Toshinori Kagawa

A UWB navigation system aided by sensor-based autonomous algorithm - Deployment and experiment in shopping mall

Demands for indoor-localization or indoor-navigation are increasing in many fields such as a marketing, shopping related industries, and anticrime application. At present, many types of technologies of indoor-localization or indoor-navigation are proposed. Some examples are those that use ultrasonic waves, Wi-Fi, or IR-UWB. In this paper, we focus on IR-UWB technology because of its great potential on high precision ranging, which is within several 10cm. However, a distance surveying fluctuation due to multipath effect may reduce the ranging precision. Multipath effect occur by smooth surface wall or glare items in indoor environment. To avoid multipath effect, we adopt sensor-based autonomous algorithm to assist UWB navigation. We deployed the overall navigation system in a shopping mall. Preliminary evaluation experiments were performed. As a result, the combined IR-UWB and autonomous algorithm system shows good navigation performance. The autonomous algorithm can reduce multipath effect. As compared with using only IR-UWB, the localization errors of applied autonomous algorithm decreased by 12.6% maximum.

C-band aircraft-to-ground (A2G) radio channel measurement for unmanned aircraft systems

This paper presents a summary of a measurement campaign on radio propagation channels in air-to-ground (A2G) links based on a usage scenario of unmanned aircraft services (UASs). In order to reveal their propagation characteristics, a measurement setup has been established that transmits a designed FMCW signal continuously from a small manned airplane with frequency bandwidth of 20 MHz at center frequency of 5060 MHz, and records the transmitted signals on ground as IQ waveforms by using a vector signal analyzer. Metrics on radio propagation characteristics including received signal strength (RSS) and channel impulse responses (CIRs) are obtained from the recorded data. The results on obtained RSS have shown that the trends of RSS change in the A2G links is expressed by free-space pathloss with a shadowing component encountered in mobile radio communications. Regarding the CIR in A2G links, it is observed that the radio propagation channels are expressed by a direct path and a ground reflection with scatter components; however, the direct path has margin of more than 20 dB in signal level against the other components.

Measurement of TCP and UDP performance over UAS relay networks

This paper presents a measurement setup for transport protocol of wireless relay network using a unmanned aircraft (UA). The UA can fly back and forth to ferry data from multiple ground based access points or ground stations (GSs) that are located in the distance without connection to the backbone due to the network disconnection caused by a large-scale disaster. In such disaster area, a demand of communications through the data including moving images, sounds and pieces of text increases. In this paper, we conduct the experimental measurement of the wireless relay network using UA and analyzes its behavior. In this experimental measurement, we evaluate the basic performance of TCP and UDP protocol based on usage scenes. The numerical results of its goodput and delay performance of will be shown in this paper.

Deployment of wireless mesh network using RSSI-based swarm robots

This paper proposes a novel method for deploying a wireless mesh network (WMN) using a group of swarm robots equipped with wireless transceivers. The proposed method uses the rough relative positions of the robots estimated by their Radio Signal Strength Indicators (RSSIs) to deploy the WMN. The employed algorithm consists of three parts, namely, (1) a fully distributed and dynamic role decision method among the robots, (2) an adaptive direction control using the time difference of the RSSIs, and (3) a narrow corridor for the robots to pass by movement function along walls. In our study, we evaluated the performances of the proposed deployment method and a conventional method in a real environment using 12 real robots for simple deployment, and 10 real robots for passing the narrow corridor. The results of the performed experiments showed that (1) the proposed method outperformed the conventional method with regard to the deployment time, power consumption, and the distances traveled by the robots, and (2) the movement function along the walls is effective while passing a narrow corridor unlike any other function.

Power provision scheme considering shadowing effect for two-dimensional communication systems

Two-dimensional communication system (2DCS) is a novel communication system which utilizes surface of sheet as communication medium. 2DCS provides wireless power supply as well as safely and high-speed data transmission to sensor devices. However, how to suppress the standing wave effect to a minimum is still an open issue for 2DCS. In this study, we explore how the power distribution on sheet medium changes by the location of input coupler, and then compose a scheme of the power provision with multiple single or compound couplers where shadowing effect is considered to suppress the standing wave effect. Through simulation experiments, we evaluate the performance of proposed scheme to improve the power provision efficiency over 2DCS.

Measurements on C-band air-to-air channel for coexistence among multiple unmanned aircraft systems

The measurements of air-to-air channel at C-band for coexistence among multiple unmanned aircraft (UA) systems are presented. The measurement campaign was performed to clarify the channel characteristic of the air-to-air radio propagation between small UAs. This paper presents a measurement result of our campaign on radio channel characteristics in C-band held in Japan in March 2016. The received signal consisting of the line-of-sight (LOS) component and multi-path component formed predominately by the single ground reflected wave was observed. These results can be used to model the statistical channel characteristics in order to assist an efficient sharing of the airspace with multiple UAs.

Meander mesh for two-dimensional wireless power

This paper proposes and evaluates a two-dimensional wireless transmission sheet with enhanced power transmission characteristics. The sheet consists of three layers: a conducting base layer, a dielectric microwave propagation layer, and a surface layer with a conducting mesh of meander lines. The inductive mesh surface supports evanescent radiation for wireless coupling at any point on the sheet. Radiation is fed into the sheet with a coaxial-waveguide coupler, and evanescent radiation is coupled out of the mesh surface with a capacitive coupler. The transmission characteristics at 2.45GHz evaluated by simulation show improvement of spatial uniformity and independence of coupler orientation compared to previous methods.

Demonstrations of combined small-UAV with satellite system for large-scale disaster

This paper describes overviews on two demonstration experiments of combinedxed- wing unmanned aircraft (UA) with satellite telecommunicatio systems for a large-scale disaster. Therst demonstration experiment is for video image delivery of disaster area even immediately after the occurrence of damage. To understand the situation in disaster area, the camera mounted on a small-UA is used in this demonstration experiment. The small-UA can photograph the moving picture during the circling, and the pictures are deliv- ered to non-isolated areas via ground station (GS) and satellite telecommunicatio system in an almost real time. The second demonstration is for providing temporal communication lines rapidly deployable to the isolated areas of disaster area until the recovery of ground infrastructures. To achieve temporal communication lines, small UA equipped with on- board transceiver (or repeater) is used to communicate with the GSs. The small UA-based wireless bridge system and satellite communication systems are serially concatenated to extend the network. This paper presents the successful results of these demonstrations and the effects of this combined system for large-scale disasters.

Energy-efficient construction algorithm for mobile mesh networks

In this paper, we propose an autonomous control method for the movement of distributed nodes in a mobile wireless mesh network. Our approach estimates the mutual position of nodes from the received signal strength indicator (RSSI), and constructs a network using a number of autonomous moving nodes to enable wireless communication. The proposed method controls the direction of node movement using two features: (1) the dynamic allocation of reference and moving nodes, and (2) the temporal variation of RSSI. To evaluate the effectiveness of our method, we employ three criteria. First, the area coverage ratio represents the degree of coverage of the target area with nodes such as sensors or communication devices. Second, the communication stability represents the latency and connectivity in the communication between nodes. Third, the energy consumption represents travel distance between nodes. Experimental results using a network simulator demonstrate that the proposed method achieves full area coverage using less than 3.8% of the energy required by the conventional method.

A self-localization estimation method with cooperating small robots Using camera positioning and movable landmarks

Recently, there has been extensive research on robot control using self-position estimation. Simultaneous Localization And Mapping (SLAM) is one approach to self-positioning estimation. In SLAM, robots use both autonomous position information from internal sensors and data from external landmarks. SLAM can improve the accuracy of position estimation with a large number of landmarks, but it involves a degree of uncertainty and has a high computational cost, because it requires detection and recognition of landmarks through image processing. To overcome this problem, we propose a new method involving the creation of maps and the measurement of position using two cooperating robots that serve as moving landmarks for each other. This makes it possible to solve problems of uncertainty and computational cost with two-dimensional markers, because a robot needs to find only a simple two-dimensional marker, rather than feature-points landmarks. In the proposed method, the robots have a two-dimensional marker of known shape and size and have a camera kept at the front of the robots sensing the markers to determine distance. The robots use this information to estimate each others positions and to control movement. To test the method experimentally, we used two real robots in an indoor environment. The result of the experiment revealed that the distance measurement and control error could be reduced to less than 3%.