Optical communication links between space and ground will be disconnected by cloud blockages only based on optical site diversity, because of cloud blockages randomly changing in time and space. To continue the operation, cloud avoidance network with cloud observation from space and ground and network controls are necessary, however, optical ground stations will be often placed at remote sites without ground wired network. To realize continuous operation under such an environment, our cloud avoidance network is designed to extract and handle only minimum and meaningful information of clouds. The network experiment has been conducted on ground wired network and the operation possibility has been also verified on ground wireless network. In this paper, first, overview of our cloud avoidance network and structures of each equipment on the network, Next, operation possibility of our cloud avoidance network, even based on a low rate communication environment because of the unique system feature of handling only information required for the cloud avoidance network and then, the operation possibility based on the mobile wireless router verified through our experiment are presented.

A circular polarized 4x4 element 4-port antenna in the 300 GHz band was designed and fabricated. Antenna gain of more than 10 dBic and axial ratio of less than 3 dB were obtained at 285.12 GHz to 289.44 GHz, which are ch 16 and ch 17 of IEEE 802.15.3d. If the power of the four ports were ideally combined, the antenna gain would increase by 6 dB to 16 dBic. A lens was designed for the circularly polarized 4x4 element 4-port antenna. The focal length of the lens was 100 mm and lens radius is 35 mm. An antenna gain of 40 dBic was calculated using the lens. Placing the 4x4 element 4-port antenna at the focal length of the lens would provide maximum gain, but no beam steering by phase controle. Placing the antenna closer than the focal length would lower the antenna gain but allow beam steering by phase controle. The antenna gain and beam tilt angle were calculated for different distances between the lens and the 4x4 element 4-port antenna. A lens antenna with a lens height of 70 mm was assembled and beam steering was measured.

This paper proposes a priority control method utilizing channel reservation for high-priority access points (APs) in IEEE 802.11 wireless LANs. The proposed algorithms are based on a network-controlled channel allocation scheme called RATOP. Computer simulation results demonstrated the positive effect of the proposed scheme on average and minimum throughput in a large area. This paper also proposes an enhanced algorithm that releases reserved channels to improve throughput. An estimation method based on theoretical analysis provides the number of required reserved channels for a given throughput ratio of high-priority APs to low-priority APs.

In this letter, we propose a distance estimation method that accounts for molecular absorption (MA) delay in the THz frequency band. In radio propagation, the time of arrival (TOA) at the receiver from the transmitter is typically determined by the propagation delay, which is the distance divided by the speed of light in a line-of-sight (LoS) scenario. However, in THz the observable TOA could exceed the propagation delay due to an additional delay denoted by MA delay caused by molecular absorption. This MA delay introduces a biased estimate into conventional distance estimations. In this letter, a novel distance estimation method based on TOA incorporating MA delay is proposed. Numerical evaluations indicate that our proposed distance estimation method outperforms the conventional approach by accounting for the effects of MA delay.

This study develops an efficient measurement method for radiated emissions from automotive wire harnesses. The proposed measurement method utilizes the transfer function (TF) between a reference model and a simplified setup model. The results measured by the proposed method show high correlation with the reference measurements. In addition, the proposed method requires only one simple evaluation antenna for measurement, whereas the previously proposed TF method requires two antennas. We also attempted to eliminate dips in the measurement by using multiple measurement points for the simple evaluation antenna. In addition, the conventional TF method requires a 4-port VNA, but the proposed method can perform the measurement with a 2-port VNA. Therefore, the proposed method can reduce the cost of the measurement device.

The importance of privacy data protection has become increasingly prominent in the communication system. This paper presented a code division multiplexing(CDM)-based high-performance reversible data hiding(RDH) scheme for audio streams. In the scheme, plenty of private data are embedded into the audio stream through orthogonal spreading vectors without interfering with each other. Consequently, both private data and the original audio stream can be completely retrieved at the receiver side. At the same time, according to the orthogonality of spreading vectors, private data can be repeatedly embedded within an audio stream, thereby enhancing the capacity of data embedding to a great extent. As the mutual cancellation of most elements accrues during multiple-level data embedding, high perceptual quality for audio streams is obtained even with a large data-embedding payload. Extensive experimental results clearly show that the CDM-based audio RDH algorithm surpasses other state-of-the-art approaches in terms of data-embedding performance.

Proper antenna classification is required for complex systems including specific application and performance parameters such as resonance frequency, gain, and reflection coefficient because conventional mathematical decision-making models are not well-suited for evaluating these systems. This study proposes an antenna classification method based on Mamdani Fuzzy Inference System (FIS) to determine the appropriate antenna type for those requirements. The performance parameters of five types of antennas are evaluated to construct the configuration of the FIS. The FIS responses for unseen requirements verify the model’s performance showing its classification capability for new data.

In Vehicle-to-Everything (V2X) communication, vehicles transmit their information to surrounding vehicles and infrastructures for traffic safety and efficiency. However, vehicle anonymity in communications is important because location privacy is threatened when communications are eavesdropped and traced by malicious attackers. The method of periodically changing pseudonyms instead of using actual identification has been considered to provide anonymity. However, anonymity is significantly reduced when the number of vehicles changing pseudonyms simultaneously is insufficient, or when the vehicle trajectory is easily predictable. In this paper, we propose a cooperative pseudonym change scheme among vehicles with similar vehicle information extracted using Locality Sensitive Hashing (LSH), aiming to achieve higher vehicle anonymity. We analyze the anonymity of the proposed scheme in our mathematical model under limited circumstances and evaluate it in comparison with existing pseudonym change schemes.