Published papers

Due to the advance in information and communication technologies, smart cities have become an increasingly appealing vision. One indispensable basis in the research, development and implementation of smart cities is urban sensing technology. Automotive sensing is a novel urban sensing technology that equips sensors to vehicles, like buses, taxi cabs or garbage trucks and utilizes their mobility to help to conduct urban sensing tasks. In this paper, we present Cruisers, an automotive sensing platform for smart cities, based on the following ideas: a) Garbage collecting trucks are used to host sensors, b) Cellular communication network is used to deliver sensed data to servers, and c) Proxy server(s) are adopted to convert the format of sensed data to required ones, such as sampling rate, spatial interval or pub/sub protocol. To validate the feasibility of Cruisers, we implement a real system that consists of 66 customized sensing modulars integrating typical environmental and mobility sensors and deploy them into the garbage collecting trucks at Fujisawa, a medium-sized city in Japan. Performance evaluation is conducted to investigate the performance of Cruisers in terms of scalability, data publishing delay and spatial coverage.

Automotive sensing is a novel and appealing sensing technology in which sensors are installed into vehicles to utilize vehicles' mobility to conduct urban sensing in smart cities. The coverage performance is a major metric to characterizing the quality-of-service of sensing systems. Despite of the coverage metrics studied in static sensor networks that consist of only spatial dimension, the lack of a proper metric to characterizing the spatio-temporal coverage of automotive sensing systems is stunting the research, development and commercialization of such mobile sensing systems. To address this issue, we propose, for the first time to the best of our knowledge, a spatio-temporal coverage metric for automotive sensing. The proposed metric characterizes the coverage in both spatial and temporal dimensions in order to provide a guideline for smart cities application developers to evaluate the quality-of-service that can be expected from an automotive sensing system. Evaluation based on an automotive sensing system implemented in Fujisawa City, Japan is conducted to demonstrate the usage of this metric in a realistic scenario.

Human attention has bottlenecked today's ubiquitous computing environment where users are consuming increasing amounts of information from numerous applications and services. Since the system-to-user provision of information is becoming more proactive, mainly via push notifications that often cause interruption at the users’ side, attention management is becoming very important. Despite the many existing studies concerned with detecting opportune moments to present such push information to the users (in a way that preserves the user's attention and lowers their cognitive load and frustration), there is little evaluation of such systems in the real-world production environments. Overlooked areas of study also include the examination of real users and notification contents. In this paper, we present various results from the first extensive evaluation on user's interruptibility and engagement in the real-world environment with a market-leading smartphone application that boasts a large number of users, including real notification content on the application. Following our previous mobile-sensing and machine learning-based interruptibility estimation approach, which was an effective study in its own right (Okoshi et al., 2015 [18,19]), we embedded a logic with the same approach in the “Yahoo! JAPAN” Android app (one of the most popular applications on the national market). The results from our large-scale in-the-wild user study (that included more than 680,000 users and spanned three weeks) indicate that, in most cases, delaying the notification delivery until an interruptible moment is detected is beneficial to users. The practice results in significant reduction of user response time (49.7%) when compared to delivering the notifications immediately. We observed a higher number of notifications opened in our system and constant improvement in user engagement levels throughout the entire study period. We also observed differences in click rates among different days and time among users with different attributes (e.g., age, gender, and occupation). Additional evaluation of our revised system, which can train and distribute different models for weekdays and weekends, improved the click rates during weekends. This negated the performance degradation previously observed during weekends.

The limited attentional resource of users is a bottleneck to delivery of push notifications in today's mobile and ubiquitous computing environments. Adaptive mobile notification scheduling, which detects opportune timings based on mobile sensing and machine learning, has been proposed as a way of alleviating this problem. However, it is still not clear if such adaptive notifications are effective in a large-scale product deployment with real-world situations and configurations, such as users' context changes, personalized content in notifications, and sudden external factors that users commonly experience (such as breaking news). In this paper, we construct a new interruptibility estimation and adaptive notification scheduling with redesigned technical components. From the deploy study of the system to the real product stack of Yahoo! JAPAN Android application and evaluation with 382,518 users for 28 days, we confirmed several significant results, including the maximum 60.7% increase in the users' click rate, 10 times more gain1compared to the previous system, significantly better gain in the personalized notification content, and unexpectedly better performance in a situation with exceptional breaking news notifications. With these results, the proposed system has officially been deployed and enabled to all the users of Yahoo! JAPAN product environment where more than 10 million Android app users are enjoying its benefit.

This paper proposes the session layer communication continuity support for Java applications toward a continuous operation for the users. In a mobile computing environment, mobile hosts move around thedifferent network segments even during applications communicate with the remote endpoint.In such a situation, maintenance of thecommunication continuity between the applications is significant.In order to retain the communication continuity, not only the mobilitysupport but the virtual circuit continuity support is required forapplications.Existing approaches on the network, the transport and the sessionlayers do not provide the complete mobility and virtual circuitcontinuity for applications, although they require the complicatedimplementation.``MobileSocket'' is a user-level enhanced socket library written inJava, and provides the library-based session layer mobility andvirtual circuit continuity support for applications. Two mechanisms, Dynamic Socket Switching (DSS) and Application LayerWindow (ALW) enforce MobileSocket and enable the implementationsimplicity.MobileSocket applications can be used in the Java mobile applications and the agents, as well as in ordinary network applications.In this paper, after we clarify the communication continuity andexisting approaches, we present the MobileSocket design, mechanism, and evaluation results.

In this paper, we propose the Neighbor-state Based Queuing（NBQ）for improving the performance of flows sharing link bandwidth under various transfer protocols. Each router with NBQ　informs the next upstream router of its link status. According to the received status, NBQ dynamically sets the packet discard ratio of the non-adaptive flows. NBQ　reduces the wasted non-adaptive flows and provides available bandwidth for the adaptive flows. We have demonstrated dramatic improvements of adaptive flow's throughputusing our scheme through simulations.

Rate control of continuous media (CM) UDP flows over the Internet should retain TCP-friendliness.Despite many efforts to create TCP-friendly algorithms,it is often difficult to adjust parameters pertaining to the algorithmsin order to achieve exact fairness with TCP flows.In this paper, we propose a scheme called TCP-Rate-Probing-Based Adaptation (TPBA).In TPBA, a CM flow intermittently changes its transport protocol to TCP to measurea TCP-exact rate, and uses the rate with UDP.We have built an experimental system with FreeBSD PCs andshown that TCP-friendly rate control can easily be achievedfor both a shorter and a longer round-trip-time connections.

We propose a mechanism to facilitate the development of component-based mobile applications with adaptive behaviors. The design principles and communication patterns of legacy software systems will greatly change in a forthcoming environment, where a variety of computing devices become embedded in home and office environments, users move around with/without portable computing devices, and all the devices are interconnected through wired/wireless networks. In the proposed mechanism, Improvised Assembly Mechanism (IAM), we realize functionality to compose an application in an ad hoc manner and to achieve the adaptation of applications by adding, replacing, supplementing, and relocating components at system runtime according to various environmental changes such as the locational changes of computing devices and users. The mechanism is implemented as a built-in functionality of the Soul component, which is one of the fundamental elements in the Possession model.

This work explored location-based virtual plug-and-play. It allowed functional manipulation of objects through the run-time for applications (known as Serdget). A mark-up language (VML) described the functional components of virtual networked appliances (VNA). Some issued include dynamic locations, adaptation, wireless mobile devices, and heterogeneous network. Devices were represented with some structure indicating who else were in the same location. The devices themselves were decentralised. The location mapping mechanism provided lookup, registrar, location update, and event notification. The mechanism addressed issues pertaining to its overhead, modularity of search and autonomy. The area manager appears to be hierarchical rather than peers, which imposed total ordering and partial ordering respectively.

The work described a personal corner and desk-top manager. The PDA device stored the keys, passphrases and location information. This follow-me feature was achieved through a secure call-up protocol. The environmental awareness were imported into the application as marshalled environment events. The environmental awareness provided the basis for QoS adaptation. Internal metrics include display size, CPU and memory, and locale information. External metrics include power service, and evaluation service. The call-up would go back to the previous machine to retrieve the standby agents. The Java applications were suspended by flushing their state to the machine (which might compromise the security model). Research issued identified include policy negotiation, QoS adaptation, and resource policy.

This paper proposes Smart Operation of Networked Appliances (SONA) system, a new control system for networked appliances using mobile agents. By adopting mobile agents to the control system, the SONA system can control networked appliances autonomously and asynchronously. This can relieve users from direct and complicated operations of the appliances. In addition, the SONA system facilitates the control of networked appliances with limited system resources. In this paper, we present the design and implementation of SONA system.

This paper presents a new middleware architecture for integrating heterogeneous information appliances on heterogeneous network for various users, called Virtual Network Appliance (VNA) Architecture. Instead of merely connecting appliances seen in existing approaches, VNA architecture accommodates creating a function alliance called a VNA. VNA Markup Language is our solution to define VNAs independent of specific home networks. Our middleware enables users not only to define VNAs by themselves (bottom-up integration), but also to virtually plug and play pre-defined VNAs (top-down integration).

Today, new computing environment called wearable computing is getting popular in research. However, many of these research issues are mainly focused on the user interface or the miniaturization of PC platform. These hardware related researches may achieve some results, however these researches do not present an application and a software organization that are suitable and needed for wearable computing environment.We propose wearable computing environment named `` Wearable Network computing'' which supports cooperation of many devices and appliances around user's body. In {it Wearable Network} computing environment, the application may be distributed into various devices and appliances around user's body and accomplish user's task by using the function of these devices. In this environment the wearable computer controls the distributed application adapting to changes of user's context and to availability of devices.In this paper, we describe the an applicaton framwork for wearable computing environment which may provide context-awareness, device coordination, distributed and migratable application.

Today, new computing environment called wearable computing is getting popular in research. However, many of these research issues are mainly focused on the user interface or the miniaturization of PC platform. These hardware related researches may achieve some results, however these researches do not present an application and a software organization that are suitable and needed for wearable computing environment.We propose wearable computing environment named `` Wearable Network computing'' which supports cooperation of many devices and appliances around user's body. In {it Wearable Network} computing environment, the application may be distributed into various devices and appliances around user's body and accomplish user's task by using the function of these devices. In this environment the wearable computer controls the distributed application adapting to changes of user's context and to availability of devices.In this paper, we describe the an applicaton framwork for wearable computing environment which may provide context-awareness, device coordination, distributed and migratable application.

This paper describes the Smart Space Lab (SSLab) project toward the next generation computing environment, ``{sf Smart Space}.'' As numerous types of networked appliances, such as A/V devices, home appliances, or sensors, are connected to each other via both wired and wireless networks, computational intelligence can be regarded as being distributed and embedded into users' surrounding space, rather than on a specific device such as users' PCs or PDAs. We call such a space with embedded computation ``Smart Space.'' In Smart Space, users can have their computing environment relying on not only computation of their carrying devices, but one in Smart Space. Toward the realization of Smart Space, SSLab Project is now addressing three research issues, (A)physical structure of Smart Space, (B)network architecture with support of dynamism and heterogeneity, and cadaptive middleware architecture and applications.

Today, new computing environment called wearable computing is getting popular in research. However, many of these research issues are mainly focused on the user interface or the miniaturization of PC platform. These hardware related researches may achieve some results, however these researches do not present an application and a software organization that are suitable and needed for wearable computing environment.We propose wearable computing environment named `` Wearable Network computing'' which supports cooperation of many devices and appliances around user's body. In {it Wearable Network} computing environment, the application may be distributed into various devices and appliances around user's body and accomplish user's task by using the function of these devices. In this environment the wearable computer controls the distributed application adapting to changes of user's context and to availability of devices.In this paper, we describe the an applicaton framwork for wearable computing environment which may provide context-awareness, device coordination, distributed and migratable application.

Today, Wearable Computers are popular in research, however, they are dedicated almost for methods of human interface design. We do not expect WC's as a merely super-compact notebook computer or its extension, which includes everything and runs the same OS as desktop PC's do. Meanwhile, short-range radio-networking technology as Bluetooth, is emerging. We envision that a WC plays a role as a control center which conducts and collaborates with the devices or gadgets also worn by a person in response to the environmental changes. All these appliances should be networked in any way, and a person does not wear appliances but rather the network itself. We named it as wearable network, and are constructing the software architecture for this. This article describes the wearable network architecture, from the device layer, which captures and collects raw data of evironmental information around the owner, a database module which consists of the knowledge on the real-world and the owner's intention, to the application layer, which enables the adaptable coordination among the services timely available. We also explain a current state-of-the-art wearable network implementation.