Abstract Statistical methods have been widely misused and misinterpreted in various scientific fields, raising significant concerns about the integrity of scientific research. To mitigate this problem, we propose a tool-assisted method for formally specifying and automatically verifying the correctness of statistical programs. In this method, programmers are required to annotate the source code of the statistical programs with the requirements for these methods. Through this annotation, they are reminded to check the requirements for statistical methods, including those that cannot be formally verified, such as the distribution of the unknown true population. Our software tool automatically checks whether programmers have properly specified the requirements for the statistical methods, thereby identifying any missing requirements that need to be addressed. This tool is implemented using the Why3 platform to verify the correctness of OCaml programs that conduct statistical hypothesis testing. We demonstrate how can be used to avoid common errors in various statistical hypothesis testing programs.

This paper proposes an extension of CNN-based demodulation in image sensor-based visible light communication from single-color to multi-color processing. Conventional CNN-based demodulation methods mainly focus on a single color space, limiting the utilization of chromatic information. In this study, we introduce a multiplexed chromatic modulation by incorporating both Cr and Cb components into the demodulation process. To evaluate the proposed method, we conducted fundamental experiments using 24 different monochromatic backgrounds. The performance of our approach was compared with the conventional cell averaging method in terms of bit error rate (BER). Experimental results demonstrate that the proposed CNN-based demodulation with multi-color processing achieves a lower BER than conventional methods, indicating improved communication quality in image sensor-based visible light communication.

Image overlay uplink screen camera communication has been studied, which consists of a small screen transmitter with LED backlight modulation and a rolling shutter camera receiver, allowing the user to transmit data while displaying the received image on the screen. This study investigates a method that enables data demodulation even when the transmitter screen is captured only in a part of the received image as the transmitter moves. To detect only the screen captured as part of the received image and further detect the preamble, threshold decision, object detection deep learning (DNN), and correlation coefficients are compared. It has been revealed that object detection DNN is suitable for screen detection, while correlation coefficients are suitable for preamble detection.

To realize high-throughput optical wireless communication (OWC) indoors using a photodiode (PD) receiver, the receiver that mechanically tracks an LED transmitter is effective. The receiver consists of a photodiode with a narrow field of view (FOV) and a camera that captures the movement of the LED transmitter. In this study, a rolling shutter (RS) camera is used to identify and locate the transmitter in real time by an object detection algorithm, and the receiver mechanically tracks the transmitter using two-axis motors. RS camera uses YOLOv5 to detect the location of the transmitter by identifying low-rate modulation in the preamble. A data rate of 1Mbps is achieved indoors between an LED transmitter moving at walking speed and a tracking PD receiver.

This study focuses on visible light communications using a high-speed display and rolling-shutter camera of a smartphone. We aim to achieve high-quality communication imperceptible to the human eye through the high-speed display. The capture rate of an image sensor is generally slow. Then, the image sensor cannot obtain some parts of a transmitted data image because of the high-speed display rate. We employ the rolling shutter camera that reads pixels row by row and propose a receiving scheme in which the camera obtains some transmitted data images in a captured image. The proposed scheme can acquire transmitted data, even if the display rate is higher than the capture rate. We experimentally evaluate the proposed scheme in terms of the quality of the visual information and the communication quality to clarify its superiority.

Low-Iuminance spatial division multiplexing (SDM) with spatial 4-pulse position modulation (4-PPM) correlation is demonstrated to realize indoor uplink screen to camera communication using a smartphone screen and a video camera. Spatial 4-PPM correlation enables SDM transmission even when pixel values on the low-luminance screen vary due to ambient light. It achieves low bit error rate without learning thresholds using known SDM images. In addition, combining spatial 4-PPM and inverted 4-PPM improve the data rate. Difference in the average pixel value of each cell is used to distinguish between 4-PPM and inverted 4-PPM cells.

In previous study for uplink optical wireless communication from a smartphone screen to an indoor telephoto camera, low-luminance space division multiplexing (SDM) using spatial 4 pulse position modulation (4PPM) was demonstrated without threshold learning. In this study, to increase the data rate further, low-luminance wavelength division multiplexing (WDM)/SDM is demonstrated by spatial 4PPM correlation and successive interference cancellation (SIC) without threshold learning. WDM/SDM causes both spatial inter-symbol interference (ISI) and inter-wavelength ISI. Even under the condition of spatial ISI caused by SDM, spatial4PPM with SIC can remove inter-wavelength ISI caused by WDM. Furthermore, it is also demonstrated that low-luminance WDM/SDM using spatial 4PPM with SIC enhances physical layer security at wide angles.

It is expected that IEEE 802.11ad is used as intra-vehicle communications for high-speed transmission. Currently, since motion detection by frequency modulated continuous wave (FMCW) signals in mmW has been available, issues on interference between IEEE 802.11ad and FMCW signals have been raised. To solve the issues, an interference mitigation method applicable into IEEE 802.11ad against FMCW signals has been proposed. In this method, FMCW signals are detected by summation of the energy in frequency domain of interfered received signals. Interference suppression is achieved by nulling the frequencies where it is determined that FMCW signals are detected. The method does not require any changes of IEEE 802.11ad specifications. Simulation results show that significant improvement on BER has been achieved by introducing the method over SIR range from 0 dB to 8 dB. Experiment on the method has been conducted to evaluate performance of the method in a vehicle. The results obtained by the experiment have shown that the method successfully suppresses FMCW signals.

In a large-scale indoor environment such as an industrial one, a multiple-input-multiple-output optical wireless communication (MIMO-OWC) system represents a flexible and easy-to-deploy solution to achieve point-to-point long-distance and high-speed data transmission. The majority of imaging MIMO-OWC systems have mainly targeted high data rate communication over short distances, not exceeding 10 m. In this work, on the contrary, we focus on longer-distance links providing high-speed transmission data rate. For this purpose, we propose an imaging MIMO-OWC system that features an improved optical modulator array with a one-dimensional element arrangement, and a new imaging receiver using long focal length lenses placed in front of the receiving photo-detector array. The performance of the proposed system is then experimentally evaluated. The obtained results show that the measured MIMO channel matrices have sparse patterns, which means that the elements not corresponding to the emitted beams are nearly zero. We successfully demonstrate the transmission at a high data rate of 100 Mbps over a long distance of 50 m. This result surpasses the achieved distance corresponding to the conventional MIMO-OWC system using an independent optical system for each light-receiving element. Consequently, the experimental results confirm that our proposed system has the potential for higher speed with longer distances.

This study considers a power line communication (PLC) based multi-machine feedback control system. In PLC, channel characteristics have cyclostationary features synchronous to the mains voltage, and based on the multiple access schemes, the communication performance significantly differs. In this situation, previous work has evaluated the system which uses time division multiple access (TDMA) and found that the controlled quality of each machine becomes unequal. This manuscript thus proposes employing synchronous code division multiple access (SCDMA) and compares the control performance with the system using TDMA. As a result, using the proposed SCDMA, it is observed that all the machines achieve the same control quality, and the control quality itself is better than that with TDMA when the signals are much stronger than noise.

In this paper, we examine wireless relay networks using drones as emergency communication systems during large-scale disasters. Flying drones are inclined in the direction of their movement. This inclination causes a reduction in the received power when taking into account the effects of antenna directivity in the vertical plane and the polarization plane deviation. In this paper, we model the relationship between the inclination and flying speed of drones and derive the received power taking into account the inclination. We evaluate the influence of the drone's inclination on the delay time through simulation. The results indicate that the speed of the drone that achieves the shortest delay time is dependent on the number of drones.

For efficient collection of the leaf temperature data over the entire farm, we simultaneously use a drone in the sky and sensor nodes on the ground that are both equipped with infrared thermometers. In this study, we propose a communication protocol for wireless sensor network (WSN). The preliminary results of a prototype experiment show that the measurements are sufficiently synchronized for collecting useful leaf temperature data.

For large-scale disasters, it is important to ensure communications to confirm the information about safety and disaster situation. Then, this paper focuses on an emergency communication system using drones. In this system, an important issue is to shorten the delay time of transmitting information. Since delay time depends highly on a flight scheme of the drones, we propose two flight schemes: a rebounding-flight scheme and a common-flight-path scheme. Moreover, we consider breaks of drones due to their battery exhaustion because it is impossible for the drones to fly permanently. We evaluate the delay time with and without drones' breaks for the proposed flight schemes. Our results show that the proposed flight schemes are effective to reduce the delay time even if the drones' breaks are considered.

In this paper, a cross-layer design for communication and control layers for wireless feedback control systems is considered, and an optimized receiver design for state feedback is proposed. The proposed receiver is designed on the basis of a maximum à posteriori probability decision and utilizes the control layer's information, namely, the estimated state information of a Kalman filter-based state observer, as the à priori information of the transmitted state feedback. In addition, the proposed receiver provides the error covariance information of the received state feedback for the control layer. The recursive structure of the receiver and state observer is simple and suitable for the feedback control loop. The improvement in the channel error probability is supported by the control accuracy and vice versa. Numerical results show that the proposed receiver can effectively reduce the number of channel errors in the received state feedback and improve the control performance.

Packet losses degrade the performance of wireless feedback control systems. The use of channel coding may decrease the packet loss rate; however, its redundancy decreases the packet transmission rate under the same bit rate and thus degrades the control quality. In this paper, we propose a variable length channel coding scheme for state feedback without decreasing the packet transmission rate. The proposed scheme reduces the number of state variables to be fed back and instead adds redundant bits of channel coding on the basis of state estimation error. We show that the proposed scheme improves the control quality without decreasing the packet transmission rate.

In wireless feedback control systems with multiple plants, state information and control information are sent over a shared communication channel. The IEEE 802.15.4 beaconenabled mode has a contention access period (CAP) and a contention free period (CFP). In the CAP, carrier sense multiple access/collision avoidance (CSMA/CA) is used. In the CFP, time division multiple access (TDMA) is used. This paper considers wireless control over the IEEE 802.15.4 beacon-enabled mode and discusses how to use the CAP and the CFP. We propose two schemes that assign the plants to the CAP and the CFP; one is based on communication success/failure and the other is based on control error between state information and the target value. We show that the proposed assignment schemes improve the quality of an overall plant control compared with random assignment. In addition, the scheme based on the control layer achieves better control quality than that based on the communication layer.

Multiple access communication is required to control multiple plants via wireless communication channels. This study discusses time division multiple access (TDMA) schemes to improve control quality for feedback control of multiple plants. To improve the control quality, time slot allocation of the TDMA should be based on information of the control layer, i.e., control objective and plant's state. In wireless control of multiple plants, there are different target values for the plants and different packet losses on communication channels. This leads to different tracking performances among the controlled plants. Therefore, a flexible time slot allocation scheme that considers the tracking performances is required. In this paper, we propose time slot allocation schemes to minimize predicted tracking error on the controlled plants. One minimizes the predicted tracking error in all time slots, and the other sequentially minimizes that in each time slot. Numerical results show that the proposed schemes can improve an overall control quality under packet loss.

In this paper, we consider the reduction of the amount of transmission data in wireless feedback control systems. Because available frequency bandwidth is limited in wireless communication, the amount of control data that can be transmitted in a sampling period is limited. A source coding scheme that has variable length codes can efficiently reduce the amount of transmission data; however, a variation in packet loss rate due to the variable code length highly affects the control quality. If control data are assigned to long codes, packet loss rate of the data becomes large. Therefore, the control quality deteriorates if control data of high importance are assigned to long codes. From this view point, we propose a source coding scheme that considers the importance of control data. We evaluate the performance of the proposed coding scheme under a data-rate constraint and show that the proposed coding suppresses the deterioration of the control quality and reduces the amount of transmission control data.

This paper considers H∞control for wireless networked control systems with data packet loss. In wireless networked control systems, the control performance deteriorates due to packet loss. Therefore, packet loss is one of major weakness in the wireless networked control systems. To overcome this weakness, this paper proposes a new control design that considers the influence of packet loss as a disturbance. Our new control design belongs to the H∞control design and can reduce the influence of disturbances acting on the controlled object. Numerical examples show that the proposed H∞control design can more effectively reduce control performance deterioration due to packet loss. This paper provides not only the proposal of the new control design but also control performance comparisons of the proposed control design and the Linear Quadratic (LQ) control design. Numerical examples show that the control performance of the proposed H∞control design is better than that of the LQ control design.

Digital signage, which is advertising media using a liquid crystal display (LCD), is increasing in popularity. One possible application is wireless communications between digital signage and viewers. We focus on image-sensor-based visible light communication (VLC). Image-sensor-based VLC requires only an image sensor (IS), which is common equipment in smart phones. In the proposed method, an information signal is displayed on LCD. However, embedding the information signal into an advertisement may decrease the quality. We propose blue color difference modulation to make such signals imperceptible. We implemented a VLC system between digital signage and IS to demonstrate, the effectiveness of the proposed modulation in a real environment.

We focus on MIMO mesh networks, which consist of wireless nodes supporting MIMO transmission. Communication quality of a wireless link using MIMO spatial streams is sensitive to change in its channel, and performance will be unstable. For stable operation of MIMO mesh networks, a method analyzing the MIMO mesh networks is needed. In this paper, we aim to propose an analyzing method of MIMO mesh networks. We measure the time variation of throughput and Received Signal Strength Indicator (RSSI) as feature values of a link in our testbed of the MIMO mesh network, and analyze the measurement results by using Self-Organizing Map. As a result, we confirm that it is possible to find the links that have correlation with time variation of throughput and RSSI by applying SOM to the measured feature values.

Our goal is the improvement of the data collection in solar-powered wireless sensor networks. One of the methods to improve the data collection is cooperative transmission by which a node relays data from a source node to a base station. However, the cooperative transmission is not enough to prevent the data collection performance from the decline in low power generation, such as in a cloudy day and at night. We tackled this problem by introducing a repeater role to same nodes, which only relays data from the other nodes without transmitting its own data. Our proposal improves the data collection performance in the low power generation. Numerical examples compare and show the effectiveness of the conventional method and three assignment methods of the repeater role: one is to assign the repeater role to some nodes fixed in place around the farthest nodes, one is to assign the repeater role uniformly randomly to some nodes, and another is to assign the repeater role to some nodes that do not have sufficient battery levels.

An emergency node-combined wireless network that uses balloons, electric vehicles, and unmanned aerial vehicles (UAVs) was proposed. We discuss the construction and specific issues of this network. The communication area is evaluated by changing the node elevation. In this network, the elevations of balloon and UAV nodes vary, and the communication area changes with elevation. In addition, the network may be temporarily disconnected by changes of the communication area. To solve this problem, we employ a delay-tolerant network technique. We evaluate the number of nodes and node density according to the desired application and regional characteristics.

In this paper, we propose area transmission efficiency to evaluate the performance of single-user multiple-input multiple-output (SU-MIMO) and multi-user MIMO (MU-MIMO) in wireless mesh networks (WMNs). The area transmission efficiency is the number of packets that can be transmitted per unit time and per area, and is calculated by considering the multiplexing effect of MIMO and the density of transmitting nodes. The performance of SU-MIMO and MU-MIMO is evaluated and compared in term of the area transmission efficiency in WMNs. As a result, the area transmission efficiency of MU-MIMO can be superior to that of SU-MIMO when the number of queueing packets is small. Conversely, this relationship is reversed when the number of queueing packets is enough large. In addition, by selecting the transmission packets so as to reduce the number of receiving nodes, MU-MIMO is always superior to SU-MIMO.

In wireless feedback control systems, reducing packet loss is critical. The use of channel coding may decrease such packet loss; however, redundancy in channel coding also decreases the packet transmission rate although the bit rate remains the same. Thus, control systems are highly affected by disturbances. To improve control system quality, channel coding should be adaptively employed on the basis of packet loss and disturbances. Herein, an on-off error control coding scheme based on the communication and control layers is proposed. In this scheme, channel coding is adaptively used to minimize tracking errors in a controlled plant. Results demonstrate that the proposed on-off error control coding scheme improves the control system's reference tracking performance compared with that when using a fixed-rate coding scheme.

Packet loss is the major weakness of wireless feedback control systems. In this paper, we discuss the improvement of the control quality of wireless feedback control systems with Forward Error Correction (FEC) coding. If FEC coding is used, packet losses may decrease. But its redundancy decreases the packet transmission rate under the same bit rate, so that the control quality will be worse. Therefore, we propose an adaptive coding scheme to improve the control quality. In this scheme, FEC coding is used adaptively based on a predicted state of the controlled plant. Our proposal is the first approach in the field of adaptive channel coding for wireless feedback control systems because this scheme adapts channel coding to the quality of the control layer (application layer). In this paper, we show that the proposed adaptive coding scheme improves the control quality more than that of the fixed rate coding in Rayleigh fading channels.

In wireless feedback control systems, it is important how to reduce packet losses. If channel coding is used, packet losses may decrease. But its redundancy decreases the packet transmission rate under the same bit rate, so that disturbances in the controlled plant may deteriorate the quality of the control system. To improve the quality of the control system, the channel coding should be used adaptively based on packet losses and disturbances. In this paper, we propose an adaptive coding scheme based on the quality of the communication layer and the control (application) layer. In this scheme, the channel coding is used adaptively based on a predicted state of the controlled plant under a packet loss rate. We show that the proposed adaptive coding improves the control quality compared with that of the fixed rate coding.

This paper proposes a joint coding scheme for information advertisement in wireless mesh networks. Random network coding is a technique that can mitigate the effect of a broadcast storm problem. However, it cannot correct bit errors, and it should forward more and more packets to recover bit errors. On the other hand, multi-route coding was proposed to reduce bit errors on wireless channels. This coding scheme can obtain a diversity gain by transmitting multiple coded packets on multiple routes. This paper proposes the joint coding scheme by using random network and multi-route coding to reduce the effect of the broadcast storm problem and bit errors. We evaluate the performance of the proposed coding scheme by simulation. The results show that the proposed scheme improves the transmission delay and packet delivery failure ratio compared with the conventional schemes.

This paper introduces a Visible Light Communication (VLC) system using an LED sign panel, which allows the provision of broadcast-type information in public spaces. This system provides an additional function to an LED advertisement panel; the panel not only displays an advertisement, but also transmits wirelessly to other devices. We suggest its use in benefit of the visually impaired. They can obtain local information by using this system, named i-LightHouse (i-LH). For this purpose, i-LH transmits a long-range navigation signal to direct users to the LED sign panel and a short-range signal to download content information to the users' devices. We propose its modulation scheme which can multiplex the navigation and content information at the same time. In this system, the interruption by a passerby and ambient lights may degrade the communication performance. On these issues, we propose an error correcting method and a filter to mitigate the interference of them and evaluate the effectiveness.

Our goal is the improvement of the node activity rate in solar-powered wireless sensor networks. We consider the application of a cooperative transmission scheme that uses a relay node when a node sends data to reduce the consumption of energy of the entire network. However, if we do not consider the variations in energy harvesting, the node activity rate declines during nighttime. In this paper, we smooth out the day-and-night node activity rate variations by introducing the new inactive node reactivation condition and achieve the required high node activity rate.

In sensor networks, because of densely deployment of sensor nodes, sensing area of each sensor node is overlapped with each other and its observed data sequence is correlated. The joint decoding scheme that uses the correlation between the observed data sequences can reduce bit errors in the wireless channel. In this paper, we extend the joint decoding to the case of more than two-hop transmission. For such extension, selection of fusion scheme is very important issue. If the global fusion scheme is employed and the observed data sequence of each sensor node is transmitted on an independent route, route diversity effect could be obtained by using the correlation between observed data sequences. We compare the bit error rate performance of local and global fusion schemes and clarify the route diversity effect