Smart city applications integrate the human, physical, and digital systems in a built environment with Internet of Things (IoT) resources, city models, and domain models. However, existing methods for the integration are suitable for individual applications and lack interoperability among application modules. This study analyzed existing integration strategies and developed an ontology for integrating the data modeling standards of the Open Geospatial Consortium (OGC) CityGML, IndoorGML, and SensorThings API. To cope with the broad definition of “things” in the IoT, the proposed ontology supports multiple views of things, including the a-building-as-a-thing, a-room-as-a-thing, an-opening-as-a-thing, and a-device-as-a-thing views. Thus, the proposed ontology relates information from these three standards and supports semantic queries. We demonstrated the proposed solution in smart home, smart security, smart health care, and fire evacuation systems. Overall, the proposed solution can facilitate the integration of standard-based IoT resources and city models to support smart city applications.

Change detection (CD), enabled by multitemporal multispectral satellite imagery, has many important Earth observation missions such as land cover/use monitoring, for which we observe that change regions are relatively smaller than those caused by disaster (e.g., forest fire) with patterns typically composed of a number of smooth regions. These observations are considered in our new CD criterion, which can effectively mitigate the artifacts and speckle noise suffered by existing statistic-based and difference image (DI) analysis based methods. The proposed CD criterion amounts to a large-scale non-convex optimization, which is first reformulated using the convex relaxation trick with associated change map interpreted in the probability sense, followed by adopting an efficient convex solver known as alternating direction method of multipliers (ADMM). The resulted probabilistic change map would be more practical, and can be thresholded at 0.5 to yield the conventional binary-valued one. We also reveal a link between the proposed criterion and the DI-based criterion, and demonstrate the outstanding performance of our fully unsupervised CD algorithm qualitatively and quantitatively.

Over the past years, 360° video streaming is getting popular. Watching these videos with Head-Mounted Displays (HMDs), also known as Virtual Reality (VR) headsets, gives more immersive experience than using traditional planar monitors. To fulfill a real immersive experience, there are several challenges, such as high bandwidth consumption, latency-sensitive, and heterogeneous HMD devices. In this paper, we propose an edge-assisted 360° video streaming system, which leverages edge servers to render viewports for viewers of 360° videos. We formulate an optimization problem to determine which HMD clients should be served by the edge server. We design an algorithm to solve this problem, and implement a real testbed as a proof-of-concept. The resulting edge-assisted 360° video streaming system is extensively evaluated with a public 360° viewing dataset. Leveraging edge servers, we reduce the bandwidth usage and computational workload on HMD clients. Moreover, lower network latency is achieved. The evaluation results show that compared to current 360° video streaming platforms, our edge-assisted rendering platform: (i) saves up to 62% in bandwidth consumption, (ii) achieves higher viewing quality, (iii) reduces the computation workload for those lightweight HMDs, and (iv) saves the battery life of HMD clients.

We present LOST-Tree, a new spatio-temporal structure to manage sensor data loading and caching in a sensor web browser. In the same way that the World Wide Web needs a web browser to load and display web pages, the World-Wide Sensor Web needs a sensor web browser to access distributed and heterogeneous sensor networks. However, most existing sensor web browsers are just mashups of sensor locations and base maps that do not consider the scalability issues regarding transmitting large amounts of sensor readings over the Internet. While caching is an effective solution for alleviating the latency and bandwidth problems, a method for efficiently loading sensor data1 from sensor web servers is currently missing. Therefore, we present LOST-Tree as a sensor data loading component that also manages the client-side cache on a sensor web browser. By applying LOST-Tree, redundant transmissions are avoided, enabling efficient loading with cached sensor data. We demonstrate that LOST-Tree is lightweight and scalable, in terms of sensor data volume. We implemented LOST-Tree in the GeoCENS sensor web browser for evaluation with a real sensor web dataset.

IEEE-1394 is widely adopted in various commercial products for computing, communication, and entertainment. Although many services with Quality-of-Service (QoS) supports are now available in systems over IEEE-1394, little work is done for QoS-based resource allocation. In this article, we aim at the design of a bandwidth reservation mechanism and its policy for isochronous requests, such as those from cameras. We then address the QoS support issue for asynchronous requests, such as those from disks, and an analytic framework for probability-based QoS guarantees. This work is concluded by the proposing of a topology configuration algorithm for IEEE-1394 devices. The capability of the proposed methodology and the analytic framework are evaluated by a series of experiments over a Linux-based system prototype.

As the universal serial bus (USB) 2.0 becomes a major driving force in the peripherals market now, the variety of USB devices and their request types also impose challenging issues on resource allocation of bus bandwidth. This research aims at the proposing of a USB-compliant system architecture and real-time scheduling algorithms for the resource allocation of USB 2.0 and 1.1 device requests jointly in a quality-of-service (QoS) fashion. Periodic requests, such as isochronous and interrupt transfers, are guaranteed with preservation of bus bandwidth and schedulability tests. Sporadic requests, such as control and bulk transfer, are serviced with probabilistic performance guarantees. The capability of this work is demonstrated with performance evaluations over a Linux system prototype, for which we have encouraging results.