TRACs can achieve 32kbps transmission information bit rate in hand-held conditions.

Fog computing provides various new services with distributing Internet of Things (IoT) data. To distribute IoT data, we apply the publish/subscribe messaging model to a fog computing system. However, the user’s private data may be distributed without his or her permission. In this paper, we propose using Ticket-based Access Control to distribute IoT data. It enables detailed control over a user’s data access. Because we need to understand the performance of the ticket authentication and authorization infrastructure, we simulate it. As a result, the average processing delay time is nearly the same when the number of authentication and authorization channels is 5 and 10. In addition, the average processing delay time is reduced by approximately 61% when compared to the case with one channel.

In vehicle ad hoc networks (VANETs) in urban environments, the presence of many obstacles causes shadowing and interference with radio wave propagation. Despite this, most of the existing opportunistic routing protocols do not consider shadowing in their simulations. In this study, we propose a new opportunistic routing protocol that minimizes the effect of shadowing by actively selecting street intersection nodes as relay nodes. Additionally, we propose a new opportunistic recovery strategy when the local optimum situation occurs. Simulation results show that the proposed scheme improves the packet delivery ratio and overhead.

Research and development on the Internet of Things (IoT) has been promoted actively. However, when a large number of tiny data blocks are transferred over the Internet conventionally, some critical problems such as large overheads for legacy protocols and their processing power for communication equipment are highlighted. To solve these problems, MQTT has been discussed actively in academic societies and standardization organizations. However, it is not reasonable to use the MQTT to transfer large files, e.g., video files from surveillance footage. This paper proposes new mechanisms for cooperation between MQTT and FTP for data blocks of any size. This paper also reports the reasonability of this mechanism through prototyping.