Software defined networking (SDN) is applied for efficient traffic control in aerial wireless mesh networks. In this scenario, each mesh node requires a connection path to the involved SDN controller. To deal with the loss of connection paths due to wireless link failure, we propose and implement the combination of an ad hoc routing protocol with an SDN protocol. Maintaining a connection path to the SDN controller enables the implementation of the consecutive efficient traffic control. Additionally, we propose two routing algorithm control methods that are suitable for aerial wireless mesh networks, and we implement them in an SDN controller. One is a metric algorithm, and the other is a combined optimization algorithm that is intended to minimize the maximum link bandwidth utilization. The combination optimization algorithm prevents communication flows from concentrating on specific links, thereby improving the system throughput of the mesh network. We implemented the proposed system in actual drone equipment and conducted field trial evaluations, demonstrating multihop communication in the air, automatic route switching using the metric algorithm, and route distribution using the combination optimization algorithm, which all could work satisfactorily in a real field.

In an MEC (Multi-access Edge Computing) environment, it is suitable to compose an application as a set of containers for flexibility in resource allocation. This paper proposes stateless shared containers (SS-Containers) that can be shared by multiple applications simultaneously in an MEC environment, similar to a shared library in an operating system. It is expected that SS-Containers reduce resource consumption, shorten application startup time, and efficiently manage special hardware such as GPU. When 16 applications share an SS-Container with an encryption function, and each application contains the container with the same encryption function, the memory consumption is reduced by approximately 190 MiB. Comparing the case in which nine applications share an SS-Container that accesses a GPU to solve large-scale simultaneous linear equations with the case in which nine applications randomly access a GPU via a container inside them, the response time is reduced approximately by 57 % (39 seconds).

In a Multi-access Edge Computing (MEC) environment, an application will be composed of multiple containers running on edge servers, and a container orchestration method determines which containers should be deployed on which edge servers. This paper proposes a container orchestration method considering shared containers. These containers will be introduced in an MEC environment to reduce application resource usage, similar to a shared library in an operating system. The proposed method adopts a multi-stage grouping of edge servers to aggregate computation resource information and network information of the edge servers for efficient orchestration calculation. The formulation of the proposed orchestration method has been successfully completed, marking a significant milestone in this research. Evaluation will be conducted assuming an environment that contains 2,048 edge servers and 200 user terminals.

This paper proposes an architecture called Cont-MEC for enabling UEs (User Equipments) to offload a part of applications to MEC (Multi-access Edge Computing) servers. It is expected that a MEC infrastructure is composed of a small number of centralized data centers and geographically distributed edge stations, in each of which multiple edge servers are installed. It is also expected that applications on UEs are implemented as container clusters similar to cloud-native applications and they are deployed on computing clusters. ContMEC has the following three features: (i) constructing a computing cluster per edge station for scalability to the number of UEs, (ii) hierarchical resource management for scalability and efficient resource sharing among computing clusters, and (iii) overlapped computing clusters for efficient resource sharing. A PoC (Proof-of Concept) implementation of ContMEC employs Kubernetes as a container orchestration system without modifications although Kubernetes does not take account of the MEC infrastructure. The PoC implementation shows that advantage of offloading is larger than disadvantage of implementing applications as container clusters, control traffic is moderate against the number of UEs, and efficient resource sharing among computing clusters is achieved.

A wireless mesh network is constructed with multiple aircrafts equipped with wireless communication devices. A centralized software-defined networking (SDN) controller on the ground is adopted to control traffic routing efficiently and flexibly. In such a wireless SDN mesh environment, each mesh node always requires a connection path to the SDN controller. In preparation for wireless mesh link failure, the ad hoc routing protocol together with the SDN protocol is utilized. However, duplicated control packets of the two protocols increase the overhead and waste valuable wireless bandwidth and processing power. The existing research does not mention the problem; therefore, we focus on the topology information acquisition issue and propose a method named topology information acquisition method using HELLO ACK that can realize the overhead reduction by optimizing the control packets. The theoretical evaluation was conducted to confirm the effect of the proposed method by comparing with the existing methods on the overhead reduction. The proposed method was also implemented into open source SDN and ad hoc routing protocols. Our proposal works well in an actual mesh network environment. In all the evaluations, our proposed method showed an overhead reduction effect of 75%-95%.

Autonomous robots moving indoors require information about their position with high accuracy in order to reach their destination safely and correctly. To realize self-localization for such autonomous robots, we aim to measure the indoor position of a moving object by using signal tracking with spread-spectrum (SS) ultrasonic signals. In this paper we investigate the accuracy of distance measurements using signal tracking of SS ultrasonic signals using Code Division Multiple Access (CDMA). To detect the SS ultrasonic signals, we perform correlation calculations between a range of received waves and a similar range of replica signals identical to the transmitted SS signals. Conventional positioning systems using SS signals employ signal acquisition to calculate the coordinates of objects from correlation values and signal tracking to measure the relative shift of distances of moving objects. After investigating the signal acquisition method, we found that 3-D positioning with an error of 50 mm was possible, even when transmitting simulcast ultrasonic signals with CDMA. Other studies using our proposed signal tracking method for moving targets without CDMA have maintained correlation values using a limited correlation range for correlation calculations, though they have yielded reduced correlation values for unmoving targets. In this paper, we develop a signal tracking method using the simulcasting of multiple signals with CDMA and discuss its effectiveness. We conduct an experiment on distance measurements to determine the method's measurable range and measurement error. We perform ten measurements of distances from 1000 to 6000 mm between a transmitter and a receiver, in 1000 mm intervals, using 50% of the correlation range. The results indicate an average measurement error of 11 mm, which is less than that of conventional signal acquisition methods.

Indoor real-time positioning is required in order to realize self-localization for autonomous mobile robots. In particular, accurate control in plural mobile robots requires 3-D coordinate information. This paper presents the positioning accuracy and response time for a 3-D real-time indoor positioning system which uses continuous spread spectrum ultrasonic signals that are generated and detected using inexpensive all-purpose transducers, and a Code Division Multiple Access (CDMA) communication system. For application with moving targets, we propose signal acquisition and tracking using continuous signals in analogy to the already effective Global Navigation Satellite System (GNSS). The proposed calculation algorithm for coordinate acquisition is based on the Newton-Raphson method for continuous signals. The calculation time and accuracy of this method is verified by conducting a positioning experiment. The results show that the positioning error is less than 50 mm in a 4000 mm by 4000 mm experimental space with 4 transmitters. Moreover, the maximum response time to update a result is 80 ms, displaying the efficacy of this system for robot navigation.